Impact of Cryogenic Temperature Environment on Single Solder Joint Mechanical Shear Stability
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https://doi.org/10.1007/s11664-020-08456-5 Ó 2020 The Minerals, Metals & Materials Society
TMS2020 MICROELECTRONIC PACKAGING, INTERCONNECT, AND PB-FREE SOLDER
Impact of Cryogenic Temperature Environment on Single Solder Joint Mechanical Shear Stability ANDE KITAMURA,1 TIMOTHY MATTHEWS,1 RUBEN CONTRERAS,1 DAVID ROUTLEDGE,2 and TAE-KYU LEE 1,3 1.—Department of Mechanical and Materials Engineering, Portland State University, Portland, OR, USA. 2.—Nordson Dage, Aylesbury, UK. 3.—e-mail: [email protected]
Although the performance of electronic devices in extreme temperature ranges has been extensively studied, the interconnections, which are still mainly Snbased materials, require thorough observation and assessment to support the mechanical and electrical stability in subzero to cryogenic temperature environments. An in-depth assessment is required because of the nature of Sn, which has a ductile-to-brittle transition temperature of approximately 60°C. Sn-1Ag-0.5Cu (wt.%) (SAC105) solder joints were subjected to shear testing at room temperature and at 196°C at liquid nitrogen temperature. Isothermal aging at 150°C for 50–500 h prior to cryogenic temperature testing indicated further degradation under certain aging conditions. The study presented here investigates the maximum shear strength variations for SAC105 single solder joints with NiAu and Cu-organic solderability preservative (Cu-OSP) pad surface finishes using a multibond tester with a 10-lm shear height and 100lm/s shear speed. An increase in the maximum shear strength was observed at liquid nitrogen temperature compared to that at room temperature due to an increase in the yield strength and loss in ductility of the solder material in response to the low-temperature environment. The maximum shear strength decreased with isothermal aging due to the crack propagation path variation. Fracture locations were identified between the Ni pad and the (Cu, Ni)6Sn5 interface for the NiAu surface finish components, and Cu-OSP surface finish solder joints revealed transgranular crack through the Cu6Sn5 and crack propagation between the Cu6Sn5 and the solder interface. The shift in the full fracture location is discussed in association with electron backscatter diffraction (EBSD) analysis on partially sheared solder joints at room temperature and at 196°C. Key words: Cryogenic temperature, solder, solder shear, microstructure, interconnect
INTRODUCTION Recent deep-space exploration, quantum computing, and extreme environmental conditions have pushed the limits of interconnect reliability
(Received June 17, 2020; accepted August 27, 2020)
challenges in electronic devices to cryogenic temperatures. Aerospace exploration has the potential to encounter planets and moons with cryogenic temperatures of approximately 220°C, while quantum computing requires an environment of cryogenic temperatures of approximately 270°C.1–3 Even though the solder joints and interconnects might not be exposed directly to these temperatures, the mechanical and electrical stability at subzero te
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