Electronics > Repair
Keyboard flexi PCB
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soldar:
This could be titled "Fools rush in where angels fear to tread". ( https://en.wikipedia.org/wiki/An_Essay_on_Criticism )

I have a favorite keyboard which got wet and some keys stopped working. I discovered some discontinuity in a few traces of the flex pcb.

On eBay I ordered some conductive ink and I received it recently except that it looked like thermal paste and not like conductive ink. No matter I thought, I will just try it.

Well, not only it does not conduct but it dissolved the trace so now the problem is made worse.

And now I think "why did I not test it first in some other place or even just test it for conductivity?"

So here I am, having damaged the keyboard even further and feeling silly for having done it.

Now i will have to search for some real conductive ink. I seem to remember I already asked about this in the past.
squadchannel:
I have repaired a trace on a IBM Model M keyboard with aluminum foil.
It is not unusable, but sometimes I cannot type. It is cured by tapping it, though.
The pressure with which the aluminum foil and conductive trace are pressed together is important.

Where I live, it is relatively easy to purchase conductive paint. It is sold for the purpose of applying conductive shielding inside plastic cases.
I have used this paint to repair bonding wires on ICs.
I am sure there are similar products available.
soldar:
I bought this as conductive paint but it is more like paste and it does not conduct when applied. Still, I am doing some experiments because I think there is a chance it might conduct (enough) after it dries but it takes many hours, days even, to dry. We shall see. Maybe it will work well enough even if I have to apply several layers. I will see.
tooki:
Honest question: why are so many people reluctant to buy stuff from reputable distributors (like DigiKey, mouser, Farnell, RS, Reichelt, Conrad, and many others), instead choosing who-knows-what from eBay? It just doesn’t make sense to me.
soldar:
Well, I did some experimenting and it does seem to work for now. As the paint/paste dries it does conduct enough that the keyboard works. It is tricky to apply because the traces are so thin but I did manage to do it. After it dries it shrinks down to very flat on the PCB.

I suppose I should not expect it to stop working or have problems but only time will tell. For now it is working.
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