Tim, thanx for the reply!
When dry films first hit the scene many years back, we began using
them for our boards, mostly mixed technology, and were having solder
ball and thickness issues, and like a lot of the industry, we went to
LPI for all of our products. I am reluctant to travel back down that
path, and we would have to requalify our board. However, I want to
keep open-minded. But I know some of our board vendors no longer
promote dry dilm, and have moth-balled the process.
Are you using dryfilm mask to successfully cover/plug vias on
reflow/reflow boards with HASL finish?
And are you having solder balling or mask thickness issues? We have
multiple .5mm pitch "thin" devices on this assembly, so mask thickness
is a concern.
Please respond with your dryfilm experience, I'm all ears!!
Thanx again Tim.
Jeff Hempton
______________________________ Forward Header __________________________________
Subject: Re: [TN] plugged vias, or no plugged vias?
Author: Timothy Reeves <[log in to unmask]> at Internet
Date: 10/18/1999 6:07 PM
Have you considered dryfilm soldermask?
Tim Reeves
> ----------
> From: Jeff Hempton
> Sent: Monday, October 18, 1999 11:48 AM
> Subject: lpugged vias, or no plugged vias?
>
> Hey gang,
> In a previous life, we did not worry about plugging vias in
> reflow/reflow boards for vacuum pulldown, since we were lower volume,
> high mix military bds., and could afford the time at test to
> clamshell
> or overclamp (Technical test terms I learned recently from the test
> group guys...).
>
> We are no-clean, and high volume. We have Genrad inline testers,
> which
> work quickly with vacuum pull-down, and the test guys like it this
> way. And we have been playing with various methods of plugging test
> vias with printed solder paste, and all other vias with LPI, and
> either get flux-vs.-probe problems or HASL solder caught in the LPI
> via pockets that resurrect themselves as solder balls during reflow!
> We have one small 4" square board that has about 300 vias, and are
> having a-heck-of-a-time trying to find a good solution for this. Oh,
> and all via annular rings must be solder resist covered or conformal
> coat covered, due to extreme environmental uses.
>
> Can anyone out there share some insight into this issue.
> Thanx in advance for your collective insights!!!
>
> Jeff Hempton, Sr. SMD Mfg. Engineer
> United Technology Electronic Controls
> e-mail: [log in to unmask]
>
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