Capacitor and arrangement with circuit board and capacitor

Abstract

Capacitor, comprising a winding element arranged in a housing (1), a mounting plate (11) comprising a non-conductive material and attached to the housing (1), and a metal element (7) which is arranged between the housing (1) and the mounting plate (11), wherein the metal element (7) comprises a projecting part (9a, 9b) which projects through the mounting plate (11), wherein the metal element (7) is not galvanically connected to the winding element.

Description

[0001] The present invention relates to a capacitor. More particularly, the present invention relates to a capacitor to be mounted on a printed circuit board (PCB) by surface mount technology (SMD).

[0002] JP 3 497 242 B2, US 2012 / 0 081 835 A1, US 2010 / 0 267 252 A1, CN 208 478 137 U, DE 10 2008 049 189 A1 and JP H10- 32 137 A show capacitors and structures that enable surface mounting of the capacitors.

[0003] Standard SMD capacitors are often poorly mechanically attached to a circuit board using their ribbon wires. Furthermore, heat dissipation from the SMD capacitor to the circuit board is limited by the physical dimensions of the wires.

[0004] Therefore, there is a need for an improved surface mount capacitor that overcomes at least one of the disadvantages discussed above. It is an object of the present invention to provide such a capacitor.

[0005] This problem is solved by the subject matter of patent claim 1.

[0006] A capacitor is provided comprising a winding element disposed in a housing, a mounting plate comprising a non-conductive material and secured to the housing, and a metal element disposed between the housing and the mounting plate, the metal element including a protruding portion extending through the mounting plate. The capacitor may additionally comprise a sealing element.

[0007] By adding the metal element between the capacitor case and the mounting plate, the disadvantages of SMD capacitors discussed above can be overcome. The metal element can be thermally bonded to the case. This allows heat absorbed by the case to be transferred through the metal element to a printed circuit board during surface mounting, for example, by reflow soldering. Thus, during reflow soldering, heat can be applied very quickly to the soldering pads of the circuit board, accelerating the soldering process because the heat can be applied not only by the circuit board itself, but also by heat absorbed by the case.Furthermore, the metal element can remain thermally bonded to the housing during normal operation of the capacitor, allowing the heat generated by the winding element in the housing to be transferred through the metal element to the circuit board. Thus, the addition of the metal element enables the circuit board to be used as a heat sink. For example, ripple currents in the winding element can generate heat. The metal element can contribute to the thermal management of the capacitor by conducting heat away from the housing.

[0008] The metal element can also contribute to improved mechanical attachment of the capacitor to the circuit board. In particular, the metal element can provide one or more mechanical contacts that can be attached to the circuit board, for example, by soldering.

[0009] The mounting plate may be a small plate with side dimensions similar to the side dimensions of the enclosure. The enclosure may be attached to the mounting plate. The mounting plate may be designed to be attached to a printed circuit board during surface mounting.

[0010] The protruding part of the metal element may extend in a direction away from the winding element above the mounting plate.

[0011] The protruding part of the metal element can be configured to be attached to a circuit board when the capacitor is surface-mounted to the circuit board. In particular, the protruding part of the metal element can form a mechanical contact that can be attached to a soldering surface of the circuit board by soldering.

[0012] The metal element can be configured to transfer heat from the housing to the circuit board. Accordingly, the metal element can accelerate the soldering process during surface mounting, as heat absorbed by the housing is effectively transferred to the soldering surface. Furthermore, during normal operation of the capacitor, the metal element can facilitate heat transfer from the housing to the circuit board, allowing the circuit board to be used as a heat sink.

[0013] The winding element may comprise two terminals forming two contacts configured to be attached to the circuit board during surface mounting. The two terminals of the winding element may provide electrical contact between the winding element and the circuit board. Furthermore, the two terminals of the winding element may also be thermally and mechanically connected to the circuit board.

