Electrical device

Abstract

Electrical appliance, which has a circuit board (12) which is equipped with heat-generating components, wherein the circuit board (12) is arranged in a housing of the device, wherein a plastic body at least partially encloses the printed circuit board (12) and is connected to the populated printed circuit board (12), in particular by material bonding and / or form-fitting, characterized by the fact that the plastic body is composed of at least two parts that are positively connected to each other, wherein a power module (5) is arranged on the circuit board (12) which is connected to a cooling plate (1), wherein the cooling plate (1) is arranged outside the plastic body, wherein the power module (5) protrudes through a recess in the plastic body.

Description

[0001] The invention relates to an electrical device.

[0002] It is known that inverters, as electrical devices, contain signal electronics and power electronics. The power electronics supply power to a load, such as an electric motor. The heat, particularly from the power semiconductor switches of the power electronics, is dissipated to a heat sink and from there to the ambient air or another surrounding cooling medium.

[0003] To improve heat transfer, it is known to introduce thermal paste into the heat transfer area.

[0004] From DE 31 47 033 C1, a protective housing for vibration-proof embedding of a device is known as the closest prior art.

[0005] From DE 10 2010 050 120 A1 a method for producing a plastically deformable plastic body is known.

[0006] From JP H09 - 18 176 A, a housing with a built-in substrate and a printed circuit board is known.

[0007] An electrically isolated module is known from EP 1 422 984 A2.

[0008] A support structure is known from US 4 864 469 A.

[0009] From DE 10 2008 034 538 A1 a digital multimeter with a hinged cover arrangement is known.

[0010] US Patent 5 755 026 A discloses a method for preventing condensation on the surface of the housing of an electrical appliance.

[0011] From DE 10 2005 037 488 B4 a cooling arrangement and its use as well as a compact drive are known.

[0012] The invention is therefore based on the objective of further developing an electrical device, whereby the manufacturing process should be simple and environmental protection should be improved.

[0013] According to the invention, the problem is solved in the device according to the features specified in claim 1 or 2.

[0014] Important features of the invention in the electrical device are that it has a circuit board which is equipped with heat-generating components, the circuit board is arranged in a housing of the device, wherein a plastic body at least partially encloses the circuit board and is connected to the populated circuit board, in particular by material bonding and / or form-fitting.

[0015] A key advantage is that the circuit board and its components are protected from mechanical impacts such as shocks, vibrations, and the like. In particular, protruding components are better stabilized against vibrations by the plastic housing. This ensures safe transport and storage, as the circuit board is not integrated into the device's housing. A thermally conductive plastic housing also allows for improved heat dissipation from heat-generating components.

[0016] Furthermore, environmental protection is improved because only the cassette needs to be replaced if the electronics are defective. The pot-shaped housing is reusable and can remain installed in the system while the cassette is being replaced. This also reduces repair costs.

[0017] Key features of the electrical device are that it has a circuit board equipped with heat-generating components, the circuit board is arranged in a housing of the device, wherein a plastic body is arranged on both sides of the circuit board and is connected to the populated circuit board, in particular by material bonding and / or form-fitting.

[0018] An advantage is that the plastic body surrounds the circuit board, thus ensuring good mechanical protection.

[0019] In an advantageous embodiment, the plastic body is composed of at least two interlocking sub-bodies, in particular wherein the interlocking connection is a snap-fit. It is advantageous that the sub-bodies can be prefabricated and thus arranged around the printed circuit board and connected to each other. Therefore, the printed circuit board does not need to be stressed when arranging the sub-bodies around it.

[0020] In an advantageous embodiment, the plastic body is formed in one piece, particularly by overmolding or as a plastic casting. The advantage here is that particularly cost-effective manufacturing is possible, since the circuit board only needs to be placed in a mold and can then be overmolded or cast.

[0021] In an advantageous embodiment, the populated circuit board has a coating on its surface, in particular a water vapor-repellent coating and / or a water-repellent coating. It is advantageous that the circuit board can be surrounded by polystyrene beads in a mold and water vapor can be added, so that a polystyrene encapsulation can be produced using a simple manufacturing method. Polystyrene is understood to mean any other foamed plastic, in particular one that is thermally conductive and electrically insulating and preferably contains a flame retardant additive.

[0022] In a preferred embodiment, the plastic is made of polystyrene or foam, in particular polyurethane foam. The advantage here is that a cost-effective material can be used, which can be enhanced with improved thermal conductivity through the addition of chemical components.

