PCB Circuit Board Manufacturing Cleanroom

1.The Importance of Cleanrooms for the PCB Manufacturing Industry
1) Overview of PCB Circuit Board Manufacturing Industry
  B (Printed Circuit Board) manufacturing industry is an important foundation of the electronic information industry: metals, oxides, nitrides and other materials are deposited on glass substrates to form a homogeneous and stable film layer. It uses printing, etching and other processes to make conductive materials such as copper foil into specific circuit patterns to achieve electrical connections and signal transmission between various components in electronic equipment. It is widely used in many fields such as computers, communications, consumer electronics, automotive electronics, industrial control, medical equipment, etc.

2)The Importance of Clean Rooms to PCB Manufacturing Industry
Clean rooms play an extremely important role in the PCB manufacturing industry, mainly in the following aspects:
â‘ Ensure product quality and yield: During the PCB manufacturing process, even tiny particle pollutants may cause electrical performance problems such as short circuits and open circuits. At the same time, chemical substances in the air, such as acid, alkali, salt and other gaseous pollutants, may also react with the metal layer or chemical substances on the surface of the PCB, causing corrosion, oxidation and other problems, reducing the reliability and service life of the PCB. The cleanroom uses a strict air filtration system to remove dust particles and microorganisms in the air to ensure the cleanliness of the production environment. This helps reduce short circuits, open circuits and other problems caused by contamination, and significantly improves the yield rate and quality stability of PCB products. 

â‘¡Improve production efficiency and reduce costs: In a clean environment, the operation of production equipment is more stable, reducing equipment failures and downtime caused by pollutants, while reducing the defective rate of PCB production and reducing rework and scrap caused by quality problems. In addition, reasonable equipment layout and material handling system design optimize the production process, improve the overall efficiency of the production line, and reduce production costs.

â‘¢Ensure employee health and safety: The clean room uses a good ventilation system and safety protection measures to effectively control the concentration of harmful chemicals and gases to ensure the health and safety of employees. At the same time, it is equipped with professional safety protection equipment and emergency rescue measures to deal with possible accidents.

â‘£Comply with industry norms and standards: In the PCB manufacturing industry, there are a series of quality standards and certification systems both internationally and domestically, such as ISO 9001 quality management system, ISO 14001 environmental management system, etc. These standards usually require companies to control environmental factors during the production process to ensure the stability and reliability of product quality. The construction and operation of clean rooms meet the requirements of these standards, which will help companies pass relevant quality certifications and enhance their credibility and market recognition. In addition, environmental protection laws and regulations in some regions have strict requirements on pollutant emissions and environmental control in industrial production processes. Through effective air purification and waste treatment systems, cleanrooms can reduce environmental pollution during the production process and ensure that the company's production activities meet the requirements of environmental protection laws and regulations.

⑤Promote technological progress in the industry: With the continuous development of semiconductor technology, circuit board manufacturing has higher and higher requirements for the cleanliness and stability of the production environment. Cleanrooms meet these high requirements by adopting advanced air purification, temperature and humidity control, and electrostatic protection technologies, and promote the continuous progress of the PCB manufacturing industry.

â‘¥Improve enterprise competitiveness: PCB board manufacturers with cleanroom production capabilities can take orders for high-end products and meet customers' strict requirements for product quality and performance, thereby occupying an advantageous position in market competition. For some industries that have extremely high requirements for electronic product quality and reliability, such as aerospace, national defense, and medical industry, customers are more inclined to choose suppliers with cleanroom production conditions.

2.The Key Role of PCB Cleanroom in Specific Production Process
1) Photolithography
♦ Ensure photolithography accuracy: Photolithography is a key process to transfer the designed circuit pattern to the copper-clad board, and it has extremely high requirements for environmental cleanliness. The cleanroom can effectively filter dust particles in the air to prevent them from falling on the photoresist or mask. If there are particulate impurities, the photolithography pattern will be deformed, blurred or defective, resulting in a decrease in the circuit line width accuracy, affecting the performance and function of the PCB, such as errors or delays in the signal transmission of the integrated circuit‌
♦ Stable photolithography environment: The photolithography process needs to be carried out in a stable temperature, humidity and airflow environment. The cleanroom uses a precise environmental control system to ensure that the photolithography equipment is in the best working conditions, reduce the change in photoresist performance and equipment precision drift caused by environmental factors, thereby improving the repeatability and consistency of the photolithography process and ensuring that the photolithography quality of each PCB can meet high standards.

