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March 2000

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 1 Mar 2000 14:12:45 +0200
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Richard

Guess chatting with a baseball bat is needed, although I don't understand why the
problem has appeared so long after manufacture.

Brian

Richard Tilbrook wrote:

> Hi Technetters, I'm back again, two months (has it been that long???) into Y2K.
>
> My problem is on a subject about which I know little, and I write to you on behalf
> of a friend upon whose project the following has manifested itself.
>
> We have a line upon which we manufacture simple through-hole PCBs. We are using
> externally supplied multi-layer boards with nothing high-density or high tech about
> them. They come in looking nice and well tinned. For about six months they have
> been flowing OK, with only one problem - a large ground plane caused a few problems
> in one area for a little while and we had to re-adjust the profile on the flow
> machine (this is, I am sure, irrelevent to the problem). We like to manufacture to
> a very high standard, so it was concerning when some PCBs recently exhibited bare
> copper in various places. We use a low tack professional masking tape to mask two
> planes on the board during conformal coat - on removal, the tinning came away,
> exposing bare copper! Even more seriously, at many places solder had not fully
> wicked to the top of the through-hole, meaning very suspect joints. In various
> places, solder had wicked away from pads, again exposing copper.
>
> Is it possible that we are doing something wrong without realising, or shoud we be
> chatting to our board suppliers?
> What do you folks feel is the problem, and what do you recommend we look at?
>
> Regards,
>
> Richard Tilbrook
> Junior Engineer
>
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