Online evaluation method and detection circuit for aging state of bonding wire based on dynamic characteristic parameters of SiC MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor)

Abstract

The invention relates to a SiC MOSFET bonding wire aging state evaluation method based on turn-on delay time, and the method achieves the real-time monitoring and quantitative evaluation of the aging state of a bonding wire through measuring the turn-on delay time tdon of a SiC MOSFET in the working process. According to the invention, the turn-on delay time detection circuit is designed, the turn-on delay time of the SiC MOSFET can be accurately measured, and the aging degree of the bonding wire can be accurately reflected by analyzing the change of the parameter. The method has the advantages of high accuracy, real-time monitoring, high adaptability and the like, and is suitable for SiC MOSFET devices with different working condition parameters. According to the invention, an operator can find potential fault hidden dangers in time, the maintenance cost of the system is reduced, and the reliability and stability of the system are improved. According to the invention, a new thought and method are provided for health monitoring and evaluation of the SiC MOSFET, and innovation and development of a health monitoring technology of a power electronic device can be promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of health monitoring and evaluation of power electronic devices, and in particular monitors and analyzes dynamic characteristic parameters of SiC (silicon carbide) MOSFET (metal oxide semiconductor field effect transistor) to evaluate the aging state of its bonding wires. Background Art

[0002] Compared with traditional Si MOSFET, SiC MOSFET (Silicon Carbide Metal Oxide Semiconductor Field Effect Transistor) has shown great potential in the power field with its advantages of high frequency, high voltage resistance, high temperature resistance and low loss. However, the packaging aging of SiC MOSFET devices, especially the aging of bonding wires, has become a key factor restricting its performance, mainly manifested in the degradation of bonding wire material properties, weakened connection strength, falling off or breaking, etc., which directly affects the electrical performance and mechanical strength of SiC MOSFET devices, and may even cause the failure of SiC MOSFET devices.

[0003] There are many shortcomings in the current methods for evaluating SiC MOSFET bond wire aging. Although the power cycle test method can simulate the aging process in actual applications, the test equipment is expensive, the cycle is long, the cost is high, and real-time detection cannot be achieved. Although the active physical measurement method provides a variety of detection methods, it also faces problems such as high test cost, complex operation, and insufficient accuracy. Although the SiC MOSFET dynamic characteristic parameter characterization method has the advantages of high precision and high sensitivity, its evaluation effect is highly dependent on the sensitivity and accuracy of the selected characterization parameters, and the detection or measurement of the characterization parameters is still a major bottleneck restricting its application. Summary of the invention

[0004] In order to solve the above-mentioned deficiencies of the prior art, the present invention proposes a bonding wire aging evaluation method based on the dynamic characteristic parameters of SiC MOSFET, which converts the dynamic characteristic parameters of SiC MOSFET in the process of turning on (i.e., changing from the off state to the on state) - the turn-on delay time t don As a characterization parameter for evaluating the aging of SiC MOSFET bonding wires, the aging degree of the bonding wires is characterized.

[0005] The principle of the present invention is as follows:

[0006] SiC MOSFET turn-on delay time t don It can be shown by formula 1:

[0007]

[0008] In the formula, R g is the driving resistance of the SiC MOSFET driving circuit, V gs,onis the driving voltage, V th is the threshold voltage of SiC MOSFET, C gs and C gd They are the equivalent gate-source capacitance and equivalent gate-drain capacitance of SiC MOSFET respectively.

[0009] The physical structure of a single SiC MOSFET cell is shown below: Figure 7 As shown in Figure 2. The equivalent capacitance inside the SiC MOSFET mainly includes the gate-source capacitance C gs , gate-drain capacitance C gd and source-drain capacitance C ds . Gate-source capacitance C gs It is formed by the gate oxide layer between the gate metal and the source semiconductor, and controls the effect of the gate voltage on the channel charge. gd The source-drain capacitance C is generated due to the electric field coupling between the gate metal and the drain semiconductor, which affects the feedback of the gate voltage to the drain voltage. ds It depends on the width of the depletion layer between the drain and the source, and changes with the drain voltage. These capacitors play a key role in the switching process, affecting the switching speed, loss and stability of the device. In the SiC MOSFET turn-on delay stage, i.e., Stage 1, the gate-source capacitance C gs , gate-drain capacitance C gd are not affected by the internal channel charge of the SiC MOSFET cell and the charge of the N-type drift region. Therefore, the gate-source capacitance C gs , gate-drain capacitance C gd The structure is mainly composed of the oxide layer capacitance inside the SiC MOSFET cell.

