Hi,
What I found on IPC Standards, just few paragraphs on
IPC-HDBK-001,(Dec-2000)
4.1.7.2 Intermetallic Layers
4.1.7.2.1 Intermetallic Growth Rates
As Dave says, plenty of information (Papers) are available about Copper
Dissolution phenomena and IMC behaviours at different temperatures and
Alloys. With Reflow,Wave and Rework Processes.
Also on web, if lucky, by googling you can find plenty of helpful infos.
Regards
Gabriele
-----Messaggio originale-----
Da: TechNet [mailto:[log in to unmask]] Per conto di David D. Hillman
Inviato: giovedì 2 febbraio 2012 23.02
A: [log in to unmask]
Oggetto: Re: [TN] Cu - dissolution and IMC growth rate
Hi Stewart - I would recommend that before you launch into a SAC305 copper
dissolution project that you investigate the published data as there has
been a tremendous volume of work in that area already. Sources in my
references include:
- a number of papers presented in the IPC APEX and SMTAI conferences in
the 2005-2012 time frame
- NPL (Dr. Chris Hunt and team) did a great study on dissolution rate
- Craig Hamilton and the folks from Celestica have some great publications
on copper dissolution
- the NASA DoD report has copper dissolution data for SAC305 and SN100C
solder alloys (the report is on the web)
Your question on "how thick can IMC get before we have cracking issues" is
a good question but the reality is that the number of IMC cracking issues
published can be counted on one hand. Using industry typical soldering
process, either tin/lead or leadfree solder alloys, you need to severely
abuse the process parameters to get into those types of situations.
Published data by Thwaites and Klein Wassink covers the IMC topic. There
is no IPC standards on copper dissolution or IMC thickness that I am aware
of.
Good luck with the effort.
Dave Hillman
Rockwell Collins
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Stewart McCracken <[log in to unmask]>
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02/02/2012 04:11 AM
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Subject
[TN] Cu - dissolution and IMC growth rate
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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