Design and test of radiator for vehicle electronic control equipment (50w)
Abstract: In the design of automotive electronic control equipment, electronic devices are the key components in the equipment. The thermal design of electronic devices directly affects the reliability of the entire system. This paper introduces the design of a 50w heat sink in a vehicle electronic control device, and introduces the heat conduction analysis and heat sink design of the heat sink from the perspective of use. The experimental data and simulation analysis results are compared and analyzed to verify the design. Effectiveness.
0 Preface
In recent years, electronic technology has been widely used and rapidly developed in automobiles, especially new energy vehicles. At the same time, people's increasing demand for automotive functions has made the integration of automotive electrical equipment more and more high, and the functions of automotive electrical equipment have been integrated. High Power. Miniaturization is the future direction of automotive electronics.
With the thin and light electronic products. High-performance. The development of IC devices is highly integrated. The heat generated by electronic devices causes the internal temperature to rise rapidly. If the heat is not dissipated in time, the device will continue to heat up, and the device will fail due to overheating. The reliability of the electronic device will be Dropped, and even caused the chip to be damaged by instant breakdown. Therefore, the requirements for the heat dissipation capability of electronic products have been changed, and the heat dissipation design technology of electronic products has been continuously improved.
1 Heat generation and heat transfer analysis of the radiator
As a key component of automotive electronic control equipment systems, electronic devices must not only ensure the performance of automotive electronic control equipment to meet the requirements of the entire vehicle, but also ensure that the automotive electronic control equipment has sufficient safety and reliability. For the automotive electronic control equipment provided in the prior art, in order to achieve higher energy density and power density, the power drive unit module is mostly formed by series or parallel connection between multiple power single tubes, so that the output voltage or output of the power module The current will be greatly increased to meet the driving requirements of the car. In the course of work, the power-driven PCB assembly of automotive electrical equipment is the most important source of heat generation.
Analysis of heat conduction process: The surface of the power device is mounted on the circuit layer, and the heat generated by the device is conducted to the metal base layer through the insulating layer, and then extended from the metal substrate to the outside of the module to exchange heat with the external environment to achieve heat dissipation to the device, such as Figure l shows.
Which metal is used for the metal substrate depends mainly on the coefficient of thermal expansion. Thermal conductivity. strength. hardness. weight. Surface state and cost. The metal substrate is basically made of an aluminum plate.
The aluminum radiator is extruded by using an aluminum alloy material. In order to increase the heat dissipation area per unit volume, the formed heat sink has corrugated teeth, and this structure enhances the heat dissipation capability of the heat sink. The heat conduction internal resistance between the power module and the heat sink is effectively reduced, the heat on the power module can be quickly exported, and the power module can be cooled in time; in order to supplement the defects in the machining, a layer of 100 is coated on the surface of the heat sink. Um's thermal paste fills the small space between the heat sink and the power module. This requires surface machining of the mounting surface of the power device during processing and ensures a certain degree of flatness. Roughness. In short, the structural design of the radiator. The surface treatment and the coating of the thermal conductive materials create a good external heat dissipation environment for the power module, which can ensure the reliable and stable operation of the power module and prolong the working life of the power module.
2 radiator design
The heat sink dissipates heat by convection and radiation, where convection heat dissipation dominates. Refer to the fin shape (as shown in Figure 2 and Table 1) design data, and design the main dimensions as follows:
(1) According to the installation position of the controller, the short air duct wind resistance is small. Increase the heat dissipation surface area as much as possible while selecting the fins parallel to the short side of the heat sink base.
(2) The spacing between the fins. Since the air flow rate of the BSG controller installation position varies greatly with different working conditions, and sometimes works under the condition that the air flow rate is close to 0, in order to ensure that the heat dissipation base plate can effectively dissipate heat at a lower wind speed, sufficient fins are required. Pitch. However, the excessive fin spacing will reduce the number of fins and reduce the heat sink area, thereby reducing the heat dissipation capability of the heat sink. On the wall surface of the heat sink, natural convection will occur due to the temperature change of the surface, resulting in laminar air flow on the wall surface. The thickness of the air layer is about 2 mm, and the fin spacing should be more than 4 mm to ensure smooth natural convection. At this time, the pitch of the heat dissipation base plate is about 8 mm.
(3) Fin thickness. When the controller is in the starting state, the transient current of the power tube is large, so the controller has a large transient thermal shock, and the fins of the heat dissipation substrate are required to have sufficient thickness. When the shape of the fin is fixed, the balance of thickness and height becomes important, especially when the fin is too thick and the height is insufficient, which causes difficulty in heat transfer at the front end, so that the heat sink cannot increase efficiency even if the volume is increased. When the heat sink is too thin and the height is shortened, the surface area is increased but the volume of the heat sink is reduced to cause a decrease in heat dissipation capability. According to the reference value, the fin thickness is designed to be 4mm and the draft angle is 3
(4) Since the power tube is not completely evenly distributed on the heat dissipation board of the controller, in order to ensure effective heat dissipation, the heat dissipation fins are distributed as much as possible in the place where the power tubes are concentrated.
(5) According to the basic formula of convection heat transfer, the heat dissipation surface area of ​​the heat dissipation substrate can be increased as much as possible, and the heat dissipation capability of the heat dissipation substrate can be effectively increased, and the heat dissipation surface area of ​​the heat dissipation substrate can be effectively increased by adding corrugated teeth on the surface of the fin. However, considering the influence of heat conduction and wind resistance, the depth of the corrugated teeth is preferably not more than 0.5 mm.
Considering the above situation and combining the overall shape of the PCB driver board and controller, the design of the heat sink board is shown in Figure 3.
3 Radiator thermal simulation and test analysis
3.1 Simulation results
For the designed heat sink, CAE modeling simulation is performed as follows:
According to the total heat power consumption of 80W, the heat power is distributed evenly on the heat sink for simulation. Each time the heat monitoring point is simulated: 2 (PCB board. One center of the heat sink), when the temperature of the center of the heat sink changes When 30min is not more than 1°C, the heat sink is considered to be in thermal equilibrium and the simulation is over. The simulation results are shown in Table 2:
3.2 Test results
Through experiments, the temperature rise of the center temperature of the heat sink is about 73 ° C. 54 ° C. 27 ° C under the power of 80 W, 55 W, 30 W, respectively, the temperature rise of the PCB board center temperature is about 72 ° C. 55 ° C. 37 ° C as shown in Figure 4.
4 Conclusion
By comparing the temperature rise data of the simulation and the test experiment, their temperature rises are not much different, and the temperature rise does not exceed 90 °C in the absence of wind. At the same time, consider the installation location of the controller. Ambient temperature. Working condition factors, etc., it is known that the temperature of the radiator center reaches about 110 °C, which is a normal situation. At this time, the power tube casing temperature is at least 120 ° C, and its working limit temperature is 160 ° C (the drain current will be significantly reduced). Small) There is still a certain distance, so the heat sink design is reasonable.
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