Thanks all, Dwayne, Mircea

great information from everyine, and I like that tip about the 'L' frame 
for alignment.

Rolf

Dwayne Reid wrote:
> At 09:18 AM 11/9/2006, Rolf wrote:
>   
>> Hi all.
>>
>> I am doing some hobby-related playing with building my own PCB's... I am
>> using the positive-resist coated PCB's, and am pondering a really basic
>> solution to being able to see what I am doing while working on it
>> (drilling register holes, aligning transparencies, etc).
>>     
>
> If I can interject something here - you shouldn't need to use 
> register holes.  I've written about this many times previously (check 
> the archives) but will repeat it again:
>
> Grab a chunk of un-etched copper-clad PCB material and cut it into a 
> "L" shape - something like a small version of a carpenter's 
> square.  The ones I make usually have legs 4" and 6" long; the legs 
> are about 3/4" or so wide.  I use copper-clad PCB material because it 
> is the same thickness of the board you are going to expose.
>
> Tape the bottom transparency to the legs (both legs).  Now flip the 
> whole thing over and tape only the long edge of the top transparency 
> to the long leg, taking care to get the drill holes lined up exactly.
>
> Now: just slide the sensitized PCB material into the pocket formed by 
> the 2 transparencies, stick into your vacuum frame (you DO use a 
> vacuum frame, don't you?), expose.  My vacuum frame is made from 2 
> similar pieces of glass so I simply flip the frame over to expose the 
> other side after the 1st side is done.
>
> The reason for taping one transparency to only one leg is that I find 
> that the transparencies stick to the photo-sensitive emulsion during 
> the expose cycle.  Taping only 1 edge allows easy peeling of the top 
> transparency from the board; once it is free, its easy to peel the 
> bottom transparency from the board.
>
> Quick, easy, accurate.
>
> dwayne
>
> (Dupont Riston 4315 photo-sensitive film laminate, Kepro laminator 
> (much modified GBC unit), mercury-vapor expose lamp with timed 
> shutter, potassium carbonate developer, ammonium persulphate bubble 
> etcher, sodium hydroxide stripper, Gordon Robineau's really cool PCB drill).
>
>   

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