Patent ID: 12243674

DETAILED DESCRIPTION

The planar transformer1, shown schematically in a particular embodiment inFIG.1and allowing to illustrate the invention, is intended to produce an (electrical) energy conversion, for example a direct/direct, direct/alternating or alternating/direct type voltage conversion.

In the context of the present invention, this planar transformer1is intended to be mounted on a motherboard2, as shown inFIG.2.

Although not exclusively, this planar transformer1shown inFIG.1and/or this motherboard2shown inFIG.2can be used in equipment deployed in stationary installations or in onboard equipment on movable platforms. As an illustration, the planar transformer1and/or the motherboard2can be used in land, sea or air vehicles. They can also be used in weapon systems and in particular in missiles.

They can, in particular, be used in the power supply of calculators.

The planar transformer1comprises at least, as shown inFIG.1:a printed circuit board3. A bare printed circuit board (PCB) is an assembly consisting of an insulating support and flat metallic conductors intended to ensure electrical connections between electronic components that will be arranged on the surface of the support. The printed circuit board3is provided with turns (not shown) specified below. The printed circuit board3is also provided with a connection interface4, at some of its ends, in particular so that it can be simply mounted on a motherboard2(receiver) by welding; anda magnetic core5, preferably made of ferrite. The magnetic core5is mounted on the printed circuit board3in such a way as to cooperate, in the usual way, with the turns which are arranged around this magnetic core5. 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 core5to form an (electrical) energy converter, e.g. a direct/direct, direct/alternating or alternating/direct type voltage converter.

The planar transformer1is produced according to a usual planar technology.

According to the invention, said planar transformer1further comprises at least one electronic component6mounted (in a usual, known and not further described way) on the printed circuit board3.

In a preferred embodiment, said planar transformer1comprises a plurality of electronic components6mounted on the printed circuit board3, as schematically shown inFIG.1. Furthermore, in a particular embodiment of this preferred embodiment, the planar transformer1comprises as many electronic components6as possible, i.e. so as to occupy the entire surface of the (upper) face3A, remaining available on the printed circuit board3. The electronic components6are brazed (in the usual way) to the printed circuit board3.

Preferably, the printed circuit board3comprises, in a usual way, a plurality of superimposed layers. The turns (not shown) are arranged on layers other than an upper layer, and preferably on the assembly of layers other than the upper layer, and said electronic components are arranged on said one upper layer (which is the one closest to the upper face3A).

The upper layer of the printed circuit board3is therefore left without turns in order to be able to place electronic components6on the entire available surface (of the upper face3A) around the magnetic core5.

The printed circuit board3of the planar transformer1is thus produced in such a way as to be able to accommodate numerous electronic components6, without increasing the surface area of the printed circuit board3required for routing the turns of the planar transformer1.

The compactness thus obtained also allows to limit the electromagnetic disturbances, and the electronic components6placed on the printed circuit board3free space on the motherboard2which receives the planar transformer1. This reduces the cost of manufacturing and assembling, as the solution is generic and reusable.

In a particular embodiment, the electronic component or components6are part of a power cell used for the operation of the planar transformer1.

In addition, the connection interface4comprises one or more connection elements for attaching the planar transformer1to the motherboard2, as specified below.

The connection interface4of the planar transformer1can be produced by any usual connection means. However, in one particular embodiment, the connection interface4comprises metallizations7.

The planar transformer1can be used in various applications and be adapted to the constraints imposed by the environment of the electronic board (motherboard2) on which it will be mounted.

It is known that the magnetic components, in particular the transformers, are major contributors to the size, volume, weight and cost of (switch mode) power supplies. Also, the planar transformer1can be used in compact and low cost power electronics equipment.

The planar transformer1can therefore be part of a motherboard2(or electronic board), as shown inFIG.2. The motherboard2comprises, in this case, a printed circuit board8, and a planar transformer1as described above, which is mounted on this printed circuit board8.

The motherboard2furthermore comprises a plurality of electronic components9(shown schematically) which are also mounted (in the usual way) on the printed circuit board8, at various points (on the upper face8A) of the printed circuit board8. Electronic components can also be mounted on the lower face (not shown) of the printed circuit board8.

