JPS6031244Y2 - composite parts - Google Patents

Description

[Detailed description of the invention] This invention consists of a thick film varistor mainly composed of zinc oxide sintered powder and a thick film capacitor mainly composed of dielectric porcelain sintered powder on an electrically insulating substrate. It concerns a composite component that is laminated through electrodes and arranged in electrical parallel, and its purpose is to provide a composite component with varistor properties and large capacitance, and at the same time improve the reliability of this composite component. , especially in improving moisture resistance.

Thick film varistors made of sintered zinc oxide powder and glass as a binder have been developed and put into practical use as minute, thick film parts.

In particular, they have been widely used in DC micromotors and connected to the micromotor's commutator to reduce electrical high-frequency noise.

However, increasing the precision of micromotor peripheral equipment,
Especially with the advancement of micro motors into audio equipment.

A problem with conventional thick film varistors has been that the noise level is insufficiently low.

This is because the capacitance of conventional thick film varistors is 150 to 300 pF (picofarad・10-1.2 F) at IMHz.
) was not sufficient to absorb high frequency noise such as in the SX band and FM band.

It has been found from various experiments that the capacitance required to absorb high frequency noise is greater than tooopF' at IMHz.

Therefore, abnormal high voltages such as spark voltage generated by DC micro motors are absorbed by thick film varistors, and high frequency noise is reduced to 100%.
A method has been proposed in which a thick film capacitor with a capacitance of 0 pF or more is used to absorb it.

The circuit diagram is shown in FIG. 1, where Zr is a thick film varistor and B is a thick film capacitor.

Its configuration is shown in FIG.

FIG. 2a is a sectional view, and FIG. 2a is a plan view.

In the figure, 1 is an electrically insulating substrate made of alumina, etc., on which silver paste is applied by screen printing.
Baking in air at 0°C formed the bottom electrode 2.

Zinc oxide sintered powder is placed on the lower electrode 2 at an angle of 80°~
A varistor paste prepared by kneading glass fudot as a binder which melts at 900°C with an organic binder was applied by screen printing, and baked at 900°C to form a thick film varistor 3.

Next, in parallel with the thick film varistor 3, a dielectric paste made by kneading dielectric porcelain sintered body powder mainly composed of barium titanate and glass as a binder with an organic binder is applied by screen printing. Baking at °C formed a thick film capacitor 4.

On top of that, apply silver paste by screen printing, 900
Baking at 0.degree. C. formed a section electrode 5.

The thus obtained composite component of a varistor and a capacitor was effective in absorbing electrical noise from a micromotor.

However, since this conventional composite component forms a thick film varistor and a thick film capacitor on the same surface, the area of the varistor part is smaller than in the case of only a thick film varistor, which causes some problems in terms of the varistor's performance limit. there were.

Due to these problems, thick film capacitors could not take up a sufficient area, and the yield rate for capacitances of 1000 pF or more was poor.

Furthermore, this conventional composite component had a problem in terms of reliability in terms of moisture resistance.

This is because the thick film capacitor part is extremely porous, and in conventional composite component configurations, the thick film capacitor part is exposed to the outside, and moisture and water can easily enter from there, causing insulation resistance due to long-term voltage application. This is because

Although increasing the amount of glass in the dielectric paste may be an easy way to improve the moisture resistance, this would greatly reduce the dielectric constant and make it impossible to obtain a capacitance of 1 ooopF' or more.

Therefore, the present invention has a structure in which a thick film varistor and a thick film capacitor are laminated so that the capacitance can be formed with sufficient margin without deteriorating the varistor characteristics in terms of electrical performance.

Additionally, in order to improve moisture resistance, the thick film capacitor section is not exposed and is completely sealed with the intermediate electrode and thick film varistor.

The thick film varistor has a glass content of 40% by weight relative to the zinc oxide sintered powder, and there is no problem with its moisture resistance.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 3a is a sectional view of the composite component of the present invention, and the same figure is a plan view.

In FIG. 3, 6 is an electrically insulating and heat-resistant substrate such as alumina, 7, 9 and 11 are electrodes, and 8 is a thick film capacitor, which is made of dielectric sintered ceramic powder and a small amount of glass.

10 is a thick film varistor made of sintered zinc oxide powder and glass.

The varistor paste used in this invention consists of zinc oxide sintered powder with an average particle size of 6 microns and zinc borosilicate glass (33-3i-Zn-Q glass) with an average particle size of 5 microns at a weight ratio of 60% each. %, 40% was weighed, an organic binder was added thereto, and the mixture was kneaded.

On the other hand, the dielectric paste was prepared by adding a small amount of glass to powder of a dielectric ceramic sintered body whose main component is barium titanate (BaTi03) having a high dielectric constant, and kneading the mixture with an organic binder.

In addition, as a commercially available product, DuPont's dielectric paste No.
, 5217, No.

I used something like 8289.

Their dielectric constants are 175 to 1200, respectively.

Two types of electrode materials were considered because the intermediate electrode 9 plays the role of a moisture-resistant cover for the thick film capacitor.

One was to create a silver paste by adding bismuth oxide to silver powder and kneading it with an organic binder.

