JPS5937567B2 - Manufacturing method for thick film porcelain capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing thick film porcelain capacitors constituting thick film integrated circuits.

Conventional capacitors of this type consist of an Ag-containing glass frit on a ceramic substrate made of alumina, forsterite, etc.
A lower electrode is formed by printing and drying an electrode paste such as Pd, Au, Au-Pt, or Au-Pd, and then a porcelain paste made of barium titanate-based porcelain material is printed and dried as a dielectric on top of the lower electrode. After forming a dielectric layer and further printing and drying the electrode paste on it to form an upper electrode, it was fired at a temperature not exceeding 1050°C.

This firing temperature is significantly lower than the optimum firing temperature of 1300° C. to 1380° C. for barium titanate-based porcelain.

This is electrode paste crab 050 containing glass frit
This is because they cannot withstand temperatures above ℃.

Therefore, even if a barium titanate ceramic material with a dielectric constant of 2000 to 1oooo is used, the dielectric constant after firing is 50.
The exact size is about 0 to 1000, and the high dielectric properties of the barium titanate ceramic dielectric cannot be fully utilized.

In order to obtain a high dielectric constant, it is necessary to increase the firing temperature.
If an electrode paste that does not contain glass frit is used to form the electrode, high-temperature firing is possible, but the lower electrode formed with electrode paste that does not contain glass frit may not adhere to a ceramic substrate such as alumina. It has weak strength and cannot be made into a mechanically stable structure.

For this reason, conventionally, it has been difficult to manufacture high dielectric constant thick film porcelain capacitors due to restrictions on firing temperature.

The present invention produces a high-permittivity thick-film porcelain capacitor characterized by using a calcined porcelain material serving as a dielectric, employing an electrode paste that does not contain glass frit, and performing high-temperature firing. It is the law.

Examples thereof will be described below with reference to the drawings. In FIG. 1, 1 is a ceramic substrate made of alumina, forsterite, etc., and the ceramic substrate 1 is coated with Ag-Pdy Auy Au.
A lower electrode 2 is formed by printing and drying an electrode paste containing no glass frit, such as Pt, Au, Pd, or the like.

3 is a dielectric layer provided on the lower electrode 2, which is made of a titanate-based high permittivity ceramic material such as titanium oxide, magnesium titanate, barium titanate, etc., for example, 81 B a T
i03 t17BaZrO3s 2CaZrO3(+
- 0.4% Wo as an additive to a composition consisting of
.

A.I.

Zn030.2% and Zn00.7% (both by weight) were added at a temperature of 1080° to 1350°C for a holding time of 2.
After being calcined for an hour, it is crushed to about 1 to 5 microns, and then dispersed and mixed in a solution of an organic resin such as ethyl cellulose or polyacrylate and an organic solvent such as terpineol or carpitol acetate for printing. A suitable paste is formed, and this porcelain paste is printed and dried on the lower electrode 2 to form and jelly.

The dielectric layer 3 is printed twice in order to prevent pinholes. Reference numeral 4 designates an upper electrode formed by printing and drying the electrode paste on the dielectric layer 3.

The drying performed during the above steps is all ioo'c~1
It is carried out for 15 to 30 minutes at a temperature of 50°C.

After the above steps are completed, the temperature is 1150℃~1380℃
Main firing is performed for a holding time of 60 minutes or less.

After firing the thick film porcelain capacitor obtained by the method of the present invention,
After being left at room temperature and humidity for 4 hours, the dielectric constant was measured, and the results shown in FIG. 2 were obtained.

In other words, those calcined at 1080°C for 2 hours are
700℃ after main firing at 1310℃~1320℃ for 30 minutes
A high dielectric constant exceeding 0 was recorded.

If the film thickness is 25μ, the capacitance per 17 is 2800P.
The material corresponding to grade F, which was broken and calcined at 1350°C for 2 hours, recorded a dielectric constant exceeding 4000 after main firing at 1240°C to 1260°C for 30 minutes.

If the film thickness is 25μ, the capacitance per 17 is 1400P.
Corresponds to F.

From the above experiments, it was confirmed that when the calcination temperature is high, the dielectric constant decreases, but at a low main calcination temperature, the dielectric constant can be changed to the highest value, and that the film quality after calcination is strong.

Figure 3 shows a thick film porcelain capacitor (with a dielectric constant of 1,500
, 4200, 7200), and it was found that the dielectric constant has no relationship with sagging, and that it shows the same value as that of porcelain before thickening.

That is, -30 to -70 at -30℃ to 25℃, 25
It was confirmed that it exhibited good temperature/capacitance characteristics of -50 to -60% at temperatures between 85°C and 85°C.

