High-temperature reverse bias test method
By combining the temperature-sensitive electrical parameter method and the temperature control device, the problem of junction temperature measurement and control in high-temperature reverse bias test was solved, enabling accurate measurement and real-time control of modules with large leakage current, reducing the risk of thermal runaway and ensuring the stability of the test.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-23
- Publication Date
- 2026-04-07
AI Technical Summary
In high-temperature reverse bias tests, existing technologies struggle to accurately measure and control junction temperature, especially for modules with large leakage currents. The thermal resistance is difficult to calibrate scientifically, leading to uncontrollable test conditions and potentially causing thermoelectric positive feedback that results in module overcurrent breakdown.
Thermal resistance calibration is performed using the temperature-sensitive electrical parameter method, and shell temperature is controlled by a temperature control device. Accurate measurement and real-time control of junction temperature are achieved through circulation pipelines and oil system. An independent temperature control device is used to adjust the temperature of each module under test.
It enables accurate measurement and rapid control of junction temperature, reduces the possibility of thermal runaway, is suitable for modules with large leakage current, and ensures the stability and reliability of the test process.
Smart Images
Figure CN121805802A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a high-temperature reverse bias test method. Background Technology
[0002] High Temperature Reverse Bias Test (HTRB) is a test that applies a reverse bias voltage at a high temperature. The increase in leakage current over time is used to determine if a device has failed, thus assessing its reliability. Temperature control is crucial in HTRB testing; excessively high temperatures accelerate device failure, while excessively low temperatures fail to effectively evaluate reliability. Standards require that the junction temperature of the device during HTRB testing be equal to its highest operating junction temperature, T0. jmax However, this requirement is very difficult to achieve. For low-voltage devices or modules, the maximum operating junction temperature is low, the rated voltage is low, and the leakage current is small, resulting in negligible losses due to leakage. The junction temperature is almost the same as the case temperature Tc. Therefore, it is only necessary to control the case temperature of the device to be the maximum operating junction temperature (Tc). c =T jmax For modules with multiple chips connected in parallel, the rated voltage is high and the leakage current is large. The loss caused by leakage current may reach hundreds of watts. During long-term testing, this will cause the module junction temperature to rise. Since leakage current and junction temperature are positively correlated, positive feedback can easily form, leading to overcurrent breakdown of the module. Summary of the Invention
[0003] This invention provides a high-temperature reverse polarization test method, which uses the temperature-sensitive electrical parameter method for thermal resistance calibration and employs a temperature control device to control the shell temperature, thereby achieving accurate measurement and control of the junction temperature during the test.
[0004] The high-temperature reverse polarization test method provided by this invention includes the following steps: S1. Heat the module under test to a preset temperature T and maintain it for a preset time, so that the junction temperature T j With shell temperature T c Similarly, a preset pulse voltage is applied to the module under test, and the leakage current I at different temperatures T is collected. R data; This step involves calibrating the temperature-sensitive parameters. Specifically, the module under test is mounted on a hot plate and heated to a preset temperature, such as 30°C, and held for 10 minutes to allow the module to reach thermal equilibrium. At this point, the internal temperature of the module reaches equilibrium, and the junction temperature T0 is determined. j With shell temperature T cThe temperature is the same for both, 30℃. The signal generator applies a pulsed square wave signal to the control IGBT, causing the module under test to apply a pulse voltage. The pulse width should be as narrow as possible, for example, 200μs. The principle is that the pulse width should not be too long, otherwise it will easily cause self-heating, but the pulse width should not be less than the sampling period of the leakage current. Time matching is used to avoid the loss or distortion of the leakage current pulse. This process is repeated 4 to 5 times, and different leakage currents are collected at different temperatures (such as 30℃, 60℃, 90℃, 120℃, 150℃) to reduce errors. S2, the leakage current I obtained from S1 R By performing a linear fit with the temperature T data, we obtain ln(I R The functional relationship between leakage current and temperature (I / T); In the HTRB test, the PN junction in the power semiconductor chip is subjected to a bias voltage. Under a fixed voltage, the relationship between leakage current and temperature is I / T. R ∝E g / e nkT Among them, E g Let I be the bandgap width, k be the Boltzmann constant, and n be the injection coefficient. Taking the logarithm of both sides yields ln(I0). R ) = A / T + B, where A and B are parameters.