[0010] The SiC MOSFET wafer consists of multiple cells connected in parallel, and the cells are electrically connected through bonding wires and the copper layer on the substrate to form a complete wafer. Figure 8 As shown. The equivalent gate-source capacitance C of SiC MOSFETT device gs , gate-drain capacitance C gd , as shown in Formula 2.

[0011]

[0012] In formula 2, A represents the active area, which has a direct relationship with the aging degree of the bonding wire. ox and d ox are the dielectric constant and thickness of the oxide layer, respectively.

[0013] When the bonding wire of SiC MOSFET device ages, the active area A of SiC MOSFET decreases. According to equation 2, the gate-source capacitance C gs , gate-drain capacitance Cgd According to Formula 3, the threshold voltage V th The expression of the driving voltage V gs,on They are not affected by the reduction of active area A.

[0014]

[0015] In formula 3, ε s ,k,T,N A 、n i They are the dielectric constant of the semiconductor, the Boltzmann constant, temperature, semiconductor doping concentration and intrinsic semiconductor concentration, and these parameters are independent of the active area A of the SiC MOSFET.

[0016] Combining formula 1, we can know that the gate-source capacitance C gs , gate-drain capacitance C gd Reducing the turn-on delay time t of SiC MOSFET will don Reduce,

[0017] The technical solution of the present invention is as follows:

[0018] An online evaluation method for bonding wire aging status based on SiC MOSFET dynamic characteristic parameters is characterized in that it includes the following steps:

[0019] Step 1. Measure the turn-on delay time of SiC MOSFET:

[0020] The turn-on delay time detection circuit is used to capture and record the turn-on delay time t of SiC MOSFET in real time during operation. don ; Among them, the opening delay time t don is the gate voltage V gs The time required for the drain current Id to rise from 0 to 10% of the steady-state current IL;

[0021] Step 2. Run the SiC MOSFET device to obtain the actual operating parameters of the SiC MOSFET device;

[0022] Step 3. Based on the turn-on delay time t of SiC MOSFET don The actual operating parameters of SiC MOSFET devices are combined with the bond wire aging evaluation model based on turn-on delay time to evaluate the bond wire aging status of SiC MOSFET.

[0023] Further, in step 1, the delay time detection circuit is turned on, including:

[0024] A voltage divider circuit is used to control the input voltage within the power supply voltage of the voltage follower circuit and output it to the voltage follower circuit respectively;

[0025] The voltage follower circuit is used to buffer the signal transmission between the front-stage voltage divider circuit and the rear-stage voltage comparison circuit, isolate the mutual influence between the front-stage and rear-stage circuits, reduce the interference to the voltage signal, and output it to the voltage comparison circuit;

[0026] A voltage comparison circuit is used to compare the output of the voltage follower circuit with a preset reference voltage V TH1 and V TH2 For comparison, the reference voltage V TH1 Set to gate threshold voltage V th 10% of the reference voltage V TH2 Set to bus voltage V DC 90% of the value, and output the comparison result to the pulse synthesis circuit;

[0027] A pulse synthesis circuit is used to synthesize a pulse signal according to the output of the voltage comparison circuit, and the width of the pulse signal is equal to the turn-on delay time t of the SiC MOSFET. don .

[0028] Furthermore, the voltage comparison circuit includes at least two voltage comparators, which are respectively used to compare the gate voltage V gs With reference voltage V TH2 and the drain-source voltage V ds With reference voltage V TH2 , and output the comparison result.

[0029] Furthermore, the pulse synthesis circuit includes a logic gate circuit for synthesizing a pulse signal that meets the conditions according to the output of the voltage comparison circuit.

