JPH09169543A - Glass composition for overcoat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a glass compsn. capable of forming an overcoating glass film having high surface smothness and high dielectric strength by blending principal glass power having a specified softening point with low softening point glass powder and a powdery refractory filler having a low dielectric constant. SOLUTION: The glass compsn. consists of 75-96wt.% principal glass powder having <=700 deg.C softening point, 2-10wt.% low softening point glass powder whose softening point is lower than that of the principal glass powder by 50-250 deg.C and 2-15wt.% powdery refractory filler having a low dielectric constant εof <=6.5%. The weight ratio of the low softening point glass powder to the filler is preferably 0.25-1.50%. Silicon dioxide, mullite or cordierite may be used as the filler but silicon dioxide having the lowest dielectric constant and stable quality is preferably used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcoat glass composition, and more particularly to an overcoat glass composition having a high surface smoothness and a high withstand voltage used in the field of thick film heaters and the like.

[0002]

2. Description of the Related Art When a thick film circuit is formed on a ceramic substrate such as alumina, an overcoat glass film is formed to protect the circuit.

The overcoat glass film is required to have various properties depending on its use. For example, in the case of a thick film heater component, an overcoat glass film is formed for electrode protection. This overcoat glass film has high surface smoothness (Rz ≦ 1.5 μm) and high dielectric strength characteristics. Is required.

[0004]

For the overcoat glass film, a glass composition containing a glass powder having a softening point of 700 ° C. or less as a main component is used as a paste, and the paste is printed by a screen printing thick film method to give a temperature of 900 ° C. or less. The dielectric strength of the glass film is essentially influenced by the dielectric constant of the glass. Therefore, there is a disadvantage that the composition of the glass powder has to be changed in order to increase the withstand voltage.

Therefore, instead of changing the composition of the glass powder, a method of adding a refractory filler powder having a low dielectric constant to improve the dielectric strength characteristics has been studied. However, according to this method, the surface smoothness of the glass film may be impaired, and in some cases, the glass film may not be densified and the dielectric strength characteristics may deteriorate.

An object of the present invention is to provide a glass composition for overcoat, which is capable of forming an overcoat glass film having a high surface smoothness and a high dielectric strength by using a low dielectric constant refractory filler powder. That is.

[0007]

As a result of various experiments, the present inventors have found that the above object can be achieved by adding a predetermined amount of a low softening point glass powder together with a low dielectric constant filler powder. It is proposed as an invention.

That is, the glass composition for overcoating of the present invention has a softening point of 700 ° C. or lower (preferably 500 to 7).
00 ° C) main glass powder 75 to 96% by weight, low softening point glass powder 2 to 10% by weight having a softening point lower than that of the main glass powder by 50 to 250 ° C, and low dielectric constant ε of 6.5 or less. The refractory filler powder is 2 to 15% by weight.

In the present invention, the main glass powder influences the basic characteristics of the overcoat glass film, and PbO-SiO generally used for overcoating.
_2- B ₂ O ₂ -based amorphous glass can be used. Among them, PbO 45 to 75%, SiO _{2 2 to} 40% by weight,
_{B 2 O 3 2~30%, Al} 2 O 3 0~10%, Zn
It is preferable to use a glass having a composition of 0-30% O. When the softening point of the main glass powder is higher than 700 ° C., the firing temperature of the overcoat glass film becomes high, and the lower electrode characteristics are likely to deteriorate during firing. Further, if the content of the main glass component is less than 75% by weight, desired characteristics cannot be obtained, and if it is more than 96% by weight, the ratio of other components becomes relatively small and improvement of the dielectric strength cannot be expected.

The low softening point glass powder is a component which prevents the deterioration of the surface smoothness and the denseness of the glass film due to the addition of the refractory filler powder and stabilizes the glass film, and has a softening point of 50 than that of the main glass powder. Known glass can be used as long as it is a glass powder having a temperature lower by 250 ° C. Especially Pb in wt%
O 55-80%, SiO ₂ 2-40%, B ₂ O ₃ 2
_{~30%, Al 2 O 3 0~10} %, ZnO 0~30
Preference is given to using glasses with a composition of%. The difference in softening point between the low softening point glass and the main glass powder is 5
If the temperature is below 0 ° C or the content of low softening point glass powder is 2
If it is less than 10% by weight, the effect is not effective. If the difference in softening point from the main glass powder is more than 250 ° C or if it is more than 10% by weight, the reaction with the electrodes becomes remarkable and the dielectric strength characteristics of the glass film are reduced. It causes deterioration.

