I didn't realise this material existed up until now. The silkscreen industry uses the same photo transfer techniques as the PCB prototyping industry, but since it's a much bigger market they have specific transparency materials designed to absorb a LOT of ink deeply from inkjet printers, but still pass UV light for exposing the image.
The material is available on ebay if you search for the keywords:-
inkjet screen printing film
Unlike the traditional overhead projector transparencies that are very clear, the screen printing film is very translucent with a milky opal sheen. This is due to the thicker layer of the coating that absorbs the ink. It absorbs it so well that it comes out the printer virtually touch dry and ready to use. The definition is also super detailed with no bleeding or smudging.
It also seems very resilient to being placed printed side down on the laminate. I had an issue with one of the overhead projector films losing ink and coating onto the PCBs photosensitive layer.
At the same time I also tested a material called inkjet vellum, which is basically a thick tracing paper. It came from an ebay craft seller (search for inkjet vellum) and to my surprise it took the dye based ink very well. It didn't fare so well with the pigment ink though. I think this is down to the larger particle size of the pigment blocking the papers pores.
Also note that the dye ink has visibly penetrated deeper into the screen printing film than the pigment ink, probably due to the particle size again.
This is all good news. It means that the common dye based ink is actually better suited to making the transparencies with these materials.
Neither of the materials I tested was detectable by the EPSON optical paper detector. I had to feed the sheets through in a carrier sheet with about half an inch (12.5mm) folded at the bottom to grip the film and make it visible to the printer. If you do this, make sure you print well beyond the folded lip to avoid jamming the print-head against the folded area.
In the video I reference the lifespan of the developer solution. I recommend using sodium metasilicate as a developer. You can use common caustic soda (sodium hydroxide) but the latter is more volatile (and destructive) and also has a very short usage life. The sodium metasilicate (water glass) has a very long working life and can be used repeatedly until it slows to the point you want to make new stuff up. The mixing ratio is 12.5g in 250ml of warm water.
As before I used the printers in a forced mode to produce a heavy black image. It was done with the matte photo paper setting and the colours adjusted to cause a high contrast image. Modern printers may have more paper settings that let you specify how much ink is laid down.
Another interesting find during the making of this video is that the cheap ebay ultraviolet nail varnish curers that use a cluster of four fluorescent lamps do a good job of exposing the film, but the built in two minute timer is maybe a bit too long. (It's hard coded in software.) I'd recommend experimenting in the 1 to 1.5 minute region, although that will depend on the quality of your transparency and the sensitivity of the laminates coating. The cheap ebay unit actually exposes the PCB material faster than my big industrial tubes-in-lid unit.
The material is available on ebay if you search for the keywords:-
inkjet screen printing film
Unlike the traditional overhead projector transparencies that are very clear, the screen printing film is very translucent with a milky opal sheen. This is due to the thicker layer of the coating that absorbs the ink. It absorbs it so well that it comes out the printer virtually touch dry and ready to use. The definition is also super detailed with no bleeding or smudging.
It also seems very resilient to being placed printed side down on the laminate. I had an issue with one of the overhead projector films losing ink and coating onto the PCBs photosensitive layer.
At the same time I also tested a material called inkjet vellum, which is basically a thick tracing paper. It came from an ebay craft seller (search for inkjet vellum) and to my surprise it took the dye based ink very well. It didn't fare so well with the pigment ink though. I think this is down to the larger particle size of the pigment blocking the papers pores.
Also note that the dye ink has visibly penetrated deeper into the screen printing film than the pigment ink, probably due to the particle size again.
This is all good news. It means that the common dye based ink is actually better suited to making the transparencies with these materials.
Neither of the materials I tested was detectable by the EPSON optical paper detector. I had to feed the sheets through in a carrier sheet with about half an inch (12.5mm) folded at the bottom to grip the film and make it visible to the printer. If you do this, make sure you print well beyond the folded lip to avoid jamming the print-head against the folded area.
