DE102019204639A1 - Air gap formation in an electrical contacting of a circuit board - Google Patents

Abstract

A printed circuit board (10, 11) for a power module (50), comprising a conductor layer (12); a backing layer (16); and an insulating layer (14) which is arranged between the conductor layer (12) and the carrier layer (16); wherein a first busbar (18, 19) is attached in an electrically conductive manner to an upper side (122) of the conductor layer (12) facing away from the carrier layer (16), the printed circuit board (10, 11) having an between a second busbar (20) , which is in contact with the first busbar (18, 19) on a side of the first busbar (18, 19) facing away from the conductive layer (12), and current flowing can be applied to the conductive layer (12), the first busbar (18, 19) being shaped to to form a gap (182, 192) between the second busbar (18, 19) and the conductor layer (12).

Description

TECHNICAL AREA

The present invention relates to the field of semiconductor-based power modules. In particular, the present invention relates to an electrical contacting of a circuit board of such a power module with an air gap formation.

TECHNICAL BACKGROUND

In the field of power electronics, a large number of semiconductor components are accommodated in an integrated circuit (IC). The so-called semiconductor chips that result from this are electrically connected to one another or to other modular units, such as the power supply, by means of electrical conductor tracks that are applied to a circuit board. In vehicle technology in particular, the advancing development of electromobility requires ever higher currents. Due to the internal resistance of the components, this leads to the power electronics heating up. It is therefore essential to dissipate the heat into the environment with the help of cooling lines or heat sinks.

A large number of possible solutions in this regard are known from the prior art. One of the options for cooling components uses a special type of printed circuit board that comprises a carrier, a conductor layer and an insulating layer formed in between. In the field, this type of circuit board is known as Insulated Metal Substrate (IMS). Due to their efficient heat dissipation, IMS circuit boards are used for semiconductor electronics in the fields of LED technology, automotive technology and entertainment electronics. For example, the thermal conductivity of the insulation layers used between the conductor layer (e.g. made of copper) and the carrier (e.g. made of aluminum) is a factor of 5 to 10 higher than that of conventional circuit boards based on flame-retardant materials (e.g. FR4).

For example, an IMS circuit board is off DE 100 56 832 A1 known.

Nevertheless, the IMS circuit boards known from the prior art do not have satisfactory electrical contacts. IMS circuit boards cannot be electrically contacted by means of a through-hole plating with conductor tracks, in which a (metallic) contacting material is introduced from the top of the power module into the interior of the conductor layer, as this would sever the insulating layer and impair the insulation.

Even direct electrical contact using screws cannot prevent the insulation layer from being severed. It has also been proposed to solder conductor tracks or busbars onto an IMS circuit board, with a screw connection being located at one end of the conductor tracks. However, screw contacts are disadvantageous in that the manufacturing process is usually more expensive than e.g. a laser weld contact. In addition, there are additional costs for the screw, the screw nut and the plastic carrier for embedding the conductor tracks. Furthermore, additional installation space for the screw, the screw nut and the accessibility of the tool must be taken into account.

Alternatively, conductor tracks are connected to the circuit board using an ultrasonic welding process. The tolerance compensation takes place here by bending the conductor tracks. In order to ensure the lowest possible reaction forces, these conductor tracks are designed for as long as possible, which causes higher costs and requires additional installation space.

The invention is therefore based on the object of improving the electrical contacting of semiconductor-based power modules, in particular of IMS circuit boards, with regard to the simplicity of manufacture and efficiency of heat dissipation.

The object is achieved by a printed circuit board according to claim 1, a power module according to claim 9 and a method for producing such a printed circuit board according to claim 10.

The circuit board according to the invention can have a circuit board and / or be produced by means of a printed circuit board (PCB). The circuit board is preferably used in a power module, for example for 48V, 400V and / or 800V applications in an electric and / or hybrid vehicle.

The conductor layer is made of an electrically conductive material such as metal, preferably copper or a copper alloy. Alternatively, the conductor layer can be formed from a different material such as stainless steel or aluminum. The thickness of the conductor layer is preferably in a range from 0.2 mm to 4.0 mm, more preferably 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm or 3.5 mm.

The carrier layer is preferably formed from a metal, for example aluminum, copper, stainless steel. The insulating layer between the conductor layer and the carrier layer is preferably made of a polymer material and / or a Ceramic material made. The insulating layer can have a thickness of 0.05 mm to 0.20 mm.

The first and / or second busbar (or conductor track) is made of an electrically conductive material such as metal, preferably copper, copper alloy and / or aluminum. The attachment of the first busbar to the top of the conductor layer is preferably a soldered connection. Alternatively, a weld connection, e.g. Laser or ultrasonic welding connection, can be used. The attachment of the second busbar to the top of the first busbar is preferably a soldered or welded connection.

The first bus bar is shaped to form a gap between the second bus bar and the conductor layer. The gap is preferably an air gap. Alternatively, an air gap can first be formed, which is then filled with a filler material (e.g. foam). The gap is preferably at least partially, more preferably completely, arranged in the first busbar.

