Power module with integrated circuit for crack detection

Abstract

Power module (10) comprising a semiconductor component (1), in particular a power semiconductor, which is arranged between a first circuit carrier (2) and a second circuit carrier (3) and is contacted therewith, wherein the arrangement is at least partially enclosed with potting compound.

Description

Technical area

[0001] The invention relates to a power module with an integrated circuit for detecting crack formation, particularly in the potting compound of the module or at an interface between the potting compound and an electrically conductive layer. State of the art

[0002] Power semiconductors such as silicon carbide (SiC)-based power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and components comprising them are well known.

[0003] Also known from the prior art are power modules in which a semiconductor component, in particular a power semiconductor such as a SiC MOSFET, is contacted with a circuit carrier such as an AMB circuit carrier (AMB = Active Metal Brazed) and / or a DBC circuit carrier (DBC = Direct Bond Copper). The power semiconductor can also be arranged between an AMB circuit carrier and a DBC circuit carrier, with the individual components and the spaces formed therein being enclosed or filled by means of a potting compound. Such power modules are used in particular as a component of an inverter for a vehicle, in particular an electric vehicle or motor vehicle.

[0004] During the application and operation of such power modules, delaminations may occur, particularly in the area of ​​the power semiconductor. These can lead to leakage currents, electrochemical migration, and even electrical flashover, particularly between the source and drain potentials. Such delaminations are usually difficult to detect, occur with increased probability during operation, and are therefore considered critical to function. Disclosure of the invention

[0005] The invention relates to a power module comprising a semiconductor component, in particular a power semiconductor, which is arranged between a first circuit carrier and a second circuit carrier and is contacted therewith, wherein these are at least partially enclosed with potting compound, wherein the power module has a detection unit which is designed to monitor a contact region between the potting compound and at least one conductive layer of a circuit carrier lying against it for crack formation.

[0006] The power module or device according to the invention enables monitoring for crack formation between a potting compound and the conductive layer adjacent to it, thus enabling the detection of crack formation or delamination between the potting compound and the conductive layer in situ in the power module. This enables safe operation of the power module and, in particular, the early detection of crack formation and a resulting failure function. This can increase the operational reliability of the power module and a component containing it, such as an inverter.

[0007] The detection unit is preferably designed to detect crack formation in the contact region by means of impedance detection or impedance monitoring, in particular capacitively. The detection unit is advantageously designed to determine a change in impedance or capacitance between different potentials on the power module in order to be able to use the detected values ​​to infer crack formation or delamination of the encapsulating compound from the adjacent conductive layers and / or the power semiconductor.

[0008] The basis for this is the finding that a capacitor with electrodes at different electrical potentials, which are insulated from each other by an intermediate dielectric such as a potting compound, exhibits a capacitance that is lower in the event of delamination or cracking between the layers than without delamination. By detecting a change in capacitance, it is possible to infer cracking or delamination of the laminated layers.

[0009] The detection unit preferably comprises at least a first sensor electrode and an opposite second sensor electrode, which sandwich the potting compound between them. The first sensor electrode and the second sensor electrode are advantageously formed by opposing conductive layers or sections of the first and second circuit carriers. The power module thus advantageously comprises a laminated arrangement of a first conductive layer of the first circuit carrier and an oppositely disposed conductive layer of the second circuit carrier, with a potting compound arranged therebetween.

[0010] The detection unit is further advantageously configured to detect a capacitance between the first circuit carrier and the second circuit carrier via a top-side drain potential of the first circuit carrier and a rear-side source potential of the second circuit carrier. This enables detection of the capacitance at the power module and thus the detection according to the invention in a simple manner and, in particular, with minimal modification to a power module known from the prior art.

[0011] In a preferred embodiment, the first circuit carrier is designed as an AMB circuit carrier (AMB = Active Metal Brazed). The second circuit carrier is preferably designed as a DBC circuit carrier (Direct Bond Copper).

[0012] The detection unit is preferably embodied as an application-specific integrated circuit (ASIC). The application-specific circuit can be embodied analogously to the circuit disclosed in DE 10 2018 210 613 A1. The ASIC is preferably arranged or formed on the second circuit carrier. In particular, the detection unit can be arranged on the top side of the second circuit carrier, advantageously a DBC substrate, and dielectrically connected to it.

[0013] In a preferred embodiment, the detection unit is additionally configured to detect a break in the semiconductor component of the power module. This is particularly true because, in this case, the electric field between the source and drain potential also changes, which can be detected by the detection unit according to the invention.

[0014] In a preferred embodiment, the power module comprises at least one temperature detection unit, in particular an NTC resistor, wherein the detection unit is designed to evaluate a respective temperature for monitoring for crack formation.

[0015] The detection unit can be configured to measure the capacitance at certain, predefined temperatures and to consider this measurement data for the detection of crack formation or delamination. Since the capacitance is temperature-dependent, this can achieve optimized detection of crack formation or delamination in the module.

