>
> > I'm very much interested in trying this laser toner transfer method
for
> > homebrewing single-sided PC boards, and the thought came to me that
perhaps
> > an electric waffle iron would be a more practical alternative than using
a
> > clothes iron. With the PC board material and the paper sandwiched
between a
> > couple of pieces of aluminum or copper plate, the heat and pressure
would be
> > more uniform and it would become a matter of applying the pressure for a
> > suitable amount of time.
>
> Chris, I have not tried an waffle iron, but I got a 1 inch thick piece
> of steel (4x5x1 inch) and lapped it to make a very flat surface,
> attached a thermo couple to it. Using a hot plate to heat the iron block
> to to the target temperature then placing this on my PCB/toner image
> sandwich and clamping it with a toggle clamp with about 400 pounds of
> pressure for about 1 minute (20 pounds per square inch). This gives me
> consistent results.
>
That's what I felt would result, and I was thinking that using an
electric waffle iron would enable you to apply uniform pressure and a
somewhat controoled temperature. Guess I'll look around the thrift stores
for one of these and see what can be done.
>
> The target temperature is established for the toner formulation your
> printer uses. This involves taking an image on a piece of paper and
> while monitoring the temp of the hot plate, looking at the toner with a
> magnifier and using a sharp pointed probe and noting the softening temp
> and the melting temp (my toner melts at about 320 degrees F) The melting
> temp is when the toner becomes glossy (shiny). The pressure and temp
> combination will determine the amount of image spreading that will occur.
>
Okay, that gives me a guideline of how to condition the method that I'm
thinking of.
>
> On small pitch traces you may adjust the temp/pressure/time
> combination for best results. For very fine pitches, I use a temp of
> about 280 degrees (this will just tack the image to the copper) then I
> take this tacked PCB/toner/paper sandwich and place it on the hot plate
> and raise it to the toner melting point (without pressure) ... this will
> cause good adhesion of the toner to the copper with minimum image
spreading.
>
And that's even better. I'll definitely look for a small electric
waffle iron and see how to adapt it for small boards. I wonder now if
adding a thermocouple to one of the plates and then connecting it to some
sort of controller would help, or perhaps simply measure the waffle iron
temperature and adjust the time accordingly.
Chris
,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_ |/ Principal Engineer
oo\ Sonoran Radio Research
(__)\ _ P.O. Box 25240
\ \ .' `. Tempe, Arizona 85285-5240
\ \ / \
\ '" \ IEEE Senior Member #40274515
. ( ) \
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