WO2013062484A1

WO2013062484A1 - Electrolytic capacitor

Info

Publication number: WO2013062484A1
Application number: PCT/SG2012/000294
Authority: WO
Inventors: Iwan ELIA; Hooi Yong Chng
Original assignee: Xenon Technologies Pte Ltd
Priority date: 2011-10-25
Filing date: 2012-08-21
Publication date: 2013-05-02

Abstract

The present application discloses an electrolytic capacitor for a portable electronic device. The electrolytic capacitor comprises a cathode foil for connecting to a cathode lead of the electrolytic capacitor and the cathode foil is folded with a plurality of layers. The electrolytic capacitor further comprises an anode foil for connecting to an anode lead of the electrolytic capacitor and a casing for enclosing both the cathode foil and the anode foil. The electrolytic capacitor also comprises an electrolyte contained by the casing. Two neighboring layers of the plurality of layers of the cathode foil form a pocket for receiving the anode foil in-between.

Description

ELECTROLYTIC CAPACITOR

FIELD OF THE INVENTION

[0001] The present application relates to an electrolytic capacitor for portable electronic devices. It also relates to a method of making the electrolytic capacitor.

BACKGROUND OF THE INVENTION

[0002] An electrolytic capacitor is a type of capacitor that uses an electrolyte, an ionic conducting liquid, as one of its electrode, to achieve a large capacitance per unit volume for storing or releasing electric current or electric charge. In a portable electronic device, the electrolytic capacitor is used for making a xenon flash module, which is an electronic circuit including a xenon flash lamp and some electronic components on a Printed Circuit Board (PCB).

[0003] The electronic components are desired to be small so that they can be encased by the portable electronic device neatly. However, the electrolytic capacitor, which is a key component of the xenon flash module, typically has a cylindrical profile with a diameter of more than 5 millimeter (mm). Hence, the typical electrolytic capacitor hinders the adoption of the xenon flash module by the portable electronic device, which is often compact or pocket-sized. Therefore, there is a need for an electrolytic capacitor small enough to fit inside a portable electronic device.

SUMMARY OF THE INVENTION

[0004] Present inventions are defined by independent claims. Preferred features or elements are defined by dependent claims. The present inventions aim to provide new and useful devices and methods.

[0005] According to a first aspect of the present invention, there is provided an electrolytic capacitor for a portable electronic device comprising a cathode foil for connecting to a cathode lead, the cathode foil being folded with a plurality of layers, an anode foil for connecting to an anode lead, an electrolyte, a casing for containing the cathode foil, the anode foil and the electrolyte, wherein two neighboring layers of the plurality of layers of the cathode foil form a pocket for receiving the anode foil in- between.

[0006] Preferably, the electrolytic capacitor further includes a top spacer and a bottom spacer that sandwich the cathode foil between the top spacer and the bottom spacer for connecting to the cathode lead.

[0007] Preferably, the cathode foil is folded in a zigzag pattern to form several pockets for receiving a plurality of anode foils respectively.

[0008] Preferably, the anode foil is made of aluminum material.

[0009] Preferably, the anode foil comprises at least one anode layer.

[0010] Preferably, one or more of the at least one anode layer is etched with through holes.

[0011] Preferably, the anode foil comprises two anode layers, one of the anode layer is etched with through holes and the other anode layer is etched with blind holes.

[0012] Preferably, both the cathode foil and the anode foil are rectangular shape such that they can be packed together for fitting into the casing.

[0013] Preferably, the casing has a regular shape or a combination of regular shapes.

[0014] Preferably, the electrolytic capacitor further includes a stopper for sealing the cathode foil, the anode foil and the electrolyte inside the casing for force fitting.

[0015] Preferably, the electrolytic capacitor comprises a valve for injecting the electrolyte into the casing or for releasing gas out of the casing. [0016] Preferably, the casing is made of aluminum material.

[0017] Preferably, at least a part of the casing is flexible.

