PCB & PCBA | Grande | EMS |Since 1998

https://www.grande-pcba.com/seven-steps-to-ensure-pcba-project-good/  

1. Preliminary preparation stage

> PCBA project specification, technical parameters and requirements; >The lead group for the preparation of the project, responsible for process design, process implementation, project reporting, etc.

2. Design and development

The standard of this stage is to ensure the circuit design ability that is able to meet the SMT production process.

3. Design and editing of work instructions for SMT production process

>Clarify the format of the work instruction, which is consistent with pcba processing factory; > The content of the operation instruction is clear (the operation instruction for solder paste selection, the operation instruction for the use of stencil, the patch processing operation instruction, the reflow welding process control instruction, etc.);

4. Confirmation of stencil production capacity

>The process of making stencil; >The patch processing factory exports Gerber files suitable for stencil production from PCB files to guide the process of stencil production;

5. Confirmation of the programming and operating capabilities of the placement machine

> Evaluation of BOM list and Gerber file; > Placement machine programming, PCB size measurement and board assembly processing;

6. PCBA test

> Test after SMT processing and production ( burning, signal, high and low temperature, ICT test, etc.); > Three-proof paint coating, etc. (three-proof refers to which three-proof, please refer to our previous analysis of the problem);

7. PCBA SMT project improvement and evaluation

>PCBA design mutual inspection; >Report; >Suggestions for improvement.

https://www.grande-pcba.com/the-difference-between-2-layer-board-4-layer-board-in-smt-assembly/The basis of SMT Assembly is PCB, that is, Printed Circuit Board, which are distinguished by the number of layers, such as double-sided boards and four-layer boards. At present, up to 48 layers can be achieved. Speaking from a technical point of view, the number of layers has unlimited possibilities in the future. Some supercomputers have nearly a hundred layers. However, the most common number of layers in medical electronic PCBA or automotive electronic PCBA is usually 2 or 4 layers. If you want to know how to choose the number of layers of the PCB reasonably, please read the following introduction about the difference between the 2 Layer board and 4 layer board in SMT Assembly before making a decision!

2 Layer Board Compared with the four-layer board, the double-sided board is easier to use due to its simple design. Although not as simple as single-sided panels, they are as simple as possible without sacrificing double-sided input capabilities. The reduced complexity leads to the same reduced price tag, but this means that there are fewer possibilities compared to a four-layer board. However, as the most commonly used circuit board in the industry, its significant advantage is that there is no signal propagation delay.

4 Layer Board Four-layer boards have a larger surface area than double-sided boards, increasing the possibility of more layout. Therefore, they are terribly suitable for more complex equipment. Due to their complexity, production cost will be higher and development will be slower. They are also more likely to have propagation delay or mutual influence, so reasonable design is very important.

What’s the purpose of layers?

The most important layer in the PCB that is the copper foil signal layer, which is the name of the PCB. Although the double-sided board has two signal layers, while 4-layer PCB has four. These signal layers are used to connect to other electronic components in the device. Between these layers is an insulating layer or core, which is added between the signal layers to give its structure. In the four-layer board, there is also a solder mask layer, which is applied on top of the signal layer. This prevents copper traces from interfering with other metal components on the PCB. They also have a silk screen layer to add numbers to different components to make them easier to lay out.

If you are looking for  Turnkey PCBA Service / EMS Company, then Grande is your best choice. We provide One- Stop Service like PCB Fabrication, Components Procurement, PCBA Manufacturing, Function Test, even Final Box Assembly, etc.

PCB Assembly belongs to precision processing. Incorrect operation will cause cracking, fracture, open circuit and bending fracture of components and connectors, which will eventually lead to the damage of components and PCBA. To avoid these situations, the following rules must be followed during PCB Assembly:

1. Keep the work environment clean The working environment consists of two parts, one is the workshop area and the other is the workbench, which must be clean and tidy, without any food, beverages and other items, nor can ashtrays, cigarettes and other items be placed, and smoking is prohibited.

2. Reduce PCB Assembly steps The assembly steps of PCB are not that complicated. Instead, PCBA manufacturers emphasize that less is better. It is best to minimize PCBA steps to reduce risk. At the same time, when operating, you must cooperate with gloves, do not disturb, and use it directly, which can easily hurt your hands and cause injury. In addition, gloves should be changed frequently so as not to interfere with operation.

3. Do not operate with bare hands Grease in the hand can reduce the solderability of components. Therefore, direct manipulation with bare hands or fingers is not allowed, thereby reducing solderability.

4. Do not use hand creams or silicon-based cleansers Both of these conditions result in reduced solderability and non-adherence of the coating, so do not use, this is a basic guideline for shop operations and should be followed by any employee.

5. PCBA cannot be superimposed During the operation, some novices may stack the PCBA boards together because of unskilled operation, which can easily damage the PCBA boards, so it is strictly forbidden to use them. The correct way is to put it in a specially configured dedicated bay.

6. The type of sensitive components should choose the appropriate mark In PCBA components, there are some sensitive components, such as EOS/ESD and so on. These components are very sensitive and appropriate markings must be selected. In addition, static electricity should be controlled during operation.

The above six points are the rules that must be followed in the PCB Assembly process. They may seem like a hassle, but in reality, they are an essential requirement to ensure a smooth PCB Assembly workflow.

In order to facilitate the assembly of the printed circuit board (PCBA), fiducial mark will be designed on the PCB board. Do you konw? The requirements and specifications of fiducial mark In PCB Design?

What Is PCB Fiducial Mark?

Circuit board fiducial mark refers to determining the specific position of the PCB via in the PCB design process, which is a super important link in the PCB design process. After all, the function of the fiducial mark is the processing benchmark when the printed circuit board is maufactuered. There are various positioning methods for PCB fiducial mark, mainly in the light of different positioning accuracy requirements. The fiducial mark on the printed circuit board should be represented by special graphic symbols. When the requirements are not high, larger mounting holes in the printed circuit board can also be used instead.

In order to facilitate the fixing of the board during drilling and milling of the printed circuit board, as well as to facilitate online testing, plenty of circuit board manufacturers want users to design three non-metallized holes on the PCB. And the fiducial mark is usually designed as non-metallized holes, and the drilling diameter unit is basically mm. If the board surface is tight, at least two fiducial marks should be placed and placed diagonally. If you want to produce panel board, you can also regard the whole panel board as a PCB, and the entire panel board only need fiducial marks. If the user does not place it, the circuit board manufacturer will automatically add it without affecting the circuit, or use the existing non-metallized holes in the board as fiducial marks.

Positioning Fiducial Mark Method

Device hole interface devices and connectors are mostly plug-in components. The diameter of the through hole of the plug-in device is 8 to 20 mil larger than the diameter of the pin, and the tin penetration is good when soldering. It should be noted that there is an error in the aperture of the circuit board factory. The approximate error is ±0.05mm. Every 0.05mm is a drill. The diameter is more than 3.20mm, and every 0.1mm is a drill. Therefore, when designing the aperture of the device, the unit should be converted into millimeters, and the aperture should be designed to be an integer multiple of 0.05. The plate manufacturer sets the size of the drilling tool according to the drilling data provided by the user. The size of the drilling tool is usually 0.1-0.15mm larger than the forming hole required by the user. Less is better. If it is a crimping device, the aperture should not be enlarged, it should be designed according to the recommendations of the data, and which are the crimping devices should be explained in the board making instructions, so that the circuit board manufacturer can try to control the error during the board making process and avoid some unnecessary trouble.

