JPH03109713A - Solid-state capacitor - Google Patents

Abstract

PURPOSE:To improve high temperature durability by specifying a ratio of oxygen permeability of a sheathing base material for sheathing a capacitor element in which part of electrodes for holding a dielectric material is polypyrrole to an average thickness. CONSTITUTION:A capacitor element 1 in which at least part of electrodes for holding a dielectric material is polypyrrole, and a sheathing base material 2 for sheathing the element 1 are provided. In this case, the material 2 has 0.2 or less of P/t, where P (unit, 10<-10>cm<3>.cm/cm<2>.sec.cmHg) is oxygen permeability at 105 deg.C of the base material and t (unit, cm) is average thickness from the surface of the sheath to the element 1. Thus, the permeability of the material and the thickness of the material are controlled to suppress influence of oxygen to the polypyrrole for forming at least part of the electrodes. Accordingly, excellent high frequency characteristic and high temperature durability are improved.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is applicable to a solid capacitor having polypyrrole as at least a part of the electrode, and is particularly applicable to a solid capacitor having a low oxygen permeability exterior, excellent high frequency characteristics, and high temperature resistance. Concerning solid capacitors with excellent durability.

〔overview〕

The present invention provides a solid capacitor in which a capacitor element in which at least a portion of electrodes sandwiching a dielectric material is made of polypyrrole is packaged with an exterior base material, and the exterior base material is
The oxygen permeability at °C is P (unit, 10-”cm3・cm/
cm2・sec-cmllg), and the average thickness is t (
The high temperature durability is improved by having a characteristic that P/t (unit: cm) is 1.2 or less.

[Conventional technology]

Conventionally, solid capacitors use oxide films of film-forming metals such as tantalum and aluminum as dielectrics, and use manganese dioxide and 7.7.8.8-tetracyanoquinodimethane (TCN) as dielectrics.
Q) Capacitors that use complex salts as part of the electrode have been developed, but those that use manganese dioxide as part of the electrode have a low electrical conductivity, so the ESR (equal series resistance) of the capacitor is large. , the high frequency characteristics are insufficient, and T
Electrodes in which CNQ complex salt is part of the electrode have drawbacks such as being unusable because they melt at high temperatures. Therefore, for the purpose of improving these, it has been proposed to use a conductive polymer such as polypyrrole as a part of the electrode (for example, Japanese Patent Laid-Open No. 60-37114).

[Problem to be solved by the invention]

However, the above-mentioned solid capacitor that uses polypyrrole as part of its electrodes has the problem that when kept in air at a temperature of 100°C or higher, the ESR gradually increases over time and the high frequency characteristics deteriorate accordingly. there were.

The purpose of the present invention is to solve the above-mentioned problems by:
It is an object of the present invention to provide a solid capacitor that has excellent high-temperature durability and does not have an increased ESR even when kept in air at a temperature of 00° C. or higher.

[Means for Solving the Problems] The present inventors have conducted various studies in order to solve the above problems. As a result, it was discovered that a capacitor equipped with a specific exterior has excellent high frequency characteristics and excellent high temperature durability, leading to the present invention.

That is, the present invention provides a solid capacitor comprising a capacitor element in which at least a portion of electrodes sandwiching a dielectric material is made of polypyrrole, and an exterior base material that exteriorizes this capacitor element, wherein the exterior base material is 105℃
The oxygen permeability at
/ cm' ・sec-cmHg), and the average thickness from the exterior surface to the capacitor element is t (unit,
cm), P/t is 1.2 or less.

FIG. 1 is a schematic cross-sectional view showing the structure of an example of a solid capacitor of the present invention. The capacitor element 1 includes a capacitor element 1 in which at least a portion of electrodes sandwiching a dielectric material is made of polypyrrole, an exterior base material 2, and leads 3 and 4.

