Combined effect of Bi and Ni elements on the mechanical properties of low-Ag Cu/Sn-0.7Ag-0.5Cu/Cu solder joints

Journal article (2020)

Authors

Xiangxia Kong North China Institute of Aerospace Engineering, Langfang
Junjun Zhai North China Institute of Aerospace Engineering, Langfang
Fenglian Sun Harbin University of Science and Technology
Yang Liu Harbin University of Science and Technology
H. Zhang Electronic Components, Technology and Materials - EEMCS , Harbin University of Science and Technology
Research Group
Electronic Components, Technology and Materials (EEMCS) (TU Delft)
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Published Date

01-04-2020

Language

English

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Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Microelectronics

Research Group

Electronic Components, Technology and Materials

Abstract

This study investigated the mechanical properties for two types of solder alloy: Sn-0.7Ag-0.5Cu-3.5Bi-0.05Ni (SAC0705BiNi) vs. Sn-0.7Ag-0.5Cu (SAC0705) by using nano-indentation. Two kinds of solder alloy balls with a diameter of 400 μm are soldered to Cu pads on FR-4 substrates, and then formed the ball grid array (BGA) micro solder joints of Cu/SAC0705BiNi/Cu and Cu/SAC0705/Cu. Meanwhile, the combined effect of Bi and Ni elements on the mechanical properties of the bulk of low-Ag Cu/SAC0705/Cu was discussed. Experimental results revealed that the indentation depth and area of the bulk of Cu/SAC0705BiNi/Cu solder joints were smaller than that of Cu/SAC0705/Cu under the same load and strain rate. It was observed that the indentation morphologies of the two kinds of the bulk of micro solder joints have piling-up phenomenon at lower strain rate. Under the maximum load of 20 mN and the strain rate of 2.5 × 10− 1 s−1, the indentation hardness of the bulk of Cu/SAC0705BiNi/Cu and Cu/SAC0705/Cu solder joints was 0.449 GPa and 0.200 GPa, respectively. And the strain hardening exponent was 0.302 and 0.159, respectively. Additionally, the stress-strain relationship was developed for the bulk of Cu/SAC0705BiNi/Cu and Cu/SAC0705/Cu micro solder joints. Compare with the bulk of the low-Ag Cu/SAC0705/Cu micro solder joints, the indentation hardness, indentation modulus and strain hardening exponent of the bulk of Cu/SAC0705BiNi/Cu achieve an improved by adding Bi and Ni elements.

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