A Systematic Design and Test About the High Uniformity Thermal Plate

With the rapid iteration and performance of the chip and electronic component technology, critical components' power has significantly increased. Generally speaking, a source of power devices with ample heat dissipation power, such as an RF transistor and MMIC chip, has a much smaller heat dissipation area than the heat dissipation substrate heat dissipation area. This temperature control shows the characteristics of high thermal flow density. Regarding this issue, conventional temperature control methods are challenging to apply.

The essence of the problem of high thermal density is that heat continues to be generated in a small area. The heat discharge rate of conventional temperature control methods in small spaces is much lower than the heat source heating rate. The accumulation of heat in small areas has led to a sharp increase in temperature in the room in a short time. The average  technology is a type of calorie scattered technology developed based on the development of the Vapor Chamber. It can rapidly diffuse high-density heat flow and effectively reduce local thermal density. The structure and working principle of the average Thermal Plate are shown in Figure 1. Its design mainly includes structural shells, a capillary system, and a working medium.

 

The research on the average Thermal Plate mainly concentrates on the middle-temperature scale of low saturated air pressure, such as water, acetone, and ethanol. Due to the limitation of working temperature range, medium thermal transmission efficiency, shell and medium compatibility, non -condensed gas sensitivity, these average Thermal Plates are challenging to apply in the field of high thermal flow density temperature control.

This article uses an aluminum combination based on the vacuum cavity principle to develop a type of temperature-resistant plate that can be applied to the space environment, which provides a reliable and efficient passive temperature control solution for the high heat flow density temperature control problem.

Research and development of high-voltage duration of high pressure

The conventional average Thermal Plate uses a low-saturated pneumatic medium. The edge of a cavity generally supports the internal cavity with a small number of support pillars. The overall size of the conventional average Thermal Plate (generally not greater than 100 mm × 100 mm) and the internal medium flow path is short. It is primarily a sintering hair core as a suction fluid core. Compared to low-pressure media, ammonia's saturated pressure is much higher. At 60 ° C, the saturation pressure of ammonia is more than 130 times the water saturation pressure. Therefore, the design of the average temperature of the plan must have good pressure. Considering the model application, the average temperature board developed in this article is 200 mm × 200 mm.

Based on the workbench platform, this article uses finite element analysis technology to simulate the models of different structures and parameters. The analysis uses a non -structural grid discrete model with good adaptability. The multi-point support structure is overall, and the maximum variable volume after pressure is controlled within 0.1 mm. The simulation analyzes the effects of different support pillar shapes, sizes, support pillar distribution, and weakening of slot lanes. The design aims to meet the number of support pillars, the volume of the supporting post, and the overall weight and thickness while satisfying indicators such as structural strength, thermal diffusion ability, and deformation. The analysis results found that the maximum stress of the circular support column was significantly reduced compared to the square support pillar. The size of the four-week bezel has a more significant impact on the maximum stress and strain, and the thickness of the frame must be about 1.5 times the diameter of the support pillar. The slot can increase the local pressure, and the thickness of the substrate needs to be adjusted according to the slot's shape, size, and density.

While the average Thermal Plate structure meets the requirements of mechanical performance, it also needs to meet the thermal performance requirements. This article analyzes the average Thermal Plate temperature distribution and thermal resistance based on the FLOEFD platform and empirical formula, as shown in Figure 2. According to the analysis, the thermal resistance (R0) of the component, the thermal resistance (R1) between the element and the average Thermal Plate, the shell thermal heat resistance (R2), and the internal temperature of the middle-Thermal Plate and the heat resistance (R3) are heat Self -heating elements spread to the primary thermal resistance in the process of intermediate Thermal Plate. R0 and R1 are the primary thermal resistance to the temperature of elevated components. R2 and R3 are the immediate thermal resistance that affects the average temperature of the intermediate Thermal Plate.    

