Evaluation of Copper and Gold Wire Bonds in PEM Devices

Abstract

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