[0014] The metal element can provide two additional mechanical contacts designed to be secured during surface mounting. These additional mechanical contacts can be formed by the protruding part of the metal element. The contacts provided by the metal element are preferably not galvanically connected to the winding element. The contacts provided by the metal element can be mechanically and thermally connected to the circuit board. Thus, the metal element can contribute to a better mechanical and thermal connection between the circuit board and the capacitor.

[0015] The connections of the winding element can protrude through a recess in the mounting plate.

[0016] The metal element can be clamped between the mounting plate and the housing. The metal element can be merely mechanically attached to the housing. In particular, no adhesive or external plastic parts are required to attach the metal element to the housing. Instead, the metal element can be attached to the housing using the same mechanical means used to attach a sealing element that closes the housing off from the rest of the housing. In particular, the metal element can be attached to the housing using a bead and a curl. The bead and the curl are required in any case to close the housing with the sealing element, so no additional means for attaching the metal element are required. The metal element can be arranged between the sealing element and the mounting plate. In particular, the metal element can bear against the sealing element arranged at the lower end of the housing.The metal element also rests on the mounting plate.

[0017] The metal element may comprise an annular base body. The annular shape of the base body may define an opening, through which the terminals of the winding element may pass. The opening in the base body may be large enough to allow the annular base body to be combined with a wide variety of winding elements and sealing elements, with the position and size of the terminals not being restricted by the opening in the metal element.

[0018] The protruding part of the metal element can be a pin. The pin can be bent before or after it is inserted through an opening in the mounting plate. By bending the pin, the metal element can be further secured to the mounting plate, preventing any axial movement of the metal element relative to the mounting plate.

[0019] The pin may be bent to form a surface parallel to a mounting surface of the capacitor. The mounting surface of the capacitor may be a lower surface of the mounting plate facing away from the winding element. The mounting surface of the capacitor may be configured to engage a printed circuit board when the capacitor is surface-mounted to the printed circuit board.

[0020] The metal element may be a stamped metal sheet, the protruding part being formed by stamping technology.

[0021] The metal element is not galvanically connected to the winding element.

[0022] The capacitor may include a sealing element that seals the housing. The metal element may be arranged between the sealing element and the mounting plate.

[0023] The present invention further relates to an assembly comprising a printed circuit board and the capacitor described above, wherein the capacitor is attached to the printed circuit board by means of surface mounting.

[0024] The following preferred embodiments of the present invention will be described with reference to the drawings. Fig. 1 shows a housing, a sealing element and a metal element of a capacitor in an exploded view. The Fig. 2 and Fig. 3 show perspective views of a capacitor according to a first embodiment during various stages of an assembly process; Fig. 4 shows the capacitor according to the first embodiment after completion of the assembly process; the Fig. 5, Fig. 6 and Fig. 7 shows a metal element according to a first embodiment before bending a protruding part; the Fig. 8, Fig. 9 and Fig. 10 shows a metal element according to the first embodiment after bending the protruding part; the Fig. 11 and Fig. 12 show a capacitor according to a second embodiment during various stages of an assembly process; and the Fig. 13 and Fig. 14 show the capacitor of the second embodiment after completion of the assembly process.

[0025] Fig. 1 shows a housing 1, a sealing element 5 and a metal element 7 of a capacitor in an exploded view.

[0026] The capacitor comprises a winding element arranged within the housing 1. The housing 1 is an aluminum can. The housing 1 is cylindrical. The winding element comprises two terminals 2a, 2b that protrude from the housing 1. The terminals 2a, 2b of the winding element are electrical terminals designed to be connected to the printed circuit board during surface mounting.

[0027] The housing 1 has a first end 3 and a second end 4. The first end 3 of the housing 1 is open. The wires forming the terminals 2a, 2b of the winding element protrude from the first end 3 of the housing 1. The second end 4 of the housing 1 is arranged opposite the first end 3.

[0028] The second end 4 is closed. In this document, the first end 3 is also referred to as the lower end, and the second end 4 is also referred to as the upper end.

