Cu-Al wire bonds under low bias humidity testing presented an idea of the failure mechanism of Cu-Al wire bonds under voltage bias \[Chiu 2014\]. Basically, electrical bias affects Cu-Al wire bonds in two different ways. The first method is to speed up the transfer of contaminants towards the bond pad interface. Epoxy molding compounds are known to contain certain levels of contaminants such as chlorine. These pollutants are first combined with large organic compounds known as functional groups \[Soestbergen 2007\]. Due to the decomposition of the epoxy molding compound (EMC) at high temperature or high humidity aging, chlorine ions are gradually released from the functional groups and move freely in the EMC.  Under voltage bias, negatively charged chloride ions are forced to move to the bond pad interface where the Cu-Al IMC is attacked by chlorine. The full chlorine attack IMC process is a fine galvanic corrosion process described in previous studies \[Lall 2015, Lall 2016\]. The corrosion rate of wire bonds has proven to be directly related to the level of chlorine concentration near the Cu-Al wire bonds. The second method is to directly change the electrochemical potential distribution across the corrosion front of the Cu-Al wire bond, accelerating the corrosion process and leading to premature failure of the Cu-Al wire bond.  To study how high voltage bias affects the reliability performance of Cu-Al wire bonds, the paper first presents an experimental setup to run high voltage bias tests on Cu-Al wires bond interconnect using oscilloscope and LTspice. Subsequently, the migration-diffusion cell experiment is proposed to quantify effect of voltage bias on chlorine transport in EMC. Butler-Bolmer-Based Corrosion Simulation is used to quantify the effect of voltage bias on the corrosion rate of Cu-Al wire bonds based on Electrochemical Polarization Test Results for Cu-Al IMC


Reliability Assessment of Cu-Al Wb Under High Temperature and High Voltage Bias Application

Division / Sponsors: 
Electronic & Photonic Packaging Division (EPPD)

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2020/volume/84041

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