JP2024091551A - Sealing materials - Google Patents

Abstract

The present invention provides a glass composition which is substantially free of lead oxide and can be used as a sealing material while maintaining its glassy state at a firing temperature of 400° C. or less.
[Solution] A sealing glass composition which does not contain lead oxide and contains, in mole percent terms of oxide, TeO ₂ : 63-82%, ZnO+CuO: 5-25%, Bi ₂ O ₃ : 0.1-9%, and RO (R is one or more of Mg, Ca, Sr, and Ba): 1-15%.
[Selection diagram] None

Description

The present invention relates to a sealing material, and more specifically, to a sealing material used for sealing electronic devices such as IC packages, bonding metals such as stainless steel together, or for protecting and insulating electrodes and resistors formed on electronic components, which is substantially lead-free and can be used at low temperatures.

Sealing materials used to seal IC packages are required to be able to seal at as low a temperature as possible, to have sufficient fluidity when fired for sealing, and to have a thermal expansion coefficient close to that of the packaging material. Sealing materials used to protect electrodes and resistors and for insulating coatings are also required to be able to be fired at low temperatures.

Generally, PbO- _B2O3 or PbO- _{B2O3 - Bi2O3} glass is used as a sealing material that can be used for sealing or coating at _low temperatures _. In order to match the thermal expansion coefficient of the target object such as the packaging material, it has been proposed to add a low expansion ceramic such as lead titanate solid solution filler to this.

However, in recent years, the use of lead-containing glass has come to be avoided for environmental reasons, and there has been active development of lead-free glass.

Known examples of lead-free low-melting glass include phosphate glass, alkali silicate glass, and bismuth-based glass. Among these, bismuth-based glass has attracted attention due to its ability to be fired at low temperatures and its chemical durability, and many types of bismuth-based glass have been developed.

However, many of the bismuth-based glasses developed so far have high softening points, and their performance is insufficient for use as sealing materials. On the other hand, bismuth-based glasses with low softening points have the drawback of being prone to crystallization during firing. If crystallization occurs during the sealing process, fluidity is lost, resulting in poor sealing. In addition, the amount of filler added is limited because it can also induce crystallization depending on the amount added. For this reason, in glasses that contain bismuth and have a low softening point, it is difficult to mix filler in the ratio required to adjust the thermal expansion coefficient of the sealing material. For example, there was also the problem that it was not possible to mix enough filler to lower the thermal expansion coefficient of the sealing material so that it would be compatible with an object with a low thermal expansion coefficient.

As a low-melting glass, Patent Document 1 discloses a tellurium oxide-based glass composition that contains a large amount of bismuth oxide and tungsten oxide.

Patent Document 2 also discloses a tellurium oxide-based glass composition containing large amounts of bismuth oxide and boron oxide, which is used as a sealing material.

JP 2019-031403 A Patent No. 6357937

The tellurium oxide glass composition disclosed in Patent Document 1 has a high alkali metal content, which causes the glass to have low water resistance.

In addition, the glass composition disclosed in the above-mentioned Patent Document 2 has a high boron content, and either has a softening point that is too high or lacks glass stability, and therefore cannot be made to flow even when fired at 400°C. Furthermore, depending on the specific composition selected, the composition disclosed in the same document can become a non-crystalline glass or a crystallized glass, and there is also the problem that the glass lacks stability in its form.

The objective of the present invention is to provide a glass composition that has excellent fluidity when fired, particularly when fired at low temperatures of 400°C or less, can maintain its glassy state when fired at such low temperatures, and is free of lead.

Another objective of the present invention is to provide a glass composition that has the above characteristics and also has improved water resistance.

An additional objective of the present invention is to provide a glass composition that has the above characteristics and also has improved acid resistance.

The present inventors have conducted research to solve the above problems. As a result, they have found a glass composition that exhibits excellent fluidity at a low firing temperature of 400°C or less, and has the property of being able to be used as a sealing material while maintaining its original glass state (amorphous) without crystallizing during the firing process at such temperatures. They have also found a glass composition that has these properties while also having high acid resistance and high water resistance. That is, the present invention provides the following glass composition and a sealing material containing the same.