[0023] In an advantageous embodiment, the plastic exhibits better thermal conductivity, in particular specific thermal conductivity, than air. In particular, the plastic body is made of an electrically insulating material. An advantage of this design is that the thermal conductivity can be improved through appropriate additives. Furthermore, this eliminates the need for air as a heat transfer medium and allows the plastic body to be placed directly between the circuit board and the cooling plate.

[0024] In an advantageous embodiment, the electrical device is a converter, in particular wherein the signal electronics and the power electronics of the converter are arranged on the printed circuit board. An advantage of this is that only one printed circuit board needs to be populated, thus enabling highly automated manufacturing, since the assembly can be carried out by pick-and-place machines. Furthermore, connecting the electronic circuit, i.e., comprising the printed circuit board with the attached cooling plate, to the housing is particularly simple and easy to perform, since it only requires inserting the electronic circuit into the cup-shaped housing.

[0025] In an advantageous embodiment, a power module is arranged on the circuit board, which is connected to a cooling plate, in particular a cooling plate containing aluminium. The power module is screwed onto this cooling plate and thermally connected to it for heat dissipation. An advantage of this design is that the cooling plate can be connected to the circuit board via the power module during assembly. This means that the plastic housing protects one side of the circuit board—the side facing away from the cooling plate—while the other side is protected not only by the remaining part of the plastic housing but also by the cooling plate.

[0026] In an advantageous embodiment, the cooling plate is arranged outside the plastic body, in particular wherein the power module projects through a recess in the plastic body. An advantage of this is that the heat dissipation through the otherwise protective plastic body is not impaired.

[0027] In an advantageous embodiment, the plastic body has recesses for components mounted on the circuit board, particularly for large components. It is advantageous that heat dissipation to the cooling plate can be achieved in these areas via air or – as in the case of the power module – through a contact surface on the cooling plate.

[0028] In an advantageous embodiment, the plastic body, particularly the second subbody, has a further recess that provides an air connection between a heat-generating component mounted on the circuit board and a surface area of ​​the cooling plate, particularly for the convective dissipation of heat to the cooling plate via this air connection. It is advantageous that the recess in the plastic body, associated with the respective heat-generating component or the corresponding surface area of ​​the circuit board, creates an air space that is at least partially bounded by a surface area of ​​the cooling plate and by the respective heat-generating component or its corresponding surface area of ​​the circuit board. Thus, convectively driven airflow is generated by temperature differences, enabling heat dissipation to the cooling plate.

[0029] In an advantageous embodiment, a first side of the circuit board, or at least a partial area of ​​this side, is covered, in particular completely, by the plastic body, in particular by its first partial body, and The other side of the circuit board is at least partially covered by the plastic body, specifically by its second sub-body, which is ring-shaped. This offers the advantage that the covered components mounted on the circuit board are protected from environmental influences, such as mechanical impact. The plastic body thus performs a housing-forming function—to the extent of its coverage. It is also more elastic than an aluminum housing. Only after installation in the cup-shaped housing part and closing it with the lid is a complete housing created. In this installed state, the plastic body also assumes a heat-dissipating function, or rather, creates air spaces for the targeted cooling of heat-generating components, provided its thermal conductivity is lower than that of air.

[0030] In an advantageous embodiment, the housing of the device has a pot-shaped housing part which is closed by a lid part. In particular, a contact surface for heat transfer from the cooling plate to the housing is arranged on the inner wall of the cup-shaped housing section. An advantage of this design is that the heat transferred from the cooling plate to the housing can be spread across the entire cup-shaped housing section. This distributes the heat over a large surface area. However, it is essential to ensure optimal thermal contact between the contact surface and the cooling plate. Since the cooling plate itself can be large and flat, comparable in size to the entire circuit board, sufficient heat transfer is easily achieved, even without thermal paste in the contact area. The integration of the cassette, consisting of the cooling plate, plastic body, and circuit board, into the cup-shaped housing also allows for the simple production of various versions. This is because the same cassette can be installed in different housing sections.This allows application-specific or market-specific requirements to be addressed through appropriately modified housing components. The cover components can be varied accordingly. A high degree of variance can be achieved with a small number of components.

[0031] In a preferred embodiment, cable glands are arranged between the lid and the housing, particularly for supply lines, lines feeding a consumer, and data bus lines. It is advantageous that the pot-shaped housing can be designed with a base that is as low as possible, i.e., with high side walls.

