JPH07226336A - Method for manufacturing solid electrolytic capacitor - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor, which can obtain a package having excellent airtightness. [Structure] A capacitor element 21 and a lead frame 22 protruding from a side surface of the capacitor element 21 are covered with a mold resin before a resin sheathing.
The projecting portion of the lead frame 22 projecting from the side surface of the capacitor element is shielded by the lower bakelite plate 26 and the silicon rubber 28 provided on the upper bakelite plate 29, and a voltage is applied in a high temperature and high humidity atmosphere to form a capacitor element. 21 is aged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor used in various electronic devices.

[0002]

2. Description of the Related Art In recent years, with the progress of electronic equipment, electronic parts have been made into chips, and it has become mainstream to assemble electronic circuits by surface mounting. Therefore, of course, the solderability of the lead terminals of the chip parts is required,
It has become necessary to have heat resistance to withstand a high temperature during soldering for a long time. In the field of electrolytic capacitors, which have been conventionally said to have poor heat resistance, surface mountable chip components are becoming mainstream due to advances in materials and technology. For example, as shown in FIG. 7, there is known a solid electrolytic capacitor in which a capacitor element is coated with a molding resin together with lead frames forming an anode terminal 1 and a cathode terminal 2 and a resin sheath 3 is applied.

[0003]

However, in the solid electrolytic capacitor provided with such a resin outer package 3, the airtightness of the outer package is lowered by being exposed to a high temperature during soldering at the time of surface mounting, so that the external enclosure is not exposed. Since oxygen and water vapor in the air penetrate into the inside, it often damages the internal capacitor element and causes deterioration of characteristics. The possible reasons for this are as follows. That is, in a solid electrolytic capacitor, treatment at a high temperature in the manufacturing process, treatment with a reagent such as acid or alkali, and deterioration of the anodized film due to mechanical stress occur, so aging treatment for repairing the anodized film is necessary. However, conventionally, before coating the capacitor element with the mold resin, the aging treatment is performed by applying a voltage in an atmosphere of high temperature and high humidity of 85 ° C. or higher.

However, in the conventional aging method, not only the capacitor elements but also the lead frames forming the anode terminal 1 and the cathode terminal 2 are exposed to a high temperature and high humidity atmosphere of 85 ° C. or higher, and therefore the lead frame An oxide film is also formed on the surface. When the capacitor element and the lead frame are covered with the mold resin in the next step with the oxide film formed on the lead frame surface in this manner, the adhesive strength between the mold resin and the lead frame is When the solid electrolytic capacitor in such a state is soldered for surface mounting on an electronic device, this solid electrolytic capacitor is exposed to high temperatures during soldering. Since it is exposed, the expansion and contraction of the lead frame and the molding resin occur at the bonding surface between the two, resulting in a void in the oxide film formed on the surface of the lead frame, and through this void. When oxygen and water vapor in the air penetrate inside, it damages the internal capacitor element and deteriorates the characteristics. Cormorants had a problem.

The present invention solves the above-mentioned problems of the prior art. When the capacitor element and the lead frame protruding from the side surface of the capacitor element are covered with a mold resin to form a resin exterior, the exterior is airtight. It is an object of the present invention to provide a method for producing a solid electrolytic capacitor, which is excellent in

[0006]

In order to achieve the above object, a method of manufacturing a solid electrolytic capacitor according to the present invention comprises a predetermined surface of an anodized film in a valve metal having an anodized film serving as a dielectric formed on the surface thereof. Providing an insulating strip in a part to divide the valve metal into an anode part and a cathode part, and sequentially forming a conductive substance layer, a conductive polymer layer and a conductor layer on the anodic oxide film of the cathode part. A capacitor element constituted by, a lead frame connected to the anode part and the cathode part of the capacitor element, a resin exterior for coating the capacitor element and the lead frame protruding from the side surface of the capacitor element with a mold resin, Before coating with the mold resin, in a hot and humid atmosphere with the protruding portion of the lead frame protruding from the side surface of the capacitor element shielded. It is obtained to perform the aging of the capacitor element by applying a pressure.

