JPH04243116A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To provide a highly reliable manufacturing method of a solid electrolytic capacitor by a method wherein a plurality of capacitor elements are laminated together by laser welding under appropriate joint conditions. CONSTITUTION:A plurality of capacitor elements 33 are laminated on the positive mounting part 36 of a comb 34 and, further, the tip part 37 of the anode mounting part 36 of the comb 34 is bent 180 degrees to hold the anode parts 25 of the plurality of capacitor elements 33 tightly. The tightly held anode parts 25 and the comb 34 are jointed together by laser welding to realize an ideal welding state as shown in the Figure (a).

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 which has low impedance in a high frequency range and has good volumetric efficiency.

0002

2. Description of the Related Art In recent years, with the digitalization of electronic equipment, capacitors used in electronic circuits are required to have low impedance, small size, and large capacity in the high frequency range. In the field of electrolytic capacitors, which are characterized by their small size and large capacity, in contrast to conventional dry-type aluminum electrolytic capacitors, tantalum solid electrolytic capacitors, and aluminum solid electrolytic capacitors that use manganese dioxide as a solid electrolyte, we are using polymers of heterocyclic compounds. Many solid electrolytic capacitors that use conductive polymers as solid electrolytes have been proposed as capacitors that can meet this demand, and some have come to be commercialized.

[0003] Low impedance in the high frequency range is achieved by using a conductive polymer, which is a polymer of a heterocyclic compound, as a solid electrolyte, but due to the characteristics of a solid electrolyte, a formation voltage considerably higher than the rated voltage is forced. As a result, the volumetric efficiency of capacitance is lower than that of dry aluminum electrolytic capacitors, and therefore, in order to increase this volumetric efficiency, it is necessary to adopt a laminated structure. Methods for forming a laminated structure have been known for some time, and an example of using a conductive polymer as a solid electrolyte is disclosed in Japanese Patent Laid-Open No. 63-239917.

In this example, as shown in FIGS. 10 and 11, a plurality of protrusions 2 are formed on one side of a band-shaped aluminum etched foil 1, and the predetermined positions of the plurality of protrusions 2 are By forming a resist layer 3 over the entire surface, the protrusion 2 is divided into two parts. Then, on one part (cathode part) divided by the resist layer 3, an aluminum oxide film layer 4 is applied as a dielectric, and a polymer layer 5 made of pyrrole is applied as a polymer layer of a heterocyclic compound that becomes an electrolyte. A graphite layer 6 and a silver paste layer 7 are sequentially formed as conductor layers to constitute a capacitor element plate 8.

Capacitor element plate 8 configured as described above
A plurality of sheets are stacked as shown in FIG. 12(a). In this case, the protrusions 2 of the plurality of capacitor element plates 8 and the protrusions 2
are stacked so that they correspond to each other, and the projections 2 are pressed under high temperature to temporarily dry the silver paste layer 7 on one part (cathode part) 9 separated by the resist layer 3 to form a capacitor element plate 8. One part 9 is fixed to each other and integrated, and the part 10 of the aluminum etched foil 1 corresponding to the other part separated by the resist layer 3 (the anode part shown by the x mark in FIG. 11) is joined together by welding or the like. In this way, the capacitor element body 11 is constructed. Next, one portion (
The outer surface of the plate-shaped cathode terminal 12 is pressed onto the temporarily dried silver paste layer 7 of the cathode part) 9, and the silver paste layer 7
By drying and curing, a plate-shaped cathode terminal 12 is attached to one part (cathode part) 9, and
A similarly plate-shaped anode terminal 13 is attached to the other part (anode part) 10 divided by the resist layer 3 by spot welding, ultrasonic welding, seamer welding, etc. to form a capacitor element, and this capacitor element is covered with a resin exterior. It comprised a multilayer solid electrolytic capacitor.

[0006]

However, the above-described conventional construction method has several drawbacks, particularly the major drawback of poor reliability in the method of connecting the anode portion.

In other words, even if there is no chemical conversion coating on the surface of valve metals such as aluminum, there is a strong oxide coating due to oxidation in the air, so resistance welding and In sonic welding, it is extremely difficult to perform reliable welding by penetrating the multiple layers of oxide film in multiple laminated foils. Furthermore, even if they are apparently bonded, the contact resistance is high and there is a risk that they may peel off during use.

