IBM 1620

Jon Elson elson at
Sun Aug 30 16:00:45 CDT 2015

On 08/30/2015 03:04 PM, Chuck Guzis wrote:
> PCB design was also a specialty, what with mylar film, 
> tape, white-out and India ink and, of course, an X-acto 
> knife.  The best people at this seemed to be from the Far 
> East.  Done probably at 4X scale, then reduced for 
> production.
Yup, back in the 70's I did a bunch of PCB design using 
mylar and black crepe tape, and pre-made donuts and IC pads.
UGH!!!  I still have a bunch of those sitting in folders.  I 
made my own reduction camera to bring the artwork down to 
1:1 size.

Then, in 1976 or so, I got my first CAD system, and printed 
everything out on plotters with India ink and Rapidograph 
pens on frosted Mylar.  If the pen didn't clog up or run dry 
before the print was finished, it worked pretty well, and 
there were Litho houses that mostly did ad copy that would 
do the reduction for a couple $.

I hacked a fiber optic light pen onto a Calcomp plotter and 
made some artwork directly onto film, and then in 1996 I 
built a laser photoplotter that cranks out 1000x1000 DPI 
images on red-sensitive film at 0.6 inches/minute.  It can 
do up to 20 x 24" films, but I've never gone over about one 
foot square.  The trick is, it has to be VERY accurate to 
line up with existing PC boards.  I mostly use it to make 
solder paste stencils, now, but originally made it for PC 
board master artwork.


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