(Topic ID: 118574)

Best way to replace metal pads on circuit board?


By HisboyElroy

5 years ago



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  • 13 posts
  • 8 Pinsiders participating
  • Latest reply 5 years ago by Mk1Mod0
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    TracesWorn-205.JPG

    #1 5 years ago

    The pic below is from the lower track on an EM gun game. You can see that the metal contact pads have literally been cut in half from the leaf switch dragging across over the years. The leaf switches no longer make contact. Is there a good way to replace them? Each pad is about an inch square... Any replacement material must be thin enough that the leaf switch can drag across without catching. Any ideas?

    TracesWorn-205.JPG

    #2 5 years ago

    Maybe you can just move the switch up onto a fresher part of the contacts?

    #3 5 years ago

    Have you ever etched a circuit board?

    Scan it, print it on a laser printer using photo stock paper, iron on to a circuit board, etch.

    #4 5 years ago
    Quoted from ecurtz:

    Maybe you can just move the switch up onto a fresher part of the contacts?

    I thought about that... I'll do it as a last resort but was wondering if there is a product or strategy to overlay the existing pads.

    I've never etched a board. The entire track is about 2ft x 2 inches. Where's a good place to get such a board?

    #5 5 years ago

    You could try a conductive ink pen and see how that does. Unfortunately, they tend to be higher resistance than copper and I don't know if it's going to hold up.

    You could also try copper tape - amazon.com link »
    I'm unclear whether the adhesive is conductive or not, so you may also need solder to bridge to the rest of the pad.

    If you go the etch route (you could probably just draw the layout by hand with sharpies if you wanted to) then I see 2 ft long sections of PCB here: amazon.com link »

    Ultimately the PCB solution will be the best long term fix, but the tape might be a quick solution.

    #6 5 years ago

    I vote for shifting the mount position of the board down - 1/8" should do it.

    #7 5 years ago
    Quoted from MikeO:

    I vote for shifting the mount position of the board down - 1/8" should do it.

    Tried that, there are 5 copper fingers that make contact on that track. with the board adjusted all the way down they still don't all make contact.

    I think I'll try a combination of copper tape & bending the fingers so they ride higher-up.

    #8 5 years ago

    I looked closer to your picture and offer the following suggestions.

    1. Your picture looks like the board is shifted up as high as possible. I believe you could lengthen the slotted holes to allow the board to raise a bit more. This would keep the followers for the lower spider fingers on the trace material. It would also allow you to solder a small jumper wire between the separated sections of trace yet not interfere with the new positions of contact between the fingers and trace. If you can reestablish continuity between both sides of the trace material, as long as the fingers don't need to reside in the same location, you will be OK.

    2. Adjust the slotted holes so that the fingers reside on remaining trace material in the upper section of the trace material. This is touchy because there is a limit to how far you can lower the complete board before the fingers will not contact the lower trace areas.

    One of these should do the job for you with minimal effort.

    #9 5 years ago

    If you don't want to etch a new PCB... here's what I would try.

    I like the suggestion above mine but I wanted to elaborate on it a bit...

    Scuff up the existing traces you want to bridge with wet/dry 800 grit sand paper, especially on the two edges you want to bond. Then, bridge the gaps with some high quality silver-bearing type solder that also contains flux. Then, use some coarser grit sandpaper to sand the solder flat so it matches flush with the other two copper sides. I would carefully use my dremel sanding attachment for that step but regular hand sanding would also work (and is SAFER!). The repair should last as long as you ever own the game. You may want to determine if that blade that cut the trace has a burr on it or a sharp edge. It should not have cut through like that under normal play.

    Have you tried to contact Steve Y. at PBR? Sometimes he does have odd-ball parts like this in stock.

    #10 5 years ago

    Be careful if you bridge the gap with solder and then try to sand or dremel it. The trace material is relatively soft and any solder you apply will be relatively hard. When sanding, while your intentions may be good, it would be very easy to sand away the trace with any errant alignment of sandpaper before you get the solder sanded down.

    I'd think long and hard before I proceeded with this approach.

    #11 5 years ago

    I think I would try to modify those two contact fingers. This older style is fairly robust. If you are skilled and careful, you might be able to drill two new holes for the mounting screws and move the whole thing up the spacing of the mounting screws. (1/4-5/16"?)

    #12 5 years ago
    Quoted from MikeO:

    Be careful if you bridge the gap with solder and then try to sand or dremel it. The trace material is relatively soft and any solder you apply will be relatively hard. When sanding, while your intentions may be good, it would be very easy to sand away the trace with any errant alignment of sandpaper before you get the solder sanded down.
    I'd think long and hard before I proceeded with this approach.

    Wet/dry fine grit will not sand off a copper trace unless you hand sand it for hours... I've used it for over 10 years. Solder always sands away a LOT quicker than copper from my experience. You only have to scuff it so the solder will stick, not go over and over it a ton. I would not suggest using a dremel for this unless you have a LOT of experience using one. You should get good results and not damage anything using hand sanding. Bridging the gap on the back side with kynar wire may work, but could get messy...

    If you are simply going to try and move the fingers any way, you would't even have to sand after you bridge the gaps with solder.

    One other thing I thought about is you could possibly use copper foil to repair the copper traces if they are really thin. The added thickness would probably be ok. You could test one of the pads by temporarily taping or glueing (or soldering?) down a square of copper foil to see if the added thickness will be ok.

    I just noticed that this reiterates mhkohne's suggestion above.

    #13 5 years ago

    I would go with the copper tape. You can lay a strip just wide enough to bridge the gap then dab a small bit of solder above and below to ensure conductivity. (It comes in all widths so you don't have to cut it down.) It is foil thin and holds quite well. The fingers should have no trouble passing over the ends. Minimal cost and minimal effort for maximum effect.

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