JPH118155A - Capacitor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize surface-mounting capacitor which is excellent in heat and inflammability resistance and very small in size and a manufacturing method thereof. SOLUTION: Laminates each composed of a metal electrode foil 10 and a dielectric layer 12 laminated on its one surface are laminated to form a capacitor element 18, and outer electrodes 20 are each provided to each edge face of the capacitor element 18 for the formation of a capacitor 22, wherein the dielectric layer is formed of inorganic material. The material solution of inorganic material is applied to coat the surface of the metal electrode foil 10 and burned, whereby the laminate composed of the metal electrode foil 10 and the dielectric layer 12 of organic material formed on the foil 10 is formed, then the laminates are laminated and subjected to heating and pressing into the capacitor element 18, and outer electrodes are each provided to each edge face of the capacitor element 18 for the formation of the capacitor 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mount capacitor and a method of manufacturing the same, and more particularly, to a small surface mount capacitor having excellent heat resistance and flame retardancy.

[0002]

2. Description of the Related Art In recent years, with the demand for miniaturization of electronic equipment,
The surface mounting technology of electronic components incorporated in this has spread,
As for capacitors, surface mount type capacitors are widely used.

FIG. 7 shows an example of such a surface mount capacitor. The capacitor 50 includes a metal electrode foil 52 such as an aluminum foil, and a film-like dielectric layer 54 made of polypropylene, polyethylene terephthalate, polyphenylene sulfide, or the like, and a margin 56 along one side of the dielectric layer 54. A laminate formed by laminating so as to be formed, a plurality of laminates, or wound after lamination,
Thereafter, the capacitor element 58 is formed by applying heat and pressure, and an external electrode (metallicone electrode) 60 is formed by spraying a metal material on both end surfaces of the capacitor element 58.

[0004] In the capacitor 50, each metal electrode foil
52 are disposed facing each other with a dielectric layer 54 therebetween,
A gap 62 is formed between one end 52a of each metal electrode foil 52 (the end of the dielectric layer 54 on the side in contact with the margin portion 56) and one of the left and right external electrodes 60. The other ends 52b of the metal electrode foils 52 are alternately connected to the left and right external electrodes 60, respectively.

[0005]

By the way, in the case of a surface mount type electronic component, the solder heat resistance is required to be 260 ° C./5 seconds due to the temperature conditions at the time of attaching a flow solder or a reflow solder. However, the heat-resistant temperature of the dielectric layer 54 used in the conventional capacitor 50 is about 85 ° C. for polypropylene and about 125 ° C. for polyethylene terephthalate.
℃, polyphenylene sulfide is as low as about 170 ℃, soldering under normal temperature conditions (260 ℃)
The high temperature causes the dielectric layer 54 to be thermally deformed, which adversely affects various characteristics of the capacitor such as a change in capacitance and a decrease in dielectric strength. For this reason, the conventional capacitor 50 cannot perform soldering work simultaneously with other electronic components,
Soldering work has been performed by lowering the temperature conditions during flow soldering and reflow soldering than other electronic components. As described above, the conventional capacitor 50 cannot perform the soldering operation simultaneously with other electronic components under the normal temperature condition, and the working efficiency is low, so that the use range thereof is limited. still,
If low-melting solder is used, both the capacitor 50 and other electronic components can be soldered at the same time.However, if low-melting solder is used, the normal temperature of flow soldering or reflow soldering is used. As compared with the case where soldering is performed under the condition (260 ° C.), the flow of solder and the solder bonding property are deteriorated, and as a result, the defect that the quality of soldering is deteriorated occurs.

The gap 62 formed between one end 52a of each metal electrode foil 52 and the external electrode 60 should originally have a sufficient width corresponding to the margin 56. However, actually, when the external electrode 60 is formed, the molten metallikon penetrates into the space 62, and as a result, the width thereof is considerably narrowed. In addition, the surface of the invading metallikon has an uneven shape and a sharp portion is generated, and the electric field is concentrated there, and a relatively low voltage is applied between the external electrode 60 and one end 52a of the metal electrode foil. Corona discharge is repeatedly generated. The metal electrode foil 52 is heated by the heat energy due to the creeping corona discharge, and the dielectric layer 54 is thermally degraded to cause dielectric breakdown. The abnormal temperature rise accompanying the dielectric breakdown eventually causes the capacitor element 58 to ignite. And there was a risk of fire. Further, since the surface mounting capacitor 50 is used in a state of being densely mounted on a circuit board together with other electronic components, when the other electronic components ignite, the combustion temperature of the dielectric layer 54 is externally increased. There was also a danger of ignition and fire due to heating at abnormally high temperatures exceeding

Further, as described above, the conventional dielectric layer 54
Since it was made of an organic material having a relatively low dielectric constant, such as polypropylene, polyethylene terephthalate, and polyphenylene sulfide, there was a limit in reducing the size of the capacitor.

