Strength of Soldered Joints Formed under Microgravity Conditions |
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Authors: | B Thomas A Atkinson R J Dashwood |
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Affiliation: | (1) Department of Materials, Imperial College, London, SW7 2AZ, United Kingdom |
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Abstract: | Experiments have been carried out to compare the mechanical strength of joints soldered with Sn-Ag-Cu under different gravitational
conditions. Joints soldered under microgravity (produced during a parabolic flight) have lower strength (by 32% in this case)
than similar joints formed under normal gravity. Electron microscopy has shown that this is due to a larger volume of residual
porosity (14%) in the joints formed in microgravity compared with <1% for joints formed in normal gravity. The residual porosity
in joints formed in microgravity is mainly within the bulk of the solder, with some microporosity in the Cu6Sn5 intermetallic layer near the copper interfaces. The porosity not only weakens the joint, but also biases the failure path
away from the intermetallic layer and into the bulk of the solder. These observations show that gravitational buoyancy is
important for the expulsion of flux and flux residues from soldered joints. |
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Keywords: | Solder strength microgravity |
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