US20070171599A1 - Solid electrolytic capacitor and method for manufacturing the same - Google Patents
Solid electrolytic capacitor and method for manufacturing the same Download PDFInfo
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- US20070171599A1 US20070171599A1 US11/657,695 US65769507A US2007171599A1 US 20070171599 A1 US20070171599 A1 US 20070171599A1 US 65769507 A US65769507 A US 65769507A US 2007171599 A1 US2007171599 A1 US 2007171599A1
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- Prior art keywords
- anode lead
- horizontal portion
- lead frame
- contact surface
- horizontal
- Prior art date
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- 239000003990 capacitor Substances 0.000 title claims abstract description 75
- 239000007787 solid Substances 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 title claims description 22
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- 238000003825 pressing Methods 0.000 claims description 19
- 230000002093 peripheral effect Effects 0.000 claims description 12
- 238000005452 bending Methods 0.000 claims description 10
- 229910052751 metal Inorganic materials 0.000 description 9
- 239000002184 metal Substances 0.000 description 9
- 238000003466 welding Methods 0.000 description 6
- 239000000470 constituent Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229920001940 conductive polymer Polymers 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 229920003002 synthetic resin Polymers 0.000 description 2
- 239000000057 synthetic resin Substances 0.000 description 2
- 229910052715 tantalum Inorganic materials 0.000 description 2
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 2
- NLZUEZXRPGMBCV-UHFFFAOYSA-N Butylhydroxytoluene Chemical compound CC1=CC(C(C)(C)C)=C(O)C(C(C)(C)C)=C1 NLZUEZXRPGMBCV-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 229920000767 polyaniline Polymers 0.000 description 1
- 229920000414 polyfuran Polymers 0.000 description 1
- 229920000128 polypyrrole Polymers 0.000 description 1
- 229920000123 polythiophene Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- PCCVSPMFGIFTHU-UHFFFAOYSA-N tetracyanoquinodimethane Chemical compound N#CC(C#N)=C1C=CC(=C(C#N)C#N)C=C1 PCCVSPMFGIFTHU-UHFFFAOYSA-N 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/008—Terminals
- H01G9/012—Terminals specially adapted for solid capacitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/04—Electrodes or formation of dielectric layers thereon
- H01G9/042—Electrodes or formation of dielectric layers thereon characterised by the material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/08—Housing; Encapsulation
- H01G9/10—Sealing, e.g. of lead-in wires
Definitions
- the present invention relates to a solid electrolytic capacitor that includes a lead frame, and a method for manufacturing the same.
- the solid electrolytic capacitor ( 1 ) includes a capacitor element ( 2 ) with a thin wire-like anode lead ( 20 ) protruding therefrom.
- An anode lead frame ( 3 ) is resistance welded to the anode lead ( 20 ), and a cathode lead frame ( 30 ) is attached to the peripheral surface of the capacitor element ( 2 ) by a conductive adhesive ( 26 ).
- the capacitor element ( 2 ) and base ends of both lead frames ( 3 ) and ( 30 ) are covered with a synthetic resin housing ( 5 ), while portions of the lead frames ( 3 ) and ( 30 ) that protrude outside the housing ( 5 ) are bent downward along the peripheral surface of the housing ( 5 ), and then horizontally along the base of the housing ( 5 ).
- the capacitor element ( 2 ) with the lead frames ( 3 ) and ( 30 ) attached is deployed in a space ( 91 ) between removable upper and lower dies ( 9 ) and ( 90 ), as shown in FIG. 9 .
- the dies ( 9 ) and ( 90 ) are removed to form the housing ( 5 ) covering the capacitor element ( 2 ).
- Tapered surfaces ( 5 a) are formed on lower side portions of the housing ( 5 ) due to the removal of the dies.
- the lead frames ( 3 ) and ( 30 ) are then bent downward along the peripheral surface of the housing ( 5 ).
- the capacitor element ( 2 ) is obtained by sequentially forming a dielectric oxide film ( 21 ), a solid electrolytic layer ( 22 ) made of a conductive polymer, and carbon and silver paste layers ( 23 ) on the surface of an anode body ( 24 ) composed of a sintered valve metal such as tantalum to cover the anode body ( 24 ), as shown in FIG. 10 .
- the anode lead ( 20 ) is made of a valve metal, and protrudes from the center of the anode body ( 24 ).
- the anode lead frame ( 3 ) forms a step portion ( 7 ) within the housing ( 5 ).
- the step portion ( 7 ) includes a first horizontal portion ( 41 ) positioned higher than and substantially parallel to the anode lead ( 20 ), and a second horizontal portion ( 40 ) contacting the anode lead ( 20 ).
- the anode lead frame ( 3 ) is bent from the end of the first horizontal portion ( 41 ) along the outside of the housing ( 5 ) to form a vertical portion ( 35 ).
- the leading end ( 20 a ) of the anode lead ( 20 ) sometimes comes in close proximity to an intersection X between an extended surface of the anode lead ( 20 ) and the housing ( 5 ).
- springback sometimes occurs because of the step portion ( 7 ) being formed by bending the metal anode lead frame ( 3 ).