When the weight ratio of bismuth oxide to silver powder was less than 2%, the adhesion of the silver electrode to the substrate 6 and the thick film capacitor deteriorated.

On the other hand, when it exceeds 30%, the diffusion of bismuth oxide into the thick film capacitor increases, reducing the capacitance.

Therefore, the optimum amount of bismuth oxide relative to silver powder is 2 to 3% by weight.

The other silver paste was prepared by adding bismuth borosilicate glass (13-3i-Bi-Q type) to silver powder and kneading it with an organic binder.

At this time, the optimum weight ratio of bismuth borosilicate glass to silver powder was 5 to 3% by weight for the same reason as in the case of bismuth oxide.

Next, a method for manufacturing the composite component of this example will be described.

First, the silver paste is applied onto the alumina substrate 6 by screen printing, and after drying, it is passed through a tunnel furnace where it is held at a maximum temperature of 900°C for a period of time, and baked in the air on the lower electrode 7.
was formed.

Next, a dielectric paste was applied by screen printing to a wider width than the lower electrode 7, and baked at 900° C. in the same tunnel furnace to form a thick film capacitor 8.

Next, as shown in the figure, a silver paste was applied by screen printing to a wider area than the thick film capacitor 8, and baked at 900° C. in the same tunnel furnace to form an intermediate electrode 9.

On top of that, varistor paste was applied by screen printing so as to be wider than the thick film capacitor 8 and to cover the parts of the thick film capacitor 8 that could not be covered by the intermediate electrode 9. Membrane varistor 10
was formed.

Finally, thick film varistor 10 is screen printed with silver paste.
The coating was applied so as to be narrower than the width of , and in contact with the lower electrode 7 , and baked at 900° C. in a tunnel furnace to form the upper electrode 11 .

The thus obtained composite component of a thick film varistor and a thick film capacitor has significantly improved varistor characteristics than the conventional example, especially the pulse withstand voltage of 200V compared to the conventional example's 150V, and the capacitance is also IMH2. The yield of 1ooopF' or more is 95%, which is significantly better than the conventional 60%.

The moisture resistance properties were also significantly improved compared to the conventional example, as shown in Figure 4.

In FIG. 4, A indicates the characteristics of this embodiment, and A indicates the characteristics of the conventional example.

The varistor voltage VAo (the voltage between the terminals when a current of 1 QmA is passed through this composite component) used in this test is 15 V, and the capacitance is about 1 ooopF'.

Apply DCOolW to this composite part and heat it at 60°C190
Tested in a humidity bath at ~95% RH.

The composite component of the present invention constructed as described above is stacked so that the thick film capacitor is located below the thick film varistor through the intermediate electrode, and the thick film capacitor is completely formed by the intermediate electrode and the thick film varistor. The structure is sealed and not exposed to the outside, which greatly improves moisture resistance.

This is because, as mentioned above, thick film capacitors are extremely porous, and when exposed to the outside, they are easily affected by the outside air, especially humidity. This has the advantage of improving humidity resistance.

In addition, since the present invention has a structure in which thick film capacitors and thick film varistors are laminated via intermediate electrodes, it can be easily obtained by printing and baking, and does not require a sintering process, and can be provided at low cost. It is.

Furthermore, the structure can be manufactured directly on a substrate such as alumina, which allows for great flexibility in design, and thick film capacitors and thick film varistors can be formed very thin, making it possible to make the entire structure compact. It has its advantages.

Furthermore, since the electrodes are easy to take out and can be created by printing or baking as described above, there is no need to use expensive materials such as platinum-palladium alloys with particularly high heat resistance for the electrodes.

Composite parts like this can be miniaturized and can be used in a wide variety of fields, including applications to micromotors in audio equipment and noise prevention for microcomputer-applied equipment in the future, and their industrial value is high. is extremely large.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing other circuits of this composite part, Figure 2 a
, b are a cross-sectional view and a plan view showing the configuration of a conventional composite part, Figures 3a and b are a cross-sectional view and a plan view showing the configuration of a composite part of the present invention, and Figure 4 is a cross-sectional view and a plan view showing the configuration of a composite part of the conventional example and the present invention. It is a figure which shows the result of the moisture resistance test of a composite part. 6...Electrical insulating substrate, 7...Curved lower electrode, 8
... Thick film capacitor, 9 ... Intermediate electrode, 1o ... Curved thick film varistor, 11 ... Upper electrode.

Claims (3)

[Scope of utility model registration request] (1) A thick film capacitor and a thick film varistor are stacked on an electrically insulating substrate so that the thick film capacitor is located below the thick film varistor via an intermediate electrode, and are electrically parallel to each other. A composite component characterized in that the thick film capacitor is completely sealed with the intermediate electrode and the thick film varistor so that it is not exposed to the outside. (2) The composite component according to claim 1, which is a registered utility model, using as an intermediate electrode a silver paste prepared by adding 2 to 3% bismuth oxide (B12O3) to silver powder and kneading it with an organic binder. (3) Utility model registration using a paste prepared by adding 5 to 30% by weight of bismuth borosilicate glass (B-3i-Bi-Q system) to silver powder and kneading it with an organic binder as an intermediate electrode as claimed in claim 1 Composite part day day 0