JP7650245B2 - Low thermal expansion glass for sealing and coating - Google Patents

Description

The present invention relates to a sealing/coating material, more specifically to a sealing/coating glass that can be used for sealing parts when manufacturing articles such as electronic devices, and for coating the surfaces of various parts such as electrodes and resistors of electronic components such as silicon diodes to protect and insulate them, and in particular to such glass that does not contain lead or alkali metal oxides.

Sealing materials used in the manufacture of items such as electronic devices are required to be able to seal the target items at as low a temperature as possible, to have a thermal expansion coefficient that is close to that of those items, and to exhibit sufficient fluidity during firing to ensure reliable sealing.

In addition, the coating materials used on the surfaces of various parts of electronic components also have necessary characteristics, such as (1) a thermal expansion coefficient close to that of the surface to be coated, (2) low alkali metal content, (3) acid resistance because acid is used in the process, and (4) the ability to be fired at relatively low temperatures (especially below 900°C) so that the heat during firing does not adversely affect the electronic components, etc.

The glasses used for sealing or coating the above-mentioned articles are generally of the PbO-- _SiO.sub.2 - _{B.sub.2O.sub.3 system} , and materials whose thermal expansion coefficients have been adjusted by adding low-expansion ceramics such as cordierite in order to lower the thermal expansion coefficients and bring them closer to that of semiconductors have also been used.

However, in recent years, the use of lead-containing glass has come to be avoided from an environmental perspective, and lead-free glass has been developed. Known examples of lead-free glass include ZnO-B ₂ O ₃ -SiO ₂ glass (Patent Document 1) and ZnO-Bi ₂ O ₃ -SiO ₂ glass (Patent Document 2).

However, the lead-free glass developed so far has problems such as a high softening temperature, which requires high firing temperatures, and glass with an increased ZnO content to lower the softening temperature has poor acid resistance.

Patent Publication 2011-153049 WO2018/026402

The object of the present invention is to provide a sealing/coating material which does not contain lead oxide or alkali metal oxide, can be fired at a relatively low temperature of 900°C or less, has excellent acid resistance, and has a thermal expansion coefficient of 40 to 70 x 10 ^-7 /°C, which is a relatively low range for glass.

As a result of extensive research aimed at solving the problems of the prior art described above, the present inventors discovered that glass manufactured by combining a certain range of components in a certain ratio has fluidity at temperatures below 900°C and can be suitably used for sealing and coating objects, has excellent acid resistance, and has a thermal expansion coefficient within the range of approximately 40 to 70×10 ^-7 /°C, and further research based on this finding led to the completion of the present invention.

