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January 2009

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Subject:
From:
Larry Dzaugis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Larry Dzaugis <[log in to unmask]>
Date:
Fri, 16 Jan 2009 19:51:09 -0600
Content-Type:
text/plain
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text/plain (64 lines)
Reprint the board if there is too little paste. The registration required
for BGA's, 402 and smaller will most likely reprint well enough.

Bridging depends on the paste used. Some will break substantial bridges
apart and others will bridge if the flux bridges.

Some customers will allow a bare board to be washed in an ultrsonic cleaner.
Populated boards not allowed, there is a chance one of the componts could be
damaged or flux entrapped.


On Thu, Jan 15, 2009 at 1:40 PM, Leland Woodall <[log in to unmask]>wrote:

> Everyone,
>
> We have automated solder paste inspection machines immediately following
> each of our screen printers.  These all check for volume, height, and
> pad coverage.  We run only lead-free products, and also have a
> requirement that disallows any wiping or cleaning of a misprinted board.
>
> I'm looking for folks running a similar operation that can give me some
> recommendations on how they manage this process.  How many bridges do
> you allow?  How do you handle insufficients or inadequate pad coverage?
>
> Insufficient paste volume bothers me, as I'm always afraid our
> post-reflow AOI process will not detect the condition.  I also hate to
> scrap a board that has only a couple of pads with low or no solder.
>
> Any suggestions on how we can minimize scrap but ensure we have no
> escapes?  Do we write down the effected pads, mark the board, place the
> parts, and capture it after the oven?  How could one reliably manage
> this?
>
> Your comments are sincerely appreciated.
>
> Stay warm!
>
> Leland Woodall
>
>
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