I had a pair of 12 inch glass panes made up at a window shop. Note the hole in the corner. This is for the future when I make a vacuum frame. The foam around the board is weather stripping. I put it on when I was testing vacuum framing with a hand vacuum pump. It actually does a pretty good job of sealing, but I will need a motorized pump because it does leak some.
This is a board I laminated photoresist onto earlier.
This is the mask I will be using. This is from a board I had built a few years back. It is a good test case because it is one of the most complex boards I built. It was originally done with toner transfer and had 5 mil traces. The mask was printed with an Epson R2400. I used this printer because it uses pigmented UV resistant inks. In a test pattern I was able to get clean exposures down to 3 mil. I think once I get experience using photoresist I might even be able to get 1 or 2 mil traces.
This is the mask on the board. Obviously this mask is bigger than the board, but this is just for demonstration.
The glass panes sandwich the board and mask. The foam is to the outside. I am not doing a vacuum frame in this case.
The whole assembly is set near a sunny window. It is partly cloudy today. During an earlier test on a cloudy day, I left the frame in the sun for 30 minutes and got traces down to 3 mil. Since I am getting some direct sun today, I leaving it for 25 minutes.
While the board is being exposed, I prepare the developer solution which is nothing more than sodium carbonate. In my area I it can be found under the name washing soda. I just poured a little into a plastic container. The toothbrush is for lightly brushing the surface of the board when I develop it.
Next I added some hot water and dissolved the washing soda. By the time the board is ready, the soda will be warm instead of hot.
After 25 minutes in the sun, I removed the board. You can see the exposed resist which corresponds to where the mask was clear.
Since the resist will continue to cure if exposed to UV, the board
should immediately be stored in a UV proof container until you are
ready to develop. You should leave the board for an additional 10 to 15 minutes before developing. I actually forgot to do this while making this demonstration.
Remember to remove the mylar coating before putting the board into the developer. I forgot this in an earlier test and had me scratching my head as to why the resist was not coming off!
When you are ready put the board in the washing soda solution. I lightly brushed the board with the toothbrush to help loosen up the unexposed photoresist.
This is the board after it is developed. As a quick and dirty test I think the board came out pretty well. However if I were really making this board, I would have to redo it because there were some defects. I am still learning how to do this.