Motherboard comprising a planar transformer equipped with components and method for assembling such a motherboard

Abstract

- A planar transformer (1) comprises at least one printed circuit board (3) provided with turns and with a connection interface (4), and also a magnetic core (5) arranged on the printed circuit board (3) so as to interact with the turns in order to form an energy converter, said planar transformer (1) also comprising one, and preferably a plurality of, electronic components (6) mounted on the printed circuit board (3), said planar transformer (1) being of optimized size and suitable for arrangement on a printed circuit board (8) of a motherboard (2), said printed circuit board also being provided with electronic components (9).

Description

[0001] Planar transformer equipped with components, motherboard including such a planar transformer and method for assembling such a motherboard.

[0002] TECHNICAL FIELD

[0003] The present invention relates to a planar transformer equipped with components, a motherboard comprising such a planar transformer and a method for assembling such a motherboard.

[0004] STATE OF THE ART

[0005] This planar transformer and / or motherboard can be used in a wide variety of applications, both in equipment deployed in fixed installations and in equipment mounted on mobile platforms. For example, the planar transformer can be used in land, sea, or air vehicles, or in weapon systems, particularly missiles. To this end, such a planar transformer must be resistant to the harsh mechanical environments likely to be encountered in such applications and must be able to easily adapt to the required constraints of mass, volume, and mechanical interfaces.

[0006] A planar transformer typically comprises at least one magnetic core and turns arranged around it, forming a primary and a secondary winding. These turns work together with the magnetic core to form a power converter (for example, a DC / DC, DC / AC, or AC / DC voltage converter). The planar transformer also includes connection means for mounting it on a circuit board.

[0007] A device (or transformer) of this type is known from document EP-0 741 395. It comprises turns formed on a printed circuit board, around which a ferrite magnetic core is positioned. This device can be mounted on a circuit board using conductive pads located on the board. It is soldered to these pads. Such a device is bulky. Indeed, the transformer's printed circuit board is used solely to create the turns. It is therefore not suitable for applications with significant space constraints.

[0008] We also know, from document EP-1 085 535, of such a device (or transformer) which comprises a stack of basic and high-current turns, around which a ferrite magnetic core is positioned. This device has high-current conductive terminals and connecting pins. These connection means allow the device to be soldered onto a circuit board. This device has the same drawbacks as the previous one and is therefore not suitable for applications with significant space constraints. Furthermore, such a device requires several assembly operations, as it requires different components to form the transformer turns.

[0009] Furthermore, US patent document 6,335,671 describes a device (or transformer) of this type comprising several conductive sheets coated with an insulator (forming the turns), around which a ferrite magnetic core is positioned. This device has connection pins ending in conductive terminals, allowing the device to be soldered onto a circuit board. This device presents the same drawbacks as the previous devices and is therefore not suitable for applications with significant space constraints. Moreover, such a device also requires several assembly operations, as it requires multiple components to form the transformer turns.

[0010] Furthermore, we know, from document EP-1 723 657, of a magnetic device to be mounted on a planar surface comprising a printed circuit.

[0011] DESCRIPTION OF THE INVENTION

[0012] The present invention aims to overcome at least some of the aforementioned drawbacks, and is particularly intended to optimize the size. It relates to a planar transformer comprising at least one printed circuit board provided with turns and a connection interface, as well as a magnetic core arranged on the printed circuit board so as to cooperate with the turns.

[0013] According to the invention, said planar transformer further comprises at least one electronic component mounted on the printed circuit board.

[0014] In a preferred embodiment, said planar transformer comprises a plurality of electronic components mounted on the printed circuit board.

[0015] Thus, thanks to the invention, one or more electronic components (and preferably as many as possible) are placed directly on the printed circuit board of the planar transformer. This avoids wasting space on the planar transformer itself and saves space on a motherboard containing such a planar transformer, as explained below.

[0016] These features allow for the optimization of the footprint of the planar transformer and / or a motherboard equipped with such a planar transformer. This planar transformer also offers other advantages, detailed below.

