JPH0753237A - Low-temperature sealing composition - Google Patents

Abstract

PURPOSE:To easily improve the statbility and fluidity by excluding thallium from a specified composition. CONSTITUTION:A low-temp. sealing composition A contg., by weight, 60-80% PbO, 3-25% TeO2, 5-15% B2O3, 0.5-3% ZnO, 2-4% Al2O3, 0.5-2% SiO2 where (ZnO+Al2O3+SiO2) <=6% and substantially free of thallium is produced. One or more kinds among CuO, SnO2 and GeO2 are incorporated, as required, into the composition A so that CuO is controlled to 1-5%, SnO2 to 1-5% and GeO2 to 1-3% to produce a low-temp. sealing composition B. A low-expansion ceramic filler (having <=20mum particle diameter) such as lead titanate, niobium pentoxide, beta-eucryptite, cordiertie and zirconia is incorporated into the composition A or B by 10-50vol.% to produce a low-temp. sealing composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low temperature sealing composition, and more particularly to a low temperature sealing composition suitable for hermetically sealing glass or ceramics having a coefficient of thermal expansion of 70 to 120 × 10 ^-7 / ° C. Regarding

[0002]

2. Description of the Related Art Conventionally, a low melting glass powder or a composite material containing a ceramic filler has been used for sealing glass, ceramics or their mutual mutual adhesion. Usually, it is desirable to perform the sealing treatment at a temperature as low as possible in order to avoid adverse effects on the material to be sealed, and generally it is performed at a temperature of 500 ° C. or less. Therefore,
The low-melting glass to be used naturally has a low softening point lower than the above temperature, but since such a low-melting glass has a high coefficient of thermal expansion, it has a low expansion coefficient to match the adherend and the coefficient of thermal expansion. Often used with added filler.

As a low melting point sealing glass, PbO-B is used.
₂ O ₃ based glass are known PbO-B ₂ O ₃ -ZnO system. However, because these compositions are unstable,
As a practical composition, glass stabilizing components such as SiO ₂ and Al ₂ O ₃ must be added to some extent, and as a result, the sealing temperature rises and the fluidity of the glass deteriorates, resulting in airtight sealing. May reduce the reliability of the.

Further, as a component for lowering the softening point, Tl
Those containing ₂ O are disclosed in JP-A-63-315536 and JP-A-4-214045.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
_{Although 2} O-containing compositions can lower the sealing temperature, they contain thallium, which is a harmful substance, so it is necessary to install equipment to prevent dust scattering in each process during manufacturing and use. However, the problem of environmental hygiene remains.
Further, the frit for low-temperature sealing disclosed in Japanese Patent Laid-Open No. 63-315536 has a very large coefficient of thermal expansion of the glass as the base material, and therefore a large amount of low expansion is required to match the coefficient of thermal expansion with ceramics such as alumina. Since a filler has to be mixed, there is a drawback that the fluidity at the time of sealing is impaired.

The present invention has been made in view of these circumstances, is substantially free of thallium, has excellent fluidity at a temperature of 500 ° C. or less, and has a coefficient of thermal expansion of about 70 to 12.
It is an object of the present invention to provide a low-temperature sealing composition suitable for hermetically sealing glass or ceramics at 0 × 10 ⁻⁷ / ° C.

[0007]

SUMMARY OF THE INVENTION The present invention, in order to achieve the above object, a PbO-B ₂ O ₃ -TeO ₂ based glass was introduced TeO ₂ is effective in stabilizing the glass as a basic composition, softening ZnO, Al ₂ O ₃ , Si for raising the point
By limiting the O ₂ content to a small amount, a sealing material having excellent fluidity at low temperatures was obtained. Further, the coefficient of thermal expansion is kept low by adding CuO, SnO ₂ , and GeO ₂ , and the addition amount of the low expansion filler can be suppressed to a low rate.

That is, the present invention is based on the weight percentage of PbO.
_{60~80%, TeO 2 3~25%,} B 2 O 3 5~1
5%, 0.5~3% ZnO, Al 2 O 3 2~4%, S
iO ₂ 0.5 to 2% (however, ZnO, Al ₂ O ₃ , S
The low-temperature sealing glass is characterized by containing a total amount of iO ₂ of 6% or less) and containing substantially no thallium. Further, at least one of CuO, SnO ₂ and GeO ₂ is contained, and the content of each is percentage by weight of CuO 1-5%, SnO ₂ 1-5%, GeO _2.
It is obtained by the range of ₂ 1-3%.

Further, in order to adjust the coefficient of thermal expansion with the object to be sealed, lead titanate, niobium pentoxide, β
-Low expansion ceramic filler such as eucryptite, cordierite, zircon, etc. in a volume percentage of 20 to 50%
It was added so that

[0010]

The function of each component of the glass constituting the present invention and the reason for limiting the composition range as described above will be described below.

