Encapsulated component and method for its production

Description

[0001] The present invention relates to an encased component. Furthermore, it relates to a method for producing the encased component. State of the art

[0002] In applications in power electronics and electrical machines where waste heat must be dissipated, thermally conductive encapsulants are often used to partially encapsulate electrically conductive elements. These encapsulants typically have a different coefficient of thermal expansion than the heated elements they encapsulate, which may be made of copper, for example. This can lead to detachment of the encapsulant from the electrically conductive elements or to cracks during thermal cycling, which significantly impairs heat dissipation.

[0003] WO 2014 / 034335 A1 discloses a coil component with high heat dissipation properties.

[0004] DE 10 2011 088043 A1 discloses a heat dissipation-optimized packaging for an electronic component.

[0005] DE 10 2008 030454 A1 discloses an actuating device with a housing and a coil body with coil winding arranged therein.

[0006] DE 10 2013 214646 A1 discloses a housing formed from a resin material and a first flange portion of a coil body forming a melting projection bonded and fused to the housing. Disclosure of the invention

[0007] The encased component comprises a thermally conductive element and a thermally conductive enveloping compound that fills an interior area of ​​the element. An interior area is defined as an area that is at least partially enclosed by the element. However, it is not necessary for the element to completely enclose the interior area.

[0008] The encapsulating compound preferably contains at least 25 volume percent ceramic particles based on 100 volume percent of the encapsulating compound to ensure good thermal conductivity of the encapsulating compound. The ceramic particles are particularly selected from the group consisting of aluminum nitride, boron nitride, aluminum oxide, silicon nitride, and mixtures thereof. The matrix material of the encapsulating compound, in which the particles are embedded, can be freely selected. For example, it can be a cement matrix or a polymer matrix.

[0009] The element has several openings that connect its interior with an exterior of the element. The encapsulating compound fills the openings. Because the encapsulating compound flows through the structure of the element and encloses it on all sides or at least penetrates the openings, contact between the encapsulating compound and the element is maintained even during thermal cycling. Heat can then be transferred from a heat source via the encapsulating compound to the element for heat dissipation. The element is a coil pot, as used in power electronics. The encapsulated component can be particularly well manufactured on the basis of a coil pot, since a large number of openings can easily be introduced into this without impairing its function. The coil pot can also be understood as a coil cup. In the context of the present invention, the term coil pot refers to a pot-shaped coil orThe term coil cup refers to a cup-shaped coil.

[0010] The heat source is preferably at least partially, and particularly preferably completely, surrounded by the element. Furthermore, the heat source is preferably completely surrounded by the encapsulating compound. For example, the heat source can be a wound magnetic core. This can be arranged, in particular, in a component in the form of a coil pot, wherein the coil pot is filled with the encapsulating compound for heat exchange with the magnetic core.

[0011] In an embodiment of the component not forming part of the invention, the element is designed as a wire mesh. This automatically provides a plurality of openings, the size of which can be adjusted by the density of the wire mesh.

[0012] The openings are designed as holes in a sheet metal. This sheet metal can, for example, form the outer surface of a cylindrical coil pot. Designing the openings as holes in a sheet metal has the advantage that the openings can be designed with a wide variety of geometries as required.

[0013] In one embodiment of the encased component, the encapsulating compound is still arranged in the outer region. The encapsulating compound in the inner region and the encapsulating compound in the outer region are then connected to each other by the encapsulating compound in the openings. This presses the encapsulating compound against the element from both sides, preventing the formation of gaps and cracks. This embodiment of the encapsulated component can be manufactured independently of the shape of the openings simply by arranging the encapsulating compound accordingly.

[0014] The openings are designed as holes in a sheet metal and each have a countersink at the end facing the exterior. This anchors the encapsulating compound in the element so that it cannot detach from it, even if it is only located in the openings and in the interior of the element, but not in the exterior.

[0015] In the process for producing the encased component, a thermally conductive element with multiple openings is first provided. At least one heat source is arranged in this element. The component is then filled with the encapsulating compound in liquid form so that it can penetrate the openings. Once the encapsulating compound has hardened, the encapsulated component is obtained. Hardening can occur using different processes depending on the composition of the encapsulating compound. If a cement compound is used as the encapsulating compound, it can harden, for example, through hydraulic setting. If, on the other hand, the encapsulating compound is a polymer compound, it can harden, for example, through heat-induced or photo-induced cross-linking.

[0016] If an encased component is to be produced in which the encapsulating compound is arranged not only in the interior and openings, but also in the exterior of the element, this can be achieved in one embodiment of the method by arranging the element in a mold and subsequently filling the mold with the encapsulating compound such that it covers the exterior of the element with a predeterminable thickness. This thickness, by which the encapsulating compound protrudes beyond the element, can be specified depending on various parameters, such as, in particular, the thermal expansion coefficient of the encapsulating compound and the element, the strength and elasticity of the encapsulating compound, and the thickness of the element to be encased.

