JPH1041193A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To weld the external connection terminal of a solid electrolytic capacitor efficiently to the internal terminal thereof comprising an aluminum metal terminal by stabilizing the strength and dissipating heat generated through welding effectively. SOLUTION: Each electrode metal foil is connected with internal terminals, i.e., aluminum metal terminals 12, 14, and wound through a separator to produce a solid electrolytic capacitor which is then encased in a resin case and sealed with a potting resin, e.g. epoxy resin. It is then cut on the sealed side to expose the metal terminals and the potting resin and the exposed metal terminals 12, 14 are connected with external connection terminals 40, 42. The external connection terminals 40, 42 are made by punching a phosphor bronze band into a predetermined shape, bending the punched band and subjecting the punched band thus bent partially to solder plating on the external connecting end side. The external connection terminals are then pressed, on the side to be irradiated with laser light, against the exposed metal terminals 12, 14 and connected through laser welding of a plurality of spots 50 displaced at a predetermined pitch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a solid electrolytic capacitor suitable for surface mounting on a printed circuit board or the like used in a small electronic device, and more particularly to a method of forming an external connection terminal with respect to an internal terminal of a capacitor element. The present invention relates to a method for manufacturing a solid electrolytic capacitor for connection.

[0002]

2. Description of the Related Art Today, as electronic devices become smaller and more portable, high-density mounting technology for electronic components constituting the devices has become indispensable. In other words, for high-density mounting, there is a strong demand for miniaturization of resistors and multilayer ceramic capacitors that are widely used among electronic components.
1.6 mm x
0.8mm (1608 parts) or 1.0mmm × 0.5m
m (1005 parts) have been developed and used.

Under the circumstances where such miniaturization is required, electrolytic capacitors having relatively large capacity characteristics have been further miniaturized from those having cylindrical lead terminals as in the prior art. Leadless rectangular solid electrolytic capacitors suitable for surface mounting have been developed and implemented.

As a method of manufacturing this type of solid electrolytic capacitor, for example, the manufacturing methods shown in FIGS. 7A to 7C are known. 7A to 7C are external perspective views schematically showing main steps in manufacturing a conventional solid electrolytic capacitor for surface mounting, in the order of the steps.

[0007] In FIG. 7A, reference numeral 10 denotes a capacitor element.
Numeral 0 indicates that each aluminum foil for the plus electrode and the minus electrode is wound via a separator. When the aluminum foil is wound, metal terminals 12 and 14 of aluminum round bars, which serve as terminal outlets of the capacitor element 10, are attached in advance by stitching or ultrasonic welding.

[0006] Lead wires (hereinafter referred to as CP wires) 16 and 18 obtained by applying solder plating to a steel-coated copper-coated wire are welded to the aluminum metal terminals 12 and 14, respectively. The capacitor element 10 is connected to a transfer frame 20, which is a conductive metal plate, by a CP on the side to be a positive terminal.
The wire 16 is attached by welding or the like.

[0007] A plurality of capacitor elements 10 attached to the transport frame 20 in a multiple state (not shown) are
For example, the resultant is impregnated with manganese nitrate and fired to form a manganese dioxide layer serving as an electrolytic layer, and then immersed in a chemical solution containing boric acid aqueous solution and ammonia. Then, the aluminum metal terminal 12 of the capacitor element 10 is
The submerged chemical conversion treatment is performed by applying a voltage so that the positive side is a positive potential and the chemical conversion side is a negative potential. This conversion treatment
Forming a withstand voltage film by re-forming so that no portion without a withstand voltage oxide film is formed at the cut end of the cut metal foil (anode foil) or at a connection point between the welded aluminum metal terminal 12 and the metal foil. It is. By cutting the metal foil (anode foil) and welding the aluminum metal terminal 12, the foil area can be increased, and the performance of the product can be improved.

Next, referring to FIG. 7B, after the chemical conversion treatment, the CP wire 16 is cut, the capacitor element 10 is removed from the transport frame 20, and the CP wires 16 and 18 are bent as shown. .

