JP7148877B2 - ceramic powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to ceramic powders, and more particularly to ceramic powders used in combination with glass powders.

A composite powder material containing glass powder and ceramic powder is generally used as the sealing material. This sealing material is superior in chemical durability and heat resistance to resin-based adhesives, and is suitable for securing airtightness.

As the glass powder for sealing, high-expansion low-melting-point glass such as PbO-based glass and Bi ₂ O ₃ -based glass is used (see Patent Documents 1 and 2, etc.).

Also, the sealing material is used for sealing low-expansion substrates such as alumina substrates and glass substrates. Undue residual strain is generated in the expansion substrate, cracks occur in the sealing layer and the low-expansion substrate, and there is a risk of hermetic leakage. Therefore, when the object to be sealed has a lower expansion than the sealing material, it is important to reduce the thermal expansion coefficient of the sealing material. In particular, when Bi ₂ O ₃ -based glass is used as the glass powder, there is a natural limit to lowering the thermal expansion coefficient of the Bi ₂ O ₃ -based glass, so it is important to lower the thermal expansion coefficient of the ceramic powder. Become.

Therefore, the use of negative expansion ceramic powder can effectively lower the thermal expansion coefficient of the sealing material. It is known that the negative expansion of ceramic powder is caused by microcracks at grain boundaries caused by anisotropic expansion of crystal grains.

JP-A-63-315536 JP-A-8-59294

By the way, the thickness of the sealing layer is designed according to the application, but in recent years, the thickness of the sealing layer may be reduced. For example, in the case of laser sealing (sealing by laser beam irradiation), if the thickness of the sealing layer is reduced, the laser sealing performance can be significantly improved. Also, reducing the thickness of the sealing layer can contribute to the reduction in height and size of the hermetic package.

In order to reduce the thickness of the sealing layer, the particle size of the ceramic powder in the sealing material must be reduced. However, when the particle size of the negative expansion ceramic powder is reduced, specifically, when it is reduced to 20 μm or less, the number of microcracks at the crystal grain boundaries is reduced and the thermal expansion coefficient is increased. As a result, the negative expansion of the ceramic powder is not sufficiently expressed, and it becomes difficult to properly reduce the thermal expansion coefficient of the sealing material.

The present invention has been made in view of the above circumstances, and its technical object is to create a ceramic powder that exhibits negative expansion even if the particle size is small.

As a result of diligent efforts, the present inventors have solved the above technical problem by adopting a lithium aluminosilicate-based (hereinafter referred to as LAS-based) ceramic powder whose main crystal phase is β-eucryptite or β-quartz solid solution. It finds out that it can be solved, and proposes it as this invention. That is, in the ceramic powder of the present invention, β-eucryptite or β-quartz solid solution is precipitated as the main crystal phase (the crystal with the largest precipitation amount), the average particle diameter _D50 is 20 μm or less, and It is characterized by having a negative coefficient of thermal expansion at 30 to 300°C. A β-eucryptite or β-quartz solid solution is precipitated as a main crystal phase, and TiO ₂ and/or ZrO ₂ are included. Here, the "average particle diameter D ₅₀ " refers to the value measured by the laser diffraction method, and in the volume-based cumulative particle size distribution curve when measured by the laser diffraction method, the cumulative amount is accumulated from the smaller particle. represents the particle size that is 50% of the total. “Thermal expansion coefficient at 30 to 300° C.” can be measured by TMA (push rod type thermal expansion coefficient measurement). Although it is difficult to directly measure the thermal expansion coefficient of ceramic powder, a sintered body of a composite powder containing glass powder and ceramic powder at a predetermined volume ratio is used as a measurement sample, and the thermal expansion coefficient of the sintered body is measured. If measured, the coefficient of thermal expansion of the ceramic powder alone can be obtained by calculation.

Of the LAS-based crystals (Li ₂ O—Al ₂ O ₃ —nSiO ₂ ), β-eucryptite (Li ₂ O—Al ₂ O ₃ —2SiO ₂ ) and SiO ₂ are further solidified from β-eucryptite. The dissolved β-quartz solid solution (Li ₂ O—Al ₂ O ₃ —nSiO ₂ : n>2) has a negative expansion characteristic. On the other hand, when SiO ₂ in the LAS-based crystal (Li ₂ O—Al ₂ O ₃ —nSiO ₂ ) dissolves until n exceeds around 4, β-spodumene solid solution with a positive coefficient of thermal expansion is formed. It becomes easier to transfer. Therefore, in the ceramic powder of the present invention, β-eucryptite or β-quartz solid solution having negative expansion characteristics is precipitated as the main crystal phase.

