EP3407425B1

EP3407425B1 - Connection assembly for power module and power component

Info

Publication number: EP3407425B1
Application number: EP17305616.9A
Authority: EP
Inventors: Luc Rambaud
Original assignee: Mitsubishi Electric Corp; Mitsubishi Electric R&D Centre Europe BV Netherlands
Current assignee: Mitsubishi Electric Corp; Mitsubishi Electric R&D Centre Europe BV Netherlands
Priority date: 2017-05-24
Filing date: 2017-05-24
Publication date: 2020-04-22
Anticipated expiration: 2037-05-24
Also published as: CN110622357A; WO2018216473A1; EP3407425A1; CN110622357B; JP2020504435A; JP6827563B2

Description

FIELD OF THE INVENTION

The present invention concerns a connection assembly for connecting a power semiconductor module and a power component.

BACKGROUND OF THE INVENTION

Hybrid or plug electric vehicles comprise an important number of power components in their power train to ensure the transformation of current between at least the battery of the vehicle and an electrical engine.
A typical application of power components involves a power control unit driving a three phase electrical engine and fed with current from a high voltage battery. The power control unit can typically comprise a bidirectional converter combined with a three-phase inverter and energy storage components such as capacitors and inductors.
The three-phase inverter of a power control unit can be made of power semiconductor modules such as a Transfer-molded Power Module (TPM) of Half-Bridge Power Module, integrating semiconductor switches than can be made of Insulated-Gate Bipolar Transistors (IGBT) or Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET), in order to sustain high power ranges (ranging from tens of kW to hundreds of kW) in a limited volume.
In the above-discussed application, a power semiconductor module is connected to a number of power components such as capacitors and inductors.
The connections between the power components in a hybrid or electric vehicle need to be carefully designed in order to withstand a number of constraints, resulting from the harsh automotive environment.
First, the connections between components need to withstand high current and voltage in a small volume to avoid the use of screws and washers. The connectors of the components must be lightweight, and cheap given that the automotive market is very competitive.
What's more, the connections between power components have to withstand tough constrains in terms of vibrations and heat. In particular the connections must be maintained even in case of vibrations or thermal dilation of the connected parts. Last, operating in the above-mentioned high power ranges imply directly connecting the components to each other in order to reduce connection lengths which are sources of stray inductance as well as losses by Joule effect.
It is known to connect a power module including semiconductor components to power elements such as capacitors or inductors by soldering; however this kind of connection can be deteriorated by solder fatigue.
A connection assembly can be seen in document US 2013/035005A1 between two high current contacts where an additional spring element is used to ensure the mechanical connection. Another connection assembly is known from DE 10 2004 054007 A1 , where two flat electrical contacts are connected by press fitting the male contact into an opening of the female contact that comprises a flexible tab.
Another connection assembly is known from document US 2012/0164865 , which discloses a press-fit connection assembly, comprising a first connector which comprises a bifurcated tip, a second connector comprising square through holes in which the first connector can be inserted, and a tapered clip element which can be inserted either in the first connector or between the first and second connectors, in order to press the first and second connectors against one another.
This connection assembly may provide good results in maintaining electrical contact in case of vibration. However each connector exhibits a low contact surface and is therefore not sufficient for transmission of high electrical currents. In other words, the connection assembly exhibits a high resistance defined by pL/S where S is the contact surface, L is the length, and p the resistivity of the material of the connection assembly. Hence the connection assembly requires an important number of connectors for connecting a power module with power components, and the resulting power module can be expensive, all the more as clip elements are required in addition to the connectors.
A skilled person could contemplate a simpler connection assembly represented schematically in Figure 1. This connection assembly 1 includes a male plate-shape connector including two pins 3 of square cross-section, a female plate-shape connector including two through holes 2 of square cross-section, each adapted to receive a pin.
Further, the connection assembly comprises one metal clip 4 adapted to retain the pins by friction once in the through-holes of the female connector, thereby maintaining contact between the pins and the female connector. An additional piece 5 receives and holds together the connectors and clip once assembled.
This connection assembly would provide a simpler way to achieve good performance in maintaining the electrical contact despite mechanical vibration thanks to the metal clip replacing the tapered clip element.
However this connection assembly comprises an important number of components, thereby increasing the number of steps necessary for its manufacturing, and hence its manufacturing cost. Moreover, the surface of electrical contact between the connectors remains quite small, and hence the losses by Joule effect are important.

