#rf circuit

Every Electronic PCB Manufacturing Company that excels in the business usually starts by selecting the appropriate materials for a specific project. The objective is to always use the right raw materials for making the boards. At the same time, the company aims to meet the requirements associated with electricity and temperature.

Silicon on insulator Market By Technology (Thick-Film, Thin-Film, Bond and Etch-Back SOI & Others); By Product (RF Circuit, Memory Device & Others) & By Application (Automotive, Photonics & Others)

A foreword World electronic product enter one quick speed already and density higher and volume thin and cost low requiring effective thermolytic capsulation eraing. With the intersection of radio communication and field ' Such as mobile phone) Fast for commercialization,to lowering costs, have by larger pressure by characteristic. LTCC (low-temperature co-sintered ceramic) Technology is a low-cost encapsulated solution, have short characteristic of lead time. This text comments and utilizes LTCC technology satisfy the microelectronic industrial development, especially the applied feasibility on the high-power RF circuit requirement. 2LTCC technological general view LTCC whether one laminate multilayer circuit that make together unsintered the intersection of casting and ceramic material, have print interconnect conductor, component, circuit inside, structural the intersection of calcination and an integrated type ceramic multi-ply this. LTCC utilizes dielectric material casting of routine thick layer, but not silk screen printing medium sizing agent. Born the intersection of porcelain and strip, cut into the intersection of magnitude and appropriate size, type mating hole and inner chamber, the communication pore adopt the laser boring or mechanical bore hole to take shape each other. Reach the conductor on per layer of ceramic wafer together with required resistor, capacitor, inductor screen printing or litho. Then every layer ceramic chip is aimed at, laminates and the co-sintering at 850 ℃. And carry on surface mounting with the Off-The-Shelf thick-film circuit production technology layout substrate. 3LTCC craft general view LTCC raw material made up of organic and inorganic composition admixture. The organic composition is polymer adhesive and dissolves and makes up plasticizer of solution. For example polyvinyl alcohol contracts butanal, gathers and moulds aldehyde propanone and low-grade alkane ' Hydrocarbon) Group acrylate polymer altogether. Acrylate still inuse, because they can in binder removal (between 300 ℃ of temperature -400 ℃ under air clean, under the inert atmosphere) . Require adhesives to be Tg low, the molecule is tall in intensity, it is good to arrange the glue characteristic. The adhesive is usually 5% wt (the percentage of the adhesive is the higher, the shrinkage after calcination is the higher) . The inorganic part is made up of pottery and glass, usually press 1: 3 proportioning. The ceramic choice depends on the required characteristic, such as thermal expansion coefficient (CTE) And thermal conductivity. The preferred low CTE pottery is quartz glass, mullite, cordierite and Zirconium oxide. In order to realize more high CTE, the preferred pottery is Al2O3, quartz, forsterite and calcium zirconate. The required characteristic of vitreous choice reliance, such as dielectric constant, adhesion, CTE and loss tangent value. The glass softening point must be up to finishing binder removal before beginning to densify, it is low to guarantee the sintering of high density. There are two formic acid, propanone, xylene, methanol and ethanol commonly used plasticizer and solvent. Then every component once is in the suspension liquid of the paint ' Called the glaze slip) China mills and uniformization, pours and takes (usually the membrane of polyester) in a moving year ,Through a dry section, remove all solvents, through controlling the interval of chasing, the required thickness of casting, the degree of viscosity and carrying the shrinkage. This technological general thickness tolerances is ± 6%. Other casting technology can be used for realizing smaller tolerance. Fig. 1LTCC typical calcination contours Then is grown ' Not sintering) The porcelain is taken and launched on the stainless steel desk, cut slice (slightly greater than the vane size) . Heat the intersection of preconditioning and ceramic wafer for less than about 30 minute at 120 ℃' Or preserve for 24 hours in N2 dry box) . Adopt the punch press to wash the ceramic chip of pretreated growing into the working size finally. Position