[0007]

According to the above-described method for manufacturing a solid electrolytic capacitor of the present invention, the lead frame protruding from the side surface of the capacitor element before the capacitor element and the lead frame protruding from the side surface of the capacitor element are covered with the molding resin. Since the aging of the capacitor element is performed by applying a voltage in a hot and humid atmosphere with the protruding portion of the capacitor shielded, the protruding portion of the lead frame protruding from the side surface of the capacitor element during this aging It is no longer exposed to a hot and humid atmosphere.

As a result, an oxide film is not formed on the projecting portion of the lead frame as in the conventional case. Therefore, in the next step, the capacitor element made of the mold resin and the lead frame projecting from the side surface of the capacitor element are formed. The adhesive strength between the mold resin and the lead frame does not deteriorate even when the lead frame is coated, and therefore, when the solid electrolytic capacitor is surface-mounted on an electronic device, the lead frame is soldered. Even if expansion and contraction occur between the adhesive surface and the mold resin, the conventional voids will not occur, so there will be no deterioration of the capacitor characteristics due to the ingress of oxygen or water vapor in the air into the capacitor. ,
It is possible to obtain the one having excellent airtightness of the exterior.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. First, as shown in FIG. 2, the surface of the anodic oxide film 11 in the valve metal 12 made of an aluminum chemical conversion foil having a thickness of 100 μm, which is roughened by etching and has an anodized film 11 serving as a dielectric formed on the surface, An insulating material strip 13 made of a strip-shaped insulating film having heat resistance is provided at a predetermined portion, and the valve metal 12 is attached to the anode portion 1.
4 and cathode part 15.

Then, as shown in FIGS. 1A and 1B, a conductive material layer 16 made of a thin manganese oxide material layer is formed on the anodic oxide film 11 of the cathode portion 15, and then alkylnaphthalene sulfonic acid is formed. Electrolytic polymerization was performed in an emulsion containing pyrrole with salt as a supporting electrolyte to form a conductive polymer layer 17 of polypyrrole on the conductive material layer 16.

Further, a conductor layer 20 composed of a graphite layer 18 and a silver paint layer 19 was successively formed thereon, whereby a capacitor element 21 as shown in FIGS. 1A and 1B was obtained. The insulating strip 13 is formed by applying an adhesive 13a and adhering it.

Next, an iron base material having a thickness of 0.1 mm is punched into the shape of the lead frame 22 shown in FIG. 3 by a press to form a copper metal layer of copper plating having a thickness of 3 μm on the surface thereof, and thereafter, A lead alloy 22 was formed by forming a solder alloy layer of solder plating having a thickness of 1 to 10 μm. Then, as shown in FIG. 4A, the lead frame 22 has a thickness other than a predetermined portion 23 on the surface (portion where the resin coating with the mold resin is hatched in FIGS. 4A and 4B). Mask with a mask material made of 1 mm butadiene rubber, and polish the other parts by alumina sand with dry sand blast method until the solder alloy layer is completely removed to expose the copper metal layer Only the portion 23 of was roughened.

This partially roughened lead frame 2
After a small amount of a conductive adhesive was applied to the position 24 corresponding to the cathode portion 15 on the upper surface 2, the capacitor element 21 was placed by stacking it as shown in FIG. 4B. Furthermore, the anode part 1
On the 4 side, laser welding is performed from above the anode presser 25 to join the anode part 14 and the cathode part 15 of the capacitor element 21 to the lead frame 22 as shown in FIG. 4B.
Connected on.

Since the anodic oxide film of the capacitor element 21 fixed on the lead frame 22 has been deteriorated by various stresses in the above process, the anodic oxide film is restored before the resin coating with the molding resin. It is necessary to perform an aging process for this.