Conventional LAS-based ceramic powder absorbs positive expansion in the a-axis direction and reflects negative expansion in the c-axis direction due to microcracks existing at the grain boundaries between crystal grains, so that the crystal grains as a whole has a negative volumetric expansion. These microcracks are generated by the anisotropic expansion of the crystal grains causing strain in the grain boundaries between the crystal grains. On the other hand, the microcracks do not occur when the crystal grain size is reduced. Therefore, it is difficult to refine the conventional LAS-based ceramic powder when applying it to a sealing material.

Through detailed research, the present inventors have found that when a small amount of a component that does not constitute an LAS-based crystal is dissolved in the main crystal, for example, when a small amount of TiO ₂ and/or ZrO ₂ is dissolved, the size of the crystal grains is small. Also, it was found that the negative expansion property can be maintained. Although the mechanism has not been experimentally proven, the present inventor believes that when a small amount of a dissimilar component is solid-dissolved in the LAS-based crystal, the crystal grain structure is distorted and the positive expansion of the a-axis becomes small. , the volume expansion of crystal grains becomes negative, and as a result, the negative expansion characteristic is maintained regardless of the presence or absence of microcracks. This mechanism is likely to occur when β-eucryptite or β-quartz solid solution is precipitated as the main crystal, even among negative expansion ceramic powders. It is presumed that similar effects can be obtained by reducing the positive expansion of the a-axis.

Secondly, the ceramic powder of the present invention preferably contains 16 to 30% Li ₂ O, 10 to 35% Al ₂ O ₃ and 30 to 68% SiO ₂ in terms of mol % composition. In this way, the positive expansion β-spodumene solid solution is less likely to precipitate, making it easier to maintain the negative expansion characteristics.

Third, the ceramic powders of the present invention are preferably substantially free of glass phases. This makes it difficult for the ceramic powder (particularly Li ₂ O) to melt into the glass during sealing, so that the sealing material is less likely to devitrify and the coefficient of thermal expansion of the sealing material is more likely to be maintained. Here, the presence or absence of the glass phase can be determined by an X-ray diffraction device or the like. For example, if the degree of crystallinity is 95% or more, it may be determined that the material does not substantially contain a glass phase. In addition, the "crystallinity" is obtained by measuring the X-ray diffraction by the powder method, calculating the area of the halo corresponding to the amorphous mass and the area of the peak corresponding to the mass of the crystal, respectively. It refers to the value obtained by the formula of [peak area]×100/[peak area+halo area] (%).

If the ceramic powder is produced by a solid-state reaction, it is possible to obtain a ceramic powder that does not substantially contain a glass phase. On the other hand, when the ceramic powder is produced by the melting method, the glass phase remains in the ceramic powder. The melting method is a method in which a raw material batch is once melted to obtain a glass melt, then the obtained melt is cooled, pulverized, and heat-treated as necessary to produce a ceramic powder.

Fourthly, in the sealing material of the present invention, the ceramic powder in the sealing material containing glass powder and ceramic powder is preferably the above ceramic powder.

Fifth, the sealing material of the present invention is preferably used for laser sealing.

1 is a schematic cross-sectional view for explaining one embodiment of an airtight package according to the present invention; FIG. Sample No. described in Table 2. 1 (before pulverization) is an electron micrograph. Sample No. described in Table 2. 1 (after pulverization) is an electron micrograph. Sample No. described in Table 2. 2 (before pulverization) is an electron micrograph. Sample No. described in Table 2. 2 (after pulverization) is an electron micrograph.

In the ceramic powder of the present invention, β-eucryptite or β-quartz solid solution is precipitated as the main crystal phase, and it is preferable that other crystals are not precipitated, but the effect of the present invention is not significantly impaired. A small amount of other crystals may be deposited as long as the crystals are present.

The ceramic powder of the present invention has a composition of Li ₂ O 16 to 30% (preferably 18 to 25%) and Al ₂ O ₁₀ to 35% (preferably 16 to 30%, more preferably 18% by mol) as a composition. 25%) and 30-68% SiO ₂ (preferably 40-68%, more preferably 50-64%). If the composition of the ceramic powder is outside the above range, it becomes difficult to deposit β-eucryptite or β-quartz solid solution as the main crystal phase, and if the particle size becomes small, it becomes difficult to maintain the negative expansion characteristic. In addition to the above components, other components such as sintering aids may be introduced within a range of 10% or less.