[0018] Preferably, the part of the casing comprises an aluminum packaging foil material.

[0019] According to a second aspect of the present invention, there is provided a method of making an electrolytic capacitor comprising providing a cathode foil and an anode foil, folding the cathode foil to form a pocket, inserting the anode foil into the pocket, and encasing both the cathode foil and the anode foil.

[0020] Preferably, the encasing comprises applying an adhesive to a stopper for sealing a casing of the electrolytic capacitor.

[0021] Preferably, the encasing further comprises force fitting the stopper into the casing of the electrolytic capacitor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying figures (Figs.) illustrate embodiments and serve to explain principles of the disclosed embodiments. It is to be understood, however, that these figures are presented for purposes of illustration only, and not for defining limits of relevant inventions.

[0023] Fig. 1 shows an electrolytic capacitor that is partially exposed;

[0024] Fig. 2 shows an exploded view of the electrolytic capacitor;

[0025] Fig. 3 shows a cross section view of the electrolytic capacitor, which is taken along line A-A in Fig. 1 ;

[0026] Fig. 4 shows an anode element with an anode tab attached; [0027] Fig. 5 shows an oblique view of the anode element with two anode layers;

[0028] Fig. 6 shows a cathode element consisting of a cathode foil and two paper spacers;

[0029] Fig. 7 shows a rubber stopper;

[0030] Fig. 8 shows a casing that is made of aluminum material;

[0031] Fig. 9 shows a capacitor element comprising the cathode element and the anode element;

[0032] Fig. 10 shows a fabrication process for making the electrolytic capacitor; [0033] Fig. 11 shows a flat electrolytic capacitor that is partially exposed; [0034] Fig. 12 shows a circular shaped electrolytic capacitor; [0035] Fig. 13 shows an U-shaped electrolytic capacitor; and [0036] Fig. 14 shows a L-shaped electrolytic capacitor.

[0037] Exemplary, non-limiting embodiments of the present invention will now be described with references to the above-mentioned figures.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention relates to an electrolytic capacitor for portable electronic devices along with a method of making the electrolytic capacitor. [0039] According to an embodiment of the present invention, there is provided an electrolytic capacitor for a portable electronic device. The portable electronic device can be a mobile phone, a digital camera, a tablet personal computer or any other electronic apparatus for being carried around in a pocket or a handbag. The electrolytic capacitor comprises a cathode foil for connecting to a cathode lead of the electrolytic capacitor. The cathode foil is folded multiple times in forming a plurality of layers such that these layers can be packed together. In other words, these layers can be stacked on top of each other such that neighbouring layers of the cathode foil face each other. When folded, the cathode foil resembles a thin slab. The electrolytic capacitor further comprises an anode foil for connecting to an anode lead of the electrolytic capacitor. The anode lead and the cathode lead provide electrical connections to the electrolytic capacitor. A casing is made available to the electrolytic capacitor for housing both the cathode foil and the anode foil together inside the casing. The casing also keeps an electrolyte of the electrolytic capacitor inside the casing such that both the anode foil and the cathode foil are covered by the electrolyte for storing electric charge. The electrolyte in a liquid form is often preferred because the electrolyte liquid can permeate over the cathode foil and anode foil for better performance. In particular, the cathode foil is folded at least once in providing two layers. The two layers consists of a first cathode foil layer and a second cathode foil layer that are neighbouring and connected to each other at a folding edge. A pocket or receptacle is formed between the two neighbouring layers. The anode foil is inserted into the pocket such that the first cathode foil layer, the anode foil and the second cathode foil layer are sequentially sandwiched together.

