Sealing glass

Abstract

A glass for sealing of the present invention includes as a glass composition, in terms of mol %, 60% to 80% of SiO.sub.2, 8% to 5.8% of B.sub.2O.sub.3, 12% to 18.7% or Li.sub.2O+Na.sub.2O+K.sub.2O, and 2% to 12% of MgO+CaO+SrO+BaO, and has a molar ratio SiO.sub.2/B.sub.2O.sub.3 of 14 or more.

Claims

1. A glass for sealing, comprising as a glass composition, in terms of mol %, 60% to 80% of SiO.sub.2, 2% to 5.8% of B.sub.2O.sub.3, 12% to 18.7% of Li.sub.2O+Na.sub.2O+K.sub.2O, and 2% to 12% of MgO+CaO+SrO+BaO, and 0.1% to 2% of F, and having a molar ratio SiO.sub.2/B.sub.2O.sub.3 of 14 or more.

2. The glass for sealing according to claim 1, wherein the glass for sealing has a content of MgO+CaO+SrO+BaO of from 4 mol % to 10 mol %.

3. The glass for sealing according to claim 1, wherein the glass for sealing has a content of Li.sub.2O+Na.sub.2O+K.sub.2O of 18 mol % or less and has a molar ratio CaO/(MgO+CaO+SrO+BaO) of 0.2 or more.

4. The glass for sealing according to claim 1, wherein the glass for sealing has a content of Li.sub.2O+Na.sub.2O+K.sub.2O+MgO+CaO+SrO+BaO of 25 mol % or less.

5. The glass for sealing according to claim 1, wherein the glass for sealing has a granular form.

6. The glass for sealing according to claim 1, wherein the glass for sealing comprises a sintered compact, wherein the sintered compact is formed by heating a green compact, and wherein the green compact is produced by tablet molding granules.

7. The glass for sealing according to claim 1, wherein the glass for sealing is used for sealing a hermetic terminal.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1A is a conceptual diagram for illustrating a hermetic terminal.

(2) FIG. 1B is a conceptual diagram for illustrating a state of a metal stem, a metal pin, and a glass for sealing before firing.

(3) FIG. 1C is a conceptual diagram for illustrating a state of the metal stem, the metal pin, and the glass for sealing after the firing.

(4) FIG. 2 is a graph for showing data in which the thermal expansion curve of Sample No. 1 in the Examples section, the thermal expansion curve of a metal stem, and the thermal expansion curve of a metal pin are superimposed on one another with a bonding temperature as a starting point.

(5) FIG. 3 is a graph for showing data in which the thermal expansion curve of Sample No. 2 in the Examples section, the thermal expansion curve of the metal stem, and the thermal expansion curve of the metal pin are superimposed on one another with a bonding temperature as a starting point.

(6) FIG. 4 is a graph for showing data in which the thermal expansion curve of Sample No. 3 in the Examples section, the thermal expansion curve of the metal stem, and the thermal expansion curve of the metal pin are superimposed on one another with a bonding temperature as a starting point.

(7) FIG. 5 is a graph for showing data in which the thermal expansion curve of Sample No. 4 in the Examples section, the thermal expansion curve of the metal stem, and the thermal expansion curve of the metal pin are superimposed on one another with a bonding temperature as a starting point.

(8) FIG. 6 is a graph for showing data in which the thermal expansion curve of Sample No. 5 in the Examples section, the thermal expansion curve of the metal stem, and the thermal expansion curve of the metal pin are superimposed on one another with a bonding temperature as a starting point.

DESCRIPTION OF EMBODIMENTS

(9) A glass for sealing of the present invention comprises as a glass composition, in terms of mol %, 60% to 80% of SiO.sub.2, 0% to 5.8% of B.sub.2O.sub.3, 12% to 18.7% of Li.sub.2O+Na.sub.2O+K.sub.2O, and 2% to 12% of MgO+CaO+SrO+BaO, and has a molar ratio SiO.sub.2/B.sub.2O.sub.3 of 14 or more. The reasons why the contents of the components are limited as described above are described below. In the description of the contents of the components, the expression % means mol %.