The ceramic powder of the present invention preferably contains TiO ₂ and/or ZrO ₂ in its composition, and the total content thereof is preferably 0.005 to 5 mol %, particularly preferably 0.1 to 4 mol %. The content of is also preferably 0.005 to 5 mol %, particularly preferably 0.1 to 4 mol %. If the content of TiO ₂ and/or ZrO ₂ is too low, the amount of solid solution of TiO ₂ and/or ZrO ₂ in the LAS-based crystal will decrease. As a result, when the particle size of the ceramic powder becomes small, it becomes difficult to maintain the negative expansion characteristic. On the other hand, if the content of TiO ₂ and/or ZrO ₂ is too high, not all of TiO ₂ and/or ZrO ₂ will form a solid solution in the LAS-based crystal, and will likely remain as an oxide. As a result, it becomes difficult to maintain the negative expansion characteristic of the ceramic powder.

In the ceramic powder of the present invention, the average particle size _D50 is 20 μm or less, preferably 10 μm or less, 7 μm or less, 5 μm or less, especially 1 to 3 μm. As described above, the ceramic powder of the present invention can maintain negative expansion characteristics even when the particle size is small. Therefore, the effect of the present invention is that the smaller the particle size, the greater the proportion of contribution to the negative expansion characteristic.

The maximum particle diameter D _max is preferably 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, especially 2 to 10 μm. As described above, the ceramic powder of the present invention can maintain negative expansion characteristics even when the particle size is small. Therefore, the effect of the present invention relatively increases as the particle size decreases. The “maximum particle diameter D _max ” refers to the value measured by the laser diffraction method, and in the volume-based cumulative particle size distribution curve measured by the laser diffraction method, the cumulative amount is accumulated from the smaller particle. It represents the particle size which is 99%.

The ceramic powder of the present invention has a negative thermal expansion coefficient (less than 0×10 ⁻⁷ /° C.) at 30 to 300° C., preferably −1×10 ⁻⁷ /° C. or less, −3×10 ⁻⁷ /° C. Below, in particular -20×10 ^-7 /°C or more and -4×10 ^-7 /°C or less. If the coefficient of thermal expansion at 30-300° C. is too high, it will be difficult to sufficiently reduce the coefficient of thermal expansion of the sealing material.

In the sealing material of the present invention, which contains glass powder and ceramic powder, the ceramic powder is preferably the above-mentioned ceramic powder. The technical features of the sealing material of the present invention partly overlap with the technical features of the ceramic powder of the present invention, and detailed descriptions of the overlapping parts are omitted.

In the sealing material of the present invention, the content of the ceramic powder is 1-45% by volume, preferably 10-45% by volume, 15-40% by volume, particularly 20-35% by volume. If the content of the ceramic powder is too high, the content of the glass powder becomes relatively low, making it difficult to ensure desired fluidity and thermal stability. If the content of the ceramic powder is too small, the effect of adding the ceramic powder will be poor.

As the ceramic powder, other ceramic powders may be introduced besides the ceramic powder of the present invention. etc., and the total content thereof is preferably 0 to 15% by volume, particularly preferably 0 to less than 10% by volume.

Various glass powders can be used as the glass powder in the sealing material of the present invention. For example, Bi ₂ O ₃ -based glass, V ₂ O ₅ -based glass, and SnO-based glass are preferable in terms of low melting point characteristics, and Bi ₂ O ₃ -based glass is particularly preferable in terms of thermal stability and water resistance. Here, the term "--based glass" refers to a glass containing specified components as essential components and having a total amount of specified components of 25 mol% or more, preferably 30 mol% or more, more preferably 35 mol% or more. point to From an environmental point of view, the glass powder preferably does not substantially contain PbO (less than 0.1 mol %) in the glass composition.

The Bi ₂ O ₃ -based glass preferably contains 28 to 60% Bi ₂ O ₃ , 15 to 37% B ₂ O ₃ , and 1 to 30% ZnO in mol % as the glass composition. The reason why the content range of each component is limited as described above will be explained below. In addition, in description of a glass composition range, % display points out mol%.

Bi ₂ O ₃ is a main component for lowering the softening point, and its content is preferably 28-60%, 33-55%, particularly 35-45%. If the content of Bi ₂ O ₃ is too small, the softening point becomes too high and the fluidity tends to decrease. On the other hand, if the Bi ₂ O ₃ content is too high, the glass tends to devitrify during firing, and this devitrification tends to reduce fluidity.

B ₂ O ₃ is an essential component as a glass-forming component, and its content is preferably 15 to 37%, 20 to 33%, particularly 25 to 30%. If the content of B ₂ O ₃ is too small, it becomes difficult to form a glass network, and the glass tends to devitrify during firing. On the other hand, if the content of B ₂ O ₃ is too high, the viscosity of the glass increases, and the fluidity tends to decrease.

