I have
a small solder fountain that I use for this. Mask surrounding area, kapton or
preferably water washable mask (thermal insulation) May have to preheat the
board first. The othe method I use for backplanes is to cut the part off and use
resistance tweezers to pull the leads. Then the solder is easier to
remove.
Charles
It seems sometimes that what I
post opens a big can of worms...open mouth, insert foot. I've received some
emails directly, that have put me in my place.
I want to apologize to
everyone, and I promise to leave the list moderation up to the moderator; Jack
Crawford.
My hope is, that my occasional indiscretions can be forgiven.
I try to support this distinguished list with whatever I can do. I just want
to say I'm sorry to everybody.
Now on to my question. I've just
recently been confronted with a big, thick, lots of copper back-plane. It's
the same one I posted about wave soldering just recently. BTW, I was able to
get satisfactory topside fillets by baking the assembly at 100 C., whisking
out of the oven to the wave machine, fluxing the top-side, and hitting it with
both the turbulent and laminar waves.
The next big challenge is rework.
Wished we could have built them without having to rework anything, but we have
a few SIP resistor networks that were put in with the wrong polarity, and it
seems almost impossible to rework these guys without lifting a pad on the
bottomside. The pads have no traces connected to them on the surface layer,
and the barrel looks fine...it's just the annular ring pad is gone. I have a
AIR-VAC PCBRM-12 and I've tried to "Pre-heat" things by just placing the area
into the nozzle, for a few seconds, then remove it, multiple times, so as to
drive heat into the laminate, before I attempt the actual removal.
I'm
thinking I probably need to pre-heat the assembly over a fairly large area
around where I'm trying to attempt rework, because the thickness of the PCB,
and the way it sucks heat away from the rework location. I'm learning there is
no-way to rework the PTH on a AIR-VAC the same way we do with .062" boards.
I'm thinking of a laboratory hot plate to pre-heat (that's because I have one
here).
Any tips or help that anyone can share would be greatly
appreciated...
-Steve Gregory- ---------------------------------------------------
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