Encapsulated magnetic component

Abstract

The invention relates to a magnetic component comprising: - an active portion comprising: o a printed circuit board extending along a first plane; o a first inductive element formed by a first winding of an electrical conductor deposited on the printed circuit board; o a ferromagnetic core positioned with respect to the first inductive element so as to form a closed magnetic circuit capable of guiding a magnetic field induced by the first inductive element; and an encapsulation structure configured to encapsulate the active portion and comprising a housing made of a first material having a first Young's modulus; wherein the housing is filled with a filling resin having a second Young's modulus lower than the first Young's modulus; and the ferromagnetic core is moulded in the resin inside the housing so as to separate the ferromagnetic core from the housing.

Description

DESCRIPTION Title of the invention: Encapsulated Magnetic Component

[0001] The present invention relates to planar magnetic components, such as inductors, coupled inductors and transformers. More specifically, the invention relates to an innovative technique for encapsulating planar magnetic components.

[0002] Traditional magnetic components often have limitations in terms of size, weight, and performance in the extreme environments of space. Currently available solutions are often based on conventional configurations that are not optimized for space-specific constraints, including size and weight reduction, radiation resistance, and thermal stability.

[0003] The present invention relates to planar magnetic components designed specifically to meet the rigorous requirements of the space domain. These components exploit advanced design and manufacturing technologies to offer improved performance, significant reduction in size and weight, reduced power consumption, reduced electrical and magnetic losses and increased thermal stability.

[0004] Generally speaking, a state-of-the-art planar magnetic component comprises an inductive element made on a printed circuit board and composed of windings consisting of several turns. These windings are designed to generate a magnetic field that can be used for energy storage (inductance) or transfer (transformer) purposes. The planar magnetic component also incorporates a ferromagnetic core that serves to channel the magnetic field, thus forming a magnetic circuit. This core can be manufactured from different materials depending on the specific application, taking into account criteria such as power, frequency, price, size and required performance. The assembly formed by the printed circuit board, the inductive element, and the ferromagnetic core are molded in an encapsulation structure made of a solidified rigid resin.This type of planar magnetic component presents a technical problem related to the integration of the ferromagnetic core into a rigid encapsulating resin. During operation, the ferromagnetic core. undergoes shape variations at its external surface due to the magnetostrictive effect. The magnetostrictive effect is a physical phenomenon in which a material changes shape in response to an applied magnetic field. When a magnetostrictive material is exposed to a magnetic field, the magnetic domains of the material realign, resulting in a change in its crystalline structure. This change in structure causes mechanical deformation of the material, which results in a shape change observable at the macroscopic scale. However, the ferromagnetic core undergoes mechanical stress, applied by the contact surface with the rigid encapsulation structure, in response to the magnetostrictive deformations. Said mechanical stress significantly degrades the performance of the planar magnetic component during operation. The degradation in performance of the magnetic component results in: - a considerable increase in magnetic resistance and therefore iron losses; - and a considerable reduction in the equivalent inductance of the magnetic component, up to 90% compared to a theoretical inductance value calculated during design.

[0005] To overcome the limitations of existing solutions, the invention proposes a planar magnetic component molded into an innovative encapsulation structure. The encapsulation structure according to the invention is composed of a rigid housing filled with a material having high elasticity so as to release the mechanical stress applied by the encapsulation structure on the molded ferromagnetic core. The elastic material further ensures thermal compatibility with the rigid housing.

[0006] In addition, the rigid housing of the encapsulation structure is dimensioned so that the printed circuit board and the ferromagnetic core can be inserted into the rigid housing and thus have a contactless mechanical embedding connection between the rigid housing and the ferromagnetic core. This eliminates the mechanical stress applied to the ferromagnetic core in response to deformations resulting from the magnetostrictive effect. Thus, the magnetic component according to the invention solves the problems of performance degradation. aforementioned electromagnetic (magnetic guidance and equivalent inductance) without reducing the robustness of the magnetic component in the face of constraints (radiation, temperatures, particles, etc.) relating to a space application.

[0007] The invention relates to a magnetic component comprising: an active part comprising: o a printed circuit extending along a first plane; o a first inductive element produced by a first winding of an electrical conductor deposited on the printed circuit; o a ferromagnetic core positioned relative to said first inductive element so as to form a closed magnetic circuit capable of guiding a magnetic field induced by the first inductive element; and an encapsulation structure configured to encapsulate the active part and comprising a solid housing made of a first material having a first Young's modulus; the housing being filled with a filling resin having a second Young's modulus lower than the first Young's modulus; the ferromagnetic core being molded in said resin inside said housing so as to separate the ferromagnetic core from said housing.

