PREVENTIVE MAINTENANCE

Power semiconductor devices useful life rely on a carefully scheduled preventive monthly maintenance. This maintenance must check the following:

• Temperature measurement of ambient air, devices, heatsinks and water when appropriate;
• Device cleaning;
• Correct mounting of devices with a torque meter wrench;
• The main causes for temperature rise of semiconductor devices are:
  • Blocked water pipes and hoses of the cooling system
  • Dirty heatsinks, caused by dust and/or oil vapor;
  • Failure of the cooling fans;
  • Dirty air filters;
  • Excessive ambient air temperature.

For power semiconductor devices, it's recommended to install a thermocouple in the heatsink, close to the semiconductor device's baseplate.
The devices must be cleaned with clean water. The use of organic solvents should be avoided, thus preventing the presence of its residues on semiconductor devices. It's recommended to clean the semiconductor devices with distilled water. If necessary, one could use a neutral soap to clean and then carefully rinse the devices. All devices must be completely dry before turning the system's power back on. To dry, use a clean absorbent cloth or paper, followed by hot air venting.
If a semiconductor device happens to be loose, it should be removed from the heatsink. The heatsink must be cleaned and the thermal compound should be reapplied. Then, the device could be mounted again. If the heatsink's surface is rough, it must be machine flattened again.
For parallel devices connection, the device characteristics must be correctly balanced. If one of the devices have to be replaced, all the devices connected in parallel must be changed to avoid further balance issues. The useful devices that have been removed should be factory balanced again for future use.