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Microstructural evolution of the intermetallic compounds in the high density solder interconnects with reduced stand‐off heights

Microstructural evolution of the intermetallic compounds in the high density solder interconnects... Purpose – This paper aims to investigate the microstructural evolution rules of the intermetallic compound (IMC) layers in high‐density solder interconnects with reduced stand‐off heights (SOH). Design/methodology/approach – Cu/Sn/Cu solder joints with 100, 50, 20 and 10 μm SOH were prepared by the same reflow process and isothermally aged at 150°C. The IMC microstructural evolution was observed using scanning electron microscopy. Findings – The whole IMC layer (Cu 3 Sn + Cu 6 Sn 5 ) grew faster in the solder joints with lower SOH because of the thinner IMC layer before aging. Also, the IMC proportion increased more rapidly in solder joints with the lower SOH. In all solder joints with different SOH, the growth rates of the Cu 3 Sn (&epsis;) layers were similar, and slowed down with increasing aging time. The Cu 6 Sn 5 (η) was consumed by the Cu 3 Sn (&epsis;) growth at the beginning of the aging stage; while it turned to thickening after a period of aging. Finally, the Cu 6 Sn 5 thickness was similar in all the solder joints. It is inferred that the thickness ratio of Cu 3 Sn to Cu 6 Sn 5 would maintain a dynamic balance in the subsequent aging. Based on the diffusion flux ratio of Cu to Sn at the &epsis;/η interface, a model has been established to explain the microstructural evolution of IMC layers in high‐density solder interconnects with reduced SOH. In the model, interfacial reactions are mainly supposed to occur at the &epsis;/η interface. Originality/value – The findings provide electronic packaging reliability engineers with an insight into IMC microstructural evolution in high‐density solder interconnects with reduced SOH. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Soldering & Surface Mount Technology Emerald Publishing

Microstructural evolution of the intermetallic compounds in the high density solder interconnects with reduced stand‐off heights

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Publisher
Emerald Publishing
Copyright
Copyright © 2011 Emerald Group Publishing Limited. All rights reserved.
ISSN
0954-0911
DOI
10.1108/09540911111169075
Publisher site
See Article on Publisher Site

Abstract

Purpose – This paper aims to investigate the microstructural evolution rules of the intermetallic compound (IMC) layers in high‐density solder interconnects with reduced stand‐off heights (SOH). Design/methodology/approach – Cu/Sn/Cu solder joints with 100, 50, 20 and 10 μm SOH were prepared by the same reflow process and isothermally aged at 150°C. The IMC microstructural evolution was observed using scanning electron microscopy. Findings – The whole IMC layer (Cu 3 Sn + Cu 6 Sn 5 ) grew faster in the solder joints with lower SOH because of the thinner IMC layer before aging. Also, the IMC proportion increased more rapidly in solder joints with the lower SOH. In all solder joints with different SOH, the growth rates of the Cu 3 Sn (&epsis;) layers were similar, and slowed down with increasing aging time. The Cu 6 Sn 5 (η) was consumed by the Cu 3 Sn (&epsis;) growth at the beginning of the aging stage; while it turned to thickening after a period of aging. Finally, the Cu 6 Sn 5 thickness was similar in all the solder joints. It is inferred that the thickness ratio of Cu 3 Sn to Cu 6 Sn 5 would maintain a dynamic balance in the subsequent aging. Based on the diffusion flux ratio of Cu to Sn at the &epsis;/η interface, a model has been established to explain the microstructural evolution of IMC layers in high‐density solder interconnects with reduced SOH. In the model, interfacial reactions are mainly supposed to occur at the &epsis;/η interface. Originality/value – The findings provide electronic packaging reliability engineers with an insight into IMC microstructural evolution in high‐density solder interconnects with reduced SOH.

Journal

Soldering & Surface Mount TechnologyEmerald Publishing

Published: Sep 20, 2011

Keywords: Soldering; Joining processes; Metals

References