[0040] Since the cathode foil is folded such that the cathode foil and the anode foil are collated tightly together, instead of rolled up in a cylindrical pattern, the electrolytic capacitor can be made in a thin cuboid form. The electrolytic capacitor is thus made more compact by having a thin plate pattern. Electrical storage capacity of the electrolytic capacitor is not compromised by the reduction in size because both the cathode foil and the anode foil can have large flat footprints or extended level areas for providing sufficient surface for electrodes of opposite charges. The thin electrolytic capacitor can be easily enclosed by a housing of a compact mobile phone such that the mobile phone can provide satisfactory flash photography experience based on the thin electrolytic capacitor. [0041] The electrolytic capacitor further comprises a top spacer and a bottom spacer that sandwich the cathode foil between the two spacers. The two spacers are often made with similar materials with low cost, such as paper. Paper spacers can be soaked with the electrolytic liquid for covering both the anode foil and the cathode foil. Performance (e.g. capacitance) of the electrolytic capacitor can be greatly enhanced when both the cathode foil and the anode foil are substantially immersed by the electrolyte liquid.

[0042] The cathode foil is folded in a zigzag pattern to form multiple pockets for housing many anode foils respectively. Each of these anode foils can be similar such that every pocket formed by neighboring layers of the cathode foil can be inserted with one of these anode foils. All of the anode foils can be attached to a tab for linking to the anode lead, whilst cathode foil can be joined to the cathode lead. The numerous anode foils may also be termed as a single anode foil because they are electrically connected together by the tab. Since almost an entire footprint or expanded surface area of both the cathode foil and the anode foils face each other respectively due to the folding structure, the electrolytic capacitor can have large capacitance with a slim profile.

[0043] The anode foil can comprise one or more anode layers that are attached together. For example, the anode foil can comprise two anode layers of etched aluminum sheet material that are cold welded together to the tab. Since each of the anode layers are etched with numerous holes on its surfaces, effective plate areas for storing electric charges are expanded. Similarly, the cathode foil can also comprise multiple cathode layers that are electrically connected to the cathode lead.

[0044] Both the cathode foil and the anode foil can be wrapped together by a bonding tape for forming a subassembly in order to be inserted into the casing. In the electrolytic capacitor, the cathode foil, the anode foil and a bonding tape are collectively known as a capacitor element. The capacitor element further comprises the cathode lead, the paper spacers and the anode tabs. The subassembly can be easily handled when bundled together. [0045] The anode foil or the cathode foil can be made of metal covered with metal oxide having high dielectric constants. Examples of the anode materials are aluminum, tantalum and niobium. Aluminum is often used because of its low cost and ease of processing.

[0046] All the anode layers of a single anode foil in a pocket can be etched with through holes. Alternatively, for a single anode foil with two or more anode layers, at least one of the anode layers of the single anode foil in the pocket can have through holes. In fact, the anode foil inside one of the pockets of the cathode foil can have two layers of etched aluminum materials with dissimilar structures. For example, for a single anode foil with two anode layers, one of the anode layers can be etched with blind holes and the other anode layer can be etched with through holes.

[0047] The anode element can comprise of either a single layer of anode foil or a multi-layer of anode foils that stacked together. In a multi-layer structure, all anode foils are electrically interconnected. Generally, a multi-layer anode foil will provide higher capacitance as compared to that of a single-layer anode foil.

[0048] One or more of the cathode foil and the anode foil can be made with rectangular shape or footprint for neatly fitting into a cuboid casing. In fact, both the cathode element and the anode elements can be rectangular shape such that they can be packed together for being inserted into a cuboid shaped casing. The cuboid casing can have a thickness smaller than a diameter of the known cylindrical electrolytic, such as less than 5mm.

[0049] The electrolytic capacitor or the casing may have a regular shape or a combination of regular shapes. For example, the electrolytic capacitor can be circular shaped, L-shaped, U-shaped or in combination of these regular shapes. These shapes are easily adapted for fitting into a housing of portable or pocketable electronic device.

[0050] The electrolytic capacitor can also comprise a stopper for sealing the cathode foil, the anode foil and the electrolyte inside the casing. The stopper can either be attached to an opening of the casing by adhesive or by force fitting. One example of the adhesive is known as epoxy.