[0032] Important features of the method for manufacturing an electrical device are that the device has a printed circuit board equipped with at least one power module and other components, in particular wherein the components and the power module are thus attached to the printed circuit board, where (i) in a process step the printed circuit board is at least partially enclosed with a plastic body, in particular - is at least partially overmolded with plastic to form the plastic body - or is inserted between at least two sub-bodies of the plastic body, which is formed in at least two parts, wherein the sub-bodies are connected to each other after insertion, in particular by means of a positive locking mechanism and / or by means of a snap-fit ​​connection, (ii) in a subsequent process step a cooling plate is connected to the power module, in particular by means of screws, (iii) in a further subsequent process step, the printed circuit board together with the cooling plate and plastic body is inserted into a pot-shaped housing part and the cooling plate is pressed against a contact surface of the inner wall of the housing part, in particular by thermal conductivity.

[0033] A key advantage is that the circuit board is encased in a protective plastic housing, thus safeguarding it during transport and storage. Once the cooling plate is attached, this protection is further enhanced, and the electronic circuit, particularly the cassette, can be transported as a single unit. For final assembly, the cassette simply needs to be inserted into the cup-shaped housing and its cooling plate brought into contact with the housing for heat dissipation. The housing is made of metal, such as aluminum, to ensure efficient heat dissipation and high mechanical stability.

[0034] Further advantages arise from the dependent claims. The invention is not limited to the combination of features of the claims. For those skilled in the art, further meaningful combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent, in particular from the problem statement and / or the problem arising from a comparison with the prior art.

[0035] The invention will now be explained in more detail with reference to schematic illustrations: In the Fig. Figure 1 shows a schematic sketch of a converter according to the invention with a first and a second foam part. In the Fig. Figure 2 shows the contour of the recess in the second foam part 4.

[0036] The inverter housing comprises a pot-shaped, one-piece housing part 9, preferably made of aluminum, which is closed by means of a cover part 8. Cable glands are provided in the intermediate area between the cover part 8 and the pot-shaped housing part 9, allowing supply cables to be inserted into the interior and connection cables to the electric motor powered by the inverter (i.e., the load) to be routed out. Data bus cables are also routed into the interior through a cable gland located there.

[0037] The electric motor is preferably a three-phase motor. The supply cables preferably carry single-phase or three-phase AC mains voltage.

[0038] Inside the inverter, a cassette is inserted which includes the inverter's circuit board 12 and a cooling plate 1.

[0039] The entire electronic circuitry of the inverter, including signal electronics and power electronics, is arranged on the circuit board. The power electronics include at least... - a rectifier which rectifies the alternating voltage supplied via the supply cables, - an intermediate circuit capacitor for smoothing the rectified voltage and - a power module which has power semiconductor switches arranged in half-bridges, from which the lines supplying the motor are fed.

[0040] The signal electronics generate pulse-width modulated control signals for the power semiconductor switches and are connected to the data bus.

[0041] The circuit board 12 is therefore equipped with at least one large component 3, such as the intermediate circuit capacitor and power module 5. Furthermore, the circuit board 12 is also equipped with small components 11, such as SMD components.

[0042] The power module 5 is screwed to a cooling plate 1 by means of a connecting screw having a screw head 7, so that the heat from the power module can be dissipated at the contact surface with the cooling plate 1. The power module 5 has a ceramic-coated or copper-plated contact surface. The cooling plate 12 is preferably made of aluminum. This ensures good thermal conductivity and effective heat dissipation.

[0043] The cooling plate has a surface area of ​​more than 50%, and in particular more than 80% or 90%, of the printed circuit board area. Even improved heat dissipation can be achieved if the surface area of ​​cooling plate 1 exceeds the surface area of ​​the printed circuit board.

[0044] Thus, a spread of the heat generated by the power module is achieved.

[0045] When the cassette is inserted into the cup-shaped housing part 9, the cooling plate is pressed against the inner wall of the cup-shaped housing part, particularly increasingly so when the corresponding connecting screws are tightened, which connect the cassette to the cup-shaped housing part 9. Thus, the heat from the cooling plate 1 is then transferred to the cup-shaped housing part 9 and thereby dissipated.

[0046] It is important that the pot-shaped housing part encloses the cassette, except for the lid area. Thus, the circuit board sits on both sides within this housing part 9, which maintains approximately the same temperature. The signal electronics and power electronics are therefore at the same temperature level.

[0047] The circuit board 12 is surrounded on both sides by foam parts, i.e., wrapped. A cooling plate 1 is arranged on only one side, so that only the circuit board 12, but not the cooling plate 1, is wrapped on both sides.