PRESENTATION OF THE INVENTION

In view of the above, the aim of the invention is to provide a connection assembly for a power module and power components not having the inconveniences of the prior art.
In particular, one aim of the invention is to provide a connection assembly exhibiting a larger electrical contact of the connectors, and ensuring that this contact be maintained even in case of vibration or heat causing thermal deformation of the connectors.
Another aim of the invention is to provide a cheaper connection assembly.
Another aim of the invention is to provide a connection assembly that can be more easily than the connection assemblies of the prior art.
Accordingly, a connection assembly for electrically connecting a power semiconductor module and a power component according to claim 1 is diclosed.
In some embodiments, the connection assembly according to the invention can further comprise at least one of the following features:

the flexible tab may extend along the plane of the plate-shape female connector and be contained in the thickness of the plate-shape female connector.
the pressure component may comprise at least two tabs integral with the plate-shape female connector, extending from two opposite sides of the through hole and oriented towards each other, said tabs being shaped to abut against two opposite walls of the pin when it is received in the through hole.
In an example, the connection assembly further comprises a piece of electrically insulating material forming the stop element. The piece of electrically insulating material may comprise a first cavity adapted to receive an end of the plate-shape female connector, and a second cavity adapted to receive the pin of the plate-shape male connector, the cavities communicating with one another to allow insertion of the pin in the through hole of the plate-shape female connector through the second cavity when the plate-shape female connector is inserted in the first cavity.
In embodiments, each finger is on a same side of the through-hole and the connection assembly further comprises at least one guiding tab extending from an opposite side of the though-hole.
The stop element may comprise a protrusion integral with the pin, at a distance from the tip of the pin to be inserted in the through hole.
The pin may extend perpendicularly to the direction of the plate-shape female connector when inserted in the through hole, and one of the plate-shape female connector and the plate-shape male connector may be right-angled to allow in-line connection between the connectors.

The connection assembly according to the invention provides connectors incorporating a pressure component which allows the connectors to exert a pressure on one another, in order to maintain electrical contact between the connectors even in case of vibrations and/or heat dilation.
As the pressure component is part of the connectors, no additional piece is needed, and hence the connection assembly is cheaper.
The surface contact is also increased with reference to the prior art, since the connectors are plate-shaped and the electrical contact between the connectors is established along a main wall of the pin. Due to this geometry, the surface contact can be increased up to two or three times and hence the number of connectors can be reduced or the intensity of current increased.
The proposed connection assembly does not require any screw or washer. This minimizes the volume of the connection assembly, and limits the losses by Joule effect and the stray inductance of the connection assembly. It also obviates the needs for precise manipulations by an operator in order to respect a specific tightening torque.
Moreover, according to one embodiment of the invention, the connection assembly may consist solely in two connectors in the same metal (copper for instance). The connectors having the same coefficient of thermal expansion, the resulting connection assembly prevents contact losses between the connectors. The process for assembling the connectors is also greatly simplified since it can be decreased to only one step.
The shape of the stop elements and/or pressure components can be designed to optimize the mechanical and electrical contact between the connectors.

DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from the following detailed description given by way of non-limiting example, with reference to the accompanying drawings, in which:

Figure 1, already described, schematically shows one connection assembly according to the prior art,
Figure 2 schematically shows an example of a connection assembly applied to the connection of a power semiconductor module to a power component,
Figure 3 shows an example of a connection assembly.
Figures 4a and 4b schematically show an example of a connection assembly according to an embodiment of the invention, respectively before and after inserting the male connector in the female connector.
Figure 4c schematically shows the female connector of the connection assembly represented in figures 4a and 4b.
Figure 5 schematically shows a detail of an example.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

A connection assembly 1 suitable for connecting a power semiconductor module to a power component will now be disclosed.
With reference to figure 2 the power semiconductor module 2 can include at least one power semiconductor component, typically a switch, for instance a transistor such as a MOSFET, an IGBT or a J-FET (junction field effect transistor), a diode, etc., arranged inside a housing, the semiconductor component being connected electrically to a connector 20 part of the connection assembly 1.
The power component 3 is preferably an energy storage component, for instance a capacitor or an inductor, which is electrically connected to a connector 30 part of the connection assembly 1.
One preferred application of the connection assembly 1 is the connection of a three-phase inverter realized as a Transfer-molded Power Module 2 with at least one capacitor 3. The capacitor includes two terminals, each of which is connected to the power semiconductor module through one connection assembly 1.

General description of the connectors

Turning now to figures 3 and 4a to 4c, a detailed description of embodiments of the connection assembly will be made.
The connection assembly comprises one male connector and one female connector. For the sake of clarity and concision, it will be considered in the exemplary application of the invention that the female connector 20 is the connector of a power semiconductor module and the male connector 30 is the connector of a power component such as a capacitor. However the scope of the invention is not limited to this example but also covers the other way round wherein the power component comprises a male connector and the power semiconductor module comprises a female connector.
Both connectors are made of electrically conductive material, preferably are made of copper.
Also, both connectors 20, 30 are generally in the shape of a plate, which is to say that each connector has a small thickness compared to its width and length, and is sensibly planar. Also, each connector has a main direction which is the direction of its length, which is than its width.
The male connector 30 comprises at its tip a pin 31, which also has the shape of a plate. In particular, the cross-section of the pin 31 extends along one main direction d shown on figure 4a. According to a preferred embodiment, this main direction corresponds to the direction of the width of the male connector.
Advantageously, the pin extends over at least 50% of the width of the male connector, said width being measured at the base of the connector.
In a preferred embodiment, the cross-section of the pin 31 can be rectangular, however it can also be oblong with rounded ends, as shown in the exemplary embodiment of figure 3.
The female connector 20 comprises a hole 21 extending through the thickness of the connector 20. The through-hole 21 is adapted to receive the pin 31 of the male connector 30. In particular, the through hole extends along a main direction D shown on figure 3, the main direction preferably corresponding to the direction of the width of the female connector.
It is thus understood that when the pin 31 of the male connector 30 is inserted in the hole 21 of the female connector 20, the male and female connectors extend perpendicularly to one another. However, in case an in-line connection is needed between the power semiconductor module 2 and the power component 3, one of the male and female connectors can be right-angled, as shown in figure 2.
The through hole 21 can have a generally rectangular shape, but the angles of the rectangle can also be slightly beveled to allow positioning and locking the pin within the hole.
Advantageously, the through hole 21 extends over at least 50% of the width of the female connector.
The shapes of the male and female connectors allow increasing the surface of electrical contact between the connectors. Indeed, once the pin 31 is inserted in the through hole, electrical contact is established between at least one wall 32 of the pin extending along the main direction of the pin and along the direction d, and at least one corresponding wall of the female connector. In embodiments, the wall of the female connector in contact with the wall 32 of the pin can be a wall 22 shown in figure 3, delimiting the hole 21. The contact surface can therefore comprise the surface of the wall 22 of the female connector delimiting the hole along the main direction thereof.
Optionally, the pin 31 the sides of the pin can be beveled at its tip to make its insertion easier inside the through-hole 21, as represented in the exemplary embodiment of figure 5.
The female connector 20 comprises a pressure component 40, which is adapted to press the male and female connector against each other when the pin 31 is inserted in the hole 21, in order to maintain electrical contact even in case of vibrations, and to ensure that the electrical contact surface is maximized. Also, as will be described in more details below, the connection assembly 1 comprises at least one stop element 11 of the pin 31 relative to the hole.

