Fastening system for printed circuit boards for dissipating heat losses

Abstract

The invention relates to a fastening system of a housing and an associated heat sink, having a first printed circuit board and a second printed circuit board which are arranged one above the other, and wherein the first printed circuit board is fixed to at least one contact element in a cavity enclosed by the housing, and the contact element electrically interconnects at least the first printed circuit board and the second printed circuit board, and the heat sink are frictionally interconnected via a housing shoulder, and a heat-conducting element is arranged between the second printed circuit board and the heat sink, said fastening system being characterized according to the invention in that an elastic connection which seals off the housing is arranged between the second printed circuit board and the housing shoulder.

Description

[0001] Mounting system for printed circuit boards to dissipate waste heat

[0002] The invention relates to a fastening system comprising a housing and an associated heat sink, with a first printed circuit board and a second printed circuit board arranged one above the other, wherein the first printed circuit board is fixed in a cavity enclosed by the housing on at least one contact element, and the contact element electrically connects at least the first printed circuit board and the second printed circuit board to each other, and the heat sinks are connected to each other by means of a force-fit connection via a housing shoulder, and a thermal conducting element is arranged between the second printed circuit board and the heat sink.

[0003] Due to increasing demands on the functionality of control and charging units in the automotive industry, devices with multiple circuit boards are being designed more and more frequently. From a mechanical design perspective, this results in increasingly conflicting requirements.

[0004] Firstly, the electronics must be well cooled, so only narrow and rigid gaps / openings are suitable for a thermal exchange layer.

[0005] Secondly, the printed circuit boards must not be mechanically bent under any circumstances, either during installation or operation, so that reliability problems due to broken or defective electrical components or their connections must be avoided at all costs. Numerous solutions for the flexible mounting of printed circuit boards to compensate for possible relative movement are already known from the prior art.

[0006] DE 10 2019 216 929 A1 describes, for example, an arrangement for temperature control of components, in particular semiconductor components, in which a heat sink and a base plate are flexibly connected to each other by means of an elastic connection. In this embodiment, the elastic connection allows for compensation of slight relative movement between the base plate and the heat sink.

[0007] DE 102005 043 880 B4 also discloses a possibility of advantageously fixing, in particular, superimposed printed circuit boards to an electronics housing by means of a spring-loaded fastening device.

[0008] A particular disadvantage of the solutions presented in the prior art is that they are limited to addressing only one problem within a single fastening arrangement. As a result, other disturbances and disadvantages often remain unconsidered and thus unaddressed.

[0009] Based on this, the present invention aims to create a fastening system for stacked printed circuit boards (PCBs) that are electrically and flexibly connected to one another, thus enabling stress-free mounting of multiple stacked PCBs. Furthermore, the invention seeks to create mechanical decoupling of the PCBs, particularly in the presence of a cooling channel, and finally, to provide a seal through the elastic connection according to the invention to protect against external influences such as particles and moisture. These objectives are achieved according to the invention by providing an elastic connection between the second PCB and the housing shoulder, which seals the housing accordingly.

[0010] The above and further objectives, properties and other advantages of the invention are explained in more detail below in conjunction with the accompanying drawings.

[0011] They show:

[0012] Fig. 1 : an arrangement according to the invention in a first

[0013] embodiment without a heat sink

[0014] Fig. 2: an arrangement according to the invention in a first

[0015] embodiment with a heat sink

[0016] Fig. 3: an arrangement according to the invention in a second

[0017] embodiment with a heat sink and a cooling channel.

[0018] Fig. 1 shows the fastening system according to the invention. This fastening system for superimposed printed circuit boards 3, 4 in a housing 2 is characterized in that the first printed circuit board 3 is flexibly attached to a contact element 10 and the second printed circuit board 4 is electrically connected to the first printed circuit board via this contact element 10.

[0019] To ensure the basic flexibility of the second circuit board 4, an elastic connection 8 is located between the second circuit board 4 and the housing shoulder 12, which also has the property of sealing the housing 2.

[0020] In this specific case, this means that the housing 2 is protected from external influences, such as dirt particles or moisture, by the elastic connection 8. Fig. 2 shows a cross-sectional view of the fastening system 1 according to the invention, in which a heat sink 6 is associated with the housing 2. The housing 2 is formed by at least one housing wall 11, preferably made of a thermally conductive material.

[0021] Furthermore, it is preferably also provided that the housing 2 consists of at least two individual parts which are joined together. The individual parts of the housing 2 can be designed as aluminum die-cast parts, extruded parts, stamped parts (sheet metal), or deep-drawn parts (sheet metal).

[0022] The connection between the two individual parts should generally be rigid and durable.

[0023] Overall, the housing 2 according to the invention can therefore be made up of multiple parts, provided that it has a rigid and permanent connection as described above.

[0024] In a further aspect of the present invention, the first printed circuit board 3 is enclosed by a cavity 5. Within this cavity 5, the first printed circuit board 3 is fixed to at least one contact element 10.

[0025] The contact element 10 consists of flexible and pluggable high-current contacts that have a high current-carrying capacity, so-called "power contacts".

[0026] The flexibility of the contact elements 10 ensures, on the one hand, that the contact element 10 has a degree of freedom of movement, particularly in the z-direction, in order to compensate for further tolerances within the mounting system. On the other hand, the pluggable design ensures that simple and easy assembly, especially of the second circuit board 4, is particularly advantageous.

[0027] Furthermore, it is also conceivable to use only a cable connection for the contact element 10, preferably a flat ribbon cable, which is designed for a high current carrying capacity.

[0028] The primary purpose of the contact element 10 used here is to flexibly and electrically connect at least the first circuit board 3 and the second circuit board 4.

[0029] As further shown in Fig. 2, a thermal conducting element 9 is arranged between the second circuit board 4 and the heat sink 6.

[0030] This means that the heat sink 6 and the second circuit board 4 are connected to each other by means of a thermal conducting element 9.

[0031] The thermal conductivity element 9 is preferably a gap filler and / or a gap pad. For the fastening system 1 of a thermal conductivity element 9 according to the invention, it is crucial that this thermal conductivity element 9 has high thermal conductivity and also exhibits good adaptability (elasticity, pastosity) to the geometric properties or characteristics of the two components to be joined (circuit board 4 and heat sink 6).

[0032] As shown in Fig. 3, it is particularly advantageous to further increase the efficiency of cooling the electrical components if a cooling channel 7 is integrated into the heat sink 6. Especially in this configuration, a force-fit connection between the housing shoulder 12 and the heat sink s is necessary, since the cooling channel 7 exerts additional forces and thus loads on the electrical components, such as the two circuit boards 3, 4, due to the pumping movements that occur.

[0033] Electrical components in power electronics are typically liquid-cooled. The cooling channels designed for this purpose are subject to dynamic movements during operation, caused by pressure changes in cooling channel 7, resulting in so-called pumping movements.

[0034] Another essential aspect of the present invention, as can be seen in Figs. 1 to 3, is the use of an elastic connection 8 between the second circuit board 4 and the housing shoulder 12, which also combines a sealing function.

[0035] In general, the goal in power electronics is to press the surfaces / components to be cooled against a cooling surface of the heat sink with a defined minimum force and at the same time to decouple dynamic and mechanical loads from these components so that no increased stresses can occur in the pressure-sensitive components.

[0036] Due to the elastic connection 8 used here, the component to be cooled (second circuit board 4) is stress-free and thus "floating" in the fastening system 1.

[0037] The elastic connection 8 is specifically a spring connection. It can preferably be designed as an elastomeric tension spring and / or an adhesive bond, but is particularly preferably designed as a polymer spring. According to the invention, this elastic connection 8 ensures that tolerance compensation can occur in the fastening system 1 in the z-direction as well as in rotations about the x- and y-axes. However, the rotational degree of freedom is only relevant for small rotation angles or small deflections of the fastening system 1.

[0038] The spring connection 8 according to the invention thus enables tolerance compensation on the housing shoulder 12 and also aligns the second circuit board 4 parallel to the cooling surface of the heat sink 6.

[0039] Likewise, if a cooling channel 7 is present, pump movements can be introduced directly into the housing 2 via the contact surface of the elastic connection 8 and via the housing shoulder 12, and not onto the first circuit board 3, so that the first circuit board 3 above it is mechanically decoupled according to the invention, and thus largely protected from mechanical wear.

[0040] Overall, pump movements of the cooling channel 7 can therefore be reliably and cost-effectively compensated by the spring connection 8 according to the invention.

[0041] In addition, the elastic connection 8 between the housing shoulder 12 and the second circuit board 4 can be continuously formed, so that in addition to tolerance compensation, a sealing function is also fulfilled by the elastic connection 8.

[0042] This is particularly important when the power electronics are delivered to a customer / end user after their manufacture. According to the invention, the second circuit board 4 is positioned in the housing 2 such that, by means of the elastic connection 8, the entire mounting system is protected from particle and / or moisture ingress during the phase up to final assembly, preferably on a motor vehicle. The elastic connection 8 thus acts as a seal to the outside.

[0043] The present invention advantageously provides for the first time a fastening system 1 for superimposed printed circuit boards 3, 4 in a housing 2, in particular in a power electronics housing, which has the following advantages:

[0044] The first advantage is that it enables stress-free storage of several superimposed printed circuit boards 3, 4.

[0045] The second advantage is based on the fact that, in the presence of a cooling channel 7, the pump movements are introduced directly into the housing 2 via the contact surface of the elastic connection 8 and via the housing shoulder 12, and not onto the first circuit board 3, so that the first circuit board 3 above it is mechanically decoupled according to the invention and thus largely protected from additional loads.

[0046] And finally and thirdly, a sealing function is created by the continuous design of the elastic connection 8 between the housing shoulder 12 and the second circuit board 4, so that as a result a protection against particle ingress and moisture is formed.

[0047] Reference sign

[0048] 1 fastening system

[0049] 2 Housing 3 First circuit board

[0050] 4 second circuit board

[0051] 5 Cavity

[0052] 6 heat sinks

[0053] 7 Cooling channel 8 Elastic connection

[0054] 9 Heat conducting element

[0055] 10 contact elements

[0056] 11 Housing wall

[0057] 12 Housing shoulder

Claims

Patent claims 1. Fastening system (1) comprising a housing (2) and an associated heat sink (6), with a first printed circuit board (3) and a second printed circuit board (4) arranged one above the other, wherein the first printed circuit board (3) is fixed in a cavity (5) enclosed by the housing (2) on at least one contact element (10), and the contact element (10) electrically connects at least the first printed circuit board (3) and the second printed circuit board (4), and the heat sink (6) are frictionally connected to each other via a housing shoulder (12), and a heat conducting element (9) is arranged between the second printed circuit board (4) and the heat sink (6), characterized in that an elastic connection (8) is arranged between the second printed circuit board (4) and the housing shoulder (12), which seals the housing (2).

2. Fastening system for a motor vehicle according to claim 1, characterized in that the cooling element (6) has a cooling channel (7).

3. Fastening system for a motor vehicle according to claim 1, characterized in that the elastic connection (8) between the housing shoulder (12) and the second circuit board (4) is formed circumferentially.

4. Fastening system for a motor vehicle according to claim 1, characterized in that the heat conducting element (9) is designed as a gap filler and / or a gap pad.

5. Fastening system for a motor vehicle according to claim 1, characterized in that the at least one contact element (10) between the first circuit board (3) and the second circuit board (4) is flexible and electrically conductive.

6. Fastening system for a motor vehicle according to claim 5, characterized in that the contact element (10) has a degree of freedom in the z-direction.

7. Fastening system for a motor vehicle according to claims 5 to 6, characterized in that the contact element (10) is designed as a pluggable high-current contact and / or as a cable connection.

8. Fastening system for a motor vehicle according to claim 1, characterized in that the elastic connection (8) has a spring connection and / or an adhesive connection.

9. Fastening system for a motor vehicle according to claim 1, characterized in that the pump movements, in the presence of a cooling channel (7), are carried out via the contact surface of the elastic connection. (8) and are introduced directly into the housing (2) via the housing shoulder (12).

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