The metallurgical mechanisms of solder fatigue
Thermal fatigue of solder joints is an important source of failure in electronic devices. Failures arise from the strain, most often in shear, imposed on the solder joint by the uneven thermal expansions of the joint constraining surfaces. Increased solder joint reliability and improved more fatigue resistant solders require an understanding of the metallurgical mechanisms operative during the fatigue cycle. The work that is reviewed here concentrates on the mechanisms of thermal fatigue and, in particular, their association with the solder microstructure. While the fatigue life of Pb-Sn solder joints is strongly dependent on operating conditions, the metallurgical mechanisms of failure are surprisingly constant for joints where the deformation occurs predominantly in shear at elevated temperatures and the solder exhibits the classic lamellar eutectic microstructure. Under these conditions, the shear strain in the joint is inhomogeneous and initiates a local recrystallization and softening of the solder microstructure. Fatigue cracks initiate in this softer microstructure to cause ultimate failure. The results outlined here identify and elucidate the role of the solder microstructure during thermal fatigue and suggest specific paths toward the design of superior solder alloys. 32 refs.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 7008757
- Report Number(s):
- LBL-28405; CONF-900271-2; ON: DE90008390
- Resource Relation:
- Conference: NEPCON '90: National Electronic Packaging and Production conference, Anaheim, CA (USA), 26 Feb - 1 Mar 1990
- Country of Publication:
- United States
- Language:
- English
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