Dust Free Workshop

Dust free workshop for optical microelectronics production

The definition of dust free workshop is to remove the pollutants such as dust particles, harmful air and bacteria from the air within a certain space, and to control the indoor temperature, humidity, cleanliness, indoor pressure, air velocity and air distribution, noise, vibration, lighting and static electricity within a certain demand range, which is given to a specially designed confined space.

In recent years, due to the innovation and development of technology, the demand for high precision and miniaturization of products is more urgent. For example, the research and manufacture of VLSI circuits has become a project that countries all over the world attach great importance to in the development of science and technology.

A dust free clean room for optical microelectronic production generally includes:

1. Clean production area;

2. Clean auxiliary room (including personnel purification room, material purification room and some living rooms, etc.);

3. Management area (including office, duty, management and rest, etc.);

4. Equipment area (including purification air conditioning system application, electrical room, high-purity water and high-purity gas room, cold and hot equipment room);

B. Purification principle of a dust free workshop of optical microelectronics production is as below: 

Air flow → primary purification → air conditioning → medium efficiency purification → fan air supply → pipeline → high efficiency purification air outlet → blowing into the room → taking away dust, bacteria and other particles → return air shutter → primary purification repeat the above process, so as to achieve the purpose of purification.

C. Purification parameters of a dust free workshop for optical microelectronics production:

Air change times: 100000 level ≥ 15 times; 10000 level ≥ 20 times; 1000 ≥ 30 times. Differential pressure: main workshop to adjacent rooms ≥ 5pa;

Average wind speed: 0.3-0.5m/s for 10 and 100 grades; temperature > 16 ℃ in winter; temperature < 26 ℃ in summer; fluctuation ± 2 ℃;

The temperature is 45-65%; the humidity of GMP powder workshop is about 50%; the humidity of electronic workshop is slightly higher to avoid static electricity.

Noise ≤ 65dB (a); fresh air supplement is 10% - 30% of total air supply; illumination is 300lx.

D. Structural materials for dust free workshop of optical microelectronic 

1. The wall and ceiling of a dust free workshop is generally made of 50mm thick insulation sandwich panel, which is characterized by beautiful appearance and strong rigidity. Arc wall corner, door, window frame, etc. are generally made of special aluminum oxide profiles.

2. The floor can be epoxy self-flowing floor or high-grade wear-resistant plastic floor. If there is anti-static requirement, the anti-static type can be selected.

3. The air supply and return pipes are made of hot-dip zinc plate and pasted with flame-retardant pf foam plastic plate with good purification and heat preservation effect.

4. The high-efficiency air supply outlet is made of stainless-steel frame, which is beautiful and clean. The perforated mesh plate is made of baking varnish aluminum plate, which is rust free and dust free, so it should be cleaned.

E. Optical microelectronic dust free workshop solutions:

In the design process of a dust free workshop, it is necessary to strengthen the analysis and understanding of the design scheme of purification engineering in the optical microelectronics industry, and determine the required cleanliness, temperature and humidity according to the requirements of its specific production process. Then, according to the specific situation of the clean room project, considering the economic bearing capacity, and combining various factors to determine which purification scheme to adopt, so as to design a scheme that can meet the production and use requirements of end user, with reasonable project cost, economic and energy saving.

1. Analysis of dust free workshop design option 1 Combined air handling unit + chiller + efficient air supply outlet:

This is the most traditional design of purification air conditioning system. The combined air treatment unit contains various functional sections, such as mixing section, primary filter section, surface cooling section, secondary return air section (or intermediate section), heating section, humidification section, medium efficiency filter section, fan section, etc. Its cold source is provided by water chiller.

advantage:

(1). The air treatment effect is good, because the air is treated centrally, the pollution degree is low in the process of air supply. The temperature and humidity of the air supply are controlled accurately;

(2). It is more suitable for plants with centralized cooling sources or larger plants;

(3). The air conditioning cold and heat sources can be shared or independent with the common air conditioning system of the plant;

(4). Low maintenance frequency;

(5). The noise in the dust free workshop is low.

Disadvantages:

(1). It is necessary to have a matching refrigeration room or an outdoor space for the heat pump unit. In addition, the air conditioning room where the combined air treatment unit is placed, such as the 25000m3 / h combined air treatment unit, is usually about 6450 × 1850 × 2250mm in overall dimension. It is difficult for the old plant reconstruction project to empty a 20-30 ┫ machine room;

(2). High cost.