[0017] If, however, the method is to be used to produce an encased component in which the openings each have a countersink at their end facing the outside area, one embodiment of the method provides for the openings in the outside area to first be covered by a cover. This cover can in particular be an adhesive tape. The liquid encapsulating compound is then poured into the interior of the element so that it can flow into the openings but cannot flow out of them due to the cover. Once the encapsulating compound has hardened in the interior area and in the openings, the cover can then be removed again. Short description of the drawings

[0018] Embodiments of the invention are illustrated in drawings and are explained in more detail in the following description. Figure 1shows a cross-sectional view of a thermally conductive element with an enveloping compound according to the prior art. Figure 2 shows a coil pot which, in one embodiment of the method according to the invention, can be coated with an enveloping compound in order to obtain a component coated according to the invention. Figure 3 shows in a cross-sectional view the production of an encased component in one embodiment. Figure 4 shows in a cross-sectional view the production of an encased component in an embodiment of the method according to the invention. Figure 5 shows an isometric view of an embodiment of an encased component. Embodiment of the invention

[0019] In Figure 1A conventional component 10 for power electronics is produced, which has a thermally conductive element 20 in the form of a coil pot. The interior of the element 20 is filled with an encapsulating compound 30, which in this case is a cement compound based on alumina cement containing 50 percent by volume of aluminum oxide particles. It can be seen that a gap 40 has formed between the encapsulating compound 30 and the element 20 due to thermal cycling. Reliable heat transfer between a wound magnetic core as a heat source 50 via the encapsulating compound 30 to the element 20 is therefore no longer guaranteed.

[0020] Figure 2shows a thermally conductive element 20 in the form of a coil pot, which is suitable for producing an encased component 10 according to an embodiment of the invention. It has the shape of a circular cylinder open at one end. Its outer surface is formed by a copper sheet in which openings 21 in the form of essentially circular-cylindrical bores are formed.

[0021] Figure 3 shows how an embodiment of a method not belonging to the invention can be used to produce a coated component 10 from this coil pot according to an embodiment not belonging to the invention. After the Figure 3After the coil pot has been fixed by a heat source 50 (not shown), the coil pot is placed in a silicone mold 60 such that its outer surface has a uniform distance d from the inner wall of the mold 60. Spacers (not shown) ensure that the distance between the bottom of the coil pot and the bottom of the mold 60 also corresponds to the distance d. Subsequently, a liquid cement mass, which corresponds to the cement mass according to Figure 1corresponds, is poured into the coil pot. It flows out of its interior through the openings 21 and thus also fills the entire outer area between the coil pot and the mold 60. After the cement mass has hardened, it forms an enveloping mass 30 that fills the interior of the element 20 and thermally connects the heat source 50 to the coil pot. It surrounds the coil pot with an outer layer of thickness d, which is connected to the enveloping mass 30 inside the coil pot through the openings 21. As a result, the enveloping mass 30 is anchored to the coil pot both inside and out in such a way that detachment or cracking during thermal cycling is excluded.

[0022] Figure 4shows the production of an encased component 10 according to an embodiment of the invention in an embodiment of the method according to the invention. For this purpose, a thermally conductive element 20 in the form of a coil pot is used, the openings 21 of which differ from the openings 21 of the coil pot according to Figure 2While the openings 21 in the first embodiment are essentially circular-cylindrical bores, the openings in the second embodiment also have a circular-cylindrical part at their end facing the interior of the element 20, which, however, merges into a depression 22 at the end facing the exterior. This means that the cross-section of each opening 21 increases from the inside to the outside in the area of ​​the depression 22. All openings 21 are closed from the outside by means of a cover 70 in the form of adhesive tape. As in the first embodiment, the liquid cement mass is poured into the interior of the element 20. It also flows into the openings 21, but cannot flow out of them due to the cover 70. After the hydraulic setting and thus hardening of the cement mass, it forms an enveloping mass 30 in the interior and in the openings 21 of the element 20.The cover 70 can now be removed. In this embodiment, the formation of gaps and cracks due to thermal cycling is also excluded, since the encapsulating compound 30 is anchored in the openings 21 in the region of the depressions 22 in the element 20.

[0023] An embodiment of an encased component 10 not belonging to the invention is shown in Figure 5 . In this example, the element 20 is designed as a coil pot in the form of a wire mesh, which in this case consists of copper wire. The meshes of the wire mesh form openings 21 in the element 20. A coil core as a heat source 50 is arranged in the element 20, and this is encapsulated internally and externally with an encapsulating compound 30 that extends through the openings 21. This exemplary embodiment of the encapsulated component 10 can be manufactured in a mold in a manner analogous to the manufacturing method in the first exemplary embodiment.

Claims

1. Encapsulated component (10), having a thermally conductive element (20) and a thermally conductive encapsulation compound (30) which fills an interior region of the element (20), wherein the element (20) has multiple openings (21) which connect the interior region to an exterior region of the element (20), wherein the encapsulation compound (30) fills the openings (21), wherein the element (20) is a coil pot, characterized in that the openings (21) are formed as bores in a metal sheet and each have a countersink (22) at their end facing towards the exterior region.

2. Encapsulated component (10) according to Claim 1, characterized in that the encapsulation compound (30) is furthermore arranged in the exterior region.

3. Encapsulated component (10) according to either of Claims 1 and 2, characterized in that it has a heat source (50) which is completely surrounded by the encapsulation compound (30).

4. Method for producing an encapsulated component (10) according to Claim 3, wherein at least one heat source (50) is arranged in an interior region of a thermally conductive element (20) which has multiple openings (21), and the element (20) is then filled with an encapsulation compound (30) such that this ingresses into the openings (21).

5. Method according to Claim 4, characterized in that the element (20) is arranged in a mould (60), and the mould (60) is subsequently filled with the encapsulation compound (30) such that this covers the exterior region of the element (20) with a predefinable thickness (d).

6. Method according to Claim 4, characterized in that the openings (21) are covered in the exterior region by means of a cover (70), which is removed again after curing of the encapsulation compound (30) in the interior region and in the openings (21).