EP3180967A1

EP3180967A1 - Circuit board with a heat-conducting element

Info

Publication number: EP3180967A1
Application number: EP15734593.5A
Authority: EP
Inventors: Thomas Wiesa
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-08-14
Filing date: 2015-06-23
Publication date: 2017-06-21
Also published as: CN106576423A; CN106576423B; DE102014216194B3; WO2016023663A1; US20170280552A1; US10117323B2

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.

Description

description

title

Circuit carrier with a heat conducting element

State of the art

The invention relates to a particularly flat formed circuit carrier with at least one in particular fiber-reinforced, electrically insulating layer and at least one electrically conductive layer. The circuit carrier has at least one heat-conducting element which is arranged in the electrically insulating layer and, in particular at least partially or completely embedded in the electrically insulating layer, is thermally conductive. The

Heat conduction is designed to transport heat loss across a flat Erstre- ckung the circuit substrate. The flat formed circuit carrier has a greater width extension than a transverse to the width extension extending thickness of the circuit substrate.

Disclosure of the invention

According to the invention, the heat-conducting element has at least two partial elements each formed by a metal body. The heat-conducting element preferably has an electrically insulating connection layer. The connecting layer is arranged between the sub-elements and is designed to electrically insulate the sub-elements from each other and to connect them to one another in a thermally conductive manner.

As a result, heat, in particular heat loss, can advantageously flow from one partial element to the further partial element, the partial elements advantageously being electrically insulated from one another. Thus, for example, a connection arrangement may be formed in which a component that generates waste heat, for example a semiconductor component, is connected to the circuit carrier, wherein the semiconductor device is arranged in the region of the heat-conducting element. The heat-conducting element can advantageously absorb the heat loss generated by the semiconductor component with a sub-element and forward it via the connecting layer to the further sub-element. The heat loss can then be advantageously discharged from the further sub-element to a heat sink, which is thermally conductively connected to the further sub-element. The thermally conductive connection between the further sub-element and the heat sink is preferably a cohesive metallic connection. Thus, advantageously, the semiconductor component, which is thermally conductive and electrically connected to the aforementioned subelement, be electrically insulated from the heat sink, in particular the heat sink.

The heat-conducting element preferably has a larger area-related heat capacity than the electrically conductive layer, in particular the conductor track of the circuit carrier, based on a flat extension of the circuit carrier.

As a result, the heat loss can advantageously be passed through the circuit carrier along its transverse to the flat extension extending thickness. For this purpose, the heat-conducting element preferably has a greater thickness extension than the electrically conductive layer.

The circuit carrier is preferably flat. More preferably, the circuit carrier has a greater width or length extension than a thickness extension.

The connecting layer of the heat-conducting element preferably extends coplanar with the circuit carrier. Thus, the heat conducting element can advantageously electrically insulate the heat conduction path through the circuit carrier.

In a preferred embodiment, the sub-elements are each formed by a copper block. Thus, the heat-conducting advantageously a large

Have thermal conductivity, which in the case of copper is at least 250 watts per meter and Kelvin, in the case of electrolytic copper 400 watts per meter and Kelvin. In another embodiment, the partial element is formed from silver. The circuit carrier can advantageously have a good thermal conductivity and thus a high power density and further advantageously a compact design.

In a preferred embodiment, the heat-conducting element, in particular the partial element, has a greater thickness dimension than the electrically conductive layer. The electrically conductive layer is preferably connected to the electrically insulating layer, for example a fiber-reinforced epoxy resin layer, produced from a prepreg, by means of lamination.

Thus, the heat conducting element can advantageously have a larger area-related heat capacity, as the electrically conductive layer, each based on a surface of the circuit substrate in its flat extension.

In a preferred embodiment, the compound layer is adhesively formed. More preferably, the bonding layer has an adhesive and is preferably self-adhesive. The bonding layer preferably comprises a plastic layer, more preferably a polyamide layer or

Polyimide layer, which may be formed for example by a film. The plastic layer preferably forms a carrier layer, which is connected to at least one, preferably two adhesive layers. Preferably, the two adhesive layers sandwich the plastic layer. As a result, the plastic layer may advantageously be adhesively bonded to the subelement via one of the two adhesive layers and adhesively bonded to the other of the two subelements via the second adhesive layer. The adhesive layer is preferably formed by a dispersion adhesive, in particular acrylic adhesive. In another embodiment, the adhesive layer is formed by a resin layer. The plastic layer can be glued to the sub-elements, for example, under the action of pressure and temperature. The resin is, for example, epoxy resin.

