1. The main purpose of air purification is to remove suspended dust particles in the air, create a clean working environment, and ensure the high quality, high precision, high purity and high yield of products. With the continuous development of PCB industry, the requirements of small circuit and high precision make the air conditioning clean room play a more important role. How to maintain and improve the cleanliness of the clean room is an important basic problem.
2. Source of Dust in Clean Room
The structure of the clean room is like a sealed whole, and its dust sources mainly include the following aspects:
2.1 In order to compensate for the fresh air needed for indoor exhaust and maintain the positive pressure value, the air filter is the last pass of air purification. For the well-qualified filters, the main problem is the sealing of the air supply outlet, such as the integrity and performance of the sealing strip, which can cause the quality of the air supply outlet. If the surrounding air leaks, the cleanliness around the air outlet will obviously deteriorate.
2.2 Items entered the entrainment:
(1) Dust is brought into the automatic transmission equipment;
(2) Dust is brought into the process of material entry.
2.3 Compressed air used in clean room brings about: In clean room, many PCB production equipment use pneumatic power structure, such as: automatic film sticker, exposure machine, screen printer, etc., and pneumatic components will be discharged after using compressed air, because the general compressed air does not carry out its higher requirements of purification process (such as internal pollution of compressed air trachea, etc.). Therefore, when compressed air is widely used in clean rooms, the cleanliness of clean rooms will be affected.
2.4 Personnel entering and leaving the room bring in dust: Personnel entering the clean room self-cleaning problems, mainly in the following aspects:
(1) irregular clothing; exposed skin, hair and other parts;
(2) Dust is entrained in the process of laundry cleaning, which leads to dust being brought into the purification plant after dressing.
(3) Personnel entering and exiting air shower doors are not managed in accordance with regulations to carry out necessary air shower and dust removal process.
2.5 The overall envelope structure of the room is tightness, which is mainly the envelope structure of the room and the selected materials. The main structure of the clean room building, no matter what kind of structure, must satisfy the following conditions:
(1) Cracks should not occur due to temperature changes and vibration;
(2) It is not easy to produce dust particles, and it is difficult to attach particles.
(3) Low hygroscopicity;

(4) In order to maintain indoor humidity conditions, thermal insulation should be high.

3. Maintenance and Maintenance of Purification Equipment
This is an important defense line to ensure high cleanliness, mainly in the following aspects:
3.1 Clean room envelope structure:
(1) The overhead floor should be cleaned regularly according to the actual production situation, and the underfloor chute should be replaced in time if it is damaged.
(2) The partition walls and ceilings should be inspected regularly for cleaning and sealing.
(3) The doors and windows of the clean room should be maintained regularly and the sealing performance should be checked.
3.2 Clean room parameters:
(1) Prevent the outside dust from intruding into the clean room: the positive pressure value in the clean room should be > 0.5mmAq;
(2) Operating environment condition of purification workshop: Temperature, humidity and the number of dust particles should be measured regularly every day to ensure that abnormal quality data need to be dealt with urgently.
(3) Moisture and drying will have an impact on production. When relative humidity exceeds 75%, the corrosion rate tends to rise in a straight line. Machinery equipment and products are easy to rust, causing losses to production and material storage. The relative humidity is less than 45%. Electrostatic charge is easy to accumulate and bring harm. In the process of PCB production, the control accuracy of humidity has a great influence on exposure alignment, so the control accuracy of humidity is a very important basic problem.
3.3 Maintenance of air handling hood:
(1) Filter management: regular inspection and replacement;
(2) Blower, inspection and cycle.
4. Clean room management, high clean environment need strict management system cooperation to achieve.
4.1 The movement or movement of workers or other personnel in the clean room is the source of dust, which directly affects the process and also affects the disturbance of airflow. To prevent and control the expression, the following items should be noted:
(1) Personal conversations unrelated to homework should be avoided as far as possible;
(2) Unnecessary actions should be avoided as far as possible to prevent turbulent flow and dust.
(3) In order to control the amount of dust, people should walk and work quietly.
(4) After smoking or eating, those who have not passed more than half an hour should not enter the clean room.
4.2 Selection, arrangement and maintenance of production equipment:
(1) Production equipment which is not easy to produce dust should be selected in the clean room.
(2) When planning the allocation space of each equipment, the principle is easy to clean.
(3) Vacuum pumps and other contamination-prone equipment are set outdoors in the daytime;
(4) When installing water, electricity and gas pipeline systems, their structures should be easy to clean and not easy to accumulate dust. Generally, they should not be placed on the floor.
(5) Production and related equipment should be cleaned regularly to avoid accumulation of dust;
(6) When the equipment maintenance is easy to produce dust particles, it should be carried out outside the clean room as far as possible.
(7) The company's foreign associates shall inform the regulations for entering and leaving the dust-free room, and the engineers in charge shall supervise the workers nearby.
4.3 Application of Automatic Production Equipment
(1) The establishment of automatic transmission system can reduce the pollution caused by personnel, but the entry and exit of automatic transmission equipment into the room should be paid special attention to: in PCB production system, attention should be paid to the entrance and exit of development and grinding board equipment, because there are baking plate section and spray section in such equipment, so the outlet of the plate has positive pressure air discharge, which should be handled properly, otherwise, the air flow into the room should be reversed. Room cleanliness will be seriously affected. Generally, the upper and lower double rollers can be used at the outlet of the equipment to reduce the reverse flow of air, but attention should be paid to the problem of equipment placement.
(2) The Wrong layout scheme: when outdoor production equipment imports materials into the clean room, the reserved space is too small. When indoor positive pressure air is discharged outdoors, it is blocked by outdoor high readiness, and can not be discharged, and can not wash away the air flow from the production equipment. In general, the air pressure of the fan of production equipment is far greater than the positive pressure value of the purification air-conditioning room, so the production equipment is in the production equipment. The outdoor air flow caused by the Department rushes into the room, thus affecting the cleanliness of the room.
(3) Better layout scheme: When the outdoor production equipment imports materials into the clean room, the reserved space is large. After observation, the distance is more than 50 cm, and the upper and lower sides of the conveyor belt can not be sealed, so as to facilitate the indoor air flow to wash away the positive air flow of the production equipment, and smoothly discharge the outdoor.
4.4 Input and Output Management of Raw Materials
(1) Produced articles entering the purification room need surface dust removal before they can enter.
(2) The way of "clean transfer window" is adopted for the entry and exit of articles.
(3) Items unrelated to production are not allowed to be brought into the clean room.
4.5 Management of Indoor Goods
(1) Tools shall be collected in boxes or cabinets with lids and placed in fixed places;
(2) Do not place objects above the airflow in the working area to avoid affecting airflow distribution and cross-contamination;
(3) Clean set of special tools shall not be taken out for use outdoors.
With years of experience in design and construction of purification projects and strong technical strength, Ed Purification has established close cooperation with many well-known enterprises. In the clean workshop, purification engineering, clean engineering, environmental protection engineering, sewage treatment, medical purification and other fields, have excellent performance! To learn more about the medical purification industry, please pay attention to the Wechat Public No. Aide-188 (Ed Purification and Oxygen Supply)