Note: I titled this referencing a keyboard, even though I am working on a touchpad. This is because most touchpads don’t use this type of build anymore, so I wanted to make the title more relevant.
Here in February of 2025, I have a good old IBM ThinkPad R52 laptop! It’s in pretty nice shape, and I easily was able to get everything working.
Well, for the most part. I discovered that the touchpad’s left-click button doesn’t work! This older laptop uses the nicer style of button, which is more like a keyboard key than it is a clicky button, like most laptops use.
In theory, the simple fix would be to replace the touchpad button module. In practice, this isn’t realistic, as the part is difficult to come by. So, I chose to investigate how this could be dealt with. I felt that there would likely be a simple explanation for such a thing, and otherwise, I’ve sure got nothing to lose.
Getting to the issue
First came the inspection – sure enough, as soon as I took got to the touchpad, I saw corrosion residue there, showing that liquid got in here at some point and messed with the circuitry. Looking closer revealed that the liquid ate away at the membrane trace that carries the left-click signal, therefore the circuit could never complete. That explains a lot!
Getting to the membrane is rather tedious, and only gets worse once you have to work with the membrane itself. On my laptop, after the palmrest casing is removed, the metal touchpad bracket must then be removed, and then the plastic backing (with the key clips) must be torn off. This then exposes the membrane sheet that is in between.
Here is the membrane sheet connected to the touchpad. Can you spot the connection break? Look closely – it’s darker than the rest of the wiring.
To resolve this, we must gain access to the very wiring itself. At least in this use case, the membrane sheet folds over an insulation layer, which you could say is sandwiched in between. These layers are VERY thin and delicate – it relies on very small tolerances. Be careful! There is adhesive that must be split thru – you want to take great care NOT to tear the connection between, you’re only trying to separate it so that you can lay everything flat and unfolded.
After carefully splitting the adhesive, we’re now presented with the membrane sheet itself. Great! And I’m sure you can now very easily see the break in the connection. Make no mistake – that is the left click, but on the right side, because we’re now looking at it from behind.
Now, how can this be remedied? I did some research, and one site suggested to use copper foil tape, so I gave that a shot. I had some from another project from years ago.
Here is how that looks. Unfortunately, it was at this point I discovered that the sticky side of my tape doesn’t conduct well enough! I think it is conductive on both sides, based on my previous experiments, but for this task, it’s conductive enough. Ergo, it’s not conductive here. So unfortunately that got me nowhere.
Another suggestion I read mentioned using conductive silver paste. Hmm! Well I once had that a long time ago, but that bottle long since dried up and got tossed. So I ordered some from Amazon, and waited.
It came in, and here’s how it came out. Seems promising – my multimeter confidently beeps during a continuity test! That should do it! That didn’t happen before with the copper foil tape. Also visible in the above picture on the touchpad bracket is the telltale white, powdery residue of corrosion from a past liquid spill. Now, to let this stuff dry…
Though it is quoted to dry in 24hr, I didn’t get a chance until a few days later to check it out, Sure enough – it works!! Now the left click can be used!
Now, unfortunately, the plastic shim for holding the touchpad buttons themselves is brittle, and it wound up cracking enough that I couldn’t use it. So in the end, I did wind up buying another touchpad, since apparently someone listed one for just $12. That’s okay! I now know exactly how to approach this problem the next time I might encounter it. And I made this article in hopes to help others just the same!