DE102018111534A1 - Device for dissipating heat from a printed circuit board - Google Patents

Abstract

The invention relates to a device (1) for removing heat from a printed circuit board (2) having a printed circuit board (2) which has at least one electrical component (10) arranged on a surface (6) of the printed circuit board (2) above the printed circuit board (2) arranged cooling element (15) for dissipating heat to the ambient air or a cooling medium, which has a flat bottom and at least one heat conducting element (12) for dissipating heat from the printed circuit board (2) to the cooling element (15 ), wherein the cooling element (15) with a top side (21) of the heat conducting element (12) is thermally conductively connected, wherein the top (21) of the heat conducting element (12) and the top of the device (10) at an identical distance from the surface (6 ) of the printed circuit board (2) are arranged so that the cooling element (15) is also thermally conductively connected to the upper side of the component (10).

Description

The invention relates to a device for dissipating heat from a printed circuit board with a printed circuit board having at least one arranged on a surface of the printed circuit board electrical component, with at least one arranged above the circuit board cooling element for dissipating heat to the ambient air or a cooling medium, which having flat bottom and with a heat conducting element for dissipating heat from the circuit board to the cooling element, wherein the cooling element is thermally conductively connected to an upper side of the heat conducting element.

Such a device with a printed circuit board, on whose surface a plurality of components are arranged, is for example from the EP 0 989 794 A2 known. This device has a plurality of heat conducting elements, which are arranged and soldered on the surface of the circuit board similar to the components. The heat-conducting elements are so far upwards from the circuit board and project in height all arranged on the circuit board components. On the upper sides of the heat-conducting a plate-shaped cooling element is thermally conductively connected to the heat-conducting elements. Via the cooling element, the heat dissipated from the printed circuit board via the heat conducting elements can be released to the ambient air.

However, it has been found in practice that heat build-up in the printed circuit board can occur, especially in power electronic printed circuit boards which switch and / or guide high currents. As a result, the functionality of the components can be impaired.

Against this background, the task arises to improve the cooling of a power electronic circuit board.

In a device of the type mentioned is proposed to solve the problem that the top of the heat conducting element and the top of the device are arranged at an identical distance from the surface of the circuit board, so that the cooling element is thermally conductively connected to the top of the device.

According to the invention, the height of the heat-conducting element above the printed circuit board is adapted to the height of the component above the printed circuit board, so that the distances of the upper side of the heat-conducting element and the upper side of the component from the surface of the printed circuit board are identical. By identical distances are meant distances whose difference is less than 1 mm, preferably less than 0.5 mm, particularly preferably less than 0.1 mm. This makes it possible that the flat underside of the cooling element can be in both thermally conductive contact with the top of the heat conducting element as well as in heat-conducting contact with the top of the device. Heat can be dissipated from the component upwards into the cooling element via the heat-conducting connection between component and cooling element. The amount of heat dissipated through the top of the device reduces the heat that must be dissipated through the circuit board to facilitate cooling of the circuit board.

The heat-conducting element preferably comprises copper or aluminum or brass, in particular CuZn40Al2 or CuZn39Pb3, or phosphor bronze. In this way, a light, easily solderable heat-conducting element can be obtained, which has a high thermal conductivity. Particularly preferably, the heat conducting element is formed of copper and tinned, for example, to improve the solderability and protection against corrosion. Alternatively, the heat-conducting element can be formed from copper-plated and / or tinned aluminum. Further alternatively, the heat-conducting element is made of, in particular tinned, brass.

Other alternatives provide that the heat-conducting element of CuZn40AI2 or CuZn39Pb3 or, in particular tinned, phosphor bronze is formed.

Heat can be dissipated to the ambient air or in particular a liquid cooling medium via the cooling element. Preferably, the cooling element is connected to at least one guide element, for example a pipe or a hose, or a heat exchanger or compressor. The cooling element may be formed as a cooling plate or as a heat sink or as a heat pipe. Such Wärmableitelemente or heat pipes can dissipate heat to a heat sink or another cooling plate.

According to an advantageous embodiment, it is provided that an underside of the heat-conducting element which lies opposite the upper side rests on the surface of the printed circuit board, so that the loading of the printed circuit board with the heat-conducting element can take place in the manner of an SMD (Surface Mounted Device) component. The heat-conducting element and the printed circuit board, in particular a conductor or a conductor pad of the printed circuit board, are preferably connected to the underside of the heat-conducting element via a solder connection.

Preferably, the underside of the heat-conducting element has a plurality of depressions. About the wells, the interface between the bottom of the heat conducting element and a solder, in particular a solder paste can be increased. The Recesses also allow gases and solvents resulting from brazing inside the braze to be removed more efficiently, thus reducing the risk of undesirable gas inclusions at the interface between the heat conduction member and the braze. Particularly preferably, the underside has a plurality of parallel grooves. Such depressions can be manufactured inexpensively. Alternatively, the recesses may be formed as punctiform recesses in the bottom, which for example have a round or polygonal cross-section.

Alternatively or additionally, it is preferred if a contact surface of the printed circuit board, on which the underside of the heat-conducting element rests, has a plurality of depressions, in particular, a plurality of bores. The depressions in the printed circuit board can be configured, for example, as "blind vias", in particular in a conductor or in a printed circuit board of the printed circuit board. Through these recesses in the circuit board, the interface between the printed circuit board and solder can be increased and space for receiving unwanted Lotproducts, for example, when soldering gases produced, created.

The underside of the upper side of the heat-conducting element is preferably flat, so that the flat underside of the heat sink can lie flat against this.

