JP2004014643A - Method of connecting fuse wire for capacitor element in solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent damage to a capacitor element 1 in a process where a fuse wire 4 is bent in the direction of the capacitor element 1 so that the tip of the fuse wire 4 contacts or comes close to a cathode film 1c when the tip of the fuse wire 4 connected to a cathode lead terminal 3 is bonded with conductive paste 16 to the cathode film 1c which forms the surface of the chip body 1a of the capacitor element 1 fixed to an anode lead terminal 2 in a solid electrolytic capacitor. <P>SOLUTION: The process for bending the fuse wire 4 is performed in a state that the cathode lead terminal 3 is elastically deformed by a pushing body 14 against the elasticity of the cathode lead terminal 3 so that the tip of the fuse wire 4 is relatively away from the chip body 1a of the capacitor element 1, and the elastically deformed state is released after the bending process. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a solid electrolytic capacitor using a capacitor element made of a valve metal such as tantalum or niobium, a solid electrolytic capacitor having a fuse wire that is blown for one or both of temperature and overcurrent, The present invention relates to a method for connecting a fuse wire to the capacitor element.
[0002]
[Prior art]
In general, as shown in FIG. 1, a solid electrolytic capacitor of this type has a capacitor element 1 formed by, for example, sintering a powder of a valve metal such as tantalum or the like into a porous form, and the like. And a cathode film 1c formed on the outer peripheral surface of the chip body 1a. The capacitor element 1 is disposed between an anode lead terminal 2 and a cathode lead terminal 3 by a capacitor. The anode rod 1b of the element 1 is disposed so as to be fixed to the anode lead terminal 2, and the space between the cathode film 1c of the capacitor element 1 and the cathode lead terminal 3 is connected by a fuse wire 4 such as a solder wire. After being electrically connected, the entire structure is sealed with a package body 5 made of synthetic resin.
[0003]
In FIG. 1, reference numeral 6 denotes an elastic resin for covering the fuse wire 4 and enabling the fusing. A portion of the lead terminals 2 and 3 protruding from the package 5 is bent toward the lower surface of the package 5.
[0004]
Incidentally, Japanese Patent Application Laid-Open Nos. Hei 5-326602, Hei 6-20891, Hei 6-45208 and Hei 7-254532 as prior arts disclose a solid electrolytic capacitor provided with the safety fuse described above. For electrically connecting the capacitor element 1 and the cathode lead terminal 3 with a fuse wire 4 such as a solder wire, a method for connecting a fuse wire by wire bonding as described below has been proposed.
[0005]
That is, in this prior art, first, a ball portion 4a is formed at the lower end of a fuse wire inserted into a cabillary tool, and the ball portion 4a is moved downward with respect to the upper surface of the cathode lead terminal 3 by the downward movement of the cabillary tool. By pressing while crushing and deforming, the fuse wire is joined so as to rise from the cathode lead terminal, and then the cabillary tool is once moved up, and then the fuse wire rising from the cathode lead terminal is connected to the cabillary tool. At the same time, the near portion is blown by heating, and at the same time, the ball portion 4a is provided at the lower end of the fuse wire on the cab tool, and the ball portion is provided at the tip (upper end) of the fuse wire 4 joined to the cathode lead terminal 3. 4b are formed, and then the tip of the fuse wire 4 joined to the cathode lead terminal 3 (the fuse wire (Except for the base end portion joined to the cathode lead terminal) in the direction of the capacitor element 1, and then the ball portion 4 b at the tip of the fuse wire 4 is connected to the chip body 1 a of the capacitor element 1. In this method, the cathode film 1c on the upper surface is bonded by being crushed and deformed by a bonding tool and pressed.
[0006]
[Problems to be solved by the invention]
However, since the chip body 1a of the capacitor element 1 of the solid electrolytic capacitor has a rather brittle property such as a porous structure, the fuse 1 is formed with respect to the cathode film 1c formed on the surface of the chip body 1a. When joining the tip of the wire 4, as in the prior art, a ball portion 4 b is formed at the tip of the fuse wire 4, and the ball portion 4 b is joined to the cathode film 1 c by pressing with a bonding tool. This means that a large stress acts on the chip body 1a in the capacitor element 1.