2) Etching Process
♦ Prevent impurities from contaminating the etching solution: In the etching process, the etching solution needs to accurately remove the unnecessary copper foil to form an accurate circuit pattern. The clean environment of the cleanroom can prevent external impurities from entering the etching solution, avoiding the etching solution from being contaminated and affecting the etching rate and uniformity. If impurities are mixed into the etching solution, it may cause uneven etching, inconsistent circuit line thickness, short circuit or open circuit, and reduce the yield rate of the PCB.
♦ Avoid surface contamination after etching: The etched PCB surface is very sensitive and easily can absorb dust and pollutants in the air. The cleanroom can provide a clean air environment to prevent the etched PCB surface from being contaminated again and ensure the smooth progress of subsequent processes. Otherwise, surface pollutants may affect the quality of subsequent processes such as solder mask and electroplating, and reduce the reliability and service life of the PCB.

3)Electroplating Process
♦ Ensure the quality of the coating: Electroplating is the process of depositing a metal layer on the surface of a PCB or on the wall of a hole to improve conductivity, solderability and oxidation resistance. The low dust environment of a cleanroom can prevent dust and other particles from being adsorbed on the electroplating surface, avoiding the formation of coating defects such as pitting and pinholes, thereby obtaining a uniform, dense, smooth and high-quality coating.
♦ Maintaining the stability of the plating solution: The stability of the plating solution is crucial to the electroplating effect. Clean rooms can effectively control the humidity and chemical pollutants in the air to prevent them from entering the plating solution and affecting the composition and performance of the plating solution. Humidity changes may cause certain components in the plating solution to hydrolyze, and chemical pollutants may react with metal ions in the plating solution, which will destroy the balance of the plating solution and affect the quality of electroplating. Clean rooms can provide a stable storage and use environment for the plating solution.

4)Lamination Process
♦ Prevent foreign matter from being mixed in: The lamination process of multi-layer PCB requires multiple insulating layers and conductive layers to be pressed together accurately. Cleanrooms can prevent foreign matter such as dust and fibers from entering between layers, preventing problems such as short circuits or reduced insulation performance after lamination. Even tiny foreign matter may form a conductive path between layers or destroy insulation performance, affecting the overall performance of multi-layer PCB.
♦ Ensure the stability of the lamination environment: The lamination process needs to be carried out under certain temperature, humidity and pressure conditions. The environmental control function of the clean room can ensure the stability of these conditions, making the lamination process more uniform and reliable, improving the bonding strength and adhesion between layers, and ensuring the structural integrity and electrical performance of multi-layer PCBs.

5)Bonding Process
♦ Protect chips and solder joints: The bonding process is a key step in connecting electronic components such as chips to PCBs, and needs to be carried out in a highly clean environment. A cleanroom can prevent dust, water vapor and other pollutants from falling on the surface of chips and solder joints, avoid chip pin oxidation, solder joints or short circuits, and ensure the reliability of bonding and electrical connection performance.
♦ Improve bonding quality: In the bonding process, such as gold wire bonding, the environmental requirements are very strict. The clean air and stable environment of the cleanroom help improve the quality of bonding and reduce bonding defects, such as insufficient bonding strength and bond wire breakage, thereby improving the connection stability and signal transmission performance between PCB and electronic components.

3.Factors That Should be Focused on in PCB Circuit Board Cleanrooms
  PCB (printed circuit board) clean rooms are crucial in ensuring product quality and production efficiency. Factors that should be focused on include cleanliness, air purification system, temperature and humidity control, noise and lighting design, decoration materials and detail processing, floor plan layout and functional area division, etc.

