A SiC MOSFET device wire bonding aging monitoring circuit and online monitoring method

Abstract

This invention discloses a bonding wire aging monitoring circuit and online monitoring method for SiC MOSFET devices. The circuit includes a peak detection circuit, an analog-to-digital conversion circuit, and a control and arithmetic unit. The peak detection circuit includes a first peak detection circuit and a second peak detection circuit. The first peak detection circuit acquires the voltage between the external KS terminal and the S terminal of the device. V KS‑S The second peak detection circuit acquires the voltage across the stray inductor in the device circuit. V CIR The analog-to-digital converter (ADC) circuit converts the voltage value obtained by the peak detection circuit and transmits it to the control unit. The control unit issues instructions and calculates the data obtained by the ADC circuit. V KS‑S and V CIR The ratio of [value] to [value] is used as a characteristic indicator of bond wire fatigue aging in SiC MOSFET devices. It features ingenious design, reasonable structure, and simple features, enabling the extraction of aging characteristics and monitoring of bond wire aging during device turn-on transients.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power semiconductor device monitoring, in particular to a SiC MOSFET device bonding wire aging monitoring circuit and an online monitoring method. BACKGROUND

[0002] With the rapid development of semiconductor technology and power electronics technology, semiconductor power devices have been widely used in new energy power generation, rail transit, consumer electronics and other fields. The development trend of high frequency and high power density of power electronics technology puts forward higher requirements for semiconductor power devices, and the third generation of power semiconductor devices such as SiC has also developed rapidly. Among them, silicon carbide (SiC) MOSFET has the advantages of high temperature resistance, high voltage resistance, low loss and fast switching speed, thereby having great application prospect and industrial value. However, the packaging reliability problem of SiC MOSFET is prominent, which is caused by the electrical-thermal-mechanical stress of the device during long-term operation. Among them, the most typical aging mode is bonding wire fatigue aging. When the bonding wire is seriously fatigued and aged, the bonding wire will fall off, break and other failures, and accelerate the aging of other bonding wires, eventually leading to device failure, which seriously affects the reliability and stability of the power electronic system.

[0003] The health level of the bonding wire of the SiC MOSFET device is closely related to the bonding wire parasitic parameters and the end parasitic parameters, so by monitoring the changes of the end parasitic parameters of the SiC MOSFET device, the aging state of the device can be judged, and a reasonable power electronic device maintenance plan can be made. However, the existing technology for monitoring the fatigue aging state of the bonding wire of the SiC MOSFET is relatively complex, the cost is high, and it is necessary to stop or disassemble the SiC MOSFET device; stopping for maintenance will cause huge economic losses, and disassembly work will also cause certain damage to the SiC MOSFET device, thereby affecting the monitoring accuracy. SUMMARY

[0004] In view of the above problems existing in the prior art, the purpose of the present application is to provide a SiC MOSFET device bonding wire aging monitoring circuit and an online monitoring method, which solves the problem that the existing technology for monitoring the fatigue aging state of the bonding wire of the SiC MOSFET is relatively complex, the cost is high, and it is necessary to stop or disassemble the SiC MOSFET device.

[0005] To achieve the above purpose, the present application adopts the following technical solutions:

[0006] A SiC MOSFET device bonding wire aging monitoring circuit, characterized in that it comprises a peak detection circuit, an analog-to-digital conversion circuit and a control operation unit.

[0007] The peak detection circuit comprises a first peak detection circuit and a second peak detection circuit; the first peak detection circuit obtains the voltage V KS-S between the KS terminal and the S terminal outside the device CIR ;

[0008] The analog-digital conversion circuit is used for converting the voltage value obtained by the peak detection circuit and transmitting to the control operation unit;

[0009] The control operation unit issues an instruction and calculates the data obtained by the analog-digital conversion circuit, and takes the ratio of V KS-S and V CIR , that is, V KS-S / V CIR , as the characteristic quantity index of the SiC MOSFET device bonding wire fatigue aging.

[0010] Further, the peak detection circuit is composed of a transconductance operational amplifier, a holding capacitor and other peripheral circuits. The analog-digital conversion circuit is composed of an analog-digital conversion chip (ADC) and peripheral circuits. The control operation unit is composed of a digital signal processor (DSP) and peripheral circuits.