[0030] Furthermore, the V gs The V terminal and the corresponding GND terminal are connected to the gate terminal and Kelvin terminal of the SiCMOSFET device respectively; ds The terminal and the corresponding GND terminal are connected to the drain terminal and source terminal of the SiC MOSFET respectively; V TH1 Terminals and V TH2 The terminals are used to set the reference voltage V TH1 and V TH2 .

[0031] Furthermore, the output of the opening delay time detection circuit is connected to an I / O port of an oscilloscope or an MCU with a pulse time detection function, and the communication port of the MCU or oscilloscope is connected to a host computer to transmit detection data in real time.

[0032] Further, the step of establishing the bonding wire aging assessment model based on the opening delay time in step 3. includes:

[0033] Step 3.1 Select SiC MOSFET devices with different bond wire aging states;

[0034] Step 3.2: Determine the test conditions, including voltage, current, and temperature parameters;

[0035] Step 3.3: Perform a double pulse test on the SiC MOSFET device and collect turn-on delay time data;

[0036] Step 3.4 processes and analyzes the collected data to extract the relationship between the turn-on delay time and the bonding wire aging state;

[0037] Step 3.5 constructs a SiC MOSFET device bond wire aging model based on turn-on delay time considering different operating parameters based on statistical methods.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1) By measuring the turn-on delay time t of SiC MOSFET don， This dynamic characteristic parameter enables quantitative evaluation of the aging status of the bonding wire and improves the accuracy of the evaluation.

[0040] 2) Use the turn-on delay time detection circuit to monitor the turn-on delay time t of SiC MOSFET in real time during operation don , without stopping or disassembling the device, the aging status of the bonding wire can be monitored online, which helps to timely discover potential fault hazards and avoid system shutdown or damage caused by device failure. By real-time monitoring and accurate evaluation of the aging status of SiCMOSFET bonding wires, operators can take timely measures, such as replacing aging devices, to avoid system shutdown or damage caused by device failure. This helps to reduce the maintenance cost of the system and improve the reliability and stability of the system.

[0041] 3) Designed with gate threshold voltage V th 10% as the starting point and the bus voltage V DC A SiC MOSFET turn-on delay time detection circuit with 90% of the turn-on delay time as the endpoint is constructed. A SiC MOSFET device bond wire aging evaluation method is constructed with the turn-on delay time, the turn-on delay time detection circuit and the SiC MOSFET device bond wire aging model based on the turn-on delay time as the core.

[0042] 4) The present invention is not only applicable to a specific type of SiC MOSFET, but also can adapt to SiC MOSFET devices with different operating parameters such as voltage, current, and temperature by adjusting the resistance ratio in the voltage divider circuit and setting a suitable reference voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of SiC MOSFET turn-on process

[0044] Figure 2 Schematic diagram of the turn-on delay time detection circuit for SiC MOSFET

[0045] Figure 3 Connection diagram for the turn-on delay time detection circuit and SiC MOSFET device

[0046] Figure 4 The signal flow diagram and output waveform of the detection circuit

[0047] Figure 5 Build a process for modeling bond wire aging based on turn-on delay time

[0048] Figure 6 Schematic diagram of the overall system operation for bond wire aging status assessment of SiC MOSFET devices

[0049] Figure 7 Physical structure diagram of a single SiC MOSFET cell

[0050] Figure 8 Schematic diagram of multiple cells connected in parallel on a SiC MOSFET wafer DETAILED DESCRIPTION

[0051] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments, but the protection scope of the present invention shall not be limited thereto.

[0052] This embodiment provides a bonding wire aging evaluation method based on the dynamic characteristic parameters of SiC MOSFET, by measuring the turn-on delay time t don , to evaluate the aging status of its bonding wires.

[0053] The implementation path of the technical solution is mainly divided into two parts: one is the opening delay time t don The first is to design the detection circuit, and the second is to establish the bonding wire aging model based on the opening delay time.

