I'm currently building my own Home Automation System with a bunch of Arduinos and Relais, all of them wired to Ethernet "Shields". The casing I am printing on a 3D printer.
The Arduinos work great with those Ethernet "Shields", but the ENC28J60 chip on those Ethernet boards get quite hot. I am measuring 79.5°C approx. In the plastic casing, I expect that they reach higher temperatures (because it's closed and has no ventilation whatsoever).
Since I am building this as a permanent solution (House wiring is now all newly adapted and I have no way back), which lifespan can I expect from those Ethernet boards?
The datasheet of that chip is saying that it's rated up to 85°C, but what does this upper rating mean? Will it stop working at this point, or only begin to degrade it's lifetime at this point?
EDIT: I have no space to put a dissipation block on those chips, because the casing is so tight.