The present invention has been devised to solve the above-mentioned problems of the conventional example, and has heat resistance enough to withstand normal temperature conditions with flow soldering and reflow soldering, and The present invention relates to a flame-retardant capacitor having no danger of igniting a capacitor element due to creeping corona discharge generated between an external electrode and an end of a metal electrode foil or abnormal high-temperature heating from the outside, and a method of manufacturing the same. For the purpose of realization. Another object of the present invention is to realize a very small surface mount capacitor and a method of manufacturing the same by forming the dielectric layer from a material having a large dielectric constant.

[0009]

In order to achieve the above object, a capacitor according to the present invention comprises a plurality of laminates formed by laminating a dielectric layer on one surface of a metal electrode foil, Alternatively, in a capacitor in which external electrodes are formed by spraying an electrode material on both end surfaces of the capacitor element while laminating and winding the capacitor element, the dielectric layer is made of an inorganic material.

Further, in the method for manufacturing a capacitor according to the present invention, a raw material solution of an inorganic material is applied to one surface of a metal electrode foil and then baked, whereby the inorganic material is coated on one surface of the metal electrode foil. Forming a laminated body in which the formed dielectric layers are laminated, laminating a plurality of the laminated bodies, or winding after laminating, performing a heating and pressing treatment to form a capacitor element, and further, An external electrode is formed by spraying an electrode material on both end surfaces of the capacitor element.

[0011] As the inorganic material, lead zirconate titanate or barium titanate is applicable.

Thus, in the capacitor of the present invention,
Since the dielectric layer is made of an inorganic material such as lead zirconate titanate or barium titanate, the dielectric layer can be formed even if soldering is performed under normal temperature conditions (260 ° C.) with flow soldering or reflow soldering. Is not thermally deformed, and does not cause deterioration in the characteristics of the capacitor such as a change in capacitance and a decrease in dielectric strength. In addition, even if a creeping corona discharge is generated between the external electrode and the end of the metal electrode foil, the dielectric layer is made of an inorganic material, so that it does not burn and prevents the capacitor element from firing. Is done. further,
Since the dielectric constant of an inorganic material is several tens to hundreds of times higher than that of an organic material, a capacitor having a dielectric layer made of an inorganic material is smaller than a capacitor having a dielectric layer made of an organic material. However, since a capacitor having the same capacitance as that when the dielectric layer is made of an organic material can be realized, the size of the capacitor can be reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A capacitor according to the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 10 denotes a metal electrode foil made of aluminum or the like.
A thin-film dielectric layer 1 made of an inorganic material, lead zirconate titanate [Pb (Zr, Ti) O ₃ ]
2 are laminated to form a laminate 14. One end 12a of the dielectric layer is laminated so as to slightly protrude from one end 10a of the metal electrode foil.
A margin portion 16 is formed along one side. An example of a method for forming the above-described laminate 14 will be described. First, a sol-gel raw material solution of lead zirconate titanate, for example, lead acetate,
A lead compound such as lead nitrate, a zirconium nitrate, a zirconium compound such as zirconium isopropoxide, and a sol-gel raw material solution prepared by diluting a titanium raw material such as titanium alkoxide with acetic acid and alcohol, the metal electrode foil 10 After being applied or sprayed on one surface and applied, 100 to 30
Dry at a temperature of 0 ° C. to a dry gel state. further,
After pre-baking at a temperature of about 450 ° C., main firing is performed in a high-temperature oxygen atmosphere of 600 to 700 ° C. to obtain a metal electrode foil.
On one surface of 10, a thin dielectric layer 12 made of lead zirconate titanate is formed. Then, by irradiating a laser to remove a part of the metal electrode foil 10 in order to secure the margin portion 16, the laminate 14 shown in FIG. 1 can be formed.