Conventional thick film porcelain capacitors are usually fired at 1050°C for 2 hours, and their dielectric constant is 1000 (film thickness 25°C).
In the case of μ, the capacity per 17 was about 350PF), but in the present invention, the porcelain material is preheated at a temperature of 1080°C to 135°C.
By performing calcination at 0°C for a holding time of 0.5 to 2 hours, and main firing at 1150°C to 1380°C for less than 60 minutes, thick film capacitors with a dielectric constant approximately 8 times higher than conventional capacitors are produced. I was able to do this.

In addition, the present invention sets the calcination temperature to 1080°C to 1350°C,
The holding time was 0.5 to 2 hours, the main firing temperature was 1150°C to 1380°C, and the holding time was 60°C.
The reason for setting it below 1 minute is that it has been confirmed through numerous experiments that substances within this range are particularly effective.

In other words, the calcination conditions after blending the raw materials for the titanate-based high-permittivity porcelain mentioned above are such that crystal grains of the titanate-based porcelain material cannot be sufficiently grown if the calcination temperature is 1050°C or less. Therefore, it is impossible to realize the high dielectric constant of this porcelain material.

However, if the pre-firing temperature is higher than 1380°C, the crystal grains will melt and the dielectric constant will drop sharply.

If the calcination time is short, 30 minutes or less, the growth of crystal grains will be insufficient and a high dielectric constant will not be obtained.

It was confirmed that the crystal grains were sufficiently grown within the calcination time of 30 minutes to 2 hours, and no crystal grain growth was observed in the calcination time of 2 hours or more.

That is, by finding conditions for obtaining the largest crystal grains, it is possible to obtain the largest dielectric constant.

Through this calcination, crystal grains grow and the solidified titanic acid-based high dielectric constant porcelain needs to be pulverized to make a paste suitable for printing.

This pulverization needs to produce a paste that has good printability without destroying sufficiently grown crystal grains.

For this reason, when finely pulverized to 1μ or less, a paste with good printability can be obtained, but the crystal grains are severely destroyed, and thick film capacitors constructed using this dielectric paste cannot be heated at temperatures between 1050°C and 1400°C. The dielectric constant obtained when main firing at this temperature is about 1500, which makes it impossible to achieve the purpose of the present invention.
Printability is poor, such as screen clogging, and the resulting non-uniform film thickness causes short circuits between the upper and lower electrodes, making it difficult to obtain stable characteristics.

As described above, the calcination temperature, its holding time, and the pulverized particle size are important requirements for obtaining a high dielectric constant thick film porcelain capacitor, which is the object of the present invention.

Furthermore, as a result of conducting experiments at firing temperatures ranging from 900°C to 1400°C, we found that at temperatures below 1150°C, the dielectric constant (
= 1500 or less), and furthermore, the film quality after firing was brittle and the properties were unstable.

Indeed, at a main firing temperature exceeding 1380°C, the dielectric constant tends to decrease, which is contrary to the purpose of the present invention.

The dielectric constant increases until the main firing time reaches 60 minutes, but the increase in dielectric constant stops after 60 minutes, so there is no need for a firing time of 60 minutes or more.

Based on the above experimental results, the basic technical idea of the present invention can be summarized as using a calcined porcelain material and increasing the temperature of the main firing when forming a thick film porcelain capacitor. The object of the present invention is to make it possible to manufacture a thick film porcelain capacitor having a high dielectric constant that cannot be obtained by conventional thick film capacitor manufacturing methods.

In addition, in the present invention, since an electrode paste that does not contain glass frit is used, the bond between the ceramic substrate and the capacitor element is weaker than in the conventional method. This can be solved by applying a paste with good adhesiveness between the two.

As described above, the method of the present invention can significantly increase the capacitance of a thick film porcelain capacitor, and therefore has the excellent advantage of improving the degree of integration of an integrated circuit that includes this capacitor as a component.

[Brief explanation of drawings]

FIG. 1 is a plan view and side view of a thick film porcelain capacitor according to an embodiment of the present invention, FIG. 2 is a graph showing the relationship between firing temperature and dielectric constant, and FIG. 3 is a graph showing the relationship between temperature and capacitance change rate. 1... Ceramic substrate, 2... Lower electrode, 3... Dielectric layer, 4... Upper electrode.

Claims (1)

[Claims] 1. Print an electrode paste that does not contain glass frit on a ceramic substrate, dry it to form a lower electrode, and then apply a high dielectric constant ceramic material on top of it at a temperature of 1080°C to 1350°C for a holding time of 3.
After calcining for 0 minutes to 2 hours, the porcelain paste was ground to 1 to 5 μm and dispersed and mixed in an organic resin binder, which was then printed and dried to form a dielectric layer. After printing and drying the paste to form the upper electrode,
A method for manufacturing a thick film porcelain capacitor, characterized in that main firing is performed at a temperature of 1150°C to 1380°C for a holding time of 60 minutes or less.