Abstract
The deterioration of surface mounted solder and adhesive joints on different substrate materials under thermal cycling was investigated metallographically. Ceramic chip resistors and leadless chip carriers were soft‐soldered or glued onto alumina, FR‐4, aluminium or steel boards and the various cracking modes were observed. Fatigue cracking in the solder under the component (mode A) took place in the case of resistors on an Al substrate and carriers on all boards except alumina. Cracking on the outward surface near the upper and lower corners (mode B) occurred on all boards, but most notably on alumina. Adhesive joints seemed to offer the highest fatigue strength, but their electrical properties suffered continuously in the course of cycling even though cracking was not observed at all in many cases.
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