How to cooperate with chemical filtration and particle filtration in LCD workshop?

LCD production - including TFT array, box forming, module and other processes - the requirements for a clean environment mainly focus on particle control. Workshops are usually equipped with primary-efficiency, medium-efficiency, and high-efficiency filtration sections, and some even have FFUs all over the ceiling. The particle index is generally controlled relatively stably.

But if you only control the particles, some problems will still arise. For example, some processes use organic solvents, photoresists, and cleaning agents. These materials evaporate into the air to form gaseous pollution that cannot be stopped by particle filters. Over time, it may accumulate in equipment optical components, product surfaces, or ventilation ducts. Therefore, the filtration system in the LCD workshop needs to consider particle control and gaseous pollution control separately, and then coordinate them in the system. For specific division of labor logic, please refer to Discussion of the difference between chemical filters and HEPA filters .

Identify loads by process

The pollution objects produced by different processes in the LCD workshop are different, and the coordination methods must be looked at separately.

Array process. Involves photolithography, etching, film deposition and other steps. Photoresist, developer, and etching gas may release organic vapors or acidic components. Particle control requirements are high, and gaseous pollution also needs attention.

Boxing process. Operations such as liquid crystal dripping, frame sealing glue, alignment and lamination, etc. Adhesives and liquid crystal materials may release trace amounts of organic matter. This process is sensitive to both particles and gases.

Module process. Polarizer attachment, driver IC binding, and backlight assembly. Involving adhesives and cleaning agents, VOC may be released. Particle control requirements are slightly lower than in the array process, but gaseous contamination may affect appearance and reliability.

Cleaning and material storage. The volatilization of the cleaning agent and the storage of materials in the open may continue to release gaseous components. This part of the source is easily overlooked. For specific investigation methods, please refer to whether to do air sampling before choosing a chemical filter . Discuss

Determine filter layers and paths

After identifying the pollution objects, consider how to arrange the filter sections in the system.

It is common practice to put particle filtration first and chemical filtration last. The initial and medium effects intercept dust first and reduce dust coverage of chemical media. Terminal high efficiency or ULPA is responsible for final particle control. The chemical filtration section is placed after the intermediate efficiency and before the terminal efficiency, or integrated with the terminal efficiency in the FFU. For specific configuration, please refer to Discussion on the division of labor between chemical filters and primary filters .

The location of the chemical filtration section depends on the source of pollution. If gaseous pollution mainly comes from external fresh air, it is more straightforward to set up a chemical filtration section in the fresh air unit. If the release mainly comes from indoor processes, it can be processed on the return air or FFU circulation path. For specific differences, please refer to Why does MAU need to configure the chemical filter section and Discussion of what localized contamination can be treated by FFU plus chemical filter .

The sequence is not fixed and must be confirmed based on the medium powder loss, gas release and maintenance structure. Some chemical media may produce trace amounts of dust. If placed behind the high-efficiency terminal, this part of the dust will directly enter the workshop. Put before efficiency, efficiency can play an interceptive role. For specific differences, please refer to Discussion on whether the FFU chemical filter should be placed before or after the HEPA .

Air volume distribution and resistance should be calculated together. Adding a chemical filtration section will increase the total system resistance. Whether the original fan can maintain the target air volume needs to be calculated based on the actual working point. For specific methods, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity consumption .

Set acceptance methods separately

Particles and gas are two types of indicators, and the acceptance must be done separately.

Particle side acceptance. Terminal high-efficiency or ULPA performs efficiency confirmation, installation sealing inspection and on-site leak detection according to the corresponding level. The detection methods and judgment standards are implemented according to the requirements of particle filters. Can be referenced Description of HEPA high efficiency filter .

Gas side acceptance. The chemical filtration section conducts inlet and outlet concentration tests based on target components to confirm the removal effect. The sampling points must be representative of the air before and after the filtration section, and the detection method must be suitable for the target gas. For specific methods, please refer to Discussion of sampling points for chemical filter performance verification .

Maintenance basis is different. The replacement of the particle filter depends on the pressure difference and leak detection results; the replacement of the chemical filter section depends on the gas processing capacity consumption, and there may be no obvious pressure difference change. The maintenance rhythms of the two are different, and the ledgers must be recorded separately. For specific differences, please refer to Discussion on whether the chemical filter can be replaced based on the pressure difference .

You cannot use particle data only to evaluate gas effects, nor can you only measure gas and ignore particles. The two types of indicators are archived separately, so that problems can be quickly located.

Pay attention to cross-process impacts

There are many processes in the LCD workshop and the air flow organization is complex. The filtering configuration must consider the interaction between the processes.

Shared return air may cause cross-contamination. If different processes share a return air system, gaseous components released from one process may enter another process through the return air. At this time, it is necessary to check the relationship between the return air partition and the pressure difference, and add a chemical filtration section to the return air path if necessary. For details, please refer to Discussion on how odors in multi-story factory buildings interact with each other and how chemical filtration should be partitioned .

Re-evaluate after process adjustments. If the cleaning agent, photoresist or adhesive is changed in a certain process, the released components may change. Whether the original chemical filtration section is still suitable needs to be rechecked. For specific methods, please refer to Discussion on why chemical filters should be selected according to the target gas .

The device side can be protected individually. For equipment or workstations that are particularly sensitive to gaseous pollution, local chemical filtration can be installed on the air inlet path of the equipment. For device-side applications, please refer to Discussion on why EFU needs supporting chemical filters .

Project judgment example

After a certain LCD module workshop had been running for a period of time, unknown foggy traces appeared on the surface of some products, but the particle detection was normal.

The investigation confirmed that some kind of adhesive was used in the workshop, which released trace amounts of organic vapor during the curing process and deposited on the surface of the polarizer to form foggy traces. Particle filtration systems do not have the ability to handle this type of gas.

Adjustment direction: Add a chemical filtration section for organic vapor on the return air path of the module process, and strengthen local exhaust at the adhesive use point. The organic vapor concentration, air volume and temperature and humidity conditions were checked before configuring the filter section. After adjustment, the foggy traces on the surface were reduced, and the particle index was not affected.

This case illustrates: Chemical filtration and particle filtration in the LCD workshop must be divided according to the pollution objects and cannot replace each other. involving When selecting a chemical filter product series , it is recommended that the pollution data, sensitive objects and system conditions of each process be provided to the supplier for verification.

Key points for selection and acceptance inspection

About Aili Industrial’s LCD workshop filtration package

For particle control and gaseous pollution control in the LCD workshop, the two types of requirements need to be confirmed separately at the planning stage, and then uniformly checked at the system level.

Aili Industrial has independent manufacturing capabilities in filters, motors, fans, control systems and sheet metal processing, and can provide HEPA/ULPA filter and chemical filter product series. For projects involving both particle and gas control, the pollution data, protection objects, air volume and installation space of each process can be combined to assist in checking the configuration and division of labor of the filter section. When the filter is matched with MAU, FFU, EFU and other equipment, the resistance, interface and maintenance methods can be confirmed uniformly.

Related products:Chemical filter product series、HEPA high efficiency filter、FFU comes with chemical filter . A separate list of particle control targets and gas targets is provided during the inquiry to help confirm the appropriate combination solution. The specific configuration is subject to the technical documents and test results confirmed by the project.