1. Contains substantially no lead oxide or alkali metal oxide, and contains, in mole percent:
SiO₂ : 30-55%
Al₂O₃: 1-17%
B₂O₃2-28%
ZnO : 0-14%
At least one of MgO and CaO: 5-25% in total
Bi₂O₃: 0-12%
contains,
SiO₂and B₂O₃The total content of is 50 mol% or more,
Glass for sealing and coating, characterized by:
2. Substantially free of lead oxide and alkali metal oxides, in mole percent:
SiO₂ : 31-53%
Al₂O₃: 3-15%
B₂O₃4-24%
ZnO: 1-14%
At least one of MgO and CaO: 5-20% in total
Bi₂O₃: 0 to 11%
contains,
SiO₂and B₂O₃The total content of is 50 mol% or more,
Glass for sealing and coating, characterized by:
3. Substantially free of lead oxide and alkali metal oxides, in mole percent:
SiO₂ : 36-51%
Al₂O₃: 5-15%
B₂O₃6-22%
ZnO: 5-14%
At least one of MgO and CaO: 5-18% in total
Bi₂O₃ : 0.5~11%
contains,
SiO₂and B₂O₃The total content of is 50 mol% or more,
Glass for sealing and coating, characterized by:
4. Any of the sealing and coating glasses 1 to 3 above, containing 5 mol % or more of MgO.
5. Substantially free of lead oxide and alkali metal oxides, in mole percent:
SiO₂ : 33-43%
Al₂O₃: 3-15%
B₂O₃ : 13-28%
ZnO: 0-10% or less
At least one of MgO and CaO: 10-25% in total
Bi₂O₃: 0-5%
contains,
SiO₂and B₂O₃The total content of is 50 mol% or more,
Glass for sealing and coating, characterized by:
6. Substantially free of lead oxide and alkali metal oxides, in mole percent:
SiO₂ : 35-42%
Al₂O₃8-15%
B₂O₃ : 15-22%
ZnO: 3-10%
At least one of MgO and CaO: 15-23% in total
contains,
Bi₂O₃: 0 to less than 1%
SiO₂and B2O₃The total content of is 50 mol% or more,
Glass for sealing and coating, characterized by:
7. MgO, CaO and Bi₂O₃SiO₂Molar ratio of:
[SiO₂/(MgO+CaO+Bi₂O₃) ］
A sealing/coating glass as set forth above in any one of 1 to 6, wherein is 1 to 5.
8. Any one of the sealing/coating glasses 1 to 5 above in powder form.
9. A sealing/coating material comprising the powder of 6 above and a filler powder, wherein the content of the filler powder relative to the total amount of both powders does not exceed 40% by weight.
10. A sealing/coating paste which is the sealing/coating material as set forth in 7 above and contains an organic binder and a solvent.

The sealing/coating material of the present invention having the above-mentioned configuration can be fired at 900°C or less. Furthermore, since the glass powder of the present invention does not react with a ceramic filler when mixed with the filler and fired, crystals are hardly precipitated during firing, and even if they do precipitate, the amount is very small. Therefore, the material has excellent fluidity during firing and can be used as a sealing/coating material with high mechanical strength and excellent durability after cooling and solidifying. Furthermore, the sealing/coating material of the present invention can easily have a thermal expansion coefficient adjusted to within the range of about 40 to 70 x 10 ^-7 /°C. Therefore, the sealing/coating material of the present invention can be used as a material particularly suitable for sealing and coating.

The components constituting the sealing/coating glass of the present invention and their content ranges suitable for achieving the objectives of the present invention are as follows:

SiO ₂ is a component that forms glass, and is preferably contained in the range of 30 to 55 mol %. This is because if the SiO ₂ content is less than 30 mol %, glass may not be obtained, or even if it is obtained, the glass may have a high thermal expansion coefficient that cannot be used for sealing, and if the SiO ₂ content is more than 55 mol %, the glass may be difficult to melt, and in particular, SiO ₂ may remain unmelted as an unmelted material. In consideration of the formability of glass and stable achievement of a desired thermal expansion coefficient and meltability, the SiO ₂ content is more preferably 31 to 53 mol %, and even more preferably 36 to 51 mol %.

Al ₂ O ₃ is a component for forming glass, and is preferably contained in the range of 1 to 17 mol %. This is because if the content of Al ₂ O ₃ is less than 1 mol %, glass may not be obtained, and if the content of Al ₂ O ₃ is more than 17 mol %, it may remain unmelted. In consideration of stable achievement of glass formability and meltability, the content of Al ₂ O ₃ is more preferably 3 to 15 mol %, and further preferably 5 to 15 mol %.

B ₂ O ₃ is a component for forming glass, and is preferably contained in the range of 2 to 28 mol %. This is because if the content of B ₂ O ₃ is less than 2 mol %, glass may not be obtained, or even if it is obtained, the glass may have a high softening temperature that cannot be used for sealing, and if the content of B ₂ O ₃ is more than 28 mol %, the glass may have a high thermal expansion coefficient that cannot be used for sealing or coating. In consideration of the formability of glass and stable achievement of a desired softening temperature and thermal expansion coefficient, the content of B ₂ O ₃ is more preferably 4 to 24 mol %, and even more preferably 6 to 22 mol %.