[0007]
Therefore, in the prior art method of connecting a fuse wire to a capacitor element, increasing the pressing force by a bonding tool to improve the reliability of bonding of the fuse wire 4 to the cathode film 1c requires increasing the chip body 1a and the chip body 1a. Since the stress on the cathode film 1c increases and chips and / or cracks are generated in this portion, the incidence of defective products increases, and the bonding tool is used to reduce the incidence of defective products. Lowering the pressing force caused by the above problem has a problem that the reliability of joining the fuse wire 4 to the cathode film 1c is reduced.
[0008]
Among the above publications, Japanese Patent Laid-Open Publication No. Hei 6-20891 discloses that a fuse wire 4 joined to a cathode lead terminal 3 so as to rise is bent in the direction of the capacitor element 1, It has also been proposed to join the tip to the cathode film 1c of the capacitor element 1 with a conductive paste.
[0009]
This bonding method using a conductive paste ensures that stress is applied to the capacitor element when the tip of the fuse wire bonded to the cathode lead terminal is pressed and bonded to the cathode film of the capacitor element. Can be avoided.
[0010]
However, on the other hand, in the case of joining with a conductive paste, in order to secure a predetermined joining strength in the joining, when the fuse wire joined so as to rise to the cathode lead terminal is bent in the direction of the capacitor element, It is necessary that the tip is in contact with or very close to the cathode film of the capacitor element. In this way, the fuse wire must be in contact with the cathode film of the chip body of the capacitor element. Alternatively, when bending in the direction of the capacitor element so as to be extremely close, a tool such as a bend bar for performing the bending contacts the tip of the fuse wire with the cathode film in the chip body of the capacitor element. Or, due to the close proximity, contact with the capacitor element occurs frequently, and When the fuse wire is bent in the direction of the capacitor element, chipping and / or cracking of the chip body and the cathode film of the capacitor element are more likely to occur because the possibility of applying stress to the capacitor element increases. There's a problem.
[0011]
SUMMARY OF THE INVENTION It is a technical object of the present invention to provide a connection method that solves the above-described problem that occurs when a fuse wire is bonded to a cathode film of a capacitor element with a conductive paste.
[0012]
[Means for Solving the Problems]
In order to achieve this technical object, claim 1 of the present invention provides
`` A step of bending the tip portion of the fuse wire bonded to the cathode lead terminal of the metal lead frame in the direction of the capacitor element fixed to the anode lead terminal of the lead frame, Bonding with a conductive paste to the cathode film on the surface of the chip body of the capacitor element,
The step of bending the fuse wire is performed in a state in which the lead frame frame is elastically deformed such that the tip of the fuse wire and the tip of the fuse wire are relatively separated from each other against the elasticity thereof. The elastically deformed state is released after the bending step. "
It is characterized by:
[0013]
Claim 2 of the present invention
"In the first aspect, a step of forming a ball portion at the tip of the fuse wire is provided before the step of bending the fuse wire bonded to the cathode lead terminal."
It is characterized by:
[0014]
Furthermore, claim 3 of the present invention
In the method according to claim 1, before the step of bending the fuse wire bonded to the cathode lead terminal, a step of forming a ball portion at the tip of the fuse wire, and the ball portion is crushed into a disk shape and deformed. Process. "
It is characterized by:
[0015]
The above-mentioned elastic deformation of the lead frame includes:
▲ 1 ▼. The case where the cathode lead terminal of the lead frame is bent against its elasticity as described in claim 4.
▲ 2 ▼. 6. A case as claimed in claim 5, wherein the anode lead terminal of the lead frame is bent against its elasticity.
(3). 7. The case where both the anode lead terminal and the cathode lead terminal are curved in opposite directions as described in claim 6.
And exists.