For example, the bonding layer is formed by a PSA (PSA = Pressure Sensitive Adhesive). The heat-conducting element can be advantageously provided at low cost. Thus, the heat-conducting element may advantageously be formed by an insertion part. The insertion part can be produced advantageously as low as an expense, preferably as an insertion part manufactured independently of the circuit carrier. The sub-elements can advantageously before inserting the heat-conducting in a the

Heat-conducting element corresponding recess in the circuit substrate are glued together and are inserted as bonded together sub-elements in the recess.

In a preferred embodiment, the tie layer is a

Ceramic layer. The ceramic layer preferably comprises aluminum oxide,

Beryllium oxide, silicon carbide, boron carbide or boron nitride.

Preferably, the heat-conducting element is advantageously provided by a DBM substrate (DBM = Direct-Bonded-Metal), in particular DBC substrate (DBC = Direct-Bonded-Metal).

Copper) be formed. The connection between the partial element and the ceramic connecting layer is preferably a eutectic connection. The sub-elements can be connected so advantageous cohesively with the connection layer.

For example, both partial elements are formed from copper or aluminum, or a partial element is formed from copper and the further partial element is formed from aluminum.

The aforementioned eutectic compound can be produced, for example, by oxidizing the partial elements, in particular copper or aluminum elements, on one side and pressing them against the connecting layer, in particular the ceramic layer, with the metal oxide layer produced in this way. During the pressing process, the bonding layer, in particular the ceramic layer, and the at least one subelement become at least 1000

Degrees Celsius heated. As a result, a heat conducting element can advantageously be produced, which advantageously has a high strength and can advantageously withstand a large number of thermal cycling without delaminating. In a preferred embodiment, the heat-conducting element is a HTCC substrate (HTCC = High-Temperature Cofired Ceramics). Thus, advantageously, a large thermal conductivity of the heat conducting element can be formed in addition to a good electrical insulation.

In a further advantageous embodiment, the heat-conducting element is formed by an AM B substrate (AMB = Active Metal Brazed). The AM B substrate preferably comprises at least one copper layer and at least one

Ceramic layer, in particular aluminum oxide, silicon nitride, aluminum nitride, or beryllium oxide. Thus, the heat-conducting element can advantageously have a good thermal conductivity. The ceramic layer of the AM B substrate is brazed to the copper layer by means of a solder paste.

In a preferred embodiment, the circuit carrier has at least one further electrically insulating layer, wherein at least one electrically conductive layer of the circuit carrier and the heat-conducting element enclose the further electrically insulating layer between one another. The heat-conducting element is connected in a thermally conductive manner by means of at least one thermally conductive metal bridge led through the further electrically insulating layer to the electrically conductive layer. The thermally conductive metal bridge is preferably formed by a particular galvanically generated via. Thus, the circuit carrier can advantageously be formed by laminating several prepreg layers. The aforementioned electrically conductive layer, which is connected to the heat-conducting element, in particular a partial element of the heat-conducting element, by means of the metal bridge, in particular cohesively, preferably extends parallel to a surface of the heat-conducting element facing the electrically conductive layer.

In a preferred embodiment of the circuit carrier, the metal bridge is formed by a particular galvanically generated via. In another embodiment, the via is produced by thermal spraying, in particular plasma spraying, or HVOF spraying (HVOF = high-velocity oxy-fuel). So the metal bridge can advantageously be arranged in an opening formed in the electrically insulating layer.

In an advantageous embodiment, the electrically conductive layer has a recess or an opening for the heat-conducting element. The heat-conducting element is advantageously passed through the electrically conductive layer and extends up to a surface of the electrically conductive layer. Thus, the circuit carrier need advantageously have no aforementioned metal bridge, which is designed to connect the heat-conducting element, in particular at least one sub-element of the heat-conducting element with the electrically conductive layer thermally conductive.

In a preferred embodiment of the circuit carrier, the connection layer is formed by a heat-conducting adhesive. The heat-conducting adhesive preferably has epoxy resin or a silicone elastomer as adhesive matrix.

