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Developing a test method to characterise internal stress in tin coatings: phase 2.

Wickman, M; Fry, A T; Gohil, D D; Hunt, C (2005) Developing a test method to characterise internal stress in tin coatings: phase 2. NPL Report. DEPC-MPR 014

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This report highlights the progress made in Phase 2 of a Studio Project aimed at formulating a practical test method for measuring the internal stresses in the coatings of electronic components based on the XRD technique. The work is driven by the necessity to be able to assess the potential of whisker growth (generated from internal stresses) from new lead-free finishes for these components. Such finishes are being explored in the light of the forthcoming ban on the use of lead.
XRD measurement did show some correlation of measured compressive residual stress on coatings with whisker growth. Three coatings with high compressive residual stress also exhibited whiskering. However, the coatings evaluated were all at least twice as thick as penetration depth of the XRD measurement system, and the measured compressive residual stress values did not start to increase until after the formation of tin whiskers. However, the XRD method did provide some correlation between residual stress in the coatings and the extent of whisker growth.

Item Type: Report/Guide (NPL Report)
NPL Report No.: DEPC-MPR 014
Keywords: electronic assembly, tin whiskers, XRD
Subjects: Advanced Materials
Advanced Materials > Electronics Interconnection
Last Modified: 02 Feb 2018 13:16
URI: http://eprintspublications.npl.co.uk/id/eprint/3685

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