The total content _{of SiO2} and _B2O3 in the sealing and coating glass of the present invention is preferably 50 mol% or more. If the total content of _SiO2 and _B2O3 is less than 50 mol%, there is a risk that glass cannot be obtained. In consideration of stable achievement of glass formability, _the total content _{of SiO2} and _B2O3 is more preferably 55 mol% or more, and further preferably 57 mol% or more.

ZnO is not an essential component, but since it acts to enhance the formability of glass, it is preferable to include it, and in that case, the content is preferably 14 mol% or less. If the ZnO content is more than 14 mol%, there is a risk of producing a glass with poor acid resistance. In consideration of the formability of the obtained glass and stable achievement of acid resistance, the ZnO content is more preferably 1 to 14 mol%, and even more preferably 5 to 14 mol%. However, without being limited to these ranges, the ZnO content may be, for example, less than 10 mol%, or 9.5 mol% or less, 9 mol% or less, that is, 0 to less than 10 mol%, 0 to 9.5 mol%, 0 to 9 mol%, etc. In addition, the lower limit of these ranges may be 1 mol%, 3 mol%, etc. instead of 0 mol%, as described above.

MgO and CaO are components that enhance the formability of glass, and it is preferable to include at least one of them in a total range of 5 to 25 mol%. This is because if the total amount of MgO and CaO is less than 5 mol%, the glass may have a high softening temperature that is not suitable for sealing in the desired temperature range of the present invention, and if the total content is more than 25 mol%, glass may not be obtained. In consideration of stable achievement of glass formability and fluidity, the total content of MgO and CaO is more preferably 5 to 20 mol%, and even more preferably 5 to 18 mol%. Of MgO and CaO, MgO in particular acts to lower the thermal expansion coefficient while maintaining the formability of glass, so it is preferable to include at least 5 mol%. In consideration of lowering the thermal expansion coefficient of the obtained glass, it is more preferable to include only MgO in any of the above ranges without using CaO in combination.

Bi ₂ O ₃ is a component that stabilizes the glass state and lowers the softening temperature of the glass. Although it is not an essential component, it is preferable to include it, and in that case, the content is preferably 12 mol% or less. This is because if the content of Bi ₂ O ₃ exceeds 12 mol%, the formability of the glass decreases or crystals are easily precipitated during firing, which may cause sealing and coating defects. In consideration of the formability of the obtained glass and the securing of sealing and coating performance, the content of Bi ₂ O ₃ is more preferably greater than 0 to 11 mol%, and even more preferably 0.5 to 11 mol%. However, without being limited to these ranges, the content of Bi ₂ O ₃ may be, for example, less than 5 mol%, or 3 mol% or less, or 1 mol% or less, that is, it may be in a range such as 0 to less than 10 mol%, 0 to less than 3 mol%, or 0 to less than 1 mol%. In addition, the lower limit of these ranges may be 0.5 mol% instead of 0 mol%, as described above.

_ZrO2 is not an essential component, but since it acts to improve the acid resistance of the glass, it is preferable to include it, and in that case, the content is preferably 7 mol% or less. This is because if the _ZrO2 content exceeds 7 mol%, the glass formability may deteriorate or crystals may easily precipitate during firing, which may cause sealing and coating defects. In consideration of the formability of the obtained glass and the securing of sealing and coating performance, the _ZrO2 content is preferably 0.1 to 5 mol _% , more preferably 1 to 5 mol%.

In the sealing and coating glass of the present invention, the ratio of the _SiO2 content (mol%) to the total content (mol%) _of MgO, CaO, and _Bi2O3 [ _SiO2 /(MgO+ _CaO + _Bi2O3 )] is preferably 1 to 5. If this ratio is less than 1, the acid resistance of the resulting glass may be reduced, and if this ratio exceeds 5, the softening temperature may be so high that an excessively high temperature is required for firing. In consideration of ensuring acid resistance and an appropriate softening temperature, the ratio [ _SiO2 /(MgO+CaO+ _Bi2O3 )] is more preferably 2 to ₄ .