The above-mentioned capacitor element 10 is impregnated with manganese nitrate and baked, so that
Since the heat near 0 ° C. is applied, the solder plating of the CP wire is melted, and the soldering becomes poor if this is done. Had been welded. But in this case,
There is a problem that stress is applied to the product due to chucking or the like at the time of welding the new CP wire.

Further, in FIG. 7C, after the capacitor element 10 is housed in the rectangular resin case 22, the potting resin 2 such as epoxy resin is placed in the resin case 22.
4 is injected to seal the capacitor element 10. After the potting resin 24 is cured, the extra length of the CP wires 16 and 18 is cut, and then the CP wires 16 and 18 are bent again along the side surfaces of the rectangular resin case as shown to complete the process.

In this way, it is possible to obtain a leadless type solid electrolytic capacitor suitable for surface mounting which is used by being mounted on a so-called face bonding substrate and having no through hole through which the lead wire of the electronic component is inserted. .

However, according to the method for manufacturing a solid electrolytic capacitor, the external terminals of the solid electrolytic capacitor are:
Since bent CP wires 16 and 18 are used, a fine work process of welding CP wires 16 and 18 to aluminum metal terminals 12 and 14 is required. Further, when a voltage is applied to the CP wire 16 while the chemical conversion solution is creeping up during the chemical conversion treatment in the liquid, the solder plating portion, the copper coating portion, etc. of the CP wire are dissolved (corroded), and in some cases, the CP wire itself is cut. Therefore, there is a problem that the capacitor element 10 must be held at a position where the chemical conversion liquid does not crawl on the CP line, and the liquid level of the chemical conversion liquid must be strictly controlled.

From such a viewpoint, the present applicant has previously impregnated a capacitor element formed by winding each metal foil for a positive electrode and a negative electrode with a separator interposed therebetween with an electrolytic solution and firing it. In a method of manufacturing a solid electrolytic capacitor in which a chemical treatment is applied and this capacitor element is housed in a resin case and sealed with a potting resin such as epoxy resin, a metal terminal made of only aluminum is attached to the bipolar electrode foil and connected to the transport frame And a step of cutting the sealing side of the resin case at a predetermined location so that the metal terminal and the potting resin are exposed after sealing the resin case, and a step of connecting an external connection terminal to the metal terminal exposed by the cutting. A method for manufacturing a solid electrolytic capacitor characterized by the provision of a solid electrolytic capacitor was developed, and a patent application was filed (Japanese Unexamined Patent Publication No.
-286308).

That is, the method for manufacturing a solid electrolytic capacitor according to the present invention is configured as shown in FIGS. First, in FIG. 3A, a capacitor element 10 to which a longer aluminum metal terminal 12 is fixed by welding or the like is attached to a transfer frame 20. This capacitor element 10 is immersed in an electrolytic solution, fired, and then subjected to a chemical conversion treatment as in the conventional case. The capacitor element 10 is housed in a molded and tapered rectangular resin case 32. At this time, the alignment between the capacitor element 10 and the resin case 32 does not require a strict alignment accuracy, and can be easily inserted.

Next, in FIG. 8B, after the capacitor element 10 attached to the carrier frame 20 is housed in a resin case 32, molten epoxy resin 24 is further injected, and the epoxy resin 24 is cured. It is in the sealed state.

Thereafter, in FIG. 8C, the lower side of the tapered portion of the resin case 32 is cut together with the epoxy resin 24 and the aluminum metal terminals 12 and 14 so as to have a predetermined length. The aluminum metal terminals 12 and 14 are exposed as shown in FIG.

In FIG. 8 (D), external connection terminals 26 and 28 formed by processing metal plates are respectively attached to the aluminum metal terminals 12 and 14 exposed in the cutting step.
The solid electrolytic capacitor can be completed by attaching by ultrasonic welding, laser welding, or the like.

[0018]

However, in the method for manufacturing a solid electrolytic capacitor described above, the conventional C
Although various problems in the processing of P-line are solved,
Many problems remain to be solved regarding connection with the external connection terminal.