[0008] According to a particular aspect of the invention, the first Young's modulus is between 10GPa and 20GPa.

[0009] According to a particular aspect of the invention, the second Young's modulus is between 1 MPa and 20 MPa.

[0010] According to a particular aspect of the invention, the first material is a solidified epoxy polymer.

[0011] According to a particular aspect of the invention, the filler resin is a polysiloxane or an acrylic.

[0012] According to a particular aspect of the invention, the housing comprises: a first notch made in a first face of the housing; a second notch made in a second face of the housing parallel to said first face; the first face and the second face being orthogonal to the foreground; the printed circuit having a first end slidably inserted into the first notch and having a second end slidably inserted into the second notch.

[0013] According to a particular aspect of the invention, the magnetic component further comprises a sealing layer made of an adhesive material deposited between: on the one hand the first end and on the other hand the periphery of the first notch; and between on the one hand the second end and on the other hand the periphery of the second notch;

[0014] The invention also relates to a method for manufacturing a magnetic component comprising the following steps: providing an active part comprising: o a printed circuit extending along a first plane; o a first inductive element produced by a first winding of an electrical conductor deposited on the printed circuit; the first winding defining a central zone of the printed circuit delimited by said first winding; the printed circuit comprising a first opening located in the central zone; o a ferromagnetic core forming a closed magnetic circuit and comprising a rod passing through the first opening; manufacturing a solid housing made of a first material having a first Young's modulus; the housing comprising: o a first notch produced in a first face of the housing; a second notch produced in a second face of the housing parallel to said first face;and a second opening on a third face of the package orthogonal to said first face; placing the active part in the package through the second opening by inserting the integrated circuit in a slide through the first and second notches; filling the solid package through the second opening with a filling resin having a second Young's modulus greater than the first Young's modulus so as to mold at least the ferromagnetic core.;

[0015] According to a particular aspect of the invention, the manufacturing method further comprises the following step: depositing a sealing layer made of an adhesive material between: o on the one hand the first end and on the other hand the periphery of the first notch; o and between on the one hand the second end and on the other hand the periphery of the second notch; so as to make the first face and the second face watertight.

[0016] Other features and advantages of the present invention will become more apparent upon reading the following description in relation to the following appended drawings.

[0017] Figure 1 illustrates a perspective view of the magnetic component according to the invention.

[0018] Figure 2a illustrates an exploded perspective view of a first example of the active part of the magnetic component according to the invention.

[0019] Figure 2b illustrates an exploded perspective view of a second example of the active part of the component according to the invention.

[0020] Figure 3 illustrates a perspective view of the rigid housing of the magnetic component according to the invention.

[0021] Figure 4a illustrates a perspective view of the magnetic component cut along the plane (X,Z) according to the invention.

[0022] Figure 4b illustrates a sectional view along the plane (X,Z) of the magnetic component according to the invention.

[0023] Figure 5 illustrates a sectional view along the plane (Y, Z) of the magnetic component according to the invention.

[0024] Figure 6 illustrates a top view of the magnetic component according to the invention.

[0025] Figure 7 illustrates a flowchart of the manufacturing process of the magnetic component according to the invention.

[0026] Figure 1 illustrates a perspective view of the assembled magnetic component D1 according to the invention. The assembled magnetic component D1 is placed in a orthogonal spatial reference frame (X,Y,Z) and the perspective view described in Figure 1 is taken from the side of the plane (X,Z).

[0027] The magnetic component D1 comprises an active part 1 encapsulated in an encapsulation structure 2. The active part 1 comprises a printed circuit 10, at least one inductive element 11 and a ferromagnetic core 12. The printed circuit 10 extends along a first plane P1 parallel to the plane (X,Y). At least one inductive element 11 is produced by a first winding 11 of an electrical conductor deposited on the printed circuit 10. The ferromagnetic core 12 is a body made of a ferromagnetic material forming a closed magnetic circuit. The ferromagnetic core 12 is placed relative to the first winding 11 so as to guide a magnetic field induced by the first inductive element 11.

[0028] The encapsulation structure 2 comprises a solid housing 21 made of a first material having a first Young's modulus. The housing 21 is filled with a filling resin 22 having a second Young's modulus lower than the first Young's modulus. The active part 1 is molded in the filling resin 22 inside the housing 22. The housing 22 comprises a first notch 21 a made in a first face 211 of the housing 22. The housing 22 further comprises a second notch 21 b made in a second face 212 of the housing parallel to said first face 211. The housing 22 has an opening 21 c on a third face 213 orthogonal to the two faces 211 and 212. The active part 1 is placed inside the housing 22, through the opening 21 c, by inserting the printed circuit 10 in a slide into the notches 21 a, 21 b. The printed circuit 10 thus extends along a plane P1 orthogonal to the first face 211, to the second face 212 and to the third face 213.