1)Cleanliness
  The cleanliness of the PCB(printed circuit board) cleanroom is the primary concern, and different production processes have different cleanliness requirements. For example, key processes such as photolithography usually need to reach ISO 5 or even higher cleanliness. It is necessary to filter dust particles in the air through equipment such as high-efficiency air filters (HEPA) to ensure a clean environment. According to the ISO 14644-1 standard, the cleanliness level ranges from Class 1 to Class 9, and different levels correspond to different particle concentration requirements. For a Class 100 cleanroom, the cleanliness requirement is extremely high, that is, the number of dust particles in each cubic meter of air does not exceed 100 particles with a diameter greater than 0.1 microns.

2)Air Purification System
  The air purification system is the core of the PCB Circuit Board cleanroom. A three-stage or even four-stage filtration system should be used, and a sub-high efficiency filter or above must be installed at the end to ensure the cleanliness of the air.
♦ Reasonable design of airflow organization: Reasonable design of airflow organization can effectively remove pollutants, generally in the form of unidirectional flow or turbulent flow. Unidirectional flow can provide uniform and directional airflow to quickly remove dust particles; turbulent flow maintains a certain cleanliness through multiple air circulation and mixing. It is necessary to select the appropriate airflow organization method according to the production area and equipment layout to limit the diffusion of dust particles and maintain the stability and cleanliness of the air.
♦ Reasonable arrangement of air supply and return vents: The position and shape of the air supply vents will affect the distribution and uniformity of the airflow, while the position and number of the return vents are related to the smooth discharge of the airflow. Generally speaking, the air supply vents should be as close to the pollution source as possible, and the return vents should be set downstream of the airflow to ensure that pollutants can be discharged in time.
♦ Positive or negative pressure design: can prevent external pollutants from entering the workshop or clean air leakage.
♦ High-efficiency air filtration system: The AC cabinet is equipped with primary filter and medium-efficiency filters in sequence. The primary filter further filters larger particles in the fresh air, while the medium-efficiency filter mainly filters particles of 1-5μm, providing preliminary purification for the air entering the cleanroom and reducing the burden of the terminal HEPA filter. Finally, a HEPA filter is installed at the air supply end of the cleanroom, which can filter tiny particles with a particle size of 0.3μm and below or even 0.1μm, ensuring that the air sent into the cleanroom reaches the required cleanliness level. In addition, a primary filter is installed at the return air outlet of the cleanroom to intercept dust, fiber and other impurities in the indoor air, prevent them from entering the return air duct, and perform preliminary filtration on the return air.
♦ Regular inspection and maintenance: Regularly check the appearance of the filter to see if there is damage, deformation, excessive dust accumulation, etc. Clean or replace the filter regularly according to the use of the filter and monitoring data. The primary filter can be cleaned or replaced every 1-2 weeks according to the degree of contamination; the medium-efficiency filter is generally checked every 1-3 months and cleaned or replaced when necessary; the replacement cycle of HEPA filter and ULPA filter is generally 1-2 years, but if the cleanroom is used in a harsh environment or the production requirements are high, a shorter replacement cycle may be required.
♦ Performance monitoring: Regularly monitor the air quality in the cleanroom through equipment such as dust particle counters, detect parameters such as particle concentration and particle size distribution in the air, and evaluate the performance of the filtration system. If the air quality is found to be substandard, the filtration system should be checked in time to find out the cause and take appropriate measures.

3)Temperature and Humidity Control
Stable temperature and humidity help maintain the normal operation of production equipment, reduce static electricity and dust adsorption, and ensure product quality.
♦ Temperature: Temperature fluctuations will affect the physical properties of PCB materials and the accuracy of production equipment. Generally, the temperature needs to be controlled within the range of 22℃±2℃ to ensure the stability of processes such as photolithography and etching, and reduce material deformation and dimensional deviation. Humidity is also crucial to PCB production.
♦ Humidity: Too high humidity can easily cause the circuit board surface to get damp, leading to short circuits, corrosion and other problems; too low humidity can generate static electricity and damage electronic components. Generally, it is more appropriate to control the humidity at 45% - 65% RH.

