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Questions relating to designing PCBs
By Chip Douglas
#30060
Aside from acrylic paints like testors, a company called LPKF makes a product called ProMask which is a 2-part epoxy that you mix together and roll onto the pcb and bake it.But its extremely pricey at over $500 for the inital kit, and $135 for 20 2-part packets.

Now i know that the acrylic paints are basicly for looks, and dont act as a resist to solder, so is there any other products out there cheaper then what LPKF sells that are true solder resists?
Im surprized there isnt some type of laminate that can be heat rolled onto a pcb.

Any info would be greatly appreciated.
By Chip Douglas
#30215
Nobody?!

Is this like top secret information or what?

I was sure you guys at sparkfun would know something about soldermasks.

I like the idea of individual 2-part epoxy packets, but @ $135 for 20 of them is ridiculous.

This is driving me nutz, My prototype boards are practically perfect,other then a true soldermask,and the obvious 3+ layer there no different then getting them made professionally.I even included via's using PTH inserts.

Theres gotta be a better (cheaper)solution other then tranparent acrylic paints.
By emf
#30217
I've never heard of anyone doing solder mask or true plated through-holes at home, so this is just an idea:

You may have seen them, but http://www.thinktink.com has a lot of the stuff you'd need to do a lot of the advanced PCB processing. They have a dry-film soldermask that's $250 for a 1' x 40' roll. If I'm reading it right, the only other stuff you'd need would be a laminator, exposure frame, and developer, but you probably have some or all of that already. If you could find a few other hobbyists to split the roll with, it could be pretty reasonable. I doubt if I'll make 40 square feet of PC boards before I die...
By Chip Douglas
#30219
Its pretty easy to do your own plated through holes, using the inserts.I have an assorment of micro punches I attach to my drill press.There not "true Plated through holes"but they work.As for thinktink...I have came across there dry film, but wasnt sure if it was exactly what im looking for, and yes $250 for a roll is too pricey and more then i would ever need.If i can find a company that sells the film in smaller rolls for under $75 I might give it a try, or a company that gives out samples would be better.

I have the laminator, but where im confused is what/why it needs to be developed?Cant you just put the film over the pcb and run it through the laminator?
By emf
#30222
Chip Douglas wrote:Its pretty easy to do your own plated through holes, using the inserts.
I've always wondered, do they lay flat enough that you can put them under components?
I have the laminator, but where im confused is what/why it needs to be developed?Cant you just put the film over the pcb and run it through the laminator?
You laminate a solid sheet of solder mask onto the board which covers up all of the traces & pads. Then you have to remove the parts of the solder mask over the pads. It sounds like you expose an image of the areas you want to remove, then expose, develop, and then scrub the board to lift off the solder mask where it was exposed. You have to expose the liquid version too, this just looked like it would be cheaper for home use.
By futrtrubl
#30232
Where can I find those PTH inserts? Did a google search but all I came across were molecular biology sites ;']

Edward
By Chip Douglas
#30264
As long as your drill holes are perfectly straight then they will lay flat.
As far as placing them under components, ive never had to, but i guess it would depend on how low to the surface your component lays and the thickness of the insert.

Also take into consideration the thickness of solder you apply to ensure a solid connection.

Using a desoldering braid after applying solder should cut down the thickness.

I dont remember what company i bought them from, and i dont feel like looking through all my catalogs, but if you want to search for them they go by alot of different names.

PTH Inserts
PTH Eyelet
Bail Bars
PTH Rivets...ect..ect..lol

I did a quick search and found a few links for you guys.

http://www.megauk.com/through_hole_rivets.php

http://www.intl-eyelets.com/
By Philba
#30297
I've never used eyelets. it seems to me that it's a lot easier (and cheaper) to just stick a wire in the vias and solder both sides. Also, if you take a little care in your layout and routing, you can use TH leads to pass signals from one side to the other (by soldering both sides). Of course, that only works for componentes that expose leads on both sides. I can usually get by with only needling a small number of vias with that approach. I call it non-PTH design rules.
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