Thermal resistance testing method for power type discrete semiconductor device

Abstract

The invention discloses a thermal resistance test based on a power-type semiconductor discrete device, and detailed analysis is carried out in the aspect of improving the accuracy of the thermal resistance test by adopting a test analysis mode. The accuracy of device shell temperature measurement is improved by means of X-ray analysis, investigation of the physical position of a product chip and the like, and the accuracy of thermal resistance test is directly influenced. The thermal resistance testing method is simple and easy to implement, the chip in the device is accurately positioned in a lossless mode, a key role is played in follow-up accurate measurement of the thermal resistance value, test equipment is universal equipment in a test room, and the technical cost can be reduced while the thermal resistance value measurement accuracy is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic component testing, and in particular to a method for testing thermal resistance of a power semiconductor device. BACKGROUND

[0002] Power semiconductor devices are widely used in the fields of electronic communication, new energy, aerospace, etc. With the development of power devices, the working current and voltage are increasing, and the analysis of the heat dissipation performance of the device becomes particularly important. Among the failure rates of domestic discrete devices in the field, about 50% are related to electrical and thermal stress, which includes parameter drift, short circuit, and open circuit. Therefore, accurately obtaining the thermal conduction performance of the device package is very important for improving the working performance, reliability of the device, and improving the thermal design of the package.

[0003] In a circuit, the resistance encountered by the current during flow can be represented by resistance. Similarly, in the process of heat conduction, thermal resistance represents the resistance of heat flow. Thermal resistance is divided into transient thermal resistance and steady-state thermal resistance according to the power condition. Transient thermal resistance: the thermal resistance measured when T J has not yet reached stability after the power step change of the device. At this time, T C may not have changed yet, or it may not have stabilized. Steady-state thermal resistance: the thermal resistance measured when T J and T C have reached a stable state after the device is powered by a constant power. Among them, the thermal resistance calculated by the average junction temperature (electrical method) is the steady-state average thermal resistance, and the thermal resistance calculated by the peak junction temperature (infrared thermal imaging method) is the steady-state peak thermal resistance. With the same temperature difference, the greater the thermal resistance, the smaller the heat flow, and the more difficult it is to transmit. Therefore, an important quantitative indicator for measuring the heat dissipation capacity of a device is thermal resistance. At the same time, thermal resistance is an important technical index and characteristic of electronic component packaging, and is a commonly used evaluation parameter in thermal analysis. The purpose of thermal design is to hope that the packaging structure is easy to dissipate heat, and the smaller the thermal resistance, the better.

[0004] In the JESD51 standard, the junction-to-ambient thermal resistance is defined as the thermal resistance from the working part of the semiconductor device to the surface of the closest shell to the mounting area of the chip, which also clearly defines that the temperature reference point position needs to be set as close as possible to the surface of the closest shell to the working area of the chip during the thermal resistance test, thereby reducing the error of the thermal resistance test. In the GJB128 and other related standards of semiconductor devices, the method for testing the thermal resistance of semiconductor devices only states that the thermocouple for measuring the shell temperature needs to be at the specified reference point, and does not provide detailed instructions on the selection of the reference point and the installation method of the device. This also indirectly affects the accuracy of the thermal resistance test of similar semiconductor devices under the same test equipment. SUMMARY

[0005] Therefore, the present application aims to accurately position the internal chip of the device in a non-destructive manner, and accurately place the thermocouple for measuring the shell temperature of the measuring device at the heat center position, which plays a key role in the subsequent accurate measurement of the thermal resistance value, and the test equipment is a general laboratory equipment, which can improve the accuracy of thermal resistance measurement and reduce the technical cost.

[0006] The specific technical solutions adopted by the present application are as follows:

[0007] A power type semiconductor discrete device thermal resistance testing method, comprising the following steps:

[0008] Step one: test the thermal resistance of the device by using the thermocouple method, place the measured semiconductor device on the heat sink of the water cooling platform, and directly measure the surface temperature of the contact shell with the thermocouple; The water cooling platform is provided with a pressure rod for providing pressure to the semiconductor device to make it in good contact with the water cooling platform; A hole is opened on the heat sink so that the thermocouple can be located on the surface of the water cooling platform; Use heat-conducting silicone grease to fill the gap between the water cooling platform and the semiconductor device;

[0009] Step two: selection of test objects;

[0010] Step three: X-ray inspection of the semiconductor device before thermal resistance testing, find the chip position of the semiconductor device, and determine the heat source of the device;

[0011] Step four: place the thermocouple directly below the center of the semiconductor device chip, and test the thermal resistance of the semiconductor device.

