Sometimes it makes sense to install heat sinks on some components , in particular on the processor. Such hardware modification provides improved stability eg. for the Fritz!Box 7170.
Procedure
1. Open your Fritz!Box and check what components heat up during service. Very often it is only the processor.
2. Get an appropriate heat sink. It should fit exactly the component and must not touch others. You can buy heat sinks, alternatively you can find them on used motherboards, graphics cards etc. It might be necessary to cut the heat sink to the right dimension
3. Buy heat conducting pad or glue.
4. Finally attach the heat sink to the component. Fritz!Box switched off, of course. A hint: heat conducting paste or glue works best if it is not applied too thick or too thin.
5. optional, RECOMMENDED
You can cut a matching opening in the casing.
6. optional
Optionally you can install a temperature sensor with display between component and heat sink. Such sensors are available together with many computer casings or separately.
7. optional