1. Substantially free of lead oxide;
In terms of oxide, mole percent is:
_TeO2 : 63-82%
ZnO+CuO: 5-25%
Bi ₂ O ₃ : 0.1 to 9%, and RO (R is one or more of Mg, Ca, Sr, and Ba): 1 to 15%.
Characterized in that it comprises
Sealing glass composition.
2. The sealing glass composition according to the above item 1,
In terms of oxide, mole percent is:
_TeO2 : 65-80%
ZnO+CuO: 8-20%
_Bi2O3 : _4-7 %
RO (R is one or more of Mg, Ca, Sr, and Ba): 2 to 12%
A sealing glass composition comprising:
3. The sealing glass composition according to the above item 1, wherein the ZnO content is 5 to 25% and the BaO content is 1 to 15%.
4. The sealing glass composition according to claim 1, wherein the content of B ₂ O ₃ is 0 to 3%.
_5. The above 1, wherein the molar ratio of _TeO2 to _Bi2O3 ( _TeO2 / _Bi2O3 ) is 8 to ₁₆ .
The sealing glass composition according to claim 1.
6. The sealing glass composition according to the above item 1, wherein the content of WO ₃ +MoO ₃ +Nb ₂ O ₅ is 1 to 12%, and the content of Nb ₂ O ₅ is 4% or less.
7. A sealing material comprising a glass powder made of the sealing glass composition according to any one of 1 to 6 above and a filler powder.

The present invention provides a glass composition that is substantially free of lead oxide and has the performance of exhibiting excellent fluidity without crystallization that inhibits fluidity even when subjected to a firing process at a low temperature, particularly a low temperature of 400°C or less, making it possible to provide a sealing material suitable for sealing, bonding, and covering objects while maintaining the original amorphous glass state. Furthermore, the present invention also makes it possible to provide a glass composition that has the above performance, particularly a glass composition with enhanced acid resistance and water resistance, as well as a sealing material that contains the glass composition.

The content of each component and the reasons for limiting the range of the sealing glass composition according to the embodiment of the present invention are explained below. Note that the content of each component is expressed in mol% below.

_TeO2 is an oxide that forms glass, and can be contained in the glass composition of the present invention as an essential component in the range of 63 to 82%. If the content of _TeO2 is less than 63%, glass may not be formed, and even if glass is obtained, it may be a glass with a high softening point, and may not be usable for purposes such as sealing at a desired temperature (400 ° C or less). If the content of _TeO2 exceeds 82%, crystallization may occur during sealing, resulting in low fluidity. Considering factors such as formability, sealing temperature, and fluidity during sealing of the glass composition of the present invention, the content of _TeO2 is more preferably 65 to 80%, and even more preferably 70 to 80%.

ZnO and CuO are components that enhance the formability of glass, and one or both of them can be included in the glass composition of the present invention in a total amount of 5 to 25% as essential components. If the total amount of ZnO and CuO is less than 5%, the glass may crystallize and become non-flowable when sealed at 400°C or less. However, if the total amount exceeds 25%, glass may not be formed. Considering factors such as the formability, stability of the glass state, and fluidity of the glass composition of the present invention, it is more preferable to include one or both of ZnO and CuO in a total amount of 8 to 20%, and even more preferable to include 4 to 10%.

In addition, compared to ZnO and CuO, ZnO acts more favorably as a component that enhances glass formability and fluidity. For this reason, it is even more preferable to include only ZnO within the above total content range.

Bi ₂ O ₃ is an ingredient that is effective in stabilizing the glass state and lowering the softening point of the glass, and can be contained in the glass composition of the present invention as an essential ingredient in the range of 0.1 to 9%. If Bi ₂ O ₃ is less than 0.1%, the glass will have a high softening point and will have low fluidity when sealed at 400°C or less. If Bi ₂ O ₃ is more than 9%, the glass state will become unstable, crystals will easily precipitate during firing, and if crystals precipitate, the fluidity will decrease. Considering factors such as formability, stability, and softening point of the glass composition of the present invention, the content of Bi ₂ O ₃ is more preferably 3 to 8%, and even more preferably 4 to 7%.