- springback indicates the deformation of the step portion ( 7 ) in such a way that the angle of bend widens after the metal has been bent, as shown by the angles Y and Z magnified in FIG. 11 . Consequently, the anode lead ( 20 ) of the capacitor element ( 2 ) is attached to the second horizontal portion ( 40 ) of the anode lead frame ( 3 ) at an angle, as shown in FIG. 12 , possibly causing variation in the size of the contact area between the anode lead ( 20 ) of the capacitor element ( 2 ) and the anode lead frame ( 3 ).
- the capacitor element ( 2 ) welded at an angle pushes the cathode lead frame ( 30 ) upward, possibly resulting in the cathode lead frame ( 30 ) jutting out from the housing ( 5 ) and affecting the appearance of the solid electrolytic capacitor ( 1 ). Variation in the bonding strength of the capacitor element ( 2 ) occurs as a result, and reliability is brought into question.
- the following problems occur if the positional relation between the anode lead ( 20 ) and the anode lead frame ( 3 ) is out of alignment when the capacitor element ( 2 ) is attached to the cathode lead frame ( 30 ).
- the substantial contact area between the anode lead ( 20 ) and the anode lead frame ( 3 ) is narrowed because of the anode lead ( 20 ) and the anode lead frame ( 3 ) not being parallel. This results in problems such as weak bonding strength and increased ESR (Equivalent Series Resistance).
- the second horizontal portion ( 40 ) is formed on a large scale with a die when mass producing the anode lead frame ( 3 ), the second horizontal portion ( 40 ) becomes rounded due to wearing of the die, possibly reducing the contact area with the anode lead ( 20 ).
- An object of the present invention which was made in consideration of the above problems, is to provide a highly reliable solid electrolytic capacitor with improved bonding strength between the anode lead and the anode lead frame, and reduced ESR, etc.
- a further object of the present invention is to provide a solid electrolytic capacitor of reduced size and increased capacity in which the anode lead frame is made longer than an initial length by performing a pressing process to flatten out the anode lead frame.
- a solid electrolytic capacitor comprises a capacitor element with a protruding anode lead, an anode lead frame connected to the anode lead, and a cathode lead frame attached to a peripheral surface of the capacitor element.
- the capacitor element, a portion of the anode lead frame, and a portion of the cathode lead frame are covered by a housing, and the anode lead frame has a protruding portion that is bent into a V-shape and protrudes toward the anode lead within the housing.
- the protruding portion includes a first horizontal portion positioned higher than and substantially parallel to the anode lead, a second horizontal portion contacting the anode lead, a linking portion linking the first and second horizontal portions, and an auxiliary bent portion bent upward from the inner end of the second horizontal portion and substantially symmetrical with the linking portion.
- An outer surface of the second horizontal portion where contact is made with the anode lead is formed into a flat contact surface, and an inner surface of the second horizontal portion on an opposite side to the contact surface is formed with a rounded curvature.
- the contact surface of the second horizontal portion with the anode lead is formed by flattening the surface using a pressing process.
- a manufacturing method for the solid electrolytic capacitor comprises the steps of forming a protruding portion having a second horizontal portion at an end portion of an anode lead frame by performing a bending process or a deep drawing process on the anode lead frame; and flattening a contact surface of the second horizontal portion with an anode lead by performing a pressing process on the second horizontal portion, and forming a rounded curvature on a surface of the second horizontal portion on an opposite side to the contact surface.
- the capacitor element ( 2 ) is correctly attached to the anode lead frame ( 3 ), increasing the substantial contact area between the anode lead ( 20 ) and the anode lead frame ( 3 ). Problems such as weak bonding strength and increased ESR resulting from incorrect attachment of the capacitor element ( 2 ) as in the prior art can thereby be resolved.
- a vertical distance H between the first horizontal portion ( 41 ) and the second horizontal portion ( 40 ) can thereby be lengthened without changing the initial cutoff length of the anode lead frame ( 3 ), making it possible to also accommodate cases where the peripheral surface height or outer diameter of the capacitor element ( 2 ) is large. Being able to accommodate increases in the size of the capacitor element ( 2 ) enables the capacity of the solid electrolytic capacitor ( 1 ) to be increased.
- FIG. 1 is a front sectional view of a solid electrolytic capacitor
- FIG. 2 is an enlarged view of the leading end of an anode lead frame
- FIGS. 3A and 3B are illustrative diagrams showing the effects of a protruding portion in the present embodiment, while FIG. 3C shows an alternative protruding portion,
- FIG. 4 is a plan view of a metal plate that is to form lead frames
- FIG. 5 is a perspective view showing the step of forming a lead frame
- FIG. 6 is a cross-sectional view showing the step of forming a lead frame
- FIG. 7 is a perspective view showing the step of forming a solid electrolytic capacitor
- FIG. 8 is a front sectional view of a conventional solid electrolytic capacitor
- FIG. 9 shows a manufacturing step for a conventional electrolytic capacitor
- FIG. 10 is a cross-sectional view of a conventional capacitor element
- FIG. 11 is a front view showing a conventional lead frame
- FIG. 12 shows a conventional capacitor element attached at an angle
- FIG. 13 shows a conventional capacitor element attached at an angle.
- a capacitor element ( 2 ) used in a solid electrolytic capacitor ( 1 ) of the present embodiment is the same as the prior art shown in FIG. 10 .
