Circuit assembly having circuit carrier and semiconductor component

Abstract

The invention relates to a circuit assembly (1) having a circuit carrier (3), a semiconductor component (5), a lead frame (7), an electrically insulating insulating element (9), a heat sink (11) and a hold-down unit (13). The semiconductor component (5) is arranged between the circuit carrier (3) and the lead frame (7). A heat sink (11) is arranged on the side of the lead frame (7) facing away from the semiconductor component (5). An insulating element (9) is arranged between the lead frame (7) and the heat sink (11). The pressing unit (13) is designed such that the circuit carrier (3), the semiconductor component (5), the lead frame (7), the insulating element (9) and the heat sink (11) are pressed against one another.

Description

Technical Field

[0001] The invention relates to a circuit arrangement having a circuit carrier and a semiconductor component. Background Art

[0002] In the field of power electronics, semiconductor components such as switching elements are usually present in the form of power modules, also referred to as power modules, or in the form of discrete packages. The semiconductor components are often contacted using special wire welding techniques, and the power module is fastened to a circuit carrier, for example using a welding connection, a spring connection or a press-fit connection. The use of wire welding limits the maximum permissible current density through the semiconductor components. In addition, parasitic inductances occur, which limit the achievable switching speed of the switching elements.

[0003] WO 2020 / 249479 A1 discloses an electronic circuit, which further comprises a first circuit carrier, a second circuit carrier and a power electronic semiconductor component. The semiconductor component has an upper side against the lower side of the first circuit carrier and a lower side against the upper side of the second circuit carrier. The first circuit carrier has a first via, which electrically connects the upper side of the first semiconductor component to the conductor circuit of the first circuit carrier. The second circuit carrier has, for example, a conductive layer forming its upper side and an electrically insulating layer arranged on the side of the conductive layer away from the first circuit carrier. The problem in such an arrangement of the circuit carrier and the semiconductor component is that the two circuit carriers can have very different thermal expansion coefficients. After the two circuit carriers are connected by material matching (i.e., material matching connection such as welding or sintering), this difference will cause the composite material structure to produce significant warping after cooling. Therefore, the second circuit carrier cannot make the entire surface contact with the heat sink, thereby compromising the heat dissipation of the circuit. In addition, the different expansion coefficients of the circuit carrier can cause cracks to form between the layers of the second circuit carrier, and the cracks can cause reliability problems until the failure of the entire circuit.

[0004] JP 2001 156225A discloses a semiconductor device having a pair of heat radiation elements. A semiconductor chip is arranged between the heat radiation elements. The heat radiation elements are made of a metal material having an electrical conductivity and / or thermal conductivity greater than that of tungsten or molybdenum.

[0005] US2020 / 343155 A1 discloses a power conversion device having two heat sinks, a printed circuit board having a circuit pattern formed thereon, and a switching element having an electrode portion electrically connected to the circuit pattern. A first insulating element is arranged between the first heat sink and the circuit board. A second insulating element is arranged between the second heat sink and the switching element.

[0006] DE 10 2014 205 958 A1 discloses a semiconductor switching element arrangement for use in a vehicle having a printed circuit board and semiconductor switching elements mounted on the printed circuit board, which is surrounded by a metal cover mounted on the printed circuit board. The metal cover can be in thermally conductive contact with a cooling device or can bring about such contact.

[0007] EP 3 440 906 A1 discloses an electronic module having a printed circuit board, at least one integrated circuit mounted on the printed circuit board and at least one shield mounted on the printed circuit board to protect against electromagnetic interference. The at least one integrated circuit is mounted within a region defined by the shield. Summary of the invention

[0008] The object of the present invention is to provide an improved circuit assembly which overcomes these problems.

[0009] This object is achieved according to the invention by a circuit arrangement having the features of claim 1 .

[0010] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0011] The circuit assembly according to the present invention comprises

[0012] - a circuit carrier,

[0013] -Lead frame,

[0014] a semiconductor component arranged between the circuit carrier and the lead frame,

[0015] a heat sink arranged on that side of the leadframe which faces away from the semiconductor component,

[0016] an electrically insulating insulating element arranged between the leadframe and the heat sink, and

[0017] A pressing unit which is designed to press the circuit carrier, the semiconductor component, the lead frame, the insulation element and the heat sink against one another.

[0018] For example, in contrast to the circuit assembly known from WO 2020 / 249479 A1, the circuit assembly according to the invention replaces two circuit carriers, between which the semiconductor components are arranged, with a circuit carrier and a lead frame, between which the semiconductor components are arranged. In addition, the circuit assembly has an insulating element, which is arranged between the lead frame and the heat sink. The lead frame and the insulating element assume the functions of the second circuit carrier of the circuit assembly known from WO 2020 / 249479 A1, namely, electrical contacting of the semiconductor components on the side of the semiconductor components facing the lead frame and thermal conduction from the semiconductor components to the heat sink.