[0016]
[Action and Effect of the Invention]
As described above, the lead frame is elastically deformed so that the chip body of the capacitor element and the tip portion of the fuse wire are relatively separated from each other against the elasticity thereof. After bending the fuse wire bonded to the terminal in the direction of the capacitor element, by releasing the state of the elastic deformation, the tip part of the chip body of the capacitor element and the fuse wire, Since the two members return to the original state due to the restoring elastic force accompanying the release of the elastic deformation, the tip of the bent fuse wire contacts the cathode film on the surface of the chip body of the capacitor element, or Will be very close.
[0017]
This allows the fuse wire bonded to the cathode lead terminal to be bent so that the tip of the fuse wire is in contact with or very close to the cathode film on the surface of the chip body of the capacitor element. Can be performed at a position away from the capacitor element, and the possibility that a tool such as a bend bar for the bending process comes into contact with the capacitor element can be greatly reduced. The occurrence rate of defective products during processing can be reliably reduced.
[0018]
In this case, as described in claim 2, by forming the ball portion at the tip of the fuse wire, the bonding area by the conductive paste can be increased, and therefore, the bonding strength can be improved.
[0019]
Further, as described in claim 3, a ball portion is formed at the tip of the fuse wire, and the ball portion is crushed into a disk shape and deformed, thereby further increasing the bonding area, and further improving the bonding strength. Can be achieved.
[0020]
Then, as described above, the elastic deformation that causes the tip body of the capacitor element and the fuse wire to be relatively separated from each other is performed by bending the cathode lead terminal as described in claim 4. Or by bending the anode lead terminal as described in claim 5, so that one of the paired lead terminals is bent and deformed against its elasticity. Therefore, there is an advantage that the structure for the elastic deformation can be simplified.
[0021]
On the other hand, in the case where both the anode lead terminal and the cathode lead terminal are curved in directions opposite to each other as described above, the structure for elastic deformation is complicated. On the other hand, since the elastic deformation can be distributed to both lead terminals, the distance between the chip body of the capacitor element and the tip portion of the fuse wire is relatively increased, and the elastic limit of both lead terminals is reduced. Since the size can be increased without causing permanent deformation beyond that, there is an advantage that occurrence of defective products can be further reduced.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
2 to 11 show the first embodiment.
[0024]
In FIG. 2, reference numeral 1 denotes a capacitor element. The capacitor element 1 is a chip body 1a obtained by sintering a valve metal powder such as tantalum into a porous material in the same manner as in FIG. An anode rod 1b protruding from one end surface of the chip body 1a, and a cathode film 1c formed on the outer peripheral surface of the chip body 1a.
[0025]
Reference numeral 10 denotes a lead frame made of a metal plate. The lead frame 10 is provided on a section bar 10c which is disposed at a suitable interval in the longitudinal direction between a pair of left and right side frames 10a and 10b extending in the longitudinal direction. The anode lead terminal 2 is integrally provided at a portion between the section bars 10c on one of the side frames 10a and 10b. The cathode lead terminal 3 is integrally provided on the other side frame 10b at a portion between the section bars 10c.
[0026]
Then, as shown in FIG. 3, the capacitor element 1 is placed between the anode lead terminal 2 and the cathode lead terminal 3 forming a pair in the lead frame 10 with the anode rod 1 b facing the anode lead terminal 2. After the supply, the anode rod 1b is fixed to the anode lead terminal 2 by welding or the like.
[0027]
Next, as shown in FIG. 4, a solder wire 4 'constituting the fuse wire 4 is inserted through a wire bonding cabillary tool 11, and the ball portion 4a formed at the lower end of the solder wire 4' is removed. After the solder wire 4 ′ is pressed against the upper surface of the cathode lead terminal 3 while being pressed against the upper surface of the cathode lead terminal 3 by downward movement, the solder wire 4 ′ is joined to the cathode lead terminal 3 so as to rise up. The rari tool 11 is once moved upward.