- polypyrrole is used to form the solid electrolytic layer ( 22 ) of the capacitor element ( 2 ), although other materials that may be used instead include conductive polymers such as polythiophene, polyaniline and polyfuran, and TCNQ (7, 7, 8, 8-tetracyanoquinodimethane) complex.
- An alloy that includes copper, an iron-nickel alloy or the like is used to form the lead frames ( 3 ) and ( 30 ).
- valve metal constituting the anode body ( 24 ) and the anode lead ( 20 ) may, for example, be niobium, titanium, or aluminum.
- FIG. 1 is a front sectional view of the solid electrolytic capacitor ( 1 ) of the present embodiment.
- a thin wire-like anode lead ( 20 ) protrudes from the capacitor element ( 2 ).
- An anode lead frame ( 3 ) is resistance welded to the anode lead ( 20 ), and a cathode lead frame ( 30 ) is attached to a peripheral surface of the capacitor element ( 2 ) with a conductive adhesive ( 26 ).
- the capacitor element ( 2 ), a portion of the anode lead frame ( 3 ) and a portion of the cathode lead frame ( 30 ) are covered with a synthetic resin housing ( 5 ), while portions of both lead frames ( 3 ) and ( 30 ) that protrude outside the housing ( 5 ) are bent downward along a peripheral surface of the housing ( 5 ) and then horizontally along the base of the housing ( 5 ).
- FIG. 2 is an enlarged view of the leading end of the anode lead frame ( 3 ).
- the base end of the anode lead frame ( 3 ) is formed into a protruding portion ( 4 ) that protrudes downward using a pressing process.
- the protruding portion ( 4 ) includes a first horizontal portion ( 41 ) positioned higher than and substantially parallel to the anode lead ( 20 ), a second horizontal portion ( 40 ) contacting the anode lead ( 20 ), a first sloping portion ( 42 ) forming a linking portion that links the horizontal portions ( 40 ) and ( 41 ), and an auxiliary bent portion ( 43 ) bent upward from the inner end of the second horizontal portion ( 40 ) and substantially symmetrical with the first sloping portion ( 42 ).
- the auxiliary bent portion ( 43 ) includes a second sloping portion ( 44 ) that extends upwardly at an angle from the inner end of the second horizontal portion ( 40 ), and a third horizontal portion ( 45 ) that extends inwardly from an upper end portion of the second sloping portion ( 44 ).
- the first and third horizontal portions ( 41 ) and ( 45 ) are substantially the same height as the cathode lead frame ( 30 ) contacting the peripheral surface of the capacitor element ( 2 ) within the housing ( 5 ).
- a contact surface ( 46 ) of the second horizontal portion ( 40 ) with the anode lead ( 20 ) is, as described later, flattened using an additional pressing process.
- a surface ( 47 ) of the second horizontal portion ( 40 ) on the opposite side to the contact surface ( 46 ) is formed with a rounded curvature R.
- the protruding portion ( 4 ) is processed using a center impeller structure for pressing symmetrically on the first and second sloping portions ( 42 ) and ( 44 ), the bending load acting on both sides of the protruding portion ( 4 ) is symmetrical and balanced. Springback of the anode lead frame ( 3 ) is thereby cancelled out, and any displacement or tilting of the anode lead frame ( 3 ) is suppressed.
- the pressing load of the welding electrode is supported on both sides of the protruding portion ( 4 ) when welding the anode lead ( 20 ) to the second horizontal portion ( 40 ), the parallelism of the anode lead ( 20 ) and the second horizontal portion ( 40 ) is not disturbed during welding.
- the capacitor element ( 2 ) is correctly attached to the anode lead frame ( 3 ), enabling problems such as weak bonding strength and increased ESR resulting from incorrect attachment of the capacitor element ( 2 ) as in the prior art to be resolved.
- the contact surface ( 46 ) of the second horizontal portion ( 40 ) with the anode lead ( 20 ) is formed flat, the contact surface ( 46 ) contacts closely with the anode lead ( 20 ). This enables the bonding strength between the anode lead ( 20 ) and the anode lead frame ( 3 ) to be enhanced.
- forming the protruding portion ( 4 ) by bending the anode lead frame ( 3 ) made from a metal plate means that the contact surface ( 46 ) easily becomes rounded when there is a large vertical interval (H in FIG. 2 ) between the first and second horizontal portions ( 41 ) and ( 40 ). This gives rise to reduced bonding strength between the anode lead frame ( 3 ) and the anode lead ( 20 ), and increased ESR.
- the contact area between the contact surface ( 46 ) and the anode lead ( 20 ) is increased. Consequently, the bonding strength between the anode lead ( 20 ) and the anode lead frame ( 3 ) can be enhanced and ESR reduced, even when there is a large vertical interval between the first and second horizontal portions ( 41 ) and ( 40 ).
- the surface ( 47 ) of the second horizontal portion ( 40 ) on the opposite side to the contact surface ( 46 ), that is, the underside of the second horizontal portion ( 40 ) is formed with a rounded curvature R for reinforcement, cracking or the like when the contact surface ( 46 ) of the second horizontal portion ( 40 ) with the anode lead ( 20 ) is flattened can be prevented.
- FIGS. 3A and 3B are illustrative diagrams showing the effects of the protruding portion ( 4 ) in the present embodiment, the protruding portion ( 4 ) having been inverted in comparison with FIG. 2 .