[0029] The ferromagnetic core 12 is molded in the filling resin 22 having a second Young's modulus lower than the first Young's modulus. The ferromagnetic core 12 is thus separated from the rigid housing 21 by the filling resin 22. This makes it possible to release the mechanical stress applied to the external surfaces of the ferromagnetic core 12 and thus absorb the mechanical deformations relating to the magnetostrictive effect. This results in a reduction in the magnetic resistance compared to the state-of-the-art solutions but also an increase in the equivalent inductance value of the active part 1. Other On the other hand, the rigid housing 22 provides mechanical and electrical protection of the active part from the external environment.

[0030] The first material forming the housing 22 has a first Young's modulus of between 10 GPa and 20 GPa. The filling resin 22 has a second Young's modulus of between 1 MPa and 20 MPa. Advantageously, the first Young's modulus is 500 to 1000 times higher than the second Young's modulus. As an indicative and non-limiting example, the housing 22 is made of a solidified epoxy polymer, preferably an epoxy polymer filled with silica beads to improve its rigidity. As an indicative and non-limiting example, the filling resin 22 is made of a polysiloxane or an acrylic. These materials are compatible with a space application: they have a reduced degassing rate and withstand several thermal characterization cycles according to the standards of the space field.

[0031] Thus, the use of the filling resin in the encapsulation structure allows on the one hand a magnetostriction necessary for the proper functioning of the magnetic component and on the other hand a good thermal interface with the package.

[0032] Furthermore, the first material forming the housing 22 has a first coefficient of thermal expansion and the filler resin 22 has a second coefficient of expansion greater than the first coefficient of thermal expansion. This makes it possible to avoid the occurrence of delamination at the interface between the filler resin 22 and the interior walls of the housing 22.

[0033] Figure 2a illustrates an exploded perspective view of a first example of the active part 1 of the magnetic component D1 according to the invention. The first inductive element 11 is produced by a first winding 11 of an electrical conductor deposited on the printed circuit 10. For example, the first winding 11 is produced by printed copper tracks. Advantageously, the printed circuit 11 is a multi-layer printed circuit making it possible to obtain a compact magnetic component D1 on several levels.

[0034] The first winding 11 defines a central area 101 of the printed circuit 10. The central area 101 is delimited by the inner tracks of the first winding 11. The printed circuit 10 comprises a first opening 102 located in the central area 101. The ferromagnetic core 12 is formed by two bodies 12a, 12b, made of ferrite for example, joined to each other using an adhesive layer. The junction of the two bodies 12a, 12b forms a ferromagnetic core 12 in the form of a closed magnetic circuit capable of guiding a magnetic field. The assembled ferromagnetic core 12 thus consists of a frame and a central rod 121. The central rod 121 results from the assembly of the rod 121a and the rod 121b. The central rod 121 is inserted into the first opening 102 located in the central zone 101. The frame of the ferromagnetic core 12 surrounds the first winding 11. Indeed, the printed circuit further comprises two lateral openings 102' and 102” placed on either side of the external tracks of the first winding 11. The two ferromagnetic bodies 12a and 12b are assembled so as to obtain a frame having two ribs inserted into said lateral openings 102' and 102”.This produces a closed magnetic circuit capable of guiding a magnetic field induced by the first inductive element (11).

[0035] Figure 2b illustrates an exploded perspective view of a second example of the active part 1 of the magnetic component D1 according to the invention. The characteristics and technical advantages described for the first example remain valid for the second example. The second example differs from the first example by the absence of lateral openings in the printed circuit 10. Indeed, the frame of the ferromagnetic core 12 surrounds the printed circuit 10. This is an alternative implementation to the implementation described in the first example.

[0036] Figure 3 illustrates a perspective view of the rigid housing 21 of the magnetic component D1 according to the invention. The housing 21 comprises a first notch 21a made in a first face 211 of the housing 22. The housing 22 further comprises a second notch 21b made in a second face 212 of the housing parallel to said first face 211. The housing 22 has an opening 21c on a third face 213 orthogonal to the two faces 211 and 212. The active part 1 is placed inside the housing 22, through the opening 21c, by inserting the printed circuit 10 in a slide into the notches 21a, 21b. The printed circuit 10 thus extends along a plane P1 orthogonal to the first face 211, to the second face 212 and to the third face 213. The thickness of the walls of the rigid housing 21 is greater than or equal to 1 mm to ensure its mechanical robustness.

