Capacitor, method for manufacturing capacitor and capacitor application

Abstract

To provide a small-sized, high-capacity, surface-mountable wound capacitor, a method for manufacturing the same, and specific application scenarios for the capacitor.SOLUTION: A capacitor C is a wound type, and has flat bottom surfaces FBS at lead frame shaped surface-mountable terminal T1, T2. A heat sink HSN arranged below a capacitance element CE and / or a heat shield HSH arranged between the capacitance element and the connection side of the terminals are provided, enabling surface mounting to deliver high capacitance in a compact form factor. A housing in which elements are arranged, is filled with a resin.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] (Technical field) The present application refers to capacitors with improved properties, methods for manufacturing the capacitors, and specific use scenarios for the capacitors. [Background technology]

[0002] EMI reduction circuits (EMI = electromagnetic interference) use EMI capacitors for such purposes with AC or DC electrical waveforms. EMI capacitors are connected between the input and output to reduce EMI directed towards the system at the input or output. DC link capacitors, for example, electrically connect a vehicle's switching devices to its DC electrical environment, e.g., the battery. Power converters can include inverters that operate at high power levels in a frequency range where undesirable frequencies should be avoided.

[0003] Capacitors can be divided into two categories based on their structure: a capacitor can contain a layer stack of conductive and dielectric layers stacked on top of each other, or a capacitor can contain a dielectric material between the two electrodes, with the material of the electrodes and the dielectric material wound between them.

[0004] For capacitors, it is generally desirable for the capacitor to have a large capacitance, a small spatial dimension, be suitable for high voltage and high power applications, and provide good performance and good reliability.

[0005] Furthermore, capacitors can be divided into categories according to their integration into the external circuit environment. Capacitors can include terminals provided for THT (through hole technology), in which the capacitor terminals are placed in holes and soldered to the external circuit environment. Another category of connection is obtained via SMT (surface mount technology), in which the terminals of an electrical component are placed on a carrier and electrically and mechanically connected to contacts of the external circuit environment on the carrier surface. Therefore, it is desirable to have a compact capacitor that offers the above-mentioned advantages of being surface mountable to the external circuit environment. In particular, it is desirable to have a compact SMT-compatible capacitor with a large capacitance. Summary of the Invention

[0006] To this end, a capacitor is provided according to independent claim 1. The dependent claims provide preferred embodiments, methods and uses.

[0007] The capacitor includes a first electrode, a second electrode, and a dielectric material. The dielectric material is disposed between the first electrode and the second electrode. The capacitor further includes a first terminal and a second terminal. The first terminal is electrically connected to the first electrode, and the second terminal is electrically connected to the second electrode. The first electrode material, the second electrode material, and the dielectric material form a wound capacitance element. The first terminal and the second terminal are surface-mountable terminals.

[0008] Such capacitors therefore belong to the category of wound-type capacitors and to the category of SMT-compatible capacitors.

[0009] The capacitor can be adapted to the reflow requirements, specifically, the capacitor can be sufficiently insensitive to the required temperature and duration of the reflow process.

[0010] In the reflow process, SMT components are placed with their corresponding terminals electrically and mechanically connected onto the connection pads of a carrier. To achieve this, the entire component is heated, for example in a reflow oven, to a temperature and for a duration sufficient to establish reliable electrical and mechanical contact between the terminals and the connection pads of the carrier. In contrast to THT connections, where high temperatures are only required at the terminals for soldering, the corresponding high temperatures are applied to the electrical component as a whole. Therefore, all elements and materials must meet the reflow requirements.

[0011] It has been found that capacitors such as those described above can meet reflow requirements, which allows for the provision of capacitors, particularly capacitors with large capacitance, that are wound capacitors and can be processed in SMT processes.

[0012] The capacitors can have a capacitance of 1 μF or greater, specifically between 1.1 μF and 2.2 μF in a compact housing that can be processed in an SMT process.

[0013] Furthermore, the first terminal and the second terminal can include a material selected from steel, copper, brass, or aluminum, and the terminals can include a coating layer of pure tin or a tin alloy to support the soldering process.