Next, as shown in FIG.
14 are alternately stacked such that the margin portions 16 are arranged on opposite sides. After laminating a desired number of laminates 14, the capacitor element 18 is formed by applying pressure and heat treatment and molding. Further, as shown in FIGS. 3 and 4,
The capacitor 22 according to the present invention is formed by forming metal electrodes such as metal copper or solder on both end surfaces of the capacitor element 18 to spray metallicon to form the external electrodes 20. Thus, as shown in FIG.
Are arranged to face each other with the dielectric layer 12 interposed therebetween, and the other ends 10b of the metal electrode foils 10 are alternately connected to the left and right external electrodes 20, respectively. Also,
One end 10a of the metal electrode foil 10 in contact with the margin,
A gap 24 is formed between the external electrode 20 and either of the left and right electrodes.

In the capacitor 22 of the present invention having the above-described structure, the dielectric layer 12 is made of lead zirconate titanate formed by firing at a high temperature of 600 to 700 ° C., so that it has excellent heat resistance. Even if soldering is performed under normal temperature conditions (260 ° C.) with flow soldering or reflow soldering,
Since the dielectric layer 12 is not thermally deformed, the deterioration of the characteristics of the capacitor 22 such as the fluctuation of the capacitance and the decrease of the dielectric strength does not occur.

Also, one end 10a of the metal electrode foil 10
The gap 24 formed between the external electrode 20 and the external electrode 20 should have a sufficient width corresponding to the margin portion 16,
In forming the external electrode 20, as a result of the molten metallikon penetrating into the space 24, the width thereof is considerably narrowed, and furthermore, the surface of the metallikon penetrated has an uneven shape,
Since a sharp portion is generated, the electric field is concentrated there, and a creeping corona discharge is repeatedly generated between the external electrode 20 and one end 10a of the metal electrode foil 10 at a relatively low voltage.
However, in the capacitor 22 of the present invention, the dielectric layer 12
Is made of an inorganic material, so that a creeping corona discharge is repeatedly generated between the external electrode 20 and one end 10a of the metal electrode foil 10, or even if the external electrode 20 is heated at an abnormally high temperature, The dielectric layer 12 made of the material does not burn, so that ignition of the capacitor element 18 can be prevented.

Further, the capacitor 22 of the present invention is made of an inorganic material having a dielectric constant several tens to several hundreds times higher than that of an organic material.
Because of the configuration of the capacitor 12, even if the capacitor is smaller than the capacitor in which the dielectric layer 12 is made of an organic material, the capacitor 22 having the same capacitance as when the dielectric layer 12 is made of an organic material is used. Since this can be realized, the size of the capacitor 22 can be reduced.

FIGS. 5 and 6 show a capacitor 22 according to another embodiment of the present invention. This capacitor
22, the dielectric layer 12 is laminated on one surface of the metal electrode foil 10 such that one end 12a of the dielectric layer 12 covers the end surface of the one end 10a of the metal electrode foil 10. This is different from the capacitor 22 shown in FIGS. 1 to 4 in that the stacked body 14 is formed by the above-described process, and the margin portion 16 does not exist. The laminate 14 is prepared by coating a sol-gel raw material solution of lead zirconate titanate on one surface and one end of the metal electrode foil 10.
After coating or spraying on the end face of 10a and applying it,
After drying at a temperature of 300 ° C. to form a dried gel state, and further calcining at a temperature of about 450 ° C.,
It can be formed by sintering in a high-temperature oxygen atmosphere at a temperature of ° C.

The plurality of laminates 14 configured as described above are
One end 10a of the metal electrode foil 10 covered with the dielectric layer 12
Are alternately stacked such that they are arranged on the opposite sides. After laminating a desired number of the laminates 14, a capacitor element 18 is formed by applying pressure and heat treatment to form a capacitor element 18, and a metal material is sprayed on both end surfaces of the capacitor element 18 with a metal material such as copper or solder. 6 to form the external electrode 20, the capacitor 22 shown in FIG. 6 is formed. Thus, as shown in FIG.
Are arranged to face each other with the dielectric layer 12 interposed therebetween, and the other ends 10b of the metal electrode foils 10 are alternately connected to the left and right external electrodes 20, respectively. Also,
In this capacitor 22, the end face of one end 10a of the metal electrode foil 10 is covered with the dielectric layer 12, and the margin portion 16 does not exist on the surface of the multilayer body 14. The metal material does not enter the margin, and one end 10a of the metal electrode foil 10 and the external electrode 20 are connected to the end 10a.
Is completely insulated by the dielectric layer 12 covering the end face of the substrate.

