Interfacial microstructures and mechanical properties of molten Sn reacting with Ni–xP films

• Published in: Surface & coatings technology Vol. 303; pp. 112 - 118
• Main Authors: Hsieh, W.Z., Rahman, M.A., Yang, T.H., Kuo, T.T., Ho, C.E.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2016
• Subjects: Electroless Ni–P; IMC spalling; Ni2SnP; Ni3Sn4; Ni–P depletion; P content effect; Ni3Sn4; IMC spalling; Ni–P depletion; Electroless Ni–P; P content effect; Ni2SnP
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2016.03.025

Deposition of Ni via autocatalytic (electroless) plating inevitably contains a specific amount of P (usually 6–10wt.%) due to the use of hypophosphite reducing agent in the autocatalytic reaction. The focus of this study is to investigate the effect of P content on the solderability between pure Sn and a Au/Ni–xP/Cu pad, where x was 6wt.% (10.8at.%), 8wt.% (14.1at.%), and 10wt.% (17.4at.%). We found that the intermetallic compound (IMC) species formed at the interface between solder and Ni–xP and the Ni–xP pad's depletion both strongly depended on x. The P-dependent Ni–xP depletion was ascribed to various IMC formations. The dependence of the IMC species on the P content can be rationalized using a Ni–P–Sn isotherm. Additionally, high-speed ball shear test showed that the difference in the interfacial microstructures arising from various x values might significantly affect the mechanical properties of solder joints. These findings revealed that the P content in the Ni–P platings is a very important factor of solderability. •P content effect on the solderability•Strong dependences of Ni(P) depletion and IMC growth on the P content•IMC massive spallation from the interface with increasing the P content•IMC spallation enhanced the mechanical properties of joint interface.•Failure mode translated from brittle to ductile with increasing the P content