Steve, one thing you want to check is the plated through holes themselves.  See
if you either got a bad composition or some type of residue in the holes.  I've
seen the composition sway away from the eutectic.  Not to mention that sometimes
board vendors will not clean off their HASL flux good.  You may check a couple
of these out.  When the compositions sways away from the eutectic, you phase
diagram shows you that you need more heat to wet by capillary action.  Go back
to your basics before changing process parameters.



[log in to unmask] on 11/16/98 06:51:17 PM

Please respond to [log in to unmask]; Please respond to
      [log in to unmask]

To:   [log in to unmask]
cc:    (bcc: Jason Smith/Lex/Lexmark)
Subject:  [TN] Weird Wave Soldering Defect...




Hi Ya'll!

     I've been wave soldering some boards today that we've been building for a
customer over the last 2-months. They're a little 2" X 2" PTH board in a 30-up
panel, and haven't given me a lick of trouble till today...been waving fine
for the past two months. Other than wanting to bow big time while warming up
before hitting the wave, there really isn't much to em'.

      They came out of the wave today with random barrels missing solder...and
when you look at the barrels that's missing solder, it's like the solder just
tinned the barrel and lead, and then said "hasta la vista baby, I'm outta
here.." and just dropped outta the holes?!?! It's random too...not
concentrated in any one area. What's got me perplexed is why did it appear
that it wet to the barrel and lead by the way it tinned them, but didn't stay
up in the barrel? There's no vibration anywhere, and the conveyer runs as
smooth as a babies butt...and I don't use a hot air knife.

       Nothing has changed with my settings that I've used over the past
2-months and have been working great up until today. I'm water soluble, foam
stone fluxer, Soltec Prisma with convection pre-heat, and Kester Flux. Cleaned
the pot and flux tank this weekend, so I was starting with a nice dross-less
pot and fresh flux...so what gives? Anybody seen this before? Any ideas?

Thanks in Advance!

-Steve Gregory-

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