Evaluation of Copper and Gold Wire Bonds in PEM Devices

The shift from gold (Au) to copper (Cu) wire bonds used in PEMs (Plastic Encapsulated Microcircuits) has been gradual for the last few years. Many agencies and critics question the long-term robustness and reliability of Cu wire bonds; however, PEM manufacturers have been thoroughly evaluating and optimizing the Cu wire bond process over the last few years to produce highly reliable products. When the manufacturing process is optimized and closely controlled and monitored, Cu wire bonds can be a reliable and stronger alternate to Au wire bonds. This paper details a Cu wire bond study that specifically compares Cu wires against Au wire bonds following combined environmental stress/life test conditions. In this study, bond pull testing indicated good performance of both copper and gold wire bonds. The methods used in this analysis (Destructive Physical Analysis (DPA), wire pull testing and environmental testing) were effective techniques for evaluation of bond wire integrity, detection of manufacturing defects, and overall assessment of the copper and gold wire bond processes. Based on wire bond testing in this analysis, the reliability/integrity of optimally developed copper wire bonds appears to be superior or even stronger than gold wires in the same package type.