PCB Design Fiducial Mark Requirements & Specifications

Drilling types are divided into metallized holes and non-metallized holes. There is copper sinking in the hole wall of the metallized hole, which can play a conductive role and is represented by PTH. There is no copper sinking in the hole wall of the non-metallized hole, which can not play a conductive role, which is represented by NPTH. The difference between the outer diameter and the inner diameter of the metallized hole diameter should be greater than 20mil, otherwise the soldering ring of the pad is too small to be processed, and it is not conducive to soldering. If conditions permit, the aperture can be designed to be the radius of the pad. The maximum drilling diameter of metallized holes is 6.35mm, and the maximum drilling diameter of non-metallized holes is 6.5mm. The metallized hole should not be designed on the outline, and the edge of the hole should generally be greater than 1mm from the outline. Heavy holes while drilling are easily able to damage the drill bit, so it should be avoided as much as possible. Holes that do not require soldering and have no electrical characteristics can be designed as non-metallized holes. Non-metallized holes do not need to be designed with pads. The edge of the hole is at least 1mmo away from the circuit or copper foil. Drilling can be divided into circular holes and rectangular holes according to the shape. Most of the drilled holes are round holes, and rectangular holes are drilled multiple times by the drill bit according to the prescribed procedure. Therefore, it is best to design the rectangular hole to be twice as long as the width, and the width is not less than 0.8mm, and the rectangular hole should be designed as little as possible.

PCB Fiducial Mark Requirements

The development of the PCB design industry has become mature, so the requirements for PCB fiducial marks are also rather perfect. The fiducial mark requirements are as follows:

1. At least two fiducial marks must be set on the diagonal of the board. 2. The standard diameter of the fiducial mark is 3.2mm_+0.05mm. 3. The following preferred apertures can also be used for the veneer of different products of the enterprise: 2.8mm±0.05mm, 3.0mm±0.5mm, 3.5mm±0.5mm and 4.5mm±05mm. For different boards of the same product (such as the DT board and PP board of ZXJ10), if the external dimensions of the PCB are the same, the positions of the positioning holes must also be unified. 4. The fiducial mark is a light hole, that is, a non-metallized through hole (except for the RF board). 5. If the existing installation holes (except the buckle installation holes) meet the above requirements, there is no need to set additional fiducial marks.

Some Common Specifications & Accuracy Requirements For Fiducial Marks

1. The diameter error range of the fiducial mark is generally within 0.01mm. If the PCB manufacturing room has a large error, it will cause poor contact of the probe and inaccurate alignment of the interface connector automatic mechanism. 2. Requirements for the diameter of the fiducial mark: Try to be below 3mm, so that the positioning column will not be deformed, and it is not easy to operate if it is too large. 3. The distance between the fiducial mark and the PCB network: More than 1MM, so that the installation operation is not easy to short-circuit, and it will not cause damage to the product line. 4. Type of fiducial mark: The fiducial mark is generally a mechanical control that requires no copper sinking, so that it is not connected to the circuit on the board and has higher precision. 5. The layout of the fiducial mark: It need to be on the four corners or diagonal lines of the PCBA, so as to form a multi-point surface positioning, the positioning is accurate, and the farther the distance, the better. 6. The distance between the fiducial mark and the test point should be at least 2mm to prevent false short circuit during the test. 7. The distance between the fiducial mark and the edge of the board is at least 2mm, which is not easy to break while ensuring the strength of the PCBA.

https://www.grande-pcba.com/what-is-fpc-circuit-board/It’s well known that Printed Circuit board (PCB) plays an important role in the electronics industry. This is because PCB is widely used to perform various roles in devices such as computers, televisions, and power systems. A printed circuit board consists of conductive tracks that interconnect components on the board. They include potentiometers, resistors, capacitors, and switches with various voltage or current levels. They are also commonly used for electrical safety testing or verification.

According to JIS C5017, the Japanese Industrial Standard for measuring the mechanical properties of printed circuit boards, a flexible printed circuit board (FPC) is a PCB with a cylindrical or rectangular shape that can vary in size based on the requirements of its application. The standard divides FPCs into two categories: Rigid and Flexible PCB. Rigid FPCs help mechanically connect components, but cannot bend. A flexible FPC is a double-sided PCB that can withstand bending forces. Also, we mainly use it for electrical interconnection applications.

FPCs are popular with engineers because they are easy to modify and customize without any solder joints. The flexibility of the FPC allows for different retrofit solutions. It significantly reduces the cost of manufacturing new boards for specific applications. For example, it is easier to add functionality to the surface of an existing board than to create an entirely new board from scratch.

Composition of FPC  Materials

The composition of an FPC material depends on its intended application and end use. The flexibility of FPC depends on the material’s ability to resist cracking, warping and mechanical damage while maintaining high electrical conductivity. Therefore, manufacturers tend to use fiberglass or FR-4 materials for FPC flexible printed circuit boards. It consists of a mixture of epoxy resin and fiberglass. FR-4 is a rigid board that combines thermal and electrical properties.

1. Insulating film It is a layer of high-density polyethylene made by extruding the resin through a nozzle and coating it on the substrate. HDPE films eliminate capacitive coupling between substrates. It also eliminates other circuits to electrically shield the interconnects on top of the board. The HDPE layer also acts as a vapor barrier to prevent moisture from entering the circuit during curing.

2. Electrostatic adhesive layer After the HDPE film is applied, the adhesive layer can connect the components. These components may include potentiometers and LEDs on the circuit board to improve performance or reduce cost. The adhesive layer is acrylic or polyimide, allowing the LED to be directly bonded to the FPC, saving material and assembly time.

3. Conductor Then we add a conductive layer on top of the adhesive layer. This layer can be polyimide or epoxy or the printed circuit board itself. To avoid warping, we can apply the conductor to a solution at 100 °C.

4.Stiffener Finally, we added a second adhesive layer to the conductors to further reduce bending or cracking issues. We usually use cellulose or acrylic for this layer.

To make an FPC board, components are first pre-assembled onto the board and then cut to size. The FPC material is then put into the mold to bend without breaking. Typically, we heat the FPC material to 120 °C for about 1 hour. This is done to obtain the necessary stiffness so that the material is able to resist the flexors and flex easily. The component is then added to the mold and pressurized to embed it in the FPC.

Next, we apply a layer of conductive ink on top of the component. It helps create a smooth surface that prevents electrical resistance and improves performance.

5. Overlay The cover layer is a top plate made of polyimide or acrylic. The overlay protects the underside of the FPC material. It also acts as an insulation, preventing moisture from entering the FPC material. The overlay is also high temperature resistant, allowing us to use it in ovens and heaters.

Why do you need to use an FPC circuit board?

We use FPCs in applications that require flexibility and conductivity. But we don’t use it when we need mechanical strength. Since FPCs are thin and light, we use them in portable devices such as cell phones, digital cameras, and walkie-talkies. We can use them in large devices like peripherals and power supplies.

1. Reduce weight and space Since FPCs don’t have terminals for electrical connectors, we can use them in devices that need to be lightweight but have outputs that connect many components. For example, a portable GPS device can use an FPC to connect a small battery to the host. The main unit has an internal rechargeable battery. However, the GPS receiver also requires power and some other functions, such as the display and buttons. FPC provides all these components and connects them.

2. Easy customization FPCs are flexible and we can cut them to the required size. Since they are not soldered, they can be easily removed from the board and modified for new uses. You can create entirely new electronics by adding FPCs with add-ons on boards already used for other purposes. For example, we can add an FPC to connect an external battery to an existing product. They include a car radio that adds functionality without completely replacing it.

3. Meet dynamic bending requirements We mainly use FPCs on portable devices because of their flexibility and light weight. They can be adapted to flexible products such as cell phones, or they can be cut to the size needed for new circuit boards. These properties make them ideal for use in consumer electronics.

