Anyone who has taken apart a few failing TV remotes, cordless phones or other devices with bad buttons has probably run into a curious oily liquid inside the buttons causing the problem. You can clean it up using isopropyl alcohol but the problem returns.
Like most people (including myself) when you first run into this you probably think the liquid is from a drink spill… or humidity… or maybe oil from your hand… What is it!?!?
Come to find out…
It’s NOT from a spill, finger oil, humidity… or even spit 😉
The liquid found in rubber keypads is left over silicone oil from the manufacturing process when they rubber keypad has not been baked enough…. it’s a gooey center, undercooked rubber keypad!
Cooking those rubber pads takes a lot of time and energy….. and when you can save some time and energy (money) you can lower the cost of your product. Since it can take years for the oils to ooze out of the rubber pad it will never be caught by the development team….. and if lucky, never even cause a problem for the consumer.
I once took several different new rubber keypads and crushed them overnight in a 3000lb press between two metal plates and a few paper towels…. just to see for myself. The next day there was a ring of oil around each keypad in the paper, one much more than the other. I can assure you that stain was not a drink spill, humidity or oil from my hands as I put handled the keypads.
Some rubber keypads have large rubber button contacts and those always have the most trouble with oils. A better keypad design uses a thin rubber keypad and a larger plastic button over the keypad. Of course if one button is used more you are going to see more problems…. like the channel and volume buttons on the TV remote… or the Answer button on a cordless phone.
The KX-TGA400b phone had… no has, terrible button problems. The keypad is entirely rubber (no plastic key caps)…. and the keypad was produced as cheaply as possible (less baking). This model is famous for the #1 key not working. Being curious as to why the #1 button on a phone would be the first to act up, eventually after looking into it for a while I discovered that the way many people hold the cordless phone was the issue. Their thumb would need to apply more pressure to the top left key just by the way it was held in the hand. A little extra pressure over hundreds of button presses was all it took.