[0017] Preferably, the printed circuit board (of the planar transformer) comprises a plurality of superimposed layers, the turns are arranged on layers (of said plurality of superimposed layers) other than a top layer, and said electronic component(s) are arranged on said top layer. This allows the turns for operation with the magnetic core to be made (in layers other than the top layer), while still leaving space to mount the electronic component(s) (on the top layer).

[0018] In a particular embodiment, the electronic component(s) (mounted on the printed circuit board of the planar transformer) are part of a power cell used for the operation of the planar transformer.

[0019] The connection interface for the planar transformer can be implemented by any conventional means. However, in one particular embodiment, the connection interface includes metallization. The present invention also relates to a motherboard comprising a printed circuit board, referred to as the motherboard board, and at least one planar transformer such as that described above, which is mounted on this printed circuit board.

[0020] Preferably, the motherboard also includes a plurality of electronic components mounted on the motherboard printed circuit board.

[0021] The arrangement of electronic components on the planar transformer, preferably by placing a maximum of electronic components directly on the said printed circuit board of the planar transformer, makes it possible to not lose any surface area on the planar transformer and to gain some on the motherboard (receiver) on which these electrical components would otherwise have had to be mounted.

[0022] The present invention also relates to a method for assembling a motherboard as described above.

[0023] According to the invention, said assembly method comprises at least the following steps:

[0024] - a manufacturing step to form a planar transformer comprising at least one printed circuit board with turns and a connection interface;

[0025] - a set of assembly steps including:

[0026] • a first assembly step to mount electronic components on the printed circuit board of the planar transformer;

[0027] • a second assembly stage to mount electronic components onto the printed circuit board of a motherboard; and

[0028] • a third assembly step to mount the planar transformer onto the motherboard's printed circuit board via the connection interface; and

[0029] - an auxiliary assembly step to mount a magnetic core on the printed circuit board of the planar transformer so as to cooperate with the turns.

[0030] In a first embodiment, these steps are carried out in the following order: the implementation step, the assembly steps, the auxiliary assembly step. In a first variant of this first embodiment, the assembly steps are carried out successively, in one of the following orders:

[0031] - the first assembly stage, the second assembly stage, the third assembly stage;

[0032] - the first assembly stage, the third assembly stage, the second assembly stage;

[0033] - the second assembly stage, the first assembly stage, the third assembly stage; - the second assembly stage, the third assembly stage, the first assembly stage;

[0034] - the third assembly stage, the first assembly stage, the second assembly stage;

[0035] - the third assembly stage, the second assembly stage, the first assembly stage.

[0036] In a second variant of this first embodiment, the assembly steps are carried out together in a single soldering sequence. This second variant simplifies the assembly process and reduces both assembly time and cost.

[0037] Furthermore, in a third variant of this first embodiment, for the assembly steps, a soldering sequence is performed for any two of the three assembly steps and another soldering sequence for the other assembly step. Moreover, in a second embodiment, these steps are implemented in the following order: the assembly step, the auxiliary assembly step, and the assembly steps.

[0038] In a first variant of this second embodiment, the steps of the assembly sequence are implemented successively, according to one of the following orders:

[0039] - the first assembly stage, the second assembly stage, the third assembly stage; - the first assembly stage, the third assembly stage, the second assembly stage;

[0040] - the second assembly stage, the first assembly stage, the third assembly stage; - the second assembly stage, the third assembly stage, the first assembly stage;

[0041] - the third assembly stage, the first assembly stage, the second assembly stage;

[0042] - the third assembly stage, the second assembly stage, the first assembly stage.

[0043] In a second variant of this second embodiment, the assembly steps are carried out together in a single soldering sequence. This second variant simplifies the assembly process and reduces assembly time and cost.

[0044] Furthermore, in a third variant of this second embodiment, for the assembly steps, a soldering sequence is performed for any two of the three assembly steps and another soldering sequence for the other assembly step. Moreover, in a third embodiment, these steps are implemented in the following order: first the assembly step, then the auxiliary assembly step that is implemented during the assembly steps.

