JPH10236845A - Low melting point leadless glass composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass with low sealing temp. which enables tight sealing and shows improved adhesion strength by mixing SiO2 , B2 O3 , Al2 O3 , BaO, MgO+ CaO+ZnO and Li2 O+Na2 O+KO and fusing and vitrifying the mixture. SOLUTION: This leadless glass compsn. having a low melting point for sealing or coating a ceramic material is produced by mixing 5 to 15wt.% SiO2 , 25 to 45wt.% B2 O3 , 1 to 8wt.% Al2 O3 , 25 to 50wt.% BaO, 0 to 20wt.% MgO+ CaO+ZnO, 0 to 10wt.% LiO2 +Na2 O+K2 O in total >=85wt.%, 0 to 1wt.% clarifying agent such as As2 O3 and Sb2 O3 , 0 to 2wt.% coloring agent such as CoO and Fe2 O3 , and if necessary, <=30wt.% ceramic powder such as cordierite, zircon and β-eucryptite, and then fusing by heating to vitrify, slowly cooling and pulverizing. The obtd. compsn. has 50×10<-7> to 80×10<-7> / deg.C average coefft. of thermal expansion at 50 to 700 deg.C after calcined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low melting point lead-free glass composition capable of sealing or coating a ceramic material, for example, a ceramic material containing alumina (Al ₂ O ₃ ) as a main component at a temperature of 900 ° C. or less.

[0002]

2. Description of the Related Art In recent years, ceramic materials containing alumina as a main component have been used in many fields, but these ceramic materials are often used in a form of composite with various metal materials. When sealing or coating such materials, it is desirable to be able to work at as low a temperature as possible so as not to damage the associated metallic material, in particular 90
If the operation can be performed at 0 ° C. or lower, many usable metal materials are suitable.

[0003]

As a material for sealing or coating a ceramic material containing alumina as a main component at a temperature of 900 ° C. or less, many low melting point glasses called solder glass (glass frit) are commercially available. All of them have a drawback that they contain a large amount of harmful substance PbO and increase costs for environmental management in work, waste disposal, and the like. A material containing no PbO generally has a disadvantage that the working temperature is high and the working cannot be performed at a low temperature of 900 ° C. or less.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a barium borate glass composition containing essentially no PbO and having a softening point of 750 ° C. or less. And a low melting point lead-free material for sealing or coating a ceramic material, wherein the average coefficient of thermal expansion at 50 to 300 ° C. after firing is in the range of 50 × 10 ⁻⁷ to 80 × 10 ⁻⁷ / ° C. A glass composition is provided.

In a preferred embodiment, the barium borate glass composition is expressed in terms of weight: 5 to 15% of SiO ₂ , 25 to 45% of B ₂ O ₃ , 1 to 8% of Al ₂ O ₃ , 25 to 50% of BaO , MgO + CaO + 0~20% ZnO , Li 2 O + Na 2 O + K 2 O 0~10%, by weight of component, the low melting point lead-free glass composition total amount accounts for more than 85% of the Bariumuhou glasses composition of the components I will provide a.

That is, the low-melting-point lead-free glass composition of the present invention is a barium borate glass composition essentially containing no PbO, and has a softening point of 750 ° C. or less.
The average coefficient of thermal expansion at 0 to 300 ° C. is 50 × 10 ⁻⁷ to 80 ×
When the temperature is within the range of 10 ^-7 / ° C, sealing can be performed at a temperature of 900 ° C or less, and a hermetic seal or a film having high adhesive strength can be obtained by firmly bonding with alumina ceramics. Or a coating composition.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred glass compositions for the glass composition of the present invention are described below. Hereinafter, when simply described as%, it means weight%. SiO ₂
If it exceeds 15%, the viscosity of the glass increases, and firing at 900 ° C. or lower becomes difficult. Preferably it is 13% or less. If it is less than 5%, the glass becomes unstable, and crystal precipitation occurs during melting and cooling during the production of the glass, and sealing or coating performance may be deteriorated. It is preferably at least 8%.

If B ₂ O ₃ exceeds 45%, crystal precipitation occurs during melting and cooling during glass production, and there is a possibility that sealing or coating performance may be deteriorated. Preferably 40%
It is as follows. If it is less than 25%, the viscosity of the glass increases, and 9
Baking at a temperature of 00 ° C. or less becomes difficult. It is preferably at least 30%.