In the present invention, a dielectric is an electrically insulating material,
For example, tantalum, aluminum, niobium, titanium, zirconium, magnesium, zinc, bismuth, silicon,
and oxides of film-forming metals such as hafnium, polymer compounds such as polystyrene terephthalate, polyethylene and polycarbonate, ceramics such as barium titanate, strontium titanate and magnesium titanate, glass and mica.

In the present invention, polypyrrole is a polymer having repeating units of pyrrole or pyrrole derivatives, and contains an electron-withdrawing compound as a dopant.
Xl0-'S/cm or more.

In the present invention, the capacitor element 1 in which at least a part of the electrodes sandwiching a dielectric material is made of polypyrrole is one in which at least a part of the electrodes in contact with or close to the dielectric material is made of polypyrrole. There are some types in which the polypyrrole electrode is used as an electrode lead as is, one in which a conductive carbon layer is formed on the outer surface of the polypyrrole electrode, and one in which the lead is connected using silver paste, solder, etc.

The present inventors heated the capacitor element described above to various temperatures and examined changes in characteristics over time and changes in physical properties of the polypyrrole itself constituting the electrode. As a result, the electrical conductivity of polypyrrole gradually decreases when heated above 100°C, and the ESR of the capacitor element increases accordingly, resulting in a decrease in high frequency characteristics. With a concentration of 1 vol, %, it does not change for a long time at lower concentrations,
It was found that the concentration gradually decreases at higher concentrations.

Therefore, next, capacitor elements having polypyrrole as part of the electrode were packaged with exterior base materials having various oxygen permeability, and changes in ESR at 105° C. were measured. In this case, E
The change in SR depends on the oxygen permeability P at 105°C and the average thickness t of the exterior base material, and in particular, when the value obtained by dividing the oxygen permeability by the average film thickness, that is, P/t, is taken as a parameter. It was found that the ESR after a certain period of time is uniquely determined regardless of the type of exterior base material.

Hereinafter, a fixed capacitor equipped with a capacitor element according to the present invention will be explained according to the drawings. Figure 2 shows a capacitor element with a capacitance of 2 μF using an electrolytic oxidation film of tantalum fine powder sintered body as a dielectric and a polypyrrole containing dodecylbenzenesulfonic acid as a dopant as an anode, and various organic polymer compounds as an exterior base material. 100℃ at 105℃ in air.
This is the relationship between P/t and ESR at the resonant frequency after time heat treatment. As is clear from Figure 2, the P/
When t is small, ESR does not change for all exterior base materials, but when P/t exceeds a certain value, ESR changes depending on this.
R increases. This value has the unit of oxygen permeability P as 10-1
0-1 O.cm/cm.sup.2.sec-cInHg, and the average thickness t from the exterior surface to the capacitor element 1 is 1.2 when expressed in cm.

Therefore, the oxygen permeability of the exterior base material at 105°C is P (unit, IQ-10cm3・cm/cm2・sec -c
mHg), and the average thickness of the exterior base material from the exterior surface to the capacitor element l is t (cm), and the solid capacitor of the present invention is formed so that P/t is 1.2 or less: It has excellent high-temperature durability because there is no change in F and SR due to heating.

In the present invention, oxygen permeability is measured by conventional gas permeability measurement methods such as pressure method and isobaric oxygen electrode method.

Furthermore, as mentioned above, since the solid capacitor of the present invention is characterized in that it is formed so that P/t is 1.2 or less, the exterior base material is an epoxy resin used for the exterior of ordinary capacitors. , silicone resins, general-purpose polymers such as polyethylene terephthalate, polystyrene, and polyvinylidene chloride, organic polymer compounds with excellent heat resistance such as engineering plastics such as polyphenylene sulfide, polyether ether ketone, and glass and mica. Inorganic polymer compounds, metals, etc. can be used alone or in combination, and the average thickness of the exterior base material may be controlled according to the oxygen permeability of each so as to satisfy the above conditions. Among the above, it is preferable to use organic polymer compounds from the viewpoint of moldability and the like.

