This part of GB/T8446 gives the principle of testing the thermal resistance and flow resistance of heat sinks, and specifies the test system requirements, test conditions and basic measurement procedures for air-cooled, self-cooled and water-cooled heat sinks. This part is applicable to the test of thermal resistance and flow resistance of cast (including extruded) heat sinks, profile heat sinks and heat pipe heat sinks for power semiconductor devices. GB/T 8446.2-2004 Heat sinks for power semiconductor devices Part 2: Test methods for thermal resistance and flow resistance GB/T8446.2-2004 Standard download decompression password: www.bzxz.net

GB/T8446 "Heat sinks for power semiconductor devices" is divided into three parts: - Part 1: Casting series;
- Part 2: Test methods for thermal resistance and flow resistance; Part 3: Insulation and fasteners.
This part is Part 2 of GB/T8446.
GB/T 8446.2-2004
This part replaces GB/T8446.2--1987 "Test methods for thermal resistance and flow resistance of heat sinks for power semiconductor devices". Compared with GB/T8446.2-1987, the main changes of this part are as follows: the structure and writing rules of the standard have changed greatly. The previous version (1987 version) was based on GB/T1.1-1981, and this version (this part) is based on GB/T1.1-2000;
- The main content has added a preface and a chapter "Scope"; - The titles "Principle" and "Measurement" of Chapter 1 and Chapter 4 of the previous version (Chapter 2 and Chapter 5 of this version) are changed to "Principle and Heating Current" and "Measurement and Calculation" respectively;
The method of providing heating current for thermal resistance test was specified as the simulation method in the previous version, and is specified as the DC method in this version (Chapter 1 of the 1987 version; Chapter 2 of this version);
In Chapter 2 of this version, the textual description and calculation of the DC method and dynamic method of heating current are added. The formula for calculating power has been changed; the approximate formula for calculating the thermal resistance of a flat plate radiator has been added (see formula (9) in 5.4 of this edition); the connection position of the rubber hose at the air inlet end of the meter for measuring the air inlet temperature, wind speed and differential pressure has been changed from 300 mm from the central section of the radiator to 300 mm from the front edge of the radiator (2.1 and Figure 1 of the 1987 edition; 3.2 and Figure 1 of this edition); there have also been major changes in literary treatment and editing, such as the wording "this standard" has been changed to "this part"; the original Chapter 1 (now Chapter 2) had no article hierarchy, but now has an article hierarchy with article numbers and titles; the original Chapters 2, 3 and 4 (now Chapters 3 to 5) had no article hierarchy, but now have titles for uniformity and eye-catchingness; the International Document Classification (UDC) number on the upper left corner of the original cover of the standard has been changed to the International Standard Classification (ICS) number.
GB/T8446 is one of the series of standards consisting of various heat sinks and heat sink selection guidelines for power semiconductor devices. This series of standards also includes:
JB/T5781 Technical conditions for profile heat sinks for power semiconductor devices-JB/T8175 Dimensions of profile heat sinks for power semiconductor devices-JB/T8757 Heat pipe heat sinks for power semiconductor devices JB/T9684 Selection guidelines for heat sinks for power semiconductor devices This part was proposed by the China Electrical Equipment Industry Association. This part is under the jurisdiction of the Xi'an Power Electronics Technology Research Institute. Drafting units of this part: Jiangyin Thyristor Accessories Co., Ltd., Wenzhou Xiangbo Power Electronics Co., Ltd., Yancheng Caiyang Electric Valve Co., Ltd., Xiangfan Instrument Components Factory, Beijing Xieli Electronic Devices Factory, Beijing Hengtaigu Technology Co., Ltd., Xi'an Power Electronics Technology Research Institute. The main drafters of this part: Xia Xianzhong, Xia Botao, Sang Chun, Liu Shuhua, Chen Zhenyun, Lu Zhengbai, Qin Xianman. This part was first published as GB/T8446.2-1987 in December 1987. 1 Scope
Heat sinks for power semiconductor devices
Part 2: Test methods for thermal resistance and flow resistance
GB/T 8446.2—2004
This part of GB/T8446 gives the principles for testing the thermal resistance and flow resistance of heat sinks, and specifies the test system requirements, test conditions and basic measurement procedures for air-cooled, self-cooled and water-cooled heat sinks. This part is applicable to the test of thermal resistance and flow resistance of cast (including extruded) heat sinks, profile heat sinks and heat pipe heat sinks for power semiconductor devices.