In addition to the above components, _La2O3 , _Nb2O5 , _TeO2 , _CeO2 , _TiO2 , _etc. may be added _in a total amount of up to 5 mol % for the purposes of improving the stability of the glass during production, suppressing crystallization, and adjusting the thermal expansion coefficient.

The sealing/coating glass of the present invention is preferably fired at 900°C or less so that the heat during firing does not adversely affect electronic components, etc., and therefore, as a rough guideline, its softening point is preferably in the range of approximately 600°C to 750°C, and more preferably in the range of approximately 650°C to 730°C.

(2) Ceramic filler: The powder made of the glass of the present invention can be mixed with a ceramic filler as necessary for the purpose of adjusting the thermal expansion coefficient and improving the strength when used as a sealing/coating material. The amount of ceramic filler mixed can be appropriately set to 40% by weight or less of the total amount with the glass. Examples of ceramic fillers to be mixed include cordierite, zircon, zirconium phosphate, aluminum titanate, mullite, alumina, willemite, and silica (α-quartz, cristobalite, and tridymite).

The sealing/coating glass of the present invention can be used as a sealing/coating material in the form of a powder or in the form of a mixed powder of the glass with a ceramic powder. It can also be used as a sealing/coating material in a form that is more convenient for application to the surface of the object to be sealed/coated, such as a paste or sheet obtained by further mixing a binder or a solvent with the powder.

To make a powder of the sealing/coating glass of the present invention or a mixed powder of the same and a ceramic filler into a paste, the powder may be mixed with at least one of a solvent and an organic binder. For example, a paste can be prepared by mixing a powder of the glass of the present invention in powder form, a solvent, and an organic binder. When preparing the paste, the average particle size of the sealing/coating glass in powder form is not particularly limited, but is usually preferably 1 to 10 μm, and more preferably 2 to 8 μm.

There is no particular restriction on what kind of organic binder is used, and any known binder may be appropriately selected depending on the specific application of the sealing/coating material. Examples include, but are not limited to, cellulose resins such as ethyl cellulose.

The solvent may be appropriately selected depending on the organic binder used, and examples thereof include, but are not limited to, alcohols such as ethanol, methanol, isopropanol, and organic solvents such as terpineol (α-terpineol, or a mixture of α-terpineol as the main component with β-terpineol and γ-terpineol). The solvents may be used alone or in combination of two or more.

In preparing the paste, in addition to the above, known additives such as plasticizers, thickeners, sensitizers, surfactants, dispersants, etc. may be appropriately blended as necessary.

To manufacture a sealing/coating material in sheet form, for example, additives such as a solvent and an organic binder are appropriately selected and added to and mixed with the sealing/coating glass powder of the present invention or a mixed powder with a ceramic filler, the mixture is applied to a substrate, and the coating film is dried at room temperature or under heat.

The present invention will now be described in more detail with reference to the following examples, but it is not intended that the present invention be limited to these examples.

[Production of Glass and Glass Powder]
Raw materials were prepared and mixed to obtain the glass compositions (component contents are expressed in mol%) shown in Examples 1 to 49 in Tables 1 to 7 and Comparative Examples 1 to 4 in Table 8. The mixture was placed in a platinum crucible and melted at a temperature of 1400 to 1500°C for 1 hour, and then quenched by a twin-roll method to obtain glass flakes, and a part of the molten glass was poured onto a preheated carbon plate to produce a glass block. The obtained glass flakes were pulverized using a pot mill to obtain glass powder. The glass block was then slowly cooled in an electric furnace set at a temperature about 50°C higher than the glass transition temperature measured for the glass powder using a DTA measuring device as described below.

[Preparation of mixed powder of glass and filler]
The glass powders of four examples randomly selected from the above examples were mixed with ceramic filler powder in the amounts shown in Table 10 for Examples 50 to 53 to prepare mixed powders.