[0048] The first foam part 10 is arranged on the first side of the circuit board. The second foam part 4 is arranged on the other side, i.e., between cooling plate 1 and circuit board 12.

[0049] The two foam parts 4 and 10 can be connected by means of a locking mechanism. Thus, they essentially clamp around the circuit board 12.

[0050] The second foam section 4 has recesses for the large components 3 and the power module 5. Since the remaining webs must have a minimum wall thickness for stability reasons, instead of individual, spaced-apart recesses in the foam section 4, a single large recess 20 is formed when the large components 3 and the power module 5 are closely spaced, as shown in Fig. 2 shown. Thus, the air arranged in the spaces between the large components and within the second foam part 4 conducts heat convectively from hot to cold surface areas, in particular towards the cooling plate 1.

[0051] The second foam part 4 is according to Fig. 2 is pronounced as a ring-shaped structure.

[0052] The locking mechanism 2 or 6 of the foam parts 4 and 10 is achieved through their shaping, and therefore requires no additional parts. A locking lug is formed on one of the foam parts 4 or 10, and a corresponding recess with a locking projection is formed on the other. A positive-locking connection is created by engaging behind the projection, i.e., by locking the parts together.

[0053] Foam components 4 and 10 protect the circuit board against mechanical impacts such as shocks and / or vibrations. Therefore, the circuit board 12 can be safely stored and transported in this packaging formed by foam components 4 and 10.

[0054] Furthermore, depending on the application or customer requirements, differently shaped, pot-shaped housing parts 9 can be connected to the cassette. Similarly, differently shaped cover parts 8 can be connected. In this way, inverters with different external appearances and correspondingly different functionalities can be manufactured without having to redesign the circuit board each time. The only important factor is that the interface to the cassette is compatible; in particular, the interface for connecting the cooling plate 1 to the inner wall of the pot-shaped housing part 9 must be compatible.

[0055] The locking mechanism 2 and 6 is preferably designed to be releasable.

[0056] In a further embodiment of the invention, the spacing between the large components 3 and between the components and the power module 5 is greater than in Fig. 1 and Fig. 2. Thus, the second foam part has several recesses, each of which is significantly smaller than those in the first. Fig. The recess shown in Figure 2 illustrates this. However, the recesses are dimensioned and arranged in such a way that hot heat sources are cooled towards the cooling plate 1 by the convective air currents that form in the respective recesses. This design of the recesses as convectively driven air zones is particularly advantageous when the thermal conductivity of the foam material is lower than that of air.

[0057] In the present invention, "air" means the ambient air of the inverter and / or air with a temperature of 20 °C at 1 bar pressure and a humidity of 30%.

[0058] If the thermal conductivity of the foam component material exceeds that of air, the recesses for convectively operated air zones are omitted wherever possible. In such cases, recesses are only provided for the large components 3 and the power module 5.

[0059] Polyurethane or polystyrene foam can be used as the foam material.

[0060] In a further embodiment of the invention, the populated circuit board 12 is not mechanically connected to two foam parts, but rather a foam part is produced by overmolding or during the production of polystyrene. Here, the populated circuit board is coated with a water-impermeable or water vapor-impermeable lacquer, for example, as a hot-dip lacquer. In a further manufacturing step, the coated circuit board 12 is then placed in a mold, and the remaining interior of the mold is filled with polystyrene beads. By additionally introducing hot steam, the polystyrene beads are positively bonded to one another, so that the foam parts 4 and 10 are formed in one piece and contain no additional recesses for air or the like. The thermal conductivity of the resulting polystyrene is improved by chemical additives to such an extent that it is better than that of air.Instead of polystyrene, another electrically insulating material suitable for overmolding, but with a better thermal conductivity than air, can also be used. Depending on the manufacturing process, coating with water vapor- or water-repellent paint may then be unnecessary.