That is, even in the above-described method for manufacturing a solid electrolytic capacitor, when the solid electrolytic capacitor is connected to the internal terminals 12 and 14, particularly when it is welded, the external terminals 26 and 28 are used in a stable manner. In addition, taking into account the effect of the temperature rise during welding on the surroundings of the internal terminals, for example, gasification of a part of the epoxy resin, perform safe and appropriate work efficiently and efficiently, and improve product production efficiency. Was required.

Therefore, an object of the present invention is to stabilize the strength when welding an external connection terminal to an internal terminal made of an aluminum metal terminal of a solid electrolytic capacitor and to effectively radiate heat generated during welding. An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor capable of achieving efficient welding.

[0021]

In order to achieve the above object, a method for manufacturing a solid electrolytic capacitor according to the present invention is characterized in that an aluminum metal terminal as an internal terminal is provided on each metal foil for a positive electrode and a negative electrode. Connected, winding each metal foil through a separator to form a capacitor element and forming a solid electrolyte layer between each metal foil, storing this capacitor element in a resin case and using a potting resin such as epoxy resin. Sealing, and then cutting the sealing side of the resin case so that the metal terminal and the potting resin are exposed, and in a method for manufacturing a solid electrolytic capacitor comprising connecting an external connection terminal to the exposed metal terminal,
The external connection terminal is formed by punching a band of phosphor bronze into a predetermined shape, bending the same, and partially plating the external connection end side with the solder light, and the external connection terminal is exposed on the laser light irradiation surface of the external connection terminal. A plurality of spots, each of which is pressed and contacted in parallel with the metal terminal and is connected by laser welding of a plurality of spots each of which is deviated by a predetermined pitch.

In this case, it is preferable that the surface of the external connection terminal formed by punching and bending the phosphor bronze band into a predetermined shape is subjected to a semi-bright nickel plating process.

Further, in the sealing portion of the resin case cut so that the aluminum metal terminal and the potting resin are exposed, the cut surface of the aluminum metal terminal is formed slightly lower than the cut surface of the sealing resin. In laser welding with an external connection terminal made of phosphor bronze, an air layer (gap) is provided between the aluminum metal terminal and the phosphor bronze terminal, so that proper and stable welding can be achieved.

In the laser welding of the plurality of spots, the first spot and the second and subsequent spots are each displaced by a predetermined pitch at a required time interval, and each spot is immediately shifted immediately before the main welding current is output. It is preferable to output a preheating current, and to set the height of the second and subsequent spots at the time of main welding at a higher value than the height of the first spot at the time of main welding.

[0025]

Next, an embodiment of a method for manufacturing a solid electrolytic capacitor according to the present invention will be described in detail with reference to the accompanying drawings.

First, in the method for manufacturing a solid electrolytic capacitor of the present invention, the step of subjecting the capacitor element to a chemical conversion treatment in a liquid comprises:
This is the same as the above-described conventional method for manufacturing a solid electrolytic capacitor. That is, also in the present embodiment, FIG.
As shown in (C), the capacitor element 10 is immersed in an electrolytic solution and fired to form a solid electrolyte layer, housed in a required resin case 32, and then injected with the molten epoxy resin 24 into the resin case 32. When the epoxy resin 24 is cured and sealed, the lower side of the resin case 32 is cut together with the epoxy resin 24 and the aluminum metal terminals 12 and 14 so as to have a predetermined length. Metal terminal 1
Let 2 and 14 be exposed.

Therefore, in the present invention, the aluminum metal terminal 12 exposed at the sealing portion of the resin case 32,
The external connection terminals 40 and 42 are welded to the 14 as described below.

1. Configuration of External Connection Terminal FIG. 1 is a perspective view showing a schematic configuration of an embodiment of the external connection terminals 40 and 42 used in manufacturing the solid electrolytic capacitor according to the present invention. In FIG. 1, a pair of external connection terminals 40 and 42 of the present embodiment are provided on a pair of left and right external connection terminals with respect to a phosphor bronze band having a required continuous width and thickness (t). 40 and 42 are continuously punched into a predetermined shape and bent.

That is, one side surface (upper surface in the drawing) of the external connection terminals 40 and 42 is a laser beam irradiation surface for laser welding, and the transfer frame 4 made of phosphor bronze is used.
One end side 40 connected to narrow neck 45 which can be separated from and connected to 4
a and 42a are configured as connecting portions with the aluminum metal terminals 12 and 14 (FIG. 2). Further, the external connection terminals 40, 4
The other end side 40b, 42b of 2 is configured as a connection portion for surface mounting on a printed circuit board or the like, and is subjected to a solder plating process to facilitate the connection.

However, one side surface of each of the external connection terminals 40 and 42 is subjected to a semi-glossy nickel (Ni) plating process so that the reflectivity of the laser light irradiation surface is appropriately adjusted so that the laser light is irradiated. The absorptance can be improved. For example, when a glossy nickel plating treatment is applied to the laser light irradiation surface, there is a problem that the reflectance of the irradiation surface increases and the laser light absorption rate deteriorates. On the other hand, if the surface irradiated with laser light is subjected to a matte nickel plating treatment, the reflectance of the irradiated surface is lowered and the absorptivity of laser light is improved, but it is easy to absorb dirt due to finger grease just by touching it. In addition, there is a problem in that dirt due to finger oil is conspicuous, and in this case, even if the oil of the machine is slightly adhered, the oil dirt is conspicuous, not only the appearance is deteriorated, but also the discoloration due to humidity occurs, so the commercial value However, there is a problem that it decreases. When performing the partial solder plating on the external connection terminals 40 and 42, it is convenient to perform the semi-bright nickel plating and then partially perform the solder plating.

The external connection terminals 40 and 42 of this embodiment are
The use of phosphor bronze as the material of the alloy means that phosphor bronze performs the most stable welding of dissimilar metals to pure aluminum as the aluminum metal terminals 12 and 14 (FIG. 2) as internal terminals. Because it can be. Also, in this case,
The thickness t of the phosphor bronze is most preferably 0.1 mm in terms of strength when lap welding is performed using a laser beam. That is, when the thickness t is 0.1 mm or less, the strength of the terminal itself becomes insufficient. The thickness t is 0.1 mm or more (for example, 0.15, 0.2 mm, etc.).
In this case, since the thickness of the terminal is large, the energy of the laser beam to be applied is also large, so that the terminal surface temperature is increased in a wide range, and the aluminum metal terminal 1 as an internal terminal
There is a disadvantage that the epoxy resin 24 (FIG. 2) surrounding the portions 2 and 14 (FIG. 2) is affected, for example, a part of the epoxy resin is gasified.

Then, the aforementioned external connection terminals 40, 42
Is carried to the aluminum metal terminals 12 and 14 exposed at the sealing portion of the resin case 32 and welding is performed, it is necessary to add a cleaning step for degreasing and cleaning the external connection terminals 40 and 42 as appropriate. It is.

[0033] 2. Setting of internal terminals (aluminum metal terminals)
Welding condition Then, the external connection terminal configured as 40, 42
Is an aluminum metal terminal 12 as an internal terminal shown in FIG.
The following conditions are required when performing laser welding on 14.

First, the cut surfaces 12a, 14a of the aluminum metal terminals 12, 14 are required to be clean. This is indispensable for improving the adhesion during laser welding.

Next, the aluminum metal terminals 12, 14 are cut against the cut surface 24a of the sealing resin (epoxy resin 24).
Are required to be slightly (δH) lower. Such a process can be easily achieved by performing a chemical polishing process on the cut surfaces 12a, 14a of the aluminum metal terminals 12, 14. With this configuration, the aluminum connection terminals 4 and the external connection terminals 4 made of phosphor bronze can be used.
When welding dissimilar metals 0 and 42, phosphor bronze has a much higher melting point, so the temperature of phosphor bronze when laser bronze is melted by phosphorescence is too high for aluminum. Air layer (gap) between bronze and aluminum
By providing, appropriate and stable welding can be achieved.

In this case, the distance L1 from the cut surface 24a of the epoxy resin 24 to the connection between the aluminum metal terminals 12, 14 and the capacitor element is required to be 0.7 mm or more. That is, if the dimension of the distance L1 is, for example, 0.5 mm or less, as shown in FIG. 3, the molten portion M due to the irradiation of the laser beam L is attached to the Hondara H of the aluminum terminal 12 (14) of the internal terminal. And the sealing resin is gasified, and the external connection terminals 40 (4
This is because good welding with 2) cannot be achieved.

At the time of laser welding, as shown in FIG. 3, the external connection terminals 40 (42) made of phosphor bronze are arranged so as to face the cut surfaces of the aluminum metal terminals 12 and 14 of the resin case 32, respectively. Required metal members 46a,
It is required to use 46b and press firmly against the resin case 32 to perform welding.

In laser welding, it is required to suppress heat conduction to the sealing resin. Therefore, the laser beam is just focused, and as shown in FIG.
In order to enlarge the melting area, that is, the welding area, a plurality of spot welds 50 are respectively displaced by a predetermined pitch.
In this embodiment, the two spot welding is 50,
The larger the deviation distance (pitch) is, the better, but from the viewpoint of heat conduction to the sealing resin, it is optimal that the pitch P between the first spot and the second spot is P = 0.16 mm. . In connection with this, it is optimal to use a leaf spring material made of a material having good heat conduction capable of performing good heat radiation as the metal members 46a and 46b for holding the external connection terminals 40 and 42. (See FIG. 3).

Further, at the time of laser welding, it is better that the welding portion 50 has a deeper melting depth, but, for example, the external connection terminals 4 are formed on the cut surfaces of the aluminum metal terminals 12 and 14.
If you forcibly remove this after welding 0, 42,
As shown in FIG. 5A, it is not preferable that a hole is simply formed in the welding portion 50 of the external connection terminal 40. in this case,
As shown in FIG. 5B, a hole is formed in the welded portion 50 of the external connection terminal 40 and the welded portion 50 of the external connection terminal 40 is removed.
It is preferred that both destruction modes coexist with the part 12b of the aluminum metal terminal 12 adhering to the peripheral edge of the metal terminal 12.

[0040] 3. Operating conditions of welding laser And, in the present invention, upon the laser welding,
Yttrium aluminum garnet laser (hereinafter, referred to as YAG laser) is preferably employed because output waveform control by pulse current waveform setting is possible.

Therefore, in this embodiment, as described above, in order to employ the two-spot welding 50, the output waveform set value of the pulse current for controlling the output of the YAG laser is set as shown in Table 1 below. Set. In Table 1, the amount of height (%) indicates a ratio when the allowable maximum value of the laser beam irradiation current is 100%.

[0042]

[Table 1]

FIG. 6 shows the output waveform of the laser beam energized and controlled by the set pulse current based on Table 1. In this case, the first spot 50a and the second spot 50a
Has a control waveform for preheating (height amount 25%) at the initial stage (sector 1 and sector 6) of spot 50b,
The welding control waveform at the time of main welding is the first spot 50a.
In the case of (2), the height amount is set to 46% in the sector 3, and in the case of the second spot 50b, the height amount of the second spot 50b is set to be high in the sector 8 as 62%. This is due to the welding at the first spot 50a
This is because the nickel plating is melted, phosphor bronze is exposed in a required area, and the absorptivity of laser light by the second spot 50b is lower than that of the first spot 50a. This basically means that the size of the weld lump formed by the first spot 50a and the second spot 50b is set to be equal (see FIG. 5A).

The components of the external connection terminals 40 and 42 described above, the welding conditions for the internal terminals and the like in the resin case in which the capacitor elements for welding the external connection terminals 40 and 42 are housed and arranged, and the laser for laser welding By welding the external connection terminals 40 and 42 to the internal terminals 12 and 14 of the capacitor element based on the light control conditions, the strength is stabilized, the heat generated during welding is effectively radiated, and the efficiency is improved. Welding can be achieved.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention. .