More preferably, the heat-conducting adhesive particles, in particular

Ceramic particles. The ceramic particles are preferably boron nitride particles or aluminum oxide particles or boron carbide particles. Thus, the heat-conducting element can advantageously be produced at low cost.

The invention also relates to a connection arrangement comprising a circuit carrier according to the above-described type. The connection arrangement has at least one semiconductor component connected to the electrically conductive layer, more preferably the connection arrangement has a heat sink, in particular a heat sink or a heat spreading element. The circuit carrier is thermally conductively connected to the heat sink on a side of the circuit carrier facing away from the semiconductor component. Thus, the heat loss can advantageously from the semiconductor device, in particular power semiconductor device, are transported to the heat sink, formed by the heat sink, wherein the semiconductor device is electrically isolated from the heat sink. The semiconductor device and the heat sink are each connected to the circuit carrier, for example, soldered, and arranged on opposite sides of the circuit substrate. The invention also relates to a method for dissipating heat loss from a semiconductor component through a circuit carrier, in particular a circuit carrier according to the above-described type, to a heat sink, in particular a heat sink. In the method, the heat loss from the semiconductor device to a connected to the semiconductor device, in particular solder-bonded, electrically conductive layer is passed. Furthermore, the heat loss is in particular passed through at least one thermally conductive metal bridge through at least one electrically insulating layer and led to an embedded in the at least one electrically insulating layer, with the metal bridge cohesively connected heat conducting element. Furthermore, the heat loss from the heat-conducting element is released via at least one further metal bridge to a further electrically conductive layer and from there to the heat sink, in particular a heat sink.

Preferably, the heat-conducting element has at least two sub-elements each formed by a metal body and interconnected via an electrically insulating connection layer, wherein one sub-element is connected to the metal bridge and the other sub-element of the two sub-elements is thermally conductively connected to the further metal bridge, so that the heat loss from the Semiconductor device can flow through the connection layer to the heat sink.

The invention will now be explained below with reference to figures and further embodiments. Further advantageous embodiments will become apparent from the features described in the figures and in the dependent claims.

Figure 1 shows an embodiment of a method step for producing a multilayer circuit substrate, in which an opening is punched into the circuit substrate;

FIG. 2 shows the circuit carrier shown in FIG. 1, in which a heat-conducting element is inserted into the aperture in a further method step; FIG. 3 shows the circuit carrier produced in FIG. 2, comprising the heat-conducting element;

FIG. 4 shows the circuit carrier illustrated in FIG. 3, in which the heat-conducting element is connected to an electrically conductive layer of the circuit carrier via metal bridges guided through an electrically insulating layer;

Figure 5 shows a connection arrangement comprising the circuit carrier shown in Figure 4, wherein the circuit carrier is connected to a heat sink and a semiconductor device;

FIG. 6 shows the circuit carrier illustrated in FIG. 4 in a plan view;

FIG. 7 shows a variant of a connection arrangement with a circuit carrier, in which the heat-conducting element extends through at least one outer electrically conductive layer and terminates with a surface of the electrically conductive layer.

FIG. 1 shows an exemplary embodiment of a method step for producing a multilayer circuit carrier. In the method step shown in FIG. 1, in a part of the circuit carrier comprising an electrically insulating layer 2, on a surface area 24 which is smaller than a surface area of the electrically insulating layer 2, by means of a punching tool 23 or a drilling tool, not shown in FIG creates a recess or a breakthrough.

In the example shown in FIG. 1, the electrically insulating layer 2 is connected to further electrically conductive layers 5, 6, 7 and 8, thus forming a core of a multilayer circuit carrier. FIG. 2 shows a method step, wherein a heat-conducting element 12 is inserted into the opening 9 previously produced in the method step shown in FIG. The heat-conducting element 12 has two partial elements 13 and 14, which are each connected to one another in a heat-conducting manner by means of a connecting layer 15 and are electrically insulated from one another.

FIG. 3 shows the part of the circuit carrier shown in FIGS. 1 and 2, the heat-conducting element 12 being inserted into the opening 9 shown in FIG.

