Power module with encapsulated power semiconductors for a controllable electrical power supply of a consumer and method for producing the power module

Abstract

The present invention relates to a power module (1) for controllable electrical power supply of a power-consuming device, wherein the power module (1) comprises: a plurality of packaged power semiconductors (3), each packaged power semiconductor having a non-electrically insulating heat-dissipating surface (15); a printed circuit board (5); a heat sink (7); and one or more insulating plates (50), wherein the printed circuit board (5) is disposed on the side of the power semiconductor (3) opposite to the heat sink (7) in an orthogonal direction, wherein the insulating plate (50) is disposed between the packaged power semiconductor (3) and the cooling surface (17) of the heat sink (7), wherein one side of each insulating plate (50) is form-fitted to a non-electrically insulating heat-dissipating surface (15) of the packaged power semiconductor (3), and the other side is form-fitted to the heat sink (7). The invention also relates to a method of manufacturing.

Description

[0001] The present invention relates to a power module having encapsulated power semiconductors for controllable power supply of a power-consuming device, and to a method for manufacturing the power module.

[0002] Power modules are used to supply the power required for the operation of power-consuming devices (such as electric motors) in a controlled manner. This type of power module is sometimes also called an inverter, transformer, or AC converter.

[0003] For example, a power module can be used in a vehicle to supply electrical power from a battery to an electric motor that serves as a drive in a controlled manner. In this case, the range of controllable power supply can be from several kilowatts to several hundred kilowatts.

[0004] For this purpose, power modules typically have power semiconductor components (hereinafter referred to as "power semiconductors"), such as in the form of IGBTs (insulated gate bipolar transistors), SiC (power modules with silicon carbide MOSFETs) or power MOSFETs controlled by control circuitry.

[0005] In the case of conventional power modules, IGBT or SiC chips are applied (i.e., soldered or sintered) onto a so-called DCB (Direct Copper Bond) (i.e., a structure that enables tight electrical and thermal connections between electronic components and chips via copper). The DCB can then be sintered or soldered to, for example, a copper plate with a cooling structure. The entire structure can then be molded in a dielectric-sealed manner.

[0006] Alternatively, in the case of traditional power modules, IGBT components are mounted on the heatsink via a so-called thermal interface material (such as foil or thermal paste). Alternatively, the electrically insulating housing of this type of component can be directly soldered or sintered to the heatsink. In this case, electrical connections are made, for example, by soldering to a stamped grid or by soldering the component to a printed circuit board via through-hole technology.

[0007] In German patent application DE 10 2019 206 523.6, which has not yet been pre-published, a power module is described in which the heat-dissipating surface (also known as "exposed pads") of a packaged power semiconductor is applied to a heat sink. One drawback of this approach is that the heat-dissipating surface of the packaged power semiconductor must first be electrically insulated before it can be thermally connected to the heat sink. This electrical insulation is typically done internally within the power semiconductor in a circuit-electrical manner, making the structure of the power semiconductor complex and therefore expensive.

[0008] Therefore, an object of the present invention is to provide an alternative power module having a non-electrically insulated power semiconductor. Another object is to provide a method for manufacturing this type of power module.

[0009] These objectives can be achieved through the subject matter of the independent claims. Further embodiments of the invention are set forth in the dependent claims and the following description.

[0010] One aspect of the invention relates to a power module for a controllable electrical power supply to a power-consuming device. In this embodiment, the power module comprises: a plurality of packaged power semiconductors, each having a non-electrically insulated heat-dissipating surface; a printed circuit board; a heat sink; and one or more insulating plates. The printed circuit board is disposed on the side of the power semiconductor opposite to the heat sink in an orthogonal direction. The insulating plate is disposed between the packaged power semiconductor and the cooling surface of the heat sink. One side of each insulating plate is form-fitted to a corresponding non-electrically insulated heat-dissipating surface of the packaged power semiconductor, and the other side is form-fitted to the heat sink.

[0011] Of course, the heat dissipation surfaces of multiple packaged power semiconductors can also be connected to a common insulating plate.

[0012] Since, in the case of power semiconductors, a portion of the conducted electrical power always results in heat generation as a loss, the packaged power semiconductor, as previously described, has a heat dissipation surface on its outer side. This type of heat dissipation surface is sometimes referred to as a "bare pad." This heat dissipation surface can be designed as a layer or plate, integrated within the packaged power semiconductor and exposed on the surface, and made of a thermally conductive material (such as metals, particularly copper). In this invention, these heat dissipation surfaces are not electrically insulating.

