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Research Papers

Effect of Solder Joint Thickness on Intermetallic Compound Growth Rate of Cu/Sn/Cu Solder Joints During Thermal Aging

[+] Author and Article Information
Yan Zhu

School of Material Science and Engineering,
Harbin University of Science and Technology,
4# Linyuan Road,
Harbin 150040, China;
School of Material Science and Engineering,
Heilongjiang University of
Science and Technology,
2468# Puyuan Road,
Harbin 150022, China

Fenglian Sun

School of Material Science and Engineering,
Harbin University of Science and Technology,
4# Linyuan Road,
Harbin 150040, China
e-mail: Sunfengl@hrbust.edu.cn

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received June 5, 2016; final manuscript received August 13, 2016; published online October 10, 2016. Assoc. Editor: Toru Ikeda.

J. Electron. Packag 138(4), 041005 (Oct 10, 2016) (5 pages) Paper No: EP-16-1069; doi: 10.1115/1.4034819 History: Received June 05, 2016; Revised August 13, 2016

The sandwich structure Cu/Sn/Cu solder joints with different thicknesses of the solder layers (δ) are fabricated using a reflow solder method. The microstructure and composition of the solder joints are observed and analyzed by scanning electron microscopy (SEM). Results show that the thickness of intermetallic compound (IMC) and Cu concentration in the solder layers increase with the decrease of δ after reflow. During thermal aging, the thickness of IMC does not increase according to the parabolic rule with the increase of aging time; the solder joint thickness affects markedly the growth rate of IMC layer. At the beginning of thermal aging, the growth rate of IMC in the thinner solder joints (δ ≤ 25 μm) is higher than that in the thicker ones (δ ≥ 30 μm). The growth rate of IMC (δ ≤ 25 μm) decreases in the thinner solder joints, while increases in the thicker solder joints (δ ≥ 40 μm) and is nearly invariable when the δ equals to 30 μm with aging time extending. The growth rate of IMC increases first and then decreases after reaching a peak value with the increase of δ in the later stage during aging. The main control element for IMC growth transfers from Cu to Sn with the reduction of size.

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References

Figures

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Fig. 1

The schematic diagram of Cu/Sn/Cu solder joint

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Fig. 2

Cross section SEM images of Cu/Sn/Cu solder joint after reflow

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Fig. 3

Cu–Sn phase diagram [18]

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Fig. 4

The thickness of Cu6Sn5 layer and Cu concentration with various δ

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Fig. 5

Cross section SEM images of Cu/Sn/Cu solder joint after aging at 160 °C for 600 h: (a) δ = 10 μm, (b) δ = 30 μm, and (c) δ = 50 μm

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Fig. 6

The relationship between the average thickness of IMC layers and aging time at 160 °C

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Fig. 7

The changes of Cu concentration in front of Cu6Sn5/solder interface during aging at 160 °C: (a) aged for 0 h, (b) aged for 192 h, (c) aged for 384 h, and (d) aged for 600 h

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Fig. 8

The changes of relative consumption of Sn solder during thermal aging at 160 °C

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Fig. 9

Growth rate of IMC layer during thermal aging

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Fig. 10

Growth rate of IMC layer versus the δ

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