Cleanroom technology applications in several hot issues currently

I. Introduction
Cleanroom air velocity / ACH, has been a concern in cleanroom design issues, with the clean room to increase pollution control results and final stage filter efficiency, etc., on the relevant norms, guidelines and other recommendations made or reference values ​​are conservative, there are many discussions; FFU in the application of the feared noise, damage repair and other issues have been resolved in practice, with the continuous improvement of FFU, FFU on whether to adopt the return air system is also a Hot: Suspended molecular contamination (AMC) control in the microelectronics and IC industry has been growing on the agenda, attention. The following cases were on these issues as summarized and analyzed.

Two. Airflow velocity
2.1 For recommended applications or reference values
Clean indoor air speed under certain cleanliness to determine, with the clean room use and other specific circumstances vary, it is not only affected by the amount of dust and indoor filter efficiency is also affected by other factors, in terms of industrial clean rooms, cleanliness and choices affect flow rate of the main factors are:
(1) indoor sources: building components, the number of personnel and operational activities, process equipment, process materials and processing technology itself, are all dust sources of release, according to the specific circumstances vary, vary greatly;
(2) indoor air flow pattern and distribution: unidirectional flow requires uniform and equal flow lines, but will be subject to changes in process equipment and personnel arrangement and location of activities such as the formation of local vortex interference; rather than unidirectional flow requires sufficient mixing, Avoid dead ends and temperature stratification;
(3) purification time (recovery time) control requirements: clean room or accidental releases of pollutants into the air or gas flow during normal operation is interrupted or intermittent convection currents or other movement of persons and equipment will result in the deterioration of cleanliness , return to the original time to determine the cleanliness of the gas flow velocity purification; the purification time control requirements depend on this time frame (lower cleanliness deterioration), the product of the quality and yield of the production capacity of impact;
(4) the final stage of the filter efficiency: COG LCD Module in a certain amount of dust indoors under high efficiency filters can be used to reduce the flow rate; energy should be considered as a high efficiency filters and reduce the flow rate, or a lower efficiency filter and the higher flow rate, in order to the product flow and least resistance;
(5) economic considerations: excessive air velocity resulting in an increase in investment and operating costs, the appropriate air velocity above factors reasonably comprehensive, too often unnecessary, does not necessarily have an effect;
(6) low demand for cleanliness cleanroom, sometimes ventilation frequency depends on the indoor heat requirements.
These factors are difficult to quantify, can only be analyzed and compared and estimates. Therefore, in engineering applications, for cleanroom air velocity tends to refer to the relevant norms, OLED Display Module guidelines and other recommendations or reference value, and then the specific circumstances of the estimated impact of the above factors were determined after comprehensive consideration.
Air velocity for unidirectional flow clean room; non-unidirectional flow clean room ventilation frequency is preferred because it is difficult to measure accurately airflow velocity; also littered with late-stage filtration rate to reflect, and can be used for various types of air flow clean room, generally covered with 100% relative to the flow rate of 0.5m / s (100fpm), 25% relative to 0.125m / s (25fpm). Current relevant norms, guidelines and other recommendations or reference values ​​are shown in Table 1.
Note: 1, ISO14644-4 for the air velocity / ACH is clear as reference materials listed in the table only for microelectronics and IC factories; right column ISO5 only pharmaceutical grade air velocity> 0.2m / s, right ISO6 ~ 8 级 Jiewei lists reference values.
2, (M) refers to the mixed flow, N refers to the non-unidirectional flow; * refers to the isolation of pollution has taken effective measures to clean areas.