ZnO is a component that enhances resistance to devitrification, and its content is preferably 1 to 30%, 3 to 25%, 5 to 22%, particularly 9 to 20%. If the content is less than 1% or more than 30%, the component balance of the glass composition is impaired, and devitrification resistance tends to decrease.

In addition to the above components, for example, the following components may be added.

SiO ₂ is a component that increases water resistance, but it also has the effect of raising the softening point. Therefore, the content of SiO ₂ is preferably 0-5%, 0-3%, 0-2%, particularly 0-1%. Also, if the content of SiO ₂ is too high, the glass tends to devitrify during firing.

Al ₂ O ₃ is a component that increases water resistance, and its content is preferably 0 to 10%, 0 to 5%, particularly 0.1 to 2%. If the content of Al ₂ O ₃ is too high, the softening point may increase unduly.

Li ₂ O, Na ₂ O and K ₂ O are components that reduce devitrification resistance. The content of Li ₂ O, Na ₂ O and K ₂ O is thus respectively 0-5%, 0-3% and in particular 0-1%.

MgO, CaO, SrO and BaO are components that increase devitrification resistance, but also components that increase the softening point. The contents of MgO, CaO, SrO and BaO are thus respectively 0-20%, 0-10% and especially 0-5%.

In order to _lower the softening point of the Bi ₂ O ₃ -based glass _, it is necessary to introduce a large amount of Bi ₂ O ₃ into the glass composition. It becomes easy to permeate, and the fluidity tends to decrease due to this devitrification. In particular, when the content of Bi ₂ O ₃ is 30% or more, this tendency becomes remarkable. As a countermeasure against this, if CuO is added, devitrification of the glass can be effectively suppressed even if the content of Bi ₂ O ₃ is 30% or more. Furthermore, if CuO is added, the laser absorption characteristics during laser sealing can be enhanced. The CuO content is preferably 0 to 40%, 5 to 35%, 10 to 30%, especially 15 to 25%. If the CuO content is too high, the balance of components in the glass composition is impaired, and the devitrification resistance tends to decrease.

Fe ₂ O ₃ is a component that enhances devitrification resistance and laser absorption characteristics, and its content is preferably 0 to 10%, 0.1 to 5%, particularly 0.5 to 3%. If the content of Fe ₂ O ₃ is too high, the component balance of the glass composition is impaired, and the devitrification resistance tends to decrease.

Sb ₂ O ₃ is a component that increases devitrification resistance, and its content is preferably 0 to 5%, particularly 0 to 2%. If the content of Sb ₂ O ₃ is too large, the component balance of the glass composition is impaired, and conversely, the devitrification resistance tends to decrease.

The average particle diameter D ₅₀ of the glass powder is preferably less than 15 μm, preferably 0.5-10 μm, especially 1-5 μm. The softening point of the glass powder decreases as the average particle diameter _D50 of the glass powder decreases.

The sealing material of the present invention may contain powder materials other than glass powder and ceramic powder. For example, 1 to 15% by volume of a laser absorber such as Mn--Fe--Al oxide, carbon, Mn--Fe--Cr oxide may be contained in order to enhance the laser absorption characteristics. Also, glass beads, spacers, etc. may be introduced.

Although the sealing material of the present invention may be used in a powder state, it is preferable to knead it uniformly with a vehicle to form a paste, which facilitates handling. A vehicle typically includes a solvent and a resin. Resin is added for the purpose of adjusting the viscosity of the paste. Moreover, a surfactant, a thickening agent, etc. can also be added as needed. The prepared paste is applied to the surface of the object to be sealed using a dispenser, a screen printer, or other applicator.

Usable resins include acrylic acid ester (acrylic resin), ethyl cellulose, polyethylene glycol derivatives, nitrocellulose, polymethylstyrene, polyethylene carbonate, methacrylic acid ester, and the like. In particular, acrylic acid esters and nitrocellulose are preferable because of their good thermal decomposability.

Solvents include N,N'-dimethylformamide (DMF), α-terpineol, higher alcohols, γ-butyl lactone (γ-BL), tetralin, butyl carbitol acetate, ethyl acetate, isoamyl acetate, diethylene glycol monoethyl ether, Diethylene glycol monoethyl ether acetate, benzyl alcohol, toluene, 3-methoxy-3-methylbutanol, water, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether , tripropylene glycol monobutyl ether, propylene carbonate, dimethylsulfoxide (DMSO), N-methyl-2-pyrrolidone and the like can be used. In particular, α-terpineol is preferred because it has high viscosity and good solubility in resins and the like.

