Solder joint reliability based on creep strain energy density for SAC305 and doped SAC solders

Abstract

Parallel to the development of new lead-free solders, electronic packaging has gone through a considerable evolution. A redistribution of layers allows the increase of functionality by increasing the number of inputs/outputsin the packagewhile reducing the size. The reliability of the package is strongly influenced by the reliability of the interconnects. During production and service life, there are thermal processes involved that may lead to thermal fatigue. In this work, a two-dimensional finite elementmodel of a Fan-Out Wafer Level Packaging (FO-WLP) was built, and simulations of thermal test cycles were carried out varying the solder interconnect material: SAC305, SACQ, SACR, orInnoLot. A thermal oscillating load from –40°C to 125°C was applied to the packaging for three hours.State of the art concerning solder joint reliability models based on creep behavior reveals the benefit of using energy-based parameters, as cycles to failure are inversely proportional to the average creep strain energy density.Based on theaverage creep strain energy density simulation results, the reliability of the package withdifferent solderswas compared.The qualitative results suggestthat SACQ has a significant advantage in the operational lifetime compared toSACR, InnoLot, and SAC305.