Patent Application
20250167057
This application claims the benefit of French Patent Application No. 23 11283, filed on Oct. 18, 2023, the entirety of which is incorporated by reference.
The present invention relates to semiconductor power modules and to a method for manufacturing them.
Power modules generally comprise at least two electronic chips which are electrically connected to connection elements such as metal tabs, and can also comprise one or more capacitors which are electrically connected to the chips or to the connection elements.
Examples of power modules are disclosed in the publications FR3115651, WO2018/024973 and U.S. Pat. No. 9,041,183.
In the application WO2018/024973,
Existing power modules are developed specifically for particular chips and take account of the size of the chip and of the location of the electrical contacts. Thus, some comprise screen-printed electrical tracks which are dependent on the arrangement of these contacts.
A drawback of these modules is the impossibility of using chips other than those for which the module has been developed, without having to extensively review the manufacturing method, notably the screen printing steps and/or the shape of the supports receiving the chips.
However, module manufacturers are sometimes faced with supply difficulties which force a change in chip suppliers, and the redesign of the manufacturing method when there is a change in chip model and the use of a new model which does not have the same dimensions and/or arrangements of contacts generates significant manufacturing delays and significant additional costs.
Consequently, there is a need to overcome this drawback.
The invention aims to meet this need, and it does so, according to one of its aspects, by proposing a power module comprising:
By virtue of the invention, it is possible to use a plurality of chips having different dimensions and/or arrangements of contacts, whilst limiting the changes to be applied to the module when switching from one chip model to another.
Specifically, different shims can be used depending on the chips in order to render said chips compatible with a large part of the elements making up the module, and these elements can thus remain unchanged.
This greatly simplifies the replacement of one chip with another, since it is no longer necessary, as in the prior art, to extensively review the manufacturing method.
Thus, in preferred exemplary implementations of the invention, the shim is the only element that needs to be modified to enable the use of a different chip on an existing module.
The module may comprise:
The shim may be produced without any conductive element such as an electrical track or, as a variant, with at least one such conductive element.
The shim may be made of any suitable material, notably ceramic or other, its shape being obtained by sintering, 3D printing, machining or otherwise.
The shim already exists during its introduction into the corresponding cutout of the module.
The shape of the shim is dependent on the chip model associated therewith.
In examples, the shim has, at an edge, at least one lateral opening into which a corresponding connection element electrically connected to a contact of the chip engages. This connection element is, for example, a metal electrical connection tab, of flattened cross section.
In examples, the shim has, at two opposite longitudinal edges, two respective lateral openings into which two corresponding connection elements electrically connected to two respective contacts of the chip engage. These connection elements are, for example, metal tabs extending in directions away from the power module. They are, for example, contacts corresponding to power terminals of a transistor, such as the source or the drain.
The connection element or elements may be soldered to the corresponding contact(s) of the chip by any means, for example with the aid of soldering paste disposed at the interface between the components to be soldered together.
The shim may have, at an edge substantially perpendicular to the aforementioned longitudinal edges, an additional opening into which an additional connection element electrically connected to a respective contact of the chip engages. This is, for example, a contact corresponding to a control terminal, for example a gate contact of a power transistor.
This additional connection element may be soldered directly to a corresponding contact of the chip, or, as a variant, the shim bears an electrical track soldered to a corresponding contact of the chip and the additional connection element is soldered to the track.
The first cutout which receives the chip may have a contour of rectangular or other shape; however, the rectangular shape is preferred.
The chip may not occupy the entire cutout in question in top view.
When the chip occupies the entire cutout in top view, the cutout can allow the chip to be positioned therein, to within an assembly clearance. In this case, the shim can just be superposed with the chip without being interposed between said chip and one or more edges of the cutout. The shim may then have only the function of thickness compensation, assisting the positioning of the connection elements and potentially also serving to establish an electrical connection between a contact of the chip and a connection element which is not directly superposed therewith.
By contrast, when the chip does not occupy the entire cutout in top view, the shim advantageously helps to position said chip in the cutout by being inserted between said chip and at least one edge of the cutout.
Thus, in embodiment examples, the shim is longer than the chip at the contact thereof, and has at least one portion engaged into the cutout between the chip and the housing element defining the cutout receiving the chip. The shim is interposed, for example, on at least three sides, notably four sides, between the chip and the housing element defining the cutout receiving the chip.
The shim may have a face that is substantially coplanar with a face of the housing element defining the cutout receiving the chip in contact with the shim.
The third housing element may have cutouts for receiving connection elements positioned so as to make it possible to superpose the latter with electrical contacts of the second chip.
The housing elements may be passed through by holes allowing the passage of retaining members for retaining the housing elements in the assembled state, notably screws.
The module may comprise at least one heat transfer element in contact with an outer face of a chip, even better two heat transfer elements each in contact with an outer face of a respective chip, this or these heat transfer elements preferably each comprising a plate of metal, preferably of copper.