[Effect]

According to the present invention, the oxygen permeability of the exterior base material and the average thickness of the exterior base material are controlled to suppress the influence of oxygen on the polypyrrole that constitutes at least a portion of the electrode, so the solid capacitor has excellent high frequency characteristics. Moreover, it is possible to provide a solid capacitor with excellent high-temperature durability.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited only to these Examples.

Example 1 Disc-shaped fine tantalum powder sintered pellets (porosity 50%) with a diameter of 5 mm and a thickness of 0.8 mm were dissolved in a nitric acid aqueous solution at a temperature of 100%.
The pellets were anodized with V, washed and dried to obtain pellets whose fine powder surface was coated with a tantalum oxide dielectric. The capacitance of this pellet measured in a nitric acid aqueous solution was 2 μF. Next, the pellets were immersed in a 25 wt% dodecylberbenzenesulfonic acid-iron(I) salt-1,5 wt% pyrrole mixed methanol solution at -75°C, and then 25 wt% in air.
Pyrrole was polymerized at ℃ for 1 hour, and leads were drawn out from the surface using silver paste to obtain a solid capacitor element having polypyrrole as part of the electrode. The ESR of this capacitor element at I MHz was 90 mΩ.

The capacitor element described above was repeatedly immersed in polyvinylidene chloride emulsion, dried and aged to an average thickness of 1
Capacitors packaged with polyvinylidene chloride of 1.5 mm, 1.5 mm and 2 mm were obtained. When the oxygen permeability of polyvinylidene chloride, which is the exterior base material, at 105°C was measured using a pressure method, it was 0.11 Xl0-”cm3 °cm/c.
m"-5ec-cmt (g. And,
P/t was 1.10.0.73 and 0.55, respectively.

The obtained solid capacitor was heat-treated in air at 105° C. for 100 hours, and the ESR at I MHz was measured.

The results are summarized in Table 1, and the ESR of all samples was at the same level as before heat treatment. It was a solid capacitor with excellent high-temperature durability.

Comparative Example 1 Using the capacitor element of Example 1, it was repeatedly dipped in the polyvinylidene chloride emulsion of Example 1 and dried H-aged to obtain a polyurethane material with an average thickness of 0.4 mm and 0.6 [1 m and Q, 3 mm. A capacitor coated with vinylidene chloride was obtained. The P/t of each of these exterior base materials is 2.7
5.1.83 and 1.38.

In the same manner as in Example 1, the obtained solid capacitor was heat treated and the ESR at I MHz was measured. The results are shown in Table 1 together with Example 1, and the ESR of all the samples increased compared to before the heat treatment, indicating that the solid capacitors had poor high-temperature durability.

(Hereinafter, the margins of this page) Table 1 Example 2 The capacitor element of Example 1 was manufactured using an epoxy resin with an imidazole compound as a hardening agent, with an average thickness of 2.5 mm.
, 4 mm and 6 mm to obtain capacitors. When the oxygen permeability of the epoxy resin used as the exterior base material at 105°C was measured using a pressure method, it was found to be 0.21X10
-10cm36 cm/ Cm2・sec -cml
(g, and P/t were 0.84, 0.53 and 0.35, respectively.

The obtained solid capacitor was heated at 105°C in air for 100°C.
The sample was heat-treated for a period of time, and the ESR at I Ml (z) was measured.

The results are summarized in Table 2, and the ESR of all the samples was at the same level as before the heat treatment, indicating that the solid capacitors had excellent high-temperature durability.

Comparative Example 2 Using the capacitor element of Example 1, using epoxy resin in the same manner as Example 2, the average thickness was 0.8 +++ m, 1 f.
A capacitor was obtained which was packaged so that the diameter of the capacitor was 1.5 mm. The P/t of these exterior base materials is 2 and 63.2, respectively.
．． 10 and 1.40.

As in Example 1, the obtained solid capacitor was heat treated and the ESR at 1 MHz was measured. The results are shown in Table 2 together with Example 2, and the ESR of all the samples increased compared to before the heat treatment, indicating that the solid capacitors had poor high-temperature durability.