[0019] The decoupling of the lead frame from the insulating element can solve the problem of warping of the circuit assembly, i.e. the lead frame is made of a material with a similar expansion coefficient as the circuit carrier and ensures that the insulating element and the lead frame are connected in a material-free manner. This significantly reduces the risk of cracks in the lead frame relative to cracks in the conductive layer of the second circuit carrier and can provide a potentially longer service life of the circuit assembly.

[0020] The hold-down unit can provide a large, temperature-independent contact surface and thus a good heat transfer between the heat sink, the insulation element and the leadframe and thus an improved heat dissipation of the semiconductor component.

[0021] Furthermore, replacing the second circuit carrier from WO 2020 / 249479 A1 by a combination of a lead frame and an insulating element advantageously reduces the costs of the circuit assembly, since an expensive second circuit carrier is no longer required. Furthermore, the thickness of the lead frame is designed to be higher than the thickness of the conductive layer of the second circuit carrier of WO 2020 / 249479 A1, which leads to improved heat dissipation of the semiconductor component.

[0022] The concept of the circuit assembly having a semiconductor component does not exclude the feasibility that the circuit assembly has a plurality of semiconductor components, and therefore it is understood that the circuit assembly has at least one semiconductor component. The same application concept is that the circuit assembly has a circuit carrier or a lead frame. For example, the circuit assembly can have a plurality of semiconductor components, each arranged between the circuit carrier and the lead frame, and an insulating element arranged between the heat sink and each lead frame. The circuit assembly can have a circuit carrier, all semiconductor components are arranged on one circuit carrier, or a plurality of circuit carriers, at least one semiconductor component is arranged on a plurality of circuit carriers. Accordingly, the circuit assembly can have a lead frame for all semiconductor components or a plurality of lead frames for at least one semiconductor component. If the circuit assembly has a plurality of semiconductor components, for example, at least one pair of two such semiconductor components is electrically connected to form a half bridge. The two semiconductor components can be connected, for example, via a circuit carrier, on which the two semiconductor components are arranged, or via another circuit carrier, the electrical connection of the other circuit carrier to the two circuit carriers, on which one of the two semiconductor components is arranged.

[0023] In one embodiment of the present invention, the insulating element is a ceramic plate. For example, the ceramic plate is made of aluminum oxide, aluminum nitride or silicon nitride. Such an insulating element has high thermal conductivity and provides mechanical stability to offset the pressing force applied by the pressing unit.

[0024] In another embodiment of the present invention, the insulating element is an insulating film. For example, the insulating film is made of a silicon-based material. Due to the elasticity of the insulating film, the insulating film is advantageously largely unaffected by temperature changes and unaffected by the pressing force applied by the pressing unit, and is therefore also suitable as an insulating element.

[0025] In a further embodiment of the invention, the heat sink has a recess into which the insulating element is inserted. The recess advantageously determines the position of the insulating element, in particular if the insulating element is connected to the heat sink in a non-materially bonded manner.

[0026] In another embodiment of the invention, the insulating element is connected to the heat sink or the lead frame in a non-materially bonded manner. As explained above, a materially bonded connection of the insulating element to the heat sink or to the lead frame is undesirable, so that the insulating element can be pressed onto the lead frame and the heat sink by the pressing unit flexibly and independently of temperature changes of other components of the circuit assembly.

[0027] In a further embodiment of the invention, a heat conducting medium is arranged between the insulating element and the heat sink and / or between the insulating element and the lead frame. For example, the heat conducting medium is a heat conducting oil. The heat conducting medium advantageously increases the heat transfer between the insulating element and the heat sink and / or between the insulating element and the lead frame and in particular therefore improves the heat dissipation of the semiconductor component.

[0028] In a further embodiment of the invention, the lead frame and the circuit carrier have similar coefficients of thermal expansion, thereby preventing a warping of the lead frame and the circuit carrier due to a large difference in the coefficients of thermal expansion of the lead frame and the circuit carrier.

[0029] In a further embodiment of the invention, the lead frame is made of copper. This embodiment of the invention is particularly advantageous if the first circuit carrier is a printed circuit board, since conventional circuit boards have a similar coefficient of thermal expansion as copper.

[0030] In a further embodiment of the invention, the clamping unit has at least one threaded connection, which connects the heat sink to the circuit carrier or to a clamping disk arranged on the side of the circuit carrier facing away from the heat sink. Such a threaded connection provides a simple, cost-effective design of the clamping unit that can be implemented with a flexible clamping force.