 

2. Performance test of high-pressure average Thermal Plate

The performance test system of the average Thermal Plate is mainly composed of a constant temperature water tank, aluminum ammonia thermal tube, high-temperature heating tablets, high-power power supply, data collectors, etc. The size of the average Thermal Plate is 200 mm × 200 mm, and the pressure resistance capacity is better than 5.6 mPa. The high-density heat flow generated by high-temperature heating sheets has spread through the general Thermal Plate developed by a conventional density. Then transmit it from the traditional ammonia of aluminum thermal tube to the cold board. This process reflects the use of passive temperature control methods to solve the high-density thermoscopic control problem. To avoid burning and destroying heating elements, high-temperature heating films simulate high-power heating elements, and cold plate simulation space heats sinking. The filling interface material between high-temperature heating tablets, average-Thermal Plates, aluminum ammonia heat pipes, and cold dishes reduces contact thermal resistance. The specifications of aluminum ammonia are rectangular 37.4 × 19.1 dual-hole thermal tubes. The maximum heat transfer capacity of theory reaches 1100 W.

The thermal source is placed at the corner of the average Thermal Plate during the test. Theoretically, there is the most unfavorable position of the average Thermal Plate heat transfer capacity. The thermal source should have a better average temperature when it is in other areas. The distribution of the measurement point on the surface of the test piece is shown in Figure 3. The upper and lower sides of the average Thermal Plate test parts are arranged with temperature measurement points. The test process uses the method of gradually improving heating power to test the thermal diffusion performance of the average test parts under different thermal densities. The heating power and the surface temperature difference between the different thermal densities and the surface Thermal Plate are shown in the Table below.

 

 

As heating power and thermal density increase, the surface temperature, thermal source temperature, and the surface temperature difference of the average Thermal Plate increase. When the thermal density is 34.3 W/CM2, the heating power is 107.7 W, and the maximum temperature difference between the thermal test parts is only 0.25 ° C. When the heat flow density exceeds 34.3 W/CM2 to the maximum thermal density provided by the test thermal source of this test, the average Thermal Plate can maintain a suitable average temperature as a whole. The temperature difference does not exceed 1 ° C, showing a solid heat diffusion effect. Limited by heating source heating capacity, the extreme thermal diffusion capacity developed by the average temperature board testing is unable to measure. Regarding the extreme thermal density of crucial equipment and components of satellite models, the thermal density range of this test should be able to cover the thermal density range of most satellite models and features. The maximum tolerance heat flow density of conventional aluminum ammonia thermal pipes is about 3 W/CM2, so the development of the average Thermal Plate tolerance to the effect of the intermediate Thermal Plate has more than 20 times that of the conventional thermal tube tolerance heat flow density.

During the test process, the high-density thermal heat generated by high-temperature heating sheets passed through the average Thermal Plate and aluminum ammonia thermal tube to the cold plate, realizing the problem of using passive temperature control methods to solve the problem of high thermal density temperature control.

The thermal response test was carried out on the average Thermal Plate to test the response of the heat source and the opening situation of each measuring point of the intermediate Thermal Plate. The test is carried out in the test system, and the heat source and measuring point arrangement is the same as the thermal density test. The testing process can simulate the heat source by turning it on, turning the power supply, and continuously adjusting the heat source power. The range of thermal flow density is (0.5 ～ 45) W/CM2.

The surface temperature of the average Thermal Plate and the surface temperature of the heating sheet has almost synchronized thermal response effects with the power of the heat source. The response of the temperature of the thermostat's thermal source on the thermostat's surface temperature is not more than 8 S. The internal medium of the board has a breakneck heat transfer speed, so it shows high -a efficiency thermal diffusion function.

During the heat response process, the surface temperature difference between the average Thermal Plate is kept within 1 ° C throughout the test. It can be seen that the developed intermediate Thermal Plate still has a suitable average temperature in the process of changing conditions or transient heat transfer.

3. Comparative performance

I am summarizing the engineering sample machines and similar products at home and abroad from work quality, shell materials, space applicability, and average temperature. The developed average Thermal Plate engineering sample machine is significantly better than similar products at home and abroad regarding spatial applicability, the density of resistance heat flow, average temperature, volume thermal conductivity, and temperature use range.

4. Summarize

1) The development parts developed by the development of the average Thermal Plate have a strong heat diffusion performance. When the thermal density is 34.3 W/CM2 and the heating power is 107.7 W, the average temperature difference between the temperature board test parts is only 0.25 ° C.

2) The temperature difference is less than 0.7 ° C when the thermal density rises to 57.7 W/CM2.

3) The characteristics of the test parts have almost synchronized responses to the heat source power change, indicating that the test parts have an excellent thermal reaction.

4) The development of the resistance of pressure resistance is the goal of passive temperature control methods to solve the problem of high thermal density.