[0005] S3. Heat the module under test to near the target test temperature, and apply the test voltage V to the module under test. R Collect leakage current I R Data and reference point temperature T ref Leakage current I R After stabilization, calculate the junction temperature T based on the fitted curve in S2. j Thus, the thermal resistance R of the system is obtained. th =(T j -T ref ) / V R I R Heat the module under test (DUT) to near the target test temperature (typically the maximum junction temperature), for example, 5°C lower than the maximum junction temperature. Apply a continuous signal to the control IGBT, keeping it in the normally open state. Apply the test voltage to the DUT and begin acquiring the device's leakage current and reference point temperature T. ref (No need to limit it to shell temperature T) c (This could be the temperature of a component in a temperature control device). After the leakage current stabilizes, the junction temperature T can be calculated based on the fitting curve of S2. j Then, the thermal resistance R of the system is calculated. th Complete the calibration of the thermal resistance value.
[0006] S4. Start the test and collect the leakage current I in real time. R and reference point temperature T ref Calculate the real-time junction temperature T j =T ref+R th V R I R The temperature of the module under test is adjusted using a temperature control device to achieve the desired junction temperature T. j The goal is to reach and maintain the highest junction temperature. HTRB testing can employ two control strategies: one is constant case temperature, which is currently widely adopted in equipment. However, for modules with high leakage current, fluctuations in leakage current can easily disrupt the thermal balance, leading to thermoelectric positive feedback and causing overcurrent breakdown. The other strategy is constant junction temperature TB. j However, the shell temperature T needs to be controlled in real time. c To ensure junction temperature T j Since the thermal resistance is constant, it is necessary to calculate the thermal resistance of the system.
[0007] In one implementation, the pulse voltage in S1 and the test voltage V in S3 R same.
[0008] In one implementation, for parallel testing of multiple modules under test, each module under test is temperature-controlled using an independent temperature control device.
[0009] In one embodiment, the temperature control device includes a temperature regulating base, a heating element, an oil pump, a radiator, and a circulation pipeline. The circulation pipeline is filled with oil and is connected in series with the temperature regulating base, the heating element, the oil pump, and the radiator. The module under test is connected to the temperature regulating base.
[0010] In one implementation, the circulation pipeline is filled with oil, and when the junction temperature T of the module under test is... j When the temperature is too low, the heating element operates, raising the oil temperature. The oil pump power increases to improve the oil flow rate, causing the temperature control base to heat up rapidly and then heat the module under test. When the junction temperature T of the module under test... j If the temperature is too high, increase the power of the radiator and oil pump to quickly cool the temperature control base and the module under test.
[0011] In one implementation, the radiator is an air-cooled radiator.
[0012] In one embodiment, thermal grease is provided between the temperature control base and the module under test.
[0013] In one implementation, the oil in the circulation pipeline is fluorinated oil.
[0014] In one implementation, the reference point temperature T ref This is for adjusting the temperature of the heating element.
[0015] Compared with the prior art, the advantages of the present invention are as follows: 1. The thermal resistance calibration based on the temperature-sensitive electrical parameter method solves the problem of scientific calibration of thermal resistance in HTRB test and realizes accurate measurement of junction temperature; 2. Continue to use the thermal resistance method to calculate the junction temperature, instead of directly using leakage current to measure the junction temperature, to avoid the impact of leakage current fluctuations caused by product degradation on the junction temperature measurement; 3. Each module under test uses an independent temperature control device, which can achieve precise real-time control of junction temperature. It is especially suitable for power modules with large leakage current, reducing the possibility of thermal runaway during HTRB testing. Attached Figure Description
[0016] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.
