I have failed once and I then stopped for at least 6 months. I want to do it again.
Therefore I need some guidance in making pcb again. The actual schematic has converted to PCB.
I remembered what I have done last time My step are wrong because I do not get a nice clean pcb at the end of the day.
I printed it out from internet in a laser printer.
made transparency copy of the pcb and cut it a the size of the actual perimeter said 4 by 5 cm.
I have "ever-Muse" presensitized P.C.B.
I used a glass to cover the transparency that covers the "ever-Muse"
I applied strong "flood" light for about 10 minutes ( I do not know exact time that I have apply and I need to find out where is the flood light located since I have not used it for six months.
I remembered I applied some "yellow pebbles and hot water to form a yellow liquid" and also the electrolube- photo resist developer". I bombed the last project.
Perhaps your insect UV source is insufficient. I haven't done PCBs for years, and I used to live in South Africa, where the sunshine is quite strong, but I used to expose using sunlight and didn't have to buy special UV equipment.
You don't even need strong sunlight. In the days when I made my own boards I found 10 minutes of overcast English sky to be enough. I used an old SLR camera to measure the overall illumination so I could make some sort of calibration.
You need to do a test strip like a photographer. Just take a small bit of board and expose different areas for (say) 5, 10, 15 and 20 minutes to find the best exposure time with your lamp.
Possibly there is nothing wrong with you. BUT there may be a problem with your transparency. Most I've seen are not opaque enough for uv exposure. The tracks and pads are not dark enough. Try exposing something solid, say a coin or ? Expose, develop and look at the differences. If your film is too light, the traces will come off in the developer. If the coin shape is present on the board, then you know what the problem is. If the coin pattern is not there, maybe the developer is too strong.
I'd be surprised if the entire board wasn't washed out at that exposure. I started to see overexposure at less than 3 minutes, but I'm in a lower latitude and it was summertime when I tested. In all, sunlight is not a good source - too many environmental factors influencing its effectiveness and availability.
So, what result are you seeing - does the board appear to change at all when you develop it? Aside from the overall bad results, you need to narrow whether it's your exposure or your chemicals.
Among other tricks, warming the chemicals helps them develop much faster (we're talking on the order of seconds before results start becoming visible). But I think exposure is your first problem.
Also, be sure the developer you're using is chemically matched to the PCB coating. I seem to recall there's more than one system, and perhaps you're not using a compatible developer.
Other tips for quality: ensure the toner side of the transparency is in contact with the PCB for best results. And I develop in very low lighting (e.g. 4W nightlight) to avoid affecting the exposure. (Of course, the PCB is also bagged immediately before/after exposure.)
Here are some comments from an old posting of mine with some more details on my testing...
I happened to have an empty picture frame handy, and it made an excellent holder / clamp with glass included (the gap for a photo with a cardboard backer was just right for a PCB with a transparency).
For the source, I used a fixture in my office; it works well enough that I haven't tested further. It's a 21-inch 13-watt under-counter light fixture from Home Depot, with a replacement bulb (a Philips "Home Light Cool 4100K"). Exposure was done 6" from the fixture (for a 2"x2" PCB).
With the diffusing panel left installed on the fixture, an exposure of 5 minutes worked fine, though it was very slow to develop. I've seen the best results with the diffuser panel removed, and an exposure time of ~10-15 minutes).
FWIW, a UV "grow lamp" flourescent fixture did not yield much better results. At least for my purposes, it wasn't worth setting up a special rig when I could use a lamp at-hand.
FYI, I initially tried using sunlight at a 180-second exposure, but the results were badly overexposed. It could be a viable source as well with some testing, but I abandoned it because I realized the source would be too inconsistent (e.g., clouds, time of day - particularly nighttime ;-). Also, I was concerned that the sun was too intense as a source (that the toner on the transparency might not block it effectively at any exposure). So, I opted for a less intense light source (i.e., slower), but gained consistency and control.