Characteristic:

(1). It is suggested that fresh air should be mixed with return air after centralized treatment, so as to reduce the burden of surface cooling section;

(2). This kind of scheme can be generally applied to lower clean and dustless plants with higher cleanliness, such as class 100, class 1000 or class 10000, class 100000, etc.

2. Analysis of dust free workshop design option 2: Water cooled cabinet machine+booster air cabinet+high-efficiency air supply outlet:

Compared with option 1, this is a relatively simple air conditioning scheme. It can greatly reduce the area of the machine room. The water-cooled cabinet can be arranged in the smaller machine room or the dust free workshop according to the specific situation. The booster fan cabinet can also be arranged in the machine room or hung in the machine room or in the mezzanine.

advantage:

(1). The effect of air treatment is better, and the air after treatment is less polluted in the process of air supply. The temperature and humidity control effect of the air supply can achieve better control. It is mainly controlled in the air handling unit (booster fan cabinet);

(2). Flexible layout. Self-cooling source;

(3). Large and small plants, new and old plants are applicable;

(4). Low maintenance frequency;

(5). The noise in the workshop is low.

Disadvantages:

(1). A small area of machine room is needed. Cooling tower and cooling water pump shall be placed;

(2). Air conditioning unit and air conditioning treatment unit shall be arranged centrally;

(3). Low cost.

(4). Features: this option can be primary return air or secondary return air, depending on the size of the workshop; this kind of scheme can generally be applied to clean and dust-free workshops with cleanliness of class 1000, class 10000, class 100000, etc.

3. Analysis of dust free workshop design option 3: Split air conditioning cabinet unit+FFU air supply outlet:

This is the simplest air conditioning design. The split air-conditioning cabinet is directly arranged in the workshop and enclosed with color steel, and then the air outlet (with primary filter screen) is opened on the color steel plate at the air outlet of the cabinet; the filter unit FFU of KLC fan is evenly arranged on the ceiling. This scheme is suitable for the dust-free workshop with low indoor temperature and humidity accuracy requirements.

Advantages:

(1). It does not need to occupy the area of the machine room, and the layout is very flexible;

(2). Can meet the air cleanliness;

(3). The lowest cost. The initial investment of such dust-free workshop is about 400000;

(4). Good uniformity of air supply.

Disadvantages:

(1). Poor temperature and humidity control;

(2). Can meet the air cleanliness;

(3). FFU maintenance frequency is high;

F. Analysis of design scheme of clean room in optical microelectronics industry

1. Cleanliness of dust free workshop:

The brief process of LCD screen making is as follows: cleaning → printing orientation film → friction → sealing the printing layer to distribute the spacer → combination → marking and cutting → LC injection → sticking polarizer → final screen making inspection.

In this design, it refers to some dust-free workshops of the end process, and its purification cleanliness is generally class 1000 or class 10000 or class 100000. The dust-free workshop of backlight screen is mainly the stamping workshop, assembly workshop and other dust-free workshops of this kind of products, and its cleanliness is generally class 10000 or class 100000.

2. Indoor air parameter requirements:

(1). Temperature and humidity requirements: the temperature is generally 24 + 2 ℃, and the relative humidity is 55 + 5%.

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(2) There is a lot of fresh air. Due to the large number of personnel in such dust free workshops, the following maximum values can be taken according to the following values: 10-30% of the total air supply volume of the non-unidirectional flow clean room; the fresh air volume required to compensate the indoor exhaust air and maintain the indoor positive pressure value; and the fresh air volume of each person per hour in the room shall be ≥ 40m3 / h.

(3) Large air supply. In order to meet the cleanliness and heat and humidity balance of the clean room, a large air supply volume is required. For a dust free workshop of 300 square meters with a ceiling height of 2.5 meters, the air supply volume of 300 × 2.5 × 30 = 22500 m3 / h (air change times, no less than 25 times / h); for a dust free workshop of 100000 levels, the air supply volume of 300 × 2.5 × 20 = 1500 m3 / h (air change times, no less than 15 times / h).

For design of dust free clean room of conventional electronic workshop, air conditioning design scheme should be selected according to the production process requirements of electronic workshop and end user's economic conditions, in order to meet the requirements of production process as the premise. According to the past experience, the air conditioning scheme of combined air handling unit can be selected for high requirements; for low requirements and low initial investment, the cabinet + FFU can be selected. In a word, the choice of specific scheme depends on the specific situation.