Research And Application Of Hole Metallization Of PTFE High Frequency Circuit Board

The fifth-generation mobile communication technology(5G)will lead to a large number of applications of PTFE(polytetrafluoroethylene)high-frequency boards in highfrequency signal transmission.As high-frequency boards are developing toward highdensity,high number of multi-layer,etc.,reliable metallization holes are especially important in achieving layer interconnection.For the hole metallization of PTFE highfrequency printed circuit boards,the biggest difficulties include the drilling process and the activation desmear treatment before chemical copper deposition,which are hot spots in the industry research.Aiming at the problem of activation desmear treatment before chemical copper deposition of PTFE high-frequency board,this thesis uses plasma modification treatment method.The effect of plasma treatment with O2/CF4 mixed gases and N2/O2/CF4 mixed gases on the hole metallization of ceramic filled PTFE high frequency boards are investigated and analyzed by thermal stress test,contact angle test,XPS test,ATR-FTIR test and other characterization methods.By optimizing the plasma gas flow rate,treatment time and other factors,the optimal process parameters of plasma treatment with O2/CF4 mixed gases and N2/O2/CF4 mixed gases were obtained.The fractal dimension of the hole wall is calculated by the box counting method of fractal theory to qualitatively evaluate the cleaning effect of plasma on the pore wall.The results show that after the plasma treatment with appropriate parameters,the content of non-polar functional groups on the surface of PTFE decreases,and a certain amount of polar functional groups such as CO,C=O,O-C=O,OF are formed on the surface of PTFE.The contact angle is decreased,the wettability is enhanced,and the quality of the hole metallization is improved.Compared with plasma treatment with O2/CF4 mixed gases,plasma treatment with N2/O2/CF4 mixed gases is more advantageous in improving the hole metallization quality of the PTFE highfrequency board.The lowest fractal dimension is associated with the best qualified surface plasma treatment for PTFE drilling hole.PTFE high-frequency mixing-laminted board have been the popular printed circuit board type for the reason of achieving high-frequency and high-speed functions and a reduced price.Aiming at the technical processing problems of the blind hole and throughhole of PTFE High-frequency mixing-laminted board,the integrated balance method and the comprehensive scoring method are used to optimize the important mechanical drilling parameters such as feed speed of through-hole and the key laser drilling parameters such as the pulse width of the blind hole in the mixing-laminted board.The best processing parameters for the production of blind holes and through-holes are obtained.The influences of the type of aluminum plate,phenolic paper laminate and the life of the drill,plasma desmear parameters,washing method of post-drilling board on its drilling quality are studied.The results show that for blind holes,the deepness of concave decreases with increasing the circularity of blind holes.The upper and lower aperture ratios are only within a certain range,and the blind hole quality is better.Regardless of whether plasma desmear or chemical desmear plus plasma desmear,there is no residual glue in blind holes,and it can be seen that from the average and maximum value of the deepness of concave of blind hole,the use of chemical desmear plus plasma desmear is better.For the throughhole,the cutting life of the new drill and the second-used drill is determined by the relationship between the life of the drill and the hole roughness,the nail head,the diameter of the drilled through-holes.Using drilling parameters with high rotationl speed and low feed rate in mechanical drilling,using new drill,MVC aluminum sheet and phenolic paper laminate,washing board with high pressure water after drilling and combining with O2/CF4/N2 plasma desmear can obtain better type and quality through-holes.