If the content of Al ₂ O ₃ exceeds 8%, the viscosity of the glass increases, so that firing at 900 ° C. or less becomes difficult. Preferably 6
% Or less. If the content is less than 1%, the glass becomes unstable, and the bonding property with strong ceramics cannot be obtained. It is preferably at least 3%.

If the content of BaO exceeds 50%, the glass becomes unstable, and crystal deposition occurs during melting and cooling during the production of the glass, so that sealing or coating performance may be deteriorated. Preferably it is 40% or less. If it is less than 25%, the viscosity of the glass increases, and firing at 900 ° C. or less becomes difficult.
It is preferably at least 30%.

For MgO, CaO and ZnO,
Although not essential, any one or more of them may be contained for adjusting the coefficient of thermal expansion. However, if the total amount exceeds 20%, 50
The average coefficient of thermal expansion at up to 300 ° C. is 50 × 10 ⁻⁷ to 80 × 1
It is difficult to enter the range of 0 ^-7 / ° C. Preferably, the total amount is 15% or less.

As for Li ₂ O, Na ₂ O and K ₂ O, any one or more of them may be contained for improving the solubility, though not essential. However, if the total amount exceeds 10%, 50
The average coefficient of thermal expansion at up to 300 ° C. is 50 × 10 ⁻⁷ to 80 × 1
It is difficult to enter the range of 0 ^-7 / ° C. Preferably, the total amount is 5% or less.

In a preferred embodiment of the present invention, the total amount of the above components accounts for 85% or more of the glass composition. In order to ensure the effect more, it is preferable to account for 90% or more of the glass composition.

The glass composition of the present invention contains known fining agents (As ₂ O ₃ , Sb ₂ O ₃₎ as long as the effects of the present invention are not impaired.
Etc.) in a total amount of 1% or less of the glass composition and a coloring agent (Co
O, Fe ₂ O _3, etc.) in a total amount of 2% or less of the glass composition.

When the glass composition of the present invention is used for sealing or coating, cordierite, zircon, β
-It is also possible to control the thermal expansion coefficient by mixing a ceramic powder such as eucryptite or forsterite in a range of 30% or less based on the total amount of the glass powder and the ceramic powder.

The glass composition of the present invention has a viscosity of 50 to 3 after firing.
The average thermal expansion coefficient at 00 ° C. is 50 × 10 ⁻⁷ to 80 × 10 ^−7.
/ ° C. Outside of this range, sufficient bonding strength cannot be obtained because the difference in thermal expansion coefficient between the alumina ceramic and the fired glass is large. More preferably, 5
The average coefficient of thermal expansion at 0 to 300 ° C. is 60 × 10 ⁻⁷ to 75 ×
10 ⁻⁷ / ° C. Further, the glass composition of the present invention has a softening point of 750 ° C. or less. Therefore, sealing at 900 ° C. or less is possible.

The composition of the present invention is usually prepared by mixing a powder of this composition with water or an organic solvent to form a paste, applying the mixture to a ceramic-based material to be bonded or a material to be coated, and baking it. Alternatively, a coated material is obtained, but a powder compact is formed by pressing, a sintered compact obtained by further calcining the pressed compact near the softening point of glass, or a powder mixed with a solvent to form a slurry. A joined body can also be obtained by using a sheet-shaped product.

Further, the composition of the present invention can be obtained by casting a molten solution into a predetermined shape without pulverization, and then further processing the solution to a predetermined size to obtain a bonded composition as a sealing composition. .

[0019]

EXAMPLES Table 1 shows Examples (Examples 1 to 5) and Comparative Examples (Examples 6 to 7) of the present invention. Composition shown in Table 1 (wt%)
According to the above, each raw material was weighed so as to become 1 kg as a final composition, and mixed with a mixer. After mixing, the mixture was melted in a platinum crucible at 1300 ° C. for 1 hour in an electric furnace. After that, the block was taken out of the furnace and molded on an iron plate.
Was transferred to an electric furnace having a temperature of, and gradually cooled.

