Ceramic powder, composite powder materials and sealing materials

Abstract

The ceramic powder is characterized in that β-eucryptite or β-quartz solid solution is precipitated as the main crystalline phase, and the average particle size D 50 The thickness is 20 μm or less, and the thermal expansion coefficient at 30 to 300° C. is negative.

Description

Technical Field

[0001] The invention relates to ceramic powder, composite powder material and sealing material. Background Art

[0002] As a sealing material, a composite powder material containing glass powder and ceramic powder is generally used. Compared with resin-based adhesives, this sealing material has excellent chemical durability and heat resistance and is suitable for ensuring airtightness.

[0003] As the sealing glass powder, a high-expansion low-melting-point glass such as PbO-based glass or Bi 2 O 3 -based glass can be used (see Patent Documents 1 and 2, etc.).

[0004] Sealing materials can also be used to seal low-expansion substrates, such as alumina substrates and glass substrates. However, if the thermal expansion coefficient of the sealing material is too high, there is a risk that, after sealing, undue residual strain will occur in the sealing layer or low-expansion substrate, leading to cracks in the sealing layer or low-expansion substrate, and thus, airtight leaks. Therefore, when the sealed object has a lower expansion than the sealing material, it is important to reduce the thermal expansion coefficient of the sealing material. In particular, when using Bi2O3-based glass as the glass powder, there is a natural limit to how low the thermal expansion coefficient of Bi2O3-based glass can be reduced, making it important to reduce the thermal expansion coefficient of the ceramic powder.

[0005] Therefore, if a ceramic powder with negative expansion is used, the thermal expansion coefficient of the sealