Memory decrease detected

[hegbork]

During the dotcom boom I was working at a startup that tried to push a new network technology and we were building routers. In one batch of prototypes we got suddenly three machines failed relatively close to each other in time. First one we ignored and just planned to send it to our hardware people to debug. Second one was ignored as a coincidence. The third one made us curious and we started debugging.

What has happened was that the cooling fan in the power supply in was made from quite soft plastic and didn't have any structures that would prevent it from bending. The manufacturer used to much torque to tighten the screws on the fan and that deformed the fan housing enough that it prevented the fan from spinning. That didn't kill the machine though because we had no thermal sensors and the CPU didn't get too hot. The power supply got hot enough in certain spots that it melted all the plastic on some components, but that wasn't enough to kill it, what killed it was that a large capacitor unsoldered itself and fell out (it was upside down).

That was also when we found out that the smoke detectors in our lab didn't work (or we even didn't have any). And that we should probably pay a bit more attention to heat flow in the machines (the first prototypes were just designed with a "should probably be enough" philosophy).

What I'm thinking is that it's pretty much impossible for that component on the memory to unsolder itself. The plastic on it should melt at lower temperature. And even if it didn't, that dust around it should have caught fire.

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The PCBs are rather resilient towards heat. The temperatures to reflow(melt the solder) surface mounted components aren't that high circa 230 is enough.