Study On Surface Modification And Metal Finishing Of Printed Circuit Substrate

The development and construction of 5G communication promote the development of printed circuit board?PCB?to high frequency,high speed,high reliability and high functionalization,thereby inducing new challenges to the processing technology of existing PCB substrates and the growth of intermetallic compounds?IMCs?between metal-modified PCB substrates and solders.In this paper,the effect of surface modification of PCB substrates on its metallization,the influence of metal modification and environmental conditions on the growth and evolution of IMCs,and the influence of metal modification transmission line of IMCs growth on signal transmission were investigated based on the realization of effective electrical connection between metallized PCB substrates with high reliability and microelectronic components.The research results could impove the reliability of solder joints in electronic packaging technology and signal transmission stability.The contents are detailed as follows.The modification effect of air plasma on epoxy resin substrate was studied.The influence of plasma modification on the interface performance of epoxy resin substrate was analyzed by multiple characterizations including morphological,chemical and surface tension-based measurements while electroless copper plating experiments were carried out to verify the effect of plasma modification on the quality of copper plating.The results show that the roughened shape and the oxidized chemical groups at surface are the major causes of modified interface properties of epoxy resin substrate.Subsequent electroless copper plating tests demonstrate that plasma treatment significantly improves the quality of electroless copper deposition in PCB manufacturing process,and copper plating layer with uniform coating and less roughness can be obtained after air plasma modification.The adhesion of electroless copper plating on the surface of carbon fiber/cyanate ester composites under different coarsening conditions and the application of electroless copper plating on the composites as conductive patterns were studied.The results show that the surface morphology and hydrophilicity of the composite after different coarsening treatments get modified,thus affecting the adhesion,surface roughness and surface morphology of copper layer.Under the combined action with sand-grinding and the oxidation of potassium permanganate,the plating copper layer with good crystallization,density and adhesion is obtained on the surface of the composite.The plating copper layer with the low resistivity of 2.56×10^-6?cm on the composite has good conductive performance to form circuit connection.The morphology and growth kinetics of the intermetallic compounds?IMCs?at the interface of Sn-3Ag-0.5Cu?SAC305?solder and PCB substrates with different deposited copper layers?including electroless copper,electroplated copper,sputtered copper?were investigated under the conditions of isothermal aging,thermal shock and multiple reflow.And the influence of IMCs on signal integrity after isothermal aging treatment was also discussed.The results indicate that IMCs emerged on metal-modified PCB substrates with discrepant microstructure have evident differences in morphology and thickness.And the microstructure,composition and growth thickness of the IMCs naturally get changed during variational conditions.Solder joints on microstrip can lead to signal loss and overgrown IMCs emerged at interface will further aggravate the signal loss.