The sealing material of the present invention has high fluidity and a low coefficient of thermal expansion during laser sealing, and therefore can be suitably used for laser sealing between a package substrate and a glass lid of an airtight package. An airtight package according to the present invention is an airtight package in which a package base and a glass lid are airtightly sealed via a sealing material layer, wherein the sealing material layer is a sintered body of a sealing material, and the sealing material layer is a sintered body of the sealing material. The bonding material is characterized by being the sealing material described above. Hereinafter, the airtight package according to the present invention will be described in detail.

The package base preferably has a base and a frame provided on the base. By doing so, it becomes easier to accommodate the internal elements such as the sensor element in the frame portion of the package base. The frame portion of the package base is preferably formed like a picture frame along the outer edge region of the package base. In this way, the effective area functioning as a device can be expanded. In addition, it becomes easy to accommodate an internal element such as a sensor element in the space inside the package substrate, and it becomes easy to perform wiring connection and the like.

The surface roughness Ra of the region where the sealing material layer is arranged on the top of the frame is preferably less than 1.0 μm. As the surface roughness Ra of the surface increases, the accuracy of laser sealing tends to decrease. Here, the "surface roughness Ra" can be measured by, for example, a stylus type or non-contact type laser film thickness meter or surface roughness meter.

The width of the top of the frame is preferably 100-7000 μm, 200-6000 μm, especially 300-5000 μm. If the width of the top of the frame is too narrow, it becomes difficult to align the sealing material layer and the top of the frame. On the other hand, if the width of the top of the frame is too wide, the effective area for functioning as a device becomes small.

The package substrate is preferably glass ceramic, aluminum nitride, aluminum oxide, or a composite material thereof (for example, aluminum nitride integrated with glass ceramic). Glass ceramics can easily form a sealing material layer and a reaction layer, so that strong sealing strength can be secured by laser sealing. Furthermore, since thermal vias can be easily formed, it is possible to appropriately prevent the hermetic package from excessively increasing in temperature. Since aluminum nitride and aluminum oxide have good heat dissipation properties, it is possible to properly prevent the situation in which the temperature of the airtight package rises excessively.

Glass ceramic, aluminum nitride, and aluminum oxide preferably have a black pigment dispersed therein (sintered with the black pigment dispersed therein). In this way, the package base can absorb the laser light transmitted through the sealing material layer. As a result, the portion of the package base which is in contact with the sealing material layer is heated during laser sealing, thereby promoting the formation of a reaction layer at the interface between the sealing material layer and the package base.

The package substrate in which the black pigment is dispersed has the property of absorbing the laser light to be irradiated, for example, the thickness is 0.5 mm and the total light transmittance at the wavelength (808 nm) of the laser light to be irradiated is 10% or less. (preferably 5% or less). This makes it easier for the temperature of the sealing material layer to rise at the interface between the package base and the sealing material layer.

The thickness of the base of the package substrate is preferably 0.1 to 2.5 mm, particularly 0.2 to 1.5 mm. This makes it possible to reduce the thickness of the hermetic package.

The height of the frame portion of the package base, that is, the height obtained by subtracting the thickness of the base from the package base is preferably 100 to 2500 μm, particularly 200 to 1500 μm. By doing so, it becomes easy to achieve a thin airtight package while properly housing the internal elements.

Various glasses can be used as the glass lid. For example, alkali-free glass, alkali borosilicate glass, and soda-lime glass can be used. Note that the glass lid may be laminated glass obtained by bonding a plurality of glass plates together.

The functional film may be formed on the inner element side surface of the glass lid, or may be formed on the outer surface of the glass lid. An antireflection film is particularly preferable as the functional film. Thereby, the light reflected on the surface of the glass lid can be reduced.

The thickness of the glass lid is preferably 0.1 mm or more, 0.15 to 2.0 mm, especially 0.2 to 1.0 mm. If the thickness of the glass lid is small, the strength of the hermetic package tends to decrease. On the other hand, if the thickness of the glass lid is large, it becomes difficult to reduce the thickness of the hermetic package.

The sealing material layer has the function of softening and deforming by absorbing laser light, forming a reaction layer on the surface layer of the package substrate, and hermetically integrating the package substrate and the glass lid.

The difference in thermal expansion coefficient between the glass lid and the sealing material layer is preferably less than 50×10 ⁻⁷ /°C, less than 40×10 ⁻⁷ /°C, and particularly preferably 30×10 ⁻⁷ /°C or less. If the thermal expansion coefficient difference is too large, the stress remaining in the sealed portion becomes unduly high, and the hermetic reliability of the hermetic package tends to decrease.