[Evaluation 1]
For each of the glasses of Examples 1 to 49 and Comparative Examples 1 to 4, the glass transition temperature, softening temperature, and crystallization temperature were measured using glass powder, and the thermal expansion coefficient was measured using a glass block, by the following methods. The results are shown in Tables 1 to 8.

(1) Glass transition temperature, softening temperature, and crystallization temperature Approximately 60 to 80 mg of glass powder was filled into a platinum cell, and the glass transition temperature (Tg), softening temperature (Ts), and crystallization temperature (Tp) were measured by raising the temperature from room temperature at 20° C./min using a DTA measurement device (Rigaku Thermo Plus EVO2 TG-DTA8122).

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

[Evaluation 2]
Acid resistance The acid resistance of each of the glasses of Examples 31 and 32 and Comparative Examples 1 to 4 was measured by the following method. That is, the above glass blocks were cut into approximately 5 x 5 x 15 mm, immersed in 70% nitric acid, and left to stand at room temperature for 2 hours. The ratio (%) of the weight change of the glass block after immersion to the weight before immersion was calculated. The results are shown in Table 9.

[Evaluation 3]
Fluidity (baked at 900°C)
The fluidity of each of the glasses of Examples 31 and 32 and Comparative Examples 1 to 4 was examined when fired at 900°C by the following method. That is, about 5 g of each glass powder was placed in a mold having an inner diameter of 20 mm, and pressed into a green compact, which was then heated to 900°C at a heating rate of 200°C/hour and held at that temperature for 1 hour, after which the fired state was observed. The results are shown in Table 9. Glasses that had a glassy luster on the surface and flowed were marked with an ◯, and glasses that did not have a glassy luster on the surface and had no fluidity were marked with an X.

[Evaluation 4]
Thermal expansion coefficient of compact of mixed powders In Examples 50 to 53, about 5 g of the mixed powder was placed in a mold with an inner diameter of 20 mm and pressed to form a compact. Each compact was sintered at 900°C for 1 hour, and the resulting sintered body was cut into a size of about 5 x 5 x 15 mm to prepare a test specimen. For the test specimen, the thermal expansion coefficient (α) was determined based on two points, 50°C and 300°C, from the thermal expansion curve obtained when the temperature was raised from room temperature at a rate of 10°C/min using a TMA measuring device. The results are shown in Table 10.

As can be seen from the above table, the glasses of Examples 1 to 49 have softening temperatures in the range of 615°C to 767°C, and therefore can be fired in a state of sufficient fluidity at temperatures not exceeding 900°C. The glasses of Examples 1 and 39, which have crystallization temperatures below 900°C, have a sufficiently large difference between the softening temperature and the crystallization temperature (the differences are 185°C and 246°C, respectively), and can be fired at temperatures that do not cause crystallization. In the glasses of the remaining Examples, no crystallization is detected or the crystallization temperatures exceed 900°C, and therefore there is no risk of crystallization occurring during firing at temperatures below 900°C. The glasses of all Examples also exhibit an expansion coefficient within the range of 40 to 70 x 10 ^-7 /°C, which is preferred in the present invention. Furthermore, the glasses of Comparative Examples 1 and 2, which have low _SiO2 contents (15.3 and 25.0 mol%, respectively), show significant weight loss in the acid resistance test, whereas the glasses of the present invention have excellent acid resistance, as seen in Examples 31 and 32. The glass of Comparative Example 2 is also not suitable for the purpose of the present invention because of its large thermal expansion coefficient of 71 x ^10-7 /°C. The glass of Comparative Example 3 has a fairly low crystallization temperature (777°C) and a small difference between the softening temperature and the crystallization temperature (the difference is 167°C), making it difficult to control the temperature so as to perform firing while suppressing substantial crystallization, which causes a decrease in fluidity, and the glass of Comparative Example 4 has a very narrow difference between the softening temperature and the crystallization temperature (the difference is 118°C), making it even more difficult to suppress crystallization during firing.

