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News Release from: National Physical Laboratory
Edited by the Electronicstalk Editorial Team on 13 November 2006

Project to investigate copper dissolution

Collaborative industry project investigates measurements of copper dissolution in lead-free solder alloys

The UK National Physical Laboratory is launching a new collaborative industry project on measurements of copper dissolution in lead-free solder alloys. One of the problems associated with the switch from tin-lead to lead-free is the increased tendency of copper dissolution in molten solders.

This has been confirmed by Martin Morrell, Managing Director of Artetch Circuits in Littlehampton, UK who has stated: 'It seems very timely to conduct this investigation'.

'We have seen a marked increase in customers finding issues related to copper dissolution since they moved over to lead-free assembly'.

'I think the findings of this project are urgently needed as we tend only to see the catastrophic effects of copper loss'.

'There must be a product out there that has issues that have gone unnoticed'.

'We have already pledged the support of Artetch Circuits to this study'.

PCB land and plated through holes can be eroded or dissolved away in the presence of molten solder rendering the PCB nonfunctional.

Significant dissolution can occur with the use of certain new Sn-rich alloys and is further exacerbated by the higher process temperatures.

Clearly this phenomenon represents a serious risk to circuit reliability.

There is a clear need to determine the dissolution rate of copper pads with lead-free solders under various conditions.

Hence a well defined and efficient technique is required to compare the performance of the new alloys regarding their tendency to dissolve copper when they are in the molten state.

This NPL project aims to bring together interested parties who need to deal with the new lead-free alloys in situations where the copper dissolution is a concern.

The project can potentially include various lead-free alloys as well as different temperatures and soldering technologies eg wave, selective and reflow soldering, in order to understand what happens in real industrial processes.

A measuring method will be developed as part of the project and will be used to test the alloys.

Partners will have the chance to influence directly the project by making it relevant to their production scenario, design, equipment, alloys, PCB finish and so on and they will be able to access experimental results at all times, before the end of the project.

The scope of the project includes the development of a monitoring technique to quantify the rate of copper loss due to immersion in a molten metal under static and dynamic conditions.

It also involves the investigation of Cu dissolution with a range of solder alloys, PCB styles and temperatures.

There will be a best practice guide that includes a test method, for minimising PCB copper dissolution.

The partners for this studio project are expected to be drawn from solder alloy manufacturers, wave soldering manufacturers and end users wishing to get a better understanding of the problem.

An initial meeting for this project has been announced for 7th December 2006 at The Oxfordshire Conference Centre in Thame, Oxfordshire.

This meeting is an opportunity to explore what the project might achieve and who are the likely partners.

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