Capacitor, method for manufacturing capacitor, and use of capacitor

Abstract

An improved capacitor is provided that is of the wound category and is surface mountable to provide high capacitance in a compact form factor.

Description

[Technical field]

[0001] (Technical field) The present application refers to capacitors with improved properties, methods for manufacturing the capacitors, and specific usage 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 towards the system at the input or output. DC link capacitors, for example, electrically connect the switching devices of a vehicle to its DC electrical environment, for example 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 according to their structure. A capacitor can include a layer stack in which conductive and dielectric layers are stacked on top of each other. Another category of capacitors includes a material of electrodes and a dielectric material between two electrodes where the dielectric material is wound.

[0004] For a capacitor, it is generally preferred that the capacitor have a large capacitance, a small spatial dimension, be suitable for high voltage and high power applications, 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 terminals of the capacitor are placed in holes and soldered to the external circuit environment. Another category of connections is obtained via SMT (surface mount technology), in which the terminals of the electrical component are placed on a carrier and electrically and mechanically connected to contacts of the external circuit environment on the carrier surface. It is therefore desirable to have a compact capacitor offering the above-mentioned advantages of being surface mountable to the external circuit environment. In particular, it is preferable 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 construct 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 the carrier. To that end, the entire component is heated, for example in a reflow oven, to a temperature and for a duration such that reliable electrical and mechanical contact between the terminals and the connection pads of the carrier is established. In contrast to THT connections, where high temperatures are only necessary at the locations of the terminals for soldering, the corresponding high temperatures are applied to the electrical component as a whole. All elements and materials must therefore comply with the reflow requirements.

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

[0012] The capacitor can have a capacitance of 1 μF or more. Specifically, the capacitor can have a capacitance between 1.1 μF and 2.2 μF in a compact housing that can be processed in an SMT process.

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

[0014] The first terminal and the second terminal may include or be composed 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 can be compatible with SMT processes and provide reliable capacitors. The use of such materials is possible because an annealing process can be performed during manufacture to prepare the dielectric material for subsequent SMT process steps. Furthermore, possible shrinkage of the thickness of the dielectric material can be compensated for by providing a dielectric material having a thickness after SMT processing that is compatible with the requirements for high voltage applications, high power applications and high capacitance.

[0017] Additionally, 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 that is to be electrically connected to an external circuit element.

[0018] The heat shield can include a material having a low thermal conductivity. The heat shield can be used to protect the sensitive capacitance element of the capacitor, especially the heat sensitive dielectric material of the capacitance element, from heat entering the capacitor, especially via a path along the terminal when the terminal establishes a thermal bridge from the outside to the capacitance element. Thus, the heat shield can include small openings to guide the conductive elements of the terminals to electrically connect the capacitance element to the external circuit environment. However, additional heat radiated by the lower portion of the terminal 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 may be used to concentrate heat entering the capacitor such that the heat sink constitutes a sacrificial element for thermally protecting the more sensitive capacitance element.

[0021] The heat sink may include a material that has a certain degree of thermal conductivity. In particular, the heat sink may include a material that has a large thermal 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 greater.

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

[0026] The capacitor can 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., double-walled, 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 that absorbs heat entering the housing from the outside and prevents 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 may include or consist of an epoxy resin.

[0034] Filling 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 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 a pick and place machine.

[0037] Such a pick-and-place machine can be used in an SMT process to place the capacitor in the correct location and in the correct orientation on a carrier in an 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 source to a DC power source, such as a battery or a rectified source. An EMI component may include one or several such capacitors and connect an AC input from a mains power source or an AC output to a mains power source with a power converter.

[0039] In DC link components, capacitors can be used as part of an electromagnetic interference reduction circuit, in particular 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 600V or more for DC or 100VAC or more for AC. The housing of the capacitor may have a cuboid shape having a length, a width and a height. The length may be between 18mm and 100mm, for example 31.5mm. The height of the housing may be between 10 and 100mm, for example 40mm. The vertical height of the terminal may be between 1mm and 5mm, for example 2mm. The width of the housing may be between 20mm and 100mm, for example 28.5mm. The length of the terminal in a horizontal direction (x,y) may be between 10mm and 30mm, for example 20mm. The corresponding width of the connection surface of the terminal in the corresponding orthogonal horizontal direction may be between 5mm and 8mm, for example 6.5mm.

[0041] A method for manufacturing a capacitor as described above, comprising the steps of: 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 more or 100Vac or more, especially 100Vac.