FIG. 4 shows the circuit carrier 1. In a further method step, the circuit carrier 1 has an electrically insulating layer 3 laminated to the part of the circuit carrier shown in FIG. Furthermore, at least one via, in this exemplary embodiment three vias are generated in the electrically insulating layer 3, of which one via 16 is designated by way of example. The vias are formed in this embodiment in each case by a - in particular cylindrical - metal bridge.

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

On an electrically insulating layer 2 facing away from the electrically insulating layer 3 side of an electrically insulating layer 4 is connected to the electrically insulating layer 2 by means of lamination. In the electrically insulating layer 4, at least one via, in this embodiment three vias, are formed, of which one via 17 is designated by way of example. The vias, such as the via 17, are each formed by a metal bridge, for example produced by electroplating or thermal spraying. The vias, such as the via 17, are thermally conductively and electrically conductively connected to the subelement 14. The vias, such as via 17, are connected to an electrically conductive layer 1 1, which is connected to the electrically insulating layer 4. The electrically conductive layers 10 and 11 are each thermally connected to a sub-element of the heat-conducting element 12 and electrically insulated from each other. With the circuit carrier 4, a semiconductor component can be soldered onto the electrically conductive layer 10 and a heat sink can be soldered onto the electrically conductive layer 11 as a heat sink.

FIG. 5 shows a connection arrangement in which the circuit carrier 1 is solder-bonded to a semiconductor component 21 and to a heat sink formed by a heat sink 20. The electrically conductive layer already shown in FIG. 4 is connected to the semiconductor component 21 by means of a soldering agent layer 18. The semiconductor component 21 is formed, for example, by a diode, a semiconductor switch, in particular a field-effect transistor. The semiconductor switch is formed for example by a housing-less semiconductor switch, also called Bare-Die, or by a housed semiconductor switch.

The heat sink 20 is formed in this embodiment by a copper block. In the copper block fluid channels are formed, of which a fluid channel 22 is exemplified. The heat sink 20 is connected in this embodiment by means of a Lotmittelschicht 19 with the electrically conductive layer 1 1. The heat sink 20 is arranged on the circuit carrier 1 opposite to the semiconductor component 21, so that loss heat 25 generated by the semiconductor component 21 from the semiconductor component 21 via the solder agent layer 18, the electrically conductive layer 10, the vias such as the via 16 to the subelement 13 of the heat conduction element 12 can flow. Furthermore, the heat loss 25 can flow via the connection layer 15 to the subelement 14 and from there flow via the vias, such as via 17, to the electrically conductive layer 11 and from there via the solder layer 19 to the heat sink 20 as heat sink. The heat loss can be dissipated in the heat sink 20 via a cooling fluid, for example cooling water, guided in the fluid ducts, such as the fluid duct 22. The heat sink 20 may have instead of the fluid channels cooling fins, which are designed to dissipate the heat loss 25 by convection.

FIG. 6 shows the circuit carrier 1 already shown in FIG. 3 in an upright view. The surface area 24 of the heat-conducting element 12 is smaller than the surface area of the electrically insulating layer 2 in a flat extension of the circuit carrier.

FIG. 7 shows a variant of the connection arrangement already shown in FIG. The connection arrangement according to FIG. 7 has a circuit carrier 26 which is connected to the semiconductor component 21 by means of a solder agent layer 18 and to the heat sink 20 by means of a solder agent layer 19. In the exemplary embodiment shown in FIG. 4, the circuit carrier 26 has a multilayer structure and comprises an electrically insulating layer 2 inside, further electrically conductive layers 5, 6, 7 and 8 connected to the electrically insulating layer 2 and two further, the electrically insulating layer 2 between one another enclosing, electrically insulating layers 3 and 4. The electrically insulating layer 3 is connected to an electrically conductive layer 10 and the electrically insulating layer 4 is connected to an electrically conductive layer 11. The electrically conductive layers 10 and 1 1 thus include the aforementioned electrically insulating layers 2, 3 and 4 and the electrically conductive layers 5, 6, 7 and 8 - in particular in the manner of a sandwich - between each other. In accordance with the method step shown in FIG. 1, a recess, in this exemplary embodiment an opening 27, can be produced in the circuit carrier 26 thus formed by means of a punching tool 23 or by means of a drilling tool. The heat-conducting element 12 can then be inserted into the opening 27 in accordance with the method step shown in FIG. In the exemplary embodiment shown in FIG. 7, the heat-conducting element 12 has the same thickness direction 28 as the multilayer circuit carrier 26.

