An innovative approach to accelerate high temperature operating endurance test for automotive electronic control units

Abstract

Interconnect technologies play a vital role to provide the necessary electrical, mechanical and thermal interconnections in electronic assemblies. They are considered as one of the most critical factors governing the lifetime and reliability of the whole assembly1,2. This paper represents a new approach with a goal to accelerate the high temperature aging of electronic modules. The standard aging test is exposure of the assemblies to elevated temperatures for determined durations in order to simulate their lifetime in the field. It has to be mentioned that this qualification process activates failure mechanisms which are diffusion controlled and thermally activated. In this research, electronic assemblies have been subjected to temperature shocks as a pre-treatment before the ordinary high temperature aging under constant elevated temperatures. The main aim of this pre-treatment is to induce plastic deformation in the material due to coefficient of thermal expansion (CTE) mismatch of different materials. The stored energy is the driving force for recrystallization producing new strain-free and small in size grains. Consequently, the number of grain boundaries will increase which will make the grain boundary diffusion mechanism more dominant than the bulk diffusion mechanism. This process enhances and accelerates the overall diffusion process and consequently the diffusion controlled failure mechanisms under exposure to constant elevated temperatures. This will help in accelerating the electronic assemblies qualification process. A design of experiment was developed in order to better understand the effect of thermal aging conditions on interconnect technologies in the form of intermetallic compounds growth. Different geometries have been used including multi layer ceramic capacitors (MLCC) and integrated circuits (IC). Failure analysis and microscopic investigations have followed the different aging conditions. A group of assemblies were exposed to temperature shocks of different number of cycles. Another experiment has been carried out for thermal aging of electronic assemblies under constant elevated temperatures; repeated for different durations. A correlation between the aging hours and the IMCs growth is analyzed. A third experiment has been implemented with another group of assemblies that were subjected to sequential temperature shock and high temperature aging, deriving a conclusion.