MgO, CaO, SrO, and BaO are components that act to enhance the formability and stability of glass, and at least one of them can be contained as an essential component in the glass composition of the present invention in a total amount of 1 to 15%. If the total content of MgO, CaO, SrO, and BaO is less than 1%, the glass composition of the present invention may crystallize and not flow when sealed at 400°C or less. If the total content exceeds 15%, there is a risk that glass may not be formed. Considering factors such as the formability and fluidity of the glass composition of the present invention, it is more preferable to contain one or more of MgO, CaO, SrO, and BaO in a total amount of 2 to 12%, and even more preferable to contain 4 to 10%.

Of MgO, CaO, SrO, and BaO, BaO is particularly preferred as a component that stabilizes the glass. For this reason, it is even more preferred to include only BaO among these four components within the above total content range.

The glass composition of the present invention does not substantially contain PbO. Here, "substantially does not contain" means that raw materials containing any of these as constituents are not used in the manufacture of the glass composition of the present application, and it is acceptable to consider PbO as substantially free if it is contained as an impurity in the raw materials used to manufacture the glass. More specifically, if the content of PbO is 500 ppm or less, it is considered to be an impurity.

_B2O3 can be contained as _an optional component in _{the glass composition of the present invention. Although B2O3 is} an effective component for improving the stability of the glass state, it is also a component for increasing the softening point of the glass. Considering the softening point and fluidity of the glass composition of the present invention, even if _B2O3 is contained _, its content is preferably 3% or less, more preferably 1% or less, and it is further preferable that it is not substantially contained, specifically 0.1% or less.

Li ₂ O, Na ₂ O, and K ₂ O may also be contained as optional components in the glass composition of the present invention. These are components that lower the softening point of the glass, but also components that lower the water resistance of the glass, so even if they are contained, the total content is preferably 1% or less, and it is further preferable that they are not substantially contained, specifically 0.1% or less.

_SiO2 and _Al2O3 may also be included as optional components in the glass composition of the present invention. Although these are components _that form glass, the glass obtained is likely to crystallize if they are included. Therefore, the total content of _SiO2 and _Al2O3 is preferably 1% or less, _and more preferably, they are not substantially included, specifically, 0.1% or less.

Furthermore, V ₂ O ₅ may be contained as an optional component of the glass composition of the present invention. V ₂ O ₅ is a component that forms glass and also lowers the softening point. However, vanadium is a substance that is generally known to have an effect on the human body (vanadium pentoxide is subject to the Industrial Safety and Health Act's Specific Chemical Substance Hazard Prevention Regulations), so from the viewpoint of avoiding concerns about exposure, particularly in the glass manufacturing process, it is preferable to contain 1% or less, more preferably 0.5% or less, and it may not be substantially contained. Regarding V ₂ O ₅ , "substantially not contained" means that raw materials containing this as a constituent component are not used in the manufacture of the glass composition of the present application, and its inclusion is permitted to the extent that it is contained as an impurity in raw materials, etc. for producing glass. More specifically, if the content of V ₂ O ₅ is 500 ppm or less, it is considered to be an impurity.

In the sealing glass composition of the present invention, the molar ratio (TeO ₂ /Bi ₂ O ₃ ) of the content of TeO ₂ to the content of Bi ₂ O ₃ is preferably 8 to 16. If this molar ratio is less than 8, the composition will have an unstable glass state, and crystals may easily precipitate during firing. If this molar ratio exceeds 16, the composition will have a high softening point, and fluidity may decrease. In consideration of factors such as glass formability, stability, and softening point, the molar ratio (TeO ₂ /Bi ₂ O ₃ ) is more preferably 10 to 15.

It is generally known that the lower the temperature exhibiting thermal properties such as the glass transition point and softening point, the lower the chemical stability such as acid resistance and water resistance tends to be. However, as a result of further investigation, it was found that the glass composition of the present invention having the above composition and containing an oxide selected from WO ₃ , MoO ₃ and Nb ₂ O ₅ in a predetermined molar ratio can improve the acid resistance (and therefore improve the water resistance at the same time) while maintaining the above-mentioned preferable thermal properties such as the glass transition point and softening point.