The glasses of Examples 54 to 69 were manufactured in the same manner as Examples 1 to 53 so as to have the glass compositions shown in Tables 11 to 13. Powders and glass blocks were prepared for each, and the glass transition temperature, softening temperature, crystallization temperature, and thermal expansion coefficient were measured (some were not measured). The results are shown in Tables 11 to 13.

As can be seen in Tables 11 to 13, the glasses of Examples 54 to 69 showed results equivalent to those of Examples 1 to 49.

As such, the glass of the present invention is suitable for sealing items such as semiconductors in terms of its softening temperature and thermal expansion coefficient, and can also be provided with excellent acid resistance, making it suitable for use in sealing and bonding a wide variety of electronic devices and various parts of electronic components.

The glass of the present invention can be used in the form of powder, either alone or as a mixed powder with ceramic filler powder, as a sealing and coating material with excellent fluidity at temperatures below 900°C for sealing and coating electronic devices and other articles. In addition, there is no risk of reaction between the filler and the glass, the thermal expansion coefficient is close to that of the semiconductors used in articles such as electronic devices, so problems with thermal stress are unlikely to occur, the mechanical strength and durability of the sealing and coating parts are high, and it can also be provided with excellent acid resistance, so it can be advantageously used as a sealing and coating material for such articles.

Claims (10)

Substantially free of lead oxide or alkali metal oxides, in mole percent,
SiO₂ : 30-55%
Al₂O₃:3~17%
B₂O₃2-28%
ZnO : 1-14%
At least one of MgO and CaO: 15-25% in total
Bi₂O₃: 0-12%
contains,
SiO₂and B₂O₃The total content of is 50 mol% or more,
Glass for sealing and coating, characterized by: Substantially free of lead oxide and alkali metal oxides, in mole percent:
_SiO2 : 31-53%
_Al2O3 : _3-15 %
_{B2O3 :} 4-24%
ZnO: 1-14%
At least one of MgO and CaO: 15 to 20% in total
_Bi2O3 : ₀ to 11%
Contains
The total content of _SiO2 and _B2O3 is 50 mol% or more _;
A sealing and coating glass characterized by the above. Substantially free of lead oxide and alkali metal oxides, in mole percent:
_SiO2 : 36-51%
_Al2O3 : _5-15 %
_{B2O3 :} 6-22%
ZnO: 5-14%
At least one of MgO and CaO: 15 to 18% in total
_{Bi2O3 :} 0.5-11%
Contains
The total content of _SiO2 and _B2O3 is 50 mol% or more _;
A sealing and coating glass characterized by the above. A sealing/coating glass according to any one of claims 1 to 3, containing 5 mol% or more of MgO. Substantially free of lead oxide and alkali metal oxides, in mole percent:
_SiO2 : 33-43%
_Al2O3 : _3-15 %
_{B2O3 :} 13-28%
ZnO: 1 to less than 10% At least one of MgO and CaO: 15 to 25% in total
_{Bi2O3 :} 0-5%
Contains
The total content of _SiO2 and _B2O3 is 50 mol% or more _;
A sealing and coating glass characterized by the above. Substantially free of lead oxide and alkali metal oxides, in mole percent:
_SiO2 : 35-42%
_Al2O3 : _8-15 %
_{B2O3 :} 15-22%
ZnO: 3 to less than 10% At least one of MgO and CaO: 15 to 23% in total
Contains
Bi ₂ O ₃ : 0 to less than 1% The total content of SiO ₂ and B ₂ O ₃ is 50 mol% or more;
A sealing and coating glass characterized by the above. Molar ratio of _SiO2 to the _sum of MgO, CaO and _Bi2O3 :
[SiO ₂ /(MgO+CaO+Bi ₂ O ₃ )]
The sealing/coating glass according to any one of claims 1 to 4, wherein is 1 to 6. A sealing/coating glass according to any one of claims 1 to 7, in the form of a powder. A sealing/coating material comprising the powder of claim 8 and a filler powder, wherein the content of the filler powder relative to the total amount of both powders does not exceed 40% by weight. 10. The sealing/coating paste according to claim 9, comprising an organic binder and a solvent.