4)Differential Pressure Control
♦ Pressure difference between different areas: To prevent external pollutants from entering the cleanroom and cross contamination between areas of different cleanliness levels, the pressure difference needs to be set reasonably. For example, a positive pressure of 5-10Pa should be maintained between the clean area and the non-clean area, and a high cleanliness area should also maintain a certain positive pressure on the adjacent low cleanliness area to ensure that the airflow flows from the clean area to the non-clean area.
♦ Dynamic balance: During the production process, it will affect the indoor pressure including the entry and exit of personnel and materials, the operation of equipment, etc. Therefore, it is necessary to equip with advanced pressure monitoring and regulation systems to adjust the supply and exhaust air volumes in real time to maintain the dynamic balance of the pressure difference.

5)Plane Layout and Functional Area Division
In order to ensure product quality and production efficiency, the PCB cleanroom needs to rationally plan the various functional areas of the workshop according to the production process, equipment layout and personnel flow to reduce dust diffusion and cross contamination.
♦ Loading area: Generally located near the entrance of the cleanroom, it is convenient for the handling and storage of raw materials. There needs to be enough space to place the raw material shelves and loading equipment. The ground should be flat and solid to bear the weight of the raw materials, and it should be isolated from other areas to prevent dust and other pollutants from entering.
♦ Printing area: Closing to the loading area, it is convenient for taking materials for printing operations. The temperature, humidity and cleanliness in the area must be kept stable to ensure printing quality. The equipment layout should take into account the operating space and maintenance channels, and anti-static measures should be taken to prevent static electricity from affecting PCB and ink.
♦ Exposure area: It has extremely high requirements for environmental cleanliness, temperature and humidity. It is usually set up in a relatively independent and quiet area to reduce external interference. Exposure equipment requires a stable power supply and water source. The access convenience of water and electricity lines should be considered during layout. At the same time, shading measures should be set up to prevent external light from interfering with the exposure process.
♦ Development area: adjacent to the exposure area, it is convenient for the PCB to be developed in time after exposure. The development process will produce waste water and waste gas, which requires a complete waste water treatment and waste gas discharge system. The ground must be treated with anti-corrosion to prevent the developer from corroding the ground.
♦ Etching area: Various chemical reagents are used in the etching process, which are corrosive and toxic. They should be set up in a well-ventilated area and equipped with an independent ventilation system and exhaust gas treatment equipment. A certain distance should be maintained between equipment to facilitate operation and maintenance, and anti-corrosion measures should be taken on the ground and walls.
♦ Electroplating area: It requires a large amount of water and electricity supply and waste water treatment facilities, which are generally located near the water supply and drainage system. Anti-leakage measures should be taken for electroplating tanks and other equipment to prevent leakage of electroplating liquid from polluting the environment. Sufficient ventilation equipment should be set up in the area to remove harmful gases generated during the electroplating process.
♦ Inspection area: Usually located at the end of the cleanroom, it has high requirements for cleanliness and must avoid external interference. The inspection equipment requires stable power supply and signal transmission. When laying out, the spacing and operating space between the equipment must be considered to facilitate inspection personnel to operate and record data.
♦ Gowning room: Divided into first and second changing rooms, usually located at the entrance of the cleanroom. The first changing room is used to change ordinary work clothes and shoes, and the second changing room is used to change clean clothes, wear masks and gloves, etc. The changing room should be equipped with enough wardrobes and shoe cabinets, and have good ventilation and lighting facilities.
♦ Air shower room: It connects the changing room and the production area, and is the only way to enter the cleanroom. The size and number of air shower rooms should be determined according to the flow of personnel in the cleanroom and production needs, ensuring that personnel can fully remove dust and impurities before entering the cleanroom.
♦ Tool storage area: It is used to store tools, fixtures and measuring tools used in the production process. Keep them dry and clean to prevent rust and contamination. Tool racks and lockers can be set up to classify and store tools for easy access and management.
♦ Equipment maintenance area: Generally located at the edge or corner of the clean room, with independent space for easy repair and maintenance of equipment. The maintenance area should be equipped with necessary maintenance tools and equipment, and protective measures should be taken to prevent dust and debris generated during maintenance from contaminating the cleanroom.
♦ Personnel passage: Ensure sufficient width, generally not less than 1.2 meters, to facilitate personnel passage and material handling. The passage floor should be flat and non-slip, and have a good connection with the production area and auxiliary area. At the same time, obvious signs should be set up to guide personnel to pass correctly.
♦ Material channel: Determine the width and height of the channel according to the material transportation method and flow rate. If a forklift or other transportation tool is used, the width is generally not less than 3 meters. The material channel should be closely connected with the loading area, production area and finished product area to ensure smooth transportation of materials.
When planning the layout of the PCB cleanroom, factors such as fire protection and safe evacuation should also be considered to ensure that personnel can evacuate quickly in an emergency. At the same time, a certain amount of expansion space should be reserved according to the company's development plan and future needs.

