Has anyone thought of making something like what the pizza delivery
places use? Put the board on a conveyer on one side, it goes through the
oven at a set rate and comes out the other side nicely baked. Seems like
it would be great for production work.

Steve Baldwin wrote:
>
> > Are you kidding? You sure better post "everything" about
> > this, otherwise someone will try to patent it out from
> > under you.
> >
> > A toaster oven usually works by direct radiation. What
> > temperature do you suppose the surface of the pcb gets up
> > to? And is this allowable, regards the specs for the chips?
> > And how does this compare to commercial smt cookers?
>
> I use a toaster oven too. I used to use a hot air gun and the results
> were pretty good but required a lot of operator skill and attention.
> Very easy to stuff it up. Then I tried experimenting with a pop-up
> toaster on its side, working on the theory that the smaller air
> volume would be better for control. The theory was OK but
> implementing it with a mass produced product wasn't all that
> practical. Because of the volume thing, I wasn't too sure how the
> toaster oven would go.
>
> I bought a fan forced toaster oven and after a bit of experimentation,
> found that putting the boards on the mica element formers from the
> previous toaster experiments was perfect as it forms a bit of a
> barrier between the top and bottom halves of the oven. I played
> around a bit with shelf height to get good even heat coverage.
>
> My procedure is also manual at this stage but it will be simple to
> automate as soon as I get time.
> I use a single thermocouple (as I know from experiments that it is
> representative) and the temp meter I use has time on the display.
> Put the boards in the oven.
> Set temp to max, top & bottom elements and fan on.
> When temp reads about 5 degrees below preheat, turn everything
> off. (the 5 degrees compenstates for the system lag so the temp
> will reach the setpoint and hold steady for around 30 sec).
> Wait the preheat period.
> Select grill and max temp. No fan.
> When temp reaches 200 degrees, turn off.
> The board temp will peak at 210-215 and drop off.
> At about 190 (solder solid again), turn the fan on with no elements
> (mixes in the slightly cooler air from below).
> I open the door a little at 160 degrees and fully at about 100
> degrees.
>
> If I plot the temp and time it's almost exactly on the line provided
> by the solder manufacturer. The whole cycle is about 5 minutes
> from board in to board out and yield so far has been no failures in
> about 75 board/panels.
>
> Steve.
>
> ======================================================
> Steve Baldwin                Electronic Product Design
> TLA Microsystems Ltd         Microcontroller Specialists
> PO Box 15-680, New Lynn      http://www.tla.co.nz
> Auckland, New Zealand        ph  +64 9 820-2221
> email: steveb@tla.co.nz      fax +64 9 820-1929
> ======================================================
>
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