I'm writing a reasonably detailed explaination on the use of photoresist for the traintools group. The polymerization reaction generated by UV light in photoresist is more complex than you would imagine. There are many ways to expose photoresist, but you have to do it right or resolution goes to pot. When I get it done - a week or two from now - I'll post it to the photo section of this group as well.
----- Original Message -----
From: Thomas
To: Homebrew_PCBs@yahoogroups.com
Sent: Wednesday, October 06, 2004 12:20 PM
Subject: [Homebrew_PCBs] UV laser exposure
Hi Christian
I am looking at your calcs from another angle here trying to figure all this out.... I'd like to know more about your Calculation if you'd care to share it with us in detail.
If there is any logic in my thoughts here, so 2 UV Flouro Lamps @ say 20Watts each, thats 40 Watts total and I spose that a %age of this is scattered and would not be directed at the PCB, so how much actual wattage is being used to develope the PR ??
What I am getting at here is that there was mention that UV LED's would not be strong enough that maybe so in the raw state, If the UV LED was concentrated using a Collimating Lense for a LD to get that small concentrated spot, maybe that could /would equal the equivalent of the UV Flouro wattage, the point is that these UV Lasers or UV LED Arrays at 1 Watt are $$ and regular High Output UV LED's are cheap if they could do the job
some neat stuff here http://www.roithner-laser.com/index.htm
Thomas
----- Original Message -----
From: Cristian
To: Homebrew_PCBs@yahoogroups.com
Sent: Wednesday, October 06, 2004 7:13 PM
Subject: [Homebrew_PCBs] UV laser exposure
http://www.crystalaser.com/ has QUV 355-25 Crystal Laser of 25mW at 349 or
351 or 355nm, just inside the photoresist window.
I don't know how much it is, for the moment, but the head is not so bulky.
One can mount it on a CNC Machine easily.
Of course, some simple optics is necessary, because the beam is 0.9mm diameter.
Calculations:
Photoresist needs maximum 100mJ/cmp, that means 4 seconds/cmp with 25mW laser.
That means 240 seconds for 100x60mm. Four minutes of XY Plotter work.
If my calculations are correct, that is not too much.
Cristian
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