Pressure component

Embodiments of the pressure component 40 are detailed with reference to figures 3 and 4a to 4c.
The pressure component comprises at least one flexible tab 40 formed integral with the female connector 20, and adapted to abut against the pin, in order to exert a pressure on the pin 31 against the female connector, when the pin is inserted in the hole.
With reference to figure 3, according to one embodiment, the pressure component 40 comprises at least one tab contained in the thickness of the female connector 20. Each tab extends parallel to the main direction of the female connector, towards the hole 21, from a wall 23 opposite the wall 22 which delimits the hole 21 and is in contact with the pin.
It can be appreciated that, as the tab 40 is formed integral with the female connector, the contact surface between the tab and the pin also increases the electrical contact between the male and female connectors. As on figure 3, the pressure component 40 can comprise more than one tab, for instance two tabs.
The number and size of the tabs can be adjusted to obtain desired properties of the pressure components, for instance narrower tabs can increase their flexibility; whereas larger or more numerous tabs can increase the electrical contact of the connector 20 with the pin 31.
Moreover, each tab preferably has square ends in order to maximize electrical contact with the pin, however rounded ends are also possible embodiments.
The pin 31 of the male connector comprises a groove 33 adapted to receive the end of the tab when the pin is inserted in the hole. The groove thus extends along the main direction of the cross-section of the pin, i.e. along the width of the connector, at a distance from the tip of the pin. The groove 33 locks the achieved contact between the tab 40 and the pin 31.
With reference to figures 4a to 4c, according to an alternative embodiment, each tab of the pressure component is not contained within the thickness of the female connector but instead protrudes from the connector.
In this embodiment also, the pin comprises at least one groove 33 adapted to receive one of the tabs 40a, 40b.
The tabs 40a, 40b are preferably shaped in order to abut against two opposite walls of the pin when the latter is inserted in the wall, so that each tab can exert a pressure on a respective side of the pin. In other words, the tabs 40a, 40b protrude towards opposite directions, such that each tab is directed towards the other.
The exertion of a pressure on both sides of the pin avoids tilting of the pin relative to female connector, which would slightly lower the surface contact between the connectors.
Preferably, as is shown on Figure 4c, two tabs 40a, 40b are arranged at symmetrical positions relative to the hole 21, on the same side of the female connector 20, in order to exert pressure on the two sides of the pin.
However, the two tabs 40a, 40b can have different shapes and sizes, and abut against the pin 31 at different levels thereof. In the embodiment shown in figures 4a to 4c, the first tab 40a is flexible and exerts a pressure against the pin 31 when received by the groove 33, and the second tab 40b exerts a counter-pressure on the pin 31.
In the example shown in figures 4a to 4c, the tabs 40a, 40b protrude from the middle of each side of the hole 21, below the female connector.
Each tab of this embodiment is also slightly flexible to accommodate vibrations and/or thermal dilation of the connection assembly. The flexibility of the tabs results naturally from the fact that they are formed in a thin layer of metal such as copper.
Preferably, each tab 40 of the pressure component is cut or machined within the female connector 20. The tabs protruding from the connector are folded after being cut.
It will be appreciated that each tab 40 coming into contact with the pin 31 adds a portion of electrical contact surface between the female connector and male connector, thereby increasing the current density that can flow between the connectors.
Therefore the wall of the female plate-shape connector in electrical contact with the pin 31 when the latter is inserted in the hole comprises the walls of the various tabs 40 of the pressure component in contact with the pin 31.