The preferred total content of WO ₃ , MoO ₃ and Nb ₂ O ₅ (WO ₃ +MoO ₃ +Nb ₂ O ₅ ) that meets this purpose is preferably 1 to 12%, more preferably 1 to 11%, and even more preferably 2 to 10%, of which the content of Nb ₂ O ₅ is preferably 4% or less, and more preferably 3% or less.

The glass composition of the present invention containing WO ₃ , MoO ₃ and/or Nb ₂ O ₅ in such a ratio has the above-mentioned preferable temperature characteristics and also has enhanced acid resistance and water resistance, and therefore can be provided as a glass composition and sealing material with expanded possibilities for use in the manufacture of products that are exposed to acid during the manufacturing process, such as plating treatment, or products that are used in acidic environments.

Furthermore, in order to improve the stability of the glass during manufacturing, to prevent crystallization during the firing process at 400°C or less, and in particular to be able to add the filler described below while preventing crystallization to adjust the thermal expansion coefficient, it is preferable that the total content of the above-mentioned essential components is 98% or more.

The glass composition of the present invention is preferably in the form of a powder for convenience during use. There are no particular limitations on the particle size of the glass composition of the present invention in powder form, but taking into account the fluidity during firing, the 50% particle size is preferably 2 to 15 μm, and more preferably 5 to 13 μm.

In the present invention, the "50% particle size" ( _D50 ) is the particle size at which the cumulative amount counted from the small particle size side is 50% of the entire sample in the volume-based particle size distribution, and can be measured using a laser analysis/scattering type particle size distribution analyzer.

A ceramic filler can be added to the glass powder made of the glass composition of the present invention in order to adjust the thermal expansion coefficient when used as a sealing material for an object and to improve the strength of the sealing material after hardening. The amount of ceramic filler added can be appropriately adjusted within a range of 40 parts by mass (40% by mass) or less when the total amount with the glass composition is 100 parts by mass.

Ceramic fillers that can be used include zirconium tungstate phosphate, β-eucryptite, cordierite, zircon, zirconium phosphate, aluminum titanate, mullite, β-spodumene, alumina, celsian, willemite, and silica (α-quartz, cristobalite, tridymite). It is preferable to mainly use zirconium tungstate phosphate as the ceramic filler.

The ceramic filler is usually in the form of a powder, and its 50% particle size is not particularly limited, but is preferably 15 to 25 μm, and more preferably 15 to 20 μm.

The glass composition of the present invention can be used as a sealing material in powder form as it is, but it can also be used as a suspension such as a slurry or paste in which the powdered glass composition is dispersed in an organic binder and/or an organic solvent.

There is no particular restriction on the organic binder that can be used with the glass composition of the present invention, and any known binder can be appropriately selected depending on the specific application of the glass composition of the present invention. Examples include, but are not limited to, cellulose resins such as ethyl cellulose.

There are no particular limitations on the organic solvent that can be used with the glass composition of the present invention, and it can be appropriately selected from known organic solvents depending on, for example, the type and amount of the binder used. Examples include, but are not limited to, alcohols such as methanol, ethanol, isopropanol, and organic solvents such as terpineol (α-terpineol or a mixture of β-terpineol and γ-terpineol with α-terpineol as the main component). These solvents can be used alone or in combination of two or more types.

The features of the present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples.

(Manufacture of glass, glass powder and glass blocks)
As shown in Tables 1 to 3, raw materials were prepared and mixed to obtain the glass compositions of Examples 1 to 13 and Comparative Examples 1 and 2. The resulting mixture was placed in a platinum crucible and melted at a temperature of 800 to 900°C for 1 hour. Next, most of the molten glass was quenched by a twin-roll method to obtain glass flakes, and the remaining portion was poured onto a preheated carbon plate to produce a block. The block was placed in an electric furnace set at a temperature about 50°C higher than the expected glass transition point and slowly cooled. The glass flakes were then placed in a pot mill and pulverized to obtain glass powder.

The 50% particle size of the glass powder was measured using a laser diffraction/scattering type particle size distribution measuring instrument (model name "MT-3000", manufactured by Nikkiso Co., Ltd.) The _D50 of the glass powder of each of the examples and comparative examples is shown in Tables 1 to 3.

