Hi Jason.

These Component Manufacturers don't make it easy for us Process Engineers do
they!!

I am assuming that you are getting 1 leg on some devices that is not
soldering yes?

If so here are a few tricks you may want to use and checks that you might
want to make.

1. Skipped joints on Wave Soldered SMT devices can be caused by outgasing of
the flux from under the device, therefore check the quantity of flux that
you are putting onto the PCB and check that your preheat is hot enough to
drive out all the solvents before the PCB hits the wave.

2. Ask the design dept. to increase the length of the pads. This pad will
then reach beyond the void in the solder, that has formed around the device,
and the solder will wick up the pad.

3. Increase the temperature of the solder bath. The increase in temperature
will lower the surface tension of the solder and help the solder reach the
legs.

4. Check that the pads and device legs are free from contamination. (Speaks
for itself).

5. Increase the height of the chip wave. This does two things, a - forces
solder at the PCB under higher pressure which may get closer to the legs, b
- the PCB will get hotter, thus drawing less heat away from the solder wave
so the surface tension of the solder will drop (only by a small amount but
it may be enough)

6. Give Up and become a flower arranger!!

Hope this helps



===== Original Message from TechNet@PAT [log in to unmask] (TechNet E-Mail
Forum.) at 9/11/98 15:45
>I'm searching for tricks of the trade for soldering the unbearable 3-legged
>transistor.  We have the correct orientation on our panel, but seem to still
>have problems wave soldering them intermittedly.  I would appreciate any help
>you can give with soldering them.
>
>Jason Smith
>Process Materials Engineer
>Lexmark Electronics
>
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Mark Austin (Process Engineer)
ACW Technology Limited
Hylton Road
Petersfield
GU32 3XX
ENGLAND

TEL - +44 (0) 1730 300000
FAX - +44 (0) 1730 266045

Email - [log in to unmask]

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