[0017] Figure 1 This is a flowchart of the high-temperature reverse polarization test method in an embodiment of the present invention; Figure 2 This is a schematic diagram of the temperature control device in the high-temperature reverse polarization test method of the present invention. Figure 3 In an embodiment of the present invention, the leakage current I R A graph showing the data of temperature as a function of 1 / T, the reciprocal of temperature.
[0018] Figure label: 1. Temperature control base; 2. Heating element; 3. Oil pump; 4. Radiator; 5. Circulation pipeline; 6. Module under test; 7. Thermal grease. Detailed Implementation
[0019] The invention will now be further described with reference to the accompanying drawings.
[0020] To address the issue of junction temperature measurement, current equipment primarily employs the thermal resistance method to calculate the device junction temperature T. j The calculation formula is shown in equation (1), where R th Typically, this is the junction-to-case thermal resistance of the device (usually obtained from the datasheet), V R It is the bias voltage applied to the device, I R It is the leakage current generated by the device.
[0021] T j =T c +R th V R I R (1) The core of this method is the setting of the thermal resistance value, which directly affects the junction temperature T. j However, the calculation of thermal resistance on equipment currently lacks a scientific method, mainly in the following three aspects: ① For the HTRB test of the module, the test tube is usually IGBT and FRD chip connected in parallel. When measuring the junction-case thermal resistance, only the independent thermal resistance of IGBT and FRD can be measured separately. The thermal resistance of both heating up at the same time cannot be obtained. ② Junction-to-case thermal resistance R of the device th It is not fixed, but closely related to heat dissipation conditions. Generally, the better the external heat dissipation conditions, the better the R... th The larger the value, the more likely the thermal resistance value on the datasheet is measured under water cooling, while in the HTRB test, the module is in a passive heating state. ③ For modules with large leakage current, the module is usually installed on the heat sink for HTRB testing, which introduces additional contact thermal resistance and heat sink thermal resistance. Compared with the junction thermal resistance, these two types of thermal resistance are more difficult to determine.
[0022] In addition, during the HTRB test, the leakage current of the module under test may fluctuate or degrade, and the loss generated by the leakage current will also change accordingly. If a constant case temperature is used, the junction temperature will change accordingly. Due to the positive feedback relationship between leakage current and junction temperature, the test conditions are uncontrollable. Currently, some equipment provides a constant junction temperature mode. The control logic is based on formula (1) and adjusts the case temperature according to the real-time monitoring value of the leakage current. However, the case temperature response time is very long under oven-type or hot plate-type heating methods, and it is impossible to keep up with the control in time.
[0023] To address the two issues mentioned above, this invention proposes a high-temperature reverse bias test method. This method uses a temperature-sensitive electrical parameter method for thermal resistance calibration and an oil circuit heating system for shell temperature control, thereby achieving accurate measurement and rapid control of the junction temperature during the test.
[0024] like Figure 1 As shown, the high-temperature reverse bias test method of the present invention includes the following steps: S1, heating the module under test to a preset temperature T and maintaining it for a preset time, so that the junction temperature T j With shell temperature T c Similarly, a preset pulse voltage is applied to the module under test, and the leakage current I at different temperatures T is collected. R data; This step involves calibrating the temperature-sensitive parameters. Specifically, the module under test is mounted on a hot plate and heated to a preset temperature of 30°C. This temperature is maintained for 10 minutes to allow the module to reach thermal equilibrium. At this point, the internal temperature of the module reaches equilibrium, and the junction temperature T0 is determined. j With shell temperature T c The temperature is the same for both, 30℃. The signal generator applies a pulsed square wave signal to the control IGBT, causing the module under test to apply a pulse voltage. The pulse width should be as narrow as possible, for example, 200μs. The principle is that the pulse width should not be too long, otherwise it will easily cause self-heating, but the pulse width should not be less than the sampling period of the leakage current. Time matching is used to avoid the loss or distortion of the leakage current pulse. This process is repeated 4 to 5 times, and different leakage currents are collected at different temperatures (30℃, 60℃, 90℃, 120℃, 150℃) to reduce errors. The temperature-sensitive parameter calibration data of one embodiment is shown in Table 1:
[0025] Table 1 S2, the leakage current I obtained from S1 R By performing a linear fit with the temperature T data, we obtain ln(I R The functional relationship between leakage current and temperature (I / T); In the HTRB test, the PN junction in the power semiconductor chip is subjected to a bias voltage. Under a fixed voltage, the relationship between leakage current and temperature is I / T. R ∝Eg / e nkT Where Eg is the bandgap width, k is the Boltzmann constant, and n is the injection coefficient (value is 1 or 2). Taking the logarithm of both sides yields ln(I R The equation is: ) = A / T + B, where A and B are parameters. It's important to note that the unit of T during fitting should be K, for example, 30℃ = 303K.
