Hand Applied Solder Mask

[Noggin]

I need some help finding a hand applied solder mask to cover up a via which is too close to a switch as it occasionally makes contact with a carbon pad on a membrane. This will be used on a commercial product until the corrected boards come in. So far, all I've been able to find is this but I'm a little worried that the datasheet states that this is peelable. I'd like something more permanent. I may also have to go with something like a mylar tape...

The boards are already assembled, so letting the PCB manufacturer reapply the solder mask and then rebaking is not an option.

Edit: Maybe something more like **broken link removed** is what I should look at using, its probably clear though which is a negative

 

[dknguyen]

Yeah, I'd just go with conformal coating. Most are clear I think. Unless you use epoxy or find some that isn't. But yeah, why is clear a negative? I would think it was a positive?

As far as an actual solder mask, at least what's used on a PCB at the end, isn't something you can do by hand so they don't realy sell it like that.

And you should definately not use the TEchspray solder mask. THat is meant to be removed after a solder job is finsihed so it has been designed not to be permanent.

 

[Boncuk]

Solder mask

You might try "Kontaktchemie" finish. It looks like clear laquer and it is sprayable. Apply three thin coats of it with the board perfectly horizontal.

According to my experience it won't even crack in hot environment (80deg/C +) within an 18 years period.

Of course there is a disadvantage to it. Tracing malfunctions you really have to poke holes through it to be able to measure. I made the probes of tailor's needles.

 

[Noggin]

Thanks for the responses. Clear is bad because this is hand applied and I'd like the worker to be able to easily see if it is covered or not. I've also found a conformal coating pen which I'm hopeful will work well. I can't go with a spray on because I need to cover the via and only the via as the area immediately surrounding the via cannot be covered. I'm also about to look for some mylar tape, hopefully thats not too difficult to find.

 

[dknguyen]

I don't know any brush-on conformal coatings that have colourant, but a lot of sprays and pens (like the ones from MG Chemicals) have UV glowing stuff in it.

 

[mneary]

I would consider Kapton tape. See this link. https://www.goldmine-elec-products.com/searchprods.asp

 

[3v0]

Perhaps a dab of hot melt glue

 

[Noggin]

I would consider Kapton tape. See this link. https://www.goldmine-elec-products.com/searchprods.asp

Yeah, I bought some kapton tape and I imagine it'll work great. Only problem is the stuff I bought has a shelf life of 12 months, which brings up the question of whether or not the adhesive may start to fail at that time. However, the board will be oriented such that gravity will work with it, not against it. And I found something else that was thinner than kapton, better adhesiveness (is that a word?), and actually listed dielectric strength. I picked up some of that too.

And hot glue is too thick and doesn't stick to PCB's very well in my experience. This is a commercial product and while I'm not happy with putting tape or hand applying some sort of soldermask, I need some sort of feeling that it will last for 5+ years.

Thanks for the help and suggestions, I think something I've purchased today should work for me. I appreciate it.

 

[jpanhalt]

How about old fashioned fish paper applied with a permanent, double-sided tape. I have seen that approach inside of a lot of products, including batteries and PCBs that are close to a metal frame. You may want to check out McMaster-Carr, as it has a large selection of 3M tapes. I've never had much luck on the 3M site, unless I know almost exactly what I want or can find in my area before I go there. John