[0008] This is because the conventional welding method requires only a small amount of energy and welds only where the oxide film between adjacent foils is penetrated, and the welded parts, which are the basics of welding, are alloyed together. This is thought to be because the situation is far different from the actual state.

Furthermore, in conventional resistance welding, a current other than the welding current flows during welding, often causing destruction of the oxide film or conductive polymer film.

The present invention solves the above-mentioned problems of the conventional method. In particular, by optimizing the bonding conditions of the anode parts of a plurality of laminated capacitor elements and performing laser welding, a highly reliable solid electrolytic capacitor can be manufactured. The purpose is to provide a manufacturing method.

[0011]

[Means for Solving the Problems] In order to achieve the above object, the method for manufacturing a solid electrolytic capacitor of the present invention involves dividing a foil made of valve metal on which an oxide film is formed with an insulating layer, and A conductive layer consisting of a conductive material layer, a conductive polymer film, a graphite layer, and a silver paint layer is sequentially formed on one part (cathode part) to constitute a capacitor element, and a plurality of these capacitor elements are laminated, One part (cathode part) of the plurality of capacitor elements is laminated and connected to a part of the comb that also serves as an extraction terminal, and the other part (anode part) of the plurality of capacitor elements is connected to another part of the comb. At the same time, the tip of another part of this comb is bent 180 degrees, and the other part (anode part) of the multiple capacitor elements is sandwiched in close contact with each other, and this sandwiched state The other part (anode part) of the plurality of capacitor elements and the comb are connected by laser welding, and the whole is covered with molded resin.

0012

[Function] According to the manufacturing method described above, the other part (anode part) of the capacitor element made of a plurality of laminated valve metals is laminated on another part of the comb that also serves as the lead terminal, and Bend the tip of the part 180 degrees and attach it to the other part of the multiple capacitor elements (
Since the two parts (anode part) are sandwiched in close contact with each other, there is no space gap between the other part (anode part) in the capacitor element made of multiple valve metals.
As a result, when laser welding is used to connect the anode part of a capacitor element made of multiple valve metals to a comb that also serves as a lead-out terminal, it is possible to achieve an ideal welding condition, making it possible to use a highly reliable welding method. This makes it possible to provide a compact, large-capacity solid electrolytic capacitor with low impedance in a high frequency region.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings.

(Example 1) After etching a 100 μm thick aluminum foil, which is a valve metal, by a known method to make it porous, an oxide film is formed on its surface by a chemical conversion treatment, and this chemically converted aluminum foil is A comb-shaped electrode 22 having a protrusion 21 as shown in FIG. 1 is punched out. Further, an insulating layer 23 is provided at a predetermined position of the projection 21 to divide it into a cathode section 24 and an anode section 25. Note that the aluminum foil may be punched out in the metal foil state and then subjected to etching and chemical conversion treatment, but considering productivity,
It is best to use a wide coated foil. Further, the insulating layer 23 may be provided by punching out a chemically formed aluminum foil and then applying an insulating paint, but it is also possible to provide the insulating layer 23 by applying an insulating paint to a predetermined position of the chemically formed aluminum foil. The tape is pasted and then punched out to form a comb-shaped electrode 22 as shown in FIG.
may also be configured.

Next, at least the entire surface of the cathode section 24 is immersed in a chemical solution to repair the cut surface and the oxide film, and then the cathode section 24 of the comb-shaped electrode 22 is immersed in an aqueous solution of manganese nitrate. After that, heat treatment is performed at about 300° C. for 10 minutes to form a conductive material layer 26 made of manganese dioxide as shown in FIG. 2(b). After this, in order to repair the oxide film deteriorated by the heat treatment, it is better to carry out re-forming, but this re-forming may be omitted.

