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Microstructure evolution and growth behavior of Cu/SAC105/Cu joints soldered by thermo-compression bonding

Mengjiao Guo (Harbin University of Science and Technology, Harbin, Heilongjiang, China)
F. Sun (Harbin University of Science and Technology, Harbin, Heilongjiang, China)
Zuozhu Yin (Harbin University of Science and Technology, Harbin, Heilongjiang, China)

Soldering & Surface Mount Technology

ISSN: 0954-0911

Article publication date: 13 May 2019

Issue publication date: 21 August 2019

Abstract

Purpose

This paper used a novel technique, which is thermo-compression bonding, and Sn-1.0Ag-0.5Cu solder to form a full intermetallic compound (IMC) Cu3Sn joints (Cu/Cu3Sn/Cu joints). The purpose of the study is to form high-melting-point IMC joints for high-temperature power electronics applications. The study also investigated the effect of temperature gradient on the microstructure evolution and the growth behavior of IMCs.

Design/methodology/approach

In this paper, the thermo-compression bonding technique was used to form full Cu3Sn joints.

Findings

Experimental results indicated that full Cu/Cu3Sn/Cu solder joints with the thickness of about 5-6 µm are formed in a short time of 9.9 s and under a low pressure of 0.016 MPa at 450°C by thermo-compression bonding technique. During the bonding process, Cu6Sn5 grew with common scallop-like shape at Cu/SAC105 interfaces, which was followed by the growth of Cu3Sn with planar-like shape between Cu/Cu6Sn5 interfaces. Meanwhile, the morphology of Cu3Sn transformed from a planar-like shape to wave-like shape until full IMCs solder joints were eventually formed during thermo-compression bonding process. Asymmetrical growth behavior of the interfacial IMCs was also clearly observed at both ends of the Cu/SAC105 (Sn-1.0Ag-0.5Cu)/Cu solder joints. Detailed reasons for the asymmetrical growth behavior of the interfacial IMCs during thermo-compression bonding process are given. The compound of Ag element causes a reduction in Cu dissolution rate from the IMC into the solder solution at the hot end, inhibiting the growth of IMCs at the cold end.

Originality/value

This study used the thermo-compression bonding technique and Sn-1.0Ag-0.5Cu to form full Cu3Sn joints.

Keywords

Acknowledgements

The work described in the paper was partially supported by the National High Technology Research and Development Program of China (863 Program) (No. 2015AA033304) and partially supported by the National Natural Science Foundation of China (No. 51174069).

Citation

Guo, M., Sun, F. and Yin, Z. (2019), "Microstructure evolution and growth behavior of Cu/SAC105/Cu joints soldered by thermo-compression bonding", Soldering & Surface Mount Technology, Vol. 31 No. 4, pp. 227-232. https://doi.org/10.1108/SSMT-08-2018-0025

Publisher

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Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited