Hi, I am going to put my 2 cents worth in.  This might apply to the messages
about ancient design issues as well.  I remember working at the EMPF in Indy
and a gentleman from England that had a concept of putting on material
(build up) around through holes that would come off the wave without a
complete fill.  The concept had to do with thinking the solder wave was
water and by causing turbulence (damming) affect the hole would then fill.
He used an example of a connector pin that would not fill but after adding
the material it would fill every time.  I cannot remember his name but his
idea came to mind this morning.  He was a Cat B (if some of you might
remember that from the WS-DOD-Mil days).  Maybe some of you can remember his
name or concept.  The material could be add and removed or be part of a
redesign.  PS I have always believed the Cat A, B, C, D, E, R that was used
was from the "Cat in the Hat" book.  Jon

 -----Original Message-----
From:   Stephen R. Gregory [mailto:[log in to unmask]]
Sent:   Thursday, August 10, 2000 1:00 PM
To:     [log in to unmask]
Subject:        [TN] Topside solder fillets after wave...

Hi all!

Been trying to dial a profile in on the wave today with a board that's
fairly
thick, probably around .090", polyimide, all PTH with a fair amount of the
IC's being ceramic. We use a spray fluxer and a RMA flux.

The first boards have been coming off without the preferred topside fillets
at a number of locations. I've been playing with the pre-heat, belt speed,
and even did something that I don't like to do, which was to flux the
topside
of the board.
All to no avail...I still had quite a few places that didn't have topside
fillets, and that is something that doesn't go over well here at all.

I started noticing that the places that didn't have topside fillets were at
the same locations. So I came back to my 'pooter and looked at the gerber
for
the board. What's really weird was that everyplace there's a thermal for a
pin is where I have no topside fillet??? I thought that thermals were
supposed to help prevent that from happening? But it's true, every single
place there is a thermal= no top solder. Has anybody ever seen that before?

-Steve Gregory-

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