[0045] Advantageously, the auxiliary assembly step and the steps of the assembly sequence are implemented successively, according to one of the following orders:

[0046] - the first assembly stage, the auxiliary assembly stage, the second assembly stage, the third assembly stage;

[0047] - the first assembly stage, the auxiliary assembly stage, the third assembly stage, the second assembly stage;

[0048] - The first assembly step, the auxiliary assembly step, then the second assembly step and the third assembly step are implemented in a single step. BRIEF DESCRIPTION OF THE FIGURES

[0049] The figures in the attached drawing will clearly illustrate how the invention can be implemented. In these figures, identical reference numerals designate similar elements.

[0050] Figure 1 is a schematic, perspective (top view) view of a particular embodiment of a planar transformer.

[0051] Figure 2 is a schematic, perspective (top view) view of a particular embodiment of a motherboard equipped with the planar transformer of Figure 1.

[0052] Figures 3A, 3B, 3C, 4 and 5 represent different successive stages of a motherboard assembly process.

[0053] Figure 3A is a schematic, perspective view of a bare printed circuit board with openings.

[0054] Figure 3B is a schematic, perspective view of the printed circuit board of Figure 3A and two elements (or parts) of a magnetic core.

[0055] Figure 3C is a schematic, perspective view of the printed circuit board of Figure 3B on which the magnetic core, formed from the said two parts of the magnetic core, is mounted.

[0056] Figure 4 is a schematic, perspective view of the printed circuit board of Figure 3C and of a printed circuit board of a motherboard.

[0057] Figure 5 is an identical view to that of Figure 2, representing the assembled motherboard.

[0058] Figure 6A is a schematic, perspective view of a portion of the printed circuit board including metallizations of a connection interface, conforming to a first embodiment variant.

[0059] Figure 6B is a schematic, perspective view of a portion of the printed circuit board including metallizations of a connection interface, conforming to a second embodiment variant.

[0060] DETAILED DESCRIPTION The planar transformer 1, schematically represented in a particular embodiment in Figure 1 and illustrating the invention, is intended to carry out an energy (electrical) conversion, for example a voltage conversion of the direct / direct, direct / alternating or alternating / direct type.

[0061] Within the framework of the present invention, this planar transformer 1 is intended to be mounted on a motherboard 2, as shown in Figure 2.

[0062] Although not exclusively, this planar transformer 1 shown in Figure 1 and / or this motherboard 2 shown in Figure 2 can be used in equipment deployed in fixed installations or in equipment mounted on mobile platforms. For example, the planar transformer 1 and / or the motherboard 2 can be used in land, sea, or air vehicles. They can also be used in weapon systems, particularly missiles.

[0063] In particular, they can be used in powering computers.

[0064] The planar transformer 1 comprises at least, as shown in Figure 1:

[0065] - a printed circuit board 3. A bare printed circuit board (PCB) is an assembly consisting of an insulating substrate and flat metallic conductors designed to provide electrical connections between electronic components that will be arranged on the surface of the substrate. The printed circuit board 3 has turns (not shown) specified below. The printed circuit board 3 also has a connection interface 4 at some of its ends, notably to allow it to be easily mounted onto a motherboard 2 (receiving board) by soldering; and

[0066] - a magnetic core 5, preferably made of ferrite. The magnetic core 5 is mounted on the printed circuit board 3 so as to cooperate, in the usual way, with the turns which are arranged around this magnetic core 5. The turns form one or more primary windings and one or more secondary windings which cooperate (in the usual, known and not further described way) with the magnetic core 5 to form an (electrical) energy converter, for example a DC / DC, DC / AC or AC / DC voltage converter.

[0067] The planar transformer 1 is made using a conventional planar technology.

[0068] According to the invention, said planar transformer 1 further comprises at least one electronic component 6 mounted (in a usual, known and not further described manner) on the printed circuit 3.

[0069] In a preferred embodiment, the planar transformer 1 comprises a plurality of electronic components 6 mounted on the printed circuit board 3, as schematically represented in Figure 1. Furthermore, in a particular embodiment of this preferred embodiment, the planar transformer 1 comprises as many electronic components 6 as possible, i.e., so as to occupy the entire surface of the (upper) face 3A, remaining available on the printed circuit board 3. The electronic components 6 are soldered (in the usual way) onto the printed circuit board 3.

