Carl,

Good luck!

No seriously though, this is a major research issue at the moment.

They need to consider testing the process in accordance with J-STD001B
Appendix B (was 001A appendix D) This way they can apply some form of
process validation. They should also please consider the reliability of the
product and process rather than making reference to an empirical
"cleanliness" spec.. No one can answer "How clean is clean?"

The only issue I have is that the quoted SIR test method MUST be modified in
light of recent research findings - notably through the UK NPL.  Note that
SIR testing is a QUANTITATIVE  not a QUALITATIVE  test method.

These changes involve reducing the test time interval to 20 minutes instead
of the present 24 hours. It also means testing at far more sensitive levels
and with lower bias voltage more in line with the end product. I will not
bore you with comment about the coupon design - but will happily review this
offline if you wish - and there MUST be component over mounting.

What essentially should occur is that you select the desired board, resist,
HASL or NiAg finish - the desired flux/paste/wire combo - any other chemical
process steps (underfills, globtops, adhesives etc) and the preferred
coating. Test at each process step and in total combination.

I have just been speaking with a high rel Class 3 customer who was tasked to
"eliminate cleaning in 12 months". That management decision was made
(apparently) in January 1998. It is now Sep 99, and they still can't do it!

However, I do have a solution but you should contact me offline if you want
more.

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: Carl Ray <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, September 02, 1999 3:13 PM
Subject: [TN] Advances in Cleaning of NO Cleans


> What advances have been made in the last few years to clean (DI Water) no
> clean flux residue from wave solder fluxes and solder pastes? I have a
> customer who is in Aerospace and they want use to look into no clean
process
> and still meet IPC 610 Class 3 specs for PCB cleanliness prior to
conformal
> coat. Any ideas would be helpful.
> Carl Ray
> Engineering  Supervisor
> 256-494-3247 Direct line
> 256-492-8997 ext. 272
> 256-494-0625 Fax
> [log in to unmask]
>
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