Covering PCB Pads

Question

I have a PCB that was poorly designed and there is a ground pad that is too close to a signal pad. As a result, the signal pad on the surface mount component will short to ground. I was looking to use some ink or other material to cover the ground pad. The pads are too small to fit Kapton tape. Are there any standard materials used to cover PCB SMT pads?

Solution: I ended up cutting the pad out of the board using a very small razor blade. Picture from under a microscope of the end product:

Answer 1

Is it possible to cut the pad with a razor just to make some space? Are you getting bridging during the reflow process? If you post a picture of the offending area I think we could comment more on a suitable repair solution.

Answer 2

I think you can get a soldermask-like material in a small touch-up bottle. You might want to check out the website of Circuit Technology Center, who specialize in this sort of work, and also sell materials and tools if you want to DIY.

See their epoxy/mask kit, and the application guides at the bottom of that page.

(No relation to me, other than as a very satisfied customer.)

Answer 3

With care, a pointy tungsten-carbide bit like this chucked in your Dremel can be used to open up clearances between pads.

Answer 4

If this PCB is for personal use then I will suggest using a nail polish, i have used it before and it can be easily removed with a polish remover like acetone. Or use an oil-based paint marker if you want to look more professional.

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Update: I will not suggest this method if you are planing to solder around the area after applying the paint. I use it to cover traces before etching my boards, or after I am done to protect some areas.

Answer 5

I'd probably try the following things in this order:

1. Make the gap bigger by cutting the copper away. I use a special too for this called a "screwdriver". A small flat bladed one works. This isn't the optimum way and is only for one-off, but I list it first because the screwdriver is already on my bench and I'd be done in a minute.

2. Grind off the extra copper like Dave suggested. I have done that a bunch too. It works well and you can get good control with a fine-pointed grinding tip. This is #2 for me because the high speed rotary tool (mine is not actually Dremmel brand) is accross the room on a shelf, so I'd have to go get it, put on the right tip, futz with the power cord, etc.

3. Kapton tape. I think that's actually a brand name, but it's what this kind of high temperature adhesive tape is commonly called. This looks like transparent orange-color mylar, and is intended to survive soldering temperature.