A further subject of the invention is an array of power modules, comprising at least a first and a second module according to the invention, at least one of the chips of the first module being different from a corresponding chip of the other module, the two modules comprising different shims and at least identical first and second housing elements. “Different chip” should be understood to mean that the chip model is different, by at least one of the dimensions thereof, notably length and/or width, and/or the arrangement of the contacts.
The connection elements may be identical, and also the third housing element.
A further subject of the invention is a method for manufacturing a power module, notably a module according to the invention, as defined above, this module comprising:
The aforementioned openings in each shim may be in the form of notches.
In an exemplary implementation of the invention, the method comprises the introduction:
The method may comprise the replacement of one shim with another of different shape, adapted to a different chip model.
A further subject of the invention is the assembly guide as such, and the assembly guide and the assembly of the components of the module that are intended to be assembled with the aid of the guide.
The invention will be able to be better understood upon reading the following detailed description of non-limiting exemplary implementations thereof, and upon examining the appended drawing, in which:
The power module 1 shown in
The module 1 also comprises connection elements, namely, in the example illustrated, metal tabs 41 and 42 extending opposite a first side of the module 1, a metal tab 43 extending on the opposite side therefrom, and opposite metal tabs 44 and 45 extending from the two other sides.
The module 1 may comprise, as illustrated, on its main faces, heat transfer plates, of which one 50 is visible in
The different housing elements and the heat transfer plates may be retained by screws 60, as illustrated.
The module 1 is shown in
At least one of the housing elements, for example the lower element 10, may comprise an opening 11 for injecting a filling insulating resin, referred to as “underfiller”.
If reference is made to
What can also be seen in this figure is the lower heat transfer plate 51 and the nuts 61 into which the screws 60 come to engage.
A capacitor 100 may be disposed between the connection elements 41 and 42.
The chips 80 and 90 are for example power transistors, for example based on GaN; for example, the source of one is connected to the drain of the other by a centre tap, and the connection elements 41 and 42 are for example connected to the drain of one and to the source of the other, whereas the connection element 43 is connected to the centre tap. The connection elements 44 and 45 are for example connected to the gates of these transistors.
The capacitor 100 is for example a decoupling capacitor, the value of which is for example several nF.
This guide 200 is for example made of plastics material and can be produced with relatively rough manufacturing tolerances by injection moulding.
It may comprise a horizontal base 201 topped by a vertical wall 207 which defines a main cutout 202 and four secondary cutouts 203 to 206, which are disposed around the main cutout 202 in the same way as the connection elements on the module.
The assembly guide has been shown in isolation in
A further description, referring to
When screws are used to retain the assembled housing elements, the manufacturing method may start by disposing the nuts 61 in the corresponding impressions 208, as illustrated in
Then, as illustrated in
In the example considered, the plate 51 is made of copper, but it can be replaced with any suitable dissipator, for example made of another metal or made of a heat-conducting ceramic.
The different elements that make up the module can be placed by any suitable tool, notably a conventional “pick and place” tool.
The lower housing element 10 can then be deposited in the cutout 101.
This element 10 comprises a first central through-cutout 12, intended to receive the first chip 70, and cutouts 13, 14 and 15 that do not pass all the way through for respectively receiving the connection elements 41, 45 and 43. These cutouts 13, 14 and 15 open out into the cutouts 203, 204 and 205, respectively, of the guide 200. Holes 16 are provided for the passage of the screws 60.
In this example, the chip 70 has a parallelepipedal overall shape, the contour of which in top view corresponds substantially to that of the cutout 12.
The chip 70 may have electrical contacts 71, 72 and 73 on its inner face.
The shim 90 has been shown in isolation in
Said shim has a length and width that are adapted for the positioning thereof in the cutout 12 with a small clearance.
It can be made of any electrical insulating material compatible with the conditions of use, for example a ceramic or a polymeric material.
The shim 90 has two lateral openings 91 and 92 and an opening 93 at the end, in the form of notches.
Once the shim 90 has been placed on the chip 70, as illustrated in
The connection elements 41 and 45 can then be placed in the cutouts 203 and 204, respectively, coming to partially cover the contacts 71 and 73, as illustrated in
It may be useful to form, in the cutouts 13 and 15, reliefs 313 and 315 intended to cooperate with corresponding reliefs of the connection elements received in these cutouts, so as to improve the positioning and the retention of the connection elements during the assembly operations. The reliefs 313 or 315 are, for example, in the form of bosses facing each other, and the connection element then has two notches 341 or 343, visible in
Cooperating reliefs in the form of bosses and notches between the housing elements and the connection elements may be present for each of the five connection elements of the module, as is visible in the figures, and will not be described in detail each time hereinafter.
Then, the intermediate housing element 20 can be introduced into the cutout 201 in order to cover the components that are already present.
The element 20 has holes 23 for the passage of the screws 60, and openings 24, 25 and 26 intended to receive the connection elements 44, 42 and 43, respectively.
The opening 26 provides access to the contact 72 of the chip 70.