[0016] In a preferred embodiment, the detection unit comprises a processing unit configured to generate a crack detection signal for detecting a crack or delamination in the contact region and transmit it to the sensor electrodes, and to detect an impedance or capacitance in the contact region and, depending on the impedance or capacitance, and preferably a detected temperature signal, to generate and output a crack signal representing a crack. The crack detection signal of the detection unit can be output continuously, at predefined time intervals, and / or under predefined operating parameters of the power module.

[0017] The crack signal emitted when a crack or delamination is detected can be passed on to a control unit connected to the power module, for example the control unit of a vehicle.

[0018] In a further aspect, the invention relates to a control unit for a motor vehicle having a power module as described above. The control unit is advantageously connected to the power module and in particular to the detection unit of the power module, such that a crack signal provided by the detection unit, which can be used to infer crack formation or delamination in the power module, can be received by the control unit. The control unit is further advantageously designed to make a change in the control of the motor vehicle, in particular to initiate a safe state, depending on the information provided and in particular depending on a crack signal provided by the detection unit.

[0019] To avoid repetition, with regard to the further features of the control unit according to the invention, reference should be made to the previously described features of the power module according to the invention, which should be considered as equally disclosed and claimable for the control unit according to the invention and vice versa.

[0020] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings. Short description of the drawings Fig. 1a shows a top view of a power module from the prior art, with the potting compound hidden for clarity purposes, Fig. 1b shows a section AA through the power module of the prior art according to Fig. 1a with a sandwich-like structure, Fig. 2a shows a plan view of a power module according to a preferred embodiment, wherein the potting compound is hidden for clarity purposes, Fig. 2b shows a detailed view of the contacting on the power module according to Fig. 2a, Fig. 2c shows a section BB through the power module according to Fig. 2a,b, Fig. 3a,b show a detailed view analogous to Fig. 2b and a side sectional view of a power module according to another preferred embodiment, Fig. 4 shows a detailed view analogous to Fig. 2b of a further preferred embodiment of the power module according to the invention. Embodiments of the invention

[0021] Identical elements or elements with the same function are provided with the same reference numerals in the figures.

[0022] Fig. 1a and Fig. 1b shows a prior art structure of a power module 10' comprising a first, lower circuit carrier 1, which is preferably designed as an AMB circuit carrier or AMB substrate, and at least one, preferably several, semiconductor elements 2, in particular in the form of SiC MOSFETs, arranged thereon and contacted with the first circuit carrier 1. The power module 10' further comprises a second circuit carrier 3, in particular a DBC circuit carrier or a DBC substrate, the rear side 5b of which is contacted with a front side of the at least one semiconductor component 2 or the plurality of semiconductor components 2. A contacting layer 2a, for example Alloy42, is advantageously arranged between the semiconductor component and the second circuit carrier 3.

[0023] The first and second circuit carriers 1, 3 each comprise a substrate 1a, 3a, preferably a ceramic substrate, with electrically conductive layers 4a, 4b, 5a, 5b on a front and rear side. The ceramic substrate can comprise aluminum oxide (Al2O3) or a non-oxide ceramic such as silicon nitride (Si3N4).

[0024] On the rear side, the power module 10' can be thermally coupled to a cooling element or a heat sink (not shown) by means of a suitable layer 15, in particular a cooling solder.

[0025] The power module 10' is encapsulated with a potting compound or mold 11. This mold particularly fills the gaps 17 formed between the first and second circuit carriers 1, 3 and the semiconductor element 2. During operation of the power module, functionally critical delamination or cracking can occur in these gaps 17, particularly between the potting compound 11 and one of the two adjacent circuit carriers 1, 3.

[0026] Fig. 2a-c show a preferred embodiment of the power module 10 according to the invention. This basically has a structure similar to the prior art; in this respect, reference is first made to the above description of the power module 10'. Deviating from this, the power module 10 according to the invention comprises a detection unit 6, which is designed to monitor a contact region 7a, 7b between the potting compound 11 and at least one conductive layer 4b, 5a of a circuit carrier 1, 3 adjacent thereto for crack formation.

[0027] The detection unit 6 is preferably designed as an ASIC, which is dielectrically connected to the top side of the second circuit carrier 3, in particular a DBC circuit carrier. The detection unit 6 is contacted to the DBC circuit carrier via bonding wires in such a way that a capacitance between the first circuit carrier 1, preferably an AMB circuit carrier, and the second circuit carrier 3 can be measured.

[0028] Here, the detection unit 6 is contacted by means of bonding wire 8a with a contact section 12 on the upper side of the second circuit carrier 3, which in turn is connected by means of bonding wire 8b with the upper side of the first circuit carrier 1 in such a way that a drain potential Φ Dcan be detected on the top side of the first circuit carrier 1. Furthermore, the detection unit 6 is connected by means of bonding wires 9a,b to the top side of the second circuit carrier 3 and by means of a contact section 13, which is contacted with the semiconductor component 2 arranged underneath for guiding the source sense, preferably also by means of bonding wire 14, wherein a rear-side source potential Φ S can be measured on the second circuit carrier 3.