Next, as shown in FIG. 3, an electrolytic polymerization solution 27 in which pyrrole, which is electrolytically polymerized to form a conductive polymer, and triisopropylnaphthalene sulfonic acid as a supporting electrolyte are dissolved in water, is used also as a counter electrode. The comb-shaped electrode 2 is placed in a container 28 made of stainless steel.
2 to the middle of the insulator layer 23, and then comb-shaped electrode 2.
The tip of the stainless steel electrode 29 with a shape corresponding to 2 is the cathode part 2.
The stainless steel electrode 29 is used as an anode and the container 2 is in contact with a portion of the insulating layer 23 as close as possible to the conductive material layer 26 of the container 2.
Electrolytic polymerization is performed by applying a voltage using 8 as a cathode, and a conductive polymer film 30 is formed on the conductive material layer 26 as shown in FIG. 2(b).

Further, on top of this conductive polymer film 30, as shown in FIG.
As shown in (b), the graphite layer 31 is
and a silver paint layer 32 are sequentially formed. In this case, since the graphite layer 31 is thin, a normal dipping and baking method is sufficient, but in the case of the silver paint layer 32, the dipping method thickens the bottom part, which is detrimental to lamination, so a uniform method such as a printing method is not suitable. Application methods are preferred. In the comb-shaped electrode 22 thus completed, C-
The protrusion 21 is cut along the C line to form a single capacitor element 33. In this case, there is a method of stacking the comb-shaped electrodes 22 as they are, but this method is not advisable in terms of production yield and subsequent assembly steps. For example, if a single capacitor element 33 has a yield of 90%, if five single capacitor elements 33 are laminated in the form of a comb-shaped electrode 22, the yield will be 59%. Therefore, it is obvious that it is more advantageous to judge whether a single capacitor element 33 is good or bad and to stack them.

Next, a single capacitor element 33 is stacked and installed on a comb (metal frame) 34 which also serves as a lead-out terminal as shown in FIGS. 4 and 5(a) and 5(b). , the thickness of the comb 34 which also serves as a lead-out terminal is 0.1.
An iron base material obtained by punching out a flat plate of mm in thickness was plated with 3 μm of copper and 1 μm of tin. This comb 34 is connected in advance to the cathode mounting portion 35 and the anode mounting portion 36 in FIG. 5(a).
The part indicated by the broken line is bent at a right angle, and a small amount of silver paint is applied as an adhesive between the cathode part 24 of the capacitor element 33 and the comb 34, and a single capacitor element 3 is assembled.
3 are stacked and loaded. Furthermore, the tip 37 of the anode mounting part 36 of the comb 34 is further bent by 90 degrees, that is, the anode mounting part 36 is bent by 180 degrees as a whole, as shown in FIG.
As shown in FIG. 6B and FIG. 6, the anode portions 25 of a plurality of laminated capacitor elements 33 are sandwiched between combs 34 in close contact with each other. And in this state com 3
Laser welding was performed from the upper part of the tip portion 37 of the anode mounting portion 36 of No. 4. In this case, two or three welding points were used.

In order to perform this laser welding well, the valve metal that makes up the plurality of aluminum foils at the spot where the laser beam is irradiated and the metal that makes up the comb 34 that also serves as the lead-out terminal are melted and mixed uniformly. Or it needs to be in an alloyed state. The comb 34, which also serves as the lead-out terminal, is generally made of iron as a base material, and is made of a metal that easily alloys with solder.
For example, valve metals are plated with copper, nickel, tin, etc., and the melting point of iron is 1535°C, while the melting point of aluminum is 660°C and the melting point of tantalum is 2996°C.
The melting points of iron and valve metal are far different, as the melting point of niobium is 2468°C, so if you try to melt them both at the same time, the metal with a lower melting point will evaporate and be lost, causing phenomena such as holes to occur. . In addition to this, energy is also required to break through the oxide films formed on the surfaces of the plurality of aluminum foils.

Furthermore, when the capacitor elements 33 are laminated, the thickness of the anode part 25 is 500 μm in total if, for example, five sheets of 100 μm aluminum foil are stacked, whereas the thickness of the cathode part 24 is made of conductive polymer. Including the thickness of the membrane 30 and the conductive layers 31 and 32, each sheet has a thickness of approximately 0.5 mm, and for five sheets the thickness reaches 2.5 mm, so the aluminum foils constituting the anode section 25 to be welded are stacked as they are. If only there is a space of about 0.4 mm, there will be a space of about 0.4 mm.

