Repair PCB Teeth

For lack of better terms...lol. How do you go about repairing the teeth on a pcb when one flaked off?



Are you talking about the card edge like this?

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I believe the right way to do it is to adhere a piece of copper tape to where the contact once was and connect said tape to its circuit with a bit of solder and/or wire. I've done it once and it came out ok. Pretty much like the picture shows. I think that would be the cleanest method anyway, but someone else here might have a better idea.
 
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It's easy when the trace is a power one and connects to both the top and bottom sides of the board. That Pac edge connector in the picture will have the copper tape wrapped around the edge of the board to the other side where it's soldered in a similar fashion.

If it doesn't connect to the same thing top and bottom side then that gets much harder. You'll need some way to stick the copper down that is resistant to the heat of soldering. DO NOT use "super glue" or cheap epoxy.
 
I usually scrape out a small rectangular indentation and use a bit of tin plate cut to size. Using high temp epoxy glue to stick it on and then tin both contacts so it covers the tiny gap. Then with a piece of fine sandpaper, file it down so it's flushed to the pcb. Looks great.

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I assume you're working on a Pole Position (in which case it's a 5V or GND pin, which is the same on both sides of the board.)

As other have mentioned, adhesive copper tape is the way to go. And wrap it around, removing and replacing the finger on the other side of the board (even if it isn't damaged).

What's important with this type of repair is getting the thickness right. That's why you want to remove the finger from the other side even if it's still good, and not just tape over it. I score the finger all the way at the bottom of the finger, using an exacto, then lift at the PCB edge and peel it off. You want the thickness to be as flat as it was originally, as if it's too thick, it will stretch out and/or damage the pins in your edge connector.

You also want to dig out any charred PCB fiberglass, under the finger, if it's brittle or loose. However what happens here is you'll be left with a depression. And because that will affect the thickness, it will cause connection issues.

Some folks fill the hole with epoxy, then put the tape over it. That works, but is slow and can be a pain, as epoxy can get messy.

What I do is put the copper tape over the hole, then tin over the tape. I tin it all the way to the ends of the tape (where it meets the board), to make it electrically and visually seamless (and the color matches, so it makes the repair stick out less). However the other benefit is that you can fill the missing material from the hole with solder, rather than epoxy.

You just need to play with the solder a bit to get the thickness just right. But using quality solder like Kester 44 (which has a lot of good flux) helps.

I then clean the joint with acetone or Goof Off to remove the flux. Then I finish by burnishing it with a fine fiberglass pen, which matches the sheen of the other fingers.

When it's done, you almost can't tell it's been repaired, unless you see that the finger now wraps around the edge of the board.
 
I assume you're working on a Pole Position (in which case it's a 5V or GND pin, which is the same on both sides of the board.)

As other have mentioned, adhesive copper tape is the way to go. And wrap it around, removing and replacing the finger on the other side of the board (even if it isn't damaged).

What's important with this type of repair is getting the thickness right. That's why you want to remove the finger from the other side even if it's still good, and not just tape over it. I score the finger all the way at the bottom of the finger, using an exacto, then lift at the PCB edge and peel it off. You want the thickness to be as flat as it was originally, as if it's too thick, it will stretch out and/or damage the pins in your edge connector.

You also want to dig out any charred PCB fiberglass, under the finger, if it's brittle or loose. However what happens here is you'll be left with a depression. And because that will affect the thickness, it will cause connection issues.

Some folks fill the hole with epoxy, then put the tape over it. That works, but is slow and can be a pain, as epoxy can get messy.

What I do is put the copper tape over the hole, then tin over the tape. I tin it all the way to the ends of the tape (where it meets the board), to make it electrically and visually seamless (and the color matches, so it makes the repair stick out less). However the other benefit is that you can fill the missing material from the hole with solder, rather than epoxy.

You just need to play with the solder a bit to get the thickness just right. But using quality solder like Kester 44 (which has a lot of good flux) helps.

I then clean the joint with acetone or Goof Off to remove the flux. Then I finish by burnishing it with a fine fiberglass pen, which matches the sheen of the other fingers.

When it's done, you almost can't tell it's been repaired, unless you see that the finger now wraps around the edge of the board.

Any specific recommended copper tape and whatever tin?
 
What I do is put the copper tape over the hole, then tin over the tape. I tin it all the way to the ends of the tape (where it meets the board), to make it electrically and visually seamless (and the color matches, so it makes the repair stick out less). However the other benefit is that you can fill the missing material from the hole with solder, rather than epoxy.

You just need to play with the solder a bit to get the thickness just right. But using quality solder like Kester 44 (which has a lot of good flux) helps.

I then clean the joint with acetone or Goof Off to remove the flux. Then I finish by burnishing it with a fine fiberglass pen, which matches the sheen of the other fingers.

When it's done, you almost can't tell it's been repaired, unless you see that the finger now wraps around the edge of the board.
Sorry, sure I'm driving you nuts. But you're saying to use copper tapen then tin. In that 4 part video posted he uses a copper tape that is plated with tin. Would that be a better easier way to go to save a step or not?

Any recommendations on mil thickness? Thanks
 
Sorry, sure I'm driving you nuts. But you're saying to use copper tapen then tin. In that 4 part video posted he uses a copper tape that is plated with tin. Would that be a better easier way to go to save a step or not?

Any recommendations on mil thickness? Thanks


The videos above fill the burned-out depression in the PCB with epoxy first, then apply the copper tape over it. That can work fine, but it's slow, as you need to wait for the epoxy to really cure, which takes a few days if you really want it cured.

My method puts the copper tape down first (after cleaning out the char/damage), and then fills the depression with solder (i.e., tin), rather than epoxy. It's faster, but works just as well. You don't need pre-tinned copper tape, as you'll want to solder the copper tape to the trace on the PCB anyway. (And you want single-sided adhesive, not the double-sided.)
And you run the solder over the rest of the tape, to level it out (filling any unevenness), and to match the color. You can then burnish it with a fiberglass pen ($6 on ebay), and it will match the other fingers near perfectly (as you should burnish the other ones too anyway).

Note one other thing to be aware of is whether the finger you're repairing is a power pin or not. Most power fingers are the same voltage on both sides of the PCB, for the given location (and power/ground fingers are usually the ones that burn up). When the finger is the same on both sides, you want to actually replace both fingers (even if the other side is ok, cut it off anyway with an Xacto, at the base of the finger), as you can wrap the tape around the edge, and solder the tape to the traces on *both* sides of the PCB, which will keep it much more secure, versus relying on the adhesive or epoxy to keep the tape down.

When you don't do it this way (as in the vid above), you run a greater risk of the finger lifting again, if the epoxy or adhesive gives out, etc. But when it's wrapped around the edge, it's much less likely to come off. However note that you can only do this for power or ground fingers, where they are the same voltage on *both* sides of the PCB, as most of the time for the other signal fingers, they are not the same on both sides.

Also try to get actual 3M brand tape if possible, as the adhesive is better than on the Chinese tape. (The Chinese stuff isn't horrible, but the 3M is better.) Also, thickness probably doesn't matter that much. I threw my calipers on the stuff I have, and it was measuring 1 mil (.001").
 
Ok cool. Yeah, as of right now I probably have 6 Pole Position boards (at least with this issue) all with that same usual spot to practice on. So same on both sides.

Thanks for all the info. Hoping to be able to master this. I want it looking as un-noticable as possible. That whole mixing paint/glue in the videos was a huge turn-off for me so this sounds good.
 
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