2 Principle and heating current
2.1 Principle
The thermal resistance of a heat sink is a measure of the ability of a heat sink to dissipate heat from the die of a semiconductor device. Its value is defined as: the ratio of the temperature difference between a specified point on the heat sink surface and a specified point on the cooling medium at thermal equilibrium to the power dissipated to produce the temperature difference between the two points, see formula (1). R. - T._T
Where:
R is the thermal resistance of the heat sink, in degrees Celsius per watt (°C/W); P is the power generated by the heating current of the test thermal resistance, in watts (W); T is the temperature of a specified point on the heat sink surface, in degrees Celsius (°C); T is the temperature of a specified point at the inlet of the cooling medium (water or air), in degrees Celsius (°C). Note: For the test of air-cooled or self-cooled heat sinks, the symbol T is usually replaced by T. (1)
The thermal resistance of a bolt-shaped heat sink with one-side heat dissipation, or the partial thermal resistance of the cathode side or anode side of a flat-plate heat sink with two-side heat dissipation, can be directly measured and calculated using formula (1). At this time, the thermal resistance of the flat-plate heat sink should be calculated by the parallel connection of its two partial thermal resistances according to formula (2). The two partial thermal resistances are calculated according to formulas (3) and (4). Rsa(k) · Re(A)
R.= Rk)+ RacA
Where:
Rsa(K)
Rsa(A)
Where:
The thermal resistance of the cathode side of the flat-plate heat sink is in degrees Celsius per watt (℃/W), and the thermal resistance of the anode side of the flat-plate heat sink is in degrees Celsius per watt (℃/W). Rsa(K):
Ts(K) - T
TsK) The surface temperature of the cathode side of the flat radiator, in degrees Celsius (℃); The heat flow on the cathode side of the flat radiator, in watts (W). Pk—
Rsa(A) =
Where:
TA)— T
The surface temperature of the anode side of the flat radiator, in degrees Celsius (℃); The heat flow on the anode side of the flat radiator, in watts (W). (2)
（4）
The flow resistance (△P) of the radiator is the pressure difference of the cooling fluid at the specified points at both ends of the radiator in the air duct or water system, in Pascals (Pa). 1
GB/T 8446.2—2004
Flow resistance is also called wind resistance in the air duct and water resistance in the water system. The heat sink resistance value is measured directly by the differential pressure gauge (see Figure 1). 2.2 Heating current wwW.bzxz.Net
The heating current methods for the heat sink thermal resistance test include DC method, dynamic method and simulation method. This standard stipulates the DC method. Other methods can also be used after the calibration effect is consistent with this method. The accuracy of the thermal resistance test mainly depends on the power P generated by the heating current and the table temperature T. The accuracy of the measurement.
The DC method is a thermal resistance test method that generates power P by applying DC current to the device, see formula (5). The DC method calculates P simply and accurately, and requires a large current DC power supply device. P= IrVr
Where:
IT---the on-state DC current as the heating current, in amperes (A); Vi---the on-state DC voltage, in volts (V). (5)
The dynamic method is a thermal resistance test method that generates power P by applying a half-sine wave current to the device, see formula (6). The dynamic method is very realistic and can be implemented using full dynamic or semi-dynamic test equipment that tests the rated current of the device. P = VToIT(AV) +f\rrI(AV)
Where:
threshold voltage of the device, in volts (V); IT (AV)
-average on-state current as heating current, in amperes (A); f——waveform factor, the waveform factor value for a sine wave conduction angle of 180° is 1.571; rT-—slope resistance of the device, in ohms (Q). Note: To reduce the influence of the conduction angle on P, it is best to use a rectifier instead of a crystal rectifier. (6)
The simulation method is a heat sink thermal resistance test method that applies current to a simulated device to generate power P. The simulated device is a "device" that encapsulates a resistor element die that satisfies Ohm's law in an actual tube shell, also known as a dummy component. The analog method for calculating power is the same as the DC method formula mentioned above. It is also simple and accurate, and the equipment investment is also small. However, the analog device manufacturing technology is difficult, especially the DC voltage of the measurement system is generally as high as tens of volts. Improper insulation of the thermocouple lead and the test system have a great impact on the test results. .3 Test system requirements and instructions
3.1 General test system
The air-cooled, self-cooled and water-cooled radiator test systems all include heating current units, thermocouple test units and thermometers for measuring the inlet air or water temperature T1).
