Can I use dry film photo resist for pcb as the solder mask ?

[BravoV]

I'm new to this film photo resist pcb and was thinking about doing a hobbyist grade pcb, so nothing serious, and aware that there is a specially made dry-film photo resist just for solder mask.

[BravoV]

Or ... anyone know where to buy those green photo resist film for solder mask ? Its so hard to find. 

[M. András]

http://www.megauk.com/dry_film_laminators.php
or search on ebay for dry film photoresist, or "dynamask"

[BravoV]

Thanks, unfortunately can't afford to purchase it from UK, while fleabay doesn't carry many alternative suppliers, currently only one has it and with quite an expensive s/h charge.

Looks like this thing is new isn't it ? Can't find it in Chinese market like at Aliexpress, most of them are in liquid form like this.

[M. András]

just posted a source what i know of and the name of the thing which can be used for searching on ebay, from megaelectronics the shipping to here is still a huge amount, so i can imagine what it would cost to ship overseas etc,
maybe? http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&_nkw=dry+solder+mask&rt=nc
or http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&rt=nc&_nkw=dry+film
http://www.ebay.com/sch/i.html?_odkw=dry+film&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313&_nkw=dry+film+solder&_sacat=0

[ptricks]

You can use some dry resist for solder mask, just depends on what film you have. 
Tear off a small piece and set your iron on 300C and see how it reacts to the iron.
For one off boards I sometimes use a thin coat of protective spray coating, then go back and scrape off the places I need to solder.
http://www.krylon.com/products/crystal_clear_acrylic/

[mamalala]

Hi,

you can get the resist for reasonable prices at Octamex:

http://www.octamex.de/shop/?page=shop/browse&category_id=5848924494118370762daa6f026e22f7&/PCB_Laminate_/_Dry_Film_kaufen.html

"Tenting" is the regular dry-film resist used for etching, "Dynamask" is the solder-stop.

You can use tenting as a simple solder-mask if you want, but there are some drawbacks. First, the Tenting is very thin. Also, it does not stick that well to the copper. This means that you can rather easily scratch it or chip away parts of it. Under normal light the Tenting will look blue-ish. I have no idea about heat-resistance of that stuff. It would be OK for hand-soldering, but no idea about reflowing or hot-air. Also, there might be issues with long-term stability. That stuff is slightly hygroscopic. So it's probably a no-go for high-impedance stuff anyways.

The Dynamask solder-stop is processed slightly different. After laminating and exposing, it must sit in the dark for a while. After developing it, it must be cured for quite some time either under UV or in an oven (or both in sequence). This is what gives it the strength. It is also much thicker than the Tenting.

Greetings,

Chris

[BravoV]

Thanks for the helpful replies ! 

The only reason I'm looking to put the solder mask at my one off pcb is solely to avoid bridging when soldering those PITA tiny pitch pins. 

Looks like these solder mask film vendors are mainly in European countries only ?

[PlainName]

avoid bridging when soldering those PITA tiny pitch pins

Lots of flux might solve that for you. On TSOP and the like a common method of soldering the pins is to run a big bit loaded with solder up the pins in one go, making like an inverted travelling solder bath. Flux is the magic ingredient that makes it work.

[nukie]

Yes flux is the key, I always thought soldermask is for cosmetic purpose and helps prevent bridging during automated soldering.

The liquid solder mask from those Chinese vendors probably a copy of Japanese Taiyo. They work but technique need to be right. It has to be spread very thin otherwise it will not set regardless of the UV exposure times. And you will need to oven it. Experiment to find the right formula. I have a two year old tube stored in a dark bag in my fridge it still works. This type of mask dries matte instead of shiny. Appearance is similar to some of those CRT mainboard made in the 90s.

Theres a gentleman from Czech Republic on eBay he's selling dry type soldermask and also photoresist, I use them all its pretty good. Yes dry soldermask is not cheap, and they have a shelf life so don't buy too many at one time.

[BravoV]

Thanks for the infos Nukie, noted.

Talking about the photoresist film, the one I have here is blue coloured film, not the green one like those sold by Czech seller.



Produced by a Korean company called Kolon Industries -> http://www.kolonindustries.com/Eng/Product/product03_09.asp

[Flávio V]

Well, i am not sure if it would be a good idea to use it, since it is very thin and does't is very protective, i use it to create silkscreen and to etch....