How's this:

1. Build a table that can move a PC board in one dimension in 1/300"
increments with no cumulative error.
[Old plotter anybody?]

2. Create a UV LED bar containing LED's on 0.1" centers. Over the LEDs is a
mask containing 1/300"+ holes on 0.1" +/- 0.0005" centers [this is the
tricky part :-)]. The holes need to be a bit oversize so that consecutive
stripes will overlap a bit.

3: Mount the LED bar over the PC board on the table. The mask can almost be
in contact with the board.

4: Attach the LED bar to an indexing mechanism that allows it to move
perpendicular to the direction the PC board in 1/300" +/- 0.0005 steps (with
no cumulative error).

Now, to plot the board:

repeat until done:

Run the board from one end to the other.
Index the LED bar one step.
Run the board back.
Index the LED bar one step.

I figure you should be able to move the board a good 1" (300 steps) per
second.
Reversing direction should be about 1/10 of a second, which should give you
plenty of time to index the  LED bar.

It only takes 300/0.1 = 30 passes to do the entire board.

Thus, a 5" board would take about:

30 passes/board * 5 " * 1"/second        ; for scanning
+ 30 passes/board * 0.1 second           ; for reversing

This comes to 150 seconds + 3 seconds = 153 seconds.

That's pretty fast.

Now you may find that due to lash in the PCB board that you need to do all
the 'writing' in one direction. This would double the time.

Also, this is assuming that  you can get enough UV intensity to draw this
quickly.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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