4. Bend for easy installation and maintenance We use FPCs in solar panels, satellites, generators and electric vehicles in homes and buildings. One can easily install solar panels in places where roofing cannot be built or where landscaping is difficult. The flexibility of these FPCs means they can be adapted to many different environments while still providing electrical pathways between various components. We also use FPCs in electric vehicles. This is because they have a lightweight construction while maintaining the required strength to ensure they do not break when driven.

5. Impedance Control Manufacturers use high-quality materials to make FPCs with high electrical conductivity. Therefore, we also use them in consumer electronics where impedance control is required. The main advantage of using FPC instead of soldered connections is that we can easily control the impedance, which is necessary for mobile devices such as cell phones.

6. Scalability We need to expand some electronics later, like solar panels or electric cars. This is due to technological advancements or improved user needs. These products can use FPC to connect to various other components that we can add later when new functionality is needed.

7. Improve reliability and repeatability When we use FPC in solar panels, we weigh the FPC and mechanically test it to be stable after installation. This process ensures that the product operates reliably and smoothly in many different environments.

8. Thermal Management We can design products that use FPCs with good thermal management. Since we can’t solder the FPC to the motherboard, we can move it and replace it with another one to change its thermal performance. This process ensures that the product is always performing well.

9. Improve aesthetics We can design the FPC very thin to reduce the size of the final product and make it look very nice. One can achieve this by printing components on film rather than inside the FPC. The manufacturer prints the components on top of the FPC. It still seems to be connected to it while retaining its function and appearance.

10. Eliminate connectors FPCs do not require connectors as they can be easily removed and reconnected to other boards. With no connectors and terminals, you don’t need to disassemble the product every time you access the cable. You can then reconnect the FPC later, reducing production costs and ensuring products look clean.

11. Reduce assembly costs In many cases, FPC can reduce assembly costs. For example, semiconductor companies need to add new components to their production lines. We can use FPC with other components to create circuit boards. This increases the functionality of the product while reducing production costs.

12. Increase scalability FPCs can connect many components to the central board to create larger devices. Because of their flexibility and light weight, we can assemble these boards into large products with high performance features.

13. Provide uniform electrical characteristics for high-speed circuits Because the company manufactures FPCs using the same high-quality materials and technologies as optical fibers, they provide reliable electrical characteristics for high-speed circuits. Therefore, these circuits can operate at very high speeds without becoming unstable.

14. Improve Signal Integrity We can design FPCs to improve signal integrity by reducing noise and reflections. They also enhance transmission performance and immunity to electromagnetic interference (EMI).

Flex PCB

The text above shows that FPC is ideal for a variety of applications. Also, we can replace traditional circuit boards. The polyester (PET) and polyimide (PEEK) materials used in FPC are conductive. Therefore, they can be connected to other circuits and components. They also provide mechanical protection for stronger products. The 1-ounce thick Type-V-PET substrate used in FPC is flexible and can carry a lot of current. At the same time it can also withstand high temperature changes. This makes it ideal for high power applications such as solar panels.

level one We form a “graphic overlay” at this stage. The surface is first cleaned, the screen printed, and then cured to ensure a high-quality printing process with repeatable characteristics. Tier 1 is where most of the modification takes place. We print silkscreen or other overlay patterns. We usually do this in CMYK format, using a high-quality inkjet printer to ensure the sharpest possible image.

Tier 2 The lamination stage includes adding electrical traces. This layer is a conductive adhesive that is laminated with the first layer to form the final FPC product. Adhesives must provide a smooth surface for electrical and mechanical stability. We can do this with vacuum or pressure lamination, depending on how rigid or flexible the final product is.

Tier 3 This is an essential layer as it provides a strong mechanical bond between the first and second layers. One of the most popular binder options is a thin ceramic binder that provides excellent mechanical properties. We can apply this using manual or automated systems to ensure consistent production quality at every location.

Tier 4 The last layer determines the physical look and feel of the FPC. The thickness of this layer can vary depending on various factors. They include material type, application requirements and production location.

We use flexible printed circuits (FPCs) in many different applications, such as solar panels, electric vehicles, and airplanes. Additionally, we use them in new applications such as aerial drones and wearable electronics. Therefore, FPCs must provide reliable electrical characteristics for high-speed circuits. FPC manufacturers use more than 20 different chip types and a wide range of specialized components to create end products.

The difference between PET and FPC

PET is our most commonly used polymer in FPC. PET has low thermal expansion, and it’s also transparent, which means we can use it for solar panels or display panels. On the other hand, FPC can be used flexibly for high-performance displays or indoor use.

A flexible printed circuit board (FPC) is a low-cost flexible circuit board that saves significant shipping space. When we apply PCBs with many components, their size becomes larger. The fabrication and construction of FPCs is made easy due to the flexible key features.

Flexible Printed Circuit Cards (FPCs) combine integrated circuits (ICs) and thin-film printed circuit traces. We use them to make flexible circuit boards. A flexible printed circuit card is an electronic device used to house an integrated circuit (IC).

Flexible Printed Circuits (FPCs) are thin plastic sheets that we can use in applications. Some examples include new applications such as solar panels, electric vehicles, aircraft and aerial drones. We manufacture FPCs from conductive, flexible plastics. A plastic top layer that is etched and printed with various circuits and components. This helps create circuits that are thin enough to be flexible and durable.

Flexible Printed Circuit Cards (FPCs) are helpful in many different applications. They include solar panels, electric cars and airplanes. We also use them in new applications like aerial drones and wearable electronics. Therefore, FPCs must provide reliable electrical characteristics for high-speed circuits.

Trace width advantage One of the great advantages of FPC technology is maintaining high line widths, thereby increasing performance. This performance improvement is significant for wireless applications. There is a significant difference between the time it takes for a radio signal to travel from one point on a circuit board to another and the time it takes for the signal to be disturbed by noise and interference. Higher line widths can enable greater signal integrity by reducing these delays while increasing data rates and transmission range.

Another benefit of FPC technology is the low dielectric constant (low εr). PET allows for smaller trace widths and higher performance than other materials such as FR-4. Using low εr in FPC traces also reduces line width variation, which improves signal integrity.

Electrical Characteristics FPC offers several electrical advantages, mainly due to the use of PET. As mentioned earlier, PET is a low-dielectric material, so FPCs using PET can achieve lower line width variations. Reducing linewidth variation improves noise immunity and signal integrity.

FPCs also allow for easy routing, increasing manufacturing yields. Low temperature co-fired ceramics (LTCC) and silica also aid in the FPC process. It provides enhanced thermal performance to the circuit.

The most common FPC manufacturing method is transfer printing. That’s because it involves transferring e-ink onto a surface. Parts of the surface are then etched away to create the circuit. Transfer printing allows very high-speed processing capabilities. We may need circuits that support wireless communication such as WiFi.

manufacturing process FPC manufacturing is a complex process involving the use of many different materials and processes. We can make FPCs by transferring inks onto flexible substrates. This creates the circuit and removes portions of the substrate to expose the circuit. We then transfer the ink using an ultra-sensitive printer that applies 500-800 g/cm² of pressure.

Inks used in FPC manufacturing include a mixture of photoinitiators and photoresists. This allows high speed propagation. We can print the desired area of ​​the circuit first. We then deposit a thin layer on top of the printed area as an etch mask. The exposed areas are then etched away using oxygen plasma to create the desired circuitry.

The final step in the FPC manufacturing process is to cut the circuit into the proper shape. The circuit must be thin enough to accommodate any movement and thick enough to remain durable and functional. The thickness of FPC is usually between 0.031mm and 0.065mm. However, it can also be as thin as 0.01mm or even thinner for special applications such as wearable electronics.

