CIRCUIT BOARD WITH A HEAT-CONDUCTING ELEMENT

Abstract

The invention relates to a circuit board having at least one electrically insulating layer and at least one electrically conductive layer. The circuit board has at least one heat-conducting element which is embedded in the electrically insulating layer and which is of thermally conductive form. The heat-conducting element is designed to transport heat losses transversely with respect to an areal extent of the circuit board. According to the invention, the heat-conducting element has at least two sub- elements formed in each case by a metal body. The heat-conducting element has an electrically insulating connecting layer which is arranged between the sub-elements and which is designed to electrically insulate the sub-elements with respect to one another and connect the sub-elements to one another in thermally conductive fashion.

Claims

1. A circuit carrier (1, 26) with at least one fiber-reinforced electrically insulating layer (2) and at least one electrically conductive layer (5, 6, 7, 8, 10, 11), wherein the circuit carrier (1, 26) has at least one thermally conductive element (12), configured to conduct heat, that is embedded in a recess (9) in the electrically insulating layer (2), which element is configured to transport excess heat (25) transversely to a planar extent of the circuit carrier (1, 26), wherein the thermally conductive element (12) has at least two sub-elements (13, 14) that are each formed from a metal body and a connecting layer (15) that is electrically insulating, wherein the connecting layer (15) is positioned between the sub-elements (13, 14) and is configured to electrically insulate the sub-elements (13, 14) from one another and to connect the sub-elements to one another in a thermally conductive manner.

2. The circuit carrier (1, 26) as claimed in claim 1, characterized in that the connecting layer (15) is a plastic layer that is self-adhesive.

3. The circuit carrier (1, 26) as claimed in claim 1, characterized in that the connecting layer (15) is a ceramic layer.

4. The circuit carrier (1, 26) as claimed in claim 3, characterized in that the thermally conductive element (12) is a direct-bonded metal substrate, wherein the sub-element is eutectically bonded to a connecting layer formed from ceramic.

5. The circuit carrier (1, 26) as claimed in claim 3, characterized in that the thermally conductive element (12) is a high-temperature co-fired ceramic substrate.

6. The circuit carrier (1) as claimed in claim 1, characterized in that at least one electrically conductive layer of the circuit carrier and the thermally conductive element include an additional electrically insulating layer (3, 4) between them, wherein the thermally conductive element (12) is connected to the electrically conductive layer (10, 11) in a thermally conductive manner by at least one thermally conductive metal bridge (16, 17) that passes through the additional electrically insulating layer (3, 4).

7. The circuit carrier (1) as claimed in claim 6, characterized in that the metal bridge (16, 17) is formed from a via.

8. The circuit carrier as claimed in claim 1, characterized in that the connecting layer (15) is formed from a thermally conductive adhesive.

9. A connecting arrangement comprising a circuit carrier (1) as claimed in claim 1, wherein the connecting arrangement has at least one semiconductor component (21) connected to the electrically conductive layer and the circuit carrier (1) is connected, in a thermally conductive manner, to a heat sink (20) on a side of the circuit carrier (1) that is facing away from the semiconductor component (21).

10. A method for guiding excess heat (25) away from a semiconductor component (21) to a heat sink (20), through the circuit carrier as claimed in claim 1, wherein the excess heat (25) is guided away from the semiconductor component (21) to an electrically conductive layer (10), soldered to the semiconductor component (21), and, passes via at least one thermally conductive metal bridge (16) through at least one electrically insulating layer (2, 3) and is guided to a thermally conductive element (12) which is embedded in the at least one electrically insulating layer (2, 3) and which is cohesively connected to the metal bridge (16), and is transferred from the thermally conductive element (12) to an additional electrically conductive layer (11) via at least one additional metal bridge (17) and from there to the heat sink (20), wherein the thermally conductive element (12) has at least two sub-elements (13, 14), each formed from a metal body and connected to one another via an electrically insulating connecting layer (15), wherein one sub-element (13) is connected to the metal bridge (16) and the other sub-element (14) of the two sub-elements (13, 14) is connected to the additional metal bridge (17) in a thermally conductive manner, so that the excess heat (25) may flow from the semiconductor component (21) to the heat sink (20) through the connecting layer (15).

11. A method for guiding excess heat (25) away from a semiconductor component (21) through a circuit carrier (1) to a heat sink (20), wherein the excess heat (25) is guided away from the semiconductor component (21) to an electrically conductive layer (10) connected to the semiconductor component (21).

