jdraughn
Junior Member level 1
pcb make uv
Sorry for such a long post here, hopefully anyone who knows enough to help me does not run out of patience before they finish reading this. I know I will figure this out via trial and error but would prefer to save some money by having an experienced person point out some mistakes.
I finally got to the point where I tried to make my own PCB. I learned a ton but have a few questions, mainly how to tell if your over/under exposing or over/under developing.
I will describe my setup and procedures in as much detail as I can and describe my symptoms, maybe someone has some ideas.
I printed the schematic on overhead transparencys. I read they suck though on some of the website tutorials that I came accross and that I should use vellum or paper soaked in peanut oil. It seems there were a couple of other materials mentioned too that would be better.
I had 3 decent prints as I was experimenting with contrast and other print settings built into the printer itself to try and make it as dark as could be.
I printed it using a multi $100k xerox full color laser printer. When I went to expose my boards I overlayed the 3 good images I had over each other and taped the sides so there was no chance of them slipping. It is a perfect alignment as far as I could see. Bit I am afraid that this cost me some resolution when I exposed the board since the top sheet would cause a slight blur on the board, and I think that may actually be pretty much be the whole problem that I am generally having.
I made a custom exposure unit. I bought some clearance bug zapper UV bulbs from walmart a few months ago during the winter months just for this use. They are 40 watt, about 4" wide and around 12" long, one bulb folded in a tight "U". I wired them to a electronic ballast from home depot. It's just temporary right now, I plan on having two switches, one built into the lid and one outside so it won't run unless the lid is shut, and also having a built in timer so once I get this figured out I will be able to get perfect exposures every single time.
I know im putting out a lot of UV rays compared to just using normal flourescents, but I don't know if it's comparable to a real "exposure" fixture or somewhere inbetween. I covered the whole thing with a thick towel to protect my eyes and I could swear when I poke my hand under I could feel tingling, but it could be my imagination. I didn't keep it under long enough to find out for sure, I don't need skin cancer on my hand
My first 2 or 3 exposures I didn't have enough weight on the glass or something so I had messy exposures. Took me about 3 trys before I realized this was the problem (I was also using crappy PCB's that had been pre-exposed to light because my dogs had chewed up the corner of the board while it was still brand new in the packaging.) I was using these crappy PCB's even though I knew they probably wouldint work so I could figure out what the heck I was doing.
After I realized what was going on I taped the transparency image to the glass and layed it on top of a thick paperback book. That made a huge difference but the problem that I am having is that my copper traces are slightly merging together, which was still occuring even after sandwhiching the image real nice and tight.
I think that it's from a combination of having 3 overlayed transparencys and im either under or overexposing.
The last try I did was my best yet. I had about 3" between bulbs and PCB and I exposed it for about 90 seconds. The presensitized boards I was using said 8 minute exposure with flourescents and 60 to 90 seconds with real exposure units.
I accidently turned the image slightly though on my last try so my exposure was crooked and off the board but I went ahead and developed and etched it anyway just to see how it turned out (traces slightly running into each other).
I bought some real "etcher" that you mix with water but just for the heck of it I mixed my own using muratic acid and hydrogen peroxide and it appears to work ok. I am hoping I can just take the etcher back to where I bought it and buy more developer and/or PCB's instead.
The developer instructions said to mix the whole package with 1 liter of water which is about 4.2 cups, and me being the cheapy I am, I visually split it up into 8 parts and bagged them seperately, each one being mixed with 1/2 cup of water when I go to use it. (could also be my problem is my ratios are quite a bit off since visually splitting it up isin't the most accurate way of measuring them out).
I found the process for the developing and etching was taking quite a bit longer then what I read it should take, but the water I used was probably a little cool. I was afraid of using water that was too warm so I think i went the extreme oppisite. I wish I had kept records via a thermometer as I was writing down my trial and error exposure times and whatnot.
I ended up putting my developer and etcher in a bigger tub which had an inch of super hot tap water to speed things up and it made a huge difference in how fast it developed and etched the boards. I could actually see the "wisps" of color after heating up the solutions a little.
I am sure I probably left out some important details and instead gave a lot of unnessary information.
My last try which turned out the best, I accidently ruined when I thought I was done developing it. After I etched it. I used some laquer thinner to clean the remaining developer off thinking it was done before I realized it still had a ways to go in the developer so i dropped it back in the developer (but had already removed the photoresist with the laquer thinner) so i accidently erased all the traces.
The one board I have that actually looks like a semi usable board is not worth taking a picture of since I left it in the devloper for wayyyy to long when I realized my image was upside down and useless and I forgot about it while I worked on cutting the next trial PCB.
Thanks for any advice or tips, and again, sorry for the novel length post I just wrote. (and bad spelling and grammar).
