Re: gEDA-user: Cheap 4 layer manufacturer?

[Randall Nortman <geda-lists@xxxxxxxxxxxxxxx>]

On Sat, Oct 15, 2005 at 10:24:03PM +0200, Kov?cs Levente wrote:
> On Mon, 10 Oct 2005 22:45:30 -0500
> Darrell Harmon <mail@xxxxxxxxxxxx> wrote:
> 
> > Toaster Reflow oven for the first few. I plan to see how it
> > goes. If it works well, I will continue that way, if it does
> > not I will pay somebody.
> 
> I want to do the same. Do you have details about this technology? I've
> already bought a toaster for this. The question is what kind of sensor
> to use. I have some resistive sensor which has the max temperature
> approx. 300deg. I hope it'll be okay.

If you mean 300 Celsius, then that should be OK, so long as it doesn't
actually melt above that temperature.  However, I have had very good
luck without any sensor at all other than my own eyes.  When the
solder paste melts, it turns from dull gray to shiny silver metallic
in appearance.  The change is quite easy to see, especially if you
shine a flashlight on the board to get better illumination.  You can
very quickly confirm that the paste has melted on different parts of
the board this way.  I have not bothered trying to adhere to a strict
heating/cooling profile -- I just do everything under manual control.
Do a pre-heat stage for a couple of minutes at low temperature and
then crank it up all the way until the paste melts, then open the door
to cool.  I haven't done this very many times yet, but so far I
haven't fried anything.  (Might have degraded the performance of some
analog components -- that would be hard to measure.)

If I had to do this a lot, I would probably go ahead and put the thing
under computer control, but so far I haven't bothered.

-- 
Randall