The accuracy of the ammeter, voltmeter or wattmeter in the heating current unit should be 0.5 level. The thermocouple for measuring the radiator table temperature (T1) should be made of 0.25mm diameter copper or constantan wire hot end fusion welding, and the solder ball diameter should be less than 0.8mm. During use, the hot end of the thermocouple should be prevented from twisting and short-circuiting. In the air duct, the thermocouple should be placed at the leeward end of the radiator and covered with a sufficiently thin plastic tube. The cold end of the thermocouple should be kept at 0℃. The accuracy of the thermometer used to measure the reference point temperature (T1, or T2) should be ±0.1℃. 3.2 Air-cooled radiator test system
The test system of air-cooled radiator is shown in Figure 1. In addition to meeting the requirements of 3.1, the test system is recommended to use QDF-2 type or higher precision anemometer, and the differential pressure gauge for measuring wind resistance is recommended to use DJM9 compensated micro pressure gauge. The two rubber tubes of the differential pressure gauge are respectively connected to the metal tube on the side wall of the air duct 300mm away from the front and rear edges of the radiator under test. The inner diameter of the metal tube shall not be greater than 6mm and shall not extend into the air duct. The thermometer and anemometer (when measuring) are placed at the center of the air duct section 300mm away from the front edge of the radiator under test. 3.3 Self-cooling radiator test system
In addition to meeting the requirements of 3.1, the test system of the self-cooling radiator is mainly composed of a self-cooling environment box. The space size of the self-cooling environment box should be sufficient to keep the temperature difference at 200mm around the radiator under test no more than 2℃, and the wind speed formed by natural convection of air no more than 0.5m/s. The radiator under test should be suspended in the middle of the self-cooling environment box space, and the radiator blades should be along the natural convection direction of the upper and lower air. The location of measuring T. is 200mm directly below the center of the radiator.
3.4 ​​Water-cooled radiator test system
GB/T8446.2--2004
In addition to the heating current unit and the thermocouple test unit, the test system of the water-cooled radiator mainly consists of a thermometer for measuring the inlet water temperature (T,), a flowmeter for measuring the water flow, and a differential pressure gauge for measuring the water resistance (△P). Differential pressure gauge
Anemometer
Heating current
Thermocouple test
D=10 mm±2mm
4 Test conditions
4.1 Heating power
The test system of the air-cooled radiator
should be selected within the linear relationship between the radiator temperature rise and the heating power. 4.2 The installation force between the heat sink and the heating device
shall comply with the provisions of the relevant device product standards. 4.3 Cooling conditions of the heat sink
When testing the air-cooled heat sink, the wind speed is 6m/s, and the inlet air temperature is the actual ambient air temperature; when testing the self-cooling heat sink, the wind speed of the natural convection of the air shall not exceed 0.5m/s, and the ambient temperature at the specified point shall be the actual ambient air temperature; when testing the water-cooled heat sink, the water flow rate is 4I/min, and the inlet water specified point temperature is 35-9℃. 4.4 The location of measuring the reference point temperature
The location of measuring the ambient reference point temperature T, or T. shall comply with the relevant provisions of Chapter 3. The location of measuring the reference point temperature T. on the heat sink should be a small hole on the heat sink surface 2mm outside the diameter of the heat sink shell or the maximum diameter of the bolt-shaped shell, with a hole diameter of 0.8mm and a hole depth of 1mm. Put the thermocouple in the manhole, and use the tip of a hammer to tap the nearby metal to make the thermocouple firmly contact the radiator table, and pay attention to the insulation of the thermocouple lead. 5 Measurement and calculation
5.1 Preparation for measurement
Assemble the heating device on the radiator to be tested with the specified installation force or installation torque, install the thermocouple according to the requirements of 4.4, and place it in the wind 3
GB/T8446.2—2004
duct or water system or self-cooling environment box. Connect the heating current unit and thermocouple test unit. Put the probes of measuring instruments such as thermometers and differential pressure gauges to the specified positions. Calibrate the zero point of the potentiometer (or instrument) and anemometer for measuring T, 5.2 Adjust and control the cooling conditions
Perform according to the requirements of 4.3.
5.3 Measure and record intermediate parameters
After applying the heating current according to 4.1 and stabilizing, record Ir (or I
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