Bond reliability under humid environment for Pd coated Cu and Ag alloy wire bonding

Due to the high cost of gold wire, copper wire and silver wire become the mainstream of wire materials in electronic package industry. Recently, taking the reliability of the IC components into consideration, Pd-coated copper wire and Ag alloy wire are the most popular wires using in wire bonding. However the study of reliability about Ag alloy wire bonding is very rare. The differences between Pd-coated copper wire and Ag alloy wire have not been studied systematically. In this paper, bond reliability under humid environment for Pd-coated Cu and Ag alloy wire bonding were studied. Shear tests were used to evaluate the quality and robustness of joints. The reliability test under humid environment used in this paper is unbiased-highly-accelerated temperature and humidity stress test (u-HAST). U-HAST is conducted at 130 degrees C and 85% relative humidity. The bond-pad interface was analyzed by scanning electron microscopy (SEM) and electron-dispersive microscopy (EDS). The bond reliability of Cu wire under humid environment is better than Ag alloy wires.