Applications of Flexible Printed Circuit Boards

FPC has many applications in many different fields. We use FPCs in solar cells, cell phones, vehicles and airplanes. Many of these applications require thin and durable flexible sheets. Therefore, they can withstand bending, folding or rolling.

1. Hybrid Electronics These are an electronic product that has both organic and inorganic components. Hybrid electronics are useful clothing or building materials with embedded electronics.

2. Wearable Electronics Wearable electronics include everything from fitness trackers to glasses and other products we wear on our bodies. We have been using FPC for wearable electronics. This is because of their extremely thin, flexible and transparent properties. This makes them great for integrating clothing and other clothing items.

3. Wireless Communication We have been using FPCs in many different types of wireless communications. They are good because they offer very high speed and low power consumption. They are essential for portable devices such as cell phones, laptops, tablets, smartphones, etc. Many of these products require flexible boards that can be bent without damaging the circuit. Flexible FPC makes these products ultra-thin and durable. They also offer a range of advantages, such as ease of wiring and simplified design.

4. Connector We use FPC in all our connectors, including low temperature, high temperature and ultra high temperature versions. FPC connectors are also essential for high-speed cables. They include fiber optic cables and micro RF coaxial cables (eg CAT6).

5. Connectors and Housings FPCs are essential in the connector and housing industry for their versatility and ease of use. Many companies use FPCs to connect many products, including cell phones and other portable devices. Others also use FPCs to house components like LEDs and capacitors.

6. Printed circuit boards FPCs are essential in printed circuit boards (PCBs). They also work best in circuit sheets printed on flexible substrates, usually made of PET or laminated silica. FPCs are ideal for PCBs because they can withstand high temperatures. They can also be easily integrated into circuit boards and offer excellent flexibility.

7. Portable Equipment FPCs are suitable for the portable device market due to their thinness and durability. One of the fundamental properties of FPCs for this market is that we can fold, roll or bend them without damaging them.

8. Solar FPCs are ideal for solar power generation because of their flexibility, thinness and eco-friendly properties. We use them in electronics that convert light into energy. They include solar cells, photoelectrochemical cells, and the like. Flexible, thin and durable, these cells provide high efficiency for solar energy.

What is the cost of FPC? Most manufacturers and sellers determine FPC pricing based on application type, components, and quantity. For example, a small FPC order for a mobile phone used as a business card, we can price it separately. On the other hand, if we use FPCs in solar cells or aircraft control systems, we can price a larger order with more components into one order. FPC pricing is also affected by product or component type. For example, flexible FPC circuit boards are essential in smaller orders than rigid FPC. This is because they are less expensive to set up and have fewer orders.

F-LGA and L-CUP are two common types of flexible printed circuit boards that are ideal for a variety of applications.

F-LGA is a connector commonly referred to as a micro connector due to its small size. This connector has a unique design to suit the application. They require reliable, low-cost and lightweight connections. F-LGA is a flexible PCB used for high frequency connections in cell phones, pagers, cellular phones, cameras, etc.

The L-CUP is a connector with an LC interface designed for signal transmission between fiber optic cables used in network equipment such as routers, hubs, and switches. The connector has high transmission rates and excellent repeatability. L-CUP is a flexible PCB used in photovoltaic solar cells, medical devices and aerospace equipment.

Conclusion FPC is a flexible component used in a wide range of applications. Due to the versatility of FPCs, we can use them in many different applications that require high durability and low cost embedded components. This flexibility and capability makes FPC circuits ideal components for many projects, including solar cells and cell phones.

As we all know, the PCBA manufacturing process is a quite complex process. The entire PCBA process seems to be only one word different from PCB. However, as a matter of fact, it varies a lot, that is PCBA has a series of back-end processes based on PCB, such as solder paste printing, SPI (Solder Paste Inspection), SMT Assembly, reflow soldering, DIP soldering, wave soldering/selective wave soldering, PCBA first article inspection, etc. These PCBA process is that the PCB does not come with it.

Just because all subsequent processes are based on the PCB board, the quality of the PCB determines the quality of the entire PCBA. So which aspects of the PCB have an impact on the PCBA?

1. Dirty Board

Dirty board surface is mainly caused by high flux solid content, too large coating amount, too high or too low preheating temperature, too dirty PCB gripper of conveyor belt, too much oxide and tin dross in tin bath, etc.

The main solution is to choose the appropriate flux; control the amount of flux coating; control the preheating temperature; Check the cleaning effect of the automatic cleaning PCB gripper and take measures; clean the oxide and tin slag on the surface of the tin bath in time.

2. White Residue

The white residue on the PCB is often referred to as white frost. Although it does not affect the surface insulation resistance, the customer does not accept it.

Solution: First of all, we can try to use flux and then use solvent to clean; If it cannot be cleaned, it may be due to the aging of the flux, or it may be exposed to the air to absorb water vapor, or it may be due to the high moisture content in the cleaning agent (solvent), or the The flux does not match the cleaning agent, please ask the supplier to help solve or replace the flux cleaning agent.

3. PCB Deformation

PCB deformation is mainly caused by excessive PCB quality or uneven component layout.

When designing the PCB, try to distribute the components as evenly as possible. Design a support strip in the middle of the large-size PCB (the design width of the non-layout component area is 2~3mm); Or use a mass balance tool to press the sparse components on the PCB during the soldering process to achieve mass balance.

Grande PCB Manufacturing Pros

1)Energy production 2 to 14 layers, 14-22 layers can be produced by prototype 2)Minimum line width/spacing: 3mil/3mil BGA spacing: 0.20MM

3)Minimum aperture of finished product: 0.1mm Size: 610mmX1200mm 4)Solder Mask: Japan Tamura, Taiyo, Futoken;

5)FR4: Shengyi, Kingboard, Haigang, Hongren, Guoji, Hazens, South Asia, (Shengyi S1130/S1141/S1170), Tg130℃/ Tg170℃ Tg180℃ and other high TG plates)

6)High frequency board: Rogers (Rogers), Taconic, ARLLON; 7)Surface technology: spray tin, lead-free spray tin, immersion gold, full board gold plating, plug gold plating, full board thick gold, chemical immersion tin (silver), anti-     oxidation (OSP) blue glue, carbon oil.

Grande has its own SMT factory, which can provide SMT Assembly services for the smallest package 0201 components, and supports various Assembly forms like based on sample Assembly and PCBA OEM. Now let’s talk about the stencil manufacturing requirements in SMT Assembly.

1. Dimensions & Frame of The Stencil

Before PCBA SMT Assembly, custom designed stencils are required to make the SMT Assembly Printing more perfect and suitable. The most important thing about the stencil that is the size and frame. As you probably know, the stencil adopts the stretching method of AB glue and nylon mesh, and a layer of protective paint (S224) must be scraped evenly on the seam between the aluminum frame and the glue. Furthermore, in order to ensure that the stencil has enough tension (specified more than 35N/cm, generally 30~50N/cm) and good flatness, the distance between the stencil and the inside of the frame is required to be no less than 25mm, preferably within the range of 50-100mm . As shown in Figure 1.

Since the stencil to the inner side of the frame, the bonding area between the stencil and the nylon mesh, and the bonding area and the printing area need a certain distance, the inner size of the frame is not the maximum size available for the stencil, and the most useful maximum printing size is the inner side of the frame. size. Go to 220mm or larger size. Of course, this also depends on the width of the press rails, the size of the wiper mechanism and the size of the frame. For instance, the DEK265 press has a frame size of 29″x29″ and a maximum printing area of ​​510mmx489mm.

2. Tension

Stencil tension refers to the tension of the nylon applied to the stencil, which can be measured with a tensiometer. The principle is to test the thrust required for the part of the stencil to sink per unit distance, in N/cm, as shown in Figure 2.

