Homebrew PCBs

So what? Just because it has mass it can't be controlled?

It'll work just fine even with a simple on/off controller. Put an
aluminium plate on top of it to spread the heat, the cast iron plate
is unevenly heated by the coil. Drill a hole inside the aluminium for
the thermocouple.

Of course the temperature will overshoot that way with a simple on/off
controller, but after the initial overshoot it holds pretty steady.
The mass is high enough that adding a board won't cool it a bit, so no
quick control is necessary.


If the boards get brown you overheat them, I agree. However If you
order some boards without soldermask and leadfree immersion tin from
PCB Pool you will also find them slightly browned towards the edges,
but much less than this one. Dipping them in tin just does that and
leadfree has made it worse. I guess it should be OK, PCB Pool aren't
amateurs and the boards have worked fine so far. With soldermasked
boards you just don't see the color any more.

ST

On Sat, Feb 6, 2010 at 4:41 AM, DJ Delorie <dj@...> wrote:
>
> "James" <jamesrsweet@...> writes:
>> You could attach a thermistor to the hot plate and build a simple
>> temperature control circuit to keep the temperature FAR more stable
>> than the controls, if any, that are built in.
>
> I've thought of that, but mine is cast iron - it has way too much
> thermal mass to be accurately controlled *at all*.  It takes about
> three minutes to get up to temperature, and the ramp-up is pretty good
> for reflow soldering, so as long as I don't mess with it it works for
> one board at a time, or multiple boards simultaneously, just not for
> multiple boards consecutively.
>
> If I'm going to start hacking up an mcu-controlled reflow device, I
> won't start with a cast iron hotplate.
>
>