Shear Strength and Ductility Behavior
Computer units in the automobile are exposed to both high and low temperature. Consequently, solder joints experience repeated stress from expansion and contraction due to the difference in the coefficient of thermal expansion between the PCB and component, resulting in a crack in the solder joint.
Miniaturization is a recent trend in automotive components, so that when a BGA or a QFN/BTC component with low standoff and narrow pitch is frequently soldered. Consequently, there is a growing demand for the solder alloy composition to possess better thermal resistance than conventional SAC305(Sn/3.0Ag/0.5Cu) solder. To answer this demand, solid solution strengthened solder alloys which are tin (Sn) base alloys strengthened by Bismuth (Bi) and Antimony (Sb), hereinafter SAC+Bi,Sb solder are suggested. Although the strength is improved by these solder alloy compositions, and better thermal resistance than SAC305 is anticipated, it is also of concern that this composition may have different reliability reduction than SAC305, as its properties, such as ductility and hardiness are drastically different from SAC305.
In this paper, we will discuss the ductility and durability of a solder joint based on the shear strength test results of chip resistor soldered joints.