In the step illustrated in
The connection element 42 can then be introduced in order to cover the capacitor 100, as illustrated in
The connection element 43 is introduced on the opposite side.
When necessary, soldering paste is disposed between the components to be soldered, notably between the capacitor 100 and the connection elements 41 and 42 and between the connection element 43 and the corresponding contact 72 of the chip 70.
The connection element 44 is introduced into a corresponding cutout 27 of the housing element 20.
Then, the housing element 30 is introduced onto the previously installed connection elements, as illustrated in
The housing element 30 has a central opening 33, for example of rectangular shape, as illustrated. This opening 33 provides access to the connection elements 42, 43 and 44.
The housing element 30 comprises holes 32 for the passage of the screws 60.
The second chip 80 can then be disposed in the cutout 33, as illustrated in
This chip 80 has contacts on its face facing towards the interior, which are positioned facing connection elements 42, 43 and 44, respectively.
A soldering paste can be disposed at the interface between the contacts of the chip 80 and the connection elements, so as to enable the soldering during a subsequent heating step.
Once the chip 80 is in place, a second heat transfer plate 50, for example made of copper, can be placed against the chip 80, as illustrated in
Once the screws 60 have been tightened, the assembly can then be taken out of the guide 200 and heated in an oven at a temperature suitable for melting the soldering paste and for producing soldered joints to be effected between the different components of the module.
After soldering, a filling resin can be injected through the orifice 11 and the assembly can be encapsulated, if necessary, in an encapsulation resin, leaving the connection elements accessible, and where appropriate the copper plates when the thermal coupling to a radiator is intended.
The use of a shim 90 is advantageous because it makes it possible to replace the first chip 70 with a second 70′ of different format, without needing to modify the lower housing element 10, as illustrated in
In the example illustrated, the chip 70′ has dimensions that are smaller than those of the chip 70.
The shim 90 can be replaced with a shim 90′ shown in isolation in
In the example considered, the shim 90′ thus comprises two end tabs 94′ situated on either side of the opening 93′, which are intended to engage between the chip 70′ and the short side 12a of the cutout 12.
The shim 90′ also comprises two lateral tabs 95′ which are each configured to be inserted between a long side of the chip 70′ and a long side 12b of the cutout.
The shim 90′ comprises, on the opposite side from the tabs 94′, a stub 96′ arranged so as to engage between the chip 70′ and the other short side 12a of the cutout 12.
Thus, the shim 90′ is positioned precisely in the cutout 12, due to the outer dimensions thereof, whilst retaining the chip 70′ precisely within the cutout 12, at a location suitable for establishing electrical connections with the associated connection elements.
When the chip model used does not have the same electrical contacts as those of the other chips used, the shim can comprise at least one conductive track for electrically connecting at least one corresponding contact of the chip to an associated connection element.
By way of example,
The shim 90″ has, like the other shims 90 and 90′, cutouts 91″, 92″ and 93″ for respectively receiving the ends of the connection elements 41, 43 and 45.
The shim 90″ comprises reliefs for positioning the chip 70″ in the cutout 12, for example lateral tabs 95″ and end portions 96″.
Some of the tabs 95″ may extend up to the adjacent end portion.
The shim 90″ comprises a conductive track 97″, for example in the form of a bend as illustrated, positioned so as to be superposed by an end 97a″ with the contact 73″. The track 97″ extends, at the other end 97b″, into the bottom of the cutout 93″, in order to be connected to the connection element 45.
The track 97″ is for example integrated into the shim 90″ during the manufacturing process for said shim. This may be a metal part inserted into the ceramic or produced by injection moulding or screen printing.
The housing elements 10, 20 and 30, and the shim 90, 90′ or 90″, may be manufactured in such a way as to already exist during the assembly, made of any electrical insulating material(s) compatible with the desired use, for example made of a ceramic, notably by a 3D printing or sintering method. The material is selected in order to thermally withstand the soldering operation for the contacts, the heat released during normal use of the module, and the operating environment; thus the assembly can withstand a temperature of at least 150° C. for example.
To produce the electrical connections, a soldering paste may be used, the invention not being limited to a particular technique for establishing the electrical connections.
The invention is not limited to the examples that have just been described.
For example, the module may comprise more than one shim, and it is in particular possible to use a second shim to enable the mounting, like the second chip, of chips of different sizes and/or implementation of contacts; where appropriate, the intermediate housing element is also modified to facilitate the adaptation of different chip models.
It is also possible to assemble more than two chips within a module, and to use one or more shims that enable the use of different chip models.
The cutouts of the housing elements that are intended to receive the chips may have a shape other than rectangular, for example square or other. It is also possible to have a plurality of cutouts intended to receive respective chips in the same housing element, and to have one or more shims associated with these chips.
Some connection elements, for example the elements 44 and 45 connected to the gates of the transistors, may exit on the same side of the housing to facilitate the control of the module.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2311283 | Oct 2023 | FR | national |
