Creep Analysis of a Lead-free Surface Mount Device

In this paper finite element analysis (FEA) is used to understand the effect of a non-uniform temperature distribution on the creep and fatigue behaviour of lead-free solder joints in an electronic assembly comprising of a chip resistor mounted on printed circuit board (PCB). Solder joints in surface mount devices (SMDs) operate over a temperature range as extreme as -55degC to 125degC, which is high compared to the melting temperature of solder alloys. Exposure of solder joints to these temperatures can result in thermo-mechanical fatigue. Eutectic or near- eutectic tin-lead alloys have previously been used as an interconnection material, but the ban imposed on the use of toxic materials in electronic products demands new lead-free solder materials. This paper presents the experiments carried out using a thermal camera to obtain the real temperature distribution in the electronic assembly. These temperature distributions were used in FEA of the chip resistor under temperature cycling conditions. Unlike accelerated tests for obtaining reliability data, FEA is quick and less expensive.