[0029] The capacitor further comprises a sealing element 5 configured to seal the housing 1. In particular, the sealing element 5 is configured to seal the lower end 3 of the housing 1. The sealing element 5 comprises a non-conductive material, for example rubber. Rubber is particularly suitable as the material of the sealing element 5 because rubber has high elasticity and can therefore reliably seal the housing 1. The sealing element 5 comprises two holes 6 configured to receive the terminals 2a, 2b of the winding element. The sealing element 5 is inserted into the housing 1 from the lower end 3 of the housing 1.

[0030] The capacitor comprises the metal element 7, which is arranged below the sealing element 5 in a direction away from the winding element. The metal element 7 has an annular base body 8 and includes two protruding parts 9a, 9b.

[0031] Further details of the metal element 7 are given in each of the Fig. 4, Fig. 5 and Fig. 6, which are perspective views of the metal element 7 before bending the projecting parts 9a, 9b of the metal element 7. Thus, each of the Fig. 4 to 6 the metal element 7 before completing the assembly process.

[0032] The annular base body 8 of the metal element 7 includes an opening 10. When the metal element 8 is mounted on the capacitor, the terminals 2a, 2b of the winding element extend through the opening 10 in the base body 8. The opening 10 is larger than the distance between the terminals 2a, 2b. Accordingly, the metal element 7 can be combined with a wide variety of winding elements and sealing elements, whereby the position of the terminals 2a, 2b can be varied.

[0033] The metal element 7 comprises two protruding parts 9a, 9b. Both protruding parts 9a, 9b protrude in the same direction, i.e., in a direction away from the winding element. Each of the protruding parts 9a, 9b is a pin. The length of the pins is selected such that the protruding parts 9a, 9b protrude through a mounting plate 11, which will be described later with reference to Fig. 3. The length of the protruding parts 9a, 9b is selected such that a part of the protruding parts 9a, 9b that protrudes through the mounting plate 11 can be bent over and form a contact for surface mounting.

[0034] The sealing element 5 comprises a projection 20 that projects in a direction away from the winding element and toward the metal element 7. The shape of the projection 20 is adapted to the shape of the opening 10 in the annular base body 8 of the metal element. The metal element 7 is designed to be attached to the sealing element 5. When the metal element 7 is attached to the sealing element 5, the projection 20 is inserted into the opening 10. The projection 20 stabilizes the mechanical connection of the metal element 7 to the sealing element 5 before mounting the mounting plate 11 and before bending the protruding parts 9a, 9b of the metal element 7.

[0035] The Fig. 2 and Fig. 3 show a capacitor according to a first embodiment during an assembly process. Fig. 4 shows the capacitor according to the first embodiment after completion of the assembly.

[0036] The capacitor is designed to be attached to a printed circuit board (PCB) using a surface mount process. The capacitor is mechanically and galvanically connected to the PCB when surface mounted to the PCB.

[0037] In Fig. 2, which represents a first stage of the assembly process, the terminals 2a, 2b are wires with a circular cross-section. The metal element 7 has been placed on the sealing element 5 and is held by the projection 20 on the sealing element 5.

[0038] Fig. Figure 3 shows the capacitor in a second stage of the assembly process. The sealing element 5 and the metal element 7 have been arranged at the lower end of the housing 1. A bead 12 and a curl 13 have been added to the lower end of the housing 1. By adding the bead 12 and the curl 13, the sealing element 5 is arranged in the housing 1 and fastened to the housing 1 such that the housing 1 is sealed by the sealing element 5. The bead 12 and the curl 13 provide a mechanical fastening that prevents movement of the sealing element 5 relative to the housing 1. The bead 12 and the curl 13 further mechanically fasten the metal element 7. No additional elements or means are required to fasten the metal element 7 to the housing 1. Rather, the same fastening means that are used to fasten the sealing element 5, i.e.the bead 12 and the curl 13, also the fastening of the metal element 7 to the housing 1.

[0039] The terminals 2a, 2b of the winding element were pressed and cut to form contact pins. The contact pins of the winding element formed by the terminals 2a, 2b are connected by a first imaginary line perpendicular to a second imaginary line connecting the protruding parts 9a, 9b of the metal element 7.

