Wire-Bonding Reliability of Electroless Ni/Pd/Au Plating - Influence of Electroless Pd Deposition Reaction
Authors: Yoshinori Ejiri, Takehisa Sakurai, Yoshinori Arayama, Yoshiaki Tsubomatsu, Kiyoshi Hasegawa Company: Hitachi Chemical Co., Ltd. Date Published: 9/22/2019
Abstract: The influence of the electroless deposition of Pd in electroless Ni-P/electroless Pd/immersion Au (ENEPIG) plating was investigated on the reliability of Au and Cu wire-bonding. Excellent Cu wire-bonding reliability was achieved under the optimized electroless Pd plating conditions. The pull strength of the Cu wire was insufficient when a corrosion layer was formed at the electroless Ni-P surface. The excellent Cu wire-bonding reliability was obtained in no corrosion at the Ni-P surface. The factors influencing corrosion of the electroless Ni-P surface were found to be additives in Pd plating bath, plating area of pad on the substrate, and liquid flow in the electroless Pd plating bath. In the electroless deposition of Pd on the electroless Ni-P film, the deposition processes involve a replacement reaction and ensuing reduction reaction. When the plating area is small or the liquid flow of the plating bath is fast, the replacement reaction time is long and the surface of the electroless Ni-P was corroded by the replacement reaction of Pd. We conclude that the optimized conditions of the electroless Pd deposition reaction to prevent corrosion of the Ni-P surface is important for obtaining excellent Cu wire-bonding reliability.
Electroless Ni-P/Pd/Au (ENEPIG), wirebonding reliability, Cu wire bonding