JPS62179709A - Thin film dielectric material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the structure of a film capacitor, and aims to make the film capacitor smaller and lighter, and to improve its performance.

(Prior art) (Problem to be solved by the invention) Due to the trend toward smaller and lighter equipment, the increased density of electronic circuits due to the adoption of highly integrated circuits, and the spread of automatic insertion, electronic components have become smaller. The demand for this is becoming increasingly strong. In it.

Similarly, various attempts have been made to develop film capacitors to make them smaller. What is the capacitance of a capacitor?

It is proportional to the permittivity of the dielectric and the electrode area, and inversely proportional to the thickness.

Therefore, when trying to downsize conventional film capacitors, by increasing the dielectric constant of the film used as a dielectric material or reducing its thickness,
It is required to increase the capacitance per unit electrode area.

Generally, a polymer film made of polyethylene terephthalate polypropylene, polystyrene, polycarbonate, or the like is used as a dielectric material for a film capacitor. The thickness of these polymer films is 4-6
μm is normal, but in recent years due to market demand, 2 to 3 μm
Films of polyethylene terephthalate with a thickness of However, when producing films with a thickness of 2 to 3 μm on an industrial scale, many technical problems arise due to the thinness of the films.

For example, in order to prevent wrinkles and produce films with high thickness accuracy at a high yield, sophisticated control is required for the purification of raw polymers, melt molding, heating stretching, and the atmosphere of the production line building and its dustproofing. becomes. Therefore, it is extremely difficult to mass-produce thin films at low cost.

Industrially, it is considered that the maximum thickness of the film is about 2 μm.

As a means of reducing the size and weight of film capacitors, Japanese Patent Application Laid-Open No. 127828/1983 discloses that vapor-deposited metal electrodes are formed on both sides of a heat-resistant plastic film, leaving different ends, and heat-cured metal electrodes are formed on one side. A chip-shaped film capacitor has been proposed in which a thermoplastic resin layer is formed on the other side, and a heat-resistant thermoplastic resin layer is formed on the other side, and these minimum structural units are laminated. The dielectric layer of this film capacitor is composed of a heat-resistant plastic film, a thermosetting resin layer, and a heat-resistant thermoplastic resin layer, and these two are connected in parallel on the circuit, which makes them different from conventional film capacitors. By comparison, the capacitance has increased several times.

However, since the newly added dielectric layer is made of an organic resin layer, a large dielectric constant cannot be expected, and this is insufficient to meet the demand for smaller and lighter film capacitors.

Furthermore, a thin film dielectric material has been proposed in which A/ is deposited as a lower electrode on a glass substrate, a thin film dielectric layer is deposited thereon, and /l is deposited on top of that as an upper electrode. However, in the case of this thin film dielectric material, the film thickness of the thin film dielectric is 0.3 to 1.0 μm, so electrical weak points such as pinholes and mesh cracks are likely to occur, and the electrical insulation resistance is low. It had the disadvantage of being small.

In addition, since the upper electrode is a vapor-deposited aluminum film with a thickness of approximately 0.05 μm, in the event of a local dielectric breakdown, the upper electrode will instantly scatter only at the periphery, creating a self-healing effect that maintains its function as a capacitor. By using this effect, it is possible to improve to some extent the poor insulation resistance of the thin film dielectric in the initial stage. On the other hand, in terms of actual capacitor performance, they have the drawbacks of large DC leakage current and large dielectric loss when voltage is applied.

(Means for solving the problem) The present inventors have solved the above m)! As a result of intensive research to eliminate the drawbacks of 1m electric material, we have found that by providing an organic polymer thin film layer on the metallized film layer as the lower electrode, the electrical insulation resistance and electrical dielectric strength were greatly improved. This led to the discovery that the yield rate was improved and the present invention was achieved.

The present invention will be specifically explained below with reference to FIG.