In this exemplary embodiment, the semiconductor component 21 extends both over the subelement 13 and over a portion of the electrically conductive layer 10. The semiconductor component 21 is thus solder-bonded by means of the solder agent layer 18 to the electrically conductive layer 10 and to the subelement 13. In this exemplary embodiment, the semiconductor component 21 has an electrical connection, which is formed by 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 solder agent layer 18 and is electrically and thermally conductively connected to the partial element 13 via the solder layer 18, so that loss heat 25 generated by the semiconductor component 21 can be released to the component element 13. The heat loss 25 can be delivered via the electrically insulating connection layer 15 to the sub-element 14 and from there via the solder layer 19 to the heat sink 20. The heat sink 20 is formed for example by a copper heat sink or by an aluminum heat sink. The partial elements 13 and 14 are each formed by a metal block, for example a copper block or aluminum block.

Claims

claims

1. 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, 1 1), wherein the circuit carrier (1, 26) at least one in a thermally conductive heat-conducting element (12) embedded in the electrically insulating layer (2), which is designed to transport waste heat (25) transversely to a flat extent of the circuit carrier (1, 26);

characterized in that

the heat-conducting element (12) has at least two sub-elements (13, 14) each formed by a metal body and an electrically insulating connecting layer (15), wherein the connecting layer (15) is arranged and formed between the sub-elements (13, 14), the sub-elements (13, 14) to electrically isolate each other and to connect with each other thermally conductive.

2. circuit carrier (1, 26) according to claim 1,

characterized in that

the connecting layer (15) is a self-adhesive plastic layer.

3. circuit carrier (1, 26) according to claim 1,

characterized in that

the bonding layer (15) is a ceramic layer.

4. circuit carrier (1, 26) according to claim 3,

characterized in that

the heat-conducting element (12) is a direct-bonded-metal substrate, in which the partial element is eutectically connected to a ceramic connecting layer.

5. circuit carrier (1, 26) according to claim 3,

characterized in that

the heat-conducting element (12) is a high-temperature cofired ceramics substrate.

6. circuit carrier (1) according to one of the preceding claims,

characterized in that

at least one electrically conductive layer of the circuit carrier and the heat-conducting element a further electrically insulating layer (3, 4)

between each other, wherein the heat-conducting element (12) by means of at least one through the further electrically insulating layer (3, 4) passed through thermally conductive metal bridge (16, 17) is thermally conductive connected to the electrically conductive layer (10, 11).

7. circuit carrier (1) according to claim 6,

characterized in that the metal bridge (16, 17) is formed by a via.

8. circuit carrier (16, 17) according to one of the preceding claims,

characterized in that

the connecting layer (15) is formed by a heat-conducting adhesive.

9. Connecting arrangement with a circuit carrier (1) according to one of the preceding claims 1 to 8,

wherein the connection arrangement has at least one semiconductor component (21) connected to the electrically conductive layer and the circuit carrier (1) is thermally conductively connected to a heat sink (20) on a side of the circuit carrier (1) facing away from the semiconductor component (21).

10. A method for dissipating heat loss (25) from a semiconductor component (21) through a circuit carrier (1) to a heat sink (20), in particular by the circuit carrier according to one of the preceding claims 1 to 8,

in which the loss of heat (25) from the semiconductor component (21) is conducted to a, in particular solder-bonded, electrically conductive layer (10) connected to the semiconductor component (21) and in particular via at least one thermally conductive metal bridge (16) by at least one electrically insulating layer (16). 2, 3) is passed and to a in the at least one electrically insulating layer (2, 3) embedded, with the metal bridge (16) cohesively connected heat conducting element (12) is guided, and by the heat conducting element (12) via at least one further metal bridge (17) to a further electrically conductive layer (11) and from there to the heat sink (20) is discharged, wherein the heat-conducting element (12) at least two each by a Me- comprising partial bodies (13, 14) which are formed by tall body and are interconnected via an electrically insulating connecting layer (15), one partial element (13) being connected to the metal bridge (16) and the other partial element (14) of the two partial elements (13, 14) is thermally conductively connected to the further metal bridge (17), so that the heat loss (25) from the semiconductor device (21) through the connection layer (15) can flow through the heat sink (20).