According to an advantageous embodiment, it is provided that the printed circuit board has an insert element arranged within the printed circuit board, which is connected in a heat-conducting manner to the heat-conducting element. The insert element can be designed, for example, as a copper inlay. Preferably, the insert element extends parallel to the surface of the circuit board. For example, the insert element may be plate-shaped. The insert element preferably has a thickness in a direction perpendicular to the surface of the printed circuit board, which is greater than 1 mm, in particular in the range of 2 mm to 5 mm. The insert element may be a prefabricated insert element that is inserted into the printed circuit board or pressed or cast. The insert element is preferably connected in a heat-conducting manner to the conductor tracks, for example metallized vias, which run perpendicular to the surface of the printed circuit board, to the heat-conducting element arranged on the surface.

In this context, it has proven to be an advantageous embodiment, in which on the upper side of the circuit board, a reaching to the insert element recess is arranged and the heat-conducting element is arranged in the recess. The recess may form a window in the surface, which allows the contacting of the insert element arranged within the printed circuit board. In this respect, the underside of the heat-conducting element can be arranged below a plane of the surface of the printed circuit board. The heat-conducting element and the insert element are preferably connected via a solder connection.

According to an advantageous embodiment, the heat-conducting element has on its underside a plurality of pins which are each arranged in a recess in the printed circuit board. Via the pins, the dissipation of heat from the circuit board in a direction perpendicular to the surface of the circuit board can be improved. The recess may be formed as a blind hole or through hole, in particular blind hole or through hole.

Preferably, the pins extend from a surface on an upper side of the printed circuit board to a surface on an underside of the printed circuit board and stand out of the printed circuit board at the lower side. Optionally, the pins on the underside may be connected to the circuit board via a solder connection.

It is preferred if the pins are connected via a press fit with the circuit board, so that a solder joint for fastening and heat-conducting connection of the heat-conducting element is not absolutely necessary. The cross-section of the pins and the corresponding recess may be selected such that an edge of a pin cuts into a printed circuit or a metallized via of the printed circuit board during pressing, so that an electrical and / or heat-conducting connection between the pin and the printed circuit or Via is made. The pins of the heat-conducting element may have a different cross-section than the respective recess into which the pins are inserted. Preferably, the pins have a cross section with a plurality of edges, which incise when inserting the pins in the recesses in an inner wall of the respective recess. The recesses may have a round cross-section. For example, the cross section of the pins may be polygonal, in particular quadrangular, pentagonal, hexagonal, heptagonal or octagonal.

It has proved to be particularly advantageous if the pins have a star-shaped cross section. In this way, a cross section of the pins can be obtained, for example, with acute edge angles, which can be pressed into the inner wall of the respective recess improved.

An advantageous embodiment provides that the heat-conducting element has a resting on the surface of the circuit board support member and the pins of the heat-conducting element are formed as separate from the support member pins. hereby can be made possible on a cost-effective production of the Wärmeleitelements in which a chipping or milling of the pins and the support member is not required as a monolithic part.

According to a preferred embodiment, a heat-conducting, electrically insulating insulating element is arranged between the upper side of the heat-conducting element and the underside of the cooling element. About the insulating element, the cooling element can be galvanically isolated from the heat conducting element. The insulating element may be formed as a plate or as a foil. Preferably, the thickness of the plate is in the range of less than 2 millimeters. An insulating element formed as a film advantageously has a thickness in the range of 10 to 900 micrometers, preferably in the range of 20 to 100 micrometers.

Preferably, the circuit board has a conductor track which is electrically conductively connected to the heat-conducting element, wherein the conductor track does not conduct an electrical signal and is electrically insulated from all signal-carrying conductor tracks of the printed circuit board. About an interconnect in the manner of an island insulation of the heat-conducting element and the cooling element relative to the conductor tracks of the circuit board and / or against a liner element of the circuit board can be made possible, wherein the insulation is provided in the circuit board. It is possible to lay the most necessary electrical isolation between electronics to be cooled and / or printed circuit board and the cooling element in the circuit board. Galvanic separations, also referred to as insulation, are usually a bottleneck in refrigeration systems because, on the one hand, high thermal but low electrical conductivity is required. The very effective in many conductors electronic thermal conductivity can not be used accordingly and appropriate insulation materials must resort to other Wärmeleitmechanismen, such as phononic heat conduction. On a thermally conductive but electrically insulating plate, pad or alternatively a film, which are usually a thermal and electrical compromise but conventionally required for galvanic isolation, can even be dispensed with. Instead, the galvanic isolation can take place in that the conductor track on the circuit board, to which the heat conducting element in the sense of the invention electrically and thermally contacted, is isolated from other conductor tracks of the circuit board, in particular of such traces, the signals lead to which a galvanic Separation is desired. It is thus possible to use for isolation methods and procedures that are provided in the PCB process. For isolation from other conductors on other levels or Metallisierungslagen the circuit board, the printed circuit board material, usually usually FR4 , for example in the form of a resin preimpregnated fabric mat (known to those skilled in the art as a prepreg layer) or core material. The galvanic isolation to other interconnects on the same level or metallization of the circuit board can also be done by PCB design methods, in particular the maintenance of distances and the introduction of milling. Distances of the tracks on the circuit board to which the heat-conducting electrically and thermally contacted in the context of the invention, to other tracks can accordingly very easily according to the rules and distances known to those skilled in the art for creepage distances and isolation distances in circuits according to Standard EN 60664-1: 2007 respectively. A reduction of the necessary distances can also be obtained by coating the plane with insulating materials, for example polyurethanes, epoxies, silicones and similar plastics. An electrical insulation on the circuit board can be made much more controlled and thinner than in a film, a pad or plate between two mostly mechanically not directly connected, but mostly held together by pressure surfaces according to the prior art, the or thus usually also must compensate for geometric tolerances. Accordingly, a much lower thermal resistance is possible because the heat resistance decreases approximately with decreasing thickness. Furthermore, in the case of an insulation on the printed circuit board for the insulation, materials with higher thermal conductivity, for example materials filled with high ceramic concentrations, which would be too brittle for films, pads and the like in the prior art, can be used.