(10) SiO.sub.2 is a main component for forming a glass skeleton, and the content of SiO.sub.2 is from 60% to 80%, preferably from 65% to 75%, more preferably from 68% to 72%. When the content of SiO.sub.2 is too small, there is a risk in that, the thermal expansion coefficient is increased improperly. In addition, water resistance is liable to be reduced. Meanwhile, when the content of SiO.sub.2 is too large, a bonding temperature is liable to be increased.

(11) B.sub.2O.sub.3 is a component which increases meltability and reduces the bonding temperature, and is also a component which increases the water resistance. However, B.sub.2O.sub.3 is a component which encourages abnormal shrinkage at a temperature around a glass transition point during cooling. The content of B.sub.2O.sub.3 is from 0% to 5.8%, preferably more than 0% to 5.3%, more preferably from 1% to 4.8%, particularly preferably from 2% to 3.5%. When the content of B.sub.2O.sub.3 is too small, the bonding temperature is liable to be increased, and the water resistance is liable to be reduced. When, the water resistance is reduced, glass powder is liable to be affected by water in a granulation step, and bubbles are liable to be generated through firing of granules. Meanwhile, when the content of B.sub.2O.sub.3 is too large, a thermal expansion curve has a large inflection at a temperature around the glass transition point, abnormal shrinkage occurs in the glass during cooling, and the glass is liable to be temporarily subjected to a large tensile stress from a metal stem.

(12) The molar ratio SiO.sub.2/B.sub.2O.sub.3 is 14 or more, preferably 17 or more, more preferably 20 or more, still more preferably from 23 to 250. When the molar ratio SiO.sub.2/B.sub.2O.sub.3 is too small, the thermal expansion curve has a large inflection at a temperature around the glass transition point, abnormal shrinkage occurs in the glass during the cooling, and the glass is liable to be temporarily subjected to a large tensile stress from the metal stem. Meanwhile, when the molar ratio SiO.sub.2/B.sub.2O.sub.3 is too large, a viscosity at high temperature is increased, and fluidity is liable to be insufficient in a sealing step. In addition, the water resistance is liable to be reduced.

(13) An alkali metal oxide (Li.sub.2O, Na.sub.2, and K.sub.2O) is a component which increases the meltability and reduces the bonding temperature, but is a component which encourages abnormal shrinkage at a temperature around the glass transition point during the cooling. The alkali metal oxide is also a component which reduces the water resistance. The content of Li.sub.2O+Na.sub.2+K.sub.2O is from 12% to 18.7%, preferably from 12.5% to 18%, more preferably from 13% to 17%, still more preferably from 14% to 16%. The content of Li.sub.2O is preferably from 0% to 10%, more preferably from 1% to 7%, still more preferably from 2% to 6%, particularly preferably from 2.5% to 4%. The content of Na.sub.2O is preferably from 1% to 15%, more preferably from 2% to 12%, still more preferably from 3% to 10%, particularly preferably from 4% to 7%. The content of K.sub.2O is preferably from 1% to 15%, more preferably from 2% to 12%, still more preferably from 3% to 10%, particularly preferably from 4% to 7%. When the content of the alkali metal oxide is too small, the bonding temperature is increased, and hence a residual stress generated after the cooling is increased, with the result that the probability of a hermetic leakage is liable to be increased. Meanwhile, when the content of the alkali metal oxide is too large, abnormal shrinkage occurs in the glass during the cooling, and the glass is liable to be temporarily subjected to a large tensile stress from the metal stem. In addition, the water resistance is liable to be reduced.

(14) An alkaline earth metal oxide (MgO, CaO, SrO, and BaO) is a component which reduces the bonding temperature. The content of MgO+CaO+SrO+BaO is from 2% to 12%, preferably from 41 to 11%, more preferably from 5% to 9%, particularly preferably from 6% to 8%. The content of MgO is preferably from 0% to 5%, more preferably from 0% to 3%, still more preferably from 0% to 1%. The content of CaO is preferably from 0% to 10%, more preferably from 1% to 8%, still more preferably from 3% to 7%. The content of SrO is preferably from 0% to 5%, more preferably from 0% to 3%, still more preferably from 0% to 1%. The content of BaO is preferably from 0% to 7%, more preferably from 1% to 5%, still more preferably from 2% to 4%. When the content of the alkaline earth metal oxide is too small, the bonding temperature is increased, and hence a residual stress generated after the cooling is increased, with the result that the probability of the hermetic leakage is liable to be increased. Meanwhile, when the content of the alkaline earth metal oxide is too large, the thermal expansion curve has a large inflection at a temperature around the glass transition point, abnormal shrinkage occurs in the glass during the cooling, and the glass is liable to be temporarily subjected to a large tensile stress from the metal stem.

