Characterization of Flakes on Copper Bond Pad after Flux Cleaning Process

Abstract

In this study, flakes were analysed using several imaging tools including optical scope, SEM & TEM which were complemented with EDX analysis for elemental investigation of the flakes. Flakes formed on copper bond pad after flux cleaning process were characterized due to the fact that there were very few studies found in current literature. With in-depth analysis results interpretation of each method, a cross sectional schematic was proposed illustrating the interaction of flake on copper bond pad after flux cleaning process. Based on SEM & TEM analysis results, no evidence of IMC formation of the flake to copper bond pad was reported. From this flake characterization study, it was recommended to the assembly process experts to reduce or eliminate flakes formation on bond pad surface after flux cleaning process as accumulation of flakes on bond pad's surface would endanger robust wire bonding and also good adhesion quality and reliability assurance of semiconductor product in the long run.