- FIG. 3A shows the protruding portion ( 4 ) having undergone the pressing process to flatten the contact surface ( 46 ) after forming the contact surface ( 46 ) by flattening out the protruding portion ( 4 ) to make it thinner
- FIG. 3B shows the protruding portion ( 4 ) before undergoing the pressing process to flatten the contact surface ( 46 ). Consequently, the contact surface ( 46 ) in FIG. 3B is slightly rounded.
- the vertical distance H from the first horizontal portion ( 41 ) to the second horizontal portion ( 40 ) can thereby be lengthened without changing the initial cutoff length of the anode lead frame ( 3 ), making it possible to accommodate cases where the peripheral surface height or outer diameter of the capacitor element ( 2 ) is large. Being able to accommodate increases in the size of the capacitor element ( 2 ) enables the capacity of the solid electrolytic capacitor ( 1 ) to be increased.
- the auxiliary bent portion ( 43 ) may be left as punched, without providing the third horizontal portion ( 45 ), as shown in FIG. 3C .
- the protruding portion ( 4 ) can be moved toward the capacitor element ( 2 ) by an amount equal to the horizontal length of the third horizontal portion ( 45 ), thereby enabling the housing ( 5 ) of the solid electrolytic capacitor ( 1 ) to be reduced in size.
- a manufacturing method for the anode lead frame ( 3 ) will be shown below.
- a metal plate ( 8 ) forming the material for the lead frames ( 3 ) and ( 30 ) is punched.
- the lead frames ( 3 ) and ( 30 ) are cut out of the metal plate ( 8 ) to provide an anode constituent piece ( 80 ) and a cathode constituent piece ( 81 ) separated from one another.
- a recess ( 31 ) shown in FIGS. 4 and 5 is formed where the capacitor element ( 2 ) is to be set on the cathode constituent piece ( 81 ), thereby suppressing increases in the overall height of the capacitor.
- the protruding portion ( 4 ) is formed by bending the leading end of the anode constituent piece ( 80 ).
- the protruding portion ( 4 ) can also be formed by deep drawing, although the bending process is considered advantageous for giving height to the protruding portion ( 4 ).
- the deep drawing process may, of course, be used to form the protruding portion ( 4 ).
- a receiving die ( 6 ) having a rounded top surface is placed on the inner side of the protruding portion ( 4 ), and a pressing process is performed on the protruding portion ( 4 ) from above using a punch ( 60 ) having a flat working surface.
- the upper surface (i.e., the contact surface ( 46 )) of the second horizontal portion ( 40 ) is thereby leveled, and the underside ( 47 ) of the second horizontal portion ( 40 ) is formed with a rounded surface.
- the anode lead ( 20 ) of the capacitor element ( 2 ) is placed on the contact surface ( 46 ) of the second horizontal portion ( 40 ) of the protruding portion ( 4 ), and the capacitor element ( 2 ) is placed in the recess ( 31 ).
- the anode lead ( 20 ) is resistance welded to the contact surface ( 46 ), and the capacitor element ( 2 ) is attached to the recess ( 31 ) with a conductive adhesive.
- the capacitor element ( 2 ) is covered with the housing ( 5 ), the anode and cathode constituent pieces ( 80 ) and ( 81 ) are cut off to form the lead frames ( 3 ) and ( 30 ), and the lead frames ( 3 ) and ( 30 ) are bent along the housing ( 5 ) to thereby obtain the solid electrolytic capacitor ( 1 ).
- the capacitor element ( 2 ) may be cylindrical.
- the capacitor element ( 2 ) When attaching the capacitor element ( 2 ) to the anode lead frame ( 3 ), the capacitor element ( 2 ) is described above as being deployed above the anode lead frame ( 3 ), and then lowered. However, the anode lead frame ( 3 ) may instead be turned upside down, so that the protruding portion ( 4 ) protrudes downward, and the capacitor element ( 2 ) deployed below the anode lead frame ( 3 ), before being raised and attached.
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Abstract
Description
- 1. Field of the Invention
- The present invention relates to a solid electrolytic capacitor that includes a lead frame, and a method for manufacturing the same.
- 2. Description of the Related Art
- Conventionally, a solid electrolytic capacitor (1) having the configuration shown in
FIG. 8 is known (see Japanese Patent No. 3157722). The solid electrolytic capacitor (1) includes a capacitor element (2) with a thin wire-like anode lead (20) protruding therefrom. An anode lead frame (3) is resistance welded to the anode lead (20), and a cathode lead frame (30) is attached to the peripheral surface of the capacitor element (2) by a conductive adhesive (26). The capacitor element (2) and base ends of both lead frames (3) and (30) are covered with a synthetic resin housing (5), while portions of the lead frames (3) and (30) that protrude outside the housing (5) are bent downward along the peripheral surface of the housing (5), and then horizontally along the base of the housing (5). - When forming the solid electrolytic capacitor (1), the capacitor element (2) with the lead frames (3) and (30) attached is deployed in a space (91) between removable upper and lower dies (9) and (90), as shown in
FIG. 9 . After injecting resin into the space (91), the dies (9) and (90) are removed to form the housing (5) covering the capacitor element (2). Tapered surfaces (5a) (seeFIG. 8 ) are formed on lower side portions of the housing (5) due to the removal of the dies. The lead frames (3) and (30) are then bent downward along the peripheral surface of the housing (5). - The capacitor element (2) is obtained by sequentially forming a dielectric oxide film (21), a solid electrolytic layer (22) made of a conductive polymer, and carbon and silver paste layers (23) on the surface of an anode body (24) composed of a sintered valve metal such as tantalum to cover the anode body (24), as shown in
FIG. 10 . The anode lead (20) is made of a valve metal, and protrudes from the center of the anode body (24). - As shown in
FIG. 8 , the anode lead frame (3) forms a step portion (7) within the housing (5). The step portion (7) includes a first horizontal portion (41) positioned higher than and substantially parallel to the anode lead (20), and a second horizontal portion (40) contacting the anode lead (20). The anode lead frame (3) is bent from the end of the first horizontal portion (41) along the outside of the housing (5) to form a vertical portion (35). - Due to variation in length of the anode lead (20), the leading end (20 a) of the anode lead (20) sometimes comes in close proximity to an intersection X between an extended surface of the anode lead (20) and the housing (5).