[0051] The electrolytic capacitor can comprise a valve for injecting electrolyte into the casing or for releasing gas out of the casing. The valve can be provided on the stopper, the casing or other suitable places of the electrolytic capacitor. Elements or components of the electrolytic capacitor are enclosed inside the casing before they are filled with the electrolyte. The valve can be made as an orifice on the rubber stopper for injecting electrolyte fluid into the casing. The orifice can also be a relief valve of the electrolytic capacitor because hydrogen gas generated inside the casing can be discharged through valve automatically when exceeding a predetermined limit. For example, the hydrogen gas is generated inside the electrolytic capacitor during an aging test before product release. The valve can also be made on the casing if not on the stopper.

[0052] The casing can be made with either plastic material or aluminum material. The casing of plastic material can be easily injection molded at low cost. The casing of aluminum material can withstand high impact and internal pressure such that the electrolytic capacitor's life is extended. When in use, aluminum material of the cathode foil or anode foil can react with the electrolyte for generating hydrogen gas such that the casing is subjected to high pressure. A strong casing, such as made by aluminum, can endure the high pressure due to its robustness.

[0053] One or more parts of the casing can be made flexible. In other words, the casing can partially or completely change its shape or profile without causing damage to the electrolytic capacitor. Having the flexible casing also makes it easier for assembling the electrolytic capacitor element into the casing. Adopting the flexible casing can further avoid high tooling cost when adjustments of external dimensions to the electrolytic capacitor are required.

[0054] In practice, the flexible part of the casing can be made of aluminum packaging foil material for making the casing formable. Since aluminum foils of various thicknesses are abundantly available at low cost, the electrolytic capacitor with the flexible casing can be cost effectively produced for mass production. Besides, since the technology of making a flexible casing by using the aluminum foil is well developed, the electrolytic capacitor with the flexible casing can be made robust in structure and reliable in long-term performance. Alternatively, the flexible casing can be made with composite material.

[0055] According to another embodiment of the invention, the present application provides method of making an electrolytic capacitor that comprises a step of providing a cathode element, a step of folding the cathode element to form a pocket, a step of inserting anode elements into the pocket, and step of encasing the cathode element and the anode elements. The method is simple and provides a reliable, cost-effective and low profile electrolytic capacitor.

[0056] The step of encasing can comprise a step of applying an adhesive to a stopper for sealing a casing of the electrolytic capacitor. The adhesive is able to hermetically seal the electrolytic capacitor for long term usage.

[0057] The step of encasing can further comprise a step of force fitting the stopper into the casing of the electrolytic capacitor. The force fitting is also known as interference fitting such that the adhesive may be avoided.

[0058] Exemplary non-limiting embodiments of the present invention will now be described with reference to the figures.

[0059] Figs. 1 to 10 relate to a first embodiment of the present invention. In particular, Fig. 1 illustrates shows an electrolytic capacitor 32 that is partially exposed. The electrolytic capacitor 32 comprises an aluminum casing 34, a capacitor element 36 and a rubber stopper 38 and electrolyte liquid 74 (not shown in Fig. 1). The capacitor element 36 is sealed inside the casing 34 by the rubber stopper 38, which locates at an opening end 40 of the casing 34. Two electrode leads 42, 44 of the capacitor element 36 pass through and extend beyond the rubber stopper 38 such that a longer metal pin serves as an anode lead 42 of the electrolytic capacitor 32 and a shorter pin serves as a cathode lead 44 of the electrolytic capacitor 32. The rubber stopper 38 has an orifice 46 and the rubber stopper 38 is further sealed to the opening end 40 by an adhesive (not shown). The casing 34 is partially cut off such that internal structure of the electrolytic capacitor 32 is exposed for illustration.