[0031] In a further embodiment of the invention, the circuit carrier is a printed circuit board, in particular a multilayer printed circuit board. The embodiment of the circuit carrier as a printed circuit board is particularly advantageous in that the semiconductor components can be connected to conductor tracks and vias extending in or on the printed circuit board.

[0032] In a further embodiment of the invention, the semiconductor component has a first load terminal arranged on the side of the semiconductor component facing the circuit carrier and electrically connected to the contact pad of the circuit carrier and a second load terminal arranged on the side of the semiconductor component facing the lead frame and electrically connected to the lead frame. In other words, the semiconductor component has load terminals arranged on opposite sides, each of which is electrically in contact with the circuit carrier or with the lead frame. This makes it possible to provide a contact of the semiconductor component that is similar to the contact known from WO 2020 / 249479 A1.

[0033] In another embodiment of the invention, the semiconductor component is a transistor or a diode or a thyristor. The circuit assembly according to the invention is suitable for all these semiconductor components, because all these semiconductor components can be designed so that the load terminals of the semiconductor components can be arranged on mutually opposite sides of the semiconductor components. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above-mentioned characteristics, features and advantages of the present invention and the manner in which they are achieved are clearly and clearly explained in conjunction with the description of the exemplary embodiments described in more detail below with respect to the accompanying drawings. It is shown here:

[0035] Figure 1 shows a schematic cross-sectional view of a first exemplary embodiment of a circuit assembly,

[0036] Figure 2 A schematic cross-sectional view of a second exemplary embodiment of a circuit assembly is shown.

[0037] Parts which correspond to one another are identified in the figures by the same reference numerals. DETAILED DESCRIPTION

[0038] Figure 1 ( FIG1 ) shows a schematic cross-sectional view of a first exemplary embodiment of a circuit assembly 1 .

[0039] The circuit assembly 1 comprises a circuit carrier 3 , a semiconductor component 5 , a lead frame 7 , an insulating element 9 , a heat sink 11 and a pressing unit 13 .

[0040] The semiconductor component 5 is arranged between the circuit carrier 3 and the lead frame 7. In the exemplary embodiment shown, the semiconductor component 5 is a transistor having a control terminal, a first load terminal and a second load terminal. The control terminal and the first load terminal face the circuit carrier 3, while the second load terminal faces the lead frame 7. In other exemplary embodiments, the semiconductor component 5 can be, for example, a diode or a thyristor. If the semiconductor component 5 is a diode, the semiconductor component does not have a control terminal, but only has two load terminals.

[0041] The control terminal of the semiconductor component 5 is connected to the first contact pad 15 of the circuit carrier 3. The first load terminal of the semiconductor component 5 is connected to the second contact pad 17 of the circuit carrier 3. The first contact pad 15 and the second contact pad 17 are arranged on the side of the circuit carrier 3 facing the semiconductor component 5. The second load terminal of the semiconductor component 5 is connected to the lead frame 7 by a connecting material 19, for example, a solder material or a sintering material.

[0042] The circuit carrier 3 is, for example, a multilayer printed circuit board in which a via extends, which connects each contact pad 15 , 17 to at least one conductor track of the printed circuit board.

[0043] The lead frame 7 is made of a material having a similar coefficient of thermal expansion as the circuit carrier 3. If the circuit carrier 3 is a printed circuit board, the lead frame 7 can be made of copper, for example. The lead frame 7 is also connected to the circuit carrier 3 via an electrically conductive connection 20. The remaining space between the lead frame 7 and the circuit carrier 3 is filled with an encapsulation material 21, for example a casting resin.

[0044] The heat sink 11 and the insulating element 9 are arranged on the side of the lead frame 7 facing away from the semiconductor component 5. The heat sink 11 has a recess 23 on the lead frame side, the size of which exceeds the size of the lead frame 7. The insulating element 9 is inserted into the recess 23, the size of which also exceeds the size of the lead frame 7. Therefore, the insulating element 9 is arranged in the recess 23 of the heat sink 11 between the lead frame 7 and the heat sink 11.

[0045] A heat conducting medium 25 is arranged between the insulating element 9 and the heat sink 11 and between the insulating element 9 and the lead frame 7. The heat conducting medium 25 is, for example, heat conducting oil. Therefore, the insulating element 9 is not connected to the heat sink 11 or the lead frame 7 in a materially bonded manner, but is only inserted into the recess 23 of the heat sink 11.