12. The method as claimed in claim 11, wherein excess heat passes via at least one thermally conductive metal bridge (16) through at least one electrically insulating layer (2, 3) and is guided to a thermally conductive element (12) which is embedded in the at least one electrically insulating layer (2, 3) and which is cohesively connected to the metal bridge (16), and is transferred from the thermally conductive element (12) to an additional electrically conductive layer (11) via at least one additional metal bridge (17) and from there to the heat sink (20), wherein the thermally conductive element (12) has at least two sub-elements (13, 14), each formed from a metal body and connected to one another via an electrically insulating connecting layer (15), wherein one sub-element (13) is connected to the metal bridge (16) and the other sub-element (14) of the two sub-elements (13, 14) is connected to the additional metal bridge (17) in a thermally conductive manner, so that the excess heat (25) may flow from the semiconductor component (21) to the heat sink (20) through the connecting layer (15).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will now be explained below with reference to figures and further exemplary embodiments. Further advantageous embodiments may be obtained from the features described in the figures and in the dependent claims.

[0028] FIG. 1 shows one exemplary embodiment of a step in the method for producing a circuit carrier formed from multiple layers, wherein an opening is punched into the circuit carrier;

[0029] FIG. 2 shows the circuit carrier shown in FIG. 1, wherein, in an additional method step, a thermally conductive element is inserted into the opening;

[0030] FIG. 3 shows the circuit carrier produced in FIG. 2, comprising the thermally conductive element;

[0031] FIG. 4 shows the circuit carrier represented in FIG. 3, wherein the thermally conductive element is connected to an electrically conductive layer of the circuit carrier via metal bridges that pass through an electrically insulating layer;

[0032] FIG. 5 shows a connecting arrangement comprising the circuit carrier shown in FIG. 4, wherein the circuit carrier is connected to a heat sink and to a semiconductor component;

[0033] FIG. 6 shows a top view of the circuit carrier represented in FIG. 4;

[0034] FIG. 7 shows one variant of a connecting arrangement comprising a circuit carrier, wherein the thermally conductive element extends through at least one outer electrically conductive layer and terminates with a surface of the electrically conductive layer.

DETAILED DESCRIPTION

[0035] FIG. 1 shows one exemplary embodiment of a step in the method for producing a circuit carrier formed from multiple layers. In the method step shown in FIG. 1, a recess or opening is made, using a punching tool 23 or a drilling tool (not shown in FIG. 1), in a portion of the circuit carrier, which circuit carrier comprises an electrically insulating layer 2, on a surface region 24 that is smaller than a surface region of the electrically insulating layer 2.

[0036] In the example shown in FIG. 1, the electrically insulating layer 2 is bonded to additional electrically conductive layers 5, 6, 7 and 8, and thus forms a core of a circuit carrier formed from multiple layers.

[0037] FIG. 2 shows a method step wherein a thermally conductive element 12 is inserted into the opening 9 previously made in the method step shown in FIG. 1. The thermally conductive element 12 has two sub-elements 13 and 14, each being connected to one another, in a thermally conductive manner, by means of a connecting layer 15 and electrically insulated from one another.

[0038] FIG. 3 shows the portion of the circuit carrier shown in FIGS. 1 and 2, wherein the thermally conductive element 12 is inserted into the opening 9 represented in FIG. 2.

[0039] FIG. 4 shows the circuit carrier 1. The circuit carrier 1 has, in an additional method step, an electrically insulating layer 3 that is laminated onto the portion of the circuit carrier shown in FIG. 3. In addition, at least one via, three vias in this exemplary embodiment, are produced in the electrically insulating layer 3, one via 16 of which is referenced by way of example. In this exemplary embodiment the vias are each formed from a metal bridge, in particular a metal bridge taking the form of a cylinder.

[0040] The circuit carrier 1 shown in FIG. 4 also has an electrically conductive layer 10, which is laminated onto the electrically insulating layer 3. The vias, such as the via 16, are each designed to connect the electrically conductive layer 10 and the sub-element 13 of the thermally conductive element 12 to one another both electrically and in a thermally conductive manner.

[0041] On a side of the electrically insulating layer 2 that is facing away from the electrically insulating layer 3, an electrically insulating layer 4 is bonded to the electrically insulating layer 2 by means of lamination. At least one via, three vias in this exemplary embodiment, are produced in the electrically insulating layer 4, one via 17 of which is referenced by way of example. The vias, such as the via 17, are each formed from a metal bridge, for example a metal bridge produced by electroplating or thermal spraying. The vias, such as the via 17, are connected to the sub-element 14 electrically and in a thermally conductive manner. The vias, such as the via 17, are connected to an electrically conductive layer 11, which is bonded to the electrically insulating layer 4.