Your mileage will vary with your setup (e.g., larger PCBs may require more distance from the bulb for angle and even lighting, and thus a longer exposure). I took a PCB and cut it into 2"x2" sections and exposed under a variety of settings until I got results I was happy with. IIRC, it only took 3-4 cycles to get the settings "dialed in".
When I switched to photo etching, I picked up a packaged kit at the local Fry's Electronics. The kit's handy, and it was about the same price as buying separately packaged chemicals, but also included some PCBs. Here's the manufacturer's site:
formatting link
I've had great results with the photo process, with one glitch. An early batch of boards apparently had scratches in the photosensitive material, which caused cuts in the trace lines. I tried boards from DigiKey (more expensive, naturally) and did not have this problem. I can't imagine it's a regular problem with MG' products, but I wasn't going to keep experimenting to find the good batch. ;-)
Curiously, I just found this on MG's site - it's general instructions for photo etching. They suggest any 18" fluorescent lamp will do, at a distance of 5" for 10 minutes using a glass sheet. Coulda saved me a couple rounds of trial and error...
No shit. I have that problem with MG. It's not to the point where I'd change brands though. None of the boards were seriously effected by the flaw. (Usually just on the ground plane.) I couldn't get the digikey boards to work... likely because I was running low on chemicals at the time.
No. I didn't pursue it with MG. Chalked it up to buying cheap stuff at Fry's. It would've been a problem though, because the traces I was testing were pretty narrow for hobbyist (7-10 mils).
Looking at one of the test boards lying here, there are 1/16" to 1/8" gaps in some of the traces - pretty bad by any standard. Since I used the same transparency for all the tests, it was pretty certainly the PCB.
Anyhow, I've been paying to have PCBs made lately... a more expensive (but easier) fix. The solder mask alone makes it worth the cost when trying to hand-solder fine-pitch SMDs. ;-)
Incidentally, the MG Chemicals did work fine for me with the DigiKey PCBs, though as the chemicals depleted I found myself heating them for best results.
Pardon the very fundamental questions, but making no assumptions here...
Are you sure you're buying photo-sensitive PCBs? They'd come sealed in a light-proof pouch with a protective film that needs to be removed before exposing.
After exposing the PCB, the "developer" solution will cause exposed areas to fall away from the PCB, leaving only bare copper and coated traces. If you never see bare copper, then the photo developer is bad, the photo-sensitive material on the PCB is bad, or they're chemically incompatible.
The etch process uses a separate chemical solution to eat the copper that's exposed. Again, a very noticable process. But from your comments, you aren't making it this far.
Are you sure the stuff you think is developer really is developer? Perhaps you've mixed up the developer and the etchant solutions?
ELECTROLUBE ( order code PRD250) PHOT RESIST Developer. I dipped the exposed PCB down and up at least two dozen times. NO bare copper was found, "no green things" comes out.
I have done exactly what the film instructed even this is first time I saw the film.
formatting link
the rest of the etching process is out the question since I do have a noticable clean clear "BARE" copper PCB.
In the film, he used a day light floursecent lamp , I guess it has 2 lamps and it may a 18 inches. can u confirm this lenght of the lamp?
Or perhaps using positive process boards but using developer for negative process boards?? Or vice-versa??
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)
Time is what keeps everything from happening all at once.
Well, I got a big goose-egg trying to find these products online. Google and Electrolube's site turned up nothing. How old are your materials?
Sounds like some seriously dead materials. Considering the only reference I found isn't even carrying those PCBs anymore, I wonder if you didn't get some really old stock.
No. I use a single-lamp 18" fixture as detailed previously. MG's looks very similar, so I'd guess it has one 18" bulb. See
formatting link
I'd suggest getting some fresh materials (PCB, developer, and etchant), cut up a board (score/break) into small pieces and try several different exposure times. The info I provided before should give a good jump-start. It sounds like you're fighting a loosing battle with depleted / inactive chemicals.
It's really a very easy process once you work out your exposure technique.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.