(15) The molar ratio CaO/(MgO+CaO+SrO+BaO) is preferably restricted to 0.2 or more (desirably 0.3 or more, particularly desirably 0.4 or more) while the content of Li.sub.2O+Na.sub.2O+K.sub.2O is restricted to 18% or less. When the content of Li.sub.2O+Na.sub.2O+K.sub.2O is too large, the water resistance is reduced, and bubbles are liable to be generated through the firing of the granules. In addition, when the molar ratio CaO/(MgO+CaO+SrO+BaO) is too small, the water resistance is reduced, and bubbles are liable to be generated through the firing of the granules. Out of the alkaline earth metal oxides, CaO has a high effect of increasing the water resistance.

(16) The content of Li.sub.2O+Na.sub.2O+K.sub.2O+MgO+CaO+SrO+BaO is preferably 25% or less or 24% or less, particularly preferably 23% or less. When the content of Li.sub.2O+Na.sub.2O+K.sub.2O+MgO+CaO+SrO+BaO is too large, the thermal expansion curve has a large inflection at a temperature around the glass transition point, abnormal shrinkage occurs in the glass during the cooling, and the glass is liable to be temporarily subjected to a large tensile stress from the metal stem.

(17) Other than the above-mentioned components, for example, the following components may be introduced.

(18) Al.sub.2O.sub.3 is a component which increases the water resistance. The content of Al.sub.2O.sub.3 is preferably from 0% to 8%, more preferably from 1% to 6%, still more preferably from 2% to 4%. When the content of Al.sub.2O.sub.3 is too small, the water resistance is liable to be reduced. Meanwhile, when the content of Al.sub.2O.sub.3 is too large, the bonding temperature is liable to be increased.

(19) TiO.sub.2 and ZrO.sub.2 are each a component which increases the water resistance. The content of each of TiO.sub.2 and ZrO.sub.2 is preferably from 0% to 4%, more preferably from 0% to 2%, still more preferably from 0.1% to 1%. When the contents of TiO.sub.2 and ZrO.sub.2 are too small, the water resistance is liable to be reduced. Meanwhile, when the contents of TiO.sub.2 and ZrO.sub.2 are too large, the bonding temperature is liable to be increased.

(20) F is a component which reduces abnormal shrinkage at a temperature around the glass transition point while reducing the viscosity at high temperature. The content of F is preferably from 0% to 2%, more preferably from 0.1% to 1%. When the content of F is too large, an environmental load is liable to be increased.

(21) Other than the above-mentioned components, for example, Cl.sub.2, La.sub.2O.sub.3, MnO.sub.2, Cr.sub.2O.sub.3, Fe.sub.2O.sub.3, Co.sub.2O.sub.3, and the like may be introduced at respective contents of from 0.1% to 3% unless the effects of the present invention are impaired improperly.

(22) The glass for sealing of the present invention has a thermal expansion coefficient in a temperature range of from 30 C. to 380 C. of preferably from 6010.sup.7/ C., to 13010.sup.7/ C., more preferably from 8010.sup.7/ C. to 11010.sup.7/ C., still more preferably from 8510.sup.7/ C. to 10510.sup.7/ C., particularly preferably from 9010.sup.7/ C. to 10010.sup.7/ C. When the thermal expansion coefficient is too high, after the production of a hermetic terminal, a state in which the glass for sealing is sufficiently compressed by a metal stem is not achieved, and it becomes difficult to maintain sealing strength. Meanwhile, when the thermal expansion coefficient is too low, after the production of the hermetic terminal, a state in which the glass for sealing is excessively pulled by a metal pin is achieved, and cracks are liable to occur in the glass for sealing at an interface with the metal pin. The thermal expansion coefficient refers to an average linear thermal expansion coefficient measured with a push-rod-type thermal expansion coefficient measurement apparatus (TMA) in a temperature range of from 30 C. to 380 C.

