Fellow Technetters,

We are going to be involved in a project this year looking at rates of Cu dissolution and IMC layer growth during soldering processes (including rework).
At this stage, I would like to ask the wider community whether anybody has or knows of "rules of thumb", or published data etc. which describes rates of dissolution and rates of IMC layer growth?

A little more specifically, based on a SAC305 alloy system, and using an Immersion Silver or OSP PCB finish, we are looking to develop our understanding of the following points:

1. IMC growth (microns) for SAC305 solder as a function of time exposure (seconds) above 230C
2. Cu dissolution (microns) for SAC305 solder as a function of time exposure (seconds) above 217C
3. Does anyone work to a defined critical threshold (in terms of max IMC thickness) above which PCB functional integrity is considered to be undermined?
4. Does anyone work to a defined critical threshold (in terms of min Cu thickness) below which PCB functional integrity is considered to be undermined?
5. Are there IPC or other standards covering these items?

I would be extremely grateful for your input, and would be very happy to share results of the experimental programme which we will undertake later this year.

Thanks and kind regards,

Stewart

Stewart McCracken
MCS Ltd.
Centre House
Midlothian Innovation Centre
Roslin
Midlothian
EH25 9RE
U.K.

t. +44 (0)131 440 9090
m. +44(0)7711 541735
e. [log in to unmask]
w. www.themcsgroup.co.uk


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