Studies of Silver Catalyst System in Print-Circuit Board Application

Surface activation by palladium, either in colloidal or ionic form, has been widely accepted in printed circuit board industry. Palladium catalysts generally provide highly effective surface activation for electroless copper deposition on dielectric surface in making holes conductive (MHC) process. Unit price of palladium has almost doubled up in recent two years. The surge in unit price of this key metal in MHC process increases production cost of printed circuit board. The economic pressure leads to development of alternative catalytic chemistry which has lower cost and comparable, or even better, plating performance. Silver is another precious metal catalyst which shows promising experimental results in catalyzing electroless copper plating, and has the advantage of relatively stable metal unit price. However, new processes like silver catalyst need comprehensive data to demonstrate its industrial applicability without compromise the interconnect reliabilities.In this paper, the potential of silver catalyst process have been exploited and its corresponding performances in interconnect reliabilities were systematically studied. A standard test vehicle with and without preconditioning was used prior to the different kinds of thermal cycling tests. The test results were further supported by microstructural examination using advanced microscopy.