[0061] Preferably, thermal paste is omitted in the contact area between the cooling plate and the housing part. The surface area is sufficiently large to allow for effective heat dissipation. Reference symbol list 1 cooling plate 2. Locking mechanism 3 large component, especially capacitor 4 second foam part 5 power modules, featuring power semiconductor switches 6. Locking mechanism 7 Screw head of a connecting screw for attaching the power module to the cooling plate 1 8 lid part 9 pot-shaped housing part 10 first foam part 11 SMD components or small electronic components 12 circuit boards

Claims

[1] Electrical device, which has a printed circuit board (12) which is equipped with heat-generating components, wherein the circuit board (12) is arranged in a housing of the device, wherein a plastic body at least partially encloses the circuit board (12) and is connected to the populated circuit board (12), in particular in a material-locking and / or form-locking manner, characterized by , that the plastic body is composed of at least two partial bodies that are connected to one another in a form-fitting manner, wherein a power module (5) is arranged on the circuit board (12) and is connected to a cooling plate (1), wherein the cooling plate (1) is arranged outside the plastic body, wherein the power module (5) protrudes through a recess in the plastic body. [2] Electrical device, which has a printed circuit board (12) which is equipped with heat-generating components, wherein the circuit board (12) is arranged in a housing of the device, wherein a plastic body is arranged on both sides of the printed circuit board (12) and is connected to the populated printed circuit board (12), in particular in a materially bonded and / or form-fitting manner, characterized by , that wherein the plastic body is composed of at least two partial bodies connected to one another in a form-fitting manner, wherein a power module (5) is arranged on the circuit board (12) and is connected to a cooling plate (1), wherein the cooling plate (1) is arranged outside the plastic body, wherein the power module (5) protrudes through a recess in the plastic body. [3] Device according to claim 2, characterized by that the positive connection is a locking mechanism (2). [4] Device according to one of the preceding claims, characterized by that the populated printed circuit board (12) has a varnish on its surface, in particular a water vapor-repellent varnish and / or a water-repellent varnish. [5] Device according to one of the preceding claims, characterized by that the plastic is made of polystyrene or foam, in particular polyurethane foam. [6] Device according to one of the preceding claims, characterized by , that the plastic has better thermal conductivity, especially specific thermal conductivity, than air, in particular wherein the plastic body is made of electrically insulating material. [7] Device according to one of the preceding claims, characterized by that the electrical device is a converter, in particular wherein the signal electronics and the power electronics of the converter are arranged on the circuit board (12). [8] Device according to one of the preceding claims, characterized by that the power module (5) is screwed onto this cooling plate (1) and is connected to it in a heat-conducting manner for the dissipation of heat. [9] Device according to one of the preceding claims, characterized by that the cooling plate (1) contains aluminum. [10] Device according to one of the preceding claims, characterized by that the plastic body has recesses for components mounted on the circuit board (12), in particular for large components. [11] Device according to claim 10, characterized by , that the plastic body, in particular the second partial body, has a further recess which is an air connection between a heat-generating component mounted on the circuit board (12) and a surface partial region of the cooling plate (1), in particular for the convective dissipation of heat by means of the air connection to the cooling plate (1). for components mounted on the circuit board (12), in particular for large components. [12] Device according to one of the preceding claims, characterized by , that a first side of the printed circuit board (12) or at least a partial area of ​​this side is covered, in particular completely covered, by the plastic body, in particular by its first partial body, and the other side of the circuit board (12) is at least partially covered by the plastic body, in particular by its second partial body, in particular wherein the second partial body is annular. [13] Device according to one of the preceding claims, characterized by , that the housing of the device has a pot-shaped housing part which is closed by a cover part (8), in particular wherein a contact surface for heat introduction from the cooling plate (1) to the housing is arranged on the inner wall of the pot-shaped housing part. [14] Device according to one of the preceding claims, characterized by that cable bushings are arranged between the cover part (8) and the housing part, in particular for supply lines, lines feeding a consumer and data bus lines. A [15] Method for producing an electrical device, in particular according to one of the preceding claims, wherein the device comprises a printed circuit board (12) equipped with at least one power module (5) and further components, in particular wherein the components and the power module (5) are thus fastened to the printed circuit board (12), wherein the electrical device is a converter, wherein the signal electronics and the power electronics of the converter are arranged on the circuit board (12). characterized by , that (i) in a method step, the printed circuit board (12) is at least partially enclosed with a plastic body, in particular - is at least partially overmolded with plastic to form the plastic body - or is inserted between at least two partial bodies of the at least two-piece plastic body, wherein the partial bodies are connected to one another after insertion, in particular in a form-fitting manner and / or by means of a locking mechanism (2), (ii) in a subsequent process step, a cooling plate (1) is connected to the power module (5), in particular screwed, (iii) in a further subsequent method step, the printed circuit board (12) together with the cooling plate (1) and the plastic body is inserted into a pot-shaped housing part and the cooling plate (1) is pressed onto a contact surface of the inner wall of the housing part, in particular is connected in a heat-conducting manner.

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