- By positioning the upper end of the vertical portion (35) above the second horizontal portion (40) by the height of the step portion (7), room is provided between the intersection X and the vertical portion (35) by an amount equal to the horizontal distance of the tapered portion (5 a) corresponding to the height of the step portion (7). Damage to the leading end of the anode lead (20) due to the vertical portion (35) contacting the leading end of the anode lead (20) when bending the anode lead frame (3) along the housing (5) to form the vertical portion (35) is thereby prevented.
- The applicant was aware of the following problems with the above configuration in need of resolution.
- Springback sometimes occurs because of the step portion (7) being formed by bending the metal anode lead frame (3). Here, springback indicates the deformation of the step portion (7) in such a way that the angle of bend widens after the metal has been bent, as shown by the angles Y and Z magnified in
FIG. 11 . Consequently, the anode lead (20) of the capacitor element (2) is attached to the second horizontal portion (40) of the anode lead frame (3) at an angle, as shown inFIG. 12 , possibly causing variation in the size of the contact area between the anode lead (20) of the capacitor element (2) and the anode lead frame (3). - Also, if the anode lead (20) is welded to the second horizontal portion (40), as shown in
FIG. 13 , the capacitor element (2) welded at an angle pushes the cathode lead frame (30) upward, possibly resulting in the cathode lead frame (30) jutting out from the housing (5) and affecting the appearance of the solid electrolytic capacitor (1). Variation in the bonding strength of the capacitor element (2) occurs as a result, and reliability is brought into question. - Also, the following problems occur if the positional relation between the anode lead (20) and the anode lead frame (3) is out of alignment when the capacitor element (2) is attached to the cathode lead frame (30). The substantial contact area between the anode lead (20) and the anode lead frame (3) is narrowed because of the anode lead (20) and the anode lead frame (3) not being parallel. This results in problems such as weak bonding strength and increased ESR (Equivalent Series Resistance).
- Further, if the second horizontal portion (40) is formed on a large scale with a die when mass producing the anode lead frame (3), the second horizontal portion (40) becomes rounded due to wearing of the die, possibly reducing the contact area with the anode lead (20).
- There are also calls for further reductions in the size and increases in the capacity of capacitors of this type.
- An object of the present invention, which was made in consideration of the above problems, is to provide a highly reliable solid electrolytic capacitor with improved bonding strength between the anode lead and the anode lead frame, and reduced ESR, etc. A further object of the present invention is to provide a solid electrolytic capacitor of reduced size and increased capacity in which the anode lead frame is made longer than an initial length by performing a pressing process to flatten out the anode lead frame.
- A solid electrolytic capacitor comprises a capacitor element with a protruding anode lead, an anode lead frame connected to the anode lead, and a cathode lead frame attached to a peripheral surface of the capacitor element. The capacitor element, a portion of the anode lead frame, and a portion of the cathode lead frame are covered by a housing, and the anode lead frame has a protruding portion that is bent into a V-shape and protrudes toward the anode lead within the housing.
- The protruding portion includes a first horizontal portion positioned higher than and substantially parallel to the anode lead, a second horizontal portion contacting the anode lead, a linking portion linking the first and second horizontal portions, and an auxiliary bent portion bent upward from the inner end of the second horizontal portion and substantially symmetrical with the linking portion.
- An outer surface of the second horizontal portion where contact is made with the anode lead is formed into a flat contact surface, and an inner surface of the second horizontal portion on an opposite side to the contact surface is formed with a rounded curvature.
- The contact surface of the second horizontal portion with the anode lead is formed by flattening the surface using a pressing process.
- Further, a manufacturing method for the solid electrolytic capacitor comprises the steps of forming a protruding portion having a second horizontal portion at an end portion of an anode lead frame by performing a bending process or a deep drawing process on the anode lead frame; and flattening a contact surface of the second horizontal portion with an anode lead by performing a pressing process on the second horizontal portion, and forming a rounded curvature on a surface of the second horizontal portion on an opposite side to the contact surface.