[0014] The first terminal and the second terminal may include or be made of the same material, preferably a material that provides high electrical conductivity and low thermal conductivity.

[0015] The dielectric material can be selected from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PPS (polypropylene sulfide), PTFE (polytetrafluoroethylene), PS (polystyrene), PC (polycarbonate) and PET HT (HT = high temperature).

[0016] It has been found that such dielectric materials are compatible with SMT processes and can provide reliable capacitors. The use of such materials is possible because an annealing process can be performed during fabrication to prepare the dielectric material for subsequent SMT processing steps. Furthermore, possible shrinkage of the dielectric material's thickness can be compensated for by providing a dielectric material with a thickness after SMT processing that meets the requirements for high-voltage applications, high-power applications, and high capacitance.

[0017] Furthermore, the heat resistance of the capacitor can be further increased by providing a heat shield within the capacitor. The heat shield can be located below the capacitance element of the capacitor. In this context, "below the capacitance element" means that the heat shield is located between the capacitance element and the location of the connection side of the terminal to be electrically connected to an external circuit element.

[0018] The heat shield can include a material with low thermal conductivity. The heat shield can be used to protect the sensitive capacitance element of the capacitor, particularly the heat-sensitive dielectric material of the capacitance element, from heat entering the capacitor, particularly via a path along the terminals when the terminals establish a thermal bridge from the outside to the capacitance element. Thus, the heat shield can include small openings through which the conductor elements of the terminals can be routed to electrically connect the capacitance element to the external circuit environment. However, additional heat radiated by the lower portions of the terminals is blocked by the heat shield.

[0019] The heat shield may comprise a heat resistant material such as a ceramic or a less sensitive plastic material.

[0020] Additionally, the capacitor may include a heat sink disposed under the capacitance element, for example, between the capacitance element and the connection side of the terminal. The heat sink can be used to concentrate heat entering the capacitor, such that the heat sink constitutes a sacrificial element for thermal protection of the more sensitive capacitance element.

[0021] The heat sink may comprise a material that has some thermal conductivity. In particular, the heat sink may comprise a material that has a large heat capacity.

[0022] Additionally, the heat sink may include a phase change material that has a phase change temperature below the degradation temperature of the dielectric material.

[0023] The phase change can be a reversible phase change or an irreversible phase change when the component is used only once in the SMT process.

[0024] The first terminal and the second terminal may have a vertical length of 1 mm or more.

[0025] Longer lengths are preferred because they reduce the thermal conductivity of the terminals and improve thermal protection of the capacitance elements within the capacitor.

[0026] The capacitor may include a housing in which a wound capacitance element is disposed.

[0027] The housing may include an inner wall and an outer wall, the inner wall and the outer wall being separated by a gap. Thus, the housing may be a double-walled case. Specifically, each of the walls of the housing may be double-walled, i.e., formed by an inner wall and an outer wall separated by a gap.

[0028] Because the housing includes an inner wall and an outer wall separated by a gap, the housing provides high thermal insulation for a capacitance element disposed within the housing. The gap between the inner and outer walls can act as a heat sink element, absorbing heat entering the housing from the outside and preventing the capacitance element from reaching a critical temperature, at least temporarily, for the duration of the reflow process.

[0029] Preferably, the gap is filled with air or other thermally insulating material.

[0030] The housing may comprise a plastic material that is not very sensitive to heat. Preferably, the housing material has a low thermal conductivity.

[0031] Additionally, the capacitor may further include a filler within the housing, the filler within the housing may be positioned such that the capacitance element is disposed within the filler.

[0032] The thermal expansion coefficients of the materials of the housing, filler and capacitance element are preferably sufficiently similar so that thermal stresses during temperature changes are reduced.

[0033] The filler material may include or consist of an epoxy resin.

[0034] Filler materials can be used to eliminate potential spaces where air and / or moisture can be stored within the capacitor, thus allowing the capacitor to be essentially free of air and / or moisture.

