Poor compressed air quality has a huge impact on the SMT industry

As the second largest power source after electricity, air has been recognized by the business community. When considering the configuration of SMT production line, equipment selection, and subsequent installation and use, many users often only pay attention to the main equipment (for example: sticker The selection of installed machines, solder paste printers, wave soldering machines, etc.), while ignoring the reasonable selection and investment of aerodynamics, has left long-term hidden dangers to the production line. The compressed air used in the SMT production line not only requires stable and sufficient air pressure and flow, but also the compressed air used must be dry and clean.

The atmosphere contains impurities such as corrosive gases, water vapor, and hydrocarbons. There are approximately 140 million solid particles per cubic meter of air. More than 80% of these impurities have a particle diameter of less than 2μm. It will easily enter the compressed air system through the air compressor and the muffler filter. After passing through a simple filter, the air containing various impurities enters the air compressor for compression. Due to the high temperature and oxidation generated when the gas is compressed, the quality of the compressor lubricating oil is reduced, and it is strongly acidic. These solid particles When compressed air, oil and water vapor enter the compressed air pipe network system together, it will cause the pipe network and equipment to rust and increase the maintenance cost of the system equipment.

   Poor quality of compressed air will bring the following serious hazards to SMT production:

  1. Corrosion of solenoid valves, cylinders and other pneumatic components will cause blockage of the air circuit, resulting in uncoordinated actions of the pneumatic mechanism of the machine and damage to the machine. Equipment such as solder paste printers and multi-function placement machines will often shut down for repairs due to excessive oil, water and other impurities in the gas circuit system. These hazards are particularly serious in high temperature, humidity and heat;

  2. During wave soldering, the use of dirty compressed air brings oil, water and other impurities to the flux, printed boards, and component leads, resulting in poor soldering. In the case of chip ceramic capacitors, the soldering tin often causes the component body to form a penetrating short circuit. The reason is mostly because the flux is contaminated by dirty compressed air. For the soldering of printed boards with high component density or too dense component leads, it is necessary to prevent the contamination of the flux by dirty compressed air, and the chances of short-circuit and false soldering during soldering will be greatly increased.

   Therefore, effectively removing water, oil, and dust particles in compressed air, improving the quality of compressed air, and meeting the technological requirements of equipment will directly reduce the production cost of the enterprise, improve production efficiency and economic benefits. SMT production equipment belongs to precision machinery equipment. The compressed air provided should be clean and dry, and the quality of the gas must meet the ISO8573/11-3-1 standard in process.

   The oil in the compressed air mainly comes from the mechanical movement process inside the air compressor, and the lubricating oil necessary for the air compressor to perform work. Oil-free air compressors are undoubtedly the best choice, but due to the extremely high price of oil-free air compressors, most users can only choose ordinary screw compressors. Therefore, it is inevitable to mix part of oil in compressed air. Dust particles, oil and moisture in the air can be removed with high efficiency filters and dryers.

   The solid particles in compressed air are mainly removed by precision filters. There are three principles:

   One is to "directly capture" larger and heavier particles that move in a straight line;

   The second is "inertial collision", which is used to capture particles that are smaller, lighter, and change direction slightly with the airflow;

   The third is "Brownian motion". As for very small particles, once they collide with fibers, they will be firmly attracted by van der Waals force, electrostatic attraction and vacuum attraction.

   The following principles should be followed when selecting models:

   (1) According to the compressed air source, the use requirements of the production equipment (for example: equipment requirements for compressed air quality, gas pressure, flow, etc.), select the filter level;

   (2) When filters of different levels are used in combination, they should be configured in order from low level to high level, and can not skip arbitrarily;

  3) The pressure drop between the inlet and outlet of the filter should be as small as possible. The water in the compressed air is mainly filtered through high-efficiency gas-water separators, refrigerated dryers, and adsorption dryers. The filter can also remove part of the liquid water. The refrigeration dryer mainly cools high-temperature compressed air to separate part of the liquid water, but it cannot completely solve the problem of water in the compressed air.

  Adsorption dryer mainly absorbs water molecules in compressed air on its surface through molecular sieve, and discharges the water through a pressure swing method, thereby completely removing the water in the compressed air. The oil in the compressed air is mainly filtered by a filter. If the oil content is high, it is best to configure an activated carbon filter. When choosing a filter, you should not only consider the price factor, but also pay attention to the filter quality and effect.

   Precautions for product selection

  Because it is widely used in our lives and production, when making a purchase, you must not only pay attention to the price or the brand, and not to be cheap. The most important thing should be:

   1. Quality problems Because the filter material and the quality of the filter element of the air filter are very important;

   2. Safety assurance Whether the product has passed the safety certification of relevant national institutions and departments, and whether there is a product inspection certificate;

  3. The reputation and service of the production enterprise Whether the production enterprise abides by its promises, has follow-up services and quality assurance capabilities;

   Fourth, the technical strength of the enterprise The enterprise must have the technical ability and production capacity to continuously update its products, and to ensure the stability of product quality;

   Otherwise, once the product has a problem, it will affect the entire equipment and production status, causing serious consequences such as product quality, equipment damage, and production accidents.