In a direction parallel to the surface of the circuit board, the electrically conductive connected to the heat conducting element conductor track may have a distance in the manner of a creepage distance from the other conductor tracks. In a direction perpendicular to the surface of the circuit board may also be provided a distance from the other conductor tracks.

Preferably, the heat-conducting element is thermally conductive and / or electrically connected to a plurality of first interconnects in different levels of the circuit board, wherein between the first interconnects a plurality of second interconnects are arranged, which are electrically isolated from the first interconnects. In this respect, a comb-like structure of the printed conductors is preferably formed in the cross section of the printed circuit board. This comb-like cross-sectional structure increases the heat-conducting but electrically insulating interface between the first and the second conductor tracks, so that the heat transfer between the first and second conductor tracks is increased and the first and second conductor tracks are galvanically separated from one another. in the In contrast to the prior art, when the insulation in the printed circuit board is formed, the cross-sectional area of the insulation over which the heat flow must flow can be systematically increased. While according to the prior art surfaces of the cooling element and element to be cooled are generally limited, the electrically insulating surface over which the heat flow must flow, for example, by a geometrically interlocking but electrically isolated vertical or horizontal shaping of the insulation in the circuit board Comb structures of the metallization on the circuit board, to which the heat conduction electrically and thermally contacted, and at least one other metallization be increased by orders of magnitude. The thermal resistance, which is inversely proportional to the size of the cross section of the heat flow, thus decreases.

Preferably, the first interconnects and the second interconnects are arranged overlapping, so that the first interconnects and the second interconnects form an overlapping surface arranged parallel to the surface of the circuit board.

An embodiment has proven to be advantageous in which the printed circuit board has a substrate and at least partially disposed in the substrate particles of a ceramic material, for example ZnO, Ti2O5, ZrO2. Such particles can at least partially increase the phononic thermal conductivity of the substrate.

According to an advantageous embodiment it is provided that the conductor has a distance from all signal-carrying conductor tracks of the printed circuit board, which is less than 150 microns, more preferably less than 100 microns; or that the first interconnects have a distance from the second interconnects which is less than 150 μm, more preferably less than 100 μm.

According to an advantageous embodiment, it is provided that a heat-conducting tolerance compensation element is arranged between the upper side of the heat-conducting element and the underside of the cooling element. The tolerance compensation element can be configured as a pad, foil, plate or as a heat-conducting paste. Such a configuration is particularly advantageous when the insulation between the heat conducting element and the cooling element is realized in the circuit board. About the tolerance compensation element, a geometric tolerance compensation of the transition between the heat conducting element and the cooling element can be made possible, for example, but not necessarily exclusively by an elasticity of the material. It is not necessary that the tolerance compensation element is designed to be electrically insulating.

• 1 ein erstes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer Schnittdarstellung;
• 2 ein zweites Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer Schnittdarstellung;
• 3 ein drittes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer Schnittdarstellung;
• 4 ein erstes Ausführungsbeispiel eines Wärmeleitelements in einer perspektivischen Darstellung;
• 5 weitere Ausführungsbeispiele von Wärmeleitelementen in einer Ansicht von unten;
• 6 weitere Ausführungsbeispiele von Wärmeleitelementen in einer Schnittdarstellung;
• 7 ein viertes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer Schnittdarstellung;
• 8 ein erstes Ausführungsbeispiel eines Stifts eines Wärmeleitelements und einer entsprechenden Ausnehmung in der Leiterplatte in einer schematischen Schnittdarstellung;
• 9 ein zweites Ausführungsbeispiel eines Stifts eines Wärmeleitelements und einer entsprechenden Ausnehmung in der Leiterplatte in einer schematischen Schnittdarstellung;
• 10 weitere Ausführungsbeispiele von Stiften eines Wärmeleitelements in einer perspektivischen Darstellung;
• 11 ein fünftes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer Schnittdarstellung;
• 12 verschiedene Ausführungsbeispiele von separat ausgebildeten Stiften des Wärmeleitelements in einer perspektivischen Darstellung;
• 13 ein sechstes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer perspektivischen Explosionsdarstellung;
• 14 ein Detail eines siebten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer perspektivischen Darstellung; und
• 15 ein Detail eines achten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer perspektivischen Darstellung;
• 16 ein neuntes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer perspektivischen Explosionsdarstellung;
• 17 ein Detail eines neunten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer perspektivischen Darstellung;
• 18 ein Detail eines neunten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer perspektivischen Darstellung;
• 19 ein zehntes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer perspektivischen Explosionsdarstellung;
• 20 ein Detail eines zehnten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer perspektivischen Darstellung;
• 21 ein Detail eines zehnten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer perspektivischen Darstellung;
• 22 ein Detail eines zehnten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer perspektivischen Darstellung;
• 23 ein elftes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer Schnittdarstellung;
• 24 ein Detail eines elften Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer perspektivischen Darstellung;
• 25 ein zwölftes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung in einer Schnittdarstellung.