-
- 1. A protruding portion (4) of an anode lead frame (3) is formed by bending a portion of the anode lead frame (3) into a first horizontal portion (41), a linking portion (specifically, sloping portion (42) in
FIG. 2 ), a second horizontal portion (40), and an auxiliary bent portion (43). When forming the protruding portion (4) of the anode lead frame (3), the bending load acting on both sides of the protruding portion (4) is symmetrical and balanced, because processing is preformed using a center impeller structure for pressing symmetrically with both ends of the protruding portion (4) held down. Any displacement due to springback of the anode lead frame (3) is thereby symmetrical, allowing the protruding portion (4) to be kept horizontal. Also, since the pressing load of the welding electrode is supported on both sides of the protruding portion (4) when welding the anode lead (20) to the second horizontal portion (40), the parallelism of the anode lead (20) and the second horizontal portion (40) is not disturbed during welding. - Consequently, the capacitor element (2) is correctly attached to the anode lead frame (3), increasing the substantial contact area between the anode lead (20) and the anode lead frame (3). Problems such as weak bonding strength and increased ESR resulting from incorrect attachment of the capacitor element (2) as in the prior art can thereby be resolved.
- 2. Also, because a contact surface (46) of the second horizontal portion (40) with the anode lead (20) is formed flat, the contact area between the contact surface (46) and the anode lead (20) is enlarged. In this respect also, the bonding strength between the anode lead (20) and the anode lead frame (3) can be enhanced, and ESR reduced. Further, because a surface (47) of the second horizontal portion (40) on the opposite side to the contact surface (46), that is, the underside of the second horizontal portion (40) is rounded for reinforcement, cracking or the like when the contact surface (46) of the second horizontal portion (40) with the anode lead (20) is pressed flat can be prevented.
- 3. Also, because the contact surface (46) of the second horizontal portion (40) with the anode lead (20) undergoes a pressing process for flattening out the protruding portion (4) using a die to make the protruding portion (4) thinner, the distance from the first horizontal portion (41) to the auxiliary bent portion (43) via the sloping portion (42) and the second horizontal portion (40) is lengthened in comparison to when a pressing process to flatten out the contact surface (46) is not performed. That is, because the contact surface (46) is formed by flattening out the protruding portion (4) to make it thinner, an equivalent amount of the material is protruded, elongating the sloping portion (42) and the auxiliary bent portion (43), and increasing the overall length of the protruding portion (4).
- A vertical distance H between the first horizontal portion (41) and the second horizontal portion (40) can thereby be lengthened without changing the initial cutoff length of the anode lead frame (3), making it possible to also accommodate cases where the peripheral surface height or outer diameter of the capacitor element (2) is large. Being able to accommodate increases in the size of the capacitor element (2) enables the capacity of the solid electrolytic capacitor (1) to be increased.
-
FIG. 1 is a front sectional view of a solid electrolytic capacitor, -
FIG. 2 is an enlarged view of the leading end of an anode lead frame, -
FIGS. 3A and 3B are illustrative diagrams showing the effects of a protruding portion in the present embodiment, whileFIG. 3C shows an alternative protruding portion, -
FIG. 4 is a plan view of a metal plate that is to form lead frames, -
FIG. 5 is a perspective view showing the step of forming a lead frame, -
FIG. 6 is a cross-sectional view showing the step of forming a lead frame, -
FIG. 7 is a perspective view showing the step of forming a solid electrolytic capacitor, -
FIG. 8 is a front sectional view of a conventional solid electrolytic capacitor, -
FIG. 9 shows a manufacturing step for a conventional electrolytic capacitor, -
FIG. 10 is a cross-sectional view of a conventional capacitor element, -
FIG. 11 is a front view showing a conventional lead frame, -
FIG. 12 shows a conventional capacitor element attached at an angle, and -
FIG. 13 shows a conventional capacitor element attached at an angle. - An embodiment of the present invention will be described below with reference to the accompanying drawings. A capacitor element (2) used in a solid electrolytic capacitor (1) of the present embodiment is the same as the prior art shown in
FIG. 10 . Here, polypyrrole is used to form the solid electrolytic layer (22) of the capacitor element (2), although other materials that may be used instead include conductive polymers such as polythiophene, polyaniline and polyfuran, and TCNQ (7, 7, 8, 8-tetracyanoquinodimethane) complex. An alloy that includes copper, an iron-nickel alloy or the like is used to form the lead frames (3) and (30). - Apart from tantalum, the valve metal constituting the anode body (24) and the anode lead (20) may, for example, be niobium, titanium, or aluminum.
-
FIG. 1 is a front sectional view of the solid electrolytic capacitor (1) of the present embodiment. A thin wire-like anode lead (20) protrudes from the capacitor element (2). An anode lead frame (3) is resistance welded to the anode lead (20), and a cathode lead frame (30) is attached to a peripheral surface of the capacitor element (2) with a conductive adhesive (26). The capacitor element (2), a portion of the anode lead frame (3) and a portion of the cathode lead frame (30) are covered with a synthetic resin housing (5), while portions of both lead frames (3) and (30) that protrude outside the housing (5) are bent downward along a peripheral surface of the housing (5) and then horizontally along the base of the housing (5). -
FIG. 2 is an enlarged view of the leading end of the anode lead frame (3). The base end of the anode lead frame (3) is formed into a protruding portion (4) that protrudes downward using a pressing process. The protruding portion (4) includes a first horizontal portion (41) positioned higher than and substantially parallel to the anode lead (20), a second horizontal portion (40) contacting the anode lead (20), a first sloping portion (42) forming a linking portion that links the horizontal portions (40) and (41), and an auxiliary bent portion (43) bent upward from the inner end of the second horizontal portion (40) and substantially symmetrical with the first sloping portion (42). The auxiliary bent portion (43) includes a second sloping portion (44) that extends upwardly at an angle from the inner end of the second horizontal portion (40), and a third horizontal portion (45) that extends inwardly from an upper end portion of the second sloping portion (44). The first and third horizontal portions (41) and (45) are substantially the same height as the cathode lead frame (30) contacting the peripheral surface of the capacitor element (2) within the housing (5). - A contact surface (46) of the second horizontal portion (40) with the anode lead (20) is, as described later, flattened using an additional pressing process. A surface (47) of the second horizontal portion (40) on the opposite side to the contact surface (46) is formed with a rounded curvature R.
