Dissolution in Service of the Copper Substrate of Solder Joints


June 20, 2019


Nihon Superior Co., Ltd, Department of Materials, Imperial College London


It is well known that during service the layer of Cu6Sn5 intermetallic at the interface between the solder and a Cu substrate grows but the usual concern has been that if this layer gets too thick it will be the brittleness of this intermetallic that will compromise the reliability of the joint, particularly in impact loading. There is another level of concern when the Cu-rich Cu3Sn phase starts to develop at the Cu6Sn5/Cu interface and an imbalance in the diffusion of atomic species, Sn and Cu, across that interface results in the formation at the Cu3Sn/Cu interface of Kirkendall voids, which can also compromise reliability in impact loading. However, when, as is the case in some microelectronics, the copper substrate is thin in relation to the volume of solder in the joint an overriding concern is that all of the Cu will be consumed by reaction with Sn to form these intermetallics.

This paper reports an investigation into the kinetics of the growth of the interfacial intermetallic, and the consequent reduction in the thickness of the Cu substrate in solder joints made with three alloys, Sn-3.0Ag-0.5Cu, Sn-0.7Cu-0.05Ni and Sn-1.5Bi-0.7Cu-0.05Ni....

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Company Information:

Nihon Superior Co., Ltd.

Nihon has been a leader in soldering and brazing since 1966. Nihon manufactures SMT solder joining materials e.g. lead-free solder (SN100C:Sn-Cu-Ni-Ge etc): solder paste, solder spheres, flux cored solder wire, solder bar, etc.

Osaka, Japan

Manufacturer of Assembly Material, Soldering

  • Phone 81-(0)6-6380-1121
  • Fax 81-(0)6-6380-1262

Nihon Superior Co., Ltd. website

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