Panic and bullshit
A few months ago, I got my hands on a box full of these and these because the batteries leaked and rendered the buttons useless. Before they were thrown away, I grabbed the whole box (about 50 in total), took them home and quickly started designing a new PCB based on the ESP8266. The plan is, as always, to extend my smarthome system.
The first two iterations were completely miscalculated. The PCBs itself were bigger than the initial ones, resulting in the PCBs either not fitting or the button being blocked so it can’t be pressed down. The third iteration though fits almost perfectly in the case (only a small useless stub of plastic needs to be broken out).
I assembled the first of the three ordered boards, and it worked perfectly. The LED that is built into the button can be controlled by my board, and the membran switch inside can be read out by the ESP as well. Pretty cool, having a panic button for my system.
The second board wasn’t as easy to work with as the first one. I confirmed my suspicions: After assembling, there was – again – a short to ground. This time though, I desoldered the ESP to see how it looks beneath. Et voilà, solder paste spread out resulting in a ton of pins being connected and causing the problem. I removed the solder paste and soldered a clean ESP onto the board. This time, without solder paste. And it worked as expected.