[0012] Preferably, when selecting test objects, select devices with large-area metal plates on the device shell.

[0013] Preferably, after testing the thermal resistance of the semiconductor device, the test results are divided into two groups along the horizontal direction of the device and along the vertical direction of the device for data analysis.

[0014] The present application has the following advantages:

[0015] The key of testing thermal resistance parameter of power semiconductor device by using existing equipment and method is how to install thermocouple at the position closest to the heat center of the device. The thermal resistance test plays a vital role in the heat dissipation performance of the power device. The positioning of the chip of the device by X-ray inspection and the analysis of the device packaging structure and material are more conducive to accurately finding out the thermal resistance parameter. The domestic relevant standards do not further refine the test method steps and solidify the related test process and operation in view of the variables in the test process. The thermal resistance test method of the scheme is simple and easy to operate, the internal chip of the device is accurately positioned by the nondestructive method, and plays a key role in the subsequent accurate measurement of the thermal resistance value. The test equipment is general equipment in the laboratory, which can improve the accuracy of the thermal resistance value measurement and also reduce the technical cost. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a water cooling platform and device installation schematic diagram.

[0017] Figure 2 It is a sample device physical map.

[0018] Figure 3 It is a sample device X-ray appearance.

[0019] Figure 4 It is a thermocouple and semiconductor device installation area.

[0020] Figure 5 It is a chip position and test point schematic diagram.

[0021] 1-semiconductor device, 2-pressing rod, 3-pressing plate and gasket, 4-radiator, 5-cooling water, 6-plastic sleeve, 7-thermocouple wire, 8-thermocouple probe assembly, 9-thermocouple. DETAILED DESCRIPTION

[0022] The design results of the present application will be further described below in combination with the drawings and thermal resistance test.

[0023] The technical solution of the present application is to improve the accuracy of thermal resistance test by using test analysis method, and the specific steps are as follows:

[0024] Step one: test the thermal resistance of the device by using thermocouple method, place the measured semiconductor device 1 on the radiator 4 of the water cooling platform as shown in Figure 1 , directly measure the surface temperature of the semiconductor device 1 shell in contact with the thermocouple 9. The water cooling platform is provided with a pressing rod 2, which can provide a certain pressure for the semiconductor device 1 to make it in good contact with the water cooling platform. In order to measure the temperature of the shell in contact with the radiator 4, a hole is opened on the radiator 4, so that the thermocouple 9 can be located on the surface of the water cooling platform. Figure 2The diagram shows the installation of the water-cooled platform and semiconductor device 1. The front end of thermocouple 9 needs to be in direct mechanical contact with the bottom of the semiconductor device 1's housing. The clamping rod 2 of the water-cooled platform can bring device 1 into contact with thermocouple 9 with a fixed force. To enable thermocouple 9 to more accurately detect the temperature of semiconductor device 1's housing, thermal grease needs to be used to fill the gap between the water-cooled platform and device 1.

[0025] Step Two: Selection of Test Object: Refer to a certain type of power field-effect transistor. This type of package has a relatively flat base surface. A physical image is shown below. Figure 2 As shown. The package has a large metal backplate, which is beneficial for the installation of thermocouple 9 and the overall heat dissipation of the device, effectively transferring and dispersing the heat generated inside the package.

[0026] Step 3: Before thermal resistance testing, X-ray inspection of device 1 can help locate the chip position, thereby identifying the heat source of device 1 and further improving the accuracy of thermal resistance testing. Figure 4 The X-ray image shown indicates that the chip for this device model is rectangular and located at the bottom of the device. The mounting areas for thermocouple 9 and device 1 are as follows. Figure 5 As shown in the figure, thermocouple 9 is located directly below the center of the chip.

[0027] Step 4: Perform thermal resistance testing on device 1 according to the equipment testing procedures. Using the above steps can reduce thermal resistance testing errors and improve testing accuracy.