In order to ensure the flatness of the stencil, sufficient tension is required, generally greater than 35N/CM, usually in the range of 30-50N/cm.

3. The Shape & Roughness of The Stencil Hole Wall

Ideally, the opening portion of the stencil should be inverted tapered; For example, the dimension below the opening is about 0.01mm wider than the dimension above (depending on the thickness of the stencil). As shown in Figure 3:

In the above cases, the stencil openings should be ground: QFP, SOJ, PLCC, SOP, socket, and CSP devices with 0.5mm pitch and below, all printed stencils.

4. Dimensional Tolerance

At present, the processing accuracy of electro-polished stencil of major domestic stencil manufacturers is as follows.

1. Opening dimensional accuracy: 0-0.010mm. 2. Opening position accuracy: 0.005～0.03mm. 3. The outside opening accuracy of the screen frame: within 2mm. 4. Material thickness: 0.030～0.600mm. 5. The centering accuracy of the graphics in the frame: within 1mm. 6. Material thickness accuracy: within 0.003. 7. Roughness of side wall (hole wall): 0.005～0.006mm.

https://www.grande-pcba.com/pcb-price-analysis/PCB is an important electronic component and a carrier for the electrical interconnection of electronic components. So many people are curious how the price of PCB is calculated. Now, let’s analyze the factors that affect the price of PCB together!

Factors Affecting PCB Price:

1. Material of the PCB circuit board Take an ordinary double-sided circuit board as an example. Board materials typically include FR-4, CEM-3, with thicknesses from 0.6mm to 3.0mm, and copper thicknesses from 0.5 oz to 3 oz. Solder mask (ink), there is a certain price difference between ordinary thermosetting ink and photosensitive green ink.

2. Production process used for printed circuit boards Different production processes lead to different costs. For example, gold-plated circuit boards and tin-sprayed gongs (milling) and (stamping), and using printed circuits and dry film circuits have different costs.

3. The difficulty of PCB circuit boards Even if the materials are the same, the process is the same, and the difficulty of the PCB itself will still result in different costs. If there are 1000 small holes on both boards, one board has holes larger than 0.6mm in diameter and the other board has holes smaller than 0.6mm, this will result in different drilling costs. For instance, two types of circuit boards are the same, however, the line width and line spacing are different, one type is larger than 0.2 mm, and one type is smaller than 0.2 mm, it will also lead to different production costs because of difficult board scrap rates higher, the cost will inevitably increase.

4. Different customer needs also lead to different prices The level of customer demand will directly affect the output of the factory, such as, a factory requires a 98% pass rate for class1 according to IPC-A-600E, but may only have a 90% pass rate according to class3 requirements.

5. Different PCB circuit board manufacturers Even if the same product is made by different manufacturers with different process equipment and technical level, the result is different cost. Today, many manufacturers produce gold-plated plates because of the simple process and low cost. However, when some manufacturers produce gold-plated boards, the resulting cost will increase when they are scrapped. So they prefer to produce tin-sprayed boards, because tin-sprayed boards lower than gold-plated boards.

6. Different payment methods At present, PCB board manufacturers usually adjust the PCB price according to different payment methods, ranging from 5% to 10%.

7. Different regions Currently, geographically in China, prices increase from south to north, and there are some differences in prices in different regions.

Grande PCB manufacturing advantages

1.Mass Production: 2 to 14 layers                                                  

  Sample Production:14 to 22 layers;

2.Minimum Line Width/Spacing: 3mil/3mil                               

  BGA spacing: 0.20MM

3.Minimum aperture of finished product: 0.1mm                   

   Size: 610mmX1200mm

4.Solder Mask (Ink): Japan Tamura, Taiyo, Futoken;

5.FR4 Brand: Shengyi, Kingboard, Haigang, Hongren, Guoji, Hazens, South Asia, (Shengyi S1130/S1141/S1170), Tg130℃/ Tg170℃ Tg180℃ and other high TG plates)

6.High Frequency Board: Rogers (Rogers), Taconic, ARLLON;

7.Surface Finish Technology: Spray tin, lead-free spray tin, immersion gold, full board gold plating, plug gold plating, full board thick gold, chemical immersion tin (silver), anti-oxidation (OSP) blue glue, carbon oil

Grande is a professional PCB manufacturer with more than 20 years of professional experience, and its board manufacturing capabilities cover rigid circuit boards, FPC, Rigid-flex PCB, etc. If you have any printed circuit board processing needs, welcome to contact us.

After the SMT Assembly is completed, the packaging needs to be inspected to ensure that the PCBA products delivered to the customer are working properly and reliably. So what are the Precautions for packaging inspection after SMT Assembly?

1. The SMT factory assembles the finished product after SMT Assembly and delivers the boards. After the PCBA manufacturer passes the inspection, it should sort out the inspection and test data and materials, issue a certificate of conformity, and prepare the test coupon and packaging material for testing. Delivery shall include accepted printed board, certificate of conformity, necessary (or contractually specified) test data and attached breadboard (for multi-layer boards for Class 3 products, at least circuit continuity test data, plating Photo of the metallographic microsection of the hole).

2. Attaching the test board can add the appropriate test pattern to the outside of the border of the required printed board (near the outside of the edge) as part of the board (panel), processed at the same time as the required printed board, and finished by the final smt processing The shape is separated to represent the finished circuit board for some destructive tests such as withstand voltage, thermal stress, simulated rework, micro-sectioning, etc. The attached test board should generally be marked with the batch number; when the circuit board is assembled by SMT in the form of a puzzle, the attached test board should be marked with the printed board, so that the coupon can be traced back to the specific board. For Class 3 printed boards, there must be an attached test board. For Class 1 and 2 printed boards, whether to attach a test board should be determined by the user or stipulated in the contract.

3. Packaging, Storage and Shipping

(1) Packaging SMT packaging is to ensure that qualified printed board products can withstand transportation and storage environments, and will not be damaged and degraded before use. Qualified PCB boards are cleaned, dried and dehumidified according to regulations, cooled to room temperature and packaged, then packed in polyethylene plastic bags or laminated plastic bags composed of polyethylene/polyamide and polyester/polyethylene, vacuum sealed and packaged , Neutral wrapping paper should be lined between the multi-packed multi-layer boards. Usually laminated plastic vacuum packaging. If the storage environment is harsh and the time is long, when the specified storage conditions are exceeded, the supplier and the buyer will agree to use a plastic-aluminum foil laminated bag made of aluminum foil and polyethylene or polyester film for vacuum packaging. When long-distance transportation is required, the packaged multi-layer boards should be put into the packing box, the outer box should be sealed, the inner box should be lined with moisture-proof paper, and put in a desiccant. Each batch of qualified products should be accompanied by a product qualification certificate. If it is packed in boxes (or other packaging forms), it should be accompanied by a certificate including product name, finished product model, specification, batch, quantity, production date, packaging date, production unit, etc. Packing List.

(2) During storage and transportation, it should be protected from moisture and prolonged exposure to the sun, and should be protected from contact with strong alkali, strong acid gas and mechanical damage. The PCB board should be stored in a clean container or box with a temperature of 10-35°C and a relative humidity of not more than 75%. The surrounding environment should not be acidic or alkaline.

The precautions for applying PCBA potting material

1. If the potting material exceeds the shelf life, it is prohibited to use.

2. The storage container should be kept tightly closed after opening.

3. It is forbidden to pour the remaining potting material back into the original storage container, and keep it separately and tightly closed.

4. If the workshop or storage room is not opened for a long time (more than 12 hours), it should be ventilated for 15 minutes before entering.

5. If accidentally splashed into the eyes, immediately open the upper and lower eyelids, rinse with running water or normal saline, and then seek medical treatment.