[0054] According to relevant international standards such as IEC 60747-2019, the opening delay time t don The definition of is: the gate voltage Vgs from 0 is used as the start mark of the turn-on delay process, and the drain current Id rises to 10% of the steady-state current IL as the end mark of the turn-on delay process. Figure 1 As shown, t don Represents the time from when the gate voltage starts to rise until the drain current reaches 10% of the steady-state current. don_VdsIt represents the time when the gate voltage rises to 10% of the threshold voltage and the drain-source voltage V ds Drop to bus voltage V DC The end time is 90% of the don_Vds As the turn-on delay time of SiC MOSFET, the detection circuit is as follows Figure 2 As shown, it includes: a voltage divider circuit composed of high-precision resistors R1, R2, R3, and R4, a voltage follower circuit composed of high-precision operational amplifier 1 and high-precision operational amplifier 2, a voltage comparison circuit composed of voltage comparator 1 and voltage comparator 2, and a pulse synthesis circuit composed of logic gate-AND gate. The detection circuit can monitor the working state of SiC MOSFET in real time, especially the changes in gate voltage and drain-source voltage. By adjusting the resistance ratio in the voltage divider circuit and setting a suitable reference voltage, the change in the turn-on delay time of SiC MOSFET during operation can be accurately captured. Among them, the voltage divider circuit is used to control the voltage input into the voltage follower circuit within the power supply voltage of the high-precision operational amplifier. Taking the power supply voltage of the high-precision operational amplifier as 5V, the gate voltage V gs The voltage of the SiC MOSFET is within 0~20V, and the ratio of R1 to R2 is about 3, which is adjusted according to the actual situation. ds It will change according to the actual application scenario. Taking the 400V application scenario of SiC MOSFET devices as an example, the ratio of R3 to R4 is about 79 and is adjusted according to the actual situation. The voltage follower circuit uses the high impedance characteristics of high-precision op amp 1 and high-precision op amp 2 to reduce the impact on the original circuit characteristics. The output voltages of high-precision op amp 1 and high-precision op amp 2 are respectively input into voltage comparator 1 and voltage comparator 2. TH1 and V TH2 The comparison of the values ​​outputs a positive voltage or a negative voltage respectively. After passing through the logic AND gate, the pulse signal output by the voltage comparator 1 and the voltage comparator 2 through the logic gate can be finally obtained.

[0055] V gs The V terminal and the corresponding GND terminal are connected to the gate terminal and Kelvin terminal of the SiC MOSFET device respectively; ds The V terminal and the corresponding GND terminal are connected to the drain terminal and source terminal of the SiC MOSFET respectively. TH1 terminal and the corresponding GND terminal and V TH2 The terminal and the corresponding GND terminal are terminals for setting the reference voltage. TH1 The gate threshold voltage V th 10%, V TH2 The terminal and the corresponding GND terminal are set to the bus voltage V DC 90% of.

[0056] Figure 3 This is a connection diagram of the turn-on delay time detection circuit and the SiC MOSFET device. As shown in the figure, the steps to realize the turn-on delay time detection of SiCMOSFET are as follows:

[0057] Step 1: Gate voltage V gs and drain-source voltage V ds After the voltage divider circuit and the voltage follower circuit, they enter the voltage comparator and the reference voltage V TH1 and reference voltage V TH2 Compare, where V TH1 Set to gate threshold voltage V th 10% and V TH2 Set to bus voltage V DC 90%;

[0058] Step 2: Gate voltage V gs With reference voltage V TH1 Compare, when V gs Exceed V TH1 , the voltage comparator outputs the first step signal, indicating that the SiC MOSFET starts to turn on; the drain-source voltage V ds With reference voltage V TH2 Compare, when V ds Drop to V TH2 When the voltage drops below 0.1, another voltage comparator outputs a second step signal, indicating that the drain-source voltage of the SiC MOSFET has dropped to a certain critical level.

[0059] Step 3: The two voltage step signals output by the two voltage comparators are subjected to logic operation through the AND gate. When the two voltage step signals meet the conditions at the same time (i.e., appear at the same time), the AND gate outputs a high-level signal. The width of this high-level signal is exactly equal to the turn-on delay time of the SiC MOSFET. That is, a single pulse signal with a width equal to the turn-on delay time length of the SiC MOSFET device is obtained within the switching cycle of the SiC MOSFET device.