[0060] Fig. 2 shows an exploded view of the electrolytic capacitor 32. In the exploded view, the capacitor element 36 is removed from the casing 34 such that components of the capacitor element 36 are expanded for viewing. According to Fig. 2, the capacitor element 36 comprises a cathode element 37, four anode elements 56, 58, 60, 62 and a bonding tape (not shown) for binding the cathode element 37 and the anode elements 56, 58, 60, 62 together.

[0061] The cathode element 37 comprises a top spacer 50, a cathode foil 52, a bottom spacer 54 and the cathode lead 44. The top spacer 50, the cathode foil 52 and the bottom spacer 54 are closely attached to each other and further folded together by four times to form four pockets 57, 59, 61 , 63 for receiving the four anode elements 56, 58, 60, 62 respectively. In particular, the cathode foil 52 is sandwiched between the top spacer 50 and the bottom spacer 54 such that they are further folded in a zigzag formation together. At every fold, neighbouring layers of the bottom spacer 54 or neighbouring layers of the top spacer 50 form one of the pockets 57, 59, 61 , 63 for receiving one of the anode elements 56, 58, 60, 62. In detail, a first pocket 57 is formed between two neighbouring layers of the bottom spacer 54, which opens towards right in Fig. 2. A second pocket 59 is formed between two neighbouring layers of the top spacer 50 below the first pocket 57, and the second pocket 59 opens towards left. A third pocket 61 is formed between two neighbouring layers of the bottom spacer 54 again, which opens towards right. The third pocket 61 is further below the second pocket 59 in Fig. 2. A fourth pocket 63 is formed between two neighbouring layers of the top spacer 50 again, which opens towards left. The fourth pocket 63 is located below all of the three pockets 57, 59, 61 in Fig. 2.

[0062] The four sets of anode elements 56, 58, 60, 62 comprise a first anode element 56, a second anode element 58, a third anode element 60, a fourth anode element 62 and the anode lead 42. Each of the anode element 56, 58, 60, 62 has an anode tab for providing electrical connection from the anode element 56, 58, 60, 62 to the anode lead 42. Specifically, the first anode element 56 has a first anode tab 66 extending from its corner, a second anode element 58 has a second anode tab 68 extending at its corner, a third anode element 60 has a third anode tab 70 extending beyond its corner and a fourth element 62 has a fourth anode tab 72 extending from its corner. All these anode tabs 66, 68, 70, 72 are located close to the anode lead 42 and further electrically connected to the anode lead 42, although Fig. 2 does not explicitly show the physical proximity and linkages. In contrast, the two spacers 50, 54 and the cathode foil 52 are electrically connected to the cathode lead 44, despite not being depicted in Fig. 2. Electrolyte (electrolytic liquid) 74 is also not depicted in Fig. 2 for the purpose of simplification. In fact, the capacitor element 36 is fully immersed by the electrolyte fluid 74 inside the casing 34 after being assembled such that the two spacers 50, 54 are fully soaked with the electrolyte fluid 74.

[0063] The four anode elements 56, 58, 60, 62 have similar structures such that the first anode element 56 is used as an example for explanation. In particular, the first anode element 56 consists of two sheet materials 76, 78, which are a first top anode layer 76 and a first bottom anode layer 78. Both the first top anode layer 76 and the first bottom anode layer 78 are etched with porous surfaces.

[0064] Fig. 3 shows a cross section view of the electrolytic capacitor 32, which is taken along line A-A in Fig. 1.The capacitor element 36 is enclosed by the aluminum casing 34 according to Fig. 3. In the assembled form as shown in Fig. 3, the top spacer 50, the cathode foil 52 and the bottom spacer 54 are folded in a zigzag pattern such that the four anode elements 56, 58, 60, 62 are enclosed by the four pockets 57, 59, 61 , 63. Since the top spacer 50, the cathode foil 52 and the bottom spacer 54 has substantially the same size and are packed closely against each other, the four anode elements 56, 58, 60, 62 are also squeezed against the top spacer 50, the cathode foil 52 and the bottom spacer 54. Components of the electrolytic capacitor 32 are immersed in the electrolyte liquid 74 that is contained by the aluminum casing 34.