However, in one embodiment of the present invention,
As described above, the tip portion 37 of the anode mounting portion 36 of the comb 34 which also serves as a lead-out terminal is further bent 90 degrees, that is, the anode mounting portion 36 is bent 180 degrees as a whole, as shown in FIG.
b) and as shown in FIG.
When laser welding is performed from the upper part of the tip part 37 of the anode mounting part 36, an ideal welding state can be obtained. That is, as shown in FIG. 7(a), the anode mounting portion 3 of the comb 34
6 and the anode part of the capacitor element 33 (
In this example, the aluminum foil) 25 is melted and integrated into 3
8, and dissolution traces can be seen not only from the laser incident side but also from the back surface. FIG. 8 shows a component analysis diagram of this dissolved portion using an X-ray microanalyzer, and it can be seen from FIG. 8 that Al, Fe, Cu, and Sn are uniformly dissolved. In addition, if the laser beam is too strong, the low melting point metal will mainly evaporate and the hole 3
9 becomes open. For example, when using an SI (step index) type optical fiber, it tends to dissolve widely and shallowly, so if you try to dissolve it all the way to the bottom, as shown in Figure 7.
(b) is likely to occur. Moreover, if a space gap exists between the aluminum foils of the anode part 25 of the capacitor element 33 stacked in plurality, it is impossible to uniformly melt the aluminum foils, so that welding cannot be performed or a similar state occurs. On the other hand, if the laser beam is too weak, not only will it not be possible to melt all the way to the bottom, but it will also be impossible to confirm whether welding is appropriate.

Regarding the welding conditions for laser welding in one embodiment of the present invention, first, the YAG laser method was selected as the oscillation method because the YAG laser method is more suitable for low energy than the carbon dioxide laser method. In order to continuously supply the laser beam mode with minute energy to a small spot and to melt multiple pieces of metal deeply in a small area, instead of using SI (step index) type optical fiber, we used GI ( A graded index) type optical fiber was used.

In one embodiment of the present invention, the metal in the anode mounting portion 36 of the comb 34 and the capacitor element 3
After laser welding the anode part 25 in 3, the silver paint layer 32 constituting the cathode part is cured, and the comb 34 is installed in a molding die, and after molding with epoxy resin, the terminal part is cut, I took out the solid electrolytic capacitor. Figure 9 shows the appearance of this solid electrolytic capacitor. The anode terminal 41 and the cathode terminal 42 in this solid electrolytic capacitor 40 utilize the above-mentioned comb 34 as they are.In this case, if the anode terminal 41 and the cathode terminal 42 are bent along the molding resin, You can get a capacitor.

(Embodiment 2) The metal in the anode mounting portion 36 of the comb 34 and the anode portion 25 in the capacitor element 33 are welded by laser welding. In this case, laser welding is SI
A solid electrolytic capacitor was manufactured under the same conditions as in Example 1 except that a (step index) type optical fiber was used.

(Comparative Example) An attempt was made to manufacture a solid electrolytic capacitor under the same conditions as in Example 1, except that the metal in the anode mounting portion 36 of the comb 34 and the anode portion 25 in the capacitor element 33 were welded by resistance welding. However, it was difficult to weld the plurality of aluminum foils constituting the anode section 25 by resistance welding, and it was not possible to construct a solid electrolytic capacitor.

Initial characteristics and thermal shock tests were conducted for 10 solid electrolytic capacitors each of Example 1 and Example 2, which were manufactured by laminating five sheets of aluminum foil with protrusions 21 having dimensions of 3 x 7 mm at a formation voltage of 28 V. (Hold at -40℃ for 30 minutes, 10
The results of a reliability test (a test in which holding at 5° C. for 30 minutes was alternately repeated 100 times) were as shown in (Table 1) and (Table 2).

[0027]

[Table 1]

[0028]

[Table 2]

As is clear from the above (Table 1) and (Table 2), in Example 1 shown in (Table 1), the high frequency region (
500kHz), but in Example 2 shown in (Table 2), the impedance after the test was seen to be significantly higher.