- Because the protruding portion (4) is processed using a center impeller structure for pressing symmetrically on the first and second sloping portions (42) and (44), the bending load acting on both sides of the protruding portion (4) is symmetrical and balanced. Springback of the anode lead frame (3) is thereby cancelled out, and any displacement or tilting of the anode lead frame (3) is suppressed.
- Also, since the pressing load of the welding electrode is supported on both sides of the protruding portion (4) when welding the anode lead (20) to the second horizontal portion (40), the parallelism of the anode lead (20) and the second horizontal portion (40) is not disturbed during welding.
- Consequently, the capacitor element (2) is correctly attached to the anode lead frame (3), enabling problems such as weak bonding strength and increased ESR resulting from incorrect attachment of the capacitor element (2) as in the prior art to be resolved.
- Since the contact surface (46) of the second horizontal portion (40) with the anode lead (20) is formed flat, the contact surface (46) contacts closely with the anode lead (20). This enables the bonding strength between the anode lead (20) and the anode lead frame (3) to be enhanced. In particular, forming the protruding portion (4) by bending the anode lead frame (3) made from a metal plate means that the contact surface (46) easily becomes rounded when there is a large vertical interval (H in
FIG. 2 ) between the first and second horizontal portions (41) and (40). This gives rise to reduced bonding strength between the anode lead frame (3) and the anode lead (20), and increased ESR. - By performing the additional pressing process to flatten the contact surface (46), the contact area between the contact surface (46) and the anode lead (20) is increased. Consequently, the bonding strength between the anode lead (20) and the anode lead frame (3) can be enhanced and ESR reduced, even when there is a large vertical interval between the first and second horizontal portions (41) and (40).
- Further, because the surface (47) of the second horizontal portion (40) on the opposite side to the contact surface (46), that is, the underside of the second horizontal portion (40) is formed with a rounded curvature R for reinforcement, cracking or the like when the contact surface (46) of the second horizontal portion (40) with the anode lead (20) is flattened can be prevented.
- With solid electrolytic capacitors of this type, there are cases where it is desirable to enlarge the diameter of the capacitor element (2) in order to accommodate increased capacity. In this case, the vertical interval H between the first and second horizontal portions (41) and (40) needs to be widened to avoid contact between the peripheral surface of the capacitor element (2) and the auxiliary bent portion (43). This is described below.
-
FIGS. 3A and 3B are illustrative diagrams showing the effects of the protruding portion (4) in the present embodiment, the protruding portion (4) having been inverted in comparison withFIG. 2 .FIG. 3A shows the protruding portion (4) having undergone the pressing process to flatten the contact surface (46) after forming the contact surface (46) by flattening out the protruding portion (4) to make it thinner, whileFIG. 3B shows the protruding portion (4) before undergoing the pressing process to flatten the contact surface (46). Consequently, the contact surface (46) inFIG. 3B is slightly rounded. - Because the pressing process in
FIG. 3A used to form the contact surface (46) involves flattening out the protruding portion (4) to make it thinner, an equivalent amount of material is protruded, elongating the first sloping portion (42) and the auxiliary bent portion (43), and increasing the overall length of the protruding portion (4). - The vertical distance H from the first horizontal portion (41) to the second horizontal portion (40) can thereby be lengthened without changing the initial cutoff length of the anode lead frame (3), making it possible to accommodate cases where the peripheral surface height or outer diameter of the capacitor element (2) is large. Being able to accommodate increases in the size of the capacitor element (2) enables the capacity of the solid electrolytic capacitor (1) to be increased.
- The auxiliary bent portion (43) may be left as punched, without providing the third horizontal portion (45), as shown in
FIG. 3C . In this case, the protruding portion (4) can be moved toward the capacitor element (2) by an amount equal to the horizontal length of the third horizontal portion (45), thereby enabling the housing (5) of the solid electrolytic capacitor (1) to be reduced in size. - A manufacturing method for the anode lead frame (3) will be shown below.
