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

Xiangxia Kong, Junjun Zhai, Fenglian Sun, Yang Liu, Hao Zhang

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)

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.

Original languageEnglish
Article number113618
Number of pages8
JournalMicroelectronics Reliability
Volume107
DOIs
Publication statusPublished - 1 Apr 2020

Keywords

  • Indentation hardness
  • Indentation modulus
  • Micro solder joints
  • Nano-indentation
  • Strain hardening exponent
  • Strain rate

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