For the glass compositions of Examples 1 to 13 and Comparative Examples 1 and 2, the glass transition point, softening point, and crystallization temperature were measured using the glass powder prepared above. The glass powder was also fired to measure the flow diameter, and XRD measurements were performed to check for the presence of crystals. Furthermore, the thermal expansion coefficient was measured using the glass block. The methods used are as follows, and the results are shown in Tables 1 to 3.

(Method of evaluating physical properties)
1. Glass transition point, softening point, crystallization temperature Approximately 60 to 80 mg of glass powder was filled into a platinum cell, and the glass transition point (°C), softening point (°C), and crystallization temperature (°C) were measured by increasing the temperature from room temperature at 20°C/min using a DTA measuring device (ThermoPlusTG8120 manufactured by Rigaku Corporation). Regarding crystallization, the glass powder was fired at a temperature of 400°C for 1 hour, and then the presence of crystals was confirmed by an X-ray diffraction device, and the presence of only the glass phase was judged as ×, and the presence of only the glass phase was judged as ◯.

2. Thermal expansion coefficient α of the glass composition
The glass block obtained above was cut into a size of about 5×5×15 mm and polished to prepare a sample for measuring the thermal expansion coefficient. Using a TMA measuring device, the sample was heated from room temperature at a rate of 10° C./min, and the thermal expansion coefficient (×10 ⁻⁷ /° C.) was calculated based on two points, 50° C. and 300° C., from the thermal expansion curve obtained.

3. Flow button test 8 g of glass powder was dry-pressed into a cylinder of φ20 mm, and fired on a stainless steel substrate for 1 hour at 400° C. The maximum diameter of the resulting fired body was measured as the flow diameter.

4. Water resistance test Approximately 15 g of the glass powder of Example 1 was placed in a thermo-hygrostat chamber at a temperature of 60° C. and a humidity of 90%, and was taken out after 1, 4, 14, and 30 days, and fired at a temperature of 400° C. for 1 hour. After firing, it was confirmed whether the flow button had bubbled. Glass compositions in which the flow button had not bubbled after 30 days in the thermo-hygrostat chamber were judged as ◯ (good), and glass compositions in which the flow button had bubbled were judged as × (bad).

(Preparation of mixture with filler)
A 80:20 (mass/mass) mixed powder of the glass composition powder of Example 1 and ceramic (zirconium tungstate phosphate) powder as a filler was prepared in the ratio shown in Table 4, and used as the sealing material of Example 14. 8 g of this mixed powder was dry-pressed into a cylinder of φ20 mm and sintered on a stainless steel substrate at 400°C for 1 hour. The maximum diameter of the resulting sintered body was measured as the flow diameter. In addition, a block of about 5 x 5 x 15 mm was cut out from the sintered body and polished to prepare a sample for measuring the thermal expansion coefficient. The thermal expansion coefficient (×10 −7 /°C) based on two points, 50°C and 300°C, was obtained from the thermal expansion curve obtained when the sample was heated from room temperature at 10° ^C /min using a TMA measuring device. The results are shown in Table 4.

As is clear from the results in Table 1, the glass compositions of Examples 1 to 13 have softening temperatures below 400°C, and actually exhibit sufficient fluidity even when fired at 400°C. In addition, DTA measurements show that the glass compositions of the Examples have high crystallization temperatures of at least 458°C, and in particular, in the glass compositions of Examples 1 to 9, no crystallization peaks were detected or the crystallization peaks were above 500°C, resulting in glass compositions that do not crystallize when fired at 400°C or below. XRD measurements after firing at 400°C also showed no crystal formation in the glass compositions of Examples 1 to 9. In addition, when the water resistance of the glass composition of Example 1 was tested, no bubbles were observed in the flow button even 30 days after the start of the test, confirming that it has good water resistance.

In contrast, the glass composition of Comparative Example 1 has a softening temperature exceeding 400°C and does not flow even when fired at 400°C. The glass composition of Comparative Example 2 also showed flow when fired at 400°C, but bubbles were already observed in the flow button four days after the start of the water resistance test, confirming its low water resistance.