Preferably, the sealing material layer is formed so that the contact position with the frame is separated from the inner edge of the top of the frame and is separated from the outer edge of the top of the frame, More preferably, it is formed at a distance of 50 μm or more, 60 μm or more, 70 to 2000 μm, particularly 80 to 1000 μm from the inner edge of the top of the frame. If the distance between the inner edge of the top portion of the frame and the sealing material layer is too short, the heat generated by local heating during laser sealing will not easily escape, and the glass lid will easily break during the cooling process. . On the other hand, if the distance between the inner edge of the top of the frame and the sealing material layer is too long, it becomes difficult to miniaturize the hermetic package. The sealing layer is preferably formed at a position spaced apart from the outer edge of the top of the frame by 50 μm or more, 60 μm or more, 70 to 2000 μm, particularly 80 to 1000 μm. If the distance between the outer edge of the top part of the frame and the sealing material layer is too short, the heat generated by local heating during laser sealing will not easily escape, and the glass lid will easily break during the cooling process. . On the other hand, if the distance between the outer edge of the top of the frame and the sealing material layer is too long, it becomes difficult to miniaturize the hermetic package.

The sealing material layer is preferably formed so that the contact position with the glass lid is separated from the edge of the glass lid by 50 μm or more, 60 μm or more, 70 to 1500 μm, particularly 80 to 800 μm. If the distance between the edge of the glass lid and the sealing material layer is too short, a surface temperature difference between the inner element side surface and the outer surface of the glass lid will occur in the edge region of the glass lid during laser sealing. It becomes large, and the glass lid becomes easy to break.

The sealing material layer is preferably formed on the center line of the top of the frame in the width direction, that is, formed in the central region of the top of the frame. This makes it easier for the heat generated by localized heating to escape during laser sealing, so that the glass lid is less likely to break. If the width of the top portion of the frame portion is sufficiently large, the sealing material layer may not be formed on the center line of the top portion of the frame portion in the width direction.

The average thickness of the sealing material layer is preferably less than 8.0 μm, especially greater than or equal to 1.0 μm and less than 7.0 μm. The smaller the average thickness of the sealing material layer, the smaller the alpha ray emission rate in the hermetic package, which makes it easier to prevent soft errors in internal elements. The accuracy of laser sealing improves as the average thickness of the sealing material layer decreases. It can also reduce the residual stress in the sealed area after laser sealing when the thermal expansion coefficients of the sealing material layer and the glass lid are mismatched. As a method for regulating the average thickness of the sealing material layer as described above, there are a method of thinly applying the sealing material paste and a method of polishing the surface of the sealing material layer.

The maximum width of the sealing material layer is preferably ≧1 μm and ≦2000 μm, especially ≧100 μm and ≦1500 μm. Reducing the maximum width of the sealing material layer makes it easier to separate the sealing material layer from the edge of the frame, which makes it easier to reduce the stress remaining in the sealing portion after laser sealing. Furthermore, the width of the frame portion of the package base can be narrowed, and the effective area functioning as a device can be expanded. On the other hand, if the maximum width of the sealing material layer is too narrow, bulk fracture of the sealing material layer is likely to occur when a large shear stress is applied to the sealing material layer. Furthermore, the accuracy of laser sealing tends to be lowered.

The present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view for explaining one embodiment of an airtight package according to the present invention. As can be seen from FIG. 1, the hermetic package 1 comprises a package base 10 and a glass lid 11. As shown in FIG. The package base 10 also has a base portion 12 and a frame portion 13 in the shape of a picture frame on the outer peripheral edge of the base portion 12 . An internal element 14 is accommodated in a space surrounded by the frame portion 13 of the package base 10 . Electrical wiring (not shown) for electrically connecting the internal element 14 and the outside is formed in the package base 10 .

The sealing material layer 15 is a sintered body of sealing material, which contains glass powder and the refractory filler powder of the present invention, but does not substantially contain a laser absorber. Further, the sealing material layer 15 is arranged over the entire circumference of the top portion of the frame portion 13 between the top portion of the frame portion 13 of the package base 10 and the surface of the glass lid 11 on the internal element 14 side. The width of the sealing material layer 15 is smaller than the width of the top portion of the frame portion 13 of the package base 10 and further away from the edge of the glass lid 11 . Furthermore, the average thickness of the sealing material layer 15 is less than 8.0 μm.