The low dielectric constant refractory filler powder is a component added to increase the dielectric strength of the glass film, and the dielectric constant ε of silicon dioxide, mullite, cordierite, etc. is 6.
Less than 5 are used. Among them, the lowest dielectric constant,
Further, it is preferable to use silicon dioxide whose quality is stable. The reason for limiting the dielectric constant ε of the refractory filler powder to 6.5 or less is that if the dielectric constant is larger than this, it hardly contributes to the improvement of the dielectric strength voltage. Further, if the content of the refractory filler powder is less than 2% by weight, its effect is not exerted, and if it is more than 15% by weight, the surface smoothness of the glass film is impaired, or the glass film is not densified and the dielectric strength characteristics are deteriorated. Will end up.

In the present invention, the ratio of the content of the low softening point glass powder to the content of the low dielectric constant refractory filler powder is preferably 0.25 to 1.50 by weight. If this ratio is smaller than 0.25, the effect of adding the low softening point glass powder becomes small, the surface smoothness of the glass film is impaired, or the glass film is not densified, and the withstand voltage is apt to decrease. . On the other hand, when it is larger than 1.50, the effect of adding the low dielectric constant filler powder is small, and it is impossible to expect a large improvement in withstand voltage.

The glass composition for overcoating of the present invention contains, in addition to the above-mentioned components, up to 5% by weight of a refractory filler powder such as alumina, zirconia or zircon for strengthening and stabilizing the glass film, and glass. It is possible to add up to 5% by weight of refractory inorganic pigment powder for coloring the film.

Next, a method for forming an overcoat glass film using the glass composition for overcoat of the present invention will be described.

First, a main glass powder, a low softening point glass powder,
The low dielectric constant refractory filler powder (and other refractory filler powder and inorganic pigment powder as required) are mixed in the above proportions to obtain a mixed powder. Next, the mixed powder is uniformly kneaded with a vehicle in which an organic binder is dissolved in an organic solvent to prepare a paste. The paste thus obtained is printed on a thick film circuit (for example, on an electrode of a thick film heater component) by a screen printing thick film method and baked at 900 ° C. or lower to form an overcoat glass film. be able to.

[0016]

When only the low-dielectric-constant refractory filler powder is added to the conventional overcoat glass composition, the surface smoothness of the glass film is impaired, or the glass film is not densified and the dielectric strength characteristics are deteriorated. However, the coexistence of the low softening point glass powder prevents deterioration of the surface smoothness and the denseness of the glass film due to the addition of the refractory filler powder, and a stable glass film can be obtained. As a result, it is possible to obtain an overcoat glass film having high surface smoothness equivalent to that of a conventional product and higher dielectric strength characteristics.

[0017]

EXAMPLES Hereinafter, the glass composition for overcoating of the present invention will be described based on Examples.

Table 1 shows main glass powders (Samples A and B) and low softening point glass powders (Samples C and D) used in Examples and Comparative Examples.

[0019]

[Table 1]

Tables 2 to 5 show examples (Sample Nos. 1 to 14) and comparative examples (Sample Nos. 15 to 20) of the present invention.
Is shown.

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

[Table 5]

Each sample was prepared as follows.

First, glass powder having the composition shown in Table 1 was prepared. The average particle size of the glass powder was set to 1.5 to 3.0 μm, which is suitable for screen printing. Further, low dielectric constant refractory filler powders (silicon dioxide, mullite, cordierite) shown in Tables 2 to 5 and other additive components (alumina, zirconia, zircon, refractory inorganic pigments) were prepared. Silicon dioxide, mullite, cordierite, alumina, zirconia and zircon have an average particle size of 0.5 to 0.5.
The one having a thickness of 2.5 μm was used. As the refractory inorganic pigment, an Fe-Cr-Co black pigment having an average particle size of 1.0 µm was used.

Then, glass powder, low dielectric constant refractory filler powder and other additive components were uniformly mixed in the proportions shown in Tables 2 to 5 to obtain samples.

A glass film was formed using each of the samples thus obtained, and the surface smoothness and dielectric strength characteristics were evaluated. The results are shown in Tables 2 to 5.

