# How to attach a paper screen to a DIY PCB?

For poor people who can only afford paper and not silk, a home brew silk screen can be inkjet printed onto paper and then glued onto a PCB. Component legs will be poked through the paper. So I have a PCB like:-

and want to add my paper screen like:-

The large multi pin package towards the middle is digital, clocked at 16MHz. There are also some analogue voltages about in the mV and kHz ranges.

Photo mount type stuff is my instinctive choice of glue, but might there be issues with capacitance /resistance? What type of adhesive might be suitable to glue the paper to the PCB? Is there an electronics glue?

Paper can have a pretty low resistivity value if the relative humidity is higher. I read somewhere that it changes downward by a factor of 1000 going from about 20% to 60%, for example. Still may not be any problem. But since you are worrying about the glue, I thought I'd throw that in just to give you something more to worry about.

You would want an "electrically resistant" epoxy or adhesive. For oddball electronics situations like this, one place I consider is Cotronics Corp. I use their products already and they are good stuff to have around, at times. In this particular case, you might consider their Electrically Resistant Epoxies or their Electrically Resistant Ceramic Adhesives. If I were buying, I'd probably would try out the first link to start, though I'd be curious about how well those from the second link might also work.

You should consider contacting them directly to ask. Chances are, they can recommend something more specific.

• I hadn't considered conductivity of the paper wrt humidity. Some circuit stability of the analogue components is desirable. This might rule out my scheme entirely. Thanks a bunch ;-) Oct 21, 2016 at 2:24
• @PaulUszak I just did a search and found this link: madsci.org/posts/archives/2003-05/1052420610.Ph.r.html (However, the units cited there don't make sense. Sheet resistance is in $\Omega$, not so far as I'm aware in the units shown on that site.)
– jonk
Oct 21, 2016 at 2:41
• Ohms per square centimeter is a reasonable unit for that type of measurement. They could drop the centimeters, though. The resistance will stay the same whetherit is a square centimeter, a square meter, or a square cubit.
– JRE
Oct 21, 2016 at 5:57
• ! What if the paper screen was sprayed with conformal coating once all the components had been affixed? Oct 21, 2016 at 22:15
• @PaulUszak You said you wanted to just punch through the paper with the parts. (Okay, you said "poked.") This would seem to leave haphazard paper shards, many touching the pins/wires/etc. Paper is all a lot of tiny capillaries. I'm not sure how a conformal coating would operate there -- very hard to guess at that. I doubt you will find someone here who knows for sure and has tried it. So I suppose you could just try it and take some measurements before and after? Let us know? I'm actually curious. But I don't know, myself.
– jonk
Oct 21, 2016 at 22:36

Rather than glue the paper to the perf board, consider using a toner transfer method to transfer just polymer toner from a laser printer or photocopy of an inkjet print to the board. There are some approaches that use inexpensive coated paper. I have tried this and it works, however the toner will come off with solvent rather easily.

There are guaranteed electrically insulating adhesives, mostly silicone or epoxy based but probably not easily or inexpensively available in consumer packaging. You could try small amounts of two-component epoxy or you could test a solvent (not water) based spray adhesive such as 3M 77.

The electric properties of glues are much better than those of paper. The pcb base material is made of glas fibers and epoxy, you may use an epoxy glue. But I would prefer a heat resistant plastic film to print on. You have to drill holes in the film for the parts pins. I fear making holes in the film is too difficult and time consuming, therefore this idea is not practicable.

• Note that in many contexts, the term "foil" generally denotes thin sheets of metal, which the OP might find confusing. Thin sheets of dielectric materials are generally called "film". Polyimide (a.k.a. Kapton) is one commonly-used heat-resistant film material. A sharp awl will make the holes easily enough. Oct 21, 2016 at 9:46