Microwave Tech - Microwave High-Frequency Board processing process is not easy

Based on the special physical and chemical properties of Microwave High-Frequency Board(Teflon PCB), the processing process is different from the traditional FR4 process. If the common epoxy glass fiber coppery clad plate is processed under the same conditions, there is no way to obtain the standard product.

(1) drilling: the base material is soft, the number of drilling boards to be less, generally 0.8mm plate thickness to two a stack is appropriate; Speed should be a little slower; To use a new drill bit, the tip Angle of the drill bit,screw Angle has its special requirements.

(2) printing resistance welding: after the spanner rot, printing resistance welding green oil can not be used before the roller brush grinding plate,so as not to damage the substrate. Chemical treatment of appearance is recommended. To do this: no grinding plate, printed solder resistance line, and copper surface average the same,no oxygen layer, is not easy.

(3) Hot air leveling: based on the external performance of natural fluorine resin, should try to prevent the sheet heating very fast, tin spray before 150 degree Celsius, about 30 minutes of preheating disposal, and then immediately spray tin. The temperature of the tin cylinder is not suitable to exceed 245 degree Celsius, otherwise, the adhesion of the isolated pad will be affected.

(4) milling appearance: fluoride natural resin soft, common plane milling appearance burrs too much, unfair, the need for a special appropriate plane milling appearance.

(5) inter-process transportation: it can not be placed vertically, but can only be placed horizontally in the basket. In the whole process, fingers can not touch the line pattern inside the board. The whole process to avoid scratches, scratches, line scratches, pinholes, indentation, the concave point will affect the signal transmission, the wrench will reject.

(6) etching: clamping side corrosion, serrated, notched son, line width tolerance clamping ±0.02mm. Use a 100x magnifying glass.

(7) Chemical copper precipitation: the pretreatment of chemical copper precipitation is not easy to solve the Teflon plate, but also a key step. There are many ways to deal with copper before settling, but to sum up, there are only two ways to adapt to mass production with stable quality.

Method 1: chemical method: add tetrahydrofuran solution to form sodium tetra complex, so that the surface atoms of the polytetrafluoroethylene board( Teflon PCB ) in the pore are eroded to achieve the goal of wetting the pore. This is a classic successful method, the effect is satisfactory, the quality is stable, but toxic, flammable, dangerous, needs special management.

Method 2: Plasma method (Plasma): demand for imported facilities, under the background of pumping air into vacuum state, between two high voltage perfusion carbon tetrafluoride (CF4) or argon (Ar2), nitrogen (N2), and oxygen (O2) gas, PCB in between the two electric, the cavity of Plasma formation, so the hole drilling sewage, dirt revenge. This method can be achieved to meet the average of the same effect, mass production is feasible. However, there are two well-known American Plasma companies, APS and March, which need to invest in an extremely expensive Plasma facility (more than 100,000 dollars per machine).In recent years, a little domestic literature also introduced a variety of other methods, but the classic effective methods are the above two. For ε3.38 andRogers Ro4003 high-frequency PCB substrate, with polytetrafluoroethyleneglass fiber substrate is roughly similar to the high-frequency performance, but also has FR4 substrate is roughly similar to the unique place of easy processing, this is a glass fiber and ceramic as filler, glass transition temperature Tg>280 degree Celsius high heat resistant material. This kind of base material drilling is very consumption bit, need to use special drilling machine parameters, milling shape to often change the planer; But another processing technology is roughly similar, do not have to make special hole disposal, so obtained a lot of PCB circuit board factory and customer's permission, but Ro4003 does not contain flame retardant, wrench to 371 degree Celsius, the wrench can be activated combustion phenomenon. State-run 704 plant LGC-046 sheet material, modified polytetrafluoroethylene board(Teflon PCB) ether (PPO) type, dielectric constant 3.2, processing performance with FR4, this product has also obtained many single licenses in China.