In a message dated 3/3/99 6:43:33 AM Pacific Standard Time,
[log in to unmask] writes:

<< Does anyone know of a manufacturer or vendor that may make or sell this
 product, if it exists?  We are basically looking for individual preform
 "doughnuts" that are held in place by Kapton or some other similar material,
 that can be removed after re-flow.  I looked into Winslow Automation's
 SolderQuick product, but apparently they only do re-balling for BGAs on
 Kapton like material.  Any information would be greatly appreciated.

 Thanks, >>

Hello John!

     I just went through this drill for a series of products we're building
for one of our customers. They're a supplier of PC104 cards...embedded
controllers, power supplies, ect.

     PC104 cards are a standard of boards that interface together via what's
called a stack-through connector. It's basically a sorta' "T" shaped pattern
of 104 long gold plated header pins on .100" centers with a female receptical
at the other end, the pins go thru the board, and the whole kit-and-kaboodle
must be hand soldered on...unless of course you have some other method. Hand
soldering them isn't a problem until you come to the last 18-pins that are one
row in from the outside (they're in a 4-row pattern), that's when your rework
operator has to be caffeine free, and snake her soldering iron around the pins
to solder the inside row and not get any solder on the gold plating of the
other pins...my best lady can do all 104 pins in around 6-7 minutes, averages
out to anywhere from three an a half to four seconds a pin.

     There's quite a few vendors that make individual donuts. There's also
tools that can be made for the donuts where you take a handfull of dounuts
them spread them across the tool, and one donut will seat itself into a recess
and the others will fall away. Then you take the connector or whatever, and
insert it into the holes in the tool, flip the whole mess upside down and pull
the connector out, and you have a donut on each pin...it's faster than trying
to put a donut on each pin yourself, but still too much trouble in my book
because these donuts don't have any cored flux, so you would still need to
pre-flux before reflow.

     The were two vendors that I looked at that had connecting types of
preforms, they were Kester and Indium. Each has a different approach to their
preforms, both have preforms on .100" centers. Kester preform are solid,
stamped preforms...no-flux. The sampled ones I have are in a series of
8-holes...a little better than loading one at a time, but still too much
hassle.

     Kester was the only vendor that warned me about the difficulty in
reflowing joined preforms like these. They warned that adjacent pins must heat
equally to the same temperature otherwise the solder could wick to the hottest
pin and leave the cooler one insufficient...makes sense to me knowing that
solder will flow to the hottest area.

     Indium does things a little differently, their preforms are actually
etched and do contain flux. They come in sheets and you cut them to what ever
size you need...I figured I could get 16 boards worth of PC104 footprints out
of 1-sheet. The problem with Indiums preforms is that they stretch so easily
and it's not hard at all to get the .100" centers so outta shape that it
becomes a real pain in the butt to get them on...so I'm still feeling that the
preforms are still too much trouble. Can't find anything that'll compete with
3-4 seconds a pin.

      But then I get turned on to Teka. They make PC104 connectors with the
preforms already on the connectors, with flux no less. I think I've got our
customer convinced to start purchasing them...they've got to use up all their
Astron ones first.

      There's also dedicated hot air tools for PC104 connectors with solder
bearing leads. Zephyrtronics makes such a unit...but I understand they cost
around $5,000 to $6,000...quite a bit if you ask me. I'm planning to try and
make a custom nozzle for my Hakko hot air tool as it is a good hot air
source...I've got flow and temp controls on it and that's all you need. The
trick is going to be to be able to baffle the airflow in such a way (inside
the nozzle) that all pins receive the same heat. That's been the problem with
some systems, the pins close to the nozzle outlet wind-up smoking when the
ones on the outsides (at the each end) just reflow.

      I'll let ya'll know how I do with my nozzle...

-Steve Gregory-

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