For Examples 1 to 3 and 6 to 7, the obtained blocks were crushed in an alumina mortar and then finely pulverized in a ball mill, and passed through a 150-mesh sieve to obtain powder.
In Examples 4 and 5, the obtained block was cut and ground into a shape suitable for the following test to obtain a predetermined test piece (all of the coating properties were tested with powder).

First, a differential thermal analysis (DT) of the obtained glass was performed.
A) was performed to determine the softening point, and the results are shown in Table 1. Regarding the coefficient of thermal expansion, each sample was held at a temperature 150 ° C. higher than the softening point for 20 minutes, fired, cooled to room temperature, and then subjected to an average thermal expansion coefficient of 50 to 300 ° C. by a TMA analyzer (differential thermal dilatometer). It was measured.

Regarding the bonding strength, α-alumina
Two plates having a thickness of 10 mm × 10 mm × 2 mm were bonded together with the composition shown in Table 1 at a temperature 150 ° C. higher than the softening point.
After holding for a minute, it was baked and joined. Thereafter, the shear strength was measured by a strength tester (autograph). The shear strength is desirably 300 kg / cm ² or more.

With respect to the airtightness, α-alumina tube (outer diameter 30 mm, inner diameter 26 mm, length 40 mm) and β
-Alumina plate (50 mm long, 50 mm wide, 2 m thick)
m) was glued together with the composition shown in Table 1 so that one end of the tube was covered with a plate, held at a temperature 150 ° C. higher than the softening point for 20 minutes, and fired and joined. The He leak test was performed by connecting the open end of the tube to a He leak tester and blowing He gas on the joint between α-alumina and β-alumina. Helium leak rate is 10 ^-6 atm · cc
/ Sec or more was evaluated as poor, and less than / sec was evaluated as good.

Regarding the coating property, the composition shown in Table 1 was dispersed in water in a porcelain containing alumina as a main component (coefficient of thermal expansion: 70 × 10 ⁻⁷ / ° C.) to form a slip. It was applied to a thickness of about 100 μm, dried, and baked at 900 ° C. for 20 minutes. After firing, those having a glossy glass surface and no cracks were evaluated as good.

[0025]

[Table 1]

As can be seen from Table 1, all of the compositions of the present invention can be sealed or coated at 900 ° C. or lower, and have an average thermal expansion coefficient of 50 to 300 ° C. of 50.
× is in the range of ^{10 -7 ~80 × 10 -7 / ℃} , Al 2 O 3
A strong bonded body with a ceramic as a main component or a coating material having high film adhesion strength can be obtained.

[0027]

As described above, the composition of the present invention comprises 90
A sealing operation or a coating operation can be performed at a temperature of 0 ° C. or less, and a ceramic having alumina as a main component can be hermetically sealed or a film having a high adhesive strength can be obtained. Since the sealing temperature is low, many metal materials can be applied to the ceramic mainly composed of alumina of the article to be joined. For example, when looking at electrode materials, relatively inexpensive materials such as Ni and Cu can be used for sealing at 900 ° C. or lower, but Mo,
An expensive material such as W is required.

The average thermal expansion coefficient at 50 to 300 ° C. is 50 ×
Since it is in the range of 10 ^-7 to 80 × 10 ^-7 / ° C., a strong bonding strength can be obtained, and thus a hermetic seal can be obtained or a coating film having a high adhesion strength can be obtained. By not containing PbO, there is no harm, safe operation can be performed, and waste disposal is easy.

Claims (2)

[Claims] (1) It contains essentially no PbO and has a softening point of 75
A barium borate glass composition having a temperature of 0 ° C. or less, which has an average coefficient of thermal expansion at 50 to 300 ° C. after firing of 50 × 10 ^−7.
A low melting point lead-free glass composition for sealing or coating a ceramic material, wherein the composition is in a range of from about 80 × 10 ⁻⁷ / ° C. 2. The barium borate glass composition is expressed by weight: 5 to 15% of SiO ₂ , 25 to 45% of B ₂ O ₃ , 1 to 8% of Al ₂ O ₃ , 25 to 50% of BaO, MgO + CaO + ZnO 0 _2. The low melting point lead-free glass composition according to claim 1, wherein the composition contains Li ₂ O + Na ₂ O + K ₂ O 0-10%, and the total amount of the components accounts for 85% or more of the barium borate glass composition. Stuff.