Just wanted to share my experience since I only found limited info online about this. I picked up an eMac with the original keyboard (A1048) and it was pretty dirty. I had a complete lapse in judgement and used water to clean the top part with the membrane 
. A decent number of keys didn't work the next day when I reassembled it.
I didn't want to spend a ton of money on a repair and copper tape that was conductive on both sides sounded like a great option. Unfortunately, it didn't work at all - the adhesive side of the tape I bought proved not to be conductive at all according to my multimeter. It would've also been a bit awkward to work with - the broken traces were much thinner than the width of the tape.
This excellent iFixit guide suggests a conductive pen, but the really nice ones seemed a bit expensive. I decided to try a Circuit Scribe pen, which was only about $10 (USD) and, so far, it's worked great. The pen had just the right width to make it easy to use on the traces and I was able to get every key working again. I was concerned that any conductive ink might be too vertically tall and cause the key to always be detected as pressed, but that didn't end up being an issue at all, at least for this keyboard. The repair was tedious, but steady. I saw something about the Circuit Scribe ink drying out and cracking over time, so I'll try and post back here in the future to report on whether that became an issue. So far though, I'm very happy with how it worked for this application. Here's a photo of a portion of the repair:
. A decent number of keys didn't work the next day when I reassembled it.I didn't want to spend a ton of money on a repair and copper tape that was conductive on both sides sounded like a great option. Unfortunately, it didn't work at all - the adhesive side of the tape I bought proved not to be conductive at all according to my multimeter. It would've also been a bit awkward to work with - the broken traces were much thinner than the width of the tape.
This excellent iFixit guide suggests a conductive pen, but the really nice ones seemed a bit expensive. I decided to try a Circuit Scribe pen, which was only about $10 (USD) and, so far, it's worked great. The pen had just the right width to make it easy to use on the traces and I was able to get every key working again. I was concerned that any conductive ink might be too vertically tall and cause the key to always be detected as pressed, but that didn't end up being an issue at all, at least for this keyboard. The repair was tedious, but steady. I saw something about the Circuit Scribe ink drying out and cracking over time, so I'll try and post back here in the future to report on whether that became an issue. So far though, I'm very happy with how it worked for this application. Here's a photo of a portion of the repair:
