Fastening unit for connecting thermally stressed components

Description

[0001] The invention relates to a fastening unit for connecting thermally stressed components according to the type specified in the preamble of patent claim 1. Furthermore, the invention also relates to the use of these fastening units according to patent claim 13.

[0002] A generic fastening unit for connecting thermally loaded components, in particular a heat-generating body to a heat sink, comprises a retaining pin and a retaining element. The retaining pin is connected to a retaining head. The retaining pin extends through the retaining element. The retaining head rests against the retaining element. The retaining element engages the body or heat sink and holds it in a fastening direction of the retaining pin. In the fastening position, the retaining head connected to the retaining pin holds the retaining element, which in turn holds the body or heat sink. The fastening pin is anchored in a bore of a component, for example, a heat sink if a thermal energy-generating power module is to be held.

[0003] DE 103 06 227 A1 discloses a power module as a thermally loaded body, which comprises at least one circuit board and heat-generating components. A heat sink is also provided, which is designed as a hollow body and through which a cooling medium flows to dissipate heat. The heat-generating components are arranged on cooling surfaces on the outside of the heat sink and are connected to these in a heat-conducting manner. The heat sink is symmetrical and provided with several inclined cooling surfaces arranged around a longitudinal axis of the heat sink. A fastening screw with a screw head is provided in the centrally arranged longitudinal axis of the heat sink, which connects the heat sink and the circuit board to one another via a spider-shaped clamping spring. The clamping spring presses the heat-generating components onto the cooling surfaces of the heat sink and simultaneously serves to dissipate heat.Such a design is very complex, since a holding element in the form of the spider-shaped clamping spring must be provided for each heat sink shape.

[0004] DE 196 30 173 C2 discloses a power module with semiconductor components having a circuit board on which several chip-shaped power semiconductor components and contact surfaces are arranged. A housing with pressure contacts is arranged on the circuit board to switch the circuit board accordingly. A pressure piece is fixed to the housing via a centrally arranged fastening screw, and the circuit board is firmly connected to the pressure piece. The pressure piece is made of an electrically insulating material. To insulate the fastening element from the circuit board housing, a sleeve is provided in the housing which surrounds the fastening screw. The problem with this design is that the interconnected components - circuit board, housing, and pressure piece - which are made of different materials and are subject to different expansions due to the temperature generated during operation, cannot move relative to one another.This leads to tension and premature material fatigue.

[0005] WO 00 / 62340 A1 discloses a method for joining two thermally loaded components. The components are connected to each other using a floating bearing, which allows relative movement of one component and the other component at least along one axis.

[0006] The invention is based on the object of developing a fastening unit according to the type specified in the preamble of claim 1 in such a way that, while avoiding the disadvantages mentioned, distortion due to thermal expansion of thermally stressed bodies and other bodies is prevented in a simple manner.

[0007] This problem is solved by the characterizing features of claim 1 in conjunction with its preamble features.

[0008] The subclaims form advantageous developments of the invention.

[0009] According to the invention, the retaining element is designed for lateral engagement with the body or heat sink, in that the retaining element has a retaining groove on its side facing the body or heat sink, extending in a longitudinal direction transverse to the fastening direction, wherein at least one groove surface, in the assembled state, at least partially rests against the body or heat sink. This makes it easy to enable relative movement in the event of thermal expansion of the heat sink or body with appropriate assembly.

[0010] According to an advantageous development of the invention, the retaining groove is V-shaped and consists of two groove surfaces, one groove surface being parallel to the longitudinal axis of the fastening pin and the other groove surface being inclined thereto, in particular the groove surfaces being at an acute or obtuse angle to one another. This V-shaped retaining groove makes it easy to hold different edge regions of heat sinks without restricting movement along the retaining groove. Depending on the design of the edge region of the body or heat sink or the expected thermal stress, an acute or obtuse angle is suitable. This results in at least one groove surface of the retaining groove being in linear or planar contact with the body or heat sink to be held.

[0011] Preferably, the retaining element has a substantially rectangular base. This allows it to be easily manufactured and also easily aligned with the body to be held during assembly. In particular, the retaining element has a greater length in the longitudinal direction of the retaining groove than transversely to the longitudinal direction of the retaining groove.

[0012] According to a further embodiment of the invention, the retaining element is symmetrically designed and has two retaining grooves, allowing the retaining element to simultaneously engage with different adjacently arranged bodies or heat sinks. This expands the application area and increases the flexibility of the fastening unit.

[0013] In order to protect the holding element in particular from rotation relative to the body or heat sink to be held, it has proven advantageous for the holding element to have an elongated projection running perpendicular to the pin in the middle, to the side of the fastening pin, which in turn has a further groove on the side remote from the holding head. This groove engages in particular with a strip. This results in a positive connection in the direction of rotation, which, however, does not impair movement relative to the holding groove due to thermal expansion. Twisting of the holding element is thus prevented, but thermal expansion in the longitudinal direction of the groove and the holding groove arranged parallel to it is still maintained.

[0014] Preferably, the additional groove is also V-shaped. This allows for both linear and flat contact, depending on the design of the contact surface of the body or heat sink to be held opposite the groove.

[0015] To ensure that the fastening unit is not too high, the holding head engages in a recess in the holding element and rests there.

[0016] In particular, the retaining head and the recess of the retaining element are cylindrical, so that one end face of the retaining head rests against the end face of the recess, allowing relative compensating movement around the cylinder axis. This is advantageous during assembly for aligning the retaining element with the body or heat sink to be held. Furthermore, with certain body and heat sink designs, this can also be beneficial for balancing stresses.

[0017] Alternatively, it is also possible for the retaining head to be at least partially spherical on its side facing the recess, with the recess having a partially spherical shape adapted to the retaining head, so that the facing spherical surfaces allow for a compensating movement relative to each other in the manner of a ball joint. This ensures that the thermal expansion of the connected body and heat sink does not lead to distortions due to torque.

[0018] The pin may have a thread at its end remote from the retaining head, which aligns with a thread in a hole in the heat sink or body. This allows the mounting unit, and thus the body and heat sink, to be screwed together via the mounting unit.

[0019] Alternatively, the pin can have at least one locking element at its end remote from the retaining head, which is associated with an undercut in a hole in the heat sink or body. The pin is slotted in the area of the end remote from the retaining head. A locking connection allows the body and the heat sink to be connected to each other via the fastening unit. This simplifies assembly.

[0020] Preferably, the body is formed by a power semiconductor. Power semiconductors generate a lot of heat and must be cooled by heat sinks. The mounting units according to the invention are particularly suitable for this purpose, since the heat sinks are subject to expansion.

[0021] The heat sink can be an air heat sink and / or a liquid heat sink.

[0022] According to one embodiment of the invention, the holding head of the fastening unit consists of a thermally and / or electrically insulating material, or of an electrically conductive material.

[0023] According to another aspect, the invention is characterized by the use of at least two fastening units of the type specified above for connecting a heat sink and a body to one another. Two fastening units are mounted diametrically opposite one another on the body or heat sink and form a loose bearing with the body or heat sink. This makes it easy to achieve relative movement between the body and heat sink along the retaining grooves of the retaining elements of the fastening units.

[0024] When assembled, the retaining grooves of the fastening units are primarily aligned parallel to each other.

[0025] Further advantages, features and possible applications of the present invention will become apparent from the following description in conjunction with the embodiments shown in the drawings.

[0026] In the description, claims, and drawings, the terms and associated reference symbols used in the list of reference symbols below are used. In the drawings, the following definitions apply: Fig. 1a is a schematic side view of a fastening unit according to a first embodiment of the invention; Fig. 1b is a perspective view obliquely from above of the fastening unit of Figure 1a ; Fig. 1c an exploded view of Fig. 1b ; Fig. 2a a schematic side view of a fastening unit according to a second embodiment of the invention; Fig. 2b a perspective view obliquely from above of the fastening unit of Figure 2a ; Fig. 2c an exploded view of Fig. 2b; Fig. 3a a schematic side view of a fastening unit according to a third embodiment of the invention; Fig. 3b a perspective view obliquely from above of the fastening unit of Figure 3a ; Fig. 4a a schematic side view of a fastening unit according to a fourth embodiment of the invention; Fig. 4b a perspective view obliquely from above of the fastening unit of Figure 4a ; Fig. 5 shows a first application example in a sectional view of the third embodiment of the invention in the assembled state; Fig. 6 shows a second application example in a sectional view of the third embodiment of the invention in the assembled state, and Fig. 7 shows a third application example in a perspective exploded view of the first embodiment of the invention in the assembled state.

[0027] In the Fig. 1a, 1b and 1cA first embodiment of a fastening unit 10 is shown. The fastening unit 10 comprises a fastening pin 12, which is firmly connected to a holding head 14 using the same material. In the present case, the fastening pin 12 is made of a single piece with the holding head 14. The holding head 14 is cylindrical and has a hexagon socket 12a for screwing in the fastening pin 12 during assembly. The hexagon socket 12a forms an internal drive for the fastening pin 12.

[0028] In addition, the fastening unit 10 comprises a holding element 16, which has a through-bore 18 and, concentric thereto, a cylindrical recess 20 on the upward-facing side 10a. The holding element 16 has a rectangular basic shape in plan view. The holding element 16 is longer in the longitudinal direction than in the transverse direction. On a first longitudinal side 10b, a holding arm 22 projects over the entire longitudinal side 10b and is inclined relative to the upward-facing side 10a. Below the holding arm 22, a V-shaped holding groove 24 is provided parallel to the longitudinal side 10a, wherein the groove surface 24a closest to the through-bore 18 runs parallel to the through-bore 18 and the further groove surface 24b is inclined thereto.

[0029] As in particular the Fig. 1a As can be seen, the groove surfaces 24a and 24b of the retaining groove 24 form an acute angle to each other.

[0030] The groove surface 24a is extended downwards and the underside of the holding element 16 slopes downwards in some areas to the groove surface 24a.

[0031] The fastening pin 12 with the retaining head 14 is inserted into the through-hole 18 in the fastening direction, designated by the reference numeral 26, until the retaining head 14 rests with its end face on the upwardly facing surface of the recess 20. In this state, the upper end face of the retaining head 14 is flush with the upwardly facing side 10a.

[0032] By inserting the fastening pin 12 with the holding head 14 into the through-hole 18 and the recess 20 of the holding element 16, the fastening pin 12 is also anchored in a heat sink or another component, as will be explained in more detail below.

[0033] In the Fig. 2a, 2b and 2c A second embodiment of the invention is shown. As shown in the Figures 1a, 1b and 1cThe fastening unit 10 shown also has the fastening pin 12 with the holding head 14. Only the holding element 16 is designed differently in that on both longitudinal sides 10b and 10c a holding arm 22a, 22b projects laterally over the entire longitudinal side 10b or 10c, a holding groove 24c, 24d is provided under each holding arm 22a, 22b, and the groove surface 24a running parallel to the through-bore 18 is extended downwards. This results in a web running laterally to the fastening pin 12 with a central groove 30. The holding element 16 is designed symmetrically with two holding grooves 24c and 24d and a further central groove 30. The groove 30, the web 30a and the holding grooves 24c and 24d run parallel to one another and perpendicular to the longitudinal axis and fastening direction 26 of the fastening unit 10.

[0034] In the Fig. 3a and 3bA third embodiment of the invention is shown, which essentially corresponds to the second embodiment, wherein the fastening pin 12 has a thread 32, which is associated with a thread (not shown here) in a heat sink (also not shown here). The fastening pin 12 is thus designed to be screwed into an associated thread.

[0035] In the Fig. 4a and 4ba fourth embodiment of the invention is shown, which essentially corresponds to the second embodiment, wherein the fastening pin 12 has a slot 36 running from its free end 34 into the holding element 16. In addition, the fastening pin 12 and the holding element 16 are designed and manufactured from a single piece. At the free end 34 there is a notch 38 which forms a shoulder 38a and decreases in size towards the free end 34. The fastening pin 12 and the notch 38 are essentially cylindrical or conical. In a bore (not shown here) in a heat sink (likewise not shown here), an undercut is made, in which the notch 38 engages in the assembled state and the shoulder 38a comes to rest against the undercut. The fastening unit 10 is fastened in the bore via the notch 38.

[0036] In the Fig. 5 to 7different embodiments of applications of the fastening units 10 according to the invention are shown.

[0037] The Figs. 5 and 6 each show fastening units 10 according to the first and third embodiments with a fastening pin having a thread 32 and are each screwed into a threaded bore 40 of a heat sink 42.

[0038] In Fig. 5The heat sink 42 is essentially cuboid-shaped. On the upper side, thermal energy-generating power semiconductors 44 are connected to the heat sink via the fastening units 10, so that the holding arms 22 with the holding grooves 24 of the fastening units each come into contact with the edge of the power semiconductor 44. On the outer sides of the heat sink, fastening units 10 according to the first embodiment are provided, which engage and hold only one edge of a power semiconductor 44, wherein in the central region, fastening units 10 according to the third embodiment are provided, which with their holding arms 22a, 22b and the holding grooves 24c, 24d engage and hold the edges of two different power semiconductors 44. The holding arms 22a, 22b with their holding grooves 24c, 24d each lie linearly or flatly against the edge of the power semiconductor 44.All retaining grooves 24 of the fastening units 10 are aligned parallel to each other.

[0039] In Fig. 6 , a heat sink is shown that is trapezoidal in section. Here, too, the power semiconductors 44 are arranged on the top side of the heat sink 42. On the outer side of the heat sink 42, fastening units 10 according to the first embodiment are screwed into the heat sink 42 and hold a power semiconductor 44 at the edge. In the central region, fastening units 10 according to the third embodiment are screwed into a corresponding bore at the edges of the heat sink 42, engaging and holding two adjacent power semiconductors 44. This makes it clear that the V-shaped holding grooves 24 can also easily fix power semiconductors 44 that are inclined to one another, without the holding elements 16 having to be adjusted.

[0040] In Fig. 7The arrangement of the fastening units 10 in the heat sink 42 and relative to the edge of the power semiconductor is illustrated. The fastening pins 12 are screwed into associated holes 40 in the heat sink 42. These are fastening units 10 according to the first embodiment.

[0041] The retaining grooves 24 and the fastening of the fastening units 10 on opposite sides enable the power semiconductors 44 to expand parallel to the retaining grooves 24. This prevents distortion. For example, two fastening units 10 are arranged on each long side of a power semiconductor 44. Depending on whether the fastening units 10 are intended to hold one or two adjacent power semiconductors 44, the embodiment of the fastening unit 10 with one holding arm 22 or two holding arms 22a, 22b is used. The power semiconductors 44 are thus held by a loose bearing, i.e., movement in one direction is possible. This direction is the main expansion direction of the power semiconductor 44.

[0042] The distance between two power semiconductors 44 and the edge of the power semiconductor 44 can be adjusted via the length of the lateral projection of the holding arms 22.

[0043] Preferably, a set of retaining elements 16 is provided, each having different lengths of lateral projection of the retaining arms 22. Depending on the requirements, the retaining element 16 is then used with a larger laterally projecting retaining arm 22 or a smaller laterally projecting retaining arm 22. The fastening pin 12 with the retaining head 14 can remain the same for the different retaining elements 16. However, fastening pins 12 with different lengths and diameters can also be provided during assembly.

[0044] Depending on the application, the fastening units 10 can be electrically conductive, electrically insulating, thermally conductive, or thermally insulated. It is also possible for the retaining elements 16 on one side and the fastening pin 12 with retaining head 14 on the other side to have different material properties.

[0045] The fastening units 10 according to the invention thus easily enable the expansion of the power semiconductors 44 and thus a relative movement between the power semiconductors 44 and the heat sink 42. The firm anchoring of the fastening pins 12 prevents elastic deformation along the fastening axis. This easily prevents distortion during operation. List of reference symbols

[0046] 10 Fastening unit 10a Upward-facing side 10b Long side - right 10c Long side - left 12 Fastening pin 12a Hexagon socket, internal drive 14 Retaining head 16 Retaining element 18 Through hole 20 Recess 22 Retaining arm 22a Retaining arm - left 22b Retaining arm - right 24 Retaining groove 24a Groove surface parallel to through hole 18 24b Groove surface diagonal to through hole 18 24c Retaining groove - left 24d Retaining groove - right 26 Fastening direction 28 Web 30 Additional groove 30a Web 32 Thread 34 Free end 36 Slot 38 Detent 40 Hole 42 Heat sink 44 Power semiconductor

Claims

1. Fastening unit (10) for connecting thermally stressed components to each another, in particular a heat-generating body (44) to a heat sink (42), comprising a holding pin (12) and a holding element (16), wherein the holding pin (12) is connected to a holding head (14), the holding pin (12) engages through the holding element (16), the holding head (14) bears against the holding element (16), and the holding element (16) engages on the body (44) or the heat sink (42) and holds the latter in a fastening direction (26) of the holding pin (12), with the holding element (16) being designed for lateral engagement on the body (44) or the heat sink (42) for which purpose the holding element (16) has, on its side facing the body (44) or the heat sink (42), a holding groove (24) that extends in a longitudinal direction transverse to the fastening direction, with at least one groove surface (24a, 24b), in the assembled state, coming to rest against the body (44) or the heat sink (42), at least in some areas, characterized in that, in its center, on the side of the fastening pin (12), the holding element (16) has an elongate projection (web 30a) each, which extends perpendicularly to the fastening pin (12) and which in turn has an additional groove (30) on the side remote from the holding head (14).

2. Fastening unit according to claim 1, characterized in that the holding groove (24) is V-shaped, formed by two groove surfaces (24a, 24b), of which one groove surface (24a; 24b) extends in parallel to the longitudinal axis of the fastening pin (12) and the other groove surface (24a; 24b) is inclined thereto, which groove surfaces (24a, 24b) are in particular at an acute or obtuse angle to each another.

3. Fastening unit according to any one of claims 1 or 2 above, characterized in that the holding element (16) has a substantially rectangular base.

4. Fastening unit according to any one of the preceding claims, characterized in that the length of the holding element (16) is longer in the longitudinal direction of the holding groove (24) than transversely to the longitudinal direction of the holding groove (24).

5. Fastening unit according to any one of the preceding claims, characterized by a symmetrical design of the holding element (16) with two holding grooves (24), so as to enable the holding element (16) to come to rest against different adjacent bodies (44) or heat sinks (42) at the same time.

6. Fastening unit according to any one of the preceding claims, characterized in that the additional groove (30) is V-shaped.

7. Fastening unit according to any one of the preceding claims, characterized in that the holding head (14) engages in a recess (20) of the holding element (16) and makes contact there.

8. Fastening unit according to claim 7, characterized in that the holding head (14) is cylindrical and the recess (20) is cylindrical, resulting in one end face of the holding head (14) resting on the end face of the recess (20), which allows for a relative compensatory movement about the cylinder axis.

9. Fastening unit according to any one of claims 1 to 8 above, characterized in that the holding head (14) is at least partially spherical in shape on its side facing the recess (20), the recess (20) has a partial spherical shape adapted to the holding head (14), which allows for a compensatory movement of the spherical surfaces facing each another relative to one another in the manner of a ball-and-socket joint.

10. Fastening unit according to any one of the preceding claims, characterized in that the fastening pin (12) has, at its end (34) remote from the holding head (14), a thread (32) which is associated with a thread (32) in a bore (40) in the heat sink (42) or the body (44).

11. Fastening unit according to any one of the preceding claims, characterized in that the fastening pin (12) has, at its end (34) remote from the holding head (14), a thread (32) which is associated with a thread (32) in a bore (40) in the heat sink (42) or the body (44).

12. Fastening unit according to any one of the preceding claims, characterized in that the holding head (14) is made of a thermally and / or electrically insulating material, or of an electrically conductive material.

13. Use of at least two fastening units of the type claimed in any one of the preceding claims for connecting a heat sink (42) and a body (44) together, characterized in that two fastening units (10) are attached opposite one another on the edge of the body (44) or the heat sink (42) and thus form a loose bearing arrangement with the body (44) or the heat sink (42).

14. Use according to claim 13, characterized in that, in the assembled state, the holding grooves (24) of the fastening units (10) are aligned parallel to each another.