IGBT (Insulated Gate Bipolar Translator) device safe working area degradation characterization method considering aging influence

Abstract

The invention relates to an IGBT (Insulated Gate Bipolar Translator) device safe working area degradation characterization method considering aging influence, and belongs to the technical field of semiconductors. A characterization model of the method comprises: a two-dimensional initial SOA (including a maximum current boundary, a maximum power loss boundary and a maximum voltage boundary); a junction-to-case thermal resistance degradation model with variable junction temperature fluctuation; the invention discloses a dynamic SOA boundary degradation model. The method comprises the following characterization steps: defining a two-dimensional initial SOA of a device according to a data manual, obtaining thermal resistance degradation model parameters under different junction temperature fluctuation power cycle conditions through experimental fitting, and establishing a dynamic SOA boundary degradation model under variable junction temperature fluctuation according to a thermal resistance degradation model. According to the invention, the influence of load and environment temperature working condition change on the boundary contraction of the safe working area of the device can be observed, and the degradation contraction effect of device aging on the safe working area is effectively represented.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors and relates to a method for characterizing the degradation of a safe operating area of ​​an IGBT device taking aging effects into consideration. Background Art

[0002] As a core component of modern power electronic equipment, insulated gate bipolar transistor (IGBT) is widely used in the generation, transmission, distribution and consumption of new power systems with high proportion of new energy and high proportion of power electronics. However, historical data and research show that power semiconductor devices are the most vulnerable components in power electronic equipment. The low reliability of equipment caused by long-term operation has become one of the key bottlenecks restricting the development of new power systems. It is urgent to quantitatively evaluate its long-term safe operation capability to improve the reliability of the system. SOA is a well-known device parameter that represents the ability of the device to ride through overvoltage and overcurrent conditions. When designing power converters, we assume a fixed SOA value, and the overall reliability of the circuit simply becomes the probability of abnormal conditions occurring and the probability of failure of other devices. Numerous experimental results show that the SOA of any semiconductor device is age-related rather than static. This age-related SOA is a potential cause of device aging failure, especially when the device is subjected to unexpected overvoltage / current. When the device ages, it will be affected by the reduction of SOA, which will reduce the mean time between failures (MTTF) of the device and the reliability of the overall system. Therefore, by understanding the aging level, the dynamic or real-time SOA of the device can be estimated, thereby determining the overall reliability of the circuit. By doing so, planned maintenance can be performed more accurately, thereby reducing unnecessary downtime.

[0003] At present, IGBT SOA is mostly based on electrical characteristics such as current and voltage in the steady-state working area. Although the device manual gives a simple thermal resistance parameter, it is difficult to accurately describe the changes in electrothermal parameters when the electrical system changes. Considering the changes in the electrothermal parameters of the device material with the degree of device aging, SOA can be defined more accurately. By collecting the life cycle characteristic data of IGBT devices, establishing a dynamic model of the safe working area, constructing the dynamic SOA boundary condition attenuation characteristics, and analyzing the relationship between the degradation of IGBT electrical characteristic parameters and SOA in different life cycles, the health status of power devices can be judged more accurately to ensure the safe and stable operation of devices and power equipment. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for characterizing the degradation of the safe operating area of ​​an IGBT device taking into account the influence of aging. By combining the selection of device aging characteristic parameters, mathematical model construction and experimental verification, the dynamic SOA definition of the IGBT device taking into account the influence of aging is realized. The redefined SOA can more accurately describe the protection range of the IGBT.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for characterizing the degradation of the safe operating area of ​​an IGBT device considering the influence of aging, the method comprising the following steps:

[0007] Define the two-dimensional initial SOA of the IGBT module, and describe the maximum current boundary, maximum power loss boundary, and maximum voltage boundary of the SOA;

[0008] A junction-to-case thermal resistance degradation model was established, and the thermal resistance degradation parameters were obtained through experimental fitting.

[0009] Analyze the thermal resistance degradation model under different junction temperature fluctuation power cycle conditions and obtain the thermal resistance change results;

[0010] The SOA boundary degradation model is established to observe the impact of the device's safe operating area boundary shrinkage on changes in load and ambient temperature, and to analyze the influencing factors of the dynamic safe operating area.

[0011] Furthermore, the maximum current limit I CR(max) Defined as the maximum collector conduction current I C(max) 2 times;

[0012] The maximum power loss is limited by the junction temperature not exceeding the maximum junction temperature T j(max) The maximum voltage boundary is determined by the IGBT module breakdown voltage V CES(BR) Decide.

[0013] Furthermore, the junction-to-case thermal resistance degradation model is:

[0014] R th =R th-initial ·[1+A1·(N) m ]

[0015] Where R th-initial is the initial junction-to-case thermal resistance, N is the number of power cycles, and A1 and m are thermal resistance degradation parameters.

[0016] Furthermore, the number of the different junction temperature fluctuation power cycle conditions is three groups.

[0017] Furthermore, the boundary of the safe operating area of ​​the device shrinks with the degradation of the power cycle number N as follows:

[0018]

[0019] log(I C )+log(V CE )=log(T j(max) -T c )

[0020] -log(Z th-initial )-log(1+A1·(N) m )

[0021] Where T c is the case temperature, V CE(sat) is the collector saturation voltage drop, I C is the collector current, V CE is the collector-emitter voltage, Z th-initial is the initial junction thermal impedance.

[0022] The beneficial effects of the present invention are:

[0023] (1) The present invention considers the impact of device SOA shrinkage caused by the degradation of device electrical and thermal parameters during long-term service of IGBT devices. A mathematical model of the IGBT device's dynamic shrinkage safe operating area is established to characterize the SOA shrinkage process of the IGBT module during aging and describe the impact of device aging on its safety.

[0024] (2) The present invention establishes a thermal simulation model for the IGBT module. The simulation boundary conditions and initial conditions are set according to the actual operating conditions of the device, three different operating conditions of junction temperature fluctuation are selected for simulation, and the thermal resistance degradation model under different junction temperature fluctuation conditions is established.

[0025] (3) The present invention considers the influence of different junction temperature fluctuations on the thermal resistance degradation of the device, establishes a corresponding dynamic SOA model, and compares the dynamic shrinkage speed of the device SOA boundary under different junction temperature fluctuations, which can provide guidance for the SOA characterization of devices under different working conditions and different aging lifespans.

[0026] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0028] Figure 1 It is the principle diagram of the present invention;

[0029] Figure 2 is the two-dimensional initial SOA of the IGBT;

[0030] Figure 3 = ΔT j =SOA dynamic shrinkage process under 72.8℃ junction temperature fluctuation;

[0031] Figure 4 = ΔT j =SOA dynamic shrinkage process under 80.5℃ junction temperature fluctuation;

[0032] Figure 5 = ΔT j =SOA dynamic shrinkage process under 93.7℃ junction temperature fluctuation. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0034] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] See also Figure 1 The present invention is a method for redefining the dynamic SOA of an IGBT device taking into account the influence of aging. The method comprises the following steps:

[0037] S1: Define the two-dimensional initial SOA of the IGBT module. The two-dimensional initial SOA describes the ability of the IGBT module to withstand voltage and current at the same time. Based on device characteristic tests or data sheet parameters, describe the maximum current boundary, maximum power loss boundary, and maximum voltage boundary of the SOA.

[0038] Maximum current limit I CR(max) Usually defined as I C(max) 2 times. C(max) Limited by the current capacity and heat dissipation, if the collector current exceeds I CR(max) , there will be a risk of overvoltage and overheating, causing the chip to desaturate prematurely; in addition, the aluminum metallization layer on the surface of the IGBT chip may also be damaged, causing the chip to age and fail prematurely.

[0039] The expression is as follows:

[0040]

[0041] Among them I chip is the maximum on-state current constrained by the chip and bonding wires; T j(max) is the maximum junction temperature; V CE(sat) is related to the junction temperature T j The associated saturation voltage; R th(jc) is the junction-to-case thermal resistance.

[0042] The limiting condition of the maximum power loss boundary is that the IGBT junction temperature cannot exceed its allowable upper limit T j(max) , otherwise the device will overheat and collapse and lose its blocking ability. The formula is described as follows:

[0043] T j(max) -T c =P tot(max) ·Z th(jc)

[0044] Z th(jc) =D·R th(jc) +(1-D)·Z thp(jc) (t p )

[0045]

[0046] Where Z th(jc) is the junction-to-case transient thermal impedance; Z thp(jc) is the single pulse transient thermal impedance; U DC is the DC bus voltage; U DC(on) is the bus voltage when the IGBT is turned on; U DC(off) is the bus voltage when the IGBT is turned off.

[0047] Because P tot(max)It can be described as V CE and I C Therefore, the maximum power loss boundary can be described in logarithmic coordinates as follows.

[0048] log(I C )+log(V CE )=log(T j(max) -T c )-log(Z th(jc) )

[0049] The maximum voltage limit is given by the IGBT module breakdown voltage V given in the data sheet. CES(BR) Decision, V CES(BR) It is usually in the order of several hundred volts and is almost unaffected by temperature. CES(BR) This will cause the chip to break down and fail instantly.

[0050] S2: Establish the junction-case thermal resistance degradation model. From the above initial SOA definition formula, it can be seen that the maximum current boundary and the maximum power loss boundary are both affected by the junction-case thermal resistance R th(jc) The research shows that thermal resistance is a characteristic quantity that can be used to characterize the health status of power modules. The junction-case thermal resistance degradation model is established as follows:

[0051] R th =R th-initial ·[1+A1·(N) m ]

[0052] Where R th-initial is the initial junction-to-case thermal resistance, N is the number of power cycles, and A1 and m are thermal resistance degradation parameters, which must be fitted through experiments.

