How to choose EFU filter without partition? Efficiency, resistance, sealing and complete machine matching methods

When selecting an EFU filter without partitions, the most common mistake is to only look at the efficiency level. H14 is written in the specification sheet, the supplier quoted the price, and the selection seems to have been completed. But after the partition-less filter is installed in the EFU, its resistance characteristics directly determine whether the fan is at the working point, the sealing method determines whether the box structure needs to be modified, and the pleat height and frame thickness determine whether the tens of millimeters of space in the equipment are enough. Choosing a filter without partitions essentially means choosing a component that matches the entire EFU machine, rather than choosing an independent filtering device. Aili Industrial's EFU manufacturing system covers filter self-production and complete machine assembly. The efficiency, resistance and sealing structure of the partition-less filter can be aligned with the fan working point in the same system, eliminating the need to transfer parameters between the filter factory and the complete machine factory.

Efficiency level: first look at what the process requires, and then look at how the standards are divided

The efficiency level of the filter without partitions is divided according to the EN 1822 standard. The filtration efficiency of H13 for 0.3μm particles is ≥99.95%, H14 is ≥99.995%, and U15 is ≥99.9995% for 0.12μm particles. The numbers don't seem to make much difference, but in the application of equipment-side EFU, the choice between H13 and H14 often depends on the sensitivity of the process section to particles, rather than 'higher is better'.

The filter efficiency selection of the equipment-side EFU should be considered together with the division of clean areas. H14 or higher is usually required in the wafer exposure area or near the bonding workbench; H13 may be sufficient in the transfer mechanism area or in the general equipment internal microenvironment. If the equipment process involves a boron-sensitive bonding interface, you also need to confirm the filter paper type - traditional glass fiber filter paper may release boron, and PTFE filter material is an optional direction. If the efficiency level is selected high, the resistance will increase, and the fan power consumption and noise will increase accordingly; if the efficiency level is selected low, the cleanliness will not meet the standard. The starting point for selection is process requirements, not the highest grade on the standard list.

Resistance and fan operating point: No partition does not mean low resistance

The structural feature of the filter without partitions is that hot melt adhesive is used instead of aluminum foil partitions, which can achieve a larger filtration area under the same thickness, but this does not mean that its resistance is necessarily lower than that with partitions. The resistance depends on the filter paper material, pleat height, pleat spacing and head wind speed. Partition-less products with pleat heights of 55mm, 70mm, and 75mm can reduce resistance while improving filtration efficiency, but the premise is that the pleat spacing is even and the airflow distribution is reasonable. If the pleat spacing is too close, the frictional resistance of the air flow in the inter-pleat channel will increase.

When choosing a filter without partitions, you must look at the initial resistance and final resistance together. The initial resistance determines whether the fan is in the high-efficiency zone after starting, and the final resistance determines whether the fan has room to maintain air volume at the end of the filter's life. The fan working point of EFU is selected based on a certain resistance value. If the initial resistance of the filter is 20% higher than the design value, the fan may deviate from the optimal efficiency point from the beginning; if the fan can no longer maintain the air volume when the final resistance reaches the replacement threshold, the cleanliness will drop before replacement. In the EFU project, Aili Industrial checked the fan working point according to the target air volume and filter resistance curve, so that the resistance change range of the filter without partitions falls within the adjustable range of the fan.

Sealing method: The frame of the filter without partitions determines how to install it.

There are usually two ways to seal the filter without partitions in the EFU: a sealing gasket is used to compress the filter frame and the EFU box, or a liquid tank is used to seal. The compression seal has low cost and simple structure, but has high requirements on the flatness of the box installation surface and the uniformity of the pressing force; the liquid tank seal has better reliability, but requires the box to have a corresponding knife edge structure and liquid tank space, which may not fit in the ultra-thin EFU.