[0070] Preferably, the printed circuit board 3 comprises, in the usual way, a plurality of superimposed layers. The turns (not shown) are arranged on layers other than a top layer, and preferably on all layers other than the top layer, and said electronic component(s) are arranged on said top layer (which is the one closest to the top face 3A).

[0071] The top printed circuit board layer 3 is therefore left without turns in order to be able to place electronic components 6 on the entire available surface (of the top face 3A) around the magnetic core 5.

[0072] The printed circuit board 3 of the planar transformer 1 is thus made in such a way as to be able to place many electronic components 6 on it, without increasing the printed circuit board area 3 required for routing the turns of the planar transformer 1.

[0073] The resulting compactness also helps to limit electromagnetic interference, and the electronic components 6 placed on the printed circuit board 3 free up space on the motherboard 2, which houses the planar transformer 1. Manufacturing and assembly costs are thus reduced, as the solution is generic and reusable. In one particular embodiment, the electronic component(s) 6 are part of a power cell used for the operation of the planar transformer 1.

[0074] In addition, the connection interface 4 includes one or more connection elements for fixing the planar transformer 1 to the motherboard 2, as specified below.

[0075] The connection interface 4 of the planar transformer 1 can be made by any conventional means of connection. However, in a particular embodiment, the connection interface 4 includes metallizations 7.

[0076] The planar transformer 1 can be used in various applications and adapted to the constraints imposed by the environment of the electronic board (motherboard 2) on which it will be mounted.

[0077] It is known that magnetic components, particularly transformers, are major contributors to the size, volume, weight, and cost of (switch-mode) power supplies. Therefore, the planar transformer 1 can be used in compact and low-cost power electronics equipment.

[0078] The planar transformer 1 can therefore be part of a motherboard 2 (or electronic board), as shown in Figure 2. The motherboard 2 has, in this case, a printed circuit board 8, and a planar transformer 1 as described above, which is mounted on this printed circuit board 8.

[0079] The motherboard 2 also includes a plurality of electronic components 9 (shown schematically) which are also mounted (in the usual way) on the printed circuit board 8, at various locations (on the upper face 8A) of the printed circuit board 8. Electronic components can also be mounted (in the usual way) on the lower face (not shown) of the printed circuit board 8.

[0080] The planar transformer 1, as described above, allows electronic components 6 to be added to the printed circuit board 3 without increasing its surface area. The electronic components 6 placed on the planar transformer 1 save space on the receiving motherboard 2, particularly for accommodating other electronic components 9. The motherboard 2 also has receiving pads (or surfaces) 10 that allow the planar transformer 1 equipped with electronic components 6 to be accommodated.

[0081] In the example shown in Figure 2, the metallizations 7 (electrically conductive) of the planar transformer 1 equipped with the electronic components 6 are superimposed on the receiving areas 10 (electrically conductive) of the motherboard 2 so that the planar transformer 1 can be soldered onto the motherboard 2.

[0082] Metallizations 7 can be carried out in various ways. For example, metallizations 7 can be achieved by:

[0083] - according to embodiment 7A shown in Figure 1, with a square cross-section; or

[0084] - according to embodiment 7B shown in Figure 6A, with a flat face; or

[0085] - according to embodiment 7C shown in figure 6B, with a semi-circular section.

[0086] As connection interfaces for the planar transformer 1, any connector allowing the planar transformer 1 to be soldered to the receiving motherboard 2 can be used. Solderless connection interfaces are also possible.

[0087] The planar transformer 1, as described above, is configured to have an optimized footprint and to allow easy mounting on an electronic board (motherboard 2), as specified below.

[0088] Motherboard 2 can be obtained using a (manufacturing and) assembly process such as those described below.

[0089] Within the framework of this document, the assembly process generally comprises at least the following steps (specified below):

[0090] - a manufacturing step to form a planar transformer comprising at least one printed circuit board with turns and a connection interface;

[0091] - a set of assembly steps including:

[0092] • a first assembly step to mount electronic components onto the printed circuit board of the planar transformer; • a second assembly step to mount electronic components onto the printed circuit board of a motherboard; and

[0093] • a third assembly step to mount the planar transformer onto a printed circuit board of a motherboard via the connection interface; and

[0094] - an auxiliary assembly step to mount a magnetic core onto the printed circuit board so as to cooperate with the turns.