[0013] In the overall design concept described here for the power module, each packaged power semiconductor is thermally connected to the cooling surface of a heat sink via an insulating plate. For this purpose, the heat-dissipating surface of the power semiconductor contacts the insulating plate, which in turn contacts the cooling surface of the heat sink in a thermally conductive manner. In this case, the insulating plate may be made of ceramic and has metallization on both the side facing the power semiconductor and the side facing the heat sink. In this configuration, the power semiconductor is applied to one side of the insulating plate in a form-fit manner (e.g., by welding, sintering, or gluing). Furthermore, the other side of the insulating plate is applied to the heat sink, for example, by welding, sintering, or gluing.

[0014] This allows for optimal form-fit connection between the heat dissipation surface of the power semiconductor and the insulating plate, as well as optimal form-fit connection between the insulating plate and the heat sink. The result is electrical insulation between the heat dissipation surface of the power semiconductor and the heat sink, while maintaining optimal thermal connection.

[0015] To dissipate heat from the power semiconductor, as previously mentioned, the power module has a heat sink. This heat sink can be a metal plate, for example, particularly a copper plate. Alternatively, the heat sink can have an integrated cooling structure, such as a cooling fin. The heat sink can be cooled passively, for example, through radiative and / or thermal exchange with the ambient medium. Alternatively, the heat sink can be cooled actively, for example, by allowing a cooling medium to flow through the heat sink.

[0016] In the concept presented here, the printed circuit board of the power module is arranged on the side of the power semiconductor opposite to the side where the heat sink is arranged in the orthogonal direction. In other words, for example, the heat sink can be arranged below the power semiconductor, while the printed circuit board is arranged above the power semiconductor. In this case, the printed circuit board can cover the entire area of ​​the power module in which the power semiconductor is arranged, or it can even extend laterally (i.e., laterally to the orthogonal direction) beyond that area.

[0017] The connection elements of the power semiconductor then make electrical contact with the printed circuit board in order to receive electrical signals and / or electrical power, for example, via the printed circuit board. For this purpose, in the first variant, connection surfaces are provided on the surface of the printed circuit board pointing towards the power semiconductor; these connection surfaces are conductive and, for example, made of metal.

[0018] For example, connecting elements can be electrically connected to connection surfaces on the heat sink-facing side of a printed circuit board. In this case, connecting elements extending parallel to the printed circuit board can be attached to the connection surfaces of the printed circuit board and then electrically connected to these connection surfaces, for example, by brazing or soldering. In particular, a method known as split headsoldering can be used for this purpose, in which connecting elements are pressed against the connection surfaces and current is conducted through them, by means of which heat is generated to melt the solder.

[0019] In another variant of the invention, the printed circuit board has through-holes. These through-holes (also called vias or via holes) have metallization and serve as connection surfaces in this case for contacting connection elements of power semiconductors (through-hole technology). The connection elements are then soldered into the through-holes, for example.

[0020] According to one embodiment, the power module may further have a sealant that covers both the encapsulated power semiconductor and at least a portion of the printed circuit board to protect against the environment.

[0021] Depending on the operating conditions, it may be necessary to encapsulate components of the power module to protect them from the environment, such as preventing contact with surrounding fluid media or contaminants (e.g., metal shavings). For example, contact between liquids (e.g., water) and power module components should be avoided to prevent electrical short circuits and / or corrosion. Particularly in applications where the power module is used in highly corrosive media (e.g., in gearboxes filled with corrosive oil), the components of the power module should be tightly packaged or encapsulated.

[0022] For this purpose, the power module may have a sealant that covers both the encapsulated power semiconductor and at least a portion of the printed circuit board to protect against environmental conditions. The sealant may be composed of materials that can be used in liquid or viscous form and subsequently cured. For example, the sealant may be formed from plastic materials, particularly thermosetting plastics, thermoplastics, polymers, and / or elastomers. The sealant can be applied by processes such as spraying, molding, casting, or other methods.

[0023] Another aspect of the present invention is a method for producing a power module for supplying controllable electrical power to a power-consuming device. In this case, the method according to the invention comprises the following steps:

[0024] a) Provide a radiator,

[0025] b) Assemble one or more pre-soldered components onto the cooling surface of the radiator.

[0026] c) Assemble the insulating board onto these pre-soldered materials.

[0027] d) Assemble the pre-soldering onto these insulating boards.

[0028] e) Assemble the packaged power semiconductor with a non-electrically insulating heat-dissipating surface onto these pre-soldering materials.

[0029] f) Perform a soldering process in which the insulating plates are soldered to the packaged power semiconductor and heat sink.

[0030] The pre-solder is composed of solder material and can exist, for example, in the form of a disc or as a foil. To position the pre-solder on the carrier, a welding frame can be used, for example, whose geometry defines the position of the pre-solder and the component to be soldered onto the carrier. Therefore, this geometry is determined by the welding frame, and these geometries must be maintained accordingly when manufacturing different components. However, the pre-solder can also be applied using SMD technology in steps c) and e).