[0065] Fig. 4 shows the first anode element 56 with the first anode tab 66 attached. Structures of the other anode elements 58, 60, 62 with other anode tabs 68, 70, 72 are similar to the first anode element 56 with the first anode tab 66. [0066] The first anode tab 66 is bonded to the first anode element 56 at a corner of the first anode element 56 for providing electrical connection to the anode lead 42. The two anode layers 76, 78 are stacked together with similar sizes. The two anode layers 76, 78 are bonded together by spot welding such that they are also electrically connected. Each of the anode layers 76, 78 is etched with numerous holes in their thickness directions such that effective surface areas on the anode layers 76, 78 are substantially increased. The etched anode layers 76, 78 have also been subjected to an oxidization forming process such that exposed surfaces of the anode layers 76. 78 are cover with dielectric films.

[0067] Fig. 5 shows an oblique view of the first anode element 56 with the two anode layers 76, 78. The first top anode layer 76 is flared open for showing two distinctive sheets of the anode layers 76, 78, although the two anode layers 76, 78 are closely attached together physically in a working electrolytic capacitor.

[0068] Fig. 6 shows the cathode element 37 that comprise the cathode foil 52, a top spacer 50 and a bottom spacer 54. The top spacer 50, the cathode foil 52 and the bottom spacer 54 are sequentially attached together and folded in a zigzag form. The two spacers 50, 54 are made of paper for soaking with the electrolyte liquid 74. The cathode foil 52 and the two spacers 50, 54 are in the forms of elongated rectangular strips and conform to each other.

[0069] Fig. 7 shows the rubber stopper 38 that is positioned at the opening end 40 of the electrolytic capacitor 32. The rubber stopper 38 has an orifice 46 at its bottom end 82. A cross-section of the rubber stopper 38 along a line B-B can show a rectangular shape with its corners round-off. The orifice 46 serves as a valve for injecting the electrolyte liquid 74 into the aluminum casing 34. The orifice 46 can also be used for discharging gas when high pressure is built inside the aluminum casing 34 during an aging test. When in use, hydrogen gas can be generated if the electrolyte liquid 74 meets aluminum. The orifice 46 is sealed to the aluminum casing 34 by an adhesive (not shown) after the aging test.

[0070] Fig. 8 shows the casing 34 that is made of aluminum material. The casing 34 resembles a cuboid box with the opening end 40 at its bottom (end) 84. A cross-section taken along line C-C also will present a substantially rectangular profile that compliments to the profile along the line B-B of the rubber stopper 38 (see Fig: 7).

[0071] Fig. 9 shows the capacitor element 36 that comprises the cathode element 37 and the anode elements 56, 58, 60, 62. The four anode elements 56, 58, 60, 62 may collectively be known as an anode element 64. The capacitor element 36 in Fig. 9 depicts assembled components without the aluminum casing 34 or the rubber stopper 38. The top spacer 50, the cathode foil 52, the bottom spacer 54 and the anode elements 56, 58, 60, 62 are wrapped together by a bonding tape 86 for inserting into the aluminum casing 34. The cathode foil 52 is connected to the cathode lead 44, whilst the anode elements 56, 58, 60, 62 are connected to the anode lead 42 together via their tabs 66, 68, 70, 72.

[0072] Fig. 10 shows a fabrication process 94 for making the electrolytic capacitor 32. Some important steps of the fabrication process 94 are listed in a flow chart of Fig. 10. The fabrication process 94 starts with a first step 96 of providing materials of the electrolytic capacitor 32, which include the cathode aluminum foil 52, the top paper spacer 50, the bottom paper spacer 54 and long strips of acid etched aluminum foil. Other components of the electrolytic capacitor 32, such as the casing 34, the rubber stopper 38 and the electrolyte fluid 74, are also made available at the first step 96.

