Hi Steve,

My guess is your problem is most likely due to outgassing which is blowing
the solder out of the smaller holes. If it is, you should see evidence of
bubbling in other larger holes. You can test for this by using a hand
soldering iron and filling a hole with solder on an unsoldered PCB. Watch if
it bubbles vigorously. If it is outgassing you will need to bake the boards
at around 100 deg C for an hour or so. Don't keep the iron on for too long
or you may damage the PCB, two seconds should be sufficient to see the
problem.

The source of outgassing is moisture but it should not occur if the PCB's
have good hole quality and the correct thickness of void free plating. The
only way to check this out is to micro-section a defective hole.

Hope this helps,
Paul Gould
Teknacron  Circuits Ltd
UK

-----Original Message-----
From: Pratap Singh <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 21 November 1998 02:52
Subject: Re: [TN] Weird Wave Soldering Defect...


>Stephen R. Gregory wrote:
>>
>> 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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