Conductive adhesive fillets for double sided PCBs

Electronic devices manufactures are interested in research and development of new materials and processes for producing ecologically friendly PCBs. Lead-free solders or conductive adhesives are possible solutions for joining materials. But PCBs are still produced by chemical processes for pads and vias metallization. The objective of our research was to analyse the possibility of applying conductive adhesives for creating fillets in double sided PCB application. Single component, electrically conductive, silver filled epoxy-phenolic base resins were applied. FR-4 double sided laminates with through hole diameter 0.6 mm were used for trials. Adhesive fillet resistance and variation of fillet resistance after 1 to 5 reflow soldering were used as estimation criteria. Fillets for hole diameter 0.6 mm have resistance below 300 m/spl Omega/ and current overloading above 2.5 A.