In this capacitor 22, there is no margin 16 between one end 10 a of the metal electrode foil 10 and the external electrode 20. Since the outer electrode 10a and the outer electrode 20 are completely insulated by the dielectric layer 12 covering the end 10b, the molten metal material enters the margin 16 when the outer electrode 20 is formed, and the dielectric strength decreases. Or a creeping corona discharge is not generated between the external electrode 20 and the one end 10a of the metal electrode foil 10, and it is possible to prevent ignition of the capacitor element 18 and deterioration of characteristics of the capacitor 22. It is.

In the above description, the case where lead zirconate titanate is used as the inorganic material constituting the dielectric layer 12 has been described. However, the present invention is not limited to this. For example, barium titanate (BaTiO ₃ ) may be used. May be used.

The capacitor 22 is provided with a metal electrode foil 10
On the surface of, a multilayer capacitor formed by laminating a plurality of laminates 14 formed by laminating the dielectric layers 10 has been described, but the present invention is not limited to this, and is wound after lamination. The present invention is also applicable to a laminated / wound type capacitor that undergoes a process.

[0023]

In the capacitor according to the present invention, since the dielectric layer is made of an inorganic material, it can be soldered under normal temperature conditions (260 ° C.) with flow soldering or reflow soldering. In addition, it is possible to prevent deterioration of the characteristics of the capacitor such as a change in the capacitance and a decrease in the dielectric strength without the dielectric layer being thermally deformed. Also, a creeping corona discharge is generated between the external electrode and the end of the metal electrode foil,
Alternatively, even when heated at an abnormally high temperature from the outside, the dielectric layer is made of an inorganic material, so that the capacitor element does not burn and ignition of the capacitor element can be prevented. Furthermore, since the dielectric layer is composed of an inorganic material whose dielectric constant is several tens to several hundreds times larger than that of an organic material, even if the capacitor is smaller in size than a capacitor in which the dielectric layer is composed of an organic material, the dielectric layer is formed of Since it is possible to realize a capacitor having the same capacitance as the case where the capacitor is made of an organic material, the size of the capacitor can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a laminate according to the present invention.

FIG. 2 is an explanatory view showing a capacitor element according to the present invention.

FIG. 3 is a perspective view of a capacitor according to the present invention.

FIG. 4 is a partial sectional view of a capacitor according to the present invention.

FIG. 5 is a sectional view showing another laminated body according to the present invention.

FIG. 6 is a partial cross-sectional view showing another capacitor according to the present invention.

FIG. 7 is a partial sectional view of a conventional capacitor.

[Explanation of symbols]

 10 Metal electrode foil 12 Dielectric layer 14 Laminate 16 Margin 18 Capacitor element 20 External electrode 22 Capacitor 24 Void

Claims (4)

[Claims] 1. A capacitor element is formed by laminating or winding a plurality of laminates formed by laminating a dielectric layer on one surface of a metal electrode foil, and forming electrodes on both end faces of the capacitor element. A capacitor in which an external electrode is formed by spraying a material, wherein the dielectric layer is made of an inorganic material. 2. The method according to claim 1, wherein the inorganic material is lead zirconate titanate or barium titanate.
A capacitor according to claim 1. 3. A dielectric material layer made of an inorganic material is laminated on one surface of the metal electrode foil by applying a raw material solution of the inorganic material on one surface of the metal electrode foil and then firing the solution. After forming a laminate, laminating a plurality of the laminates, or winding after lamination, applying heat and pressure treatment to form a capacitor element, and further spraying electrode material on both end surfaces of the capacitor element A method for manufacturing a capacitor, comprising: forming an external electrode. 4. The method according to claim 3, wherein the inorganic material is lead zirconate titanate or barium titanate.
3. The method for manufacturing a capacitor according to claim 1.