The gap, preferably an air gap, causes a heat spread in the first busbar, which ensures that the maximum permissible temperature of the insulating layer within the circuit board is not exceeded. In this way, impairment of the functionality of the insulating layer and thus also of the printed circuit board as a whole can be avoided or at least reduced.

Advantageous refinements and developments are specified in the subclaims.

According to one embodiment, the first busbar has an arc shape with an upper section and a lower section connected to the upper section, the lower section being attached to the top of the conductor layer, the gap being arranged between the upper and lower sections.

The arch shape thus has an opening between the upper and lower section in which the gap or air gap is formed. The first and / or second section can each have a thin layer. The first busbar can be formed in one piece. The arch shape can be produced, for example, by means of a punching and bending process. This measure realizes a heat spread in a simple manner. The circuit board is therefore easy to manufacture and inexpensive.

According to a further embodiment, the arch shape comprises a U-shape or a V-shape.

The U or V shape is particularly easy to implement, in particular by means of a stamping and bending process. The busbar is therefore inexpensive to manufacture.

According to a further embodiment, the first busbar has a bridge shape with two end sections and a middle section arranged between the end sections, at least one of the two end sections being fastened to the top of the conductor layer, the gap being arranged between the two end sections.

As an alternative to the above arch shape with the upper and lower section, the bridge shape with two end sections and a section formed between them is particularly easy to achieve. The busbar is therefore inexpensive to manufacture.

According to a further embodiment, a second busbar is fastened in an electrically conductive manner to an upper side of the first busbar facing away from the conductor layer.

The second busbar (or conductor track) can be made of a conductive material such as metal, analogously to the first busbar. The second busbar can be attached to the first busbar by means of a welded connection, for example a laser or ultrasonic welded connection, or alternatively a screw connection.

According to a further embodiment, a connection point between the first busbar and the second busbar is arranged above the gap.

The connection point between the first and second busbars is preferably located vertically directly above the gap. This means that there is an overlap between the gap and the joint in the vertical direction. If the second busbar is connected to the first busbar using a welding process, the welding point is located vertically above the gap. In this way, the spreading of the heat generated when connecting the two busbars, for example during the welding process, can take place more effectively. The overheating-related impairment of the circuit board can thereby be effectively avoided or reduced.

According to a further embodiment, the printed circuit board is connected to a heat sink on the underside.

The heat sink can be an aluminum body or have another suitable material. The functionality of the power electronics is therefore ensured with the heat dissipation.

According to a further embodiment, a heat conducting layer is arranged between the heat sink and the carrier layer of the printed circuit board.

This improves the thermal coupling between the heat source (e.g. conductor layer) and the heat sink. The functionality of the power electronics is further improved. The heat conducting layer can have a thermal interface material (TIM).

• 1 eine schematische Darstellung einer Leiterplatte gemäß einer Ausführungsform in einer perspektivischen Ansicht;
• 2 eine Frontansicht der Leiterplatte aus 1;
• 3 eine Schnittansicht der Leiterplatte aus 1;
• 4 eine schematische Darstellung einer Leiterplatte gemäß einer weiteren Ausführungsform in einer perspektivischen Ansicht;
• 5 eine Frontansicht der Leiterplatte aus 4; und
• 6 eine Schnittansicht der Leiterplatte aus 4.

Embodiments will now be described by way of example and with reference to the accompanying drawings. Show it:

• 1 a schematic representation of a circuit board according to an embodiment in a perspective view;
• 2 a front view of the circuit board 1 ;
• 3 a sectional view of the circuit board 1 ;
• 4th a schematic representation of a circuit board according to a further embodiment in a perspective view;
• 5 a front view of the circuit board 4th ; and
• 6th a sectional view of the circuit board 4th .

In the figures, the same reference symbols relate to the same or functionally similar reference parts. The relevant reference parts are identified in the individual figures.

1 shows a schematic representation of a circuit board 10 according to one embodiment in a perspective view.

The circuit board 10 has a layer structure that has a conductor layer 12 , an insulating layer 14th and a backing layer 16 includes. The insulating layer 16 is located between the conductor layer 12 and the backing layer 14th . The carrier layer 16 and the insulating layer 14th show how in 1 shown a larger area than the conductor layer 12 on. There can be several conductor layers 12 on the insulating layer 16 to be ordered. The carrier layer 16 is with a heat sink 22nd via a thermal conductor layer 24 connected.

A first power rail 18th is by means of a solder layer 13 at a top 122 the conductor layer 12 tied up. A second power rail 20th is at a welding point by means of a welding process 17th a top 189 the first busbar 18th tied up. The second busbar 20th serves to be electrically connected to other electronic components. This creates the conductor layer 12 electrically contacted.

The exemplary first power rail 18th out 1 has a U-shape and, as in the front view in 2 and in the sectional view in 3 shown in more detail, an upper section 184 and a lower section 186 on. The lower section 186 has a greater extent in a longitudinal direction than the upper portion 184 . This is for better adhesion to the top 122 the conductor layer 12 .

