Di Maio, D; Hunt, C P; Willis, B (2008) Reduce copper dissolution in lead-free assembly. Measurement Good Practice Guide. 110

Text (Measurement Good Practice Guide No. 110) mgpg110.pdf - Published Version Download (5MB)

Abstract

During a successful soldering operation to a copper surface a small amount of copper is dissolved to form a reliable interconnection and is perfectly normal. During the soldering operation copper is dissolved by tin to form a tin/copper intermetallic and the amount dissolved is dependent on the soldering process, solder alloy, surfaces to be joined, temperature, time and solder flow rate. Using lead-free alloys requires higher soldering temperatures and potentially longer contact times, and hence the propensity for higher dissolution of copper.

A typical intermetallic produced with a tin/lead solder can range between 1-3µm. In the case of lead-free soldering process this thickness can increase above 5µm. The intermetallics are themselves soluble in solder, and hence potentially the overall copper dissolution rate is greater. Dissolution during lead-free soldering does not just impact copper pads on printed boards it can be a potential issue on thin copper wire, component terminations and hybrid metallisation. Examples of some typical problems previously experienced in industry are provided in this guide.

Item Type:	Report/Guide (Measurement Good Practice Guide)
Keywords:	Soldering, lead-free, copper dissolution
Subjects:	Advanced Materials Advanced Materials > Electronics Interconnection
Last Modified:	02 Feb 2018 13:15
URI:	http://eprintspublications.npl.co.uk/id/eprint/4307

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