Hacked Gadgets Forum

June 24, 2006

Photo Etch Circuit Board Process

at 6:02 am. Filed under DIY Hacks, Electronic Hacks

How to Expose a Circuit Board

Clean the glass very well using glass cleaner and a lint free cloth. Inspect the glass for scratches and defects. A small scratch can cause issues when exposing so make sure there are none.
Clean any dust off the artwork. We will not be discussing how to create the circuit art in this article. I simply use a high quality laser printer and good transparencies. Print the image on the transparency so that it will lay toner side down against the copper. This will ensure that no light can leak under the toner.
The photo sensitive circuit boards will (should) be stored in a thick black bag or container. In a dark room remove one panel from the bag and seal the bag back up to protect the other panels from exposure. Remove the protective plastic film that covers the photo reactive coating.
Sandwich the circuit board and artwork between the pieces of glass. One piece of glass is laid directly on the table, the circuit board is placed copper side up on the glass, artwork is then placed toner side down onto the circuit board and finally the second piece of glass is laid on top. Remember this work must still be in darkroom conditions.
Turn on the UV light source and ensure every bulb is turned on and providing even light.
Put the UV lights in position to expose the circuit board. Ensure the electrical cords and other potential obstacles are not between the light and the circuit board since a shadow can cause exposure issues. The exposure time will depend on the type of coating your board has.
After the exposure time has elapsed lift the UV light assembly off the circuit board and remove the top glass.
Slowly peal off the artwork, depending on the type of coating you might be able to see a noticeable difference between exposed and unexposed areas of the board. For example with this type of coating the exposed areas show up as dark purple. Just a note that this is still needed to be done in darkroom conditions.