This aging treatment is carried out by cutting the dotted line portion of the lead frame 22 shown in FIG. 4B on the bakelite plate 26 containing cloth having the groove portion 26a shown in FIG. 5A to separate the anode portion 14 side. Place the lead frame 22
Then, on the lower bakelite plate 26 on which the lead frame 22 is placed, the silicon rubber 28 in which the contact pins 27 for voltage application at the time of aging as shown in FIG. The bakelite plate 29 is placed so that the silicone rubber 28 is on the lower side.

In this case, the upper bakelite plate 29 is also provided with a groove portion 29a having the same width as the groove portion 26a provided on the lower bakelite plate 26, and the widths of these groove portions 26a, 29a are the capacitor elements. It is the same as the width between both side surfaces of 21. Due to such a dimensional relationship, in a state where the upper bakelite plate 29 is placed on the lower bakelite plate 26, the leads in which the silicon rubber 28 of the upper bakelite plate 29 projects from the side surface of the capacitor element 21. The protruding portion of the frame 22 is shielded.

Then, as shown in FIG. 5C, after placing the upper bakelite plate 29 on the lower bakelite plate 26, a clip 30 presses the lower bakelite plate 26 and the upper bakelite plate 29. Fix and these 8
The sample was placed in an atmosphere having a relative humidity of 90% at a temperature of 5 ° C. and 105 ° C. and a voltage of 125% of the rated voltage was applied for 1 hour to perform an aging treatment.

In this aging process, the protruding portion of the lead frame 22 protruding from the side surface of the capacitor element 21 is the silicon rubber 28 of the upper bakelite plate 29.
By this, the temperature is set to 85 ° C. and 105 ° C. and the state is isolated from the atmosphere having a relative humidity of 90%, so that the oxide film is not formed on the protruding portion of the lead frame 22.

Next, as shown in FIG. 6, the capacitor element 2
1 and the lead frame 22 protruding from the side surface of the capacitor element 21 are covered with a mold resin to form a resin sheath 3
1 is performed, but in this case, molding is performed using a molding resin made of an epoxy resin by the transfer molding method. And after this molding is completed,
Resin burrs at the time of molding are removed by sandblasting using resin beads as an abrasive, and then the lead frame 22
Was cut at a predetermined size to obtain individual solid electrolytic capacitors.

In the above-described embodiment of the present invention, the protruding portion of the lead frame 22 protruding from the side surface of the capacitor element 21 is shielded by the lower bakelite plate 26 and the silicone rubber 28 during the aging process. Therefore, the projecting portion of the lead frame 22 is not exposed to the high temperature and high humidity atmosphere, and thus the oxide film is not formed on the projecting portion of the lead frame 22. Even when the capacitor element 21 and the lead frame 22 projecting from the side surface of the capacitor element 21 are covered with a certain mold resin, the adhesive strength between the resin exterior 31 and the lead frame 22 does not decrease.

As a result, when the solid electrolytic capacitor is soldered to be surface-mounted on an electronic device, a void is generated even if expansion and contraction occur between the lead frame 22 and the resin outer package 31. Therefore, the deterioration of the characteristics of the capacitor due to the invasion of oxygen and water vapor in the air into the inside of the capacitor is eliminated.

The evaluation of the airtightness of the exterior of the solid electrolytic capacitor in the above-described embodiment of the present invention was carried out by heat treatment in which the solid electrolytic capacitor was left in a constant temperature bath at 250 ± 5 ° C. for 5 minutes and then taken out at room temperature, which was repeated three times. The ones were tested by the following autoradiographic exterior tightness test. That is, the sample of the capacitor under test is used as the radioactive isotope Kr8.
After holding in an atmosphere of an inert gas pressurized to 7 MPa including 5 for 30 minutes, the amount of outside air taken into the resin outer package 31 is quantified by measuring the amount of radiation held by each capacitor sample, Then, it was tested by an exterior airtightness test in which an exterior airtightness broken sample was detected by exposing on a photographic film.

