The other day I put a new battery in an old digital tire gauge, hoping to revive it Nope. So just for the heck of it I took it apart and found that it didn’t matter whether the batter was dead or that gauge circuitry was still working, because there was no connection between the display and the rest of the thing.
Instead of wires or flex or something sensible, the designer used a piece of rubber with a zillion embedded parallel conductors. The idea, I guess, is to carry signals from a bunch of goldplated bumps on the main circuit board to a bunch of contacts on the display. As long as those two are properly aligned, it doesn’t matter whether the rubber bit is in exactly the right place, because it conducts across the piece but not lengthwise.
Until the rubber shrinks a little. Or the ends of the embedded conductors develop an oxide coating. Or moisture condenses anywhere near it. I’ve lost count of how many cheapjack little devices I’ve taken apart that might have been working fine, except that they couldn’t display anything because of one of those stupid little rubber bits. And each time (hope springs eternal) I’m pissed off again. I should really have learned by now.
For the manufacturers I guess it makes sense. Not only do they lower parts and manufacturing costs (no fancy soldering, no super-precise alignment fixtures), but they guarantee a steady stream of replacement purchases. And sure, I’ll never buy something with that particular brand name on it again, but the factory doesn’t care.