Homebrew PCBs

"James" <jamesrsweet@...> writes:

> it doesn't matter how much thermal mass it has or how long it takes
> to heat and cool,

It certainly does when you have to control the temperature *change
rate* as well as the hold temps.  Proper reflow wants a specific temp
vs time curve, not just a pre-heated surface.  The iron plate can just
barely heat up fast enough for reflow, and mcu can only slow it down.

If I start with a cold plate, put my board on it, and turn it on, I
get a pretty good temp/time curve - takes about 3 minutes for small
boards, or 6 minutes if I add an aluminum plate for large boards (heat
spreader).  Six minutes is a little long.  I'd rather have an aluminum
hotplate I can mcu-control that can do a proper temp/time curve.

If you put a board on a pre-heated plate, the flux boils and spatters
solder (and parts) all over the place.  You really need to heat the
flux up slowly so it activates and cleans the metal without disturbing
anything, then dries up before the solder flows.

I also don't want to shock the board by hitting it with that much heat
all at once.