[0026] Leakage current I in one embodiment R The data for the reciprocal of temperature, 1 / T, are as follows: Figure 3 As shown.
[0027] S3. Heat the module under test to near the target test temperature, and apply the test voltage V to the module under test. R Collect leakage current I R Data and reference point temperature T ref Leakage current I R After stabilization, calculate the junction temperature T based on the fitted curve in S2. j Thus, the thermal resistance R of the system is obtained. th =(T j -T ref ) / V R I R Heat the module under test to near the target test temperature (usually the highest junction temperature T). jmax (This can be 5°C lower than the highest junction temperature.) A continuous signal is applied to the control IGBT, keeping it in the normally open state. The test voltage is applied to the module under test, and the leakage current and reference point temperature T of the device are collected. ref (The reference point temperature T here) ref Not limited to shell temperature T c The temperature could be the temperature of a component in the temperature control device, such as the temperature of the temperature control base 1. By selecting different reference points, the thermal resistance R of the system will change. th (This will also change). Once the leakage current stabilizes, the junction temperature T can be calculated based on the fitting curve of S2. j Then, the thermal resistance R of the system is calculated. th Complete the calibration of the thermal resistance value.
[0028] S4. Start the test and collect the leakage current I in real time. Rand reference point temperature T ref Calculate the real-time junction temperature T j =T ref +R th V R I R The temperature of the module under test is adjusted using a temperature control device to achieve the desired junction temperature T. j Reaching the highest junction temperature T jmax And keep it constant. HTRB testing can have two control strategies: one is to keep the case temperature constant, which is the strategy widely adopted in current equipment. For modules with large leakage current, once the leakage current fluctuates, it is easy to disrupt the thermal balance, forming thermoelectric positive feedback and causing the module to overcurrent and break down; the other is to keep the junction temperature T constant. j However, the shell temperature T needs to be controlled in real time. c To ensure junction temperature T j Since the thermal resistance is constant, the first step is to calculate the system's thermal resistance using S3.
[0029] Furthermore, the pulse voltage in S1 and the test voltage V in S3 R The conditions must be identical to ensure consistency between the experimental conditions before and after the experiment.
[0030] Furthermore, for parallel testing of multiple modules under test, each module is equipped with an independent temperature control device. This independent temperature control allows for precise real-time control of the junction temperature, which is particularly suitable for power modules with high leakage current, reducing the possibility of thermal runaway during HTRB testing.
[0031] like Figure 2 As shown, the temperature control device includes a temperature regulating base 1, a heating element 2, an oil pump 3, a radiator 4, and a circulation pipeline 5. The circulation pipeline 5 is filled with oil and connects the temperature regulating base 1, the heating element 2, the oil pump 3, and the radiator 4 in series. The module under test 6 is connected to the temperature regulating base 1. To improve heat conduction, thermal grease 7 is also provided between the temperature regulating base 1 and the module under test 6.
[0032] Specifically, the circulation pipe 5 is filled with oil. The higher the operating power of the oil pump 3, the faster the oil flow rate in the circulation pipe 5, thus enabling the temperature control base 1 to heat up or cool down more quickly. When the junction temperature T of the module under test 6... j When the temperature is too low, the heating element 2 operates to raise the oil temperature, and the oil pump 3 increases its power to increase the oil flow rate, causing the temperature control base 1 to heat up rapidly and heat the module under test 6. When the junction temperature of the module under test 6 is T... jWhen the temperature is too high, the power of radiator 4 and oil pump 3 is increased to rapidly cool the temperature control base 1 and the module under test 6, thereby achieving rapid temperature regulation of the module under test 6. The temperature control device adopts a PID control algorithm. PID control only requires three parameters (proportional, integral, and derivative) to build a closed-loop feedback system, without relying on complex mathematical models, thus reducing the requirement for accurate modeling of the controlled object.