[0011] The application also provides a SiC MOSFET device bonding wire aging online monitoring method, which adopts the SiC MOSFET device bonding wire aging monitoring circuit.

[0012] When the device to be measured is turned on, the peak detection circuit captures and holds the peak values of the two input signals V KS-S and V CIR and sends them to the analog-digital conversion circuit for conversion; the analog-digital conversion circuit converts the input analog signal into a digital signal and returns it to the operation control unit after receiving the conversion instruction issued by the operation control unit; the control operation unit performs division operation on the converted peak value data to obtain the ratio of the peak values of V KS-S and V CIR ; the ratio is used as the bonding wire aging characteristic quantity and can be used for monitoring the bonding wire fatigue aging state;

[0013] The measured aging characteristic quantity is compared with the threshold value, and the fatigue aging degree of the SiC MOSFET device to be measured, that is, the number of bonding wire faults, can be judged.

[0014] Further, the threshold value obtaining method comprises the following steps:

[0015] First, the newly tested device is switched on, and the monitoring circuit obtains the aging characteristic value under the healthy state as the reference value; then, the bonding wires of the SiC MOSFET are cut off one by one; after cutting off each bonding wire, the device is switched on again, and the aging characteristic data after cutting off the wire is obtained through the monitoring circuit; the above operation is repeated until only the last bonding wire is left; based on the characteristic data under different bonding wire fault conditions, the threshold of the aging degree of different bonding wires is determined.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] 1、The SiC MOSFET device bonding wire aging monitoring circuit of the present application has ingenious design, reasonable design and simple structure, and can extract aging characteristic quantities during the transient process of device opening and perform bonding wire aging monitoring. The extracted aging characteristic quantities are only related to bonding wire fatigue aging, and are independent of device junction temperature, load working condition and bus working condition, thereby realizing complete decoupling of other physical quantities. In addition, the monitoring circuit does not affect the normal operation of the SiC MOSFET device and the device system. Therefore, the monitoring circuit and the monitoring method can accurately monitor the health status of the device bonding wire in real time under the condition that the device junction temperature is unknown and the circuit working condition is unknown.

[0018] 2、The SiC MOSFET device bonding wire aging online monitoring circuit of the present application can accurately monitor the aging state of the bonding wire of the SiC MOSFET device without stopping and disassembling, and can accurately determine the aging state of the device through the change of the parasitic parameter, thereby accurately determining the aging state of the bonding wire of the SiC MOSFET device, i.e. the number of bonding wire faults, thereby effectively avoiding economic losses caused by stop monitoring and damage caused by disassembling the SiC MOSFET device, reducing the operation and maintenance cost of the SiC MOSFET application equipment (such as a converter), and improving the reliability of the equipment. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a schematic diagram of the SiC MOSFET device.

[0020] Figure 2 It is a schematic diagram of the monitoring circuit of the present application.

[0021] Figure 3 It is an experimental waveform diagram of the application of the present application to a half-bridge converter.

[0022] Figure 4 It is the output waveform of the peak detection circuit and the aging characteristic quantity waveform in the present application.

[0023] Figure 1Fig. 1 is a schematic diagram of a SiC MOSFET device, wherein 1-SiC chip, 2-power source bonding wire, 3- auxiliary source bonding wire, 4-gate bonding wire. D-drain, S-power source, KS-auxiliary source, G-gate. DETAILED DESCRIPTION

[0024] The application will be further described in detail below with reference to the accompanying drawings and examples.

[0025] Reference Figure 1 Generally, the SiC MOSFET device is composed of a SiC chip, a bonding wire, a pin and an epoxy resin package. Among them, the bonding wire refers to a wire used to connect the SiC chip and the external pin of the SiC MOSFET, which is generally made of aluminum, so it is also called aluminum bonding wire. The function of the bonding wire is to connect the SiC chip and the external pin. The number of bonding wires is related to the power level, the specification of the bonding wire and the manufacturer, and is generally between 1 and 5.

[0026] When the power (source) bonding wire is severely fatigued and aged, the bonding wire will fall off, break and other failures, and accelerate the aging of other bonding wires, eventually leading to device failure, which seriously affects the reliability and stability of the power electronic system.

