Advice on photosensitive dry film - Page 1
Forum section: electronics / beginners

author: antenna
author_rank: Frequent Contributor
timestamp: December 30, 2021, 10:46:04 pm
content: The only PCB experience I have is drawing the traces my hand with acrylic paint using a fine paintbrush used for fingernail decoration before etching. I finally got tired of that and trying to cut them by hand with a dremel, so I ordered new toner for the printer, overhead projector sheets, and a roll of UV film. I do not have a lamination machine or a clothing iron to apply it to the boards. As I anxiously await for those items to arrive, I am contemplating my options for adhering the film to the boards. I thought about heating an aluminum block and using it like an iron and I've though of using my heat gun but wonder if pressure is necessary. Does anyone have some MacGyver-type advice other than buying a lamination machine that will get me by? Maybe knowledge on the best temperature, duration, and pressure to apply this stuff to my boards?Thanks!

author: rob77
author_rank: Super Contributor
timestamp: December 30, 2021, 10:55:43 pm
content: the cheapest office laminator does the job nicely. i bought mine for 20Euro , only modification i did was to cut the plastic housing so a PCB can go through.

author: ogden
author_rank: Super Contributor
timestamp: December 30, 2021, 11:15:58 pm
content: Generic household iron is good enough. Clean PCB surface with steel wool and (isopropyl) alcohol. Switch steam off, set temperature to synthetics, wait till iron ready. First preheat PCB through (smooth) paper, then put UV film on PCB and apply heat again, through paper. You may need to experiment with temperature because irons differ unfortunately.

author: Cerebus
author_rank: Super Contributor
timestamp: December 31, 2021, 12:39:20 am
content: Quote from: rob77 on December 30, 2021, 10:55:43 pmI've found that for some reason the cheaper the laminator the better it is for dry film. I've used/tried several and by far the bestfor that jobwas a bargain bucket one. The quality ones seem to baulk at having 1.6mm PCB stock fed through themanddo a good job of laminating as well, on the cheap ones it just breezes through.

author: antenna
author_rank: Frequent Contributor
timestamp: December 31, 2021, 02:16:23 am
content: Thanks for the replies. I guess I'll break down and order a laminator being a cheap one is ideal. I appreciate all the advice.

author: sleemanj
author_rank: Super Contributor
timestamp: December 31, 2021, 04:08:44 am
content: Hot air reflow tool works, a hair dryer probably would, they are a bit awkward though.Clothes iron is better than laminator IMHO, but each to their own.See my tips:https://sparks.gogo.co.nz/dry-film-tips.pdfAlso Big Clive has done a few videos in the past:

author: Siwastaja
author_rank: Super Contributor
timestamp: December 31, 2021, 09:34:34 am
content: +1 for cheapest office laminator.Failing to obtain a cheap laminator, another classical method which certainly works is this:1) Evenly spray a small amount of water on the PCB (if unsure, use distilled; tiny amount is enough so it won't cost you much. We used tap water without problems but we have soft water with little calcium in it.)2) Remove one of the protective films - using two pieces of tape at the corner helps separate the films.3) Put the dry film sticky side against the PCB4) Use a clean (to avoid scratching with particles) squeegee, you can even use it wet to make it slide smoother, applying significant force, to drive all the water (and any air bubbles) out between the film and PCB. The end result should look completely dry and "laminated".5) To actually make the film stick to the board, heat in oven, I forgot the temperature and time, google for the procedure. I guess it was like 70-80 degC for maybe 10 minutes? Hair dryer could work as a substitute. Not too hot.But the cheapest office laminator is obviously quicker. The trick is, for large panels, don't remove all the protective film at once. While the laminator eats your PCB, slightly pull back on the protective film to remove it little by little. This helps avoid wrinkles. But most people do small PCBs, in that case it doesn't matter.

author: antenna
author_rank: Frequent Contributor
timestamp: January 10, 2022, 04:34:58 am
content: Many thanks to everyone here who gave me advice! I just etched my first board, and although it has a few minor issues, the board should be usable for the active RF probe I want to stick in a copper tube. I used mspaint to make the transparency (used 4 stacked together), a hair dryer to heat it, 24" black light to cure it, boiled/cooled baking soda as the developer and some copper chloride/HCL etchant. I am very happy with how it turned out!

author: rob77
author_rank: Super Contributor
timestamp: January 10, 2022, 03:41:40 pm
content: Quote from: antenna on January 10, 2022, 04:34:58 amfew more hints:- best transparency is a polyester film for laser printers - print at 1200DPI with eco mode disabled on the printer.- if you place the transparency "toner down" so the printed side touches the photoresist , the image is sharper.- if you stack multiple transparencies to increase contrast , then use some universal oil to make them stick and increase contrast. i'm using oil even between transparencies and the photoresist.- if you use strong UV source for a short period the results are better.- i never boiled the washing soda and worked beautifully (using riston photoresist an dynamask soldermask film)- use a less aggresive etchant HCL+peroxide is way to aggresive for the photoresist. - ferric chloride or sodium persulfate are much better.attached a picture of some boards i made.