PbO is a main component for constituting a low melting point glass, and if it is less than 60%, the low melting property cannot be maintained, and
If it exceeds 0%, the glass becomes unstable.

TeO ₂ is effective in stabilizing the glass as described above, and is an essential component in the present invention as a component for lowering the viscosity of the glass. Since the softening point rises and the coefficient of thermal expansion increases, it is not practical as a glass for low-temperature sealing. It is preferably in the range of 4% to 20%.

B ₂ O ₃ has an effect of stabilizing the glass, but if it is less than 5%, the glass is crystallized, and if it exceeds 15%, the softening point becomes too high and the water resistance deteriorates. It is preferably used in the range of 7% to 13%.

ZnO is also a stabilizing component of glass,
If it is less than 0.5%, the effect is not obtained, and if it exceeds 3%, the softening point is increased and the fluidity is deteriorated.

Al ₂ O ₃ has an effect of stabilizing glass and enhancing chemical durability, but if it is less than 2%, its effect is small, and if it exceeds 4%, the softening point becomes too high. TeO
_{When 2} is contained beyond the above preferable range, TeO
_{Since the} effect of stabilizing glass by ₂ becomes less significant, Al ₂ can stabilize glass with a relatively small content.
O ₃ is preferably contained at least 2.2% or more. Therefore, it is more preferably in the range of 2.2% to 3.5%.

SiO ₂ is a component for improving the water resistance, but if it is less than 0.5%, it is not effective, and if it exceeds 2%, the softening point becomes high, which is not preferable.

ZnO, Al ₂ O ₃ and SiO ₂ all have the effect of stabilizing the glass, but when the content of TeO ₂ is high, the softening point tends to be high, so these components are included. It is not preferable to add more than 6% of the total amount because it causes a further increase in the softening point and hinders the achievement of the above object of the present invention.

In addition to the above components, CuO, SnO ₂ , G
By including at least one of eO ₂ within the above range, the coefficient of thermal expansion of glass can be lowered without increasing the softening point. Therefore, by adding these components, it is possible to obtain a glass having a lower expansion, and even when the low expansion filler is added, the addition amount can be suppressed to a small amount. However, each component is 1%
If it is less than the above, the effect is small, and if it exceeds the upper limit of each content, CuO tends to crystallize the glass,
SnO ₂ is not preferable because the viscosity of the glass becomes too high, resulting in impaired fluidity. Also GeO
_{In the case of 2,} the raw materials are expensive and the product cost increases, so many cannot be used.

In the present invention, as described above, the low expansion ceramics fillers 10 to 10 such as lead titanate, niobium pentoxide, β-eucryptite, cordierite and zircon are used.
50% (volume percentage) can be used in addition to glass. In order to improve the fluidity at the time of sealing, it is preferable that the amount of the filler added is as small as possible. Therefore, the use of negative expansion lead titanate or niobium pentoxide is effective.

Regarding the particle size of these fillers, it is desirable to use those having a particle size of 20 μm or less in consideration of fluidity and airtightness, but when applied to those having a small coefficient of thermal expansion, those having a particle size of 20 to 60 μm. May be used in a relatively low addition amount so as not to impair the fluidity. In this case, if a minus expansion filler or the like is used, the filler addition amount is 2
It may be less than 0% by volume. The preferable amount of the filler added to the glass of the present invention is 20 to 50% by volume, but the lower limit of 20% is merely a guideline for clearly showing the effect of reducing the thermal expansion coefficient by the addition of the filler. It may be appropriately determined from the relationship with the coefficient of thermal expansion. However, if it exceeds 50%, the fluidity is adversely affected, so it is better to suppress it to 50% or less at the maximum.

[0021]

EXAMPLES Examples of the present invention will be described below. Weighed and compounded red lead, tellurium oxide, boric acid, zinc oxide, silica stone powder, aluminum hydroxide, copper oxide, tin oxide, and germanium oxide so as to have the compositions shown in Tables 1 to 3, and used them in platinum crucibles. 850 ℃ in an electric furnace
It was heated and melted for 1 hour. The melt was sufficiently stirred for defoaming and homogenization, poured onto an iron plate, then cooled and pulverized at an appropriate temperature to obtain a low melting point glass.

