View Full Version : Photo etching a PCB
06-13-2007, 12:57 AM
I tried to etch my first pcb today and had no luck. I bought a photo etchable board and layed the trace patter over it and exposed it for about 30 minutes.
I then put it in the developer and it quick began to darken and got very dark where are the traces were in about a minute when i went to pull it out everything dissolved. What did i do wrong? To strong developer? To long in the developer? What?
I just get real nervous working with these chemicals.
06-13-2007, 08:01 AM
I do not know anything about the photo exposure process. When I made my own pcbs I used the instuctions HERE (http://www.fullnet.com/~tomg/gooteepc.htm) and followed them to the letter. I use the muriatic acid/peroxide etchant solution.
06-13-2007, 09:26 AM
I also use the same method as Brian and have had a high degree of success. Gloves, goggles, old clothes and working outdoors are a must.
During cold weather I float the etching container (a plastic shoe box) in warm water (an old dish pan) to help keep the etching time down. This is not needed during warm weather if you use a fresh mix of muriatic acid and peroxide. Good luck.
06-14-2007, 01:10 AM
How did you expose it was it with UV lights or in the sun?
Im not sure if you had positive or negative resist board but if it was positive resist then it was over exposed and softened all the resist or if it was negative resist it was under exposed and the resist didnt harden sufficently to the developer.
06-14-2007, 05:12 PM
I haven't used the photo exposure either. (too expensive to set up) I have had great success with the toner transfer method. I like using ferric chrloride because it is not as dangerous as the muratic/perox etchant. It has slower etch time and costs a bit more though.
02-09-2008, 11:36 PM
IMHO I like heated ferric chloride and the positive method, when I print the artwork on a laser printer the toner side goes against the board after the UV inhibitor film has been removed, this is done in a room with just incandescent light. then I expose the board and artwork in a contact frame under my bench shoplight with daylight tubes in it. the exposure lasts about 5 mins. I mix the developer (Sodium Hydroxide) at a 1:10 ratio as per the directions on the packaging. When i put the exposed board in the developer I swish the developer over the exposed side of the board with a foam paint brush, you have got to check the progress frequently, lift the board out of the developer and rinse it off, inspect it ( dip it in your etchant to see if the parts that you don't want turn color) if it still has etch resist between the traces return it to the developer for more developing. When the board is done the developed traces will be blue and the copper to be etched will be clean. this developing usually takes me about 5 mins, then the board is rinsed under running water. Then the developed board goes into the heated etch tank for roughly 30 mins use an aquarium air pump to agitate the etchant over the board, it works faster. My etch tank is a Sterlite 1 gallon plastic pitcher, I made the board holder out of some scrap plex I had laying around . I actually bought a etch heater, mistake, a small aquarium heater will do the trick and they are cheaper, ( tank, heater and, air-pump can be had at your local wally world) A word of warning, Ferric Chloride starts to out-gas at about 100F, preset the tank heater with water in the tank to get the temp at about 95F. Also getting the MSDS (material safety data sheets) pages for the chemicals is a very good idea, just in case you mistake your ferric chloride etchant for the dark beer that you were drinking. I lift the board frequently to check the progress of the etch, and when its done, rinse, dry ,inspect, drill and, stuff the board with your components.
Board making is an easy process if you pay attention to detail and its not that dangerous a task. Be Safe
02-11-2008, 12:41 AM
i am not worried as i deal with chemicals every week even unstable ones in chemistry these dont scare me at all
02-12-2008, 04:56 AM
I use ammonium persulphate and a jug of boiling water.. Works very well, is not messy.. just make sure you are in a well ventalated, it bit of ammonia is realeased!
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