[0053] S3: Analyze the thermal resistance degradation model under different junction temperature fluctuation power cycle conditions. Using the model form shown in the above formula, select three groups of thermal resistance change results under different junction temperature fluctuation conditions for data fitting.

[0054] S4: Establish SOA boundary degradation model. As the number of power cycles N increases, R th(jc) Gradually increase, the P in SOA tot(max) Boundary and I CR(max) The degradation shrinkage of the safe operating area boundary with the number of power cycles N is expressed as follows:

[0055]

[0056] log(I C )+log(V CE )=log(T j(max) -T c )

[0057] -log(Z th-initial )-log(1+A1·(N) m )

[0058] Since load and ambient temperature will change greatly during long-term service, ΔT j Therefore, N dimensions are added to the initial SOA to establish the device dynamic safe operating area considering the impact of aging. At the same time, the impact of the shrinkage of the device's safe operating area boundary on changes in operating conditions such as load and ambient temperature is observed, and the influencing factors of the dynamic safe operating area are analyzed.

[0059] The initial SOA of the IGBT defined by technology S1 is as follows Figure 2 The thermal resistance degradation experiment under different junction temperature fluctuation conditions shows that for the power device module, the thermal resistance obtained through the test results shows a nonlinear increasing trend. The thermal resistance change results under different junction temperature fluctuation conditions are fitted, and the fitting parameters of the thermal resistance degradation model are shown in Table 1.

[0060] Table 1

[0061] Module Number <![CDATA[ΔT j ]]> <![CDATA[T jm ]]> <![CDATA[A1]]> m 1 72.8℃ 65.5℃ <![CDATA[4.556×10 -101 ]]> 20.8485 2 80.5℃ 68.8℃ <![CDATA[6.1435×10 -100 ]]> 20.8626 3 93.7℃ 75.6℃ <![CDATA[4.0785×10 -105 ]]> 22.1769

[0062] The thermal resistance change results under three different conditions were selected, and the data were fitted using the junction-case thermal resistance degradation formula. The fitting results were brought into the dynamic SOA mathematical model. The dynamic shrinkage process of the device SOA under different junction temperature fluctuations under the same cycle aging number was extracted in the logarithmic coordinate system. Figure 3 to Figure 5 shown.

[0063] Depend on Figure 3 It can be seen that R th(jc) As the number of cycles N increases, the device degrades, resulting in a shrinkage in the safe operating area of ​​the device. Under the three junction temperature fluctuation conditions set to simulate different working conditions, under the same number of power cycles, the device with the largest junction temperature fluctuation has more obvious thermal resistance degradation and more obvious shrinkage of the device SOA boundary. This shows that different junction temperature fluctuations caused by changes in working conditions such as load and ambient temperature are important factors affecting the shrinkage of the device SOA boundary.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for characterizing the degradation of the safe operating area of ​​an IGBT device considering the influence of aging, characterized in that: The method comprises the following steps: Define the two-dimensional initial SOA of the IGBT module, and describe the maximum current boundary, maximum power loss boundary, and maximum voltage boundary of the SOA; A junction-to-case thermal resistance degradation model was established, and the thermal resistance degradation parameters were obtained through experimental fitting. Analyze the thermal resistance degradation model under different junction temperature fluctuation power cycle conditions and obtain the thermal resistance change results; The SOA boundary degradation model is established to observe the impact of the device's safe operating area boundary shrinkage on changes in load and ambient temperature, and to analyze the influencing factors of the dynamic safe operating area.

2. The method for characterizing the degradation of the safe operating area of ​​an IGBT device considering the influence of aging according to claim 1, characterized in that: The maximum current limit I CR(max) Defined as the maximum collector conduction current I C(max) 2 times; The maximum power loss is limited by the junction temperature not exceeding the maximum junction temperature T j(max) The maximum voltage boundary is determined by the IGBT module breakdown voltage V CES(BR) Decide.

3. The method for characterizing the degradation of the safe operating area of ​​an IGBT device considering the influence of aging according to claim 1, characterized in that: The junction-to-case thermal resistance degradation model is: R th =R th-initial ·[1+A1·(N) m ] Where R th-initial is the initial junction-to-case thermal resistance, N is the number of power cycles, and A1 and m are thermal resistance degradation parameters.

4. The method for characterizing the degradation of the safe operating area of ​​an IGBT device considering the influence of aging according to claim 1, characterized in that: The number of the power cycle conditions with different junction temperature fluctuations is three groups.

5. The method for characterizing the degradation of the safe operating area of ​​an IGBT device considering the influence of aging according to claim 1, characterized in that: The degradation shrinkage of the boundary of the device safe operating area with the number of power cycles N is expressed as: log(I C )+log(V CE )=log(T j(max) -T c ) -log(Z th-initial )-log(1+A1·(N) m ) Where T c is the case temperature, V CE(sat) is the collector saturation voltage drop, I C is the collector current, V CE is the collector-emitter voltage, Z th-initial is the initial junction thermal impedance.

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