Further details and advantages of the invention will be explained below with reference to the embodiments illustrated in the figures. Hereby shows:

• 1 a first embodiment of a device according to the invention in a sectional view;
• 2 a second embodiment of a device according to the invention in a sectional view;
• 3 a third embodiment of a device according to the invention in a sectional view;
• 4 a first embodiment of a Wärmeleitelements in a perspective view;
• 5 further embodiments of Wärmeleitelementen in a view from below;
• 6 further embodiments of Wärmeleitelementen in a sectional view;
• 7 A fourth embodiment of a device according to the invention in a sectional view;
• 8th a first embodiment of a pin of a Wärmeleitelements and a corresponding recess in the circuit board in a schematic sectional view;
• 9 a second embodiment of a pin of a Wärmeleitelements and a corresponding recess in the circuit board in a schematic sectional view;
• 10 further embodiments of pins of a Wärmeleitelements in a perspective view;
• 11 a fifth embodiment of a device according to the invention in a sectional view;
• 12 various embodiments of separately formed pins of the heat conducting element in a perspective view;
• 13 a sixth embodiment of a device according to the invention in a perspective exploded view;
• 14 a detail of a seventh embodiment of a device according to the invention in a perspective view; and
• 15 a detail of an eighth embodiment of a device according to the invention in a perspective view;
• 16 a ninth embodiment of a device according to the invention in an exploded perspective view;
• 17 a detail of a ninth embodiment of a device according to the invention in a perspective view;
• 18 a detail of a ninth embodiment of a device according to the invention in a perspective view;
• 19 A tenth embodiment of a device according to the invention in an exploded perspective view;
• 20 a detail of a tenth embodiment of a device according to the invention in a perspective view;
• 21 a detail of a tenth embodiment of a device according to the invention in a perspective view;
• 22 a detail of a tenth embodiment of a device according to the invention in a perspective view;
• 23 an eleventh embodiment of a device according to the invention in a sectional view;
• 24 a detail of an eleventh embodiment of a device according to the invention in a perspective view;
• 25 a twelfth embodiment of a device according to the invention in a sectional view.

The sectional view in 1 shows a first embodiment of a device according to the invention 1 for dissipating heat from a circuit board 2 , which is designed as a power electronic circuit board. The circuit board 2 has a substrate 5 made of an electrically insulating material. The substrate may be composed of an epoxy resin and glass fiber-containing composite material, for example, a FR-4 composite material. Inside the circuit board 2 , on the surfaces 6 the top and the surface 7 the bottom of the circuit board 2 are several tracks 3 made of an electrically conductive material, in particular of copper. About these tracks 3 Power electronic signals are led. The tracks 3 are on different layers of the circuit board 2 arranged parallel to the surfaces 6 . 7 the circuit board 2 run. In a direction perpendicular to the surfaces 6 . 7 the circuit board are the tracks 2 electrically via vias 4 connected.

On the surfaces 6 . 7 the printed circuit board are several electrical components 10 arranged. The components 10 can be designed as power electronic switches, for example, as metal oxide (MOSFETs) or as IGBTs (insulated gate bipolar transistor). Alternatively or additionally, components may be used 10 be provided, which are designed as passive components, for example as a resistor, capacitor or inductor. The components 10 are formed as SMD components by means of surface mounting (SMT, surface mounting technology) on one of the surfaces 6 . 7 the circuit board are soldered.

During operation of the power electronic circuit board 2 in particular by the switching of the components 10 Heat energy released, which must be dissipated to the environment, to overheat the components 10 to prevent. The heat conduction takes place, inter alia, via the with the respective component 10 connected interconnects 2 and vias 4 as well as through the substrate 5 the circuit board 2 , In 1 is an exemplary heat path indicated by several arrows W.

For discharging the heat to the ambient air or a cooling medium, the device has a cooling element 15 on top of a surface 6 the circuit board is arranged. The cooling element 15 may be formed, for example, as a cooling plate. It indicates at its the circuit board 2 facing bottom on a flat surface.

To create a thermally conductive connection between the circuit board 2 and the cooling element 15 To obtain, are several heat conducting elements 12 for dissipating heat from the circuit board 2 to the cooling element 15 intended. The underside of the cooling element 15 is this with an upper side of the heat conducting elements 12 thermally conductive connected. Between the top of the heat conducting element 12 and the underside of the cooling element 15 is a heat-conducting, electrically insulating insulating element 14 arranged, which is designed as a thin plate or as a foil.

To allow for improved dissipation of heat, are the top of the heat conducting element 12 and the top of a device 10 on the surface 6 the circuit board 2 at an identical distance from the surface 6 the circuit board 2 arranged. This can be achieved that the cooling element 15 also with the top of the device 10 is thermally conductively connected. Are several components of different height on the circuit board 2 provided, where is preferred, the height of the heat conducting element 2 chosen such that the top of the highest component 10 on the surface 6 the circuit board 2 at an identical distance from the surface 6 the circuit board 2 is arranged. The height of the components 10 or the height of the top of the Wärmeleitelemente above the surface 6 is preferably in a range between 1 millimeter and 10 millimeters, and more preferably between 1 millimeter and 5 millimeters.

According to the first embodiment, the heat-conducting elements 12 designed as SMD components. The underside of the heat-conducting elements 12 lies on the surface 6 the circuit board 2 on and is with this over a solder joint 13 connected. The solder joint can be produced for example by means of reflow soldering or wave soldering.

This in 2 shown second embodiment of a device 1 for dissipating heat from a circuit board 2 is similar to the first embodiment, so that the explanations to the first embodiment also apply to the second embodiment. In contrast to the first embodiment, which has the circuit board 2 according to the second embodiment, a within the circuit board 2 arranged insert element 8th on, which conducts heat with the heat conducting element 12 connected is. The insert element 8th is as a prefabricated insert element 8th , in particular as a copper-containing insert element, configured and in the substrate 5 poured or pressed. The on the surface 6 arranged heat conducting element 12 is over several vias 4 thermally conductive with the insert element 8th connected. The vias 4 connect the insert element 8th electrically and thermally conductive with a designed as a pad trace 3 on the surface 6 the circuit board 2 , with which the heat-conducting element 12 via a solder joint 13 connected is.