author: Cerebus
author_rank: Super Contributor
timestamp: January 10, 2022, 04:55:01 pm
content: Quote from: rob77 on January 10, 2022, 03:41:40 pmYou probably live somewhere with soft water. Use soft water or deionised and there's no problems, use hard water like I have here in London and you get some calcium salts thrown out of solution forming a fine, cloudy suspension. I don't think boiling would be any particular help (unless one was boiling and cooling water beforehand to reduce the hardness), but allowing the solution to settle and decanting, or filtering it, is pretty much a necessity if using hard water.

author: antenna
author_rank: Frequent Contributor
timestamp: January 10, 2022, 07:42:52 pm
content: Quote from: rob77 on January 10, 2022, 03:41:40 pmNice boards!!! Thanks for the oil tip, I will try that. My printer is a Canon ImageClass MF232w (not the best laser printer out there) but with the contrast to max, it did ok. I think I had the DPI in mspaint set to 120 so that 4 black dots for pads with 2 white dots between was perfect for SOIC-14 chips. It worked out ok.I did buy washing soda and will try that next, but the reason I boiled my baking soda was to convert it from the bicarbonate to the carbonate (washing soda). When the baking soda stops fizzing when stirred in boiling water, it has turned into washing soda (and you can tell its a stronger base with the lye-like slippery feeling on the skin). Just making do with what I had.Same with my copper chloride etchant... I did not have peroxide in it. I made it by dissolving copper in hot 34%HCL and using an aquarium air bubbler to oxidize it from the copper II chloride to the copper I chloride (took a couple days with the aquarium bubbler, but now I have 2 liters of it). Etching with that is fast compared to the peroxide-vinegar-table salt mixture I used to use. When I use it, I just dump it back in the bottle, and when it gets dark, I lower the pH and bubble more air through it. It is an etchant that not only recycles itself, but creates more etchant as you use itMy black light is slow and I was going to try the girlfriends UV fingernail paint hardener next. If the fingernail hardener don't work faster, ill put a lens on the $4 UV laser i found on ebay marketed as a purple "cat toy" laser. I originally thought it was ok for the cat being nice and dim until it hit my orange work shirt!

author: antenna
author_rank: Frequent Contributor
timestamp: January 10, 2022, 08:04:17 pm
content: Quote from: Cerebus on January 10, 2022, 04:55:01 pmI didn't boil washing soda, I boiled baking soda to turn it into washing soda. But now I have a box of it. I use distilled water because we have a big mineral problem here too.

author: rob77
author_rank: Super Contributor
timestamp: January 10, 2022, 11:24:10 pm
content: Quote from: Cerebus on January 10, 2022, 04:55:01 pmnow i get your point why the boilingactually i always use distilled water for the developer solution as i do for other pieces of chemistry (copper plating , electroless tinning solution..etc..).i use tap water only for rinsing after etching and for the sodium hydroxide solution when stripping the photoresist film after etching.

author: Cerebus
author_rank: Super Contributor
timestamp: January 11, 2022, 12:21:22 am
content: When to use tap water, when to use deionised/distilled, and when to get your water straight from the dispenser nozzle on the ultra-pure water system is always a balancing act.If Iknowthat it it won't mess up the chemistry of what I'm doing I'll use cheap highly available tap water unless I'm in someone else's lab with an unlimited supply of purified water in which case I'll always use that. If I know or suspect that tap water will mess up the chemistry then I'll go with with everyday purified (so deionised or distilled), as I also will if I want to guarantee no possibility of residues on drying. So quite a few things get rinsed in tap water and then get a final rinse with sprayed deionised water. I fortunately never get into the realm at home where I might need ultra-pure water, although I have rarely done things where freshly purified water (without carbonate ions absorbed from atmospheric CO2while standing around) is the medium of choice (e.g. making up silver nitrate solution although that's something I haven't done in years).

author: antenna
author_rank: Frequent Contributor
timestamp: January 11, 2022, 03:15:27 am
content: Quote from: Cerebus on January 11, 2022, 12:21:22 amWhy, did you get tired of the discolored fingers or did the novelty of an easy kaboom wear off? lol just kidding. For me, the novelty wore off.Uh oh, i'm deviating from electronics again lol

author: Cerebus
author_rank: Super Contributor
timestamp: January 11, 2022, 02:59:55 pm
content: Quote from: antenna on January 11, 2022, 03:15:27 amNo, photography. I can't remember when I last did any wet chemistry photography, and it's a very, very long time since I've made any of my own photosensitive materials which is what the silver nitrate was a starting point for. My stock of silver nitrate, which I used into the 90s, was passed to me by my mother (an analytical chemist by trade) who originally got itduring the second world war.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 11, 2022, 06:41:25 pm
content: Yeah, I did those photo things too, including making emulsions. I even made my own silver nitrate (it's pretty expensive to buy!), dissolving silver in nitric acid. It's an exothermic reaction which fills the fume hood with those beautiful, orange-brown fumes, which I read afterwards, would have killed me painfully after a few days if that fume hood wasn't up to the task. It was.In any case, I managed to do some pretty decent orthochromatic (sensitized to green, in addition to the natural blue response of the silver bromide-iodide emulsion), approximately ISO 25, emulsions with small grain and good resolution. Was even able to coat those on polyester base treated with a DIY high voltage corona discharge contraption which also nearly killed me, usable in a normal roll film camera. Good memories.Luckily, water in Finland is mostly very soft - depending on location, it's either soft, or even softer. Ignoringactuallysensitive processes, it's good for almost any use, including those where people usually recommend deionised or distilled water.