[0027] As Figure 2 shown, the application provides a SiC MOSFET device bonding wire aging monitoring circuit, which comprises a peak detection circuit, an analog-to-digital conversion circuit and a control operation unit.

[0028] The peak detection circuit comprises a first peak detection circuit and a second peak detection circuit; the first peak detection circuit obtains the voltage V KS-S between the KS terminal and the S terminal outside the device; and the second peak detection circuit obtains the voltage V CIR on the stray inductance in the device circuit.

[0029] The analog-to-digital conversion circuit is used to convert the voltage value obtained by the peak detection circuit and transmit it to the control operation unit.

[0030] The control operation unit issues instructions and calculates the data obtained by the analog-to-digital conversion circuit, and takes the ratio of V KS-S and V CIR , i.e. V KS-S / V CIR , as the characteristic quantity index of the SiC MOSFET device bonding wire fatigue aging.

[0031] Among them, the peak detection circuit is composed of a transconductance operational amplifier, a holding capacitor and other peripheral circuits, and can realize the peak detection function by using chips such as OPA615 and OPA860 of TI company, the peak detection circuit has high-speed signal peak capture capability, and its bandwidth is as high as 700MHz, which can quickly capture the input signal VKS-S and V CIR peak value.

[0032] The analog-digital conversion circuit is composed of an analog-digital conversion chip (ADC) and peripheral circuits, and can be realized by using an AD7367 analog-digital conversion chip of ADI Company and the like.

[0033] The control operation unit is composed of a digital signal processor (DSP) and peripheral circuits, and can be realized by using a TMS320F28335 type digital signal processor of TI Company and the like.

[0034] The SiC MOSFET bonding wire aging monitoring circuit has two signal input ports and one output port. The signal input port 1 is connected to the Kelvin source and the power source of the SiC MOSFET device, and the signal input port 2 is connected to the power source of the device and the other power terminals of the circuit; one output port is sent by the operation control unit, which is the bonding wire aging characteristic quantity.

[0035] Referring to Figure 2 , the input signal 1 of the monitoring circuit is the voltage V KS-S induced by the current change rate in the opening process of the SiC MOSFET device on the parasitic inductance between the Kelvin source and the power source of the device. S_BW The parasitic inductance is composed of the bonding wire inductance L S_L and the lead inductance L CIR The input signal 2 is the voltage V CIR induced by the current change rate in the opening process on the parasitic inductance between the power source of the device and the other power terminals of the circuit.

[0036] The characteristic quantity of the SiC MOSFET device bonding wire fatigue aging obtained by the application is the ratio of the peak value of V KS-S (input signal 1) to the peak value of V CIR (input signal 2). The expression of the characteristic quantity only contains the bonding wire inductance L S_BW , the lead inductance L S_L and the circuit stray inductance L CIR , and does not contain the current change rate, thereby eliminating the influence of the current change rate. The bonding wire aging characteristic quantity is only related to the bonding wire fatigue aging, and is irrelevant to external factors such as junction temperature, load current and bus voltage.

[0037] The new device to be tested is first detected by using the circuit, the monitoring circuit is implemented, and the aging characteristic quantity value in the healthy state is obtained as a reference value; when the device is running in the actual device, the aging characteristic quantity in the healthy state is first measured as a reference value. During the operation of the device, the characteristic quantity is detected regularly according to the needs, and compared with the set threshold value, so as to judge the fatigue aging degree of the bonding wire of the SiC MOSFET device, that is, the number of bonding wire faults.

[0038] Further, the application also provides a SiC MOSFET device wire bonding aging on-line monitoring method, which adopts the wire bonding aging monitoring circuit of the application and comprises the following steps:

[0039] When the device to be measured is turned on, the peak detection circuit captures and holds the peak values of the two input signals V KS-S and V CIR and sends them to the analog-to-digital conversion circuit for conversion; the analog-to-digital conversion circuit converts the input analog signals into digital signals and returns them to the control operation unit after receiving the conversion instruction from the operation control unit; the control operation unit performs division operation on the converted peak value data to obtain the ratio of the peak values of V KS-S and V CIR , and takes the ratio as the wire bonding aging characteristic quantity.

