Fan filter unit (FFU) is the necessary air purification equipment for semiconductor cleanrooms with stringent cleanliness requirements. Routine maintenance could greatly extend the life of FFU and reduce the maintenance cost of the company. The fan filter unit maintenance period occurs quarterly or annually.

Here are the things you need to check during fan filter unit maintenance:

1. Check whether the screws around the FFU are tight or not and whether the impeller is deformed?

2. Check whether the control box functions well and connects to the case or not?

3. Check whether the interface of HEPA filter is clean or not? Test the air velocity and filtration efficiency

  • Air velocity test: Set 9 points on HEPA filter interface. Use an anemometer at the distance of 1.2 - 1.5 m below fan filter unit to calculate the air velocity difference.
  • Filtration efficiency test: The efficiency tester should be close to the surface of the HEPA filter, stay at each point for 1 min, and count the filter value. After finishing the close test, it is necessary to collect the filter value at the same point 1m below the air outlet surface of HEPA filter, compare the close test data, and calculate the data difference.

FFU - Fan Filter Unit VCR1175

Fan filter unit with hepa filter

Fan filter unit maintenance method for semiconductor cleanroom

1. After the FFU has been in use for 3 months, the fan filter unit impeller should be checked regularly. If the screw is loose, it should be tightened
2. In case, the governor is not operating normally, it should be repaired as soon as possible. For instance, when the speed is increased, the air volume of the fan filter unit does not change significantly, then the power or SCR needs to be replaced.
3. If the test found that the HEPA filter is damaged (reduced wind speed, or low filtration efficiency), HEPA filter should be replaced