The airtight package 1 can be manufactured as follows. First, the glass lid 11 with the sealing material layer 15 formed in advance is placed on the package substrate 10 so that the sealing material layer 15 and the top of the frame portion 13 are in contact with each other. Subsequently, while pressing the glass lid 11 using a pressing jig, a laser beam L emitted from a laser irradiation device is irradiated along the sealing material layer 15 from the glass lid 11 side. As a result, the sealing material layer 15 softens and flows and reacts with the surface layer of the top portion of the frame portion 13 of the package base 10, whereby the package base 10 and the glass lid 11 are hermetically integrated, and the hermetic structure of the hermetic package 1 is achieved. is formed.

The ceramic powder of the present invention is preferably produced by the following production method. That is, the method for producing a ceramic powder of the present invention includes the steps of firing a raw material batch to obtain a sintered body in which β-eucryptite or β-quartz solid solution is precipitated as a main crystal phase by a solid phase reaction; and pulverizing the aggregate to obtain a ceramic powder.

The method for producing a ceramic powder of the present invention has a step of firing a raw material batch and obtaining a sintered body by solid phase reaction. When a sintered body is produced by solid phase reaction, a glass phase remains in the sintered body. no longer. As a result, the ceramic powder (especially Li ₂ O) is less likely to melt into the glass during sealing, so that the sealing material is less likely to devitrify and the thermal expansion coefficient of the sealing material is more easily maintained.

Various raw materials can be used as raw materials for introducing Li, Al and Si, but among them, it is preferable to use pulverized pre-sintered bodies containing Li, Al and Si. By pre-sintering all or part of the introduced raw material, it is possible to homogenize the precipitated crystals and reduce variations in the properties of the ceramic powder. In addition to the pulverized presintered body containing Li, Al and Si, an oxide raw material, a hydroxide raw material, a carbonate raw material, and the like may be used.

When TiO ₂ and/or ZrO ₂ are dissolved in the LAS-based crystal, various raw materials can be used as raw materials for introducing Ti and Zr. , oxide raw materials, hydroxide raw materials, carbonate raw materials, and the like can be used.

Firing of the raw material batch can be performed in an electric furnace, a gas furnace, or the like. The calcination temperature of the raw material batch is preferably 1000-1450°C, especially 1250-1400°C. If the firing temperature is too low, the amount of precipitated crystals in the ceramic powder tends to decrease. On the other hand, if the firing temperature is too high, part of the sintered body will be vitrified and the glass phase will tend to remain in the sintered body. Moreover, since the degree of sintering of the sintered body increases, it becomes difficult to pulverize the sintered body. The firing time of the raw material batch is preferably 15 to 40 hours. If the sintering time is too short, the amount of precipitated crystals in the ceramic powder tends to decrease. On the other hand, if the firing time is too long, the degree of sintering of the sintered body increases, making it difficult to pulverize the sintered body.

The raw material batch is preferably wet pulverized and mixed using a ball mill or the like. By doing so, the homogeneity of the raw material batch is improved, so that the solid-phase reaction can be promoted.

The pulverization of the sintered body can be performed with a ball mill, jaw crusher, jet mill, disc mill, spectromill, grinder, mixer mill, etc. However, from the viewpoint of running cost and pulverization efficiency, a ball mill may be used in a wet or dry process. It is preferable to use The pulverized grain size of the sintered body is preferably smaller than the size of the precipitated crystal grains, and is preferably adjusted to such an extent that grain boundaries between crystal grains do not substantially contain microcracks. By doing so, the particle size of the ceramic powder becomes small, so that it can be suitably applied to an airtight package having a thin sealing layer. When the average particle diameter _D50 of the ceramic powder is less than 10 μm, the grain boundaries between the precipitated crystal grains are substantially free of microcracks.

After pulverizing the sintered body, it is preferable to perform sieve classification or air classification as necessary to adjust the particle size.

The present invention will be described in detail below based on examples. It should be noted that the following examples are merely illustrative. The present invention is by no means limited to the following examples.

(Preparation of pulverized pre-sintered body)
The raw materials shown in Table 1 were placed in an alumina pot having an internal volume of 3.6 L, and wet pulverized and mixed for 12 hours to prepare a raw material batch. For the pulverization and mixing, 3000 g of zirconia with a diameter of 3.0 mm was used as a pulverizing ball, and 600 ml of alcohol was used as a dispersion medium.

Next, the raw material batch was dried, pulverized, held in an electric furnace at 800° C. for 8 hours, and then fired at 1350° C. for 16 hours. The rate of temperature increase from room temperature to 800° C. was 5° C./min, the rate of temperature increase from 800° C. to 1350° C. was 1° C./min, and the rate of temperature drop from 1350° C. was 1° C./min.

Furthermore, by dry pulverization and wet pulverization, the obtained sintered body was pulverized to an average particle diameter D ₅₀ of 1.0 μm to prepare a pre-sintered pulverized product.