Note that in the above embodiment, the anode portion 25
I explained about the one made of aluminum foil,
The valve metal foil is not limited to this, and may be made of other valve metal foils, such as tantalum or niobium. Furthermore, although the conductive polymer film 30 has been described as being made of a conductive polymer made of polypyrrole, it may also be made of other conductive polymers such as polyfuran or polythiophene, depending on the manufacturing conditions. The mere difference does not impair the requirements of the present invention.

[0031]

[Effects of the Invention] As described above, according to the method of manufacturing a solid electrolytic capacitor of the present invention, the other part (anode part) of the capacitor element made of a plurality of laminated valve metals is connected to another part of the comb which also serves as a lead terminal. At the same time, the tip of another part of this comb is bent 180 degrees and the other part (anode part) of the multiple capacitor elements is sandwiched in close contact with each other. There is no longer a space gap between the other part (anode part) of the capacitor element made of valve metal, and as a result, the anode part of the capacitor element made of multiple valve metals and the comb that also serves as the lead-out terminal can be connected by laser welding. When connecting,
Since ideal welding conditions can be achieved, a highly reliable welding method can be obtained, and thereby a small, large-capacity solid electrolytic capacitor with low impedance in a high frequency region can be provided.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a comb-shaped electrode having a plurality of protrusions used in an example of the present invention.

[Figure 2] (a) An enlarged view of the protrusion of a comb-shaped electrode that forms a capacitor element by forming a conductive polymer film or a conductor layer (b)
) A-A cross-sectional view in (a)

FIG. 3 is a schematic diagram of an electrolytically polymerized layer forming a conductive polymer film in an example of the present invention.

[Fig. 4] A cross-sectional view of a comb (metal frame) that also serves as a pull-out terminal used in an example of the present invention.

FIG. 5: (a) A partially enlarged view of the comb shown by line B-B in FIG. 4; (b) A schematic diagram showing a state in which capacitor elements are laminated and filled in the comb portion in (a).

FIG. 6 is a side cross-sectional view of a state in which a plurality of capacitor elements according to the embodiment of the present invention are stacked together, as shown by line D-D in FIG. 5(b).

FIG. 7: (a) A cross-sectional view showing an ideal fusion welding state of the anode part by laser welding of the present invention; (b) A cross-sectional view showing an unsatisfactory welding state of Example 2 of the present invention.

[Figure 8] Graph showing component analysis of the melted part in laser welding of the present invention using an X-ray microanalyzer

[Fig. 9] A perspective view showing the appearance of a solid electrolytic capacitor manufactured in an example of the present invention.

FIG. 10 (a) Enlarged view of a protrusion provided on the side of an aluminum etched foil showing a conventional example (b) A sectional view taken along the line E-E in (a)

[Fig. 11] A plan view of an aluminum etched foil with multiple protrusions, showing a conventional example.

[Fig. 12] (a) Side view of a state in which multiple capacitor elements are stacked, showing a conventional example. (b) A plan view of the same.

[Explanation of symbols]

22 Comb-shaped electrode 23 Insulator layer 24 Cathode part 25 Anode part 26 Conductive material layer 30 Conductive polymer membrane 31 Graphite layer 32 Silver paint layer 33 Capacitor element 34 com 36 Anode mounting part 37 Tip of anode mounting part

Claims (1)

[Claims] Claim 1: A foil made of valve metal on which an oxide film is formed is divided by an insulating layer, and one of the divided parts (cathode part)
A conductive layer consisting of a conductive material layer, a conductive polymer film, a graphite layer, and a silver paint layer is sequentially formed on the capacitor element to form a capacitor element. One part (cathode part) is laminated and connected to a part of the comb that also serves as an extraction terminal, and the other part (anode part) of the plurality of capacitor elements is laminated to another part of the comb. The tip of another part of the comb is bent 180 degrees, and the other part (anode part) of the plurality of capacitor elements is sandwiched in a state in which they are in close contact with each other, and the plurality of capacitor elements in this sandwiched state are A method of manufacturing a solid electrolytic capacitor in which the other part (anode part) and the comb are connected by laser welding, and the whole is covered with molded resin.