[0060] Step 4: Read the single pulse signal in real time. The width of this pulse signal is the turn-on delay time of the SiC MOSFET in the current switching cycle.

[0061] The signal flow chart and output waveform of the turn-on delay time detection circuit of the SiC MOSFET device in the above steps are as follows: Figure 4 shown.

[0062] The above step 4 specifically connects the pulse signal to the pulse time detection I / O port of an oscilloscope or a microcontroller (MCU) to obtain the turn-on delay time of the SiC MOSFET in the current switching cycle.

[0063] By performing double pulse tests on SiC MOSFET devices with different bonding wire aging states, and collecting and analyzing the test data, a turn-on delay time t don The bonding wire aging assessment model is as follows:

[0064] Step 1. Select a SiC MOSFET device: Select a SiC MOSFET device whose bonding wire status ranges from a healthy state to an aging state close to failure;

[0065] Step 2. Determine the test conditions: Select one or more test conditions based on the actual operating parameters of the SiC MOSFET device (such as voltage, current, temperature, etc.);

[0066] Step 3. Double pulse test: According to the requirements of the double pulse test, the SiC MOSFET device is connected and a double pulse signal is applied for testing;

[0067] Step 4. Data processing and analysis: Process and analyze the data of the double pulse test to extract the turn-on delay time t of the SiC MOSFET under the current bonding wire aging state and operating parameters. don ;

[0068] Step 5. Test condition loop: Check whether the test conditions of all working parameters are completed. If not, return to step 2; otherwise, go to step 6;

[0069] Step 6. Device test cycle: Check whether the test of all SiC MOSFET devices is completed. If not, return to step 1, otherwise, go to step 7;

[0070] Step 7. Construct an aging model: All the above data are sorted and analyzed according to different operating parameters and different bonding wire aging degrees. Using the linear regression method, a SiC MOSFET device bonding wire aging model based on the turn-on delay time considering different operating parameters is constructed.

[0071] The online real-time evaluation method of SiC MOSFET device bonding wire aging state includes the following steps:

[0072] Step 1: System connection and setup

[0073] Step 1.1: Connect the SiC MOSFET device to the detection circuit: Connect the corresponding terminals of the SiC MOSFET device to the corresponding input terminals of the turn-on delay time detection circuit to capture the voltage or current changes of the SiC MOSFET device at the moment of turn-on.

[0074] Step 1.2 Set the reference voltage: Set the reference voltage V TH1 and V TH2 . V TH1 Usually set to the gate threshold voltage V th 10% of the gate voltage, used to detect when the gate voltage starts to rise; V TH2 Then set the bus voltage V DC 90% is used to determine whether the SiC MOSFET device has been fully turned on.

[0075] Step 1.3: Connect the detection circuit to the MCU / oscilloscope: Connect the OUT terminal of the turn-on delay time detection circuit to the oscilloscope or the I / O port of the MCU with pulse time detection function to capture and record the turn-on delay time pulse signal in real time.

[0076] Step 1.4 MCU / oscilloscope connected to the host computer: Connect the communication port of the MCU or oscilloscope to the host computer so that the detected data can be transmitted to the host computer in real time for analysis and processing.

[0077] Step 2: Running the SiC MOSFET Device

[0078] Start up and run the SiC MOSFET device in its actual operating environment to collect data under real-world conditions.

[0079] Step 3: Record the current operating parameters

[0080] Real-time recording of the operating parameters of the SiC MOSFET device during operation, such as voltage, current, temperature, etc. These parameters have a certain impact on the turn-on delay time, so they need to be recorded for subsequent analysis.

[0081] Step 4: Evaluate bond wire aging

[0082] According to the real-time recorded operating parameters and the turn-on delay time measured by the turn-on delay time detection circuit board, the bond wire aging state of the SiC MOSFET device is calculated using the previously established bond wire aging model based on the turn-on delay time.

[0083] The evaluation results are displayed on the host computer for the operator’s reference. In this way, the operator can take timely measures based on the evaluation results, such as replacing aging SiC MOSFET devices, to ensure the stable operation of the system.