- As shown in
FIG. 4 , a metal plate (8) forming the material for the lead frames (3) and (30) is punched. The lead frames (3) and (30) are cut out of the metal plate (8) to provide an anode constituent piece (80) and a cathode constituent piece (81) separated from one another. A recess (31) shown inFIGS. 4 and 5 is formed where the capacitor element (2) is to be set on the cathode constituent piece (81), thereby suppressing increases in the overall height of the capacitor. - Next, as shown in
FIG. 5 , the protruding portion (4) is formed by bending the leading end of the anode constituent piece (80). In this case, the protruding portion (4) can also be formed by deep drawing, although the bending process is considered advantageous for giving height to the protruding portion (4). The deep drawing process may, of course, be used to form the protruding portion (4). - Next, as shown in the cross-sectional view of
FIG. 6 , a receiving die (6) having a rounded top surface is placed on the inner side of the protruding portion (4), and a pressing process is performed on the protruding portion (4) from above using a punch (60) having a flat working surface. The upper surface (i.e., the contact surface (46)) of the second horizontal portion (40) is thereby leveled, and the underside (47) of the second horizontal portion (40) is formed with a rounded surface. - Next, as shown in
FIG. 7 , the anode lead (20) of the capacitor element (2) is placed on the contact surface (46) of the second horizontal portion (40) of the protruding portion (4), and the capacitor element (2) is placed in the recess (31). The anode lead (20) is resistance welded to the contact surface (46), and the capacitor element (2) is attached to the recess (31) with a conductive adhesive. Then, similarly to the prior art, the capacitor element (2) is covered with the housing (5), the anode and cathode constituent pieces (80) and (81) are cut off to form the lead frames (3) and (30), and the lead frames (3) and (30) are bent along the housing (5) to thereby obtain the solid electrolytic capacitor (1). Although shown inFIG. 7 as being rectangular, the capacitor element (2) may be cylindrical. - When attaching the capacitor element (2) to the anode lead frame (3), the capacitor element (2) is described above as being deployed above the anode lead frame (3), and then lowered. However, the anode lead frame (3) may instead be turned upside down, so that the protruding portion (4) protrudes downward, and the capacitor element (2) deployed below the anode lead frame (3), before being raised and attached.
Claims (4)
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JP2006017210A JP4585459B2 (en) | 2006-01-26 | 2006-01-26 | Solid electrolytic capacitor and manufacturing method thereof |
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Cited By (2)
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US20230135896A1 (en) * | 2021-10-29 | 2023-05-04 | Samsung Electro-Mechanics Co., Ltd. | Tantalum capacitor |
US20230290579A1 (en) * | 2022-03-11 | 2023-09-14 | Samsung Electro-Mechanics Co., Ltd. | Tantalum capacitor |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8514550B2 (en) * | 2011-03-11 | 2013-08-20 | Avx Corporation | Solid electrolytic capacitor containing a cathode termination with a slot for an adhesive |
US8848343B2 (en) | 2012-10-12 | 2014-09-30 | Kemet Electronics Corporation | Solid electrolytic capacitor and method for manufacturing the same |
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US5638253A (en) * | 1994-04-28 | 1997-06-10 | Rohm Co. Ltd. | Package-type solid electrolytic capacitor |
US6665172B1 (en) * | 2002-05-22 | 2003-12-16 | Samsung Electro-Mechanics Co., Ltd. | Solid electrolytic capacitor |
US6891716B2 (en) * | 2000-11-20 | 2005-05-10 | Epcos Ag | Capacitor |
US6975503B2 (en) * | 2004-01-07 | 2005-12-13 | Nec Tokin Corporation | Chip type solid electrolytic capacitor having plated fillet surface and method of manufacturing the same |
US7149077B2 (en) * | 2004-12-10 | 2006-12-12 | Nec Tokin Corporation | Solid electrolytic capacitor with face-down terminals, manufacturing method of the same, and lead frame for use therein |
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JPS62168633U (en) * | 1986-04-15 | 1987-10-26 | ||
JPH0336125U (en) * | 1989-08-22 | 1991-04-09 | ||
JP3157722B2 (en) * | 1996-08-23 | 2001-04-16 | 富山日本電気株式会社 | Chip type solid electrolytic capacitor |
JP2005057105A (en) * | 2003-08-06 | 2005-03-03 | Nec Tokin Corp | Chip type solid electrolytic capacitor |
-
2006
- 2006-01-26 JP JP2006017210A patent/JP4585459B2/en active Active
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US5638253A (en) * | 1994-04-28 | 1997-06-10 | Rohm Co. Ltd. | Package-type solid electrolytic capacitor |
US6891716B2 (en) * | 2000-11-20 | 2005-05-10 | Epcos Ag | Capacitor |
US6665172B1 (en) * | 2002-05-22 | 2003-12-16 | Samsung Electro-Mechanics Co., Ltd. | Solid electrolytic capacitor |
US6975503B2 (en) * | 2004-01-07 | 2005-12-13 | Nec Tokin Corporation | Chip type solid electrolytic capacitor having plated fillet surface and method of manufacturing the same |
US7149077B2 (en) * | 2004-12-10 | 2006-12-12 | Nec Tokin Corporation | Solid electrolytic capacitor with face-down terminals, manufacturing method of the same, and lead frame for use therein |
Cited By (3)
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US20230135896A1 (en) * | 2021-10-29 | 2023-05-04 | Samsung Electro-Mechanics Co., Ltd. | Tantalum capacitor |
US12014882B2 (en) * | 2021-10-29 | 2024-06-18 | Samsung Electro-Mechanics Co., Ltd. | Tantalum capacitor |
US20230290579A1 (en) * | 2022-03-11 | 2023-09-14 | Samsung Electro-Mechanics Co., Ltd. | Tantalum capacitor |
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JP2007201122A (en) | 2007-08-09 |
JP4585459B2 (en) | 2010-11-24 |
US7283352B1 (en) | 2007-10-16 |
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