Homebrew PCBs

Tony Smith wrote:
>> Hi,
>>
>> I was wondering if anyone has considered or tried using a 
>> heat press for the toner transfer method. They are usually 
>> used for transferring images onto t-shirts.
>>     
>
>
> There was a thread about it a while back (A year? More?).
>
> Track down Tom Gootee's page, I think it was him who tried it.  Might be
> some results there.
>
> Apparently it's a bit hard to apply enough pressure.  Clamping causes
> distortion, so you get pressure in one spot but not another, etc.  Dumping
> weights on top didn't seem to help either.
>
> Tony
>
>   
I use a heat press of sorts ... I make small PCB's  no larger than 3x4 
inches ... I have a 4x6x1 inch piece of steel ... I took a piece of 
aluminum oxide abrasive paper (8x10 inch) laid it flat on the top of my 
table saw and dragged the steel plate back and forth across the abrasive 
paper until it was flat and shiny (I actually made a motor driven 
fixture to do the dragging in a random fashion for me ... it took 
several days and several sheets of abrasive) ... I use a hot plate to 
heat the steel plate until it is the temp I want (usually 350 to 400 
degrees F) using a thermocouple attached to the steel plate to measure 
the temp ... I have ready a flat wooden surface that has the blank 
PCB/laser image/plane paper  ready to receive the hot steel plate ... I 
place the steel plate on the top cover paper and clamp the steel plate 
with about 300 pounds of pressure (about 25 pounds per square inch) 
using a wide mouth vice grip pliers (this is moderate pressure ... you 
can easily get 400 to 500 pounds of pressure) ... I leave it clamped for 
about 1 minute then off to the water soak ... I get good resolution and 
consistent results ... the flat surface insures an even distribution of 
pressure ... the thick steel plate holds the heat and won't distort 
under the moderate pressures and temps  used ...
Jim KI6MZ
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