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Registered Member #1806
Joined: Sun Nov 09 2008, 04:58AM
Location: USA
Posts: 136
I get it; the top pic is the LED on the board, the middle pic is the let led, and the final pic is the 1, 2, 5 second exposures. The high density of the intended array is for illuminating a board that is coated with photo resist, masked by the pcb artwork....
How am I doing... oh... no, wait.. were you going to literally "CNC" etch the board by selectively exposing the photoresist with the multiplexed leds?
Perhaps get a uv laser diode, and appropriateeba focusing lens, and drag it around the board to draw your pattern. Ah, here we go... Something like this in a 2 axis (at least) cnc might get the job done... ebay
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
He is trying to etch boards without makign a mask, thus the need for many small LEDS
he tried using a laser to expose it in an earlier thread, but didn't have much luck.
Although except for maybe etching the simplest of boards, it seems the resolution of this will be too low.
Heres my idea, take a black/white LCD panel and put a backlight of UV leds behind it. There will probably be a ton of loss from the uv being absorbed in the screen (but i wouldn't expect a whole ton, glass is pretty transparent under 380nm and plastic goes to about 350nm). Then just bring up a picture of the board you want and viola
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059
hmm.... i did try that with a damaged single line HD44780 panel but unfortunately the panel broke during removal of the backplate.
It might work, i've confirmed some light gets through. My latest idea is using a spare PCMCIA laptop edge connector (which has virtually identical pin spacing to 0603) and a spare LCD panel's STaB connector as a ground plane and interconnect. Plan is to use Charlieplexing (common +V and Gnd) to minimise the number of interconnects to sensible levels. Am up to 12 LED's soldered with no defects... :) pics soon.
Will need to use some sort of mask to prevent spurious PCB exposure, have an idea to use a sheet of acetate with pinholes at the correct spacing.
Registered Member #1131
Joined: Mon Nov 19 2007, 01:36PM
Location: Germany
Posts: 9
@cjk2 It depends on the setting of the laser-focus, from 0.05mm to 1mm but the mecanical resolution of the plotter is limited to 0,1mm. the best results are with 0,15mm laser and ~30mm/s pen speed.
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LED PCB etcher
