farnell photoresist experience

Spray photoresist is a waste of time for all but the lowest-resolution PCBs unless you have a cleanroom and a lot of time to practice. It's next to impossible to get an even coating, free of dust. Use the pre-coated stuff - the extra cost is well worth it. For lots of info on making good quality PCBs, see

I have in the past used Kodak's photoresist chemicals.

It's very messy indeed. It requires alot of trouble to get even half decent results.

Graham

Making your own PCBs is giant waste of time, it's messy, innacurate, and you'll never get plated through holes. Just send your artwork (you are using a PC here right?) to any number of online proto PCB shops like APC, Olimex, Futurlec, etc... If you like playing with copper and chemicals, may I suggest taking up a stained-glass course instead?

Lots of bad things happened many hundreds of years ago.

There was nothing special about Jewish persecution. Catholics and Protestants has their troubles too depending when and where they lived.

Graham

I used KPR also and had zero problems after replacing their "developer" with (now banned) TCE. I found a repeatable and reliable way to get a thin and uniform coating by adding CP benzine. I even made my own vapor degreaser using a 1-gallon can, copper tubing, a 100 watt heater and fiberglass insulation. With that, i could make a quart of TCE last a long time.

Most of the boards i made were 2-sided, but not plated thru; i arranged the traces and vias to minimize those that had no part leads. 20 mil traces with 20 mil spacing was easy and that was 20 or more years ago.

Yes, I recently used a can of PRP200 and I found several deficiences compared to using Kinsten pre-coated board.

Firstly, it is damned expensive around AU$30 per can.

It is difficult to get an even coating and dust particles can be a real problem. And drying the board after spraying takes considerable time using a hot air gun in the semi-dark.

Exposure time is extremely long compared to Kinsten pre-coated. Kinsten takes me 85 seconds exposure but PRP200 takes 5 min in the same light box. Anything less and the developer just takes all the resist off.

The propellant in the can ran out before all the resist had been used.

The results for PRP can be excellent but Kinsten pre-coated is far more reliable and the results are repeatably excellent.

I don't have their catalogue handy, but if it's made by Electrolube, your results might be variable. Some years ago, it was good, but it was a green colour. About 5-6 years ago I bought another can, and it was distinctly blue-green, and it was crap. Results were very variable but generally poor, even with careful process control.

I have gone back to my small remaining stock of KPR, it has to be at least 30 years old, but still works good. I have also had good results from the blue "Press'n'peel" transfer paper, although I only had one small free sample sheet.

Barry Lennox

The postive pre-coated boards from Farnell are excellent. Well, the FR4 ones are excellent, the CEM1 phenolic base ones are crap, as all phenolic base is.

I use a laser printer transparency, getting the right type of tranparency to avoid pinholes is the key. You can print out to copies and stack them to get it extra dark. Make sure you put it toner face to the board to avoid undercut.

I expose mine for 15min on a home made light box, or 5 min in the Australian summer sun.

Excellent resolution, I can easy get 8thou/8thou, and 6/6 is achievable too.

Dave :)

Inaccurate? I can get 6/6 resolution double sided no problem. No plate through, but perfectly adequate for a prototype.

Can you get the board made and in your hands within an hour? That's a HUGE benefit of making your own.

Dave :)

I can confirm that. The old stuff worked quite well, but the current stuff is useless. I asked Electrolube about this at a trade show a couple of years ago and they confirmed that they had changed the formulation, and it no longer worked very well. Probably something to do with RoHS.

I use resist-coated CEM1 material from Farnell and other suppliers:

and can do 10/10 and 8/8 mil PCBs at home with very few problems.

Leon

CEM1 isn't phenolic, it's a fibreglass/paper composite. I find it works just as well as FR4 for most purposes, is cheaper, and *much* easier to cut and drill. The resist is the same as the FR4, AFAIK, which is the main thing.

Leon

Use tracing paper - works much better than transparencies - get the thick stuff

- 90gsm or more to avoid crinkling.

Incidentally, these rivets are really good for through-plating - you don't need the punch tool - you can use the rivets on their own with tweezers.

stuff - 90gsm or more to

The thin stuff is OK, I cut a piece to size and stick it to an ordinary sheet of A4 paper with a piece of masking tape. I get better results with Mega Electronics JetStar film in an inkjet printer. It's expensive stuff, though.

Leon