This in 3 shown third embodiment of a device 1 for dissipating heat from a circuit board 2 is similar to the second embodiment, so that the explanations to the second embodiment also apply to the third embodiment. Unlike the second embodiment, in the third embodiment, at the top 6 the circuit board 2 one to the insert element 8th reaching recess 9 arranged. The heat-conducting element 12 is in this recess 9 arranged and electrically and thermally conductively connected to the insert element. The underside of the heat-conducting element 12 is therefore below the plane of the surface 6 the circuit board 2 arranged. The heat-conducting element 12 and the insert element 8th are preferably connected via a solder joint. In this embodiment, there are no vias between the insert element 8th and the heat conducting element 12 required. The heat-conducting element 12 has a height that is greater than the height of the particular largest component 10 on the surface 6 the circuit board 2 , In this respect, the top of the heat conducting element 12 and the top of the device 10 also in this embodiment at an identical distance from the surface 6 the circuit board 2 arranged.

Based on the illustrations in 4 . 5 and 6 are different embodiments of Wärmeleitelementen 12 to be explained in the embodiments according to 1 . 2 and 3 Application can be found.

The representation in 4 shows a heat conducting element 12 with a flat top 21 , The bottom 22 the Wärmeleitelements has depressions 23 on, which are designed as parallel grooves. The grooves extend parallel to a side edge of the heat-conducting element 12 , Through the depressions 23 becomes the interface between the bottom 22 the Wärmeleitelements 12 and a solder, in particular a solder paste, enlarged. The wells 23 also allow gases generated during soldering inside the solder to be dissipated in an improved manner. Alternatively, a contact surface of the circuit board 2 on which the bottom 22 the Wärmeleitelements 12 rests, have a plurality of wells, in particular a plurality of holes.

In 5a is a top view on the bottom 22 a further embodiment of a heat conducting element 12 shown. The underside has wells designed as grooves which are parallel to a side edge of the heat-conducting element 12 are aligned.

The 5b shows a view of the underside 22 a further embodiment of a heat conducting element 12 in which depressions designed as parallel grooves 23 are provided which an acute angle with a side edge of the heat conducting element 12 include, in particular an angle in the range of 10 ° to 45 °.

In 5c is a top view on the bottom 22 a further embodiment of a heat conducting element 12 shown. The wells 23 are formed as parallel grooves and divided into several, in particular two, areas in which the recesses 23 have different orientations. The wells 23 in a first area are transverse to the depressions 23 arranged in a second area.

The 5d shows another view of the underside 2 an embodiment of a heat conducting element 12 , wherein punctiform depressions are provided with a round cross-section. The wells 23 For example, they may be formed as blind holes. The wells 23 can have a round, conical or angular depth profile.

In 6a is a cross section of an embodiment of a heat conducting element 12 which is a flat top 21 and a flat bottom 23 having. Inside the heat-conducting element 12 are provided for material and / or weight reduction internal recesses.

The 6b shows a cross section of an embodiment of a Wärmeleitelements 12 which is a flat top 21 and a bottom 23 with several recesses 23 having a rectangular depth profile.

The 6c shows a cross section of an embodiment of a Wärmeleitelements 12 which is a flat top 21 and a bottom 23 with several recesses 23 having a triangular depth profile.

In the 7 is a fourth embodiment of a device according to the invention 1 which is similar to the first embodiment, so that the explanations on the first embodiment also apply to the fourth embodiment. In contrast to the first embodiment, the heat conducting element 12 several pins on its underside 25 on, each in a recess 26 in the circuit board 2 are arranged. The pencils 25 are integral with a support part 25 the Wärmeleitelements 12 trained on the surface 6 the circuit board 2 rests. The pencils 25 run from the surface 6 on an upper side of the printed circuit board 2 up to the surface 7 on the bottom of the circuit board 2 and stand at the bottom of the circuit board 2 out of this. Optionally, the pins 25 on the surface 7 the bottom via a solder connection to the circuit board 2 , in particular with a conductor track 3 be electrically conductive and thermally conductively connected.

The pins are preferred 24 of in 7 shown heat conducting element 12 by means of interference fit with the circuit board 2 connected. As in 8th and 9 is shown is the cross section of the pins 24 and the corresponding recess 26 in the circuit board 2 chosen such that one or more edges of the pen 24 when pressed into a track 3 or a metallized via 4 the circuit board 2 cuts in and doing an electrical and / or thermally conductive connection between the pin 24 and the track 3 or the Via 4 will be produced. The cross section of the pen 24 is in each case designed differently than the cross section of the respective recess 26 into which the pen 24 is introduced. 8th shows a pen 24 with rectangular cross section, which is in a recess 26 is introduced with a round cross-section. 9 shows a pen 24 with a star-shaped cross section, which is in a recess 26 is introduced with a round cross-section.

In 10 are different star-shaped cross sections of pins 24 shown in the case of a heat-conducting element 12 can be used, which for mounting by means of interference fit in the circuit board 2 suitable is.

The 11 shows a fifth embodiment of a device 1 for dissipating heat from a circuit board 2 which is based on the fourth embodiment. The explanations on the fourth embodiment therefore apply to the fifth embodiment. In contrast to the fourth embodiment, the heat-conducting element 12 one on the surface 6 the circuit board 2 resting support part 25 on and the pins 24 the Wärmeleitelements 12 are as of the pad part 25 separate pens 24 educated. The separately formed pens 24 are in recesses in the support part 25 the Wärmeleitelements 12 driven.

12 shows different variants of separate pins 24 that with a device 1 Can be used according to the fifth embodiment. The pencils 24 each preferably have a conically shaped first end 27 , A second end 28 of the pens 24 that the conical, first end 27 opposite, may also be formed either conical or rectangular. The pencils 24 are preferred with the conical first end 27 in the circuit board 2 driven.