In the video I reference the lifespan of the developer solution. I recommend using sodium metasilicate as a developer. You can use common caustic soda (sodium hydroxide) but the latter is more volatile (and destructive) and also has a very short usage life. The sodium metasilicate (water glass) has a very long working life and can be used repeatedly until it slows to the point you want to make new stuff up. The mixing ratio is 12.5g in 250ml of warm water.
As before I used the printers in a forced mode to produce a heavy black image. It was done with the matte photo paper setting and the colours adjusted to cause a high contrast image. Modern printers may have more paper settings that let you specify how much ink is laid down.
Another interesting find during the making of this video is that the cheap ebay ultraviolet nail varnish curers that use a cluster of four fluorescent lamps do a good job of exposing the film, but the built in two minute timer is maybe a bit too long. (It's hard coded in software.) I'd recommend experimenting in the 1 to 1.5 minute region, although that will depend on the quality of your transparency and the sensitivity of the laminates coating. The cheap ebay unit actually exposes the PCB material faster than my big industrial tubes-in-lid unit.
Hi Clive, I'm thinking about building a uv pcb light exposure box, I wonder if you could help me out with a bit of info, what type of let's and at what wavelength and how many and what wattage? Would be forever grateful if you could help kind regards Steve Gordon.
enjoying these videos tonight! <3
The UV silkscreen film sounds like a great way to go for inkjet printers. Just ordered some. Thanks Clive!
I need A 3 transparency CLEAR FILM for Laser printer to be used in exposure for photo etching. I dont seem to find any. Not for Inkjet. I have Laser. Please help
I remember Ferric Chloride 'tatoos' from Technical College days. They could last months!
Those methods can used to etch pcb for hobby and DIY projects can't get professional pcbs good for DIY projects I tested more had small defects
This procedure done in my wet side of my old darkroom. There are already ferric chloride stains on the floor, sink, rinse pan and counter from my color photo days. That's in the bleach/fix part of the color film development process. Photo scanner and old computer replaced the enlarger on the dry side.
I used the older quick dry rough surface HP transparency film with an Epson photo printer recently with the max ink settings. Settings: Ultra presentation paper matte, high speed off, black/gray on. I used LED shop light mercury replacement T-8 tubes around 5000K kit for my seedling starting using the same UV emulsion. Four, 4' tubes, 10" from lights in an old photo proofer for 8-10 minutes. The same developer solution warmed up to above 90 degrees F took less than 20 seconds to develop and plunged in cold water to stop development, a tip I found online. Ferric chloride etchant vessel in warm water speeds up the etching. Detail was fine with most of the .01" PCB border visible after etching I used in the CAD program. It sure beat the old 1970's Mod blacklight I was using!
Hi Clive! Just wanted to mention that the one time I tried etching a board with a photosensitive coating, the best material I was able to find in my local box store was bog-standard tracing paper. Not especially transparent (about the same transparency as the vellum used on wedding invitations) and extremely non-thirsty paper, so the contrast was only a couple orders of magnitude, but I was able to get good prints with my printer's high quality setting and ink saturation dialed way down. My exposure rig was a CFL floodlamp in a clamp fixture. Once I locked down the lamp distance to get good coverage over a fairly large board area, I printed a test pattern similar to yours, snapped off a strip of the board, and had a shutter (I think it was just a piece of chipboard) that I slid a half inch every 30 seconds. The project itself was duff due to several design errors on my part, but the vellum and etching (I was experimenting with muriatic acid and hydrogen peroxide) worked splendidly. If I ever feel an urge to do some home etching again, I'll probably go with the same vellum (maybe with a panel of near-UV LEDs for the exposure), your squeegee-on photoresist, and vinegar/peroxide/salt as an etchant…but really, I doubt that will happen in the near future, as quick-fab prototype PCBs are so readily available, and I have a pile of perfboard that can handle most things I might need to lash up by tomorrow.
Can you make a tutorial about create transparant film like that?
Apparently you can't get the Seno GS anymore. Probably had someone(s) use it incorrectly and got burned.
after UV Whats devoloper solucion ?
bigclivedotcom did you check your results under microscope ?
If dye based ink seemed to penetrate deeper into the film wont it cause refraction and soft edges ?