[0035] The complete absence or essentially complete absence of air or moisture improves the capacitor's thermal response behavior, especially during SMT processes such as reflow heating.

[0036] The capacitors may be usable in pick and place machines.

[0037] Such a pick and place machine can be used in an SMT process to place the capacitor in the correct position and in the correct orientation on a carrier in the external circuit environment.

[0038] Furthermore, a DC link component may include one or several such capacitors. A DC link component may be used to electrically and mechanically connect a switching device from a mains power supply to a DC power source, such as a battery or rectified source. An EMI component may include one or several such capacitors to connect an AC input from or an AC output to a mains power supply with a power converter.

[0039] In DC link components, capacitors can be used as part of electromagnetic interference reduction circuits, specifically as capacitance elements in resonant circuits, anti-resonant circuits or filters.

[0040] The capacitor may be provided and adapted to operate at an operating voltage in the range of 600 V DC or greater, or 100 VAC AC or greater. The capacitor housing may have a cuboid shape having a length, width, and height. The length may be between 18 mm and 100 mm, e.g., 31.5 mm. The height of the housing may be between 10 and 100 mm, e.g., 40 mm. The vertical height of the terminal may be between 1 mm and 5 mm, e.g., 2 mm. The width of the housing may be between 20 mm and 100 mm, e.g., 28.5 mm. The length of the terminal in the horizontal direction (x, y) may be between 10 mm and 30 mm, e.g., 20 mm. The corresponding width of the connecting surface of the terminal in the corresponding orthogonal horizontal direction may be between 5 mm and 8 mm, e.g., 6.5 mm.

[0041] A method for manufacturing a capacitor as described above, comprising: providing a material for a first electrode, a material for a second electrode, and a material for a dielectric; providing a housing; winding a material for the first electrode, a material for the second electrode, and a material for the dielectric to obtain a wound capacitance element; connecting electrodes of the capacitance element to surface mount terminals; and disposing a capacitance element within the housing.

[0042] Additionally, the method may include annealing the capacitor.

[0043] Annealing can provide the increased thermal resistance necessary to meet SMT process requirements.

[0044] In particular, annealing can be used to prepare the dielectric material, for example, to shrink the thickness of the dielectric material.

[0045] Additionally, annealing can be used to increase the removal of air and / or moisture within the capacitor housing.

[0046] Additionally, the method may include filling the corresponding remaining volume within the housing with a filler material—to push out the air and / or moisture—to remove the air and / or moisture.

[0047] Such capacitors can be used in EMI reduction circuits, for example resonant circuits, mutually resonant circuits or filters.

[0048] In particular, the capacitor can be used in a DC link circuit.

[0049] It is possible to use the capacitor for voltages up to 630V or above or 100Vac or above, especially 100Vac.

[0050] Key aspects and details of the preferred embodiment are illustrated in the accompanying schematic drawings. [Brief explanation of the drawings]

[0051] [Figure 1] The basic structure for improving heat resistance is shown below. [Figure 2] The basic structure for improving heat resistance is shown below. [Figure 3] The basic structure for improving heat resistance is shown below. [Figure 4] The basic structure for improving heat resistance is shown below. [Figure 5] 1 shows cross sections of a capacitor viewed from different directions. [Figure 6] 1 shows cross sections of a capacitor viewed from different directions. [Figure 7] 1 shows cross sections of a capacitor viewed from different directions. [Figure 8] FIG. 1 shows a perspective view of a capacitor. [Figure 9]A perspective view of the capacitor housing H is shown. DETAILED DESCRIPTION OF THE INVENTION

[0052] FIG. 1 shows details of the capacitor C. The capacitor C includes a housing H and a capacitance element CE. Furthermore, the capacitor C includes a first terminal T1 and a second terminal T2. The capacitance element CE includes a wound sheet material of electrodes electrically connected to the two terminals T1 and T2, and a dielectric material disposed between the two electrodes. Furthermore, the two terminals T1 and T2 have a flat bottom side (FBS). Via the flat bottom side, the capacitor C is surface-mountable and thus can be used in a pick-and-place machine and electrically and mechanically connected to corresponding solder pads on an external circuit environment, for example, a carrier of a DC link component.