[0037] In addition, the depth of each notch 21 a, 21 b along the Y axis is chosen so that: when the printed circuit 10 is fully inserted in a slide at through the two notches 21 a, 21 b, the ferromagnetic core 12 assembled with said printed circuit 10 is not in contact with any internal part of the housing 21.

[0038] Figure 4a illustrates a perspective view of the magnetic component D1 cut along the plane (X,Z) according to the invention. Figure 4b illustrates a sectional view along the plane (X,Z) of the magnetic component D1 according to the invention.

[0039] The central rod 121 of the ferromagnetic core 12 is inserted into the first opening 102 located in the central zone 102. The external surfaces of the ferromagnetic core 12 are in contact with the elastic filling resin 22 and not with the rigid housing 21. (with the exception of the interface with the periphery of the opening 102). This allows deformations by magnetostrictive effect and therefore an adaptation of the crystalline structure of the ferromagnetic core 12 according to the realignment of the magnetic domains in said ferromagnetic core 12. The printed circuit 10 has a first end 10a inserted in a slide in the first notch 21a and a second end 10b inserted in a slide in the second notch 21a. The width L1 of the printed circuit 10 is greater than the width L2 of the rigid housing 21. Thus, the two ends 10a, 10b protrude from the rigid housing 21 along the X axis through the notches 21a, 21b.At least one of the ends 10a, 10b comprises electrical contact points allowing the electrical integration of the magnetic component D1 into an external circuit and / or device. For example, the external circuit is a larger printed circuit comprising other analog or digital electronic components or optoelectronic components or power components.

[0040] The magnetic component D1 further comprises a sealing layer 3, 3' made of an adhesive material deposited between, on the one hand, the first end 10a and, on the other hand, the periphery of the first notch 21a; and between, on the one hand, the second end 10b and, on the other hand, the periphery of the second notch 21b.

[0041] Figure 5 illustrates a sectional view along the plane (Y, Z) of the magnetic component D1 according to the invention. According to this section, the frame of the ferromagnetic core 12 surrounding the printed circuit 10 is observed so as to form a closed magnetic circuit. The magnetic field induced by the first inductive element 11 is guided in a first loop formed by the central rod 121 and the left part of the frame along Y. In addition, the magnetic field induced by the first inductive element 11 is guided in a second loop formed by the central rod 121 and the straight part of the frame along Y. The opening 21 c is blocked by the filling resin 22.

[0042] Figure 6 illustrates a top view of the magnetic component D1 according to the invention. Each of the ends 10a, 10b of the printed circuit 10 protrudes from the housing 10 through the lateral notches 21a, 21b. Each of the ends 10a, 10b of the printed circuit 10 comprises a plurality of castellated vias V1. The castellated vias VA are semicircular connection vias at the edge of the printed circuit 10. The castellated vias V1 allow on the one hand the interconnection between the different layers of the printed circuit 10 and on the other hand facilitate the transfer of the magnetic component to an external device by allowing soldering.

[0043] Figure 7 illustrates a flowchart of the manufacturing process P1 of the magnetic component D1 according to the invention.

[0044] The first step E1 consists of providing an active part 1 comprising: o a printed circuit 10 extending along a first plane P1; o a first inductive element 11 produced by a first winding 11 of an electrical conductor deposited on the printed circuit 10. The first winding 11 defines a central zone 101 of the printed circuit 10 delimited by the first winding 11. The printed circuit 10 comprises a first opening 102 located in the central zone 101. o a ferromagnetic core 12 forming a closed magnetic circuit and comprising a rod 121 passing through the first opening 102.

[0045] The second step E2 consists of manufacturing a solid housing 21 made of a first material having a first Young's modulus. The housing 21 comprises a first notch 21a made in a first face 211 of the housing. The housing further comprises a second notch 21b made in a second face 212 of the housing parallel to said first face 211. The housing further comprises an opening 21c on a third face 213 of the housing 21 orthogonal to said first face 211.

[0046] To manufacture the case 21, it is possible to manufacture each face of said case separately from a resin. The faces of the case are produced as example in epoxy. The first and second faces 211, 212 are machined to produce the notches 21 a, 21 b. In order to produce the opening 21 c, the manufacture of the third face 213 is omitted (the absence of the third face 213 corresponds to the opening 21 c). Then, the different faces are assembled to each other so as to obtain the shape of the housing 21. Then, the assembled structure is solidified by thermal annealing to obtain the rigid housing 21.

[0047] Alternatively, it is possible to manufacture the case 21 using additive manufacturing techniques such as 3D printing.