[0046] The insulating element 9 is made of an electrically insulating material having good thermal conductivity. For example, the insulating element 9 is a ceramic plate. The ceramic plate is made of, for example, aluminum oxide, aluminum nitride or silicon nitride. Alternatively, the insulating element 9 is an insulating film, which is made of, for example, a silicon-based material.

[0047] The pressing unit 13 is designed to press the combined structure including the circuit carrier 3, the semiconductor component 5 and the lead frame 7 onto the insulating element 9 and the heat sink 11. Figure 1 In the figure, the pressing unit 13 is only schematically shown by an arrow symbol, and the arrow symbol represents the direction of the pressing force applied by the pressing unit 13.

[0048] Figure 2 FIG2 shows a schematic cross-sectional view of a second exemplary embodiment of the circuit assembly 1. Figure 1 The difference between the illustrated embodiments is that they schematically show a specific embodiment of the pressing unit 13. In this embodiment, the pressing unit 13 has a pressing plate 27 and a screw connection 29. The pressing plate 27 is arranged on the side of the circuit carrier 3 facing away from the heat sink 11. The screw connection 29 connects the pressing plate 27 to the heat sink 11, and a pressing force is applied via the pressing plate 27, which presses the combined structure with the circuit carrier 3, the semiconductor component 5 and the lead frame 7 onto the insulating element 9 and the heat sink 11.

[0049] If the circuit carrier 3 is sufficiently stable, Figure 2 The second exemplary embodiment shown in can be modified to a third exemplary embodiment, in which the pressure disk 27 is omitted and the screw connection 29 connects the circuit carrier 3 directly to the heat sink 11 .

[0050] Although the present invention has been illustrated and described in detail by means of preferred exemplary embodiments, the present invention is not limited to the disclosed examples and other variations can be derived by those skilled in the art without departing from the scope of protection of the present invention.

Claims

1. A circuit assembly (1), comprising: - a circuit carrier (3), - a lead frame (7), a semiconductor component (5) arranged between the circuit carrier (3) and the lead frame (7), a heat sink (11) arranged on the side of the lead frame (7) facing away from the semiconductor component (5), - an electrically insulating insulating element (9) arranged between the lead frame (7) and the heat sink (11), and a pressing unit (13) which is designed to press the circuit carrier (3), the semiconductor component (5), the lead frame (7), the insulating element (9) and the heat sink (11) against one another, - wherein the circuit carrier (3) is a printed circuit board, in particular a multilayer printed circuit board.

2. The circuit assembly (1) according to claim 1, wherein: The insulating element (9) is a ceramic plate.

3. The circuit assembly (1) according to claim 2, wherein: The ceramic plate is made of aluminum oxide, aluminum nitride or silicon nitride.

4. The circuit assembly (1) according to claim 1, wherein: The insulating element (9) is an insulating film.

5. The circuit assembly (1) according to claim 4, wherein: The insulating film is made of a silicon-based material.

6. The circuit arrangement (1) according to any one of the preceding claims, wherein: The heat sink (11) has a recess (23) into which the insulating element (9) is inserted.

7. The circuit arrangement (1) according to any one of the preceding claims, wherein: The insulating element (9) is not connected to the heat sink (11) or the lead frame (7) in a materially bonded manner.

8. The circuit arrangement (1) according to any one of the preceding claims, wherein: A heat conducting medium (25) is arranged between the insulating element (9) and the heat sink (11) and / or between the insulating element (9) and the lead frame (7).

9. The circuit assembly (1) according to claim 8, wherein: The heat transfer medium (25) is heat transfer oil.

10. The circuit arrangement (1) according to any one of the preceding claims, wherein: The lead frame (7) and the circuit carrier (3) have similar coefficients of thermal expansion.

11. The circuit arrangement (1) according to any one of the preceding claims, wherein: The lead frame (7) is made of copper.

12. The circuit arrangement (1) according to any one of the preceding claims, wherein: The pressure unit (13) has at least one screw connection (29) which connects the heat sink (11) to the circuit carrier (3) or to a pressure disk (27) arranged on a side of the circuit carrier (3) facing away from the heat sink (11).

13. The circuit arrangement (1) according to any one of the preceding claims, wherein: The semiconductor component (5) has a first load terminal, which is arranged on the side of the semiconductor component (5) facing the circuit carrier (3) and is electrically connected to a contact pad (17) of the circuit carrier (3), and the semiconductor component has a second load terminal, which is arranged on the side of the semiconductor component (5) facing the lead frame (7) and is electrically connected to the lead frame (7).

14. The circuit arrangement (1) according to any one of the preceding claims, wherein: The semiconductor component (5) is a transistor, a diode or a thyristor.

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