the figure and produce in this course too. Form the via hole, utilize machinery to ram, the bore hole or laser boring technology to form the via hole next. Via hole puncture that show at growing ceramic chip ' Usually the diameter is 5 Mills- 8 Mills) ,Use it on different floor with the interconnection circuit. Also want the punching mould hole, the alignment while helping the lamination at this stage; The automatic video is aligned when mating hole are used for printing conductors with the medium. Then it is the via hole that is packed, utilize traditional thick layer to screen print or push and pack the conductor sizing agent of the high solid particle content of the special prescription to the via hole. The programmable computerized numerical control punch press can be used for getting stainless steel or brass masterplate. The via hole wants and grows the porcelain and take the shrinkage to match while packing the shrinkage of the sizing agent. It is the canonial thick layer printing technology of use that prints and dries the sizing agent of conductor next. The via hole is packed and the conductor figure is dried for about 5 minutes in 120 ℃ box furnaces. Depending upon need, all resistors, capacitors and inductors are printed and dried at this stage. Then check, sort out and align. Check, sort out and aim at different layer, make the mating hole in each layer concentric and plan to laminate. While laminating ' Both single axle and isostatic pressing) ,Put the group layer in order and collimated the hot pressing together (it is usually 70 ℃, 3000psi leaves for 10 minutes) . Then a step co-sintering laminates. The area between 200 ℃- 500 ℃ is known as the organic binder removal district (propose 60 minutes at least in the thermal insulation of laminating of this area) . Then in 5 minutes- Laminate from co-sintering to peak temperature 15 minute ' It is usually 850 ℃) . The metallized model of calcination of atmosphere is arranged and will be used to glue the curve of calcination for 2 hours - 10 hours, . The part of calcination burns the craft after getting ready, such as printing conductor and accurate resistor on the top surface, then the calcination in the air. If Cu is used in metallizedly, sintering must go on in N2 chain stove. Go on laser transfer, hinder to circuit ' If need) , test, slices and test. Can be with lead wire of brazing or air-cooling fin (if need) in LTCC capsulates . At this stage, capsulate and get the subsequent craft ready, u.i.. Casting Tape coiling Section Preconditioning Vane Layer one Punching The via hole is packed Print conductors Test /check /correctly location Lamination Calcination / co-sintering And then burn the craft Electric test Section At the time of the multi-layer craft, should repeat between 6th step and 10th step. Characteristic of 4LTCC material 4. 1 grows the porcelain and takes materials It is that LTCC system confirms the principal ingredients of the key characteristic to grow the porcelain tape, including dielectric constant, lossing factor, insulation resistance, spark-over voltage, bending strength, CTE and thermal conductivity. 4. 2 conductors The sizing agent of conductor screen prints the conductor part of the shaper. Particle size, particle organization and size distribution play an important role on final electrical property and physical property of determining the calcination conductor. Choose appropriate and metallizedly to depend on the associations of various factors, such as electrical resistivity, weldability, the intersection of lead wire and binding force, and other compatibility, use of component under system ' The via hole packs, welds, ground plane) , electron transfer, decays, RF characteristic, thermal conductivity, current carrying capacity, adhesion, rheology, corrosion resistance, appearance and cost. Table 1 enumerates various metallized materials which LTCC technology adopted out. What deserves to be mentioned is the intersection of photoengraving and acquisition of conductor, because it can produce very detailed lines and interval at LTCC base plate ' Conductor material that the table 1LTCC adopts 4. Sizing agent of resistance 3 The sizing agent of thick-film resistor is used for making passive resistor component. The sizing agent of resistance is made up of frit, conductive powder and organic vehicle admixture like sizing agent of conductor. Realize different electrical resistivities (glass content is the higher through changing the proportioning of glass and conductive powder, the electrical resistivity is the higher) . The resistor of most atmosphere calcination is