Homebrew PCBs

Tony Smith wrote:
>>> 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
>>     
>
>
> Sounds like you've got too much time on your hands, you need a hobby  :)
>   
If you are going to do a process several times, you will always spend 
LESS total time if you take the time up front to build the proper tools 
... the steel I used was a mill "cut-off" so it had some ripples in it 
... if the steel had been cut when the steel was cool, the lapping would 
be done in 30 to 90 minutes
> I can't remember what the original thread was about, but it was something
> like a clothes press.  I guess a lot of people start eyeing the sandwich
> maker in their kitchen as well...
>
> That chunk of steel you have won't bend easily, one problem solved.  How
> long does it take to heat up?  Obvious for making a batch it'll be faster
> than a laminator, but for one-offs?
>   
It takes about 10 minutes from room temp the first use ... I always 
allow the temp to over-shoot by about 20 degrees then set the steel 
block on a narrow strip of wood ... when the temp comes back down to the 
target   i use it ... the thermocouple is on the top of the steel so 
there is a temp gradient across the steel
> So for double sided you just flip the board over afterwards?
>   
I do one side at a time ... I spray paint side 2 .. image transfer and 
etch side 1 ... then spray paint side 1 ... image transfer and etch side 
2 ... I do drill alignment holes for registration
> (BTW, gluing the sandpaper to a sheet of glass works well for lapping stuff,
> in case you don't have a cast iron table saw handy.  Glass is very flat.)
>   
> Tony
>
>
>
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