Optical and Auger Microanalyses of Solder Adhesion Failures in Printed Circuit Boards

K. Kumar
1981 Journal of the Electrochemical Society  
Printed circuit boards used in electrical systems have shown solder separation from the copper wiring network with prolonged use at about 325 K (120~176 Optical and Auger microanalyses of boards that have shown such failures have revealed the existence of discrete oxide particles in the form of an oxide layer at the separated interface. High temperature accelerated aging tests have shown that the time-dependent accumulation of the oxide particles at this interface results from rejection of the
more » ... xygen out of the reacted zone and into the intermetallic-matrix boundary with the continued growth of (low Pb-containing) CuxSn~ intermetallic compounds. (These compounds are formed as a consequence of the chemical reaction that occurs between the Pb-Sn solder and the underlying copper circuit.) Increased thermal activation leads to increased growth of the intermetaUics, and this results in more oxygen exclusion from the reacted zone into the interface region (giving rise to a time-dependent accumulation of the oxide particles at this boundary). Eventually, these particles inhibit the solid-state diffusion reaction between copper and the CuxSny intermetallics and lead to the observed separation of the solder from the underlying copper. Experiments performed in this study have shown that the oxygen (giving rise to oxide-particle accumulation at the interface) is distributed throughout the bulk of the copper plating. Organic addition agents, codeposited with the copper during the formation of the copper wiring network, are probably acting as a source for the observed oxygen. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 207.241.231.82 Downloaded on 2018-07-20 to IP
doi:10.1149/1.2127425 fatcat:fkrdqhta3zalfcuup6d4hc2ph4