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October 1999

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Subject:
From:
Charles Barker <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 26 Oct 1999 10:34:42 -0500
Content-Type:
text/plain
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text/plain (119 lines)
Richard,

I suspect that the holes in the area of the board that are not soldering
properly are connected to the plane layers. This will cause them to soak up much
more heat than the other holes. This can be checked with an ohmmeter, looking
for continuity from the problem holes to power and ground. If this is so,
suspect that this is one of the areas reaching a lower pre-heat temperature.  If
this is the case, you need to get the top-side tmep prior to hitting the wave to
come up more.  This can be done by slowing down the conveyor speed a bit.

Another thing to measure is how long the board is in contact with the wave. If
my memory serves me right, it should be about 3 - 5 seconds. The board also
needs to go about 2/3 of its thickness down into the wave.

You can look at the inside of the holes with a prism device and a backlight.
That will give you some idea of the quality of plating/drilling in the holes. u
see a buch of nodules and extreme roughness in the holes, then the board shop
may have messed up the drilling/plating process. That may give you pin holes in
the sidewalls, which will cause blow outs and/or blow holes in your solder
joints.

To me, it sounds like you main problem is not an even enough pre-heat across the
board.

Good luck,

Charlie B.








Richard Tilbrook <[log in to unmask]> on 10/26/99 03:05:31 AM








 To:      Charles Barker/US/I-O INC@I-O INC

 cc:



 Subject: Re: [TN] HELP!!! - flow solder problems RT








CHARLIE,

PLEASE FIND BELOW THE ANSWERS TO YOUR QUESTIONS:

Other folks have asked pertinent questions which I am not repeating here.
You might want to look at the preheat temp.... What is the topside temp
just
prior to the boards hitting the wave?

85 TO 104 DEG. C - VARIES ACROSS THE BOARD.

What kind of flux are you using and how is it being applied?

ALPHA METALS 615-15 - RMA LIQUID FLUX (15% SOLIDS) SPRAY APPLICATION.

Is it the same 4 - 5 holes on each board?

THE 4-5 HOLES OCCUR IN THE SAME SMALL AREA.

The the hole-to-lead diameter ratio big enough to allow the solder to
flow/wick
up the lead?

WE AREN'T SURE.

Is the solder just simply not flowing up the lead or is the solder being
blown
out of the hole due to outgassing due to contamination or pin holes in
the
plating in the holes?

AGAIN, WE DON'T KNOW - WE DON'T MAKE THE BOARDS, AND WE CAN'T TEST FOR
THESE
WITH THE SUPPLIED BOARDS.

These are a few things to check for.

Good luck,

Charlie B.

THANKS FOR YOUR TIME,

RICHARD TILBROOK
BRITISH AEROSPACE

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