[0053] Increasing the vertical height of the two terminals T1, T2, i.e., increasing the length of the terminals in the vertical direction z, increases the thermal barrier between the connection side FBS of the terminals and the sensing capacitance element CE.

[0054] 2 further shows the possibility of providing a heat shield HSH arranged vertically - below the capacitance element CE - so that the heat shield HSH is arranged between the capacitance element CE and the flat bottom side of the terminal.

[0055] An additional heat shield may be arranged surrounding the housing H and having a gap of at least 1 mm, for example between 2 mm and 5 mm.

[0056] Furthermore, FIG. 3 shows the possibility of placing a heat sink HSN in the vertical direction z below the capacitance element CE. The heat sink HSN can be thermally coupled to the terminals. Due to their conductive nature, the terminals can create an undesirable heat conduction path from the outside of the housing to the capacitance element CE, but the low thermal conductivity of the terminals is desirable. The heat sink HSN can then act as a heat absorption element that absorbs heat entering the housing from the outside and prevents the capacitance element CE from reaching a critical temperature, at least temporarily, over the duration of the reflow process.

[0057] Furthermore, FIG. 4 shows the combined application of the heat shield HSH and the heat sink HSN.

[0058] Furthermore, FIG. 4 shows the possibility of filling the remaining volume of the housing H with a filler material F in order to avoid or reduce the amount of air or moisture inside the housing H. Of course, it is preferable for a capacitor to have compact dimensions. Therefore, the volume of the capacitor C that does not contribute to the capacitance should be as small as possible. Accordingly, a corresponding optimized ratio should be obtained between the volume of the capacitance element CE and the volume of the space filled with the filler material. However, the provision of the filler material F can further thermally decouple the capacitance element CE from the outside of the capacitor C and increase—at least temporarily—the heat resistance of the capacitor C.

[0059] 5 is a cross section in a view parallel to the horizontal direction y of the capacitor C. The terminal T is electrically and mechanically connected at a location within the housing H and includes two legs that are electrically and mechanically connected at the bottom side, specifically the flat bottom side FBS, making the capacitor C compatible with SMT processes.

[0060] 6 shows a cross section parallel to the horizontal direction x. In this figure, the terminals T1 and T2 are L-shaped.

[0061] 5 and 6 clearly show that the position of the capacitance element CE within the housing H is off-center. Specifically, the center of the capacitance element CE is located higher compared to the center of the housing H of the capacitor C. Thus, the length of the terminal T is increased, and the thermal resistance to the flat bottom side is also increased.

[0062] Figure 6 shows a bottom view of capacitor C. This means that the perspective is on the flat bottom FBS, which can be thought of as including a rectangular shape and two additional smaller rectangles attached to the distal ends of the main rectangular patch of terminal T.

[0063] FIG. 8 shows a perspective view of the capacitor C. The width W in the horizontal direction can be 28.5 mm. The length in the horizontal direction y can be 31.5 mm. The vertical height of the housing H can be 13 mm. The total height of the capacitor C, including the vertical dimensions of the terminals H, can be 15 mm. The horizontal extension in the y direction can be b=6.5 mm. The horizontal extension of the terminals in the x direction, in particular on the flat bottom sides of the terminals, can be a=20 mm. The distance P between the two terminals can be 27.5 mm.

[0064] With the dimensions of capacitor C shown in FIG. 8, the capacitance can be up to 1.1 μF at an operating voltage of 630 Vdc or 305 Vac with dimensions width=28.5 mm, height=15 mm and length=31.5 mm.

[0065] FIG. 9 is a perspective view of the housing H of the capacitor. The housing H is a double-walled case. The housing H includes an inner wall IW and an outer wall OW. The inner wall IW faces toward the cavity enclosed by the housing H and in which the capacitance element CE is disposed. The outer wall OW faces away from the cavity enclosed by the housing H. The inner wall IW and the outer wall OW do not abut each other. Instead, the inner wall IW and the outer wall OW are separated by a gap G. The gap G may be filled with air or another thermally insulating material.