(23) In order to subject the glass for sealing to an appropriate compression stress after the production of the hermetic terminal, it is preferred that the shrinkage amount of the glass for sealing be smaller than the shrinkage amount of the metal stem and be larger than the shrinkage amount of the metal pin in a bonding temperature range. That is, the glass for sealing of the present invention has a thermal expansion coefficient in a temperature range of from 30 C. to a bonding temperature of preferably from 10010.sup.7/ C. to 15010.sup.7/ C., more preferably from 12510.sup.7/ C. to 13510.sup.7/ C. The bonding temperature refers to a temperature calculated by the expression Tf(TfTg)/3 when a glass transition point is defined as Tg ( C.) and a deformation point is defined as Tf ( C.) in a thermal expansion curve measured with TMA.

(24) The glass for sealing of the present invention has a bonding temperature of preferably 585 C. or less, more preferably 550 C. or less, still more preferably from 480 C. to 535 C., particularly preferably from 500 C. to 525 C. When the bonding temperature is too high, a residual stress generated after the cooling is increased, with the result that the probability of the hermetic leakage is liable to be increased.

(25) The glass for sealing of the present invention preferably has a granular form. With this, a green compact having a predetermined shape, particularly a green compact having a through-hole for inserting a metal pin can be easily produced through tablet molding.

(26) The glass for sealing of the present invention preferably comprises a sintered compact. With this, when the glass for sealing having inserted therein a metal pin is housed in a metal stem, chipping of the glass for sealing can be suppressed.

(27) The sintered compact has a sealing density of preferably 82% or more, 85% or more, 88% or more, or 92% or more, particularly preferably from 95% to 99%. The sealing density of the sintered compact reflects the ratio of bubbles in the sintered compact. As the sealing density becomes smaller, the ratio of bubbles in the sintered compact becomes larger, and a sealing defect is more liable to occur. Herein, the sealing density refers to a value calculated by the expression {(density of a sintered compact)/(density of a glass bulk without bubbles)}100.

EXAMPLES

(28) Now, the present invention is described by way of Examples. The following Examples are merely illustrative. The present invention is by no means limited to the following Examples.

Examples (Sample Nos. 1 to 3) and Comparative Examples (Sample Nos. 4 to 6) of the Present Invention are Shown in Table 1

(29) TABLE-US-00001 TABLE 1 No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 Glass SiO.sub.2 66.5 77.0 71.5 69.6 63.1 66.7 composition B.sub.2O.sub.3 4.5 0.5 2.5 7.2 5.0 3.8 (mol %) Al.sub.2O.sub.3 2.5 2.5 2.5 1.2 3.4 2.0 Li.sub.2O 4.5 1.0 3.0 4.6 0.0 4.7 Na.sub.2O 8.0 8.0 6.0 7.0 12.6 9.1 K.sub.2O 3.5 5.5 6.0 3.9 3.6 5.0 MgO 0.0 0.0 0.0 0.0 0.0 0.0 CaO 1.5 1.0 5.0 0.0 1.7 2.4 SrO 0.0 0.0 0.0 0.0 2.7 0.1 BaO 6.5 4.0 3.0 4.9 0.2 4.8 TiO.sub.2 1.0 0.0 0.0 0.0 5.5 0.0 ZrO.sub.2 0.5 0.0 0.0 0.6 0.0 0.6 MnO.sub.2 0.0 0.0 0.0 0.0 1.3 0.0 Cr.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.1 0.0 Fe.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.4 0.0 Co.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.4 0.0 F 1.0 0.5 0.5 0.9 0.0 0.7 Li.sub.2O + Na.sub.2O + K.sub.2O 16.0 14.5 15.0 15.6 16.2 18.8 MgO + CaO + SrO + BaO 8.0 5.0 8.0 4.9 4.6 7.4 SiO.sub.2/B.sub.2O.sub.3 14.8 154.0 28.6 9.7 12.6 17.5 Ca/(MgO + CaO + 0.2 0.2 0.6 0.0 0.4 0.3 SrO + BaO) Li.sub.2O + Na.sub.2O + K.sub.2O + 24.0 19.5 23.0 20.5 20.7 26.2 MgO + CaO + SrO + BaO .sub.30-Tset (10.sup.7) 132 126 130 137 143 138 .sub.Tg (10.sup.7/ C.) 12 6 11 16 19 19

