Fatigue-creep crack propagation path in solder joints under thermal cycling
Authors: Liu, D.; Pao, Yi-Hsin
Source: Journal of Electronic Materials, Volume 26, Number 9, September 1997 , pp. 1058-1064(7)
Abstract:The present study investigates the thermal fatigue crack propagation path in a eutectic solder joint between a 2512 leadless chip resistor and a printed wiring board which had experienced thermal cycling between -55 and 125°C. This was achieved through the microstructural examination of fractured surfaces of the joints. Patches of finely spaced striations were observed in a predominant shear strain field in the joints. These striations were attributed to the tensile strain components in the field and used to add the identification of the fatigue crack propagation direction. It was observed that cracks did not simply propagate across the depth of the joint from the inner end (the heel) to the outer end (the toe) in the longitudinal direction, but from a corner point on the free edge of the heel to the center across the joint depth, making an angle of about 70° with respect to the longitudinal direction.
Document Type: Research Article
Publication date: September 1, 1997