6. If you feel unwell when brushing, you should quickly leave the job site to fresh air, give oxygen if you have difficulty breathing, and then seek medical treatment.

The components cannot brush potting material

1. High power with cooling surface or radiator components, power resistors, power diodes, cement resistors.

2. DIP switch, adjustable resistance, buzzer, battery holder, fuse holder (tube), IC holder, tact switch.

3. All types of sockets, pin headers, terminals and DB heads.

4, plug-in or stick-type light-emitting diodes, digital tubes.

5. Other parts and components specified by the drawings that cannot use insulating potting material.

6. The screw holes of the PCBA board cannot brush potting material.

The areas should not brushing & brushing potting material

1. Areas that cannot brush:

① Areas that require electrical connection, such as gold pads, gold fingers, metal through holes, test holes; ②Battery and battery holder; ③Connector; ④Fuse and shell; ⑤Cooling device; ⑥Jumper; ⑦The lens of the optical device; ⑧Potentiometer; ⑨Sensor; ⑩There is no sealed switch; ⑪Other areas where the coating will affect performance or operation.

2. Areas that mustbrush:

All solder joints, pins, component conductors.

https://www.grande-pcba.com/common-problems-and-requirements-of-brushing-pcba-potting-material/As the size of the electronic components of the PCBA circuit board is getting smaller and smaller, and the density is getting higher and higher; The influence on PCBA is also increasing, so we put forward higher requirements for the reliability of PCBA of electronic products. PCBA circuit board three-proof potting material can effectively achieve the protection effects of insulation, moisture-proof, anti-leakage, shock-proof, dust-proof, anti-salt spray, etc. Thereby improving the reliability of the circuit board, increasing its safety factor, and effectively delaying the service life.

Application of Potting Material

PCBA circuit board potting material is widely used in high-tech fields, such as high-end circuit boards in automobiles, home appliances, military electronics, aerospace, medical electronics, etc., which can improve product quality of PCBA circuit boards and effectively reduce rework.

In addition, the rise of emerging industries, the widespread use of electric vehicle charging piles, and unmanned aircraft have further expanded the use of conformal paint. At present, it has become a major trend to apply conformal paint on PCBA for protection.

Function of Potting Material

The potting material is used to protect PCBA circuit boards and related equipment from environmental erosion, whose function is mainly to improve the reliability of products, especially in harsh operating environments.

The potting material protects electronics from external elements such as extreme heat, humidity, moisture and dust. It also protects electronics from internal factors such as corrosion, whisker growth and short circuits within the system. In short, the potting material is equivalent to an insulating layer, which ensures that different components can operate normally and avoids premature failure of the PCB.

Operating requirements for brushing PCBA potting material

Brushing potting material should be carried out in a separate room, but it cannot be completely sealed, which must have good ventilation facilities.

Smoking, eating and drinking are prohibited in the operation room, and alcoholic beverages are not allowed before operating.

Wear masks or gas masks, rubber gloves, chemical protective glasses and other protective equipment during operation to avoid harm to the body. This also depends on the potting material products selected. If it is a benzene-containing product, you should pay great attention to protection. And fire protection, and if it is a TIS-NM environmentally friendly potting material product, the safety is much higher, and there is no risk of burning.

After the work is completed, the used utensils should be cleaned in time, the tools and equipments should be sorted and tested, and the containers with potting material should be tightly covered.

The workplace should be clean and dust-free, no dust flying, and no unrelated personnel should be allowed to enter.

Tools and equipments should be fully grounded, and electrostatic protection measures should be taken.

Do not overlap the PCBA during operation; And the PCB board should be placed horizontally.

Before each batch of raw materials is used, a small sample curing test (3-5PCS) should be done.

Clean and bake the board. Dust, moisture and oil must be removed from the surface of the object to be coated so that the potting material is able to fully exert its protective effect. Thorough cleaning ensures that corrosive residues are completely removed and that the conformal coating adheres well to the board surface. Baking conditions: 60°C, 10-20 minutes, it is better to apply while hot after taking it out of the oven.

When brushing, the board should be placed as flat as possible. There should be no dew after brushing. The brushing should be flat and there should be no exposed parts. It is appropriate between 0.1-0.3mm.

Before brushing and spraying, ensure that the diluted product is fully agitated and left for 2 hours before brushing or spraying. Using a high quality natural fiber brush, lightly brush and dip at room temperature. If a machine is used, the viscosity of the paint should be measured (with a viscosity agent or flow cup), and a diluent can be used to adjust the viscosity.

The circuit board assembly should be immersed in the paint tank vertically. The connector should not be immersed unless carefully covered, and the circuit board should be immersed for 1 minute until the bubbles disappear, and then slowly taken out. A uniform film will be formed on the surface of the circuit board. Most of the paint residue should be allowed to flow from the board back to the immersion filmer. TFCF has different coating requirements. The immersion speed of circuit boards or components should not be too fast to avoid excessive bubbles.

When using it again after dipping, if there is crusting on the surface, remove the skin and continue to use it.

After brushing, lay it flat on the bracket and prepare to cure. The method that needs to be heated is to accelerate the curing of the potting material. If the potting material surface is uneven or contains air bubbles, curing in a high temperature oven should be left at room temperature for an additional time to allow the solvent to flash out.

Technical requirements for brushing PCBA potting material

The potting material protection must be tested, qualified and thoroughly cleaned before PCB Assembly.

The brush used should be kept clean, and it is forbidden to use it for other operations; When applying the potting material to the brush, be careful not to drip into the components that do not need to be coated; And the brush should be cleaned with thinner after use.

The coating layer should be transparent and cover the PCB board and components evenly, with uniform color and consistency.

The process steps are: Brushing A surface → A Surface Drying → Brushing B surface → Curing At Room Temperature

Spraying thickness: Spraying thickness is 0.1mm—0.3mm (dry film thickness is generally 30-100UM)

All coating operations should be carried out under the conditions of not lower than 16°C and relative humidity lower than 75%. As a composite material, PCB will absorb moisture. If it is not dehumidified, the potting material cannot fully protect it. Pre-drying and vacuum drying can remove most of the moisture.

Thickness Test Method:

1. Dry film thickness measuring tool: A. Micrometer (IPC-CC-830B); B. Dry film thickness gauge (iron base)

2. Wet film thickness measurement: The thickness of the wet film can be obtained by the wet film thickness gauge, and then the thickness of the dry film can be calculated by the proportion of the solid content of the glue.

Many circuit boards undergo cross-sectional inspection after selective coating to ensure potting material coverage and thickness are met.

It is well known that equipment, technology, and craftsmanship in PCBA all affect the boards quality, and the other part is what we will discuss here, that is, components. Components are the core components of the circuit board, and the quality of components is directly related to the final quality of PCBA. The component market is mixed, and how to avoid fake components is an essential skill for a professional PCBA manufacturer.The current components market is a quite chaotic, which means not only the price is unstable, but the quality is also uneven. Some people take advantage of the chaotic opportunity to sell dismantling materials, scraps, and three-no bad quality products. This has greatly tested the ability of various PCBA factories to identify fake components.

Commonly Used Methods To Identify Fake Components

1. Visual InspectionThe easiest way to check for fake components is visual inspection. This includes checking the part numbers and silk screen markings on the components against the specifications provided by the source manufacturer. In addition, you can use previous data and products purchased from suppliers in the past to verify the validity of the date code. Other aspects of the visual inspection are as follows:

Fraudsters may use black layers to place different part numbers and date codes on components. It involves applying a thin black epoxy coating on the top of the component and then roughening the surface to obtain the desired texture. It also includes matching the font to the original font. In order to determine if there is a power failure, it is important to check the top and surface texture of the components. In addition, it is necessary to compare the manufacturer’s symbol with known original components.Before proofing Assembled PCB, you should also check whether the leads of the components are damaged, re-tinning, etc. 

