Sub-micrometer warpage measurement setups for the verification of material models of soft solder die attaches by inverse modeling

Abstract

In contrast to the use of lead free solders in most electronic applications, replacement of high-lead materials has not yet been possible for die attach in power electronics. Accordingly, there is still some need for creep data input in related simulations. Several creep models of high-lead soft solder die attach materials were published, which were extracted from macro-scale material samples. However, as it is generally known for soft solders, their creep behavior depends strongly on microstructure and a creep description close to the application is to be preferred. In order to assess the validity of the creep models at micro-scale in a use-scenario, this work uses two recently developed experimental setups with sub-μm warpage measurement capability. The warpage of three-layered samples is measured over temperature and simulated using four different published creep models. The solder models are able to reproduce the measured change in warpage direction with certain accuracy, but also show deviations from the measured behavior of the test samples which requires further investigation.