PCB repair

Thread Starter

upand_at_them

Joined May 15, 2010
760
I got this TI-83 calculator for free (didn't work). But I found the issue. The battery contact pad on the right looks fine, aside from a little material missing. But the pad on the left looks awful...corroded as well as missing material. How best to repair this? I have some copper clad board. If I can remove a piece of the copper foil, could I reasonably expect to get the glue side clean and can I reasonably expect to solder it to the bad pad? I also have brass shim stock (0.001").

IMAG1239.jpg
 

Yaakov

Joined Jan 27, 2019
2,342
I got this TI-83 calculator for free (didn't work). But I found the issue. The battery contact pad on the right looks fine, aside from a little material missing. But the pad on the left looks awful...corroded as well as missing material. How best to repair this? I have some copper clad board. If I can remove a piece of the copper foil, could I reasonably expect to get the glue side clean and can I reasonably expect to solder it to the bad pad? I also have brass shim stock (0.001").

View attachment 234711
The first thing I would do is try to clean the contact. with some very fine abrasive. If you have a fiberglass pen, that would be a good possibility but remember it creates glass dust.

If that doesn't wire, you should be able to fabricate a new contact from the copper foil but it will quickly tarnish and need cleaning. You can coat it with solder to avoid that. You should be able to bridge to the trace, a component lead would be a good jumper and promote a bridge.
 

Thread Starter

upand_at_them

Joined May 15, 2010
760
I should point out that the picture is after scrubbing with IPA and Q-tips.

Will acetone prepare the back side of the copper foil without destroying the copper?
 

Yaakov

Joined Jan 27, 2019
2,342
I should point out that the picture is after scrubbing with IPA and Q-tips.

Will acetone prepare the back side of the copper foil without destroying the copper?
Solvents aren't going to do it, you need abrasives. I'd really try cleaning first, with either very fine abrasive paper 600+ grit) or a fiberglass pen.
 

Thread Starter

upand_at_them

Joined May 15, 2010
760
Yes on flux. For now I've soldered a wire onto the trace to make sure the calculator powers up...It does. But I don't think I can solder the wire onto the stainless steel battery connector. I suppose I could solder a length of desoldering braid across the pad and to the trace.
 

Janis59

Joined Aug 21, 2017
1,297
The best repair is to drill at least 3 points with 0.6 mm hole and insert there copper vias pistons. At them solder three stubs soldered to new stainless platelet electrode. Mechanically stable, strong etc. PS, sometimes may buy even 1.2 mm vias, them are stronger.
 
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