[0029] By monitoring or preferably continuously or intermittently checking the capacitance between the AMB and DBC circuit carriers 1, 3, the contact region 7a, 7b between the AMB and DBC circuit carriers can be monitored for crack formation or delamination between the AMB, DBC circuit carrier 1, 3, the semiconductor component 2 and the intermediate layer of encapsulant 11.

[0030] The detection unit 6 can be configured analogously to the crack detection unit described in DE 10 2018 210 613 A1. In particular, the detection unit can comprise a processing unit configured to generate a crack detection signal for detecting a crack in the contact region and transmit it to the sensor electrodes, and to detect an impedance in the contact region and, depending on the impedance, to generate and output a crack signal representing a crack. In this case, a fracture within the semiconductor component 2 can also be detected, since the electric field between the monitored source and drain potential also changes.

[0031] The detection unit 6 is preferably further configured to read NTC resistors 16 arranged on the power module 10 for temperature monitoring and to consider this information for monitoring crack formation. This ensures that a change in capacitance is solely due to delamination or crack formation, since capacitance is temperature-dependent. For this purpose, the detection unit 6 can comprise a memory unit in which values ​​or value ranges for a respective temperature and a respective associated value or value range for the capacitance can be stored and / or retrieved.

[0032] The detection unit 6 can be encapsulated or molded onto the surface of the second circuit carrier 3. Alternatively, the detection unit can be connected to the second circuit carrier 3 after the module has been encapsulated during production of the power module.

[0033] Fig. 3a,b show a further preferred embodiment in which the power module 10 has an alternative contacting of the second circuit carrier 3 for detecting the rear source potential Φ S In particular, the detection unit 6 is initially connected, analogously to the previous embodiment, by means of bonding wires 8a,b via a contact area 12 on the second circuit carrier 3 to the upper side of the first circuit carrier 1 in such a way that a drain potential Φ D can be detected on the top side of the first circuit carrier 1.

[0034] For the detection of the back source potential Φ S The detection unit 6 is connected to a rear-side conductive layer by means of a bonding wire 9a and a through-hole or VIA 9c. This eliminates the need for a wire bond 14 (see Fig. 2a,b) for guiding the semiconductor source-sense to the top of the second circuit carrier 3.

[0035] A further preferred embodiment for detecting the back source potential Φ S represents the wire bonding of SiC source of the semiconductor element 2 according to Fig. 4. A wire bond 9d can be led directly from the semiconductor 2 or from an adjacent spacer surface onto the surface of the second circuit carrier 3. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2018 210 613 A1 [0012, 0030]

Claims

[1] Power module (10) comprising a semiconductor component (2), in particular a power semiconductor, which is arranged between a first circuit carrier (1) and a second circuit carrier (3) and is contacted therewith, said second circuit carrier being at least partially enclosed by a potting compound (11), characterized by in that the power module has a detection unit (6) which is designed to monitor a contact region (7a, 7b) between the potting compound (11) and at least one conductive layer (4b, 5a) of a circuit carrier (1, 3) lying against it for crack formation. [2] Power module according to claim 1, characterized by that the detection unit (6) is designed to detect crack formation in the contact region (7a,7b) by means of impedance detection, in particular capacitively. [3] Power module according to claim 1 or 2, characterized bythat the detection unit (6) is designed to detect a capacitance between the first circuit carrier (1) and the second circuit carrier (3) via a top-side drain potential of the first circuit carrier (1) and a back-side source potential of the second circuit carrier (3). [4] Power module according to one of claims 1 to 3, characterized by that the detection unit (6) comprises at least a first sensor electrode (4b) and an opposite second sensor electrode (5a), which enclose the potting compound (11) between each other. [5] Power module according to claim 4, characterized by that the first sensor electrode (4b) is formed by a conductive layer of the first circuit carrier (1) and the second sensor electrode (5a) is formed by an oppositely arranged conductive layer of the second circuit carrier (3). [6] Power module according to one of the preceding claims, characterized bythat the detection unit (6) is designed as an application-specific circuit (ASIC). [7] Power module according to one of the preceding claims, characterized by that the detection unit (6) is designed to detect a break within the semiconductor component (2). [8] Power module according to one of the preceding claims, characterized by that the power module (10) has at least one temperature detection unit (16), in particular an NTC resistor, and the detection unit (6) is designed to evaluate a respective temperature for monitoring for crack formation. [9] Power module according to one of the preceding claims, characterized by that the detection unit (6) is arranged on the upper side of the first circuit carrier (1), in particular a DBC substrate, and is dielectrically connected thereto. [10] Power module according to one of the preceding claims, characterized byin that the detection unit (6) has a processing unit which is designed to generate a crack detection signal for detecting a crack in the contact region (7a, 7b) and to send this to the sensor electrodes (4b, 5a), and to detect an impedance in the contact region (7a, 7b) and, depending on the impedance, and preferably a detected temperature signal, to generate and output a crack signal representing a crack. [11] Control unit for a motor vehicle comprising a power module (10) according to one of the preceding claims.

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