Hunt, C P; Wickham, M (2009) Evaluation of the ability of conformal coatings to inhibit tin whiskering. NPL Report. MAT 36

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Abstract

A technique using specially electroplated, interdigitated discs, developed at the National Physical Laboratory has been used to determine the relative ability of conformal coatings to mitigate against Sn whisker growth. A range of acrylic, polyurethane, silicone and urethane acrylate coatings have been evaluated and all were shown to inhibit the growth of whiskers compared to uncoated control samples over a 150 day period. All the control samples without conformal coatings, developed whiskers of >250mm in length, sufficient to cause electrical shorts between the discs within 14 days.

Where coating coverage was defect-free and of sufficient thickness, only a limited number of coatings (two acrylic coatings and a urethane acrylate coating) were found to have whiskers penetrating through the coating. Whiskers penetrating out from under coatings were found extensively in areas where the coatings were thinner, or where there were other coverage issues. All the coatings evaluated except two of the polyurethane coatings exhibited whisker growth from under coated plates in the region of sharp corners. Where both plates of the samples were coated, five of the coatings evaluated did not exhibit electrical shorts at any time during the 150 days of testing. These were one acrylic, two polyurethane and two silicone coatings.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	MAT 36
Keywords:	tin whisker, lead-free, conformal coating, mitigation
Subjects:	Advanced Materials Advanced Materials > Electronics Interconnection
Last Modified:	02 Feb 2018 13:15
URI:	http://eprintspublications.npl.co.uk/id/eprint/4562

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