[0095] In a first embodiment, said manufacturing and assembly process comprises, as shown in Figures 3A, 3B, 3C, 4 and 5, the following successive steps:

[0096] - the manufacturing step to form a planar transformer 1 comprising at least one printed circuit 3 provided with turns and a connection interface 4;

[0097] - the auxiliary assembly step for mounting a magnetic core 5 arranged on the printed circuit board 3 so as to cooperate with the turns; and

[0098] - said set of assembly steps (including brazing operations) specified below.

[0099] More precisely :

[0100] - the manufacturing step consists of forming a printed circuit board 3 provided with openings 11A, 11B and 11C and metallizations 7, as shown in figure 3A, as well as turns not shown; and

[0101] - the auxiliary assembly step consists of mounting a magnetic core 5 on this printed circuit board 3. In the example shown, the magnetic core 5 is formed of two elements 12 and 13, as shown in figure 3B.

[0102] Element 12 is E-shaped with branches 14A, 14B, and 14C. Element 12 is intended to be mounted on one face (top face 3A) of the printed circuit board 3 such that branches 14A, 14B, and 14C pass through openings 11A, 11B, and 11C, respectively. Element 13 (I-shaped) is brought onto the bottom face 3B (i.e., opposite face 3A) of the printed circuit board 3 and is fixed to branches 14A, 14B, and 14C of this element 12 (passing through openings 11A, 11B, and 11C) so as to obtain the core 5 mounted on the printed circuit board 3, as shown in Figure 3C.

[0103] Within the framework of the present invention, any common type of planar ferrite core can be used. Thus, the elements 12 and 13, instead of being a pair of elements of shapes E and I, can have other possible shapes, such as, for example, pairs of shapes E and E, or ER or EQ cores.

[0104] The assembly steps include:

[0105] - the first assembly step to mount electronic components 6 onto the printed circuit board 3 of the planar transformer 1;

[0106] - the second assembly step to mount electronic components 9 onto the printed circuit board 8 of the motherboard 2; and

[0107] - The third assembly step involves mounting the planar transformer 1 onto the printed circuit board 8 of the motherboard 2 via the connection interface 4. To do this, the printed circuit board 8 is provided (as shown in Figure 4) with an opening 15 to receive the element 13 of the magnetic core 5 of the planar transformer 1. The lower face 3B of the printed circuit board 3 is brought into contact with the upper face 8A of the printed circuit board 8 such that the metallizations 7 of the printed circuit board 3 are superimposed on the receiving pads 10 of the printed circuit board 8. The metallizations 7 (forming the connection interface 4) are soldered onto the receiving pads 10.

[0108] The usual steps of such an assembly process are known and are not described further below.

[0109] Preferably, in this first embodiment, the assembly process comprises a single soldering phase (for all assembly steps) during which the electronic components 6 of the planar transformer 1 are soldered onto its printed circuit board 3, the planar transformer 1 is soldered onto the printed circuit board 8 of the motherboard 2 and the electronic components 9 are soldered onto the printed circuit board 8 of the motherboard 2. This avoids an additional operation (to assemble the motherboard 2) which exists in the prior art.

[0110] This preferred embodiment of the process allows the motherboard 2 and the planar transformer 1 to be manufactured and assembled in a single soldering sequence (or phase). This process comprises a single phase for assembling the electronic components and a single phase for testing the entire motherboard 2 (printed circuit board 8 and planar transformer 1). Thus, the manufacturing cost can be reduced. It is also possible to perform one soldering sequence for any two of the three assembly steps and another soldering sequence for the remaining assembly step, regardless of the order of the assembly steps or the order of the soldering sequences (the two-step sequence can be performed first or second).