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

[0051] [Figure 1] The basic structure for improving heat resistance is shown below. [Diagram 2] The basic structure for improving heat resistance is shown below. [Diagram 3] The basic structure for improving heat resistance is shown below. [Figure 4] The basic structure for improving heat resistance is shown below. [Diagram 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. [Figure 9]A perspective view of the capacitor housing H is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] FIG. 1 shows a detail of the capacitor C. The capacitor C comprises a housing H and a capacitance element CE. Furthermore, the capacitor C comprises a first terminal T1 and a second terminal T2. The capacitance element CE comprises a wound sheet material of electrodes electrically connected to the two terminals T1, T2, and a dielectric material arranged between the two electrodes. Furthermore, the two terminals T1, T2 have a flat bottom side FBS. Via the flat bottom side, the capacitor C is surface mountable and thus usable in a pick-and-place machine and connectable - electrically and mechanically - to corresponding solder pads of 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] Furthermore, figure 2 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 disposed 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 arranging 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 absorbing element that absorbs the heat entering the housing from the outside and prevents the capacitance element CE from reaching a critical temperature, at least temporarily, for the duration of the reflow process.

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

[0058] Furthermore, FIG. 4 shows the possibility of filling the remaining volume of the housing H with a filling material F in order to avoid or reduce the amount of air or moisture in the housing H. Of course, it is preferable for the capacitor to have compact dimensions. Thus, the volume of the capacitor C that does not contribute to the capacitance is preferably as small as possible. Correspondingly, a corresponding optimized ratio should be obtained for the volume of the capacitance element CE and the volume of the space filled with the filling material. However, the provision of the filling material F can further thermally separate 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 location of the capacitance element CE in 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] FIG. 6 shows a bottom view of the capacitor C. This means that the perspective is on the flat bottom FBS, which can be considered as including a rectangular shape and two additional smaller rectangles attached to the distal ends of the main rectangular patch of the 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 dimension 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 at the flat bottom side 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 with dimensions width=28.5 mm, height=15 mm and length=31.5 mm, at an operating voltage of 630 Vdc or 305 Vac.

[0065] 9 is a perspective view of a housing H of a 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 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 one another. 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 and therefore provides very high thermal insulation of the capacitance element CE from the environment of the housing H.

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

[0068] Additionally, capacitors can be used with corresponding capacitors to build a capacitor array 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 material 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; the first electrode material, the second electrode material, and the dielectric material constitute a wound capacitance element; the first terminal and the second terminal are surface mount terminals; Capacitor.

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

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

4. The capacitor of any one of claims 1 to 3, wherein the dielectric material 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 any one of claims 1 to 4, further comprising a heat shield disposed below the capacitance element.

6. The capacitor of any one of claims 1 to 5, further comprising a heat sink disposed below the capacitance element.

7. The capacitor of any one of claims 1 to 6, further comprising a heat sink disposed between the capacitance element and the connection side of the terminal.

8. The capacitor of any one of claims 1 to 7, wherein the first terminal and the second terminal have a length in a vertical direction greater than 1 mm.

9. A capacitor according to any one of claims 1 to 8, comprising a housing in which the wound capacitance element is disposed.

10. The capacitor of claim 9 comprising an inner wall and an outer wall, said inner wall and said outer wall being separated by a gap.

11. The capacitor of claim 10 , wherein the gap is filled with air or another insulating material.

12. The capacitor of any one of claims 9 to 11, further comprising a filler material within the housing such that the capacitance element is disposed in the filler material.

13. The capacitor of claim 12 , wherein the filler material comprises an epoxy resin.

14. A capacitor according to any preceding claim, wherein the capacitor is essentially free of air and / or moisture.

15. A capacitor according to any preceding claim, which is usable with a pick and place machine.

16. A method for producing a capacitor according to any one of claims 1 to 15, comprising the steps of: providing a material for the first electrode, a material for the second electrode, and a material for the dielectric; 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 electrodes of the capacitance element to the surface mount terminals; and disposing the capacitance element within the housing. method.

17. The method of claim 16 further comprising the step of annealing the capacitor.

18. 18. The method of claims 16 and 17, further comprising filling the remaining volume within the housing with a filler material to remove air and / or moisture.

19. Use of a capacitor according to any one of claims 1 to 16 in an EMI reduction circuit.

20. 20. Use according to claim 19 in a DC link circuit.

21. 21. Use according to any one of claims 19 and 20 for voltages of 630 V and above.

22. Use according to any one of claims 19 to 21 in an EMI filter circuit.

23. Use according to any one of claims 20 to 22 for AC voltages of 100 Vac or more.

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