Deep toâLearn mSAP IC Substrate Technology
The never-ending demand for smaller, faster, and more powerful electronic devices has driven the semiconductor industry to innovate not only in chip design but alsoâin packaging and interconnect technologies. The Integrated Circuit (IC) substrate, which is the electrical interface to and the mechanical support for the silicon die, has seen dramaticâchanges. Among the various processing schemes, Modified Semi-Additive Process (mSAP)âis a breakthrough technology for making high density interconnect (HDI) substrates. This paper presents an in-depth analysis of the mSAP IC substrate technology including its manufacturing flow, process features as well as a directâcomparison to other widely utilized patterning techniques. For companies building the next generation of electronics,âworking with a leading mSAP IC Substrate supplier is key to realizing the potential of advanced chip architectures.
The Evolution of IC Substrate Patterning
Functionally, the IC substrate serves to provide the routing from the very high densityâinput/output pads of a semiconductor chip to the much lower density of a printed circuit board. With increasing chip input and output nums and decreasing pitches, the substrate needs to have finer linesâand spaces to meet the requirement of dense routing. Conventional PCB manufacturing processes, such as subtractive etching, areâchallenged when defining features finer than 30 micrometers . This requiredâthe introduction of additive techniques, which is how SAP and eventually mSAP came to be. An mSAP IC Substrate manufacturer takes advantage of this process to provide a solution that lies between the traditionalâPCB offering and the high density requirements of todayâs flip-chip and fan-out packages. To really know what mSAP is all about, youâneed to look at it relative to the prior and competing solutions.
The Subtractive, SAP and mSAP Process Compared
Three processes, Subtractive, SAP and mSAP, dominateâthe patterning of conductive lines on IC substrates. Each process has particular attributes, business implications, etc. subtraction processes has least environmental impactâand mSAP is most wasteful and harmfull. Subtractive Process: This is the conventional techniqueâfor making PCBs. It is based on a laminate core clad on both sides with a very thick layer of copperâfoil. Photoresist is deposited and patterned, revealingâcopper to be removed. Then the substrate is etched and the emailâsubstrate is etched and extraneous copper is cleaved away. One major disadvantageâof the subtractive process is undercutting. As copper is removed from the etchant in the vertical direction, it isâalso removed in the horizontal direction beneath the photoresist. This leads to line cross-sections that areâtrapezoidal which restricts how narrow and close lines and spaces can be. It isâusually not applicable to fine-pitch IC substrates. SAP (Semi-Additive Process): SAP is basically an additive process processing a dielectric substrate thatâis devoid of copper cladding. A very thin seed layer of copper is depositedâacross the whole area, commonly through electroless plating. Photoresist is spun on and then patterned to open the areas where the circuitryâis wanted. The copper is then electroplated in these open areas to the desiredâthickness. Finally the photoresist isâremoved and the thin seed layer is rapidly etched. SAP can produce extremely fine lines and spaces with almost vertical sidewalls but it is an involvedâand expensive process. mSAP (Modified Semi-Additive Process): shares mSAP is a semiâsubtractive/semi additive process. It begins with a laminate core with a thin layer of copperâfoil. This thin foil is the seedâlayer for subsequent plating. Like SAP, photoresist isâspun on and patterned to create circuit traces. Next, copper is electro plated onto the exposed thin foil toâform the needed thickness of the circuit. The photoresist is removed afterâplating. The essential final operation is the flash etch toâremove the original thin copper foil in the unplated portions. Since the starting copper foil is thin,âthe undercutting in the flash etching is very little enabling much finer features compared with the subtractive process, and more cost effective and more suitable for the existing manufacturing system infrastructure than pure SAP. A mSAP Substrate manufacturer can confidently achieve lineâand space from 12 to 25 microns.
The mSAP IC Substrate Manufacturing Flow
The mSAP IC substrate production process is an elaborate, multi-stage process requiring rigorousâenvironmental control and extremely high precision machines. A top mSAP Substrate supplier has a well-defined process flow toâmaintain yield and reliability. It startsâwith core preparation and drilling. The substrate material,ânormally a high-performance epoxy laminate with woven glass fiberglass, is drilled with holes to provide vertical electrical connections. After drilling the holes are processedâto remove resin smear, and then electroless copper is deposited on the entire surface. Resist lamination and imaging follow. A dry film photoresist is laminated to the copper cladâpanel and exposed with high-resolution direct imaging technology. The panel is developed to open up the thin copper seed layer under where the circuitry was formed with theâcopper seed layer. Copper pattern electroplatingâthickens up the traces and fills the vias to the desired thickness. Then the resistâis stripped and the thin seed layer is removed from the non-circuit areas by flash etching. This process stepâis what separates mSAP from subtractive etching and allows you to define fine-line patterns. The opportunity in solder mask application andâsurface finish, final inspection and testing.
Important Process Factors and Problems
The mSAP process lends itself to multiple advantages that have made it the preferred technology for high-densityâIC substrates. The main benefit is the possible resolution ofâfine line and space. Enhanced mSAP allows for line and space values as small as 15 micrometers with good dimensional control. The high density of routing is critical to support high input output counts fromâadvanced chip packages. mSAP produces nearly rectangular cross-section and vertical sidewallâconductor traces. This profile greatly enhances signalâintegrity, particularly at high frequency. By employing thin copper foils and high performance imaging techniques, an mSAP IC Substrate supplier can provide enhanced layer-to-layer registration, which is crucial for intricate multi-layerâsubstrates. But mSAP is a majorâhurdle. It is a process demanding very high purity,âotherwise the micro-particle contamination results in defects. Accurateâmanagement of plating uniformity, etching rate, and photoresist characteristics is important to maintain high yield. Theâbest mSAP IC Substrate manufacturer has to take advanced technology as backbone to surmount these difficulties by means of process engineering and quality control.
Functionsâof the mSAP IC Substrate Manufacturer
Selection of the appropriate manufacturing partner is critical for firms employing mSAP technology. High-end mSAP IC Substrateâmanufacturer should have world-leading facilities such as high precision laser drillers, direct imaging systems, advanced plating lines etc, and at the same time advanced mSAP IC Substrate technology know-how and expertise in materials and process.
In addition, top mSAP IC Substrate manufacturer also provides designâfor manufacturability(DfM) support by working with customers in the early stages of design to finalize the substrate design that fit for the mSAP process. It is a co-optimization toâget the highest yield, lowest cost and shortest time-to-market.
Conclusion
The mSAP IC substrate technology has given ratentation for growth inâthe semiconductor industry. Utilizing the advantages ofâadditive plating and the convenience of thin copper foils, mSAP is a scalable and cost effective process for the production of high density interconnects (HDI) used in current and next generation electronics. For semiconductor companies and system designers, gaining a thorough understanding of the complexities of the mSAP process and working withâa best-in-class mSAP IC Substrate manufacturer is critical to enabling product differentiation success in an ever more challenging electronics market.