[0040] The capacitor further comprises the above-mentioned mounting plate 11, which is Fig. 3. The mounting plate 11 is adapted to be attached to the lower end of the capacitor.

[0041] The mounting plate 11 has a first surface 14 facing the housing. The mounting plate 11 has a second surface 15 facing away from the housing 1. The second surface 15 of the mounting plate 11 is a mounting surface of the capacitor, which rests against the circuit board when the capacitor is surface-mounted.

[0042] The mounting plate 11 includes four openings 16 configured to receive the two protruding parts 9a, 9b of the metal element 7 and the two terminals 2a, 2b of the winding element. The mounting plate 11 comprises a non-conductive material. The mounting plate 11 has a thickness that is less than the length of the protruding parts 9a, 9b of the metal element 7 and less than the length of the terminals 2a, 2b of the winding element.

[0043] Fig. Figure 4 shows the capacitor after the assembly process has been completed. The protruding parts 9a, 9b of the metal element 7 were passed through the openings 16 in the mounting plate 11, and then the protruding parts 9a, 9b were bent.

[0044] Each of the Fig. 8, Fig. 9 and Fig. 10 shows the metal element 7 after bending the pins.

[0045] The capacitor comprises four mechanical contacts on its mounting surface, which can be attached to the circuit board by surface mounting. Two of the contacts are formed by the terminals 2a, 2b of the winding element. These contacts are designed to provide mechanical attachment and electrical contact of the winding element to the circuit board. Furthermore, two contacts are formed by the protruding parts 9a, 9b of the metal element 7. These two contacts are designed to provide mechanical attachment of the capacitor to the circuit board after surface mounting. The protruding parts 9a, 9b of the metal element 7 do not provide an electrical connection to the winding element. The four contacts are arranged to form four arms of a cross, with the contacts not touching each other.

[0046] Each of the contacts also provides a thermal connection. In particular, the metal element 7 is thermally connected to the housing 1. Accordingly, the metal element 7 contributes to accelerating heat transfer to the solder pads of the printed circuit board during surface mounting, for example, by reflow soldering.

[0047] Surface mounting can be performed, for example, using a reflow soldering process. The capacitor can be placed on the circuit board, with each of the four contacts positioned on a soldering pad. The capacitor on the circuit board is moved and heated in an oven. To accelerate the heating process, it is essential to apply the heat quickly to the soldering pads.

[0048] Heat absorbed by the housing 1 during reflow soldering can be transferred directly to the solder pads by the metal element 7, which is thermally bonded to the housing 1. Thus, the solder pads are heated not only by heat applied to the circuit board, but also by heat absorbed by the housing 1 and transferred to the solder pads by the metal element 7. Accordingly, the metal element 7 enables the acceleration of surface mounting of the capacitor to the circuit board.

[0049] During normal operation of the capacitor, heat can also be transferred from the housing 1 through the metal element 7 to the circuit board. Thus, the metal element 7 enables the circuit board to be used as a heat sink. Ripple currents applied to the capacitor during normal operation can generate heat, and this heat is generally transferred from the winding element to the housing 1. Since the housing 1 is thermally connected to the circuit board by the metal element 7, the circuit board can be used as a heat sink.

[0050] As explained above, the metal element 7 is mechanically attached to the housing 1. No adhesive or external plastic parts are required to attach the metal element 7. Unlike adhesive or external plastic parts, which are sensitive to temperature changes and humidity and generally suffer from aging, a purely mechanical attachment of the metal element 7 does not suffer from aging due to temperature changes or humidity. The mechanical attachment of the metal element 7 is stable within a wide temperature range and within a wide humidity range.

[0051] The Fig. 11 and Fig. 12 show a capacitor according to a second embodiment during various stages of the assembly process.

[0052] The Fig. 13 and Fig. 14 shows the capacitor after completion of the assembly process.