In 13 is a sixth embodiment of a device according to the invention 1 shown in a perspective exploded view. The device 1 includes a printed circuit board 2 , on the surface 6 several identical electrical components 10 , For example, MOSFETs or IGBTs are arranged. Furthermore, several heat conducting elements 12 on the surface 6 the circuit board 2 arranged. The tops of the heat-conducting elements 12 and the tops of the components 10 are at an identical distance from the surface 6 the circuit board 2 arranged so that through the tops of the heat conducting elements 12 and the components 10 a plane is formed on which a plate-shaped cooling element 15 is arranged. Optionally can be attached to the bottom of the cooling element 15 an Indian 13 Not shown insulating be provided that the cooling element 15 galvanic of the heat conducting element 12 separates, the cooling element 15 and the heat-conducting element 12 but connects thermally conductive.

The 14 shows a detail of a seventh embodiment of a device according to the invention 1 , Shown is the transition region between the circuit board 2 and a heat conducting element 12 , It can be seen that the circuit board 2 a trained as a pad trace 3 ' has, which is electrically conductive with the heat conducting element 12 connected is. This track 3 ' is on the surface 6 the circuit board 2 arranged, carries no electrical signal and is opposite to all the signal-carrying conductor tracks 3 the circuit board 2 electrically isolated. Towards the plane of the circuit board 2 is the one with the heat conducting element 12 contacted trace 3 ' by a first distance a from the signal-carrying conductor tracks 3 arranged away in a plane to the circuit board 2 vertical direction by a second distance b. In this respect forms the conductor track 3 ' one of the other tracks 3 galvanically isolated island, allowing isolation between heat conducting element 12 and cooling element 15 As in the six previous embodiments, is not required to provide electrical insulation of the heat sink 15 from the circuit board 2 to enable.

As shown in 14 becomes a bottom of the heat conducting element 12 via a solder joint with the electrically insulated conductor track 3 ' connected. According to a modification of this embodiment, it can be provided that the heat-conducting element 12 several pens 24 which, in recesses in the circuit board 2 are introduced. In such a modification must be below the electrically insulated conductor 3 ' in the circuit board 2 a sufficiently large space can be provided, in which no signal-carrying tracks 3 are arranged.

The distances between the non-signal-carrying track 3 ' and the signal-carrying tracks 3 are chosen to comply with the requirements of EN 60664-1: 2007, in particular with regard to the specified creepage distance (if the distance runs along a surface) and the specified clearances (if the distance does not run along a leading surface). In particular, these distances are in accordance with the specifications of Table F4 and the chapter 6.2 the standard EN 60664-1: 2007.

This in 15 shown eighth embodiment of a device 1 for dissipating heat from a circuit board 2 is similar to the seventh embodiment, so that the explanation of the seventh embodiment also applies to the eighth embodiment. According to 15 is the heat conducting element 12 thermally conductive and / or electrically conductive with a plurality of first conductor tracks 3 ' . 30 in different levels of the circuit board 2 connected. Between the first interconnects 3 ' . 30 are several second tracks 3 . 30 arranged electrically from the first tracks 3 ' . 30 are isolated. Between the first tracks 3 ' . 30 ' and the second tracks 3 . 30 planar heat conduction regions are formed, via which heat, for example, from the second conductor tracks 3 . 30 over the substrate 5 to first tracks 3 ' . 30 ' can be directed. This cross-sectional comb structure increases the heat-conducting but electrically insulating interface between the first and the second conductor tracks 3 . 3 ' . 30 . 30 ' , so that the heat transfer between the first and second conductor tracks 3 . 3 ' . 30 . 30 ' is enlarged and the first and second tracks 3 . 3 ' . 30 . 30 ' are galvanically separated from each other.

The devices described above 1 for dissipating heat from a circuit board 2 each include a circuit board 2 that have at least one on a surface 6 the circuit board 2 arranged electrical component 10 has, one above the circuit board 2 arranged cooling element 15 for dissipating heat to the ambient air or a cooling medium, which has a flat bottom and a heat conducting element 12 for dissipating heat from the circuit board 2 to the cooling element 15 , wherein the cooling element 15 with a top 21 the Wärmeleitelements 12 is thermally conductively connected. To allow for improved cooling, the top is 21 the Wärmeleitelements 12 and the top of the device 10 at an identical distance from the surface 6 the circuit board 2 arranged so that the cooling element 15 also with the top of the device 10 is thermally conductively connected.

16 illustrates a ninth embodiment of a device according to the invention, in which a heat-conducting element 12 on a track 3 preferably applied with solder electrically and thermally conductive. For this purpose, the conductor track 3 preferably in the form of a pad 31 from solder resist and other trace coatings exposed to an immediate electrical and thermal connection with the trace 3 to allow. The pad freed from the soldermask and other coatings 31 preferably forms the shape of the surface resting on the board of the heat-conducting element 12 after, in the soldering process, a self-alignment of the heat conducting element 12 on the pad due to the surface tension. The conductor track 3 is in this embodiment electrically and thermally conductive with a device 10 connected. This electrically and thermally conductive connection consists, for example, with the drain, collector or substrate connection of a preferably surface-mounted power transistor. Due to the electrically non-insulated connection of the heat-conducting element 12 with the component 10 over the track 3 In this exemplary embodiment, a galvanically insulating insulating element, for example a foil, a pad or a plate should preferably be inserted between the printed circuit board 2 remote surface of the heat conducting element 12 are provided, the electric currents and a galvanic connection to a resting thereon cooling element, in particular a cooling plate, prevents. This cooling element is in for better clarity 16 not shown.

17 and 18 exemplify a surface mountable heat conducting element 12 this is, which in the embodiment according to 16 can be used. The circuit board 2 opposite top 21 the Wärmeleitelementes 12 in 17 which preferably has direct or via a galvanically insulating insulating indirect thermal and mechanical contact with a cooling element, not shown, is preferably configured as shown with a smooth flat surface. In the 18 illustrated the circuit board 2 and the pad 31 facing surface 22 the Wärmeleitelementes 12 has depressions or grooves 23 on, similar to the embodiments in 4 to 6 absorb and / or remove gases and solvents produced during the soldering process.