[0028]
Next, a portion of the solder wire 4 ′ rising from the cathode lead terminal 3, which is close to the cabillary tool 11, is melted by heating with a hydrogen flame torch or the like ejected from the nozzle 12 as shown in FIG. The fuse wire 4 joined to the lead terminal 3 was cut off from the solder wire 4 ′ on the capillary tool 11 side, and at the same time, the ball portion 4 a was joined to the cathode lead terminal 3 at the lower end of the solder wire 4 ′ on the capillary tool side. The ball portions 4b are formed at the tips (upper ends) of the fuse wires 4, respectively.
[0029]
Next, as shown in FIGS. 6 and 7, the ball portion 4b at the tip of the fuse wire 4 joined to the cathode lead terminal 3 is pinched by a pair of punches 13a, 13b to form the chip body 1a of the capacitor element 1. Is deformed by crushing into a disk shape having a plane parallel to the upper surface of the disk.
[0030]
Next, as shown in FIG. 8, in a state where both side frames 10a and 10b of the lead frame 10 are immovably supported, the cathode lead terminal 3 is moved upward by pushing up the push body 14 from the lower surface side. The fuse wire 4 is elastically deformed so as to be bent upward against the elasticity of the terminal 3 so that a tip portion of the fuse wire 4 (a portion of the fuse wire excluding a base end portion joined to the cathode lead terminal). Are separated from the cathode film 1c on the surface of the chip body 1a of the capacitor element 1, in other words, are separated.
[0031]
Then, while maintaining the elastically deformed state, the tip of the fuse wire 4 on the upper surface of the cathode lead terminal 3 is moved forward by the bend bar 15 as shown in FIG. Bending in the direction of 1.
[0032]
In addition, before the bending process for the fuse wire 4, the conductive paste 16 is previously dropped on a top surface of the cathode film 1 c of the chip body 1 a of the capacitor element 1 by dripping from a dispenser (not shown) or the like. And apply. The application of the conductive paste 16 may be performed after the elastically deformed state is released, as described later.
[0033]
Then, the state in which the cathode lead terminal 3 is elastically deformed is released by the downward movement of the push body 14, so that the cathode lead terminal 3 is returned to its original position by its elastic force as shown in FIG. Therefore, the tip of the fuse wire 4 bent as described above, that is, the ball portion 4b crushed and deformed into a disk shape comes into contact with the cathode film 1c on the surface of the chip body 1a of the capacitor element 1. Or very close.
[0034]
As a result, the tip end of the fuse wire 4 bonded to the cathode lead terminal 3, that is, the ball portion 4 b crushed and deformed into a disk shape contacts or is extremely close to the cathode film 1 c on the surface of the chip body 1 a of the capacitor element 1. Can be performed at a position away from the capacitor element 1 by the amount of the elastic displacement, in other words, at a position away from the capacitor element 1. Therefore, the bending tool, that is, the bend bar 15 Thus, the possibility of contact with the device 1 can be greatly reduced.
[0035]
After passing through these steps, a step of curing the conductive paste 16 in a heating furnace, a step of covering the fuse wire 4 with the elastic resin 6, a step of sealing with the package body 5, and a step of sealing both the lead terminals 2 , 3 are separated from the lead frame 10 and then bent to the lower surface side of the package body 5 to obtain a completed solid electrolytic capacitor having a configuration as shown in FIG.
[0036]
Next, FIG. 12 shows a second embodiment.
[0037]
The second embodiment is different from the first embodiment in that the anode lead terminal 2 is replaced with a push body 16 by replacing the cathode lead terminal 3 with downward bending deformation against its elasticity as in the first embodiment. By the downward movement, the anode lead terminal 2 is elastically deformed so as to be curved upward against the elasticity of the anode lead terminal 2, so that the tip portion of the fuse wire 4 (the fuse wire is joined to the cathode lead terminal). The portion excluding the base end portion) is separated from the cathode film 1c on the surface of the chip body 1a of the capacitor element 1, in other words, is separated from the cathode film 1c. Others are the same as the first embodiment.
