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Subject: Re: [Homebrew_PCBs] Soldering a whole board at once?

From: ron amundson <mnphysicist@...>
Date: 2004-08-15

A few things.

1. Do not use no clean flux, if you want your board to
last in a humid or possibly corrosive environment.
Temperature control is critical for most no clean
fluxes. It is unlikely one could get consistant,
uniform profiles at home... and is such, if you make
an error in temperature settings or dwell time, your
board may die in a year or two due to corrosion.
2. Preheat is important, and a hot plate or radiant
heating element will do fine. Try to match the thermal
profiles as presented in the parts datasheets.
3. fumes as mentioned are bad news, use an exhaust
fan, but keep the air movement low over the pot so as
not to shock cook the board after removal. After a few
seconds quick cooling is a good idea. Again check the
profile.
4. Material selection for the solder container is
important. Some metals will react with the hot solder
and deteriorate, others will rapidly contaminate it.
5. Put a tray filled with sand under the solder bath.
You don't want to have molten solder roll off your
workbench onto your shoe, or floor. (no tennis shoes
btw, leather is much safer
6. skim the dross before each board

An outfit I know built their our own machines for
selective soldering. They did however use solder
pumps, skimmers, and tight temperature control. It
saves a lot of labor if you have mixed through hole
and SMD parts to not to have to solder 50-100 pins by
hnad. The machines were roughly 12"X18" so they could
easily put them right on a production workbench.

Ron



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