Understanding materials compatibility issues in electronics packaging

This paper presents a method, which helps to understand and control interactions between dissimilar materials in electronics packaging assemblies. The method consisting of thermodynamic and kinetic modeling combined with detailed microstructural analysis is introduced first. The method will then be demonstrated using three examples. First one is taken from an IC metallization level, and explains why and how TaC diffusion barrier reacts with Si. The second example discusses the impact of Cu on the microstructural evolution and degradation of Au-Al bonds. Finally, the third example deals with solder alloy reactions with Ni/Au pad finishes at a circuit board. The results presented explain the redeposition of AuSn₄ phase at the pad interface when SnPbAg or SnAg solders are used.