Step 6 : Exposing the board


I used a 48” florescent shop light with ‘Day Light’ florescent tubes in it for the exposure stage. Set the shop light up 5 inches from the top of the board. I used 2” by 4” and some other sized blocking for this.
Working in safe light, gently peel off the white coating. Don’t touch the green photo resist. Put it under the florescent light, which is not yet ON. I put the PCB board on top of a piece of melamine board so I could move it around under the light (take account 5” top of the board adjust if necessary). Take your transparence, lay it printed side down. Now your reference word will be the right way around. Take the piece of glass or clear plastic and lay it on top of the transparency making sure everything is lined up the way you want it. If so, turn on the florescent light for ten minutes to expose the board. It is better to overexpose than to under expose. I did it for 12 min. 30 sec. Turn off the florescent light; remove glass weight and transparence (still in safe light).
(This picture was taken during the process).

Step 7 : Developing the board


Mix developer: 1 part developer to ten parts water. I used 50ml developer to 500ml water (THIS COULD BE DIFFERENT IF USING OTHER BRAND OF DEVELOPER). It is better to mix a weaker than stronger developer. Mix this before hand. Place board into developer solution, take a foamy brush and lightly brush the photo resist off for 1-2 min. You will very quickly see the green photo resist coming off. I think my board was in there for only 30 - 60 seconds, so watch closely because my board was not in there for 1-2 min. If left in there for too long, all the photo resist will come off. Next time, my solution will be weaker. Place board directly into water to naturalize the developing stage. Take a close look at the board to see if you need to touch up anything with a permanent marker. (I did not need to).

Step 8 : Developed Board


Here is a picture right after the board was developed. All the traces were intact, so off to the next step.

Step 9 : Etching the board


Still working in safe light, drill a hole in a corner of the board where nothing is there. Place a piece of string, fish line, (I used weed eater line) through the hole so you have something to pull the board out of the etch ant with. Place the board in the etch ant for 5-30 mins. Depending if you have a heater on and bubbles going. I heated the etch ant to 42 C or 108 F with air bubbles and took 11mins. to etch the board. I started checking at 4 mins. and noticed that the top of the board was etching quicker than the bottom, so I turned the board around. When finished, take the board out and put in water. I had 2 buckets to check the board during the etching stage and one clean bucket of water for it to sit in while I cleaned up. CLEAN UP TIME!

Ferric chloride is able to be heated no higher than 57 C or 135 F. An ideal etching temperature is 50 C or 120 F. I could not go that high because the fish tank thermometer I used did not go that high. I am going have to find one that does.

This is a homemade etching tank made from acrylic plastic. It holds 1 liter or 32 OZ of etch ant nicely. Here is a ‘how-to’ that I found www.embeddedtronics.com/etchant.html. I don’t recommend building one, just get 1 gallon of etch ant and a 1 gallon rubber made container. If you do decide to make one, notice the big rubber made container that the pump is sitting on. Place the tank in one of those when etching in case the tank leaks or ruptures. Use proper acrylic glue not just silicon like they recommend.

Step 10 : Step8. Finished product


Here is the finished board. The photo resist is still on and apparently you do not need to remove it to solder. I found the photo resist to be a pain to solder to. I found it easier to remove the photo resist and solder the board, that way then you can take off the burs from around the holes.