Possibly very long times over liquidus could be contributing/aggravating
dewetting conditions. However I would not expect properly applied HASL
finish to dewet if exposed to 230C. The fact that you are using VPR as a
heat source, and SN96 on the other side of the PCB is not really germane.
In fact in the absence of solderability test equipment a pretty good test
for solderability for Sn63 finished boards would be to reflow them fluxless
in an inert atmosphere at around 230C and visually inspect for pull back and
poor wetting.......
Regards
Mike Fenner
Indium Corporation
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ido Mashall
Sent: 13 May 2004 08:54
To: [log in to unmask]
Subject: Re: [TN] Reflow problem
to me it sounds like a difference in the melting temperature.
HASL is usually 67/33 Sn/Pb with lower melting point than your paste SN96.
when heating to get soldering to the high temperature paste all the HASL
become a fluid
what result in the situation you mentioned.
to my opinion you will need to ask for different HASL with higher Tg or
other class of PWB finish. e.g. silver for
that kind of paste.
best regards,
Ido Mashall
----- Original Message -----
From: "Jason W. Gregory" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, May 12, 2004 2:26 PM
Subject: [TN] Reflow problem
> Hello all,
>
> After running a single pass of a double sided SMT board, the bottom side
> solder from HASL is spiking and pooling up in the middle of the pad (from
> gravity), forcing us to wick and prep the side prior to running the
bottom.
> You can actually see the copper showing lightly around the edges of the
> pads. We are running vapor phase reflow and the solder paste used is SN96
> (high temp soldering). Has anyone seen this? I am leaning towards profile
> issues. However, I wanted to see if anyone has seen this and if it was fab
> issues or not.
>
>
> TIA,
>
> Jason Gregory
> Manufacturing Engineer
> LaBarge Inc. --- Houston
> (281)207-1464
> (281)207-1435 fax
> (832)724-0076 cell
> [log in to unmask]
> http://www.labarge.com
>
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