ELECTROLESS NICKEL/ELECTROLESS PALLADIUM/IMMERSION GOLD PROCESS FOR MULTI-PURPOSE ASSEMBLY TECHNOLOGY

摘要

As the second part to a paper presented at the 2004 SMTA Pan Pacific Symposium, this paper further summarizes the results from technical qualification of the Ni/Pd/Au process. Whereas the previous paper examined the wire bonding capabilities of this surface finish, this second paper focuses specific attention to BGA applications. In these investigations, the solder joint integrity is measured using ball shear testing of BGAs as test vehicles. Ball shear performance of BGA solder joints is examined using both eutectic solder and a tin-silver-copper (SAC) alloy. Testing of eutectic Sn-Pb solder joints demonstrates the impact of thermo-cycling (500 cycles of -55°C to +125°C) on the Ni/Pd/Au surface in comparison to other selective finish methodologies (i.e. electroless nickel/gold and organic solderability preservatives). Similarly, ball shear testing of the SAC-alloy solder joints shows the impact of thermal aging (+150°C for 1000 hours) on the Ni/Pd/Au surface, compared to the performance of the more conventional electrolytic nickel/electrolytic gold process under the same test conditions. The overall reliability of solder ball attachment is characterized by both mechanical ball shear test results and visual inspection.