[0031] In step f), pre-soldering is performed between the insulating plate and the heat sink, and between the insulating plate and the power semiconductor, in a single soldering process.

[0032] In one variant of the invention, in step g), a printed circuit board is provided and connected to a connection element of the packaged power semiconductor. During the manufacture of the power module, the connection element is electrically connected to the connection surface in a simple manner, such as by soldering.

[0033] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings.

[0034] Figure 1 and Figure 2 A cross-sectional view through a power module according to different embodiments of the present invention is shown.

[0035] Figure 3 A schematic sequence of steps according to the method of the present invention is shown.

[0036] The reference numerals used in the accompanying drawings and their meanings are listed in summary form in the reference numeral list. In principle, identical or similar parts are given the same reference numerals. The accompanying drawings are schematic only and not drawn to scale.

[0037] Figure 1 and Figure 2 Each shows a cross-sectional view of a power module 1 through which a controllable electrical power supply is provided for a power-consuming device (such as an electric motor in an electric vehicle, for example) (not shown). Figure 2 It shows crossing Figure 1 A cross-sectional view of a slightly modified variant of power module 1.

[0038] The power module 1 includes multiple encapsulated power semiconductors 3, multiple insulating plates 50, a printed circuit board 5, a heat sink 7, and a sealant 9. The heat sink 7 may be designed as a cooling plate made of metal (such as copper) and may optionally have a cooling structure 21. Electrical and / or electronic components 11 are disposed on the printed circuit board 5 to form a control circuit 13 for controlling the power semiconductors 3. For example, electrical power may be fed from a battery via an external connector (not shown) and then controlled by the power module 1, for example, delivered to the motor phase of an electric motor via other external connectors (not shown).

[0039] Each power semiconductor in the power semiconductor 3 has a heat dissipation surface 15 on its outer side facing the heat sink 7. A metal surface or metal plate is provided on the heat dissipation surface 15 of the packaged power semiconductor 3, through which heat generated inside the packaged power semiconductor 3, such as by power control semiconductor components (such as IGBTs, SiC or power MOSFETs) located inside the packaged power semiconductor 3, can be dissipated.

[0040] In this configuration, each of the packaged power semiconductors 3 has a conductive connection element 23. The connection element 23 is used to electrically connect power control structures, such as semiconductor components inside the packaged power semiconductor 3, to provide them with control signals and / or the electrical power to be controlled.

[0041] Each of the packaged power semiconductors 3 is connected to an insulating plate 50. In this case, the insulating plate 50 is arranged between the packaged power semiconductor 3 and the heat sink 7. The insulating plate 50 has metallization 51 on its upper side 51a facing the packaged power semiconductor 3 and its lower side 51b facing the heat sink 7, respectively. Pre-solder 52 is further arranged between the metallization 51 and the packaged power semiconductor 3 and between the metallization 51 and the heat sink 7, respectively.

[0042] Pre-solder 52 is thermally bonded to the metallization 51 on the corresponding sides 51a, 5b of the insulating plate 50. During the soldering process, on one side 51a of the insulating plate 50, the pre-solder 52 connects the insulating plate 50 to the heat dissipation surface 15 of the power semiconductor 3. On the other side 51b of the insulating plate, the pre-solder 52 connects the insulating plate 50 to the cooling surface 17 of the heat sink 7. Thus, the insulating plate 50 is thermally connected to the cooling surface 17 of the heat sink 3. Furthermore, the heat dissipation surface 15 of the packaged power semiconductor 3 is thermally connected to the cooling surface 17 of the heat sink 7 via the insulating plate 50.

[0043] The printed circuit board 5 is arranged on the side of the power semiconductor 3 opposite to the side where the heat sink 7 is arranged in the orthogonal direction. In other words, the power semiconductor 3 is located between the heat sink 7 and the printed circuit board 5.

[0044] The connecting element 23 of the power semiconductor 3 is arranged such that the connecting element 23 is in electrical contact with the connecting surface 25 on the printed circuit board 5. For this purpose, in Figure 1 In the embodiment shown, the elongated connecting element 23 is arranged laterally adjacent to the power semiconductor 3 and contacts the connecting surface 25 there.

[0045] Figure 2 It shows Figure 1 Variations of the embodiments shown are presented. To avoid repetition, in... Figure 2The description only mentions... Figure 1 The change.

[0046] The printed circuit board 5 has through holes 60. These through holes 60 (also called vias or vias) are metallized and therefore serve as connection surfaces 25 for connection elements 23 of the power semiconductor 3, in addition to serving as connection surfaces 25 on the lower and / or upper sides of the printed circuit board 5. In this case, the through holes 60 are designed such that the connection elements 23 can pass through the printed circuit board 5. This allows the connection elements 23 to be attached (e.g., soldered) to the connection surface 25 on the side of the printed circuit board 5 opposite to the power semiconductor 3.