That is, the present invention uses an organic polymer film as a support substrate (
1), and on at least one side thereof, a conductive metal layer (2) as a lower electrode, an organic polymer thin film layer (3), a thin film dielectric layer (4), and a conductive metal layer ( This is a WIB dielectric material for capacitors made by sequentially laminating 5).

The thin film dielectric layer is made of zinc sulfide, lead oxide, silicon oxide, etc., and its film thickness is in the range of 0.3 to 1.0 μm. Formation methods include coating method, coating method, and vapor phase growth method. etc. However, if the film thickness is 0.3 μm or less, sufficient electrical insulation resistance cannot be obtained, and if the film thickness is 1.0 μm or more, the film itself will crack, resulting in a decrease in the yield rate. Sputtering method is a vapor phase growth method.

Examples include ion blating method, vacuum evaporation method, and CVD method.

The organic polymer thin film layer has a dielectric loss tangent of 1 when measured at IKHz.
% and the film Ito, t is in the range of 0.7 μm, thermoplastic resins, thermosetting resins, and mixtures of both. However, if the film thickness is 0.1 μm or less, sufficient electrical insulation resistance cannot be obtained, and if the film thickness is 0.7 μm or more, a large capacitance per cross-sectional area cannot be obtained, which is not practical.

For example, thermoplastic resins include polystyrene, polyethylene, polyamide, polyester, etc., and thermosetting resins include urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester, alkyd resin, urethane resin, etc. can give. The organic polymer thin film is formed by a barcode method, a printing method, or the like, or a vapor phase growth method using a vacuum device.

By forming this organic polymer thin film layer on the metallized film layer as the lower electrode, the adhesion strength between the thin film dielectric layer and the lower electrode is greatly increased, and the yield rate is improved. Electrical insulation resistance has been greatly improved. If a thin film dielectric layer is formed directly on the metallized film serving as the lower electrode, a strong adhesive layer cannot be obtained, and peeling from the lower electrode occurs due to the influence of moisture. Furthermore, when the thin film dielectric layer itself is formed using low-temperature plasma, cracks may occur in three parts due to physical and chemical distortion of the thin film dielectric. However, by forming an organic polymer thin film layer between the metallized film layer serving as the lower electrode and the thin film dielectric layer, it has become possible to increase the adhesive force between the two at once. Furthermore, since the organic polymer thin film layer plays the role of a kind of shock absorption layer, it has become possible to suppress the occurrence of cracks in the thin film dielectric layer. It also acts as an insulating layer to reinforce electrical weak points in the thin film dielectric layer, increasing electrical insulation resistance, electrical dielectric strength, and yield rate. Therefore, it is clear that the thin film dielectric material obtained according to the present invention has a capacitance several times that of a conventional film capacitor, and enables miniaturization of metallized film capacitors.

(Example) The present invention will be specifically described below with reference to FIG. 1 by showing an example.

Examples 1 to 7 A polyester film with a film thickness of 12 μm was used as the support substrate (1), and after performing ultrasonic cleaning in acetone, it was subjected to bombardment treatment (flow rate ratio iAr:Ot
=10:3. The degree of vacuum was 4XLO-2 Torr). For the lower electrode (2), Aj2 was vacuum deposited on a polyester film substrate. In order to form an organic polymer thin film layer thereon, phenoxy resin (PK HH, Union Carbide) [Example 1], polyester (Vylon 200. Toyobo) [Example 2], polycarbonate (32000F.

Mitsubishi Gas Chemical) [Example 3], polymethyl methacrylate (reagent grade, Method Pharmaceutical) [Example 4], polystyrene (GP-1, electrochemical) [Example 5], polyurethane resin (Crispon NT-150, Dainippon Ink & Chemicals) [Example 6].

Polyarylate (U-polymer, Unitika) [Example 7
] diluted to 10% (wt%).

Using the barcode method, a 0.3 μm organic polymer thin film layer (
3) was formed.