[0038]
Also in this case, similarly to the above, the tip of the fuse wire 4 joined to the cathode lead terminal 3, that is, the ball portion 4 b crushed and deformed into a disk shape is formed on the cathode film 1 c on the surface of the chip body 1 a of the capacitor element 1. Can be bent at a position separated from the capacitor element 1 by the amount of the elastic displacement, in other words, at a position distant from the capacitor element 1 by the elastic displacement. That is, the possibility that the bend bar 15 comes into contact with the capacitor element 1 can be greatly reduced.
[0039]
Of course, both the first embodiment and the second embodiment are combined, that is, both the anode lead terminal 2 is bent downward and the cathode lead terminal is bent upward. By bending the lead terminals 2 and 3 in directions opposite to each other, the tip portion of the fuse wire 4 is separated from the cathode film 1c on the surface of the chip body 1a of the capacitor element 1, that is, is separated from the cathode film 1c. Needless to say, this is acceptable.
[Brief description of the drawings]
FIG. 1 is a vertical sectional front view of a solid electrolytic capacitor provided with a fuse wire.
FIG. 2 is a perspective view showing a capacitor element and a lead frame according to the first embodiment.
FIG. 3 is a perspective view showing a state in which a capacitor element is supplied to a lead frame in the first embodiment.
FIG. 4 is a perspective view showing a state in which a solder wire is joined to a cathode lead terminal of a lead frame in the first embodiment.
FIG. 5 is a perspective view showing a state where a fuse wire is cut from the solder wire in the first embodiment.
FIG. 6 is a perspective view showing a state in which the tip of the fuse wire is crushed and deformed in the first embodiment.
FIG. 7 is a sectional view taken along line VII-VII of FIG. 6;
FIG. 8 is a diagram showing a state in which the cathode lead terminal is bent and deformed in the first embodiment.
FIG. 9 is a diagram showing a state where a fuse wire is bent in the first embodiment.
FIG. 10 is a view showing a state in which the bending deformation of the cathode lead terminal is released in the first embodiment.
FIG. 11 is a vertical sectional front view of the solid electrolytic capacitor according to the first embodiment.
FIG. 12 is a diagram showing a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Capacitor element 1a Chip body 1b Anode rod 1c Cathode film 2 Anode lead terminal 3 Cathode lead terminal 4 Fuse wire 4a, 4b Ball part 5 Package body 16 Conductive paste

Claims (6)

A step of bending the tip portion of the fuse wire bonded to the cathode lead terminal of the metal lead frame in the direction of the capacitor element fixed to the anode lead terminal of the lead frame; and Bonding with a conductive paste to the cathode film on the surface of the chip body of the capacitor element,
The step of bending the fuse wire is performed in a state in which the lead frame frame is elastically deformed such that the tip of the fuse wire and the tip of the fuse wire are relatively separated from each other against the elasticity thereof. A method of connecting a fuse wire to a capacitor element in a solid electrolytic capacitor, wherein the elastically deformed state is released after the bending step. 2. The solid electrolytic capacitor according to claim 1, further comprising a step of forming a ball portion at a tip of the fuse wire before the step of bending the fuse wire bonded to the cathode lead terminal. Connection method of the fuse wire to the capacitor element in the above. 2. The method according to claim 1, wherein before the step of bending the fuse wire bonded to the cathode lead terminal, a step of forming a ball portion at the tip of the fuse wire, and crushing and deforming the ball portion into a disk shape. And a method of connecting a fuse wire to a capacitor element in a solid electrolytic capacitor. The capacitor element in a solid electrolytic capacitor according to any one of claims 1 to 3, wherein the elastic deformation is an elastic deformation in which a cathode lead terminal of the lead frame is bent against its elasticity. How to connect the fuse wire to 4. The capacitor element in a solid electrolytic capacitor according to claim 1, wherein the elastic deformation is an elastic deformation in which the anode lead terminal of the lead frame is bent against its elasticity. How to connect the fuse wire to The capacitor element according to any one of claims 1 to 3, wherein the elastic deformation is an elastic deformation in which both the anode lead terminal and the cathode lead terminal are curved in opposite directions. How to connect the fuse wire to

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