The planar transformer1, as described above, allows to add electronic components6to the printed circuit board3without increasing its surface area. The electronic components6placed on the planar transformer1allow to save space on the receiving motherboard2, in particular to receive other electronic components9.

The motherboard2also comprises receiving ranges (or surfaces)10which allow the planar transformer1equipped with electronic components6to be received.

In the example shown inFIG.2, the metallizations7(electrically conductive) of the planar transformer1equipped with the electronic components6are superimposed on the reception ranges10(electrically conductive) of the motherboard2so that the planar transformer1can be brazed on the motherboard2.

The metallizations7can be produced in different ways. By way of illustration, the metallizations7can, for example, be produced:according to the embodiment7A as shown inFIG.1, with a square cross-section; oraccording to the embodiment7B as shown inFIG.6A, with a flat face; oraccording to the embodiment7C shown inFIG.6B, with a semi-circular cross-section.

As connection interfaces for the planar transformer1, any connector can be provided that allows the planar transformer1to be brazed to the receiving motherboard2. Connection interfaces without brazing are also possible.

The planar transformer1, as described above, is configured to have an optimized overall dimension and to allow an easy mounting on an electronic board (motherboard2), as specified below.

The motherboard2can be obtained using a (manufacturing and) assembly method such as those described below.

In the context of the present, said assembly method generally comprises at least the following steps (specified below):a production step to form a planar transformer comprising at least one printed circuit board provided with turns and a connection interface;a set of mounting steps comprising:a. a first mounting step to mount electronic components on the printed circuit board of the planar transformer;b. a second mounting step for mounting electronic components on the printed circuit board of a motherboard; andc. a third mounting step to mount the planar transformer on a printed circuit board of a motherboard via the connection interface; andan auxiliary mounting step for mounting a magnetic core on the printed circuit board so as to cooperate with the turns.

In a first embodiment, said (manufacturing and) assembly method comprises, as shown inFIGS.3A,3B,3C,4and5, the following successive steps:the production step to form a planar transformer1comprising at least one printed circuit board3provided with turns and a connection interface4;the auxiliary mounting step for mounting a magnetic core5arranged on the printed circuit board3so as to cooperate with the turns; andsaid set of mounting steps (comprising brazing operations) specified below.

Specifically:the production step consists in forming a printed circuit board3provided with openings11A,11B and11C and metallizations7, as shown inFIG.3A, as well as with turns not shown; andthe auxiliary mounting step consists in mounting a magnetic core5on this printed circuit board3. In the example shown, the magnetic core5is formed by two elements12and13, as shown inFIG.3B.

The element12is E-shaped with branches14A,14B and14C. The element12is intended to be mounted on one face (upper face3A) of the printed circuit board3such that the branches14A,14B and14C pass through the openings11A,11B and11C respectively. The (I-shaped) element13is brought to the lower face3B (i.e., opposite the face3A) of the printed circuit board3and is attached to the branches14A,14B and14C of this element12(passing through the openings11A,11B and11C) so as to obtain the core5mounted on the printed circuit board3, as shown inFIG.3C.

In the context of the present invention, any usual type of planar ferrite core can be used. Thus, the elements12and13, instead of being a pair of elements of forms E and I, can have other possible forms, such as pairs of forms E and E, or ER or EQ cores.

The set of mounting steps comprising:the first mounting step for mounting electronic components6on the printed circuit board3of the planar transformer1;the second mounting step for mounting electronic components9on the printed circuit board8of the motherboard2; andthe third mounting step for mounting the planar transformer1on the printed circuit board8of the motherboard2via the connection interface4. For this purpose, the printed circuit board8is provided (as shown inFIG.4) with an opening15intended for receiving the element13of the magnetic core5of the planar transformer1. The lower face3B of the printed circuit board3is brought into contact with the upper side8A of the printed circuit board8in such a way that the metallizations7of the printed circuit board3are superimposed on the receiving ranges10of the printed circuit board8. The metallizations7(forming the connection interface4) are brazed to the receiving ranges10.

The usual steps of such an assembly method are known and are not described further below.

