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March 2002

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 20 Mar 2002 06:53:46 +0200
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Iain

Ensolv is based on n-propyl bromide which is a very strong solvent (much
stronger than CFC-113). Some laminates, depending on their state of
cure, could well be attacked. I'm not quite clear about your cycle: were
the boards in the freeboard zone overnight? If so, anything could
happen, especially if the refrigeration is up the pole. My guess is that
even a 30 min cycle is risky.

BTW, if your freeboard isn't working, you are risking undue workplace
emissions. This solvent is quite toxic (most manufacturers recommend
operator exposure levels in the 5 to 25 ppm range. As a ref, the OELs
for carbon tet are from 3 - 10 ppm, depending on the country.). It is
also ozone-depleting.

Brian

[log in to unmask] wrote:
>
> Teckies, need a little help hear!
>
> I have recently experienced a problem whilst cleaning double sided FR4
> dual technology multi-layer boards that had been wave soldered.
> The boards (4 off) were put into a fully automatic batch cleaner end of
> day shift which uses a Brominated solvent 'ENSOLV ionic' .and removed
> the following morning first thing.
> The cleaning m/c is a vapour degrease system which has a refrigerated
> coil at the top of the bath, this provides a free board zone above the
> vapour which forms part of the cycle (draining).  =20
> The cycle time is usually 30 minutes.
>
> The problem is that the boards appear to show weave / pre-preg
> separation across all of the boards leaving the weave visible but not
> through to the top layer.  Around thru' hole terminations the board has
> clearly delaminated.
>
> I performed 100% inspection on another one of the wave soldered batch
> which appeared fine.  I repeated the cleaning exercise and the post
> cleaning result was the same.  =20
>
> Two things to note, firstly, when the board was removed after the
> second=
>
> cleaning operation the m/c had malfunctioned as the cooling coil had
> not=
>
> worked so the free board zone was hot with vapour.  What I cannot
> guarantee is that this did not happen during the first cleaning
> operation (4 off), I can't say I noticed the boards being hot but I
> suppose the m/c could possibly have malfunctioned part of the time.
> Secondly, these boards have been cleaned previously in the m/c but
> during a shift and removed after the cycle.
>
> Has anyone experienced this type of occurrence?
>
> CIA,
>       Iain.
>
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