The thermal expansion coefficient (α), glass transition point (Tg), yield point (Tc) of the obtained glass, and the evaluation results of glass stability and fluidity are shown in the table. Here, the coefficient of thermal expansion is a value measured in the range of 30 to 250 ° C. using a thermomechanical analysis method, and the glass transition point and the yield point are differential thermal analysis (D
The values obtained by the TA) method are shown. Further, the stability of the glass was judged from the presence or absence of a crystallization peak in the DTA curve of the differential thermal analysis. Regarding the fluidity, powder glass having a diameter of 45 μm or less was compression-molded into a button having a diameter of 20 mm, which was heated at 400 ° C. for 10 minutes, and a button having a diameter larger than 24 mm was judged to be good. Good stability and fluidity from the above results
Poor ones are shown by x in the table. The glass composition in the table is shown by weight percentage.

[0023]

[Table 1]

[Table 2]

[Table 3]

The glasses in Table 1 are examples corresponding to claim 1 of the present invention, and Table 3 is a comparative example. The glasses shown in Table 1 all have a coefficient of thermal expansion of 130 × 10 ⁻⁷ / ° C.
And the yield point also shows a low value below 350 ° C.
A glass having good stability and fluidity was obtained. On the other hand, the sample No. The glass of No. 3 has a high TeO ₂ content, and therefore has a high yield point and a high coefficient of thermal expansion, and has poor fluidity and is not practical. In addition, the sample No. of the comparative example not containing TeO ₂ . In No. 2, the glass was inferior in stability and was easily crystallized by the heat treatment at the time of sealing, and thus the glass of Comparative Example could not satisfy both the stability and the fluidity.

The glasses in Table 2 are examples corresponding to claim 2 of the present invention. With the addition of CuO, SnO ₂ and GeO ₂ , there was almost no increase in the yield point as compared with the glasses in Table 1, and the coefficient of thermal expansion was a low value of approximately 120 × 10 ⁻⁷ / ° C. or less. As a result of the test, the fluidity of these sample glasses was extremely good.

Table 4 shows examples containing low expansion fillers. Glass No. in the table Is the sample No. of Tables 1 to 3. Is. In addition, as a comparative example, the comparative example No. 1
The results when the glass of No. 3 was used are also shown.

[0027]

[Table 4]

The samples shown in Table 4 are prepared by using lead titanate and niobium pentoxide as fillers and adjusting the coefficient of thermal expansion for sealing soda lime glass. All of the samples show values close to the coefficient of thermal expansion of soda lime glass of 88 × 10 ⁻⁷ / ° C., but those using the glass of the comparative example have a relatively high coefficient of thermal expansion of the base material glass, and therefore are relatively large in adjustment. Needed filler.

These powders were processed into a paste, applied between test pieces of soda lime glass, dried and solidified, and then heated at 450 ° C. for 20 minutes, and the sealed state after cooling was observed. In the examples according to the present invention, neither devitrification nor cracks were generated in the sealing part, and the wettability was good, so that there were no bubbles in the sealing part and the two blue sheet glasses were firmly sealed, A tight seal was observed. On the other hand, in Comparative Example, the fluidity was poor, and the glass was not spread over the entire sealing surface. In addition, residual bubbles and partially crystallized parts were observed, and 2
The sheet of blue plate was easily peeled off.

[0030]

As described above, the low-temperature sealing composition of the present invention does not contain thallium which is a harmful substance, so that
It is not necessary to install equipment to prevent dust scattering in processes such as use, and products can be handled easily. Further, since the glass itself has high stability and excellent fluidity, it is possible to easily manage the sealing conditions and reduce defects such as insufficient strength of the sealed portion due to devitrification.

Since the coefficient of thermal expansion of glass is small,
It can be applied to sealing relatively low expansion products by using only glass, and even when low expansion filler is used to match the thermal expansion coefficient with the adherend, the addition amount can be reduced, and even after the filler is added. It can maintain excellent fluidity.

Therefore, the low-temperature sealing composition of the present invention has good wettability on the sealing surface and does not cause air bubbles or leaks in the sealing portion, so that it is very suitable for air-sealing glass, ceramics, or each other. It is suitable.

Claims (3)

[Claims] 1. PbO 60 to 80% in weight percentage,
TeO ₂ 3-25%, B ₂ O ₃ 5-15%, ZnO
0.5-3%, Al ₂ O ₃ 2-4%, SiO ₂ 0.5-
A low-temperature sealing composition comprising 2% (however, the total content of ZnO, Al ₂ O ₃ , and SiO ₂ is 6% or less) and containing substantially no thallium. _{2. At} least one component of CuO, SnO ₂ and GeO ₂ is contained, and the content of each is percentage by weight, CuO 1-5%, SnO ₂ 1-5%, G
The low temperature sealing composition according to claim 1, wherein eO ₂ is in the range of 1 to 3%. 3. A low expansion ceramics filler such as lead titanate, niobium pentoxide, β-eucryptite, cordierite, zircon or the like is contained in an amount of 10 to 50% by volume. The composition for low-temperature sealing.