The test results are shown in (Table 1), in which the number of defects with respect to the population of the test sample is expressed as a fraction. Further, as a comparative example, a solid electrolytic capacitor in which the projecting portion of the lead frame 22 projecting from the side surface of the capacitor element 21 is not shielded at all is used. A test was conducted by a test, and this test result is also shown in (Table 1) in which the number of defects with respect to the population of the test sample is expressed as a fraction.

[0024]

[Table 1]

As is clear from (Table 1), the number of defects was zero in the solid electrolytic capacitor in one example of the present invention, while the number of defects was 3 in the solid electrolytic capacitor of the comparative example.
There were 12 or 12.

[0026]

As described above, according to the method for manufacturing a solid electrolytic capacitor of the present invention, before the capacitor element and the lead frame protruding from the side surface of the capacitor element are covered with the molding resin, the capacitor element is removed from the side surface of the capacitor element. With the protruding part of the protruding lead frame shielded,
Since the capacitor element is aged by applying a voltage in a hot and humid atmosphere, the protruding portion of the lead frame protruding from the side surface of the capacitor element is exposed to the hot and humid atmosphere during this aging. That will disappear.

As a result, an oxide film is not formed on the projecting portion of the lead frame as in the conventional case. Therefore, in the next step, the capacitor element made of mold resin and the lead frame projecting from the side surface of this capacitor element are formed. The adhesive strength between the mold resin and the lead frame does not deteriorate even when the lead frame is coated, and therefore, when the solid electrolytic capacitor is surface-mounted on an electronic device, the lead frame is soldered. Even if expansion and contraction occur on the bonding surface between the resin and the mold resin, the conventional voids will not occur, so there will be no deterioration of the capacitor characteristics due to ingress of oxygen or water vapor in the air into the capacitor. ,
It is possible to obtain the one having excellent airtightness of the exterior.

[Brief description of drawings]

1A is a plan view of a capacitor element in a solid electrolytic capacitor showing an embodiment of the present invention, FIG. 1B is a sectional view taken along the line AA ′ in FIG.

FIG. 2 is a perspective view of an aluminum conversion foil forming the same capacitor element.

FIG. 3 is a plan view showing the shape of a lead frame used in the capacitor.

FIG. 4A is a partially enlarged plan view of the lead frame, and FIG. 4B is a partially enlarged plan view showing a state in which a capacitor element is mounted on the lead frame.

5A is a partial perspective view showing a state in which a lead frame having a capacitor element is placed on a lower bakelite plate, FIG. 5B is a partial perspective view showing an upper bakelite plate, and FIG. 5C is a lower bakelite. Side view showing the aging state of the capacitor element using the plate and the upper Bakelite plate

FIG. 6 is a plan view showing a state in which the capacitor element and a lead frame are covered with resin.

FIG. 7 is a perspective view showing a conventional solid electrolytic capacitor.

[Explanation of symbols]

 11 Anodized Film 12 Valve Metal 13 Insulator Band 14 Anode 15 Cathode 16 Conductive Material Layer 17 Conductive Polymer Layer 20 Conductor Layer 21 Capacitor Element 22 Lead Frame 31 Resin Exterior

Claims (1)

[Claims] 1. A valve metal is divided into an anode part and a cathode part by providing an insulating band portion at a predetermined portion of the surface of the anodic oxide film in the valve metal having a anodic oxide film as a dielectric formed on the surface thereof. And a conductive material layer on the anodized film of the cathode part,
A capacitor element formed by sequentially forming a conductive polymer layer and a conductor layer, a lead frame connected to an anode part and a cathode part of the capacitor element, and the capacitor element and a side surface of the capacitor element protruding from the side surface. The lead frame is coated with a mold resin, and a voltage is applied in a hot and humid atmosphere with the projecting portion of the lead frame projecting from the side surface of the capacitor element being shielded before coating with the mold resin. A method for manufacturing a solid electrolytic capacitor in which the aging of the capacitor element is performed by the above.