This is part of the incoming inspection and cannot be ignored due to the tight delivery time.Other factors that need to be considered in the device include component orientation, overall appearance, contact conditions, and visual inconsistencies.

2. Electrical Test

Electrical testing of fake electronic components involves verification of resistance and capacitance values ​​and full-function analysis of active components. Various contract manufacturers (CM) and third-party test laboratories have electronic test facilities. In order to test complex products, expensive test setup and programming expertise are essential, which can only be achieved in OCM or some third-party laboratories. When the main component is abnormal, you can also apply to the source factory for evaluation.

3. X-ray Inspection

X-ray inspection of hidden/internal characteristics of components. When comparing, it is always beneficial to have a gold standard or a famous example. This method checks and verifies the physical dimensions, lead frame and connection wires. In addition, it also checks for any internal changes in all components.

4. XRF Technology

XRF stands for X-ray fluorescence spectroscopy. This technology determines the elemental composition of materials and is most suitable for verifying RoHS compliance.

https://www.grande-pcba.com/where-can-i-do-fpc-flex-pcb-assembly/Grande has its own PCB Fctory and SMT Assembly factory, which can provide FPC Flex PCB Fabrication and FPC PCBA Manufacturing services!

Flex PCB Assembly Capability

Number of Rigid-Flex PCB / Flex PCB Layers: 10/6;

Minimum Trace Width & Spacing: 3/3mil;

Board Thickness Aperture Ratio: 12:1;

Distance From Hole to Conductor: 6mil;

Impedance Tolerance (Ω): 10%;

Surface Finish: Chemical immersion gold, immersion tin, HASL, hard gold plating, soft gold, silver paste, etc.

Common Types of Flex PCB

At present, Flex PCB has four types: Single-Sided FPC, Double-Sided FPC, Multilayer Flex PCB & Rigid-Flex PCB.

1. Single-Sided FPC: The lowest cost printed circuit board that do not require high electrical performance. In Single-Sided FPC Layout, it has a layer of chemically etched conductive patterns, and the conductive pattern layer on the surface of the flexible insulating substrate is a rolled copper foil. The insulating substrate can be polyimide, polyethylene terephthalate, aramid cellulose ester and polyvinyl chloride.

2. The Double-Sided FPC: A conductive pattern made by etching on both sides of the insulating base film. The metallized hole connects the patterns on both sides of the insulating material to form a conductive path to meet the design and use function of flexibility. The coverlay can protect single and double-sided traces and indicate where the components are placed.

3. Multiayer Flex PCB: To laminate 3 or more layers of single-sided or double-sided FPC together, and form metallized holes by drilling and electroplating to form conductive paths between different layers. In this way, no complicated soldering process is required. Multilayer circuits have huge functional differences in terms of higher reliability, better thermal conductivity and more convenient assembly performance. When designing the layout, the mutual influence of assembly size, number of layers and flexibility should be considered.

4. The traditional Rigid-Flex PCB: Be composed of rigid and flexible substrates selectively laminated together. The structure is tight, and the metallized hole L forms a conductive connection. If a printed board has components on the front and back sides, rigid flexible circuit boards are a good choice.But if all the components are on one side, it will be more economical to choose a double-sided flexible circuit board and laminate a layer of FR4 reinforced material on its back.

5. The FPC flex circuit board with hybrid structure is a multi-layer board, and the conductive layer is made of different metals. An 8-layer board uses FR-4 as the inner layer medium and polyimide as the outer layer medium. Leads extend from three different directions of the main board, and each lead is made of a different metal. Constantan alloy, copper and gold are used as independent leads. This kind of hybrid structure is mostly used in the relationship between electrical signal conversion and heat conversion and under low temperature conditions where the electrical performance is relatively harsh. It is the only feasible solution. It can be evaluated by the convenience of the internal connection design and the total cost to achieve the best performance-price ratio.

As you probably know, not every PCB Design has the same strict rules like the spacing required for high-voltage PCB Design. Generally, if the normal working voltage of your product reaches or exceeds 30 VAC or 60 VDC, then you should terribly diligently consider the spacing rules in the circuit board design. If you have high-density circuit boards, especially high-voltage circuit boards, then you need pay more attention to. High density makes spacing more difficult and more important for protection. 

Spacing is more important in high voltage PCB design, because the voltage on the circuit board assembly makes the arc between two conductive components more likely to occur on the printed circuit board. Any arc that does occur will bring higher risks to products and users. To help reduce risk, there are two main spacing measurement standards in PCB design, that is Electrical Clearance & Creepage Distance.      

 What is Electrical Clearance In PCB Design? 

Electrical Clearance is the shortest distance through air between two conductors. And its definition takes into account remove the clearance, such as how much space is in the air before my head hits something. If the electrical clearance anywhere on the PCB is too small, an overvoltage event may create an arc between adjacent conductive components on the circuit board. The Electrical Clearance rules vary with PCB material, voltage and environmental conditions. Among them, the environmental impact is quite significant. Most commonly, humidity changes the breakdown voltage of the air and affects the possibility of arcing. Dust is another standard factor, because particles gathered on the PCB surface will form tracks over time, shortening the distance between conductors. Arcs can damage your products and users, so the spacing on the circuit board is a key design parameter.  

What is Creepage Distance In PCB Design? 

Similar to Electrical Clearance, Creepage Distance measures the distance between conductors on the PCB. However, instead of measuring the distance in the air, it measures the shortest distance along the surface of the insulating material. The board material and environment also affect the creepage distance requirements. The accumulation of moisture or particles on the circuit board is able to shorten the creepage distance, which is the same as when it is cleared. When you use a high-density design, creepage may be a difficult requirement to meet. Since moving rails are rarely the first choice, there are other techniques for increasing the surface distance in the design. By adding slots or vertical isolation barriers between the tracks, the creepage distance can be significantly increased without changing the trace layout on the printed circuit board.      

Consider Comparing Tracking Index (CTI of Your Material) After the operating voltage, the most important factors in the Electrical Clearance and leakage requirements come from the material properties of the PCB. The electrical insulation of a material is represented by the "comparative tracking index" or CTI value. CTI is expressed as voltage, which is determined by standard tests and measures when a failure occurs on the surface of a material. According to the breakdown value of the material, there are 0 to 5 categories. The mandatory insulation rating of the product is based on these CTI categories. Category 5 is the lowest, with values ​​less than 100 V. For 600+ V faults, category 0 has the most powerful and often expensive material options. PCB insulator materials have different breakdown voltages and corresponding product application safety categories.    

     So What Sholud We Do? How To Use The Correct Material & Spacing? 

Since there are many variables in PCB design and material selection, the best option to meet safety requirements and standards is to go straight to the source. There are two standards I refer to most often. The first is IPC-2221, which is a general standard for PCB design Electrical Clearance and Creepage Distance guidance. The second is IEC-60950-1 (2nd edition). The IEC version is the standard you want to read for any IT products with AC mains or battery power, especially if you want to sell these products internationally. 

Identifying and merging standards can be very time consuming, so you should use good PCB Design Software. The best software for PCB design allows you to create specific design rules and helps you find problems early in the process. And AltiumDesigner® meets these requirements and more; you can start designing before choosing a circuit board insulation material!   

Vias-in-pad or vias-on-pad is a very headache for printed circuit board assembly factories, especially when the vias are placed on the BGA (Ball Grind Array) pad. However, design units often force assembly factories to follow suit due to insufficient design space or other insurmountable reasons.