19 illustrates a tenth embodiment of the invention, which is similar to the ninth embodiment in that at least one heat conducting element 12 with a trace 3 a circuit board 2 contacted and via the track 3 in electrically and thermally conductive connection with a component 10 is, for example, with the drain, collector or substrate connection of a preferably surface-mounted power transistor. In contrast to the surface-mounted heat-conducting element 12 of the ninth embodiment in 16 to 18 is the heat conducting element 12 in the tenth embodiment as in 19 represented by a through-hole mounting with soldering (also referred to by a person skilled in the art as through-hole mounting) or an interference fit (also referred to by the person skilled in the art as pressfit mounting) through preferably metallized bores or recesses 26 mounted electrically and thermally conductive. The metallization of the holes or recesses 26 is preferably electrically and thermally conductive with the conductor track 3 connected.

20 and 21 make heat conducting elements 12 for through-mount or press fit in perspective, as for example in the embodiment according to 19 Can be used. The circuit board 2 facing underside 22 the Wärmeleitelementes 12 in 20 has pens 24 on, similar to the embodiments in 7 to 12 in the recesses 26 the circuit board 2 grip and be fixed there by press-fitting or push-through mounting with soldering. Preferably, the conductor track 3 between the holes or recesses 26 a pad freed by the release of solder mask and other coatings, so that in addition to the thermal and electrical connection between the pins 24 the Wärmeleitelementes 12 and the track 3 Furthermore, a mediated by direct mechanical contact thermally and electrically conductive connection between the circuit board 2 facing surface of the heat conducting element 12 and the track 2 is present at the location of the pad.

22 represents the heat conducting element 12 opposite side of the circuit board 2 dar. The pins 24 the Wärmeleitelementes 12 in this case are preferably slightly, preferably 0.5 millimeters to 5 millimeters from the recesses 26 to either allow soldering in through-hole mounting or to improve mechanical retention when press-fit. On the heat conducting element 12 opposite side of the circuit board 2 may preferably be a conductor track 3 present, the electrically and thermally conductive with the heat conducting element 12 connected is. This track 3 Further, similar to the eighth embodiment, it may be utilized to provide an interdigitated comb structure with a trace 3 ' form with increased interface for thermal conduction.

23 illustrates an eleventh embodiment in which that trace 3 ' , with the associated heat-conducting element 12 electrically and thermally connected, of signal-carrying conductors 3 is electrically isolated. In this eleventh embodiment of the invention form the galvanically insulated conductor track 3 ' and signal-carrying tracks 3 overlapping comb structures to increase the cross section of the heat path between the two. The insulated conductor track overlaps 3 ' and at least one signal-carrying conductor track 3 on different levels of metallization, so that they run over each other and form a substantial overlap surface. The insulating material of the circuit board 2 , For example, a fiberglass composite, insulated the tracks 3 ' and the signal-carrying tracks 3 galvanic to each other, however, due to the small distance of the metallization levels of each other a heat path with high cross-section and short path ready. The distance between two adjacent planes is preferably less than 150 μm, more preferably less than 100 μm. For example, the material of the circuit board may be locally filled with particles of ceramic materials such as ZnO, Ti ₂ O ₅ , ZrO _2, or similar materials of high phononic thermal conductivity. 24 provides these interlocking but electrically isolated comb structures of the isolated trace 3 ' and the signal carrying trace 3 exemplified in a transparent scheme. The high regularity of the comb structures in 24 is not necessary, but alone an increased, here horizontal overlap of the insulated conductor track 3 ' and the signal carrying trace 3 on different levels of the circuit board 2 , The electrically and thermally interconnected levels of the conductor track 3 ' can via vias 4 be connected, the one provide electrical and thus electronically supported thermal conductivity between the connected metallization levels. The distances between the insulated tracks 3 ' and signal-carrying tracks 3 are preferably selected according to the standard EN 60664-1: 2007 in such a way that the specified insulation voltages and, if necessary,

Teilentladungsfreiheit be achieved at a given voltage. Further, preferably, the thickness of the material, such as a fiberglass composite, the circuit board between the insulated tracks 3 ' and signal-carrying tracks 3 On different levels of metallization preferably chosen so that it is as thin as possible for high heat conduction, on the other hand, but just thick enough to provide a predetermined isolation voltage (known to those skilled in the art as dielectric strength). For a longer life, the thinnest possible thickness for compliance with the insulation voltage also a safety margin can be added.

In the eleventh embodiment described above, those with at least one heat conducting element 12 electrically and thermally connected galvanically isolated tracks 3 ' of signal-carrying conductors 3 galvanically isolated and thus usually required electrical isolation between the cooling element 15 and components to be cooled 10 and / or tracks 3 and / or printed circuit boards 2 practically in the circuit board 2 laid. Accordingly, no further galvanically insulating device between the heat-conducting element 12 and a cooling element 15 more necessary.