Stop element

With reference to figures 3 to 5, the stop element 11 of the pin 31 relative to the hole 21 of the connection assembly will now be described.
According to an example which is disclosed in figure 3, the stop element 11 can be a part distinct from the male and female connectors, and shaped to receive both the end of the female connector 20 and the pin 31 of the male connector in a position where the pin is received in the hole. Preferably, the stop element is a piece of insulating material able to withstand high voltages. The material can for instance be a polyimide material marketed under the name of Kapton.
To this end, as shown in figure 3 the stop element comprises a first cavity 12 adapted to receive the end of the female connector, and a second cavity 13, extending perpendicularly to the first, adapted to receive the pin 31 of the male connector 30.
The cavities are dimensioned and positioned relative to each other so that, when the female connector 20 is inserted in the first cavity 12 and abuts against the bottom of the cavity, the hole 21 of the connector is aligned with the second cavity 13. Thus, the pin 31 can be inserted in the second cavity 13 through the hole 21 of the female connector, until abutting against the bottom of the cavity, said bottom stopping the pin 31 in the cavity.
This example of the stop element 11 also ensures that the two connectors are perpendicular to each other and therefore the contact surface extends over the whole wall 22 delimiting the hole 21.
As is visible from figure 3, this example of the stop 11 can be combined with the embodiment of the pressure component 40 according to which each tab extends within the thickness of the female connector 20.
According to an embodiment which is represented on figures 4a to 4c, the stop element 11 comprises at least one finger integral with the female connector 20 and extending over the hole 21, at a distance thereof. On the exemplary embodiment of the figures, two fingers are represented, extending from a same side of the hole to allow insertion of the male connector 30 from the opposite side of the hole.
The number and width of the fingers is a choice of design.
However, if there is at least one finger as a stop element 11 extending on one side of the hole 21, the female connector preferably comprises either another stop element 11 or a guiding tab 50 extending from the other side of the hole 21 and shaped to contact on opposite side of the pin 31 when the latter is inserted in the hole. This ensures a guiding of the pin 31 towards the stop element 11. In the embodiment shown in figures 4a to 4c, the female connector 20 comprises two guiding tabs 50, extending on the same side of the connector that the fingers of the stop element 11, the guiding tabs 50 and fingers 11 extending from two opposite sides of the hole 21. Said sides are the sides along the main direction D of the hole.
According to this embodiment, the wall of the female plate-shape connector in electrical contact with the pin 31 when the latter is inserted in the hole also comprises the walls of the finger(s) of the stop element (11) and guiding tab(s) which are in contact with the pin.
Last, according to another example which is represented in figure 5, the stop 11 may comprise a protrusion formed integral with the pin 31, on the male connector, and at a distance from the tip of the pin. Thus when the pin 31 is inserted in the hole 21 of the female connector, the protrusion 11 abuts against the female connector and prevents the pin from being inserted any further.
It will be appreciated that, when the stop element 11 is formed either by a finger on the female connector or by a protrusion 11 on the male connector, its coming into contact with the other connector increases the electrical contact surface between the female connector and male connector, thereby increasing the current density that can flow between the connectors.
Various examples of stop element 11 and pressure component 40 have been detailed above. In the embodiment shown on Figures 4A to 4C and the example shown on Figure 3, specific combinations are made.
In the example of figure 3, the pressure component 40 is formed of two tabs extending within the plane of the female-connector 20, and the stop element 11 is formed of an additional piece of electrically insulating material receiving the female connector 20 and the male connector 30. The electric contact is made on the contact surfaces between the pin 31 and the tabs 40, and between the pin and the wall 22 of the female connector delimiting the hole 21.
In the embodiment of figures 4a-4c, the pressure component 40 is formed of two tabs 40a,40b protruding below the female-connector 20, from opposite sides of the through-hole 21. The tabs protrude from the middle of each opposite side of the through-hole 21. The stop element 11 is formed of two fingers protruding above the hole, on the other side of the female-connector relative to the plane of the latter. The fingers extend from the same side of the hole as the tab 40a, the tab 40a being between the fingers. Two additional guiding tabs 50 face the fingers to act as a guiding means of the pin 31. They protrude from the same side as the tab 40b and are positioned on each side of the tab 40b.
The electrical contact is made between the pin 31 and the corresponding contact surfaces of the tabs 40a, 40b, the guiding tabs 50 and the fingers of the sop element 11. The wall of the female plate-shape connector in electrical contact with the pin 31 when the latter is inserted in the hole thus comprises the walls of the tabs 40a, 40b, guiding tabs 50, and the fingers in contact with the pin 31.
Another embodiment could be contemplated wherein the positions of the pressure component 40 and the stop element 11 would be inverted; there would thus be one finger positioned between two tabs of a pressure component. A guiding tab could be positioned opposite the finger. Other tabs could be positioned opposite the first tabs of the pressure component to exert a counter-pressure on the pin.
One can easily understand that the assembly process of a connection assembly 1 according to the claimed invention is quite easy.
Indeed, in the embodiments the connection assembly 1 consists in only two elements, namely the male connector 30 and female connector, and assembling the two consists in inserting the male connector 30 in the female connector 20.
For instance on figure 4a the male connector 30 is shown at a distance from the female connector 20, before insertion. On figure 4b the male connector 30 is inserted in the female connector 20 until the stop element 11 prevents the male connector 30 from being inserted any further.
In examples in which the connection assembly also comprises a separate piece of material as a stop element 11, the process of assembling the parts comprises inserting the female connector in the stop element 11, and then the male connector in the stop element 11. By this, the male connector is simultaneously inserted in the female connector.
Thus at most two steps are required for assembling the parts of the connection assembly.
Moreover, the manufacture of the male and female connector is also easy since each connector can be obtained by machining or cutting and folding.