(30) First, a glass batch obtained by blending glass raw materials so as to give the glass composition shown in Table 1 was loaded in a platinum crucible, and melted at 1,500 C. for 4 hours. At the time of the melting, the glass batch was stirred with a platinum stirrer to be homogenized. Next, the resultant molten glass was poured on a carbon sheet, formed into a sheet shape, and annealed at a rate of 3 C./min from a temperature higher than an annealing point by about 20 C. to normal temperature. The resultant glass samples were each evaluated for various characteristics.

(31) .sub.30-Tnet is an average linear thermal expansion coefficient measured with TMA in a temperature range of from 30 C. to a bonding temperature. The bonding temperature refers to a temperature calculated by the expression Tf(TfTg)/3 when a glass transition point is defined as Tg ( C.) and a deformation point is defined as Tf ( C.) in a thermal expansion curve measured with TMA.

(32) .sub.Tg is a value obtained by superimposing the thermal expansion curve of a metal stem and the thermal expansion curve of a glass sample on each other with a bonding temperature as a starting point and then evaluating a difference in thermal expansion between the metal stem and the glass sample at the glass transition point (deformation point) of the glass sample. From the viewpoint of preventing cracks from occurring in the glass for sealing owing to a tensile stress, the is preferably 1510.sup.7/ C. or less.

(33) A sealing density is a value calculated by the expression {(density of a sintered compact)/(density of a glass bulk after forming)}100. A larger sealing density means that a sintered compact has less bubbles. The sintered compact is obtained by pulverizing and classifying the glass after forming so as to have an average particle diameter D.sub.50 of from 25 m to 30 m, and then granulating the resultant glass powder, followed by firing at a temperature of (the softening point of the glass powder30 C.) for 10 minutes.

(34) FIG. 2 is a graph for showing data in which the thermal expansion curve of Sample No. 1, the thermal expansion curve of a metal stem, and the thermal expansion curve of a metal pin are super imposed on one another With a bonding temperature as a starting point. FIG. 3 is a graph for showing data in which the thermal expansion curve of Sample No. 2, the thermal expansion curve of the metal stem, and the thermal expansion curve of the metal pin axe superimposed on one another with a bonding temperature as a starting point. FIG. 4 is a graph for showing data in which the thermal expansion curve of Sample No. 3, the thermal expansion curve of the metal stem, and the thermal expansion curve of the metal pin are superimposed on one another with a bonding temperature as a starting point. FIG. 5 is a graph for showing data in which the thermal expansion curve of Sample No. 4, the thermal expansion curve of the metal stem, and the thermal expansion curve of the metal pin are superimposed on one another with a bonding temperature as a starting point. FIG. 6 is a graph for showing data in which the thermal expansion curve of Sample No. 5, the thermal expansion curve of the metal stem, and the thermal expansion curve of the metal pin are superimposed on one another with a bonding temperature as a starting point. In each of FIG. 2 to FIG. 6, solid lines represent the thermal expansion curves of the metal stem (thermal expansion coefficient: 15010.sup.7/ C.) and the metal pin (thermal expansion coefficient: 11010.sup.7/ C.), and a broken line represents the thermal expansion curve of the glass sample.

(35) As is apparent from Table 1 and FIG. 2 to FIG. 6, a difference in thermal expansion between each of Sample Nos. 1 to 3 and the metal stem was small at a temperature around the glass transition point. Meanwhile, a difference in thermal expansion between each of Sample Nos. 4 to 6 and the metal stem was large at a temperature around the glass transition point. Therefore, when a hermetic terminal is produced through use of each of Sample Nos. 4 to 6, it is considered that cracks may occur owing to a temporal tensile stress.

REFERENCE SIGNS LIST

(36) 1 hermetic terminal 11 metal stem 12 metal pin 13 glass for sealing