Charlie
Its great to have you back.
For the benefit of others, I have already sent Charlie some info that is not
suitable for the TechNet, but to ensure fair-play, I thought my other
observations should be placed through the right channel.
As I was saying, this is quite a task you set yourself given the variables
that abound. The most important issue is the nature of the end product. Is
it safety critical, High Rel or to be more correct, Class 1, 2 or 3 as
defined in the IPC-CC-830 and others?
If the product really matters, then you would be well advised to run SIR
testing using the most up to date techniques. Dr Chris Hunt of the British
NPL has published data including, most particularly, low voltage testing
that has yielded some very interesting results. If anyone else wants copies
and Chris hasn't got his TechNet ears on, then let me know and I will
forward copies.
As Brian has already stated, the process window becomes considerably smaller
and your incoming inspection increases. Maybe you have to consider
pre-tinning components if your volumes are low.
The rigorous evaluation process you refer to I guess is covered by Appendix
B of J-STD001B ( if I have my revision references correct Jack?) If so, my
information indicates that very few have actually tested this way so maybe
your wheel will be radical?
I would also refer you to my paper that appeared in Circuits Assembly
journal, Sept 1995 entitled Chemicals v Electronics. It will help to
appreciate what is involved.
As we have completed some significant work in this subject, but it will be
spamming in the worst sense, maybe interested parties can call me off line
for more.
As to water soluble processing, I would suggest that modern CSP's frankly
demand the use of saponifier additions to the wash, as compared to a pure
OA. This has been due to the extremely low stand-offs these devices present
and their large surface area - maybe that should be under-surface area!
Pure OA in-line cleaning will be around 20% to 30% less expensive than a
"saponified" system. Can we call them "Water Soluble" and "Water Washable"?
BTW, Charlie don't forget to use test coupons that are properly
representative of your actual production boards, that includes the solder
resist and the surface finish.
Hope this helps
Regards,
Graham Naisbitt
[log in to unmask]
WEB: http://www.concoat.co.uk
CONCOAT Ltd
Alasan House, Albany Park
CAMBERLEY GU15 2PL UK
Tel: +44 (0) 1276 691100 Fax: +44 (0) 1276 691227
----- Original Message -----
From: Charles Barker <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, February 21, 2000 2:35 PM
Subject: [TN] THANKS and no clean info request
> Hello Technetters;
>
> As Steve Gregory let slip last week, I am back on the job. I'm somewhat
> inundated with catching up, so I had not checked back in on TechNet right
away.
>
> MANY THANKS for all the prayers and good wishes. They were felt and very
much
> appreciated by both my wife and me. I still have a good bit or soreness
from the
> trauma of the surgery, but in general, I feel very good.
>
> Now back to the work/no clean thing:
>
> I am asking a BIGGG favor!
>
> I need to take a serious look at switching our process from a water
soluble flux
> soldering operation to a no clean one. Normally, I would put several cored
wire
> solders, liquid fluxes and solder pastes through a rigorous evaluation
process.
> That could be considered re-inventing the wheel, since many of you have
probably
> already done that.
>
> If any of you have done this and could share the results (OFF-LINE, of
course),
> I would be greatly obliged.
>
> I would like to know which brands, which model numbers, which alloys and
under
> what conditions they were tested, as well, of course, as the results.
>
> THANKS A BUNCH!!!
>
> Charlie B.
> [log in to unmask]
>
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