The level of the thermal design power adapter _

The level of the power adapter thermal design 2020-813 08 - 03 14:12:36 so-called thermal design is the electronic equipment heat input to a minimum, and increase the cooling effect, the electronic equipment inside the harmful heat discharge to the external environment of electronic equipment, obtain the appropriate operating temperature, so that they don't exceed the limits set by the reliability, to ensure reliable, safe work. The thermal design of electronic equipment can be divided into three levels. （ 1) Electronic equipment chassis, machine box, square cavity heat system level design, the system level ( 系统) Thermal design. （ 2) Electronic modules, radiator, PCB levels of thermal design, namely the encapsulation level ( 包) Thermal design. （ 3) Component level of thermal design, namely the component level ( 组件) Thermal design. System level design research electronic equipment, the influence of the temperature of the environment temperature is one of the important boundary conditions of heat system level design. System-level thermal design is to take measures to control the environment temperature, make the electronic equipment working under the environment of the suitable temperature. System level manufacturers face the biggest problem is to develop a high cooling efficiency of chassis, machine box, square cavity, so that the heat can be imported to the environment quickly. Each kind of electronic equipment design considerations are different, and the need to clearly understand electronic equipment performance and the size limit. For example, between the metal and PCB pads must be reliable and efficient connections. Usually, heat through thermal pad on the PCB hole to another layer of copper block, after heat through heat conduction into the shell or external radiator. When a shell need to remove a large amount of heat, need an external radiator, external radiator expanded the heat transfer surface, easy to heat into the air. Radiator commonly used material is aluminium or copper. For the convective heat transfer between the radiator and air, so it is necessary to optimize the geometric shape radiator. Optimization design must consider the radiator air flow around the situation, and the area of the air flow is under the influence of the radiator, the radiator optimization design challenge. The radiator's performance depends on the material, the number of fin, the fin thickness and substrate thickness parameters. Copper material with high thermal conductivity, but under the same volume of aluminum lighter, at the same time, the price is cheaper. In some PCB, for example, by using some of the substrate to enhance heat transfer capability, these substrates using ceramic or covered with copper, aluminum, or other material. Encapsulation level thermal design development is relatively mature in foreign countries, the electronic components packaging professional. Encapsulation level circuit design, structural design of thermal design and equipment are closely related. Choose PCB base material properly is an important content of encapsulation level thermal design. Categories and characteristics of copper-clad laminate is PCB design and manufacturing personnel concerned projects, in addition to the general requirements of strength, insulation and dielectric coefficient thereof, the thermal properties of the copper clad with special requirements. Copper clad thermal performance, there are two aspects of content. （ 1) Copper clad and heat-resistant properties. Epoxy glass cloth laminated sheet copper-clad has excellent electric properties and chemical stability, working temperature was minus 230℃～260℃。 Polyimide copper-clad laminate, in addition to the above excellent properties, also has the dielectric coefficient, the characteristics of signal transmission delay is small. （ 2) The performance of thermal conductivity of copper clad. Use high temperature resistant, high coefficient of thermal conductivity of materials as a material for PCB. In the same condition, the epoxy glass cloth laminate graphics conductor temperature of 40 ℃, and the metal core PCB graphics conductor temperature less than 20 ℃, and metal core PCB has been widely used in electronic equipment. Electronic equipment parts are made up of different materials of components, such as silicon, silicon oxide insulating film, aluminum interconnect, metal lead frame and plastic packages, etc. The material thermal expansion coefficient of each are not identical, once encountered the temperature change, can produce compression on the boundary of different materials or tensile stress, thus produced thermal mismatch stress, thermal stress for short. Material thermal properties do not match is the cause of thermal stress, thermal stress and temperature change is the external cause.