making on the conductive phase material, such as ruthenium acid salt, ruthenic acid bismuth and ruthenic acid lead. Choose the appropriate resistance materials to depend on the demand such as sheet resistance, power consumption, frequency response, temperature-resistance coefficient, short-term over load and upper voltage,etc.. LTCC applied resistance materials surface installation type and embedded type two kinds. Surface installation type resistor,its resistance-value from 5Ω / -2MΩ / ,It can be even as small as ± 1% to adjust the tolerance after hindering. Embedded resistor resistance-value range from 10Ω / -100kΩ / . Because embedded can't adjust and hinder before calcination, tolerance is generally ± 25%. Spiral inductor of Fig. 2 4. 4 condenser dielectric The apparatus material of electric capacity has tape-carrier type and sizing agent type. The electric capacity dielectric constant of LTCC system is from 3.9- 200. The reseach of the high K material is to substitute X7R, the keys of Z5U and Model NPO capacitor. Range of capacity of X7R capacitor is 10pF- 3000pF, but NPO type is less than 0.3%, as shown in Table 2. Applied capacitor of table 2LTCC system 4. 5 inductor sizing agent The inductor can be integrated in LTCC system too, but this technology has not been ripe yet. Various employ it such as round spiral, square spiral, snakelike and single annular inductor have already been used in RF field. It will influence final inductance and circuit Q to depend on for a living and interconnect to the electrode / board. The general equation of the linear type inductor is as follows: L(Ind.) =5.08* 10- 3* L* [Ln(L/(w+ t) + 1.19+ 0.022* L/(w+ t) *nH/mil Among them, L (Ind.) =Inductance (nH) L =Conductor length ( Mill) t =Conductor thickness ( Mill) w =Conductor width( Mill) The general relation of the spiral inductor is controlled by following equations: L(Ind.) =0.03125* N2* do* nH/mil do =5* di =2.5n(w+ s) Among them, L (Ind.) =Inductance (nH) do =Spiral external diameter di =Spiral internal diameter N =Turn s =Interval of conductor w =Conductor width As to the spiral inductor, propose the line should be as wide as possible, keep the body of whole inductance little as much as possible in diameter at the same time (see Fig. 2) . In order to improve the energy storage of every unit length, there should be enough space to measure in the spiral centre, because surface resistance is changing with the radical function of square of frequency directly. The experiment shows, Q rises to certain frequency, then fall after rise rapidly. In addition, the experiment shows, as to the same inner size, round spiral is 10% more high than square and spiral q-factor, though inductance quantity is nearly lower than 20%. 5 advantages of employing LTCC The lead time of LTCC is short, starts the low cost, it is a low-cost packaging method. It utilizes all imaging material, in order to form fine line and interval through thin film technology as to the low cost. LTCC has firm, dense and reliable capsulation, can make into the multilayer structure, realize micromation through the integrated passive component such as resistor, capacitor and inductor. Passive component these print when superficial layer, can laser transfer hinder to very much little tolerance too. In addition, the dielectric constant of LTCC is low (low to 3.9) , the dielectric loss is low and decays low. The capsulation that is made has different CTE and thermal conductivity to require. LTCC bonding lead and air-cooling fin material, there is the high density that 3D designs that is interconnected, embedded and passive and 3D component. Process and allow to examine specific layer and all layers of advantages of co-sintering at the same time parallelly, form final high yield and low cost. While standing under different temperature and damp condition, compare with other RF optical disk substrate materialses, influence the material characterization of RF characteristic, it is still relatively stable and decay such as the dielectric constant, dielectric loss. LTCC have ability of cavity pocket, can paste get air-cooling fin directly chip, then utilize wire bond reach different layer the intersection of terminal and linkage. 6 conclusions LTCC has offered the strong advantage for the fact that high-power RF is employed, it is enough to remedy its defect. One that is with new material is studied and improved constantly, in near future, employ while choosing base plate and packaging technique for high-power RF, LTCC will become one of the optimal choices. http://www.icembed.com/info.asp? ArticleID =27077&ArticlePage =1