6)Noise Control
♦ The impact of noise on personnel and equipment: Excessive noise can affect the physical and mental health and work efficiency of personnel. Long-term exposure to high noise may lead to hearing loss, fatigue, lack of concentration and other problems. At the same time, noise may also interfere with some high-precision testing equipment and instruments, affecting their measurement accuracy and stability.
♦ Take effective noise reduction measures: Use low-noise AC systems, ventilation equipment and production equipment to reduce noise at the source. Use sound insulation materials such as sound-absorbing panels and sound insulation felt on the walls, ceilings and floors of the cleanroom to reduce the spread of noise. Arrange equipment reasonably, place equipment with high noise levels away from the work area, and take necessary sound insulation and shock absorption measures.

7)Monitoring and Alarm System
♦ Monitoring center: It is mainly composed of servers, monitoring software, display screens, etc. The server is used to store and process the collected data, while the monitoring software analyzes, processes and displays the data. The staff can view the various parameters and equipment operating status in the cleanroom in real time through the display screen, and can also perform data query, report generation and other operations.
♦ Environmental parameter monitoring: including temperature and humidity sensors, differential pressure sensors, dust particle counters, wind speed sensors, air volume sensors, etc., which are used to monitor the temperature, humidity, differential pressure, cleanliness, air flow speed and air volume and other parameters in the cleanroom in real time.
♦ Equipment operation status monitoring: By installing sensors or data acquisition modules on key equipment such as production equipment, AC systems, purification equipment, etc., the operating parameters and working status of the equipment, such as voltage, current, power, operating time, fault codes, etc., can be monitored in real time.
♦ Water quality monitoring: For the deionized water and other water used in the PCB production process, conductivity sensors, pH sensors, particle counters, etc. are set to monitor water conductivity, pH value, particulate matter content and other indicators.
♦ Data acquisition and transmission: The data acquisition system is responsible for collecting data obtained by various monitoring devices and converting them into digital signals. The data is transmitted to the server or data storage device of the monitoring center through a wired network (such as Ethernet) or a wireless network (such as Wi-Fi, ZigBee, etc.).
♦ Alarm function: Set the alarm threshold. When the monitoring parameters exceed the normal range or abnormal conditions occur, the alarm signal can be sent out in time to remind the staff to take corresponding measures. At the same time, the alarm system should have a remote alarm function, which can send the alarm information to the mobile phone of the relevant personnel or the monitoring center.

4.Differentiated Needs and Solutions for Cleanrooms in PCB Circuit Board Enterprises of Different Sizes
  PCB circuit board enterprises of different scales have different requirements for cleanrooms, which are mainly reflected in the area of cleanrooms, cleanliness level, production process requirements, cost control, etc. The following are the differentiated requirements and solutions for cleanrooms of PCB enterprises of different scales:
1)Small PCB Circuit Board Company
â‘  Features
♦ Limited space: The production site is small and it is usually difficult to divide a larger clean area. It is necessary to rationally layout the cleanroom within the limited space.
♦ Cost sensitivity: Funds are relatively limited, and there are strict control requirements on the construction and operation costs of clean rooms. It is hoped that basic production needs can be met at a lower cost.
♦ The process is relatively simple: It is mainly engaged in some conventional PCB production, and the cleanliness requirements are relatively low. Generally, the cleanliness level of 10,000 or even 100,000 can meet the production needs.
â‘¡ Solution
♦ Modular cleanroom: The modular cleanroom design can be flexibly combined according to the actual site and production needs. It is easy to install, can be put into use quickly, and has a relatively low cost.
♦ Local purification equipment: For some key processes with high cleanliness requirements, such as silk-screen printing and exposure, local purification equipment such as clean workbenches and laminar flow hoods can be used to achieve higher cleanliness in a smaller space.
♦ Simple filtration system: Equipped with a relatively simple air filtration system, mainly with primary and medium efficiency filters. The filters are replaced regularly to ensure the basic cleanliness of the air.

