Removal characteristics of particulate matter with different return air system designs in a nonunidirectional cleanroom for integrated circuit (Ic) testing processes

In a conventional arrangement of the airflow pathway in nonunidirectional airflow cleanrooms with wall return schemes, the supply air is introduced from ceiling air grills and the return air, close and vertical to the floor, is extracted from the wall air grills. However, such a wall return ventilation system is theoretically not an optimal design for removing heat and particles released from processing machinery. The conventional wall return system currently used in cleanrooms aims to create an environment with diluted particle concentration in which downward cold supply air from ceiling filters encounters upward air currents generated by drifted particles from processing machinery. To solve the problem, we introduced a new design called fan dry coil units (FDCUs). In this article, we compare the performances of both innovative and traditional ventilation systems in a full-scale cleanroom. For each return air ventilation system, we investigated the effects of air change rates on the removal of 0.1∼5 μm particles. Based on the results, it is noted that the FDCU-return system eliminates about 60% more particles from the cleanrooms, compared with conventional wall-return system.