Tom,

I would commend you to review this with one of the failure analysis labs
such as CSL, Robisan or Trace etc..

White residues as described could be flux in the form of collophane remains,
tin or lead salts, or simply a reaction between your LPI Mask and the flux.
It could also come from excessive cleaning or dirty rinse water.

Ideally, you need to run an Ion Chromatography test which will define what
is on the surface. Then establish whether it will degrade the circuit
reliability or is it purely a question of aesthetics? If it is the latter,
put a coating over it - but only AFTER you know what it is! The coating will
most likely, "hide" the ugly appearance. Please DO NOT simply coat it to
hide what could be a major reliability issue.

Regards, Graham Naisbitt

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Concoat Ltd             Phone: +44 1276 691100
Alasan House          Fax:      +44 1276 691227
Albany Park
CAMBERLEY
GU15 2PL UK

Any opinions expressed are those of this employer.
-----Original Message-----
From: fawnec <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 27 January 1999 16:18
Subject: [TN] #2 White layer on PCB after wave solder


>Hello Netters,
>
>I forgot to mention Soldermask  is LPI, I am contacting vendor on whose
>brand?
>
>Thanks again!
>
>Tom B
>
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