2)Medium PCB Circuit Board Company
â‘  Features
♦ Medium-scale cleanroom: As the scale of production expands, it is necessary to build a medium-sized cleanroom to meet the needs of multiple production lines, which places higher requirements on the layout of the cleanroom and the design of the logistics channel.
♦ Requirements for multiple cleanliness levels: In addition to the regular production areas requiring class 10,000 cleanliness, some special processes, such as lamination of multi-layer boards and production of inner-layer circuits, may require Class 1,000 or even Class 100 cleanliness levels.
♦ Stability and reliability: There are high requirements for the environmental stability and equipment reliability of the cleanroom to ensure the consistency and stability of product quality and reduce the product defect rate caused by environmental factors.
â‘¡ Solution
♦ Zoning design: Divide the cleanroom into different functional areas, such as production area, buffer area, equipment area, etc., make reasonable layout according to the cleanliness requirements of different areas, set up clean areas of different levels, and realize material transfer and personnel flow between different areas through facilities such as transfer windows and air shower rooms.
♦ Multi-stage filtration system: A multi-stage filtration system that combines primary, medium and high efficiency filters is used. According to the cleanliness requirements of different areas, the grade and quantity of filters are reasonably configured to ensure air quality.
♦ Intelligent monitoring system: Install an environmental monitoring system to monitor the temperature, humidity, pressure difference, dust particles and other parameters in the clean room in real time. Once an abnormal situation occurs, it can promptly alarm and take corresponding measures to ensure the stability of the clean room environment.

3)Large PCB Circuit Board Enterprise
â‘  Features
♦ Large-scale PCB Circuit Board cleanroom cluster: It is necessary to build a large-scale, multi-floor cleanroom cluster to meet the large-scale, multi-variety PCB production needs. The layout and logistics planning of the cleanroom are very complex, and it is necessary to consider the collaborative operation and material flow efficiency between different production lines.
♦ Ultra-high cleanliness requirements: For high-end PCB products, such as HDI boards, IC substrates, etc., the production process has extremely high requirements for cleanliness, usually requiring a Class 100 or even Class 10 clean environment, which places extremely high demands on the design, construction, and operation management of the cleanroom.
♦ Advanced automated production: A large number of automated production equipment and robots are used, which has stricter requirements on the environmental control and equipment matching of the cleanroom, and it is necessary to ensure the stable operation of the equipment and high-precision production.
♦ Strict environmental protection and energy-saving requirements: Due to the large scale of production, high energy consumption and pollutant emissions, it is necessary to fully consider environmental protection and energy-saving factors in the design and operation of clean rooms, reduce energy consumption and reduce pollutant emissions.
â‘¡ Solution
♦ Overall planning and optimized layout: Invite a professional design team to carry out overall planning, adopt advanced logistics systems and automated transmission equipment, optimize the layout of the cleanroom, achieve rapid and efficient flow of materials, and improve production efficiency.
♦ Customized ultra-high efficiency filtration system: It adopts customized ultra-high efficiency filtration system, equipped with multi-stage high efficiency filters and ultra-high efficiency filters, and adopts a combination of fresh air or circulating air to ensure that the air quality in the cleanroom meets the ultra-high cleanliness requirements.
♦ Advanced environmental control system: Install advanced environmental control system, including high-precision temperature and humidity control, pressure difference control, airflow organization design, etc., and adopt intelligent control system to achieve precise control of cleanroom environment.
♦ Energy-saving and environmental protection measures: Use energy-saving air-conditioning equipment, lighting systems and ventilation equipment, optimize system operation mode, and reduce energy consumption. At the same time, equip with complete waste gas treatment, wastewater treatment and solid waste treatment facilities to ensure that pollutants are discharged in compliance with standards.