How can i mask a PCB?

[holax12]

Hello,

I just successfully etched my first PCB, it looks awesome and am so exited about it but the only draw back i have is how to add the soldermask layer coat.

How can i shield the solderpads and apply the coating? Please share your idea or how it is been done. Thanks

 

[lilimike]

I think THIS is the typical way of doing it to make it right but then if you are making your own boards to save money this defeats the purpose.

If your goal is to make it last you can always apply solder on all traces.

At one point I was going to buy a can a lacquer at a surplus store for $15 and try to cover the pads with stickers while I spray the board and remove the stickers before the lacquer dries but I turned things around since I can get 3 boards double layer with solder mask and silk screen on both sides for a little more than $20. Of course if your boards are more than a few sq. inch its a different story.

Making my first few boards was interesting though but I never got to the solder mask.

Mike

 

[kjennejohn]

Three methods come to mind:
1. Install the components and spray the board and parts, top and bottom, with conformal coating. Instant water proofing.
2. I have seen a special paper set, in green (for solder masking) and white (silkscreening), that you print on from your laser. You then iron on the prepared portions. I can only think that registration is a *****, but this has been done before. This is the same idea for iron-on traces masking that you do before etching in your tank.
3. There is a powder you dissolve in cold water and immerse the freshly etched board in. This is a tinning compound which reacts chemically with the exposed copper to leave a thin tin coating.

I don't remember what the paper is called or who sells it. Same for the tinning compound. There's been plenty of discussions in these forums about making boards. No doubt someone will come up with the info, or you can do a search.
Have a nice project.
kenjj

 

[Blueteeth]

For aesthetics, it is extremely difficult to achieve similar results to professionally made boards, although some DIYer's have done it using UV activated compounds, and exposure. Very similar to photosensitive PCB's except the coating disolves in a chemical bath when exposed to UV.

However, as previous posters have mentioned, if you just wish to protect the copper from corrosion, I have used two methods:
1. Chemical tinning solution. Clean your freshly etched board, and dip it in tinning solution, after 10-20 minutes all the copper is tinned. This not only protects the copper from corrosion, but also makes it easier to solder to. Looks pretty cool too!

2. Conformal coating lacquer: If you use the 'non acrylic' one, a light coating protects the traces from corrosion, and can be soldered through. That means you coat the entire board, pads n all, soldering melts it away, but stops it running across traces. Although I prefer tinning, this prevents all corrosion (even tinned traces oxidize after a while).

The only downside with a conformal coating is, if you wish to electrically test the board with a multimeter, the coating must be scraped/soldered away for you to get an electrical contact.

As for silk screening, on single sided boards, my preferred method is to print off the silk screen pattern onto paper, line it up, and glue it to the non-copper side of the board. Punch all the holes through with a needle, then spray with an acrylic based conformal coating... the acrylic one will not dissolve ink/toner on the paper. You end up with a shiney white board, with black 'silk screen' which, from a foot away, just looks like a white PCB.

Blueteeth

 

[3v0]

You do not need a soldermask to solder your DIY PCBs. The solder will not stick to the substrate and is pulled to the copper by surface tension.

If you want the board to look like it is professionally made you can spray it semi transparent green lacquer. I have not tried this.

For non SMD boards I spray a very light coat of clear lacquer just after etching. It keeps the traces from oxidizing while building and handling. The heat of the soldering iron drives it off. After soldering I add a heavier coat or lacquer or chimerical conformal coating. If it is a one sided PCB I use toner transfer to add graphics to the top side. If I want the board to look nice I add white paint prior to the graphics. I am thinking this is crylon fusion paint.

Note that you can build a PCB without any coating. But I like to see the copper stay as bright as it was after etching/cleaning. It does take a bit longer to solder a joint because the iron has to drive off the coating. A very light coating is gone in a fraction of a second but it is noticeable.

The https://www.pulsarProFx.com website has some good information on toner transfer even if you do not use their products.

Having said all that. I love to be able to make my own PCBs but they will not have through holes or look as nice as the professional PCBs.