Journal of SMT Article

Influence of Electroless Pd Plating Film Thickness on Solder Joint Relibility of ENEPIG

Authors: Yoshinori Ejiri, Takehisa Sakurai, Yoshinori Arayama, Yoshiaki Tsubomatsu, Kiyoshi Hasegawa
Company: Hitachi Chemical Co., Ltd.
Date Published: 1/30/2018   Volume: 31-1

Abstract: We investigated the influence of Pd film thickness in electroless nickel/electroless palladium/immersion gold (ENEPIG) plating on the intermetallic compound (IMC) growth and the effects on solder joint failure mechanisms by shear testing to qualitatively determine solder joint reliability (SJR). SAC305 solder balls were attached onto printed circuit board (PCB) and were then subjected up to seven reflows with peak temperatures at 230°C, 250°C, and 260°C. Two IMCs, (Cu, Ni, Pd)3Sn and (Cu, Ni, Pd)Sn4, were formed during the diffusion of Pd into the solder and (Cu, Ni, Pd)6Sn5 IMCs on Ni interface with two shapes depending on thickness of Pd plating. For thin Pd plating (0.1–0.2 µm), thin layers of (Cu, Ni, Pd)Sn4 IMCs were formed during the diffusion of Pd into the solder, and the shape of (Cu, Ni, Pd)6Sn5 IMCs was dendritic. Whereas for the thick Pd plating films (0.5–0.8 µm), thick (Cu, Ni, Pd)Sn4 IMCs were formed during the diffusion of Pd into the solder, and the shape of (Cu, Ni, Pd)6Sn5 IMCs was planar. We concluded that the thickness of (Cu, Ni, Pd)Sn4 IMCs affected the shape of (Cu, Ni, Pd)6Sn5 and the SJR. The excellent SRJ is caused by the dendritic shape of (Cu, Ni, Pd)6Sn5 IMCs and the poor SRJ is caused by the planar shape of (Cu, Ni, Pd)6Sn5 IMCs.

Keywords: 

Electroless Ni/Pd/Au (ENEPIG), Solder joint reliability (SJR), Intermetallic compounds (IMCs), Reflow cycles, High-speed solder ball shear test



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