The 25 shows a twelfth embodiment shown, which is based on the eleventh embodiment. In addition, according to the twelfth embodiment, at least one cooling element 15 thermally indirectly or directly with at least one heat conducting element 12 connected. Preferably, there is no galvanic separation between the cooling element in this embodiment 15 , the heat-conducting element 12 and the insulated trace 3 ' in front. When the the heat conducting element 12 facing surface of the cooling element 15 has sufficient extent to also about components 10 to reach is the height of the heat conducting element 12 preferably at least as high as the height of the component 10 to avoid geometric collisions. Particularly preferably, the height of the heat-conducting element corresponds 12 the height of the component 10 to give both a thermally conductive connection to the cooling element 15 to enable. An optional tolerance compensation element 32 between the at least one heat conducting element 12 or possibly also the at least one component 10 , and the cooling element 15 For example, a pad, a folio or a plate with a certain elasticity or a paste with a certain viscosity, can compensate for height tolerances and surface roughness, in order air-and gas-free thermally conductive contact between the cooling element 15 and heat conducting element 12 or possibly also the at least one component 10 manufacture. Preferably, the tolerance compensation element 32 not galvanically insulating. Particularly preferred is a tolerance compensation element 32 , which is electrically conductive and thus also has electronically supported thermal conductivity. The electronically supported thermal conductivity allows a much higher thermal conductivity in the case of most known materials than with solely phononically supported thermal conductivity of electrically insulating materials, in particular with materials of justifiable cost or elasticity.

Also with the in 23 and 25 The embodiments shown are the distances between the non-signal-carrying conductor track 3 ' and the signal-carrying tracks 3 are chosen in such a way that the specifications of the Standard EN 60664-1: 2007 are complied with, in particular with regard to the predetermined creepage distances (if the distance runs along a surface) and the predetermined clearances (if the distance does not run along a leading surface). In particular, these distances are in accordance with the specifications of Table F4 and the chapter 6.2 of the Standard EN 60664-1: 2007 selected.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• EP 0989794 A2 [0002]

Cited non-patent literature

• Standard EN 60664-1: 2007 [0022, 0068]

Claims (18)

Device for dissipating heat from a printed circuit board (2) - comprising a printed circuit board (2) having at least one electrical component (10) arranged on a surface (6) of the printed circuit board (2), with at least one above the printed circuit board (2 ) arranged with cooling element (15) for dissipating heat to the ambient air or a cooling medium, which has a flat bottom and - with at least one heat conducting element (12) for dissipating heat from the printed circuit board (2) to the cooling element (15), wherein the Cooling element (15) with an upper side (21) of the Wärmeleitelements (12) is thermally conductively connected, characterized in that the upper side (21) of the Wärmeleitelements (12) and the upper side of the component (10) at an identical distance from the surface (6) the circuit board (2) are arranged, so that the cooling element (15) is also connected to the upper side of the device (10) thermally conductive. Device after Claim 1 , characterized in that one of the upper side (21) opposite underside (22) of the heat-conducting element (12) rests on the surface of the printed circuit board (2). Device after Claim 2 , characterized in that the underside (22) of the heat-conducting element (12) has a plurality of recesses (23), in particular a plurality of parallel grooves. Device after Claim 2 , characterized in that a contact surface of the printed circuit board (2), on which the underside (22) of the heat-conducting element (12) rests, has a plurality of recesses, in particular a plurality of bores. Device according to one of the preceding claims, characterized in that the circuit board (2) comprises a valve disposed within the circuit board (2) insert element (8) which is thermally conductively connected to the heat-conducting element (12). Device after Claim 5 , characterized in that on the upper side (6) of the printed circuit board (2) up to the insert element (8) reaching recess (9) is arranged and the heat conducting element (12) in the recess (9) is arranged. Device according to one of the preceding claims, characterized in that the heat conducting element (12) having a plurality of pins (24) on its underside (22) which are each arranged in a recess (26) in the printed circuit board (2). Device after Claim 7 , characterized in that the pins (24) extend from a surface (6) on an upper side of the printed circuit board (2) to a surface (7) on an underside of the printed circuit board (2) and protrude from the underside of the printed circuit board (2) , Device according to one of Claims 7 or 8th , characterized in that the pins (24) are connected via a press fit with the printed circuit board (2). Device according to one of Claims 7 to 9 , characterized in that the pins (24) have a star-shaped cross section. Device according to one of Claims 7 to 10 , characterized in that the heat-conducting element (12) has a resting on the surface (6) of the printed circuit board (2) supporting part (25) and the pins (24) of the heat-conducting element (12) as from the support member (25) separate pins are formed , Device according to one of the preceding claims, characterized in that a heat-conducting, electrically insulating insulating element (14) is arranged between the upper side (21) of the heat-conducting element (12) and the underside of the cooling element (15). Device according to one of the preceding claims, characterized in that the printed circuit board (2) has a conductor track (3 '), which is electrically conductively connected to the heat conducting element (12), wherein the conductor track (3') carries no electrical signal and to all signal-carrying conductor tracks (3) of the printed circuit board (2) is electrically insulated. Device according to one of the preceding claims, characterized in that the heat-conducting element (12) is thermally conductive and / or electrically conductively connected to a plurality of first printed conductors (30 ') in different planes of the printed circuit board (12), wherein between the first interconnects (30') a plurality of second conductor tracks (30) are arranged, which are electrically isolated from the first conductor tracks (30). Device after Claim 14 , characterized in that the first interconnects (30 ') and the second interconnects (30) are arranged overlapping, so that the first interconnects (30') and the second interconnects (30) parallel to the surface (6) of the circuit board ( 2) arranged overlap surface. Device according to one of Claims 13 to 15 , characterized in that the conductor track (3 ') has a distance from all signal-carrying conductor tracks (3) of the printed circuit board (2), the less than 150 microns, more preferably less than 100 microns; or that the first conductor tracks (30 ') have a distance from the second conductor tracks (30') which is less than 150 μm, particularly preferably less than 100 μm. Device according to one of the preceding claims, characterized in that between the upper side (21) of the heat-conducting element (12) and the underside of the cooling element (15), a heat-conducting tolerance compensation element (32) is arranged. Device according to one of the preceding claims, characterized in that the circuit board (2) comprises a substrate (5) and at least partially in the substrate (5) arranged particles of a ceramic material, for example ZnO, Ti ₂ O ₅ , ZrO ₂ ,

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