TECHNET Archives

March 2003

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Graham Naisbitt <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 21 Mar 2003 10:50:23 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (83 lines)
> I have a question regarding a test for flux contamination on conformally
> coated boards.
>
> I know all about testing uncoated boards but was wondering if there are any
> tests for type UR coated boards?
>
> Does a temperature soak do any good at bringing problems to the surface?
>
> Does baking cause any remaining flux to become conductive?
>
> Does a humidity/temperature soak do any good?
>
> What were looking for is a parallel electrical path that might reduce the
> value of a small SMT resistor.
>
> Thanks in advance,
>
> KennyB

Kenny

I would assume that you have completed assemblies? If so, then I would also
presume that you have previously run some sort of accelerated life testing
with heat and humidity. If so, then repeat that test to see if you register
any failures. Do this powered-up.

If you have the chance, get some test coupons prepared that will allow over
mounting of components, and run process characterisation SIR tests. This
will measure the compatibility of your manufacturing process from the
stand-point of electro-chemical compatibility.

I have a draft spec that I can send you if you wish - please confirm.

One final pointer is that relating to adhesion of the coating.
Does it stick to component legs? Y/N
Does it stick to component bodies? Y/N
Does it stick to bare copper or tin/lead? Y/N
Does it stick to the substrate? Y/N

To my knowledge coatings are not intelligent - so cannot tell the difference
between these surfaces, so if it not sticking well to the substrate, then
there must be something else present that is preventing it from doing so.
This could be flux residues or some other "contaminant". Will this affect
circuit performance.....that's when you need to test......around and around
we go!!

--
Regards, Graham Naisbitt

[log in to unmask]

Mobile: +44 (0)79 6858 2121

NEW: Tech-Shot 05 :NEW
NEW: SoldaPro Wizard :NEW

Sales:
Concoat Limited
Millfield House, Fleet Road
Fleet GU51 3QF - UK

Phone: +44 (0)1252 813706
Fax: +44 (0)1252 813709

Works:
Concoat Limited
Alasan House, Albany Park
Canberley GU16 7PH - UK

Phone: +44 (0)1276 691100
Fax: +44 (0)1276 691227

---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------

ATOM RSS1 RSS2