[0073] In a second step 98, the long strips of acid etched aluminum foil, the cathode aluminum foil 52, the top paper spacer 50 and the bottom paper spacer 54 are cut to predetermined sizes for making the cathode element 37 and the anode elements 56, 58, 60, 62.

[0074] In a third step 106, the top paper spacer 50, the cathode aluminum foil 52 and the bottom paper spacer 54 are sequentially packed together and further folded in a zigzag form.

[0075] In a fourth step 108, the four anode elements 56, 58, 60, 62 are inserted into four pockets 57, 59, 61 , 63 of the folded cathode element 37 respectively. [0076] Afterwards, the anode elements 56, 58, 60, 62 and the cathode element 37 are packed and enveloped together by the binding tape 86 in a fifth step 114.

[0077] In a sixth step 116, the anode elements 56, 58, 60, 62 are connected together at their tabs 66, 68, 70, 72 which is further joined to the anode lead 42 for providing electrical connection.

[0078] Subsequently, the rubber stopper 38 is added such that the anode lead 42 and the cathode lead 44 are taken through holes (not shown) of the rubber stopper 38 in a seventh step 120. The capacitor element 36 is subsequently inserted into the aluminum casing 34 in an eighth step 122 and hermetically sealed with the rubber stopper 38 by an adhesive. The capacitor element 36 is applied with an impregnation process in a ninth step 126 such that the electrolytic liquid 74 is injected into the casing 34. The capacitor element 36 is immersed by the electrolyte liquid 74. Afterwards, the aluminum casing 34, the capacitor element 36, the rubber stopper 38 and the electrolyte liquid 74 are subjected to an aging process 128 in a tenth step.

[0079] The last eleventh step 130 is to seal the orifice 46 at the rubber stopper 38 to prevent leakage of electrolyte liquid 74.

[0080] Figs. 11 to 14 provide other embodiments of the invention. These embodiments provide alternative electrolytic capacitors whose external shapes are regular.

[0081] Fig. 11 shows a flat electrolytic capacitor 132 that is partially exposed. The flat electrolytic capacitor 132 has structure and components that are similar to those of the electrolytic capacitor 32. Description of the similar structure and components is hereby incorporated where appropriate. However, the flat electrolytic capacitor 132 has an aluminum casing 134 for enclosing the rubber stopper 38 by mechanical sealing. In particular, an opening end 40 of the aluminum casing 134 is crimped with a neck after receiving the rubber stopper 38 such that the aluminum casing 34 and the rubber stopper 38 form a force fitting or an interference fitting. Adhesive is avoided for providing the interference, which is airtight. [0082] Fig. 12 shows a circular shaped electrolytic capacitor 136. However, the circular shaped electrolytic capacitor 136 has edges or side surfaces 137, 139 that are straight on opposite sides. They include a first straight side 137 and a second straight side 139 that are symmetrical with respect to a centre line 141 of the circular shaped electrolytic capacitor 136. The circular shaped electrolytic capacitor 136 is useful for fitting closely to a rounded corner of a mobile phone casing.

[0083] Fig. 13 shows an U-shaped electrolytic capacitor 138. The U-shaped electrolytic capacitor 138 hides its anode lead 42 and cathode lead 44 within a footprint of the U-shaped electrolytic capacitor 138 such that the leads 42, 44 no longer protrude outside a casing of the U-shaped electrolytic capacitor 138 for presenting a compact projection or footprint.

[0084] Fig. 14 shows a L-shaped electrolytic capacitor 140. The L-shaped electrolytic capacitor 140 has a footprint of a rectangle with a recess. The L-shaped electrolytic capacitor 140 has a rectangular corner 142 for fitting into a corner of a mobile phone.

[0085] In the application, unless specified otherwise, the terms "comprising", "comprise", and grammatical variants thereof, intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, non-explicitly recited elements.

[0086] As used herein, the term "about", in the context of concentrations of components of the formulations, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically +/- 0.5% of the stated value.