When choosing a filter without partitions, the sealing method must be confirmed together with the EFU box structure. The material and thickness of the filter frame determine whether the frame will deform when pressed - the aluminum alloy frame is rigid enough but heavy, and the galvanized sheet frame is light but thin-walled and easy to warp under the bolt pretightening force. The material (polyurethane or silicone) and hardness of the gasket affect compression rebound. If the hardness is too low, the pressure will not be tight, and if the hardness is too high, greater compression force will be required. Aili Industrial's high-efficiency filters use polyurethane or silicone sealant. Each unit is scanned and tested for leaks one by one before leaving the factory. When the EFU is assembled, the sealing surface of the filter frame and the box is marked with the compression method and compression amount requirements in the confirmation diagram.

Whole machine matching: changing direction and space constraints

Another selection dimension for baffleless filters is the direction of change. The equipment-side EFU is installed inside the machine, and filter replacement often needs to be completed in a limited space. Bottom replacement, side replacement, or top replacement depends on the installation location and surrounding structure of the EFU. When selecting a filter, make sure there are handles or notches on the frame that facilitate removal and installation, and whether additional clearance is required when the filter is pulled out of the box.

Ultra-thin EFU (such as the 70mm thickness model) has tighter constraints on the thickness of the filter. The filter itself without a partition is thinner than one with a partition, but the thickness of the frame and the protrusion of the gasket still occupy the Z-axis space. When selecting, the total height including the sealing gasket should be compared with the internal clear height of the EFU box, rather than just the nominal thickness of the filter. Aili Industrial's 70mm ultra-thin EFU can be configured with filter specifications and replacement directions according to the equipment drawings. The assembly relationship between the filter and the box is marked on the confirmation drawing.

Misunderstandings to avoid

You should avoid selecting filters only based on efficiency level without checking the resistance and fan operating point. You should avoid equating no partitions with low resistance. You should avoid choosing filters with too thick frames or excessively protruding gaskets in ultra-thin EFUs. You should avoid placing orders without confirming the replacement direction. You should avoid using filter sample parameters to replace the actual air volume data of the EFU complete machine after assembly. The core of EFU partitionless filter selection is not 'as long as the efficiency is high enough', but that the efficiency, resistance, sealing and replacement methods form an assembleable, operable and maintainable match with the EFU complete machine.

Related questions and answers

Should I choose H13 or H14 for EFU partitionless filter?
Look at the division of clean areas inside the equipment. H14 is typically required in exposed areas of the wafer or near bonding interfaces; H13 may be sufficient in transfer areas or general microenvironments. If the efficiency is selected to be one level higher, the resistance will increase, and the fan power consumption and noise will increase accordingly. It needs to be checked with the fan operating point, and you cannot just look at the efficiency number.

Does a filter without baffles have lower resistance than a filter with baffles?
uncertain. The partition-less structure can achieve a larger filtration area under the same thickness, but the resistance depends on the filter paper, pleat height and headwind speed. When the pleat spacing is too close or the filter material is improperly selected, the resistance may not be low. When selecting a model, you should look at the resistance-air volume curve provided by the supplier, rather than just relying on the words 'no partitions'.

How much space does an ultra-thin EFU filter require?
Depends on the direction of replacement. Bottom replacement requires extraction space under the filter, and side replacement requires side clearance. When selecting, confirm whether the filter frame has a handle and whether it needs to be tilted when pulling it out. The internal space of the ultra-thin EFU is tight. It is recommended to mark the replacement path in the confirmation diagram instead of making an on-site judgment after arrival.

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Aili Industrial EFU selection and procurement support

Aili Industrial's EFU manufacturing system covers filter self-production and complete machine assembly. The partition-less filter can match the efficiency level and resistance specifications according to the EFU target air volume and fan operating point. The sealing structure and replacement direction are marked together with the box in the confirmation diagram. For ultra-thin models, the assembly relationship between the total height of the filter including the sealing gasket and the net height of the box can be checked according to the equipment drawings.

Learn about Aili Industrial EFU products and customized configurations. Check out the compact models.70mm ultra-thin EFU , the entire machine structure can be viewedEFU equipment fan filter unit , non-standard interface can be viewedCustomized EFU , filtering package can be viewedHEPA and ULPA air filters . Please submit the equipment cleanliness level requirements, EFU model and installation space dimensions to facilitate confirmation of filter efficiency, resistance and sealing configuration.