Claims

A connection assembly (1) for electrically connecting a power semiconductor module (2) and a power component (3), the connection assembly (1) comprising:
- a plate-shape female connector (20) comprising a through hole (21),

- a plate-shape male connector (30) comprising a pin (31),
the connectors (20, 30) being formed in electrically conductive material,
wherein the cross-section of the pin (31) extends along a main direction (d), and the through hole (21) is shaped to receive the pin (31), thereby establishing electrical contact between at least one wall (32) of the pin extending along said main direction and one wall of the plate-shape female connector (20),
and wherein the plate - shape female connector (20) comprises a pressure component (40) adapted to apply a pressure on the pin (31) against the plate-shape female connector (20) when the pin is received in the through hole, the pressure component (40) comprising a flexible tab integral with the plate-shape female connector and being adapted to abut against the pin (31) when it is received in the through hole (21), and the plate-shape male connector (30) comprises a groove (33) adapted to receive the flexible tab (40) when the pin is inserted in the through hole,
the connection assembly further comprising a stop element (11) of the pin (31) relative to the through hole (21), said stop element comprising at least one finger integral with the plate-shape female connector (20) and extending over the through hole (21), at a distance thereof.
A connection assembly (1) according to claim 1, wherein the flexible tab (40) extends along the plane of the plate-shape female connector (20) and is contained in the thickness of the plate-shape female connector (20).
A connection assembly (1) according to any of the preceding claims, wherein the pressure component (40) comprises at least two tabs (40a, 40b) integral with the plate-shape female connector, extending from two opposite sides of the through hole (21) and oriented towards each other, said tabs being shaped to abut against two opposite walls of the pin (31) when it is received in the through hole.
A connection assembly (1) according to any of the preceding claims, wherein each finger is on a same side of the through-hole (21) and the connection assembly further comprises at least one guiding tab (50) extending from an opposite side of the through-hole (21).
A connection assembly (1) according to any of the preceding claims, wherein the pin (31) extends perpendicularly to the direction of the plate-shape female connector (20) when inserted in the through hole (21), and one of the plate-shape female connector (20) and the plate-shape male connector (30) is right-angled to allow in-line connection between the connectors.
An assembly comprising a semiconductor power module (2), a power component (3), and a connection assembly according to any of the preceding claims for connecting the power module (2) and the power component (3), whereof the power module (2) comprises one of the female and male connectors of the connection assembly, and the power component (3) comprises the other of the female and male connectors of the connection assembly.