In the era of modern industry and high technology, DC-DC Power module The higher the reliability, but AC-DC Power conversion DC-DC Power conversion has gradually become a modular or integrated chip industry, as well as an important part of various electronic equipment and industrial automatic control equipment, AC-DC Power module and DC-DC The quality and reliability of power module also affect the reliability, failure rate and repair rate of the whole equipment to a great extent.
The factors that affect the design and reliability of the power supply module and its production process are all concerned by the manufacturer. In fact, the reliability of the power module should not only ensure the optimization of various performance indicators, but also ensure that the production environment of the power module is clean and orderly, with good electrostatic protection measures, and appropriate temperature and humidity. Only under such conditions can the power supply module be truly regarded as a power supply product with high reliability. With the continuous progress of society, electronic equipment plays a more and more important role in industrial production, transportation, communication and other fields. The reliability of electronic equipment also determines the effective operation of various economic activities to a certain extent. Although the cost of power module in electronic equipment is very low, it can be called the "heart" of electronic equipment, and the failure of power module is direct May lead to the paralysis of electronic equipment, resulting in irreparable losses.
1、 In the process of manufacturing and assembling, the static electricity device and the charged device may be caused by the static electricity and the electric discharge of the device. Modern integrated circuits are mostly used MOS Circuit, and most of the power modules are also used MOS Tube and integrated circuit chip. In the production of power supply module, if we do not pay attention to electrostatic protection, it will often lead to high failure rate of components. Even if the product has passed the test, it is possible that in the process of production and manufacturing, the static electricity will affect the quality of the product MOS Tube and IC chip cause slight damage, which affects the life and reliability of power module. Introduction of electrostatic protection system in production environment ( Anti static grounding of human body, anti-static grounding of floor and anti-static grounding of operating devices and instruments are adopted ) After that, we can effectively avoid MOS Tube and IC chip damage. Anti static damage of electronic components is a complex system engineering, which runs through the whole process of system or equipment development and production. From the purchase of components, packaging, transportation, inventory, installation, commissioning, testing to user use, the whole process, all aspects, all staff should follow a series of relevant measures to prevent electrostatic loss. Protection is a systematic project, which requires the investment of equipment, personnel and effective management and system. Thus, the quality of an electrostatic protection system directly reflects the quality management level of an enterprise, and it is a demonstration of the strength of an enterprise.
2、 Humidity: moisture can seep into porous materials, resulting in leakage path between conductors and producing oxygen. Moisture absorption of parts reduces insulation resistance and reduces isolation and withstand voltage capacity. However, excessive drying can also make some materials brittle, rough surface, and even produce static electricity. Therefore, the production environment will also have a certain impact on the reliability of the power supply. Most power supply modules are produced by welding components into small pieces PCB plate ( pcb ) On, and then put the small pieces PCB The board is encased in the shell with resin. In the production process, if the production environment humidity is high, especially in the rainy season in the south, the moisture in the air will condense PCB On the board and components, even if the bubbles are removed by the vacuum defoaming process when resin is used for potting, the bubbles can not be removed PCB Moisture removal from boards and components. When the power supply module works at high ambient temperature, PCB The moisture on the board and components will vaporize and expand, resulting in cracks in the power module, breaking the internal transformer wire, or introducing external moisture, which will corrode the internal components of the power module or cause short circuit in the internal circuit of the module. In the case of high isolation voltage requirements, PCB The moisture on the board and components will also reduce the isolation ability of the power module, and even cause the first stage breakdown, resulting in serious consequences. Low humidity will also cause too much dust floating in the air, which will affect the quality of power module. Low humidity will also generate electrostatic charge due to personnel walking. Even if it is protected by electrostatic protection system, it may cause static damage or soft breakdown of components, resulting in the same consequences as described above. The introduction of air conditioning system and dehumidification system in the production environment can keep the humidity of production environment at a proper level, and avoid adverse impact on the reliability of power supply module due to moisture condensation or excessive drying of air. The influence of humidity on the product. The moisture in the air is immersed in the resin. In the early stage of heating, a small amount of water vapor pressure causes the delamination of the resin interface. With the increase of the welding temperature, the pressure of water vapor will expand the resin, and the water vapor will be discharged through the seal cracks, thus creating a bad appearance of the product.
3、 Temperature: the temperature of the production environment also needs to be strictly controlled. High temperature and low temperature have different effects on components.
three point one High temperature
high temperature environment will change the resistance, inductance, capacitance, electric power series and other electrical performance parameters in the power supply, which will make the insulator soft and cause insulation failure; the active components may cause structure failure due to expansion and sticking, blistering on the coating surface, acceleration of oxidation and other chemical reactions, reduction of lubricant viscosity and evaporation and loss of lubricity due to physical expansion The wear of moving parts increases and the structural strength decreases.
three point two Low temperature
low temperature environment will make the plastic and rubber of power supply lose flexibility and become brittle, ice will appear when there is moisture, lubricant will become gum and become sticky and lose lubricity; coating surface cracking; structure failure due to physical shrinkage, change of electrical and mechanical functions, etc.
three point three Temperature control
power module, especially small size 1W 、 2W Power supply module, usually using inner diameter less than 5mm This kind of transformer can only be produced by hand. When the production temperature is high, the palms of the production staff will sweat. When the transformer is wound, the sweat on their hands will stay on the transformer. The moisture and salt in the transformer will cause damage to the paint skin of the transformer. Reducing the insulation capacity of the transformer will have a potential impact on the reliability of the power module. Install air conditioning temperature control system in the production workshop to ensure that the workshop temperature is maintained at twenty-six In order to make the production staff have a cool and comfortable environment, we can produce reliable power module products.
4、 Dust: more dust will scratch the power supply, wear the surface of the finish machining, resulting in air hole blockage, lubricant pollution, insulation pollution, corona path, so as to reduce the electrical performance. If the production environment is not clean, the dust floating in the air falls PCB On the board, false soldering and false soldering of components will be greatly increased, which will not only affect the production qualification rate of products, but also affect the reliability and life of products. pay attention to the cleaning of production environment and do a good job 5S Management is a guarantee to produce qualified and reliable products. The dust and dust in the north is more severe than that in the south, so more attention should be paid to the control. Air filtration, sealing and smoke exhaust system can be used to solve the problem.
5、 Storage and storage: improper storage and storage is another important reason for reliability reduction or failure of components, which must be paid attention to and taken corresponding measures. If the temperature and humidity of the warehouse should be controlled within the specified range, moisture-proof box should be used, and attention should be paid to moisture-proof and anti-static, and harmful gases should not exist, and regular re inspection should be carried out. Containers for storing devices shall be made of materials that are not easy to carry static electricity and cause chemical reaction of components. Sensitive components shall be inspected regularly. Electronic raw materials should also be handled with care. Ceramic capacitors and magnetic materials are easy to fall and crack, especially when using and handling.
To sum up, the management of the production environment is an important guarantee for the reliability of the module power supply. These management needs the input of human and material resources of the enterprise, and various management measures need to be implemented, rather than just written on paper, discussed in the meeting and pasted on the wall. The management level of the production environment embodies the production capacity and strength of a module power supply manufacturing enterprise. Only the enterprise that relies on quality to survive is a real enterprise with a long history. As the energy source of electronic equipment, the module power supply has become a very important and even the most critical component in the electronic system. The reliability of power supply module has attracted more and more attention of electronic equipment manufacturers, which also puts forward higher requirements for power module manufacturers. The evaluation of production environment and production management is also listed It is an important part of supplier evaluation.