The sealing material of Example 14, which is a mixture of the glass composition of Example 1, which has a thermal expansion coefficient α (50-300°C) of 172×10 ⁻⁷ /°C, and a filler in a mass ratio of 80:20, exhibited a thermal expansion coefficient of 85×10 ⁻⁷ /°C, and it was confirmed that the thermal expansion coefficient of the sealing material can be significantly adjusted by blending the filler.

(Acid resistance test)
As an additional test, the acid resistance of some of the glass compositions in the above examples was examined.
8 g of each of the glass composition powders of Examples 2 to 4, 7, and 8 was dry-pressed into a cylinder of φ20 mm and fired on a stainless steel substrate at 400°C for 1 hour to produce a flow button. The fired body was cut into a size of 3 x 3 x 10 mm, dried at 100°C for 30 minutes, and then weighed. This was immersed in 1N nitric acid at room temperature for 2 hours, dried at 100°C for 30 minutes, weighed, and the weight loss rate (%) was calculated. The results are shown in Table 5.

Additional Examples: Examples 15 to 27
(Manufacture of glass, glass powder and glass blocks)
The raw materials were prepared and mixed to obtain the glass compositions shown in Tables 6 to 8. From the obtained mixtures, glass flakes were prepared and crushed in a pot mill to obtain glass powder, and the remaining portion was poured onto a preheated carbon plate to prepare a block, in the same manner as in Examples 1 to 13. The block was placed in an electric furnace set at a temperature about 50° C. higher than the expected glass transition point, and slowly cooled.

The 50% particle size, glass transition point, softening point, crystallization temperature, thermal expansion coefficient, and flow diameter of the obtained glass powder were measured in the same manner as in Examples 1 to 13, and the acid resistance was measured in the same manner as in each of the glass compositions of Examples 2 to 4, 7, and 8.
The results are shown in Tables 6 to 8.

As seen in Tables 6 to 8, the glass compositions of Examples 15 to 27 have a softening temperature lower than 400°C, and as shown by the formation of flow buttons when fired at 400°C, they exhibit sufficient fluidity at the same temperature. This shows that no crystallization that inhibits fluidity at 400°C has occurred (for this reason, crystallization has not been confirmed). In addition, compared with the glass compositions of Examples 2 to 4, 7, and 8, the glass compositions of Examples 15 to 27 containing WO ₃ , MoO ₃ , and/or Nb ₂ O ₅ have a significantly lower weight loss rate with 1N nitric acid while maintaining the characteristic of fluidity at 400°C, and it can be confirmed that they are glasses with enhanced acid resistance. This also shows that the glass compositions of these Examples are highly water resistant.

The glass composition for sealing of the present invention is a sealing material that can be fired at a low temperature of 400° C. or less. Even when fired at such a low temperature, the glass composition has excellent fluidity and can spread well over the surface of an object to ensure a tight seal. The glass composition for sealing of the present invention can be used as a sealing material suitable for sealing electronic parts such as IC packages and quartz crystal packages.

Claims (7)

Substantially free of lead oxide
In terms of oxide, mole percent is:
_TeO2 : 63-82%
ZnO+CuO: 5-25%
Bi ₂ O ₃ : 0.1 to 9%, and RO (R is one or more of Mg, Ca, Sr, and Ba): 1 to 15%.
Characterized in that it comprises
Sealing glass composition. The sealing glass composition according to claim 1,
In terms of oxide, mole percent is:
_TeO2 : 65-80%
ZnO+CuO: 8-20%
_Bi2O3 : _4-7 %
RO (R is one or more of Mg, Ca, Sr, and Ba): 2 to 12%
A sealing glass composition comprising: The sealing glass composition according to claim 1, in which the ZnO content is 5 to 25% and the BaO content is 1 to 15%. 2. The sealing glass composition according to claim 1, wherein the content of B ₂ O ₃ is 0-3%. _2. The sealing glass composition according to claim 1, wherein the molar ratio of _TeO2 to _Bi2O3 ( _{TeO2 / Bi2O3} ) is 8-16. 2. The sealing glass composition according to claim 1, wherein the content of WO ₃ +MoO ₃ +Nb ₂ O ₅ is 1 to 12%, and the content of Nb ₂ O ₅ is 4% or less. A sealing material comprising a glass powder made of the glass composition for sealing according to any one of claims 1 to 6 and a filler powder.