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September 1998

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Subject:
From:
Nüchter Wolfgang (FV/FLT) * <[log in to unmask]>
Reply To:
TechNet E-Mail Forum. <[log in to unmask]>
Date:
Fri, 25 Sep 1998 15:25:54 +0200
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Hi Matthew,
which company does suply LPISM and DFPISM ?

Regards
        Wolfgang Nuechter


> ----------
> Von:  Matthew Park[SMTP:[log in to unmask]]
> Antwort an:   TechNet E-Mail Forum.;Matthew Park
> Gesendet:     Donnerstag, 24. September 1998 17:13
> An:   [log in to unmask]
> Betreff:      Re: [TN] Help! Plugging vias
>
> Chiman!,
>
> What is the customer's purpose of plugging vias completely with
> solder mask?  I don't think it is possible.  Maybe some fab guru's
> can elaborate on it.
>
>  We tent all via holes from the bottom side to prevent solder
> pluggings during wavesoldering process.  It does a wonderful
> job with LPISM, even though holes are not plugged with
> soldermask.   Our via size is from 0.4 - 0.6mm.  If via is bigger
> than 0.7mm, it does plug the hole with solder sometimes.
>
> Try DFPISM (dry film), it does excellent job of tenting small and
> large vias with soldermask.
>
> regards
> Matthew S. Park
> NII Norsat International Inc.
>
>
> >>> Chi-man Chan <[log in to unmask]> September 24,
> 1998  2:59 am >>>
> Currently we have a big problem on plugging vias with solder
> resist. Our
> customer requires that vias must be completely filled with solder
> resist. (i.e. light cannot go through). The via size is 0.3-0.5 mm.
> We
> use liquid imageable solder resist. I have tried to print with 43T
> then
> 32T open screen wet on wet on both side of the board. It does
> not work.
> The vias seems to be blocked with resist after screen-printing.
> However,
> some vias open again after track dry and developing. I have
> reduced the
> thinner from 5% to 2%. It does not work and causes a lot of
> bubbles
> among tracks. In order to completely plug these vias, we now
> print these
> boards with dot pattern before solder resist  printing and after hot
> air
> solder leveling. Some vias are very close to SMD. It is a very hard
> and
> time-consuming job. I think there should be an easier way to do
> this
> job.
>
> Any feedback is appreciated.
>
>
> Regards,
>
> Chan Chi Man
> [log in to unmask]
>
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