Next, on this organic polymer thin film layer, a zinc sulfide thin film dielectric layer (4) was formed by RF ion blasting using a mask to form non-evaporated portions. That is, argon is introduced into the Pelger and the degree of vacuum is 7X.
Maintained at 10-' Torr, voltage 2 MV, frequency 13
．． While applying a 56 MHz (7) high frequency electric field, the zinc sulfide evaporation base material was heated and evaporated with an electron gun, and 0.
A thickness of 5 μm was formed. However, the purity of the evaporated base material is 99.99.
% fine powder is press molded.

The material that had been vacuum sintered at 800° C. for 6 hours was used.

Further, a mask was applied to form a non-evaporated portion on the thin film dielectric layer, and AR was vacuum-deposited as an upper electrode (5).

The capacitance (IKI (measured at z), electrical insulation resistance (measured at 30 mm), and yield rate of the obtained thin film capacitor were measured. The results are shown in Table 1. However.

As Comparative Example 1, the dielectric layer was made of zinc sulfide alone.As Comparative Example 2, the dielectric layer was made of polyester resin alone. The yield rate is expressed as a percentage of 100 samples whose electrical insulation resistance is 5×10′Ω or more.

As is clear from Table 1, by forming the organic polymer thin film layer, it became possible to increase the electrical vIA edge resistance by more than an order of magnitude and to significantly increase the yield rate.

Table 1 Examples 8 to 14 Using the same resin as Examples 1 to 7, an organic polymer thin film layer (
3) was formed, and a lead oxide thin film dielectric layer (4) was formed on this organic polymer thin film layer. however.

The evaporation base material used was one obtained by press-molding fine powder with a purity of 99.99% and performing vacuum sintering for 6 hours. The formation method is the same as in Examples 1-7. However, as Comparative Example 3, the dielectric layer is made of lead oxide alone, and as Comparative Example 4, the dielectric layer is made of polyester resin alone.

As is clear from Table 2, by forming the organic polymer thin film layer, it was possible to increase the electrical insulation resistance by more than two orders of magnitude and to greatly increase the yield rate.

Examples 15-21 Using the same resin as in Examples 1-7, an organic polymer thin film layer (
3) was formed, and a silicon oxide thin film dielectric layer (4) was formed thereon. However, the evaporation base material used was one obtained by press-molding fine powder with a purity of 99.99% and performing vacuum sintering at 800'C for 6 hours. What is the formation method?

This is the same as Examples 1 to 7. However, as Comparative Example 5,
A case in which the dielectric layer was made of only silicon oxide, and a case in which the dielectric layer was made of only polyester resin as Comparative Example 6 were also added.

As is clear from Table 3, by forming the organic polymer thin film layer, it was possible to increase the electrical insulation resistance by more than two orders of magnitude and to greatly increase the yield rate.

(Effect of the invention) According to the present invention, the following effects can be obtained.

(11) Compared to conventional metallized film capacitors, the size can be significantly reduced.

(2) Compared to conventional thin film capacitors, it is possible to manufacture capacitors with high electrical insulation resistance and small dielectric loss tangent.

By forming a thin organic polymer film layer, we can make physically unstable thin film dielectrics stable.

The dielectric loss tangent was reduced and the electrical insulation resistance 1 yield rate was improved. The thin film dielectric material produced according to the present invention is a completely new and excellent thin film dielectric for capacitors, with almost no changes in handling during the manufacturing process compared to metallized films, which are dielectric materials for conventional film capacitors. Body materials can be provided.

[Brief explanation of drawings]

FIG. 1 schematically shows two thin film dielectric materials for capacitors according to the present invention. 1: Organic polymer film substrate 2: Lower electrode 3: Organic polymer thin film layer 4: Thin film dielectric layer 5: Upper electrode

Claims (1)

[Claims] An organic polymer film is used as a support substrate, and a conductive metal layer as a lower electrode, an organic polymer thin film layer, a thin film dielectric layer, and a conductive metal layer as an upper electrode are sequentially laminated on at least one surface of the organic polymer film. Thin film dielectric material for capacitors.