[0033] Furthermore, radiator 4 is an air-cooled radiator. By adjusting the operating power of the fan in radiator 4, the oil in the circulation pipe 5 can be cooled, and the cooling rate can be adjusted within a wide range to meet the experimental requirements.
[0034] Specifically, the oil in circulation line 5 is fluorinated oil. Fluorinated oil has excellent high-temperature resistance, outstanding chemical inertness, corrosion resistance, and excellent electrical insulation properties, which can support the long-term stable operation of the temperature control device.
[0035] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.
Claims
1. A high-temperature reverse polarization test method, characterized in that, Includes the following steps: S1. Heat the module under test to a preset temperature T and maintain it for a preset time, so that the junction temperature T j With shell temperature T c Similarly, a preset pulse voltage is applied to the module under test, and the leakage current I at different temperatures T is collected. R data; S2, the leakage current I obtained from S1 R By performing a linear fit with the temperature T data, we obtain ln(I R The functional relationship between 1 / T and 1 / T; S3. Heat the module under test to near the target test temperature, and apply the test voltage V to the module under test. R Collect leakage current I R Data and reference point temperature T ref Leakage current I R After stabilization, calculate the junction temperature T based on the fitted curve in S2. j Thus, the thermal resistance R of the system is obtained. th =(T j -T ref ) / V R I R ; S4. Start the test and collect the leakage current I in real time. R and reference point temperature T ref Calculate the real-time junction temperature T j =T ref +R th V R I R The temperature of the module under test is adjusted using a temperature control device to achieve the desired junction temperature T. j It reaches the highest junction temperature and remains constant.
2. The high-temperature reverse polarization test method according to claim 1, characterized in that, The pulse voltage in S1 and the test voltage V in S3 R Similarly, the pulse width of the pulse voltage is not shorter than the leakage current I. R The sampling period.
3. The high-temperature reverse polarization test method according to claim 1, characterized in that, In S2, for formula I R ∝E g / e nkT Taking the logarithm of both sides gives ln(I) R ) = A / T + B; Among them, E g Where is the bandgap width, k is the Boltzmann constant, n is the injection coefficient, and A and B are both parameters.
4. The high-temperature reverse polarization test method according to claim 1, characterized in that, For parallel testing of multiple modules under test, each module under test is controlled by an independent temperature control device.
5. The high-temperature reverse polarization test method according to claim 1, characterized in that, The temperature control device includes a temperature regulating base, a heating element, an oil pump, a radiator, and a circulation pipeline. The circulation pipeline is filled with oil and is connected in series with the temperature regulating base, the heating element, the oil pump, and the radiator. The module under test is connected to the temperature regulating base.
6. The high-temperature reverse polarization test method according to claim 5, characterized in that, The circulation pipeline is filled with oil. When the junction temperature T of the module under test is... j When the temperature is too low, the heating element operates, raising the oil temperature. The oil pump power increases to improve the oil flow rate, causing the temperature control base to heat up rapidly and then heat the module under test. When the junction temperature T of the module under test... j If the temperature is too high, increase the power of the radiator and oil pump to quickly cool the temperature control base and the module under test.
7. The high-temperature reverse polarization test method according to claim 6, characterized in that, The radiator is an air-cooled radiator.
8. The high-temperature reverse polarization test method according to claim 5, characterized in that, Thermal grease is applied between the temperature control base and the module under test.
9. The high-temperature reverse polarization test method according to claim 5, characterized in that, The oil in the circulation pipeline is fluorinated oil.
10. The high-temperature reverse polarization test method according to claim 5, characterized in that, Reference point temperature T ref This is for adjusting the temperature of the heating element.