[0047] Figure 3 A schematic sequence of steps according to the method of the present invention is shown.

[0048] In the first step S1, a heat sink 7 is provided. In step S2, one or more pre-solders 52 are then assembled onto the cooling surface 17 of the heat sink 7. In the third step S3, an insulating plate 50 is assembled onto these pre-solders 52. In the fourth step S4, the pre-solders 52 are then assembled onto the insulating plate 50. In the subsequent assembly step S5, the packaged power semiconductor 3 is arranged on the pre-solders 52 via a non-electrically insulated heat dissipation surface 15.

[0049] In the subsequent soldering process S6, the pre-solder 52 is melted in such a way that the insulating plate 50 is soldered to the packaged power semiconductor 3 and the heat sink 7. As a result, a thermal connection is achieved between the heat dissipation surface 15 of the power semiconductor 3 and the heat sink 7.

[0050] In step S7, a printed circuit board 5 is provided, and in step S8, the connection element of the packaged power semiconductor is connected to the printed circuit board 5.

[0051] Furthermore, it should be noted that "comprising" does not exclude any other elements or steps, and "a" does not exclude a plurality. It should also be noted that features or steps already described with reference to one of the preceding exemplary embodiments may also be used in combination with other features or steps from other previously described exemplary embodiments. Reference numerals in the claims should not be considered limiting.

[0052] Figure Labels

[0053] 1 Power Module

[0054] 3 Power Semiconductors

[0055] 5 Printed Circuit Boards

[0056] 7 Radiator

[0057] 9. Sealant

[0058] 11 components

[0059] 13 Control Circuit

[0060] 15. Heat dissipation surface

[0061] 17 Cooling Surface

[0062] 21 Cooling Structure

[0063] 23 Connecting elements

[0064] 25 Connecting surfaces

[0065] 50 Insulation Board

[0066] 51 Metallic compounds

[0067] 51a Upper side of the insulating board

[0068] 51b Underside of the insulating board

[0069] 52 Pre-soldering material

[0070] 60 through hole

[0071] S1-S8 Method Steps

Claims

1. A power module (1) for controllable electrical power supply to a power-consuming device, wherein, The power module (1) has: - A plurality of packaged power semiconductors (3), each of the plurality of packaged power semiconductors having a non-electrically insulating heat dissipation surface (15). - Printed circuit board (5). - Radiator (7) - One or more insulating boards (50). - A sealant (9) covering at least a portion of both the encapsulated power semiconductor (3) and the printed circuit board (5) to protect them from environmental elements; the sealant (9) is formed of a plastic material. The printed circuit board (5) is arranged on the side of the power semiconductor (3) opposite to the heat sink (7) in the orthogonal direction. The insulating plate (50) is disposed between the encapsulated power semiconductor (3) and the cooling surface (17) of the heat sink (7). Each insulating plate (50) is connected in a form-fitting manner to the corresponding non-electrically insulating heat dissipation surface (15) of the encapsulated power semiconductor (3) on one side, and in a form-fitting manner to the heat sink (7) on the other side. The insulating plate has conductive metallization (51) on the side facing the encapsulated power semiconductor (3) and on the side facing the cooling surface (17) of the heat sink (7).

2. The power module as described in any one of claims 1, characterized in that, The insulating plate is made of ceramic.

3. The power module as described in any one of claims 1 and 2, characterized in that, The connecting element (23) extends parallel to the connecting surface (25) on the printed circuit board (5) and makes electrical contact with the connecting surface (25).

4. The power module as described in claim 1, characterized in that, The connecting element (23) contacts the connecting surface (25) in the through hole (60) of the printed circuit board (5).

5. A method for producing a power module as described in any one of claims 1 to 4, the method comprising the following steps: a) Provide a radiator (7). b) Assemble one or more pre-soldering materials (52) onto the cooling surface (17) of the radiator (7), c) Assemble the insulating plate (50) onto the pre-soldering material (52), d) Assemble the pre-soldering material (52) onto the insulating plate (50), e) The packaged power semiconductor (3) is assembled onto the pre-solder (52) via a non-electrically insulated heat dissipation surface (15). f) Perform a welding process in which the insulating plate is welded to the encapsulated power semiconductor (3) and the heat sink (7). g) Provide a printed circuit board (5) and connect the printed circuit board to the connection element (23) of the packaged power semiconductor (3). h) Cover at least a portion of both the encapsulated power semiconductor (3) and the printed circuit board (5) with a sealant (9) to protect them from the environment.

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