[0040] The control operation unit can judge the wire bonding aging state of the SiC MOSFET device to be measured according to the actual value of the characteristic quantity and the set threshold value.

[0041] The characteristic quantity threshold value is obtained by off-line sample calibration, and the specific steps include:

[0042] A brand new device to be measured is subjected to switching test, the monitoring circuit is implemented, and the aging characteristic quantity value in the healthy state is obtained as the reference value; then, the wire bonds of the SiC MOSFET are cut one by one; after each wire bond is cut, the device is subjected to switching test again, and the aging characteristic quantity data after the wire cutting is obtained through the monitoring circuit; the above operation is repeated until only the last wire bond is left.

[0043] Based on the characteristic quantity data under different wire bonding fault conditions, the threshold values of different wire bonding aging degrees are determined.

[0044] The applicant found that during the on process of the device to be measured, the current change rate di / dt would induce voltages on the wire bonding inductance L S_BW , the lead inductance L S_L and the circuit stray inductance L CIR , and the specific expression is

[0045]

[0046]

[0047] Therefore, V KS-S is equal to the sum of the wire bonding inductance L S_BW and the lead inductance L S_L multiplied by the current change rate, and V CIR is equal to the circuit stray inductance L CIR multiplied by the current change rate.

[0048] As Figure 1 For an embodiment, the measured SiC MOSFET device, the total inductance of the bonding wire is equal to the inductance value of 4 bonding wires in parallel. When the bonding wire breaks (or artificially cuts the bonding wire), the number of effective bonding wires decreases, causing the bonding wire inductance to change, thereby causing V KS-S to change. Therefore, the degree of bonding wire aging refers to the number of bonding wire failures or the remaining number of bonding wires. When one bonding wire fails, the characteristic quantity data will increase compared to when there is no bonding wire failure; when two bonding wires fail, the characteristic quantity data will continue to increase, and so on. Therefore, when the bonding wire fails, how much (percentage) the characteristic quantity data specifically increases needs to be obtained through testing.

[0049] For any SiC MOSFET device, as long as the number of bonding wires is greater than or equal to 2, the monitoring circuit and method can be used for monitoring.

[0050] Referring to Figure 3 , the application is applied to the experimental waveform diagram in the half-bridge circuit (inductive load), wherein V KS-S is the voltage induced on the inductance between the Kelvin source and the power source, V OUT is the output waveform of the peak detection circuit in the monitoring circuit. As can be seen from the figure, the peak detection circuit can quickly capture the peak of V KS-S and maintain it.

[0051] Referring to Figure 4 , the waveform of the two input signals V KS-S and V CIR of the monitoring circuit of the application after peak detection and the output characteristic quantity waveform. As can be seen from Figure 3 , the peaks of the two input signals decrease over time after peak detection, which is due to the discharge of the holding capacitor of the peak detection circuit; however, the ratio of the two, i.e. the proposed bonding wire aging characteristic quantity value remains constant and does not change over time. Therefore, the proposed aging characteristic quantity and aging monitoring result are not affected by the analog-to-digital conversion time.

[0052] When the device is running in an actual device, first measure the aging characteristic quantity in a healthy state as a baseline value. The SiC MOSFET device is subjected to an opening process to expose the bonding wires, and the bonding wire breakage and shedding failure caused by bonding wire fatigue aging is simulated by artificially cutting the bonding wire. During the operation of the device, the characteristic quantity is detected periodically as needed and compared with the set threshold value, thereby determining the degree of bonding wire fatigue aging of the SiC MOSFET device, i.e. the number of bonding wire failures.

[0053] The application proposes that the bonding wire fatigue aging characteristic quantity is V KS-SThe peak value of (input signal 1) and V CIR The peak ratio of (input signal 2) is defined. The expression for the proposed characteristic quantity only includes the bond wire inductance L. S_BW Lead inductance L S_L and stray inductance L of the circuit CIR The proposed bonding wire aging characteristic is independent of the rate of change of current, thus eliminating its influence. The proposed characteristic is only related to bonding wire fatigue aging and is unrelated to external factors such as junction temperature, load current, and bus voltage. Therefore, the method of this invention enables accurate monitoring of the bonding wire aging status of SiC MOSFET devices without shutdown or disassembly, accurately identifying the number of faulty bonding wires and thus accurately determining the bonding wire fatigue aging status of SiC MOSFET devices. This effectively avoids economic losses caused by downtime monitoring and damage to SiC MOSFET devices during disassembly, reducing the operation and maintenance costs of SiC MOSFET application equipment (such as converters) and improving equipment reliability.