(Hereinafter, the margin of this page) Table 2 Example 3 The capacitor element of Example 1 was manufactured using a silicone resin obtained from a chlorosilane derivative, with an average thickness of 12 mm,
Transfer molding was performed to obtain a capacitor with a width of 18 mm and 25 mm. When the oxygen permeability of the silicone resin that is the exterior base material at 105°C was measured using a pressure method, it was 1.23
/cm' sec -cmHg, and P/t were 1.03, 0.68 and 0.49, respectively.

The obtained solid capacitor was heated at 105°C in air for 100°C.
The sample was heated for a period of time and the ESR at I MHz was measured.

The results are summarized in Table 3, and the ESR of the samples were all at the same level as before the heat treatment, indicating that the solid capacitors had excellent high-temperature durability.

Comparative Example 3 Using the capacitor element of Example 1 and using silicone resin in the same manner as Example 3, the average thickness was 4f[ll1115
A capacitor which was packaged so as to have mm and gm+n was obtained. The P/t of these exterior base materials is 3.08.2, respectively.
．． 05 and 1.54.

In the same manner as in Example 1, the obtained solid capacitor was heat treated and the ESR at I MHz was measured. The results are shown in Table 3 together with Example 3, and the ESR of all the samples increased compared to before the heat treatment, indicating that the solid capacitors had poor high-temperature durability.

<The following is the margin of this page> Table 3 Example 4 Instead of the tankle pellets of Example 1, a film with a thickness of 50 μm, 11 sides, and 12 times the surface area by etching was used.
An aluminum oxide dielectric layer and a conductive polypyrrole layer were formed using a cm square aluminum foil in the same manner as in Example 1, and leads were drawn out from the surface using silver paste to form a part of the electrode using the polypyrrole. A solid capacitor element was obtained. I MH of this capacitor element
The ESR at z was 40 mΩ.

The above capacitor element was packaged with the epoxy resin of Example 2 so that the average thicknesses were 2 mm, 3n+m, and 5 mm to obtain capacitors.

The obtained solid capacitor was heated at 105°C in air for 100°C.
The sample was heat-treated for a period of time, and the ESR at I MHz was measured. The results are summarized in Table 4, and the ESR of all the samples was at the same level as before the heat treatment, indicating that the solid capacitors had excellent high-temperature durability.

Comparative Example 4 Using the capacitor element of Example 4, epoxy resin was used in the same manner as in Example 2, and the average thickness was 0.5 mm, 1 mm.
A capacitor was obtained which was packaged so as to have a thickness of 1.5 mm.

In the same manner as in Example 1, the obtained solid capacitor was heat treated and the ESR at I MHz was measured. The results are shown in Table 4 together with Example 4, and the ESR of all the samples increased compared to before the heat treatment, indicating that the solid capacitors had poor high-temperature durability.

(Hereinafter, the margin of this page) Table 4 [Effects of the Invention] As explained above, according to the present invention, an electrode made of polypyrrole at least in part has low ESR, excellent high-frequency characteristics, and excellent high-temperature durability. Solid capacitors can be provided, and the effect is great.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of an example of a solid capacitor of the present invention. FIG. 2 is a characteristic diagram showing the relationship between the ESR of the capacitor and the P/t of the exterior base material. ■... Capacitor element, 2... Exterior base material, 3.4.
...Lead.

Claims (2)

[Claims] 1. A solid capacitor comprising a capacitor element in which at least a portion of the electrodes sandwiching a dielectric material is made of polypyrrole, and an exterior base material that exteriorizes this capacitor element, wherein the exterior base material Transmittance is P (unit, 10^-1^0cm^3 cm/cm^
2・sec・cmHg), and the average thickness from the exterior surface to the capacitor element is t (unit, cm),
A fixed capacitor characterized in that P/t is 1.2 or less. 2. The solid capacitor according to claim 1, wherein the exterior base material is an organic polymer compound.