With the development of science and technology and the increasingly complex application environment, electronic equipment is moving toward the direction of precision automation scale and miniaturization. Quality 1 also requires advanced. Rely on sexual fitness and safety. Therefore, the importance of thermal design in this type of equipment is becoming more and more prominent. The correctness of thermal design directly affects the stability and reliability of electronic equipment.
There are many electronic components in electronic equipment, and the materials used in the manufacture of fe sub-devices have a certain temperature limit. When exceeding this extreme thing, Quanpu will change ten times, and the device can not play its intended role. The device may also have a failure rate at the rated temperature due to the continuous working time for too long. The data shows that the electronic device plays an important role.
It can be known from experience that devices or circuits are prone to failure under high temperature conditions. The most temperature-sensitive devices are heavily used semiconductor devices and microcircuits. The failure rate of semiconductor devices increases exponentially with increasing temperature. Among them, performance parameters such as withstand voltage leakage current amplification factor allowable power are temperature coefficients In general, the performance parameters of other devices are also affected by temperature.
Thermal design is to consider the effect of temperature on the equipment. The key is to reduce the impact of temperature changes on the performance of the design bath through the selection of circuit design and 5 configurations of the device, so that the equipment can work in a wider temperature range. In thermal design, generally, according to the specific situation, choose a more suitable way to transfer heat to achieve the purpose of cooling the components, and at the same time, the cooling method should be considered according to the power density of the heating element and the required thermal resistance.
Radiant heat dissipation is emitted from objects in a straight line to talk about the thermal design of electronic equipment. Radiation heat dissipation measures include heat dissipation coating on the surface of the heating body to increase the temperature difference between the radiation and the surrounding environment; increase the surface area of ​​the radiator.
Forced air cooling, natural cooling can not solve the problem, you need to use forced air cooling.
The cold plate cooling belt, the channel of the heater, and the performance of forcing the air flow through the device wall.
The control of the operating temperature of the element is connected to the factors that affect the performance and failure rate of the components. The effect of temperature on the resistance is that the resistance value will change with the change of temperature, allowing the dissipated power to decrease, the life to be reduced, and the thermal noise to increase. The effect on the capacitor is to change the capacitance and dielectric loss angle power factor and other parameters, reduce the life, change the life of the sensor, change the life, and double the life. For semiconductor devices, the temperature is too high to change the electrical performance. Cause thermal breakdown, the junction temperature of the integrated circuit, every 10 increase, the failure rate increases about. Therefore, the thermal design of the components must ensure that the maximum temperature of the components is lower than its allowable temperature.
The natural heat dissipation resistance of the components is dissipated by the conduction of the lead wires and the convection radiation of itself.
The electronic world is therefore as short as possible when assembling the resistance. The installation position should be such that the surface with large heat generation is perpendicular to the center distance between the convection gas sub-tubes and should not be less than 1.5 times the tube diameter. Tunzi tube is installed with vertical installation of transformer, which requires iron core and bracket. The fixing surface of the bracket hook should be in good contact, and the outside should be matte, 19 millimeters. For big work, the body tube should be used for meters, and the heat radiator should be used for heat dissipation. , Component installation and layout of components. Arrangement and arrangement is an important part of thermal design, when carrying out this work. The location of the artifacts should be reasonably arranged according to the heating conditions of the heat sources in the equipment. Prevent the accumulation of heat of components and the thermal influence between components, make the components work within the allowable working temperature range 7 Principles of device installation and layout The location of heat-generating components should be exhausted and dispersed, in order to maximize the mouth of the components Hindered. Erqi Zhong should keep the temperature sensitive device in the low temperature 1 domain. In the installation of children's devices, the thermal design is to reduce the thermal resistance between the housing and the radiator. It is to minimize the thermal resistance. The meter uses short passages to increase the installation area and uses materials with high thermal conductivity. When using the contact interface, use the following measures to minimize the contact thermal resistance and increase the contact surface; use soft contact materials to ensure a smooth contact surface; tighten all screws to increase the contact pressure.
The main task of the thermal design of the printed board is to effectively guide the heat of the printed board to the external radiator and the atmosphere. When designing the printed line, ensure the current carrying capacity of the printed line. The width of the printed line must be suitable. Because of the conduction of current, the temperature rise and voltage drop cannot be exceeded, and the spacing between adjacent wires must also meet the electrical insulation requirements. The heat dissipation of the printed board is mainly to try to install the printed wire and the printed wire with a large thickness on the printed board, in order to facilitate the heat conduction of the printed wire and natural convection heat dissipation. Thermal resistance, enhance the thermal conductivity of the component lead legs to the printed wire, and strong conductivity. When the heat density of components exceeds 0.612. Measures such as heat sinks and heat sinks should be used to increase conduction heat dissipation.
Thermal design of the chassis The task of the thermal design of the chassis is to fully ensure that the equipment can withstand the mechanical pressure of the external environment, and the heat transfer and radiation can maximize the heat generated by the equipment. According to the situation of the equipment, you should first set a model that is similar to the actual equipment, and within 1 to 1 of the error allowed for the set response, and then pay for trial production! The device performs temperature measurement and compares it with the calculation result. Adopting and modifying measures to make the thermal design of the chassis can achieve the predetermined effect. Specifically, the sealed chassis can be used, the windward chassis or forced air cooling.
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