As a matter of fact, with the shrinking of electronic products, the density of circuit boards is getting higher and higher, and the number of layers is increasing. Therefore, plenty of PCB layout engineers (CAD layout engagers) place the through holes on the solder pads; However, those small pitch BGA pads do not really have much space for the vias.

However, placing vias on the soldering pads saves space on the circuit board, but it is a catastrophe for SMT and manufacturing engineers, because it is likely to cause the following quality problems. Uncertainly, it was RD himself who returned to the carbine at the end:

1. If the via is placed on the solder pad of the BGA, it is likely to form a head-in-pillow (pillow effect or double-head effect) or bubbles inside the solder ball (Bubbles).

Because the solder paste is printed on the via hole, the air will be enclosed in the via hole. When the circuit board flows through the high temperature zone of the reflow furnace, the air in the via hole will expand due to heat and try to escape. The air that does not go out will form holes (Void/bubble) in the BGA solder balls, and in severe cases, it may even cause the head in pillow.

2. When the air accumulated in the through hole flows through the reflow oven, the air will be thermally expanded and there is a danger of out-gassing.

This usually occurs in a poorly preheated reflow profile. When the temperature rises too fast, the air expands rapidly, and the gas cannot escape effectively, and it will eventually burst out of the solder ball.

3. The solder paste will flow into the via hole due to pertaining to capillary, resulting in insufficient amount of tin that must be soldered in contact or lack of solder, etc. Or even flow to the opposite side of the board, causing a short circuit.

However, as product designs are getting smaller and smaller, PCB layout engineers have reached the point where they must compare the territory of the circuit board, and sometimes there should be room for compromise. Therefore, there are some alternative methods to deal with the through holes on the solder pads. The following figure shows five types of through holes from A to E and their impact on the SMT process:

Five designs of vias-in-pad

A) The vias are not processed at all.

This should not be accepted by manufacturing engineers, because tin will flow through this via hole after being heated, resulting in insufficient soldering, empty soldering and other undesirable phenomena, and the amount of tin is completely uncontrollable, and it may affect the parts on the other side of the board. Cause a short circuit.

C) Blind hole.

It can barely be used, but there is still a big risk. The amount of tin can be controlled, but when the solder paste covers the semi-buried hole, the air will be sealed in the semi-buried hole. When the circuit board passes through the reflow oven for heating, the air will explode the solder paste due to expansion, or form an escape channel. Short-term use may be no problem, but after long-term use, it may slowly crack from the escape channel, resulting in poor contact.

B) and D) are the best via design.

There are no holes on the solder paste pad to affect the amount of solder paste, and no additional bubbles are formed.

E) It can be used, but the price is much expensive.

A copper electroplating process can be added after the circuit board process to fill up the semi-buried holes or through-holes. The filled holes will be slightly sunken, so they must be controlled within a certain size, especially 0.5mm pitch BGA board. Note: The board of this process generally increases the price by about 10%.

In some BGA layout, in order to enhance the strength of the solder pad attached to the circuit board, the through hole is designed in the center of the BGA solder pad and the through hole is filled with copper, which is similar to punching a rivet on the solder pad to increase its strength.

The following is an example of the recently tamped QFN intermediate grounding pad. Nowadays, most of the QFN is used as a power controller, so its grounding and heat dissipation requirements are particularly high. The dense through holes like this can be used directly. The fate of solder paste printing is really strange results will happen.

↓This is the worst design. The through-holes are placed directly on the QFN grounding heat-dissipating pad, and the amount of tin cannot be ensured in manufacturing, and therefore, good soldering cannot be ensured.

↓This is also a bad design, but some of the through holes have been covered with green solder mask, but there are still some through holes that are not plugged.

↓This design is barely acceptable, only a through hole in the middle is left without a plug hole, and the hole diameter is also reduced.

This is the worst through-hole design. The through-hole is placed directly on the QFN grounding heat-dissipating pad, and the amount of tin can not be ensured in manufacturing, and which also cannot ensure good soldering. This is also a bad through hole design, but some of the through holes have been covered with green solder mask, and there are still some through holes that are not plugged. The design of this through hole is barely acceptable, only the middle through hole is not plugged, and the hole diameter is also reduced.

SMT factory overall arrangement and location requirements

1. Placement area of fire extinguisher

Fire extinguishers should be placed beside the column and around the SMT workshop, and placed in accordance with the requirements of fire protection regulations.

2.The placement area of the material storage cart

The materials storage cart is used for the SMT production line and the replacement of materials when the model is switched. In order to facilitate production and improve the efficiency of material replacement, it is best to place the material storage cart near the placement machine. Moreover, since the material can be replaced on both the front and rear sides of the placement machine, at least one material storage cart should be placed on both sides of the placement machine.

3. Placement area of the preparation table

The material preparation table is mainly used for the preparation of materials in the production process and the material preparation work before the machine switching. Therefore, the material preparation table should be placed near the placement machine; Also, it is best to put it together with the materials storage cart , so that it can be placed to the materials storage cart directly after the material is prepared.

4. Small table placement area for printing station

The small printing station table is used to place the auxiliary tools of the printing machine in production, such as wiping paper, solder paste, alcohol, etc. Considering easy access and use, it should be placed near the printing machine , and improve production efficiency.

5. Solder paste placement area

The solder paste placement area includes a refrigerator for storing solder paste, a solder paste mixer, a solder paste reheating cabinet, etc., which can be placed next to the column or in a fixed area around the workshop according to the requirements of the workshop; In a word, solder paste placement area should be convenient for production line to take solder paste.

6. Visual inspection area and maintenance area behind the furnace

In order to facilitate the visual inspection and maintenance of the semi-finished boards after the furnace, a small table is generally placed behind the furnace, which is specially used for the visual inspection and maintenance after the furnace, and the produced boards are promptly carried out to the next operations.

7. Stencil placement area

The stencil placement area includes a stencil storage cabinet, a stencil cleaning machine, a stencil inspection tool, etc., which are used for stencil storage, cleaning and stencil tension checking, but it should be convenient to take stencils in the production line.

8. Garbage placement area

The garbage in the production mainly comes from two parts, one is the dust-free paper used in the printing operation, and the other is the waste tray and waste belt caused by the replacement of materials. The garbage generated in these two parts should be placed separately for special recycling, especially the garbage used by the printing press. Therefore, the garbage area can be placed next to the printing machine and the placement machine, or a garbage placement area can be set up next to the column, and placed separately.

9. Checking boards placement area

SMT checking boards includes production checking and quality management checking, etc., which can be centrally placed next to the entrance and exit of the workshop or set up production checking boards area at the end of each production line to centrally place quality and others, so that producers and managers can check and understand the current SMT production status and quality status timely.

10. Boards placement area

The boards produced include finished boards and semi-finished boards. These two boards placement area should be separated and strictly distinguished to avoid confusion.

11. SMT spare tools placement area

SMT spare tools, including nozzles, motors, belts, cylinders, which should be placed in special areas to facilitate access during production, especially valuable spare tools; Meanwhile, safety settings should be taken.

12. Temperature and humidity location area

In order to better understand the temperature and humidity of the SMT workshop, according to the size of the workshop area, set up several temperature and humidity measurement areas, generally placed on the column or wall next to the production line.

13. SMT workshop office area

Let the engineering and technical personnel and management personnel work on-site in the SMT workshop, which can solve the technical and management problems encountered in production in time and ensure the smooth production of the SMT production line.

14. Area for anti-static measures

The personnel entering the SMT workshop must have an area where anti-static measures are taken. The area can be delineated at the door of the workshop, including the replacement of electrostatic clothing, shoes, hats, and each employee’s locker. In addition, an area dedicated to testing the electrostatic ring should be set up at the entrance of the SMT workshop so that each employee can do the electrostatic ring test and record the test results before starting to work.