(Production of ceramic powder)
The raw material batches shown in Table 2 were placed in an alumina pot having an internal volume of 3.6 L, and wet pulverized and mixed for 12 hours. For the pulverization and mixing, 3000 g of zirconia with a diameter of 3.0 mm was used as a pulverizing ball, and 600 ml of alcohol was used as a dispersion medium.

Next, the raw material batch was dried, pulverized, held in an electric furnace at 800° C. for 8 hours, and then fired at 1350° C. for 16 hours. The rate of temperature increase from room temperature to 800° C. was 5° C./min, the rate of temperature increase from 800° C. to 1350° C. was 1° C./min, and the rate of temperature drop from 1350° C. was 1° C./min.

Furthermore, by dry pulverization and wet pulverization, the obtained sintered body was pulverized to an average particle diameter D ₅₀ of 1.0 μm. 1-3 were obtained. Sample no. The compositions of 1 to 3 are shown in Table 3. In addition, sample no. The main crystals of samples Nos. 1 and 2 are β-eucryptite. The main crystal of 3 was β-spodumene solid solution.

(Preparation of Bi ₂ O ₃ -based glass powder)
The glass composition contains 36% Bi ₂ O ₃ , 28% B ₂ O ₃ , 4% ZnO, 4% BaO, 25% CuO, 1% Fe ₂ O ₃ and 1% Al ₂ O ₃ in mol %. In order to obtain glass powder, a glass batch was prepared by mixing raw materials such as various oxides and carbonates. Next, the obtained molten glass was formed into flakes using a water-cooled roller. Finally, the flaky glass was pulverized with a ball mill and then air-classified to obtain a Bi ₂ O ₃ -based glass powder. The Bi ₂ O ₃ -based glass powder had an average particle diameter _D50 of 2.5 μm, a maximum particle diameter D _max of 10 μm, and a thermal expansion coefficient of 104×10 ⁻⁷ /°C at 30 to 300°C.

(Production of sealing material)
The Bi ₂ O ₃ -based glass powder and the ceramic powder shown in Table 3 were mixed at a volume ratio of 75:25 to obtain a sealing material.

The resulting sealing material is sintered at 500° C. to obtain a dense sintered body, and then the sintered body is processed into a predetermined shape to prepare a measurement sample for TMA (push bar type thermal expansion coefficient measurement). did. Using this measurement sample, TMA was performed in the temperature range of 30 to 300°C. The coefficient of thermal expansion α of the ceramic powder shown in Table 3 was calculated based on the coefficient of thermal expansion of the obtained sealing material.

FIG. 2 shows sample Nos. listed in Tables 2 and 3. 1 (before pulverization) is an electron micrograph. FIG. 3 shows sample Nos. listed in Tables 2 and 3. 1 (after pulverization) is an electron micrograph. FIG. 4 shows sample Nos. listed in Tables 2 and 3. 2 (before pulverization) is an electron micrograph. FIG. 5 shows sample Nos. listed in Tables 2 and 3. 2 (after pulverization) is an electron micrograph. 2-5, sample no. The size of the crystal grains of samples 1 and 2 before pulverization was about 10 μm, and the pulverization resulted in sample Nos. It can be seen that the particle diameters of 1 and 2 are smaller than the size of the crystal grains. And sample no. It can also be seen that substantially no microcracks are included in the grain boundaries between crystal grains 1 and 2.

As can be seen from Table 3, sample no. Nos. 1 and 2 had a negative expansion although the particle size was small. On the other hand, sample no. 3 was positive expansion.

1 airtight package 10 package base 11 glass lid 12 base 13 frame 14 internal element 15 sealing material layer L laser light

Claims (3)

In the sealing material containing the glass powder and the ceramic powder, the glass powder has, as a glass composition, Bi ₂ O ₃ 28 to 60%, B ₂ O ₃ 15 to 37%, ZnO 1 to 30% , The ceramic powder contains 10 to 40% CuO , has β-eucryptite or β-quartz solid solution precipitated as the main crystal phase, has an average particle diameter _D50 of 20 μm or less, and is 30 to 300 A sealing material having a negative coefficient of thermal expansion at °C, substantially free of a glass phase, and containing 0.005 to 5 mol% of TiO ₂ and/or ZrO ₂ in total in its composition. 2. The sealing material according to claim 1, wherein the ceramic powder contains 16 to 30% Li ₂ O, 10 to 35% Al ₂ O ₃ and 30 to 68% SiO ₂ in terms of mol %. . 3. The sealing material according to claim 1, which is used for laser sealing.

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