[0048] The third step E3 consists of placing the active part 1 in the housing 21 through the second opening 21 c by inserting the integrated circuit 10 in a slide through the first and second notches 21 a, 21 b.

[0049] Optionally, the fourth step E4 consists of depositing a sealing layer 3 made of an adhesive material between, on the one hand, the first end 10a and, on the other hand, the periphery of the first notch 21a. Another adhesive layer 3' is deposited between, on the one hand, the second end 10b and, on the other hand, the periphery of the second notch 21b. This makes it possible to make the first face 211 and the second face 212 of the housing 21 watertight.

[0050] The last step E5 consists of filling the rigid housing 21 with a filling resin 22 through the second opening 21 c. The filling resin 22 has a second Young's modulus lower than the first Young's modulus. All of the elements of the active part 1 placed inside the rigid housing 21 are thus molded in the filling resin 22.

Claims

CLAIMS 1. Magnetic component (D1) comprising: - an active part (1) comprising: o a printed circuit (10) extending along a first plane (P1); o a first inductive element (11) produced by a first winding (11) of an electrical conductor deposited on the printed circuit (10); o a ferromagnetic core (12) positioned relative to said first inductive element (11) so as to form a closed magnetic circuit capable of guiding a magnetic field induced by the first inductive element (11); - and an encapsulation structure (2) configured to encapsulate the active part (1) and comprising a housing (21) made of a first material having a first Young's modulus; the housing (21) being filled with a filling resin (22) having a second Young's modulus lower than the first Young's modulus; the ferromagnetic core (12) being molded in said resin (22) inside said housing so as to separate the ferromagnetic core (12) from said housing (21).

2. Magnetic component (D1) according to claim 1 in which the first module Young's 20 is between 10GPa and 20GPa.

3. Magnetic component (D1) according to any one of claims 1 or 2 in which the second Young's modulus is between 1 MPa and 20 MPa.

4. Magnetic component (D1) according to any one of claims 1 to 3 in which the first material is a solidified epoxy polymer.

255. Magnetic component (D1) according to any one of claims 1 to 4 in which the filling resin (22) is a polysiloxane or an acrylic.

6. Magnetic component (D1) according to any one of claims 1 to 5 in which the housing (21) comprises: - a first notch (21 a) made in a first face (211) of the housing; 30 - a second notch (21 b) made in a second face (212) of the housing parallel to said first face (211); the first face (21 1 ) and the second face (212) being orthogonal to the first plane (P1 ); the printed circuit (10) having a first end (10a) inserted in a slide into the first notch (21 a) and having a second end (10b) inserted in a slide into the second notch (21 a).

57. Magnetic component (D1) according to claim 6 further comprising a sealing layer (3, 3') made of an adhesive material deposited between: - on the one hand the first end (10a) and on the other hand the perimeter of the first notch (21a); - and between on the one hand the second end (10b) and on the other hand the perimeter of the second notch (21 b); 8. Manufacturing method (P1) of a magnetic component (D1) comprising the following steps: - provide (E1) an active part (1) comprising: o a printed circuit (10) extending along a first plane (P1); 5 o a first inductive element (11) produced by a first winding (1 1 ) of an electrical conductor deposited on the printed circuit (10); the first winding (1 1 ) defining a central zone (101 ) of the printed circuit (10) delimited by said first winding (11 ); the printed circuit (10) comprising a first opening (102) located in the central zone (101 ); o a ferromagnetic core (12) forming a closed magnetic circuit and comprising a rod (121 ) passing through the first opening (102); - manufacturing (E2) a solid housing (21) made of a first material having a first Young's modulus; the housing (21) comprising: 5 o a first notch (21 a) made in a first face (21 1 ) of the housing; a second notch (21 b) made in a second face (212) of the housing parallel to said first face (21 1 ); and a second opening (21 c) on a third face (213) of the housing (21) orthogonal to said first face (21 1 ); 0 - placing (E3) the active part (1 ) in the housing (21 ) through the second opening (21 c) by inserting the integrated circuit (10) in a slide through the first and second notches (21 a, 21 b); - filling (E5) the solid housing (21) through the second opening (21 c) with a filling resin (22) having a second Young's modulus greater than the first Young's modulus so as to mold at least the ferromagnetic core (12).

59. Method of manufacturing (P1) a magnetic component (D1) according to claim 8 further comprising the following step: - depositing (E4) a sealing layer (3) made of an adhesive material between: o on the one hand the first end (1 Oa) and on the other hand the periphery of the first notch (21 a); 0 o and between on the one hand the second end (1 Ob) and on the other hand the periphery of the second notch (21 b); so as to make the first face (211, 212) and the second face watertight.

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