SYMPOSIA PAPER Published: 01 January 1988
STP24508S

Fatigue of Solder Joints in Surface Mount Devices

Source

Lifetime studies of a 16 I/O surface-mounted solder joint array undergoing isothermal cyclic fatigue in torsion shear under fixed plastic strain range show a strong correlation with creep fatigue and a creep-cracking mechanism. Experimental lifetime data follow an inverse dependence on matrix creep. Experimental measurement of the steady-state shear creep rate versus shear stress defines the creep characteristic that is sensitive to changes in metallurgical structure. The amounts of grain boundary and matrix creep taking place during a fatigue cycle are derived from experimental creep data combined with stress-strain hysteresis data obtained in steady-state cycling. Initially, thicker solder joints have a larger grain size than thinner solder joints, giving more matrix creep during fatigue and a faster failure rate. Fatigue increases the mean grain size of the solder joint as determined by the creep-rate-versus-stress characteristic and microstructure. Effects of grain size and joint thickness on lifetime are discussed. A maximum in the creep fatigue rate occurs at 333 K (60°C).

Author Information

Shine, MC
Digital Equipment Corporation, Andover, MA
Fox, LR
Digital Equipment Corporation, Andover, MA
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Details
Developed by Committee: E08
Pages: 588–610
DOI: 10.1520/STP24508S
ISBN-EB: 978-0-8031-5035-5
ISBN-13: 978-0-8031-0944-5