Claims

1. An online evaluation method for bonding wire aging status based on SiC MOSFET dynamic characteristic parameters, characterized in that: The following steps are involved: Step 1. Measure the turn-on delay time of SiC MOSFET: The turn-on delay time detection circuit is used to capture and record the turn-on delay time t of SiC MOSFET in real time during operation. don ; Among them, the opening delay time t don is the gate voltage V gs The time required for the drain current Id to rise from 0 to 10% of the steady-state current IL; Step 2. Run the SiC MOSFET device to obtain the actual operating parameters of the SiC MOSFET device; Step 3. Based on the turn-on delay time t of SiC MOSFET don The actual operating parameters of SiC MOSFET devices are combined with the bond wire aging evaluation model based on turn-on delay time to evaluate the bond wire aging status of SiC MOSFET.

2. The online evaluation method for bonding wire aging status based on SiC MOSFET dynamic characteristic parameters according to claim 1, characterized in that: The step 1. of opening the delay time detection circuit comprises: A voltage divider circuit is used to control the input voltage within the power supply voltage of the voltage follower circuit and output it to the voltage follower circuit respectively; The voltage follower circuit is used to buffer the signal transmission between the front-stage voltage divider circuit and the rear-stage voltage comparison circuit, isolate the mutual influence between the front-stage and rear-stage circuits, reduce the interference to the voltage signal, and output it to the voltage comparison circuit; A voltage comparison circuit is used to compare the output of the voltage follower circuit with a preset reference voltage V TH1 and V TH2 For comparison, the reference voltage V TH1 Set to gate threshold voltage V th 10% of the reference voltage V TH2 Set to bus voltage V DC 90% of the value, and output the comparison result to the pulse synthesis circuit; A pulse synthesis circuit is used to synthesize a pulse signal according to the output of the voltage comparison circuit, and the width of the pulse signal is equal to the turn-on delay time t of the SiC MOSFET. don .

3. The online evaluation method for bonding wire aging status based on SiC MOSFET dynamic characteristic parameters according to claim 2, characterized in that: The voltage comparison circuit includes at least two voltage comparators, which are respectively used to compare the gate voltage V gs With reference voltage V TH2 and the drain-source voltage V ds With reference voltage V TH2 , and output the comparison result.

4. The online evaluation method for bonding wire aging status based on SiC MOSFET dynamic characteristic parameters according to claim 2, characterized in that: The pulse synthesis circuit includes a logic gate circuit, which is used to synthesize a pulse signal that meets the conditions according to the output of the voltage comparison circuit.

5. The online evaluation method for bonding wire aging status based on SiC MOSFET dynamic characteristic parameters according to any one of claims 1 to 4, characterized in that: The opening delay time detection circuit V gs The V terminal and the corresponding GND terminal are connected to the gate terminal and Kelvin terminal of the SiC MOSFET device respectively; ds The terminal and the corresponding GND terminal are connected to the drain terminal and source terminal of the SiCMOSFET respectively; V TH1 Terminals and V TH2 The terminals are used to set the reference voltage V TH1 and V TH2 .

6. The online evaluation method for bonding wire aging status based on SiC MOSFET dynamic characteristic parameters according to claim 5, characterized in that: The output of the opening delay time detection circuit is connected to the I / O port of an oscilloscope or an MCU with a pulse time detection function, and the communication port of the MCU or the oscilloscope is connected to a host computer to transmit detection data in real time.

7. The online evaluation method for bonding wire aging status based on SiC MOSFET dynamic characteristic parameters according to claim 1, characterized in that: The steps of establishing the bonding wire aging assessment model based on the opening delay time in step 3 include: Step 3.1 Select SiC MOSFET devices with different bond wire aging states; Step 3.2: Determine the test conditions, including voltage, current, and temperature parameters; Step 3.3: Perform a double pulse test on the SiC MOSFET device and collect turn-on delay time data; Step 3.4 processes and analyzes the collected data to extract the relationship between the turn-on delay time and the bonding wire aging state; Step 3.5 constructs a SiC MOSFET device bond wire aging model based on turn-on delay time considering different operating parameters based on statistical methods.

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