[0046]

As is apparent from the above embodiment, according to the method for manufacturing a solid electrolytic capacitor according to the present invention, aluminum metal terminals as internal terminals are respectively provided on the metal foils for the positive electrode and the negative electrode. Connected, winding each metal foil through a separator to form a capacitor element and forming a solid electrolyte layer between each metal foil, storing this capacitor element in a resin case and using a potting resin such as epoxy resin. Sealing, and then cutting the sealing side of the resin case so that the metal terminal and the potting resin are exposed, and in a method for manufacturing a solid electrolytic capacitor comprising connecting an external connection terminal to the exposed metal terminal,
The external connection terminal is formed by punching a band of phosphor bronze into a predetermined shape, bending the same, and partially plating the external connection end side with the solder light, and the external connection terminal is exposed on the laser light irradiation surface of the external connection terminal. By pressing and abutting in parallel with the metal terminal that was connected by laser welding of a plurality of spots each deviated by a predetermined pitch,
The strength is stable, the heat generated during welding is effectively radiated, and efficient welding can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view of an essential part showing an embodiment of an external connection terminal used in a method for manufacturing a solid electrolytic capacitor according to the present invention.

FIG. 2 is a longitudinal sectional view of a main part showing a state in which the capacitor element is housed and arranged in a resin case in the method for manufacturing a solid electrolytic capacitor according to the present invention.

FIG. 3 is a main part side view showing a state in which an external connection terminal is brought into contact with the solid electrolytic capacitor according to the present invention to perform welding connection.

FIG. 4 is a plan view showing a state in which an external connection terminal is brought into contact with the solid electrolytic capacitor according to the present invention to perform welding connection.

5A and 5B show a welding state of an external connection terminal for performing a welding connection to the solid electrolytic capacitor according to the present invention, wherein FIG. 5A is a plan view and FIG. 5B is a side view.

FIG. 6 is an output waveform diagram of laser light that is energized and controlled by a set pulse current when an external connection terminal is connected in the method for manufacturing a solid electrolytic capacitor according to the present invention.

FIGS. 7A to 7C are external perspective views showing main manufacturing steps in a conventional method of manufacturing a solid electrolytic capacitor in the order of fixing.

8 (A) to 8 (D) are external perspective views showing main manufacturing steps in an improved conventional solid electrolytic capacitor manufacturing method in the fixing order.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Capacitor element 12, 14 Aluminum metal terminal 12a, 14a Cut surface 12b Attachment part 20 Transport frame 24 Potting resin (epoxy resin) 24a Cut surface 32 Resin case 40, 42 External connection terminal 40a, 42a One end side 40b, 42b, etc. End side 44 Transfer frame of phosphor bronze 45 Narrow neck 46a, 46b Metal member 50 Spot welding (welded portion) 50a First spot 50b Second spot

Claims (4)

[Claims] 1. An aluminum metal terminal as an internal terminal is connected to each metal foil for a positive electrode and a negative electrode, and each metal foil is wound via a separator to form a capacitor element and each metal foil. A solid electrolyte layer is formed therebetween, and the capacitor element is housed in a resin case and sealed with a potting resin such as an epoxy resin, and then the sealing side of the resin case is cut so that the metal terminals and the potting resin are exposed. In the method for manufacturing a solid electrolytic capacitor in which an external connection terminal is connected to the exposed metal terminal, the external connection terminal is formed by punching a phosphor bronze band into a predetermined shape, bending the band, and forming an external connection end portion. Side is partially solder-plated, and presses and abuts in parallel with the exposed metal terminal on the laser beam irradiation surface of the external connection terminal. Te method for producing a solid electrolytic capacitor, characterized in that the connection by laser welding a plurality spots respectively by a predetermined pitch offset. 2. A phosphor bronze strip is punched into a predetermined shape.
The laser irradiation surface of the external connection terminal formed by bending
2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is subjected to semi-bright nickel plating. 3. A cut portion of the aluminum metal terminal at a sealing portion of the resin case cut so that the aluminum metal terminal and the potting resin are exposed so as to be slightly lower than a cut surface of the sealing resin. Item 2. A method for producing a solid electrolytic capacitor according to Item 1. 4. In the laser welding of a plurality of spots, the first spot and the second and subsequent spots are each displaced by a predetermined pitch at a required time interval, and the preheating current is immediately before output of the main welding current at each spot. And output
2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the height of the main welding by the second and subsequent spots is set higher than the height of the main welding by the first spot.