[0042] The electrically conductive layers 10 and 11 are thus each connected to a sub-element of the thermally conductive element 12 in a thermally conductive manner and electrically insulated from one another. Thus, with the circuit carrier 4, a semiconductor component may be soldered onto the electrically conductive layer 10 and a cooling element, serving as a heat sink, may be soldered onto the electrically conductive layer 11.

[0043] FIG. 5 shows a connecting arrangement in which the circuit carrier 1 is soldered to a semiconductor component 21 and to a heat sink, formed from a cooling element 20. The electrically conductive layer previously shown in FIG. 4 is bonded to the semiconductor component 21 by means of a layer of solder 18. The semiconductor component 21 is, for example, formed from a diode or a semiconductor switch, in particular a field-effect transistor. The semiconductor switch is, for example, formed from an unpackaged semiconductor switch, also referred to as bare die, or from a packaged semiconductor switch.

[0044] The cooling element 20 is, in this exemplary embodiment, formed from a block of copper. Fluid channels are formed in the copper block, one fluid channel 22 of which is referenced by way of example. The cooling element 20 is, in this exemplary embodiment, bonded to the electrically conductive layer 11 by means of a layer of solder 19. The cooling element 20 is positioned opposite the semiconductor component 21 on the circuit carrier 1, so that excess heat 25 generated by the semiconductor component 21 may flow from the semiconductor component 21, through the layer of solder 18, the electrically conductive layer 10 and the vias, such as the via 16, to the sub-element 13 of the thermally conductive element 12. In addition, the excess heat 25 may flow through the connecting layer 15 to the sub-element 14 and from there through the vias, such as the via 17, to the electrically conductive layer 11, and from there onward through the layer of solder 19 to the cooling element 20, serving as a heat sink. The excess heat may be guided away by a cooling fluid, for example cooling water, guided in the fluid channels, such as the fluid channel 22, of the cooling element 20.

[0045] The cooling element 20 may, instead of having the fluid channels, have cooling fins designed to dissipate the excess heat 25 by means of convection.

[0046] FIG. 6 shows a top view of the circuit carrier 1 previously shown in FIG. 3. The surface region 24 of the thermally conductive element 12 is smaller than the surface region of the electrically insulating layer 2 along a planar extent of the circuit carrier.

[0047] FIG. 7 shows one variant of the connecting arrangement previously shown in FIG. 5. The connecting arrangement according to FIG. 7 has a circuit carrier 26 that is bonded to the semiconductor component 21 by means of a layer of solder 18 and to the cooling element 20 by means of a layer of solder 19. The circuit carrier 26 is, in the exemplary embodiment shown in FIG. 4, formed from multiple layers and comprises an inner electrically insulating layer 2, additional electrically conductive layers 5, 6, 7 and 8 that are bonded to the electrically insulating layer 2 and two additional electrically insulating layers 3 and 4 that include the electrically insulating layer 2 between them. The electrically insulating layer 3 is bonded to an electrically conductive layer 10 and the electrically insulating layer 4 is bonded to an electrically conductive layer 11. The electrically conductive layers 10 and 11 thus include the aforementioned electrically insulating layers 2, 3 and 4 and the electrically conductive layers 5, 6, 7 and 8 between them—in particular in a sandwich-like manner. In the circuit carrier 26 thus formed, a recess, an opening 27 in this exemplary embodiment, may be made by means of a punching tool 23 or a drilling tool in accordance with the method step shown in FIG. 1. The thermally conductive element 12 may then be inserted into the opening 27 in accordance with the method step shown in FIG. 2. The thermally conductive element 12 has, in the exemplary embodiment shown in FIG. 7, the same thickness-wise extent 28 as the circuit carrier 26 formed from multiple layers.

[0048] The semiconductor component 21 extends, in this exemplary embodiment, both over the sub-element 13 and over a portion of the electrically conductive layer 10. The semiconductor component 21 is thus soldered to the electrically conductive layer 10 and to the sub-element 13 by means of the layer of solder 18.

[0049] The semiconductor component 21 has, in this exemplary embodiment, an electrical terminal that is formed from a surface region of the semiconductor component 21. The surface region of the semiconductor component 21 is electrically connected to the electrically conductive layer 10 via the layer of solder 18 and connected to the sub-element 13 both electrically and in a thermally conductive manner via the layer of solder 18, so that excess heat 25 generated by the semiconductor component 21 may be transferred to the sub-element 13. The excess heat 25 may be transferred through the electrically insulating layer 15 to the sub-element 14 and from there through the layer of solder 19 to the cooling element 20. The cooling element 20 is, for example, formed from a copper cooling element or from an aluminum cooling element. The sub-elements 13 and 14 are each formed from a block of metal, for example a block of copper or of aluminum.