not Available.

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 oxygen 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 re-