As is apparent from the table, the sample No. which is an example of the present invention. The surface smoothness of 1 to 10 is Rz = 1.4.
Sample No. using only glass A and having a withstand voltage of 52 ACV / μm or more The surface smoothness is equivalent to that of No. 15, and higher dielectric strength characteristics are obtained. Similarly, sample No. 1 which is an example of the present invention. 11-
Sample No. 14 having a surface smoothness of Rz = 1.4 μm or less and a withstand voltage of 51 ACV / μm or more, and Sample No. 14 using only glass B was used. Surface smoothness equivalent to that of No. 17 was obtained, and higher dielectric strength characteristics were obtained.

On the other hand, sample No. 1 in which only the low dielectric constant refractory filler powder was added to glass A or glass B was used. 16 and 1
8, the surface smoothness was Rz = 2.3 μm and 2.7 μm.
m, withstand voltage of 52ACV / μm and 50ACV / μm
Although it was confirmed that the dielectric strength characteristics were improved by adding the filler, the surface smoothness deteriorated. In addition, Sample No. 1 containing too much low softening point glass powder was added. No. 19 has a significant reaction with the electrodes, and therefore has a dielectric strength of 39 ACV / μ.
m, while the addition amount of the low dielectric constant refractory filler powder is too large. 20 has a surface smoothness of Rz = 3.
3 μm, withstand voltage was 28 ACV / μm, and all characteristics were extremely deteriorated.

For the surface smoothness, each sample was kneaded with a vehicle in which ethyl cellulose was dissolved in tapineol to prepare a paste, which was screen-printed on an alumina substrate, and subsequently at about 800 to 820 ° C. After firing for 10 minutes, the surface of the formed glass film was measured with a stylus type surface roughness meter.
The 10-point average roughness Rz was measured under the conditions of a measuring distance of 8.0 mm and a measuring speed of 0.3 / mm.

The withstand voltage was measured as follows.
First, each sample was made into a paste in the same manner as above, and after screen-printing this on an electrode formed on an alumina substrate,
It was baked at about 800 to 820 ° C. for 10 minutes. Next, electrodes were formed again on the upper surface of the glass film formed, and an AC power supply voltage was applied between the upper and lower electrodes to measure the dielectric breakdown voltage. Further, assuming that the measured value of the breakdown voltage and the glass film thickness are in a proportional relationship, the breakdown voltage per film thickness of 1 μm was calculated as the dielectric strength voltage. The upper and lower electrodes are electrode materials (Ag-Pt conductor).
Is applied to a circular pattern having a radius of 5 mm by screen printing, and this is baked at about 850 ° C. for 10 minutes.

[0033]

INDUSTRIAL APPLICABILITY Although the glass composition for overcoating of the present invention contains the low dielectric constant refractory filler powder, the obtained glass film has a reduced surface smoothness and densification. Never. Therefore, it is possible to form an overcoat glass film having higher dielectric strength characteristics while maintaining high surface smoothness equivalent to that of a conventional product without changing the composition of the main glass powder. For this reason,
It is suitable for protecting electrodes such as thick film heater parts.

Claims (6)

[Claims] 1. A main glass powder 7 having a softening point of 700 ° C. or lower.
5 to 96% by weight, with a softening point of 50 to 2 compared to the main glass powder
2 to 10% by weight of low softening point glass powder at 50 ° C. and low dielectric constant refractory filler powder 2-1 having a dielectric constant ε of 6.5 or less.
A glass composition for an overcoat, comprising 5% by weight. 2. The weight ratio of the content of the low softening point glass powder to the content of the low dielectric constant refractory filler powder is 0.25 to 1.50. Glass composition for coating. 3. Main glass powder is PbO 45 at a weight percentage.
_{~75%, SiO 2 2~40%,} B 2 O 3 2~30
%, Al ₂ O ₃ 0 to 10%, ZnO 0 to 30%, and the glass composition for overcoat according to claim 1. 4. The low softening point glass powder is PbO in a weight percentage.
55-80%, SiO ₂ 2-40%, B ₂ O ₃ 2
~ 30%, Al ₂ O ₃ 0-10%, ZnO 0-30%
The glass composition for overcoat according to claim 1, wherein the glass composition has the following composition. 5. The glass composition for overcoat according to claim 1, wherein the low dielectric constant refractory filler powder is silicon dioxide. 6. The overcoat glass composition according to claim 1, which is used for forming an overcoat glass film for protecting an electrode of a thick film heater component.