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April 1999

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Subject:
From:
"Stephen R. Gregory" <[log in to unmask]>
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Date:
Tue, 27 Apr 1999 19:40:15 EDT
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In a message dated 4/27/99 4:27:23 PM Pacific Daylight Time, [log in to unmask]
writes:

<< I am in dilemma. We have designed a board which require double reflow
 process with selective wave operation. Here is the problem - How can I get
 vias filled  solder which will carry 1 amp current. Some vias are underneath
 the components and many are away from the selective wave fixture opening.

 Finished hole size of the via is 18 mils. Can fab house fill the vias?

 re,
 Ken Patel >>

Hi Ken!

They should be able to...for a price of course. But the problems with via's
that are already filled, especially if it's going to be a double-sided
reflow, is that during the first reflow you may get some solder "drooping"
out the via's on the backside which may cause some problems printing the
solder paste on the second side...especially if you have fine pitch.

I think the easiest thing to do would be to identify the via's that you need
filled, pull them into the paste mask layer of the Gerbers, get new stencils
with the vias also etched in them, and viola', filled vias!

I had to do that a lot on disk drive boards...glad I'm outta that business!
That can be as bad as building memory! hehehe...

-Steve Gregory-

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