[0066] The housing H is a double-walled case, which provides very high thermal insulation of the capacitance element CE from the environment of the housing H.

[0067] The capacitor and its method and application (use) are not limited to the above-mentioned characteristics. The capacitor can include additional elements, such as a temperature sensor, a heat shield, or a mechanical or electrical protection element to protect the capacitor from overvoltage. The terminals, especially the flat bottom side of the terminals, can include additional materials, such as solder, to enhance the soldering process. Applications other than EMI reduction or DC link components are also possible. Specifically, the capacitor can be used as a short-term energy storage.

[0068] Additionally, capacitors can be used with corresponding capacitors to build capacitor arrays for increased capacitance or increased voltage resistance. Capacitors can then be arranged in series or parallel connections or both. [Explanation of symbols]

[0069] C Capacitor H Housing CE (capacitance element) T1, T2, T3 terminals RBS Flat bottom side of a terminal HSH heat shield HSN heat sink x, y horizontal directions z vertical direction F. Filler IW inner wall OW outer wall G gap

Claims

1. a first electrode, a second electrode, and a dielectric disposed between the first electrode and the second electrode; a first terminal electrically connected to the first electrode; a second terminal electrically connected to the second electrode; A capacitor, the material for the first electrode, the material for the second electrode, and the material for the dielectric constitute a wound capacitance element; the first terminal and the second terminal are surface mount terminals; the capacitor further includes a heat sink disposed below the capacitance element and / or a heat sink disposed between the capacitance element and connection sides of the first and second terminals. Capacitor.

2. 10. The capacitor of claim 1 having a capacitance greater than 1.0 μF.

3. 10. The capacitor of claim 1, wherein the first terminal and the second terminal comprise a material selected from steel, copper, brass, aluminum, tin, or a coating having a tin alloy.

4. 2. The capacitor of claim 1, wherein the material for the dielectric is selected from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PPS (polypropylene sulfide), PTFE (polytetrafluoroethylene), PS (polystyrene), PC (polycarbonate), and PET HT.

5. The capacitor of claim 1 further comprising a heat shield disposed below the capacitance element.

6. The capacitor of claim 1 , wherein the first terminal and the second terminal have a length greater than 1 mm in a vertical direction.

7. The capacitor of claim 1 including a housing in which the wound capacitance element is disposed.

8. The capacitor of claim 7 , wherein the housing includes an inner wall and an outer wall, the inner wall and the outer wall being separated by a gap.

9. The capacitor of claim 8 , wherein the gap is filled with air or another insulating material.

10. The capacitor of claim 7 further comprising a filler material within the housing such that the capacitance element is disposed within the filler material.

11. The capacitor of claim 10 , wherein the filler material comprises an epoxy resin.

12. The capacitor of claim 1 , wherein the capacitor is essentially free of air and / or moisture.

13. 10. The capacitor of claim 1, which is usable with a pick and place machine.

14. 10. A method for manufacturing the capacitor of claim 1, comprising: providing a material for the first electrode, a material for the second electrode, and a material for the dielectric; providing a first surface mount terminal and a second surface mount terminal; providing a housing; - winding the material for the first electrode, the material for the second electrode and the material for the dielectric to obtain a wound capacitance element; connecting the first and second electrodes of the capacitance element to the first and second surface mount terminals; and disposing the capacitance element within the housing. method.

15. The method of claim 14 further comprising the step of annealing the capacitor.

16. 15. The method of claim 14, further comprising filling the remaining volume within the housing with a filler material to remove air and / or moisture.

17. 10. Use of the capacitor of claim 1 in an EMI reduction circuit.

18. 18. Use according to claim 17 in a DC link circuit.

19. 18. Use according to claim 17 for voltages of 630 V and above.

20. 18. Use according to claim 17 in an EMI filter circuit.

21. 18. Use according to claim 17 for AC voltages of 100 Vac or more.

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