[0087] Throughout this disclosure, certain embodiments may be disclosed in a range format. The description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1 , 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0088] It will be apparent that various other modifications and adaptations of the application will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the application and it is intended that all such modifications and adaptations come within the scope of the appended claims.

REFERENCE NUMBERALS

32 electrolytic capacitor

34 aluminum casing

36 capacitor element

37 cathode element

38 rubber stopper

40 opening end

42 anode lead

44 cathode lead

46 orifice

50 top spacer

52 cathode foil

54 bottom spacer

56 first anode element

57 first pocket

58 second anode element

59 second pocket

60 third anode element

61 third pocket

62 fourth anode element

63 fourth pocket anode element

first anode tab

second anode tab

third anode tab

fourth anode tab

electrolyte fluid

first top anode layer

first bottom anode layer

bottom end

bottom

bonding tape

fabrication process

first step

second step

third step

fourth step

fifth step

sixth step

seventh step

eighth step

ninth step

tenth step

eleventh step

flat electrolytic capacitor

aluminum casing

circular-shaped electrolytic capacitor first straight side

U-shaped electrolytic capacitor second straight side

L-shaped electrolytic capacitor centre line

rectangular corner

Claims

1. An electrolytic capacitor for a portable electronic device comprising:

a cathode foil for connecting to a cathode lead, the cathode foil being folded with a plurality of layers;

an anode foil for connecting to an anode lead;

an electrolyte,

a casing for containing the cathode foil, the anode foil and the electrolyte,

wherein two neighboring layers of the plurality of layers of the cathode foil form a pocket for receiving the anode foil in-between.

2. The electrolytic capacitor of claim 1 further comprising:

a top spacer and a bottom spacer that sandwich the cathode foil between the top spacer and the bottom spacer for connecting to the cathode lead.

3. The electrolytic capacitor of claim 1 or 2, wherein the cathode foil is folded in a zigzag pattern to form several pockets for receiving a plurality of anode foils respectively.

4. The electrolytic capacitor of any of the preceding claims, wherein the anode foil is made of aluminum material.

5. The electrolytic capacitor of any of the preceding claims, wherein the anode foil comprises at least one anode layer.

6. The electrolytic capacitor of claim 5, wherein one or more of the at least one anode layer is etched with through holes.

7. The electrolytic capacitor of any one of claims 1 to 4, wherein the anode foil comprises two anode layers, one of the anode layer is etched with through holes and the other anode layer is etched with blind holes.

8. The electrolytic capacitor of any of the preceding claims, wherein both the cathode foil and the anode foil are rectangular shape such that they can be packed together for fitting into the casing.

9. The electrolytic capacitor of any of the preceding claims, wherein the casing has a regular shape or a combination of regular shapes.

10. The electrolytic capacitor of any of the preceding claims further comprising a stopper for sealing the cathode foil, the anode foil and the electrolyte inside the casing for force fitting.

11. The electrolytic capacitor of any of the preceding claims, wherein the electrolytic capacitor comprises a valve for injecting the electrolyte into the casing or for releasing gas out of the casing.

12. The electrolytic capacitor of any of the preceding claims, wherein the casing is made of aluminum material.

13. The electrolytic capacitor of any of the preceding claims, wherein at least a part of the casing is flexible.

14. The electrolytic capacitor of claim 14, wherein the part of the casing comprises an aluminum packaging foil material.

15. A method of making an electrolytic capacitor comprising:

providing a cathode foil and an anode foil,

folding the cathode foil to form a pocket,

inserting the anode foil into the pocket, and

encasing both the cathode foil and the anode foil.

16. The method of claim 15, wherein the encasing comprises applying an adhesive to a stopper for sealing a casing of the electrolytic capacitor.

7. The method of claim 15 or claim 16, wherein the encasing further comprises force fitting the stopper into the casing of the electrolytic capacitor.