[0111] In a variant of this first embodiment, the steps of the assembly sequence are implemented successively, according to one of the following orders:

[0112] - the first assembly stage, the second assembly stage, the third assembly stage;

[0113] - the first assembly stage, the third assembly stage, the second assembly stage;

[0114] - the second assembly stage, the first assembly stage, the third assembly stage; - the second assembly stage, the third assembly stage, the first assembly stage;

[0115] - the third assembly stage, the first assembly stage, the second assembly stage;

[0116] - the third assembly stage, the second assembly stage, the first assembly stage.

[0117] This embodiment variant allows obtaining the same motherboard 2 (with reduced footprint) as that obtained with the aforementioned preferred embodiment, but with several soldering steps.

[0118] According to one possibility, the electronic components 6 of the planar transformer 1 are first soldered onto the printed circuit board 3 of the planar transformer 1. Then, the assembled planar transformer 1 is soldered onto the motherboard 2 (receiver), for example, simultaneously with the electronic components 9 of this motherboard 2. The electronic components 6 of the planar transformer 1 are thus reflow-soldered. Furthermore, in a second embodiment (not shown), these steps are carried out in the following order: the assembly step, the auxiliary assembly step, and the assembly steps. In a first variant of this second embodiment, the assembly steps are carried out successively, in one of the following orders:

[0119] - the first assembly stage, the second assembly stage, the third assembly stage;

[0120] - the first assembly stage, the third assembly stage, the second assembly stage;

[0121] - the second assembly stage, the first assembly stage, the third assembly stage; - the second assembly stage, the third assembly stage, the first assembly stage;

[0122] - the third assembly stage, the first assembly stage, the second assembly stage;

[0123] - the third assembly stage, the second assembly stage, the first assembly stage.

[0124] Furthermore, in a second variant of this second embodiment, the assembly steps are carried out together in a single soldering sequence. This second variant simplifies the assembly process and reduces both assembly time and cost.

[0125] It is also possible to carry out one soldering sequence for any two of the three assembly steps and another soldering sequence for the other assembly step, regardless of the order of the assembly steps and regardless of the order of the soldering sequences (the two-step sequence can be carried out first or second).

[0126] Furthermore, in a third embodiment (not shown), the assembly process steps are carried out in the following order:

[0127] - first the implementation stage;

[0128] - then the auxiliary assembly step which is implemented during the set of assembly steps.

[0129] In this third embodiment, the auxiliary assembly step and the steps of the assembly set are implemented successively, according to one of the following orders: - the first assembly step, the auxiliary assembly step, the second assembly step, the third assembly step;

[0130] - the first assembly stage, the auxiliary assembly stage, the third assembly stage, the second assembly stage;

[0131] - first the first assembly stage, then the auxiliary assembly stage, and finally the second assembly stage and the third assembly stage which are implemented together in a single step (of brazing).

[0132] The planar transformer 1 and / or the motherboard 2 and / or the manufacturing and assembly process, as described above, thus offer numerous advantages, and in particular:

[0133] - Optimizing space. Indeed:

[0134] • the printed circuit board surface 3 intended for the turns of the planar transformer 1 is also used to place electronic components 6;

[0135] • We gain surface area on motherboard 2;

[0136] - an improvement in the assembly process. The process is integrated by allowing the planar transformer 1 equipped and its receiver board (namely the said motherboard 2) to be produced in the same process;

[0137] - an improvement in the development process. Indeed, the planar transformer 1 and the motherboard 2 offer the advantages of a reusable physical power supply module (validation, routing, environments), without the disadvantages (additional cost of assembling the physical module in a separate industrial process such as daughterboard / motherboard);

[0138] - miniaturization with:

[0139] • optimization of the available surface area for electronic components; and

[0140] • an integrated solution;

[0141] - a generic character with:

[0142] • the creation of reusable functions at low cost; and

[0143] • a reusable solution; and

[0144] - a simplification of the process, compared to independent physical modules, with a low series cost.

Claims

DEMANDS 1. Motherboard comprising a printed circuit board (8) referred to as the motherboard and at least one planar transformer (1) which is mounted on this printed circuit board (8) of the motherboard, as well as a plurality of electronic components (10) which are also mounted on the printed circuit board (8) of the motherboard, the planar transformer (1) comprising at least one printed circuit board (3) provided with turns and a connection interface (4), as well as a magnetic core (5) arranged on the printed circuit board (3) so as to cooperate with the turns, the planar transformer (1) further comprising at least one electronic component (6) mounted on the printed circuit board (3).

2. Motherboard according to claim 1, characterized in that the planar transformer (1) comprises a plurality of electronic components (6) mounted on the printed circuit board (3).

3. Motherboard according to any one of claims 1 and 2, characterized in that the printed circuit board (3) comprises a plurality of superimposed layers, in that the turns are arranged on layers other than a top layer, and in that said electronic component(s) are arranged on said top layer.

4. Motherboard according to any one of the preceding claims, characterized in that the electronic component(s) (6) mounted on the printed circuit board (3) are part of a power cell used for the operation of the planar transformer (1).

5. Motherboard according to any one of the preceding claims, characterized in that the connection interface (4) includes metallizations (7).

6. A method for assembling a motherboard according to any one of claims 1 to 5, characterized in that it comprises at least the following steps: - a manufacturing step to form a planar transformer (1) comprising at least one printed circuit board (3) provided with turns and a connection interface (4); - a set of assembly steps including: • a first assembly step to mount electronic components (6) on the printed circuit board (3) of the planar transformer (1); • a second assembly step to mount electronic components (9) onto the printed circuit board (8) of a motherboard (2); and • a third assembly step to mount the planar transformer (1) onto the printed circuit board (8) of the motherboard (2) via the connection interface (4); and - an auxiliary assembly step to mount a magnetic core (5) on the printed circuit board (3) of the planar transformer (1) so as to cooperate with the turns.

7. Assembly method according to claim 6, characterized in that said steps are carried out in the following order: the realization step, the set of assembly steps, the auxiliary assembly step.

8. Assembly method according to claim 7, characterized in that the steps of the assembly set are carried out successively, in one of the following orders: - the first assembly stage, the second assembly stage, the third assembly stage; - the first assembly stage, the third assembly stage, the second assembly stage; - the second assembly stage, the first assembly stage, the third assembly stage; - the second assembly stage, the third assembly stage, the first assembly stage; - the third assembly stage, the first assembly stage, the second assembly stage; - the third assembly stage, the second assembly stage, the first assembly stage.

9. Assembly method according to claim 7, characterized in that the steps of the assembly set of steps are carried out together in a single brazing sequence.

10. An assembly method according to claim 9, characterized in that, for the steps in the assembly sequence, a brazing sequence is performed for any two of the three assembly steps and another brazing sequence for the other assembly step.

11. An assembly method according to claim 6, characterized in that said steps are carried out in the following order: the fabrication step, the auxiliary assembly step, the assembly sequence.

12. Assembly method according to claim 11, characterized in that the steps of the assembly step set are carried out successively, in one of the following orders: - the first assembly stage, the second assembly stage, the third assembly stage; - the first assembly stage, the third assembly stage, the second assembly stage; - the second assembly stage, the first assembly stage, the third assembly stage; - the second assembly stage, the third assembly stage, the first assembly stage; - the third assembly stage, the first assembly stage, the second assembly stage; - the third assembly stage, the second assembly stage, the first assembly stage.

13. Assembly method according to claim 12, characterized in that the steps of the assembly set of steps are carried out together in a single brazing sequence.

14. Assembly method according to claim 12, characterized in that, for the steps of the assembly step set, a brazing sequence is carried out for any two of the three assembly steps and another brazing sequence for the other assembly step.

15. Assembly method according to claim 6, characterized in that said steps are carried out in the following order: first the manufacturing step, then the auxiliary assembly step which is implemented during the assembly sequence, and in that the auxiliary assembly step and the steps of the assembly sequence are implemented successively, according to one of the following orders: - the first assembly stage, the auxiliary assembly stage, the second assembly stage, the third assembly stage; - the first assembly stage, the auxiliary assembly stage, the third assembly stage, the second assembly stage; - the first assembly stage, the auxiliary assembly stage, then the second assembly stage and the third assembly stage which are implemented in a single step.

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