Whether the residual air release after cleaning of the wafer box can be controlled by environmental filtration requires distinguishing between the source in the box and the air in the room. Environmental chemical filtration can only process the air flow that actually passes through the filtration section, and cannot automatically eliminate residues and all sustained releases inside the container. The problem in the box cannot be solved by the room filter.

Does outgassing occur inside or outside the box?

The residual outgassing after cleaning of the wafer cassette mainly occurs in two locations. Outgassing inside the box comes from trace amounts of chemicals remaining on the box body, lining, or wafer surface after cleaning. They gradually evaporate after the box is closed, and the concentration may accumulate inside the box. Outgassing outside the box occurs when the box is opened, wafers are picked up, or the box is left open, and residual volatiles enter the surrounding air. Environmental filtration processes the part of the air that passes through the filter section in the latter, and has little effect on the accumulation in the closed box. To determine whether environmental filtration can help, the first thing to ask is: where does outgassing mainly occur and in what state does the box stay the longest.

The scope of environmental filtering has boundaries

Room circulation or equipment-side chemical filtration can only process the air sent into the filter section by the fan. If the box is closed and stored, the air in the box does not circulate with the outside world, and no matter how large the filter section is, it cannot handle the volatile matter in the box; if the air in the box is released to the microenvironment of the equipment during the box opening operation, and this part of the air happens to pass through the local filter section, filtration may be effective. Therefore, the effectiveness of environmental filtration on wafer cassette outgassing depends on whether the air path covers the location where outgassing occurs, rather than the ability of the filter material itself. Regarding the division of labor between local filtration and room filtration, please refer toCan a chemical filter be used alone in a room?。

The cleaning and drying links are more worth checking first.

The source of residual outgassing from the wafer box is in the cleaning and drying process, and the control position should also be prioritized here. The choice of cleaning agent, the number of rinses, the drying method and the standing time after drying will all affect the amount of residue. If the residue after cleaning is too high, relying on back-end environmental filtration to 'cover the bottom' will often achieve half the result with twice the effort. A more reasonable sequence is: first confirm whether the cleaning process and drying conditions are stable, and then evaluate the local filtration requirements for storage and box opening. For ideas on how cleaning agent data can be used to identify contamination, please refer toCan cleaning agent safety data sheets be used for chemical filter selection?。

Local filtration should cover box opening and storage

If there is still considerable air release after cleaning, the arrangement of local filtration should focus on the unpacking operation and storage process, rather than generally treating the room air. Circulation in the storage cabinet, local air supply at the box opening station, and internal circulation in the EFEM are all configuration points closer to the location where outgassing occurs. The common characteristics of these locations are small space and limited air volume. The matching of filter element form and air volume needs to be checked according to the actual structure. Regarding the filtering configuration of the storage link, please refer toHow to choose chemical filters for wafer storage cabinets?。

Aili industrial supporting equipment

For problems such as wafer box outgassing, we usually confirm with the customer whether the outgassing mainly occurs in the closed state of the box or during the box opening operation, and then determine whether the local filter should be placed in the storage cabinet, the box opening station, or the EFEM circulation section. Aili Industry can provide selection packages for box-type, flat-plate and V-type chemical filtration products. For box-type MAU packages, please refer toMAU box type chemical filter , product series can be viewedChemical filter product range . Equipment-side applications can adopt the form of chemical filtration FFU, integrating chemical adsorption layer and HEPA/ULPA particle filtration. The chemical-first-particle structure is suitable for micro-environments such as storage cabinets and EFEM. The compact filter element can be customized according to the cabinet space and circulating air volume. The manufacturing end covers motors, fans, control systems, sheet metal and complete machine assembly. The interfaces between the filter section and the cabinet circulation fan can be aligned in the same package. The specific gas effect, applicable environment and replacement cycle still need to be verified based on the corresponding configuration data and on-site working conditions. The actual results are subject to on-site leak detection and gas detection results.

Related questions and answers

The room is equipped with a chemical filter. Does the gas released from the wafer box need to be treated separately?
Depends on whether the box is closed for storage. When the air in the box is not circulated with the room, the room filter cannot handle the accumulation in the box, and circulation in the storage cabinet or local filtration at the box opening station may be required.

The residual content of the wafer cassette is high after cleaning. Should it be cleaned first or should it be filtered first?
In most cases, check the cleaning agent, rinsing and drying conditions first. If the source of residuals is controlled, the back-end filtration pressure will be much smaller.

Can Aili Industrial help check the filtration during wafer cassette storage?
The local filtration mode can be checked based on the storage cabinet structure, circulating air volume and air release position. The specific configuration needs to be confirmed based on product information and site conditions.

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Key points for selection and acceptance inspection