Sorry for such a long post here, hopefully anyone who knows enough to help me does not run out of patience before they finish reading this. I know I will figure this out via trial and error but would prefer to save some money by having an experienced person point out some mistakes.
I finally got to the point where I tried to make my own PCB. I learned a ton but have a few questions, mainly how to tell if your over/under exposing or over/under developing.
I will describe my setup and procedures in as much detail as I can and describe my symptoms, maybe someone has some ideas.
I printed the schematic on overhead transparencys. I read they suck though on some of the website tutorials that I came accross and that I should use vellum or paper soaked in peanut oil. It seems there were a couple of other materials mentioned too that would be better.
I had 3 decent prints as I was experimenting with contrast and other print settings built into the printer itself to try and make it as dark as could be.
I printed it using a multi $100k xerox full color laser printer. When I went to expose my boards I overlayed the 3 good images I had over each other and taped the sides so there was no chance of them slipping. It is a perfect alignment as far as I could see. Bit I am afraid that this cost me some resolution when I exposed the board since the top sheet would cause a slight blur on the board, and I think that may actually be pretty much be the whole problem that I am generally having.
I made a custom exposure unit. I bought some clearance bug zapper UV bulbs from walmart a few months ago during the winter months just for this use. They are 40 watt, about 4" wide and around 12" long, one bulb folded in a tight "U". I wired them to a electronic ballast from home depot. It's just temporary right now, I plan on having two switches, one built into the lid and one outside so it won't run unless the lid is shut, and also having a built in timer so once I get this figured out I will be able to get perfect exposures every single time.
I know im putting out a lot of UV rays compared to just using normal flourescents, but I don't know if it's comparable to a real "exposure" fixture or somewhere inbetween. I covered the whole thing with a thick towel to protect my eyes and I could swear when I poke my hand under I could feel tingling, but it could be my imagination. I didn't keep it under long enough to find out for sure, I don't need skin cancer on my hand
My first 2 or 3 exposures I didn't have enough weight on the glass or something so I had messy exposures. Took me about 3 trys before I realized this was the problem (I was also using crappy PCB's that had been pre-exposed to light because my dogs had chewed up the corner of the board while it was still brand new in the packaging.) I was using these crappy PCB's even though I knew they probably wouldint work so I could figure out what the heck I was doing.
After I realized what was going on I taped the transparency image to the glass and layed it on top of a thick paperback book. That made a huge difference but the problem that I am having is that my copper traces are slightly merging together, which was still occuring even after sandwhiching the image real nice and tight.
I think that it's from a combination of having 3 overlayed transparencys and im either under or overexposing.
The last try I did was my best yet. I had about 3" between bulbs and PCB and I exposed it for about 90 seconds. The presensitized boards I was using said 8 minute exposure with flourescents and 60 to 90 seconds with real exposure units.
I accidently turned the image slightly though on my last try so my exposure was crooked and off the board but I went ahead and developed and etched it anyway just to see how it turned out (traces slightly running into each other).
I bought some real "etcher" that you mix with water but just for the heck of it I mixed my own using muratic acid and hydrogen peroxide and it appears to work ok. I am hoping I can just take the etcher back to where I bought it and buy more developer and/or PCB's instead.
The developer instructions said to mix the whole package with 1 liter of water which is about 4.2 cups, and me being the cheapy I am, I visually split it up into 8 parts and bagged them seperately, each one being mixed with 1/2 cup of water when I go to use it. (could also be my problem is my ratios are quite a bit off since visually splitting it up isin't the most accurate way of measuring them out).
I found the process for the developing and etching was taking quite a bit longer then what I read it should take, but the water I used was probably a little cool. I was afraid of using water that was too warm so I think i went the extreme oppisite. I wish I had kept records via a thermometer as I was writing down my trial and error exposure times and whatnot.
I ended up putting my developer and etcher in a bigger tub which had an inch of super hot tap water to speed things up and it made a huge difference in how fast it developed and etched the boards. I could actually see the "wisps" of color after heating up the solutions a little.
I am sure I probably left out some important details and instead gave a lot of unnessary information.
My last try which turned out the best, I accidently ruined when I thought I was done developing it. After I etched it. I used some laquer thinner to clean the remaining developer off thinking it was done before I realized it still had a ways to go in the developer so i dropped it back in the developer (but had already removed the photoresist with the laquer thinner) so i accidently erased all the traces.
The one board I have that actually looks like a semi usable board is not worth taking a picture of since I left it in the devloper for wayyyy to long when I realized my image was upside down and useless and I forgot about it while I worked on cutting the next trial PCB.
Thanks for any advice or tips, and again, sorry for the novel length post I just wrote. (and bad spelling and grammar).