[0054] The characteristic parameters proposed in this invention are only related to bond wire fatigue aging and are not affected by parameters such as junction temperature, load current, and bus voltage. Therefore, the method proposed in this invention can be carried out online without obtaining information such as junction temperature, and the monitoring results have good accuracy. This solves the problem that most silicon carbide MOSFET bond wire aging monitoring methods are difficult to implement online, effectively avoiding economic losses caused by downtime monitoring.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A fatigue aging monitoring circuit for bond wires of a SiC MOSFET device, characterized in that, It includes a peak detection circuit, an analog-to-digital conversion circuit, and a control and arithmetic unit; The peak detection circuit includes a first peak detection circuit and a second peak detection circuit; the first peak detection circuit acquires the voltage between the external KS terminal and the S terminal of the device. V KS-S The second peak detection circuit acquires the voltage across the stray inductor in the device circuit. V CIR ; The analog-to-digital converter circuit is used to convert the voltage value obtained by the peak detection circuit and transmit it to the control and arithmetic unit; The control unit issues instructions and performs calculations on the data acquired by the analog-to-digital converter circuit. V KS-S and V CIR The ratio is V KS-S / V CIR , as a characteristic indicator of bonding wire fatigue aging in SiC MOSFET devices.

2. The SiC MOSFET device bond wire fatigue aging monitoring circuit according to claim 1, characterized in that, The peak detection circuit consists of a transconductance operational amplifier, a holding capacitor, and other peripheral circuits.

3. The SiC MOSFET device bond wire fatigue aging monitoring circuit according to claim 1, characterized in that, The analog-to-digital conversion circuit consists of an analog-to-digital converter chip (ADC) and peripheral circuits.

4. The SiC MOSFET device bond wire fatigue aging monitoring circuit according to claim 1, characterized in that, The control and operation unit consists of a digital signal processor (DSP) and peripheral circuits.

5. The SiC MOSFET device bond wire fatigue aging monitoring circuit according to claim 1, characterized in that, The peak detection circuit uses a transconductance operational amplifier, model OPA615, from TI, with a bandwidth of up to 700MHz, to quickly capture the input signal. V KS-S and V CIR The peak value.

6. A method for online monitoring of fatigue aging of SiC MOSFET bond wires, characterized in that, The bonding wire aging monitoring circuit of any SiC MOSFET device according to claims 1 to 5 is adopted; the monitoring method is as follows: When the device under test is turned on, the peak detection circuit captures and holds the two input signals. V KS-S and V CIR The peak value is then sent to the analog-to-digital converter circuit for conversion. After receiving a conversion command from the arithmetic control unit, the analog-to-digital converter (ADC) converts the input analog signal into a digital signal and returns it to the arithmetic control unit. The arithmetic unit then performs a division operation on the converted peak data to obtain... V KS-S and V CIR The ratio of the peak values; this ratio serves as a characteristic quantity of bond wire aging and is used to monitor the fatigue aging state of the bond wire. The measured aging characteristic quantity is compared with the threshold to determine the degree of bonding wire fatigue aging of the SiC MOSFET device under test, i.e. the number of bonding wire faults.

7. The online monitoring method for SiC MOSFET gate aging according to claim 6, characterized in that, The threshold acquisition method includes the following steps: First, a brand-new device under test is subjected to a switching test, and the aging characteristic value under healthy condition is obtained by the monitoring circuit as a reference value. Then, the bonding wires of the SiC MOSFET are cut one by one. After each bonding wire is cut, the device is subjected to a switching test again, and the aging characteristic data after the wire is cut is obtained by the monitoring circuit. The above operation is repeated until only the last bonding wire is left. Thresholds for different bond wire aging degrees are selected based on characteristic data under different bond wire failure conditions.

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