Between the top and bottom sections 184 , 186 is an air gap 182 formed who, as in 3 shown vertically directly below a weld 17th on which the second busbar 20th with the first busbar 18th is connected, is arranged. This means the air gap 182 and the weld 17th (or generally the connection point between the first and second busbars 18th , 20th ) are at the same height in the horizontal direction or overlap in this direction.

4th shows a schematic representation of a circuit board 11 according to a further embodiment in a perspective view.

The circuit board 11 basically has most of the components that go into the circuit board described above 10 out 1-3 are included. In contrast to the above embodiment, the circuit board 11 out 4-6 a busbar 19th that has a bridge shape. As in the front view in 5 and in the sectional view in 6th shown in more detail, has the first busbar 19th a first end portion 194 and a second end portion 196 on. Both end sections 194 , 196 are by means of a solder layer 15a , 15b at the top 122 the conductor layer 12 tied up.

Between the first and second end sections 194 , 196 is also an air gap 192 formed who, as in 6th shown vertically directly below the weld 17th on which the second busbar 20th with the first busbar 19th is connected, is arranged.

The circuit board according to the invention 10 , 11 can be used for a power module, in particular for 48V, 400V and / or 800V applications in an electric vehicle and / or a hybrid vehicle. Because of the air gap within the first busbar 18th , 19th is the heat spread of the circuit board 10 , 11 improved. The functionality of the semiconductor-based power module is therefore ensured.

List of reference symbols

10, 11

Circuit board

12

Conductor layer

122

Top

13

Solder layer

14th

Insulating layer

15a

first solder layer

15b

second solder layer

16

Carrier layer

17th

Welding point

18, 19

first busbar

182, 192

gap

184

upper section

186

lower section

194

first end section

196

second end section

198

middle section

189, 199

Top

20th

second busbar

22nd

Heat sink

24

Thermal conductor layer

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 10056832 A1 [0004]

Claims (10)

A printed circuit board (10, 11) for a power module (50) comprising: - a conductor layer (12); - A carrier layer (16); and - An insulating layer (14) which is arranged between the conductor layer (12) and the carrier layer (16); wherein a first busbar (18, 19) is attached in an electrically conductive manner to an upper side (122) of the conductor layer (12) facing away from the carrier layer (16), the printed circuit board (10, 11) having an between a second busbar (20) , which is in contact with the first busbar (18, 19) on a side of the first busbar (18, 19) facing away from the conductive layer (12), and current flowing can be applied to the conductive layer (12), the first busbar (18, 19) being shaped to to form a gap (182, 192) between the second busbar (18, 19) and the conductor layer (12). PCB (10) after Claim 1 wherein the first busbar (18) has an arc shape with an upper section (184) and a lower section (186) connected to the upper section (184), the lower section (186) at the top (122) of the conductor layer ( 12), with the gap (182) located between the upper and lower sections (184, 186). PCB (10) after Claim 2 wherein the arch shape comprises a U-shape (181) or a V-shape. PCB (11) after Claim 1 wherein the first busbar (19) has a bridge shape with two end sections (194, 196) and a middle section (198) arranged between the end sections (194, 196), with at least one of the two end sections (194, 196) at the top (122) of the conductor layer (12) is attached, the gap (192) being arranged between the two end sections (194, 196). Printed circuit board (10, 11) according to one of the preceding claims, wherein the second busbar (20) is attached in an electrically conductive manner to a top side (189, 199) of the first busbar (18, 19) facing away from the conductor layer (12). Circuit board (10, 11) according to one of the preceding claims, wherein a connection point (17) between the first busbar (18, 19) and the second busbar (20) viewed from the conductor layer (12) over the gap (182, 192) is arranged. Circuit board (10, 11) according to one of the preceding claims, wherein the circuit board (10) is connected on the underside to a heat sink (22). PCB (10, 11) according to Claim 7 , wherein a heat conducting layer (24) is arranged between the heat sink (22) and the carrier layer (16) of the printed circuit board (10). Power module, in particular for a vehicle, preferably an electric vehicle or a hybrid vehicle, comprising a circuit board (10, 11) according to one of the Claims 1 to 8th . A method for manufacturing a printed circuit board (10, 11) for a power module (50), comprising: - providing a conductor layer (12); - Providing a carrier layer (16); - Arranging an insulating layer (14) between the conductor layer (12) and the carrier layer (16); - Fastening a first busbar (18, 19) on a top side (122) of the conductor layer (12) facing away from the carrier layer (16), the printed circuit board (10, 11) being connected to a second busbar (20) connected to a the side of the first busbar (18, 19) facing away from the conductor layer (12) is in contact with the latter, and current flowing through the conductor layer (12) can be acted upon, the first busbar (18, 19) being shaped to form a gap (182 , 192) between the second busbar (18, 19) and the conductor layer (12).

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