[0028] Example:

[0029] Step 1: Test the K-coefficient of the device. The K-coefficient is the sensitivity coefficient of the temperature sensor, and it needs to be calibrated for each specific device and package. The forward conduction voltage V of the body diode within the field-effect transistor. F The relationship between voltage and temperature is linear, and the reciprocal of the slope of the curve is defined as the K coefficient. The junction temperature of a device at a given voltage value can be estimated using the K coefficient. During the experiment, liquid mineral oil with high thermal conductivity and good insulation was used as the heat transfer medium, and the V-temperature was established using the oil bath method. F The relationship curve between temperature T and temperature is obtained as follows: Figure 3 The K-curve shown.

[0030] Step 2: Connect the field-effect transistor (as shown in the physical diagram) Figure 2 (As shown) Placed as Figure 1 On the water-cooled platform shown, the temperature of the contacted housing surface is directly measured using thermocouple 9. A clamping rod 2 is mounted on the water-cooled platform to provide pressure to the semiconductor device 1, ensuring good contact with the platform. To measure the temperature of the housing in contact with the heat sink 4, a hole is made in the heat sink 4 so that the thermocouple 9 can be positioned on the surface of the water-cooled platform.

[0031] Step 3: Before thermal resistance testing, X-ray inspection of device 1 can help locate the chip position, thereby identifying the heat source and further improving the accuracy of the thermal resistance test. Figure 4 The X-ray image shown indicates that the chip for this device model is rectangular and located at the bottom of the device. The mounting areas for thermocouple 9 and device 1 are as follows. Figure 5 As shown in the figure, thermocouple 9 is located directly below the center of the chip.

[0032] Step 4: Perform thermal resistance testing on device 1 according to the equipment testing procedures. Using the above steps can reduce thermal resistance testing errors and improve testing accuracy.

[0033] The test results are shown in Tables 1 and 2. The results were divided into two groups for data analysis: one along the transverse direction and the other along the longitudinal direction. The starting test point for both directions was point 'a'. The thermal resistance difference and rate of change between the next and previous test points were calculated sequentially. The results show that the thermal resistance difference between two test points along the longitudinal direction is relatively large, with a maximum rate of change exceeding 6%. The difference between two test points along the transverse direction is smaller, with a maximum rate of change close to 2%. From the perspective of the device package structure, even a slight deviation of 1 mm in the measurement position will result in a significant change in thermal resistance. Therefore, finding the geometric center of the chip using this method will have a significant impact on the test results.

[0034] The thermal resistance testing method of this invention is simple and easy to implement. It accurately locates the chip inside the device in a non-destructive manner, which plays a key role in the subsequent accurate measurement of thermal resistance value. Moreover, the test equipment is all general laboratory equipment, which improves the accuracy of thermal resistance value measurement while reducing technical costs.

[0035] The specific embodiments described above only illustrate the design principles of the present invention. The shapes and names of the components in this description may differ and are not limited. Therefore, those skilled in the art can modify or make equivalent substitutions to the technical solutions described in the foregoing embodiments; and these modifications and substitutions do not depart from the inventive spirit and technical solutions of the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A method for testing the thermal resistance of a power-type discrete semiconductor device, characterized in that, Includes the following steps: Step 1: Test the thermal resistance of the device using the thermocouple method. Place the semiconductor device under test on the heat sink of the water-cooled platform and directly measure the surface temperature of the housing in contact with the thermocouple. A pressure rod is installed on the water-cooled platform to provide pressure to the semiconductor device to ensure good contact with the water-cooled platform. A hole is made in the heat sink so that the thermocouple can be located on the surface of the water-cooled platform. Use thermal grease to fill the gap between the water-cooled platform and the semiconductor device. Step Two: Selection of Test Subjects; Step 3: Before thermal resistance testing, perform X-ray inspection on the semiconductor device to locate the chip position and thus determine the heat source of the device; Step 4: Place the thermocouple directly below the center of the semiconductor device chip to perform a thermal resistance test on the semiconductor device.

2. The method for testing the thermal resistance of a power semiconductor discrete device according to claim 1, characterized in that, When selecting test objects, devices with a large area of ​​metal plate in the device housing are selected.

3. The method for testing the thermal resistance of a power semiconductor discrete device according to claim 1, characterized in that, After performing thermal resistance tests on semiconductor devices, the test results are divided into two groups: one along the transverse direction of the device and the other along the longitudinal direction of the device, for data analysis.

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