Preferably, in this first embodiment, the assembly method comprises a single brazing phase (for the set of mounting steps) during which the electronic components6of the planar transformer1are brazed onto its printed circuit board3, the planar transformer1is brazed onto the printed circuit board8of the motherboard2and the electronic components9are brazed onto the printed circuit board8of the motherboard2. This allows to avoid an additional operation (to assemble the motherboard2) that exists in the prior art.

This preferred embodiment of the method therefore allows the motherboard2and the planar transformer1to be manufactured and assembled in a single brazing sequence (or phase). This method comprises a single phase of mounting the electronic components and a single phase of testing for the whole motherboard2(printed circuit board8and planar transformer1). Thus, the manufacturing cost can be reduced.

It is also possible to produce a brazing sequence for any two of the three mounting steps and another brazing sequence for the other mounting step, regardless of the order of the mounting steps and regardless of the order of the brazing sequences (the two-step sequence can be carried out first or second).

In a variant of this first embodiment, the steps of the set of mounting steps are implemented sequentially in one of the following orders:the first mounting step, the second mounting step, the third mounting step;the first mounting step, the third mounting step, the second mounting step;the second mounting step, the first mounting step, the third mounting step;the second mounting step, the third mounting step, the first mounting step;the third mounting step, the first mounting step, the second mounting step;the third mounting step, the second mounting step, the first mounting step.

This variant embodiment allows to obtain the same motherboard2(with reduced overall dimension) as the one obtained with the above-mentioned preferred embodiment, but with several brazing steps.

According to one of the possibilities, the electronic components6of the planar transformer1are brazed onto the printed circuit board3of the planar transformer1firstly. Then, the assembled planar transformer1is brazed to the motherboard2(receiver), for example together with the electronic components9of this motherboard2. The electronic components6of the planar transformer1are therefore subjected to a remelting.

Further in a second embodiment (not shown), said steps are implemented in the following order: the production step, the auxiliary mounting step, the set of mounting steps.

In a first variant of this second embodiment, the steps of the set of mounting steps are implemented sequentially, in one of the following orders:the first step of mounting, the second step of mounting, the third step of mounting;the first mounting step, the third mounting step, the second mounting step;the second mounting step, the first mounting step, the third mounting step;the second mounting step, the third mounting step, the first mounting step;the third mounting step, the first mounting step, the second mounting step;the third mounting step, the second mounting step, the first mounting step.

Furthermore, in a second variant of this second embodiment, the steps of the set of mounting steps are implemented together in a single brazing sequence. This second variant allows to simplify the assembly method and reduces the assembly time and cost.

It is also possible to produce a brazing sequence for any two of the three mounting steps and another brazing sequence for the other mounting step, regardless of the order of the mounting steps and regardless of the order of the brazing sequences (the two-step sequence can be carried first or second).

Furthermore, in a third embodiment (not shown), the assembly method steps are implemented in the following order:firstly the production step;and then the auxiliary mounting step which is implemented during the set of mounting steps.

In this third embodiment, the auxiliary mounting step and the steps of the set of mounting steps are implemented sequentially, in one of the following orders:the first mounting step, the auxiliary mounting step, the second mounting step, the third mounting step;the first mounting step, the auxiliary mounting step, the third mounting step, the second mounting step;firstly the first mounting step, then the auxiliary mounting step, and finally the second mounting step and the third mounting step which are implemented together in a single (brazing) step.

The planar transformer1and/or the motherboard2and/or the manufacturing and assembly method, as described above, thus have many advantages, and in particular:an overall dimension optimization. Indeed:a. the surface of printed circuit board3intended for the turns of the planar transformer1is also used to place electronic components6;b. we gain surface area on the motherboard2;an improvement of the assembly method. The method is integrated by allowing to produced, in the same method, the equipped planar transformer1and its receiver board (i.e. said motherboard2);an improvement in the development method. Indeed, the planar transformer1and the motherboard2offer 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 method such as daughterboard/motherboard);a miniaturization with:a. an optimization of the available surface for the electronic components; andb. an integrated solution;c. a generic character with:d. a creation of low-cost reusable functions; ande. a reusable solution; anda simplification of the method, compared to independent physical modules, with a low serial cost.