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)
Notes:	NPL made every effort to ensure all information contained in this Good Practice Guide was correct at time of publication. NPL is not responsible for any errors, omissions or obsolescence, and does not accept any liability arising from the use of these Good Practice Guides.
Keywords:	Soldering, lead-free, copper dissolution
Subjects:	Advanced Materials Advanced Materials > Electronics Interconnection
Last Modified:	23 Feb 2026 09:02
URI:	https://eprintspublications.npl.co.uk/id/eprint/4307