[0053] The second embodiment differs from the first embodiment in the design of the metal element 7. According to the second embodiment, the metal element 7 is formed from a stamped metal sheet, which also has an annular base body 8. Furthermore, the protruding parts 9a, 9b of the metal element 7 are not formed by pins, but by a metal strip, which projects towards the mounting surface in its central part 17. A first end 18 and a second end 19 of the strip are connected to the annular base body. The first end 18 and the second end 19 of the strip are connected by the central part 17. The central part 17 of the protruding elements 9a, 9b is U-shaped.

[0054] Fig. Figure 11 shows the capacitor of the second embodiment in a first stage of the assembly process similar to Fig. 2. The metal element 7 is arranged under the sealing element 5 of the housing 1.

[0055] Fig. 12 shows the capacitor in a second stage of the assembly process similar to Fig. 3. In the second embodiment, the mounting plate 11 is adapted to the shape of the metal element 7 of the second embodiment. The openings 16 in the mounting plate 11 are adapted to the protruding parts 9a, 9b. Accordingly, the openings in the mounting plate of the second embodiment are formed in a circular section.

[0056] In Fig.Figure 14 shows that, according to the second embodiment, there are also four mechanical contacts that can be attached to a printed circuit board by surface mounting. Two of the contacts are formed by the terminals 2a, 2b of the winding element, and two additional contacts are formed by the protruding parts 9a, 9b of the metal element 7, which are preferably not galvanically connected to the winding element, but rather provide an improved mechanical and thermal connection between the housing 1 and the printed circuit board.

Claims

[1] Capacitor comprising a winding element arranged in a housing (1), a mounting plate (11) comprising a non-conductive material and which is attached to the housing (1), and a metal element (7) which is arranged between the housing (1) and the mounting plate (11), wherein the metal element (7) comprises a projecting part (9a, 9b) which projects through the mounting plate (11), wherein the metal element (7) is not galvanically connected to the winding element. [2] A capacitor according to claim 1, wherein the projecting part (9a, 9b) of the metal element (7) is adapted to be fixed to a circuit board when the capacitor is surface-mounted to the circuit board. [3] Capacitor according to the preceding claim, wherein the metal element (7) is arranged to transfer heat from the housing (1) to the circuit board. [4] Capacitor according to one of claims 2 or 3, wherein the winding element comprises two terminals (2a, 2b) forming two contacts of the capacitor, which are adapted to be attached to the circuit board during surface mounting, and wherein the metal element (7) provides two additional mechanical contacts adapted to be fixed during surface mounting. [5] Capacitor according to one of the preceding claims, wherein the metal element (7) is thermally connected to the housing (1). [6] Capacitor according to one of the preceding claims, wherein the mounting plate (11) comprises an opening (16), the projecting part (9a, 9b) of the metal element (7) protruding through the opening (16). [7] Capacitor according to one of the preceding claims, wherein the metal element (7) is clamped between the mounting plate (11) and the housing (1). [8] Capacitor according to one of the preceding claims, wherein the metal element (7) is merely mechanically attached to the housing (1). [9] Capacitor according to one of the preceding claims, wherein the metal element (7) is attached to the housing (1) by means of a bead (12) and a flanged edge (13). [10] Capacitor according to one of the preceding claims, wherein the metal element (7) comprises an annular base body (8). [11] Capacitor according to one of the preceding claims, wherein the projecting part (9a, 9b) of the metal element (7) is a pin. [12] Capacitor according to the preceding claim, wherein the pin is bent such that it forms a surface parallel to a mounting surface of the capacitor. [13] Capacitor according to one of claims 1 to 10, wherein the metal element (7) is a stamped metal sheet and the protruding part (9a, 9b) is formed by stamping technology. [14] Capacitor according to one of the preceding claims, wherein the capacitor comprises a sealing element (5) which seals the housing (1). [15] Capacitor according to the preceding claim, wherein the metal element (7) is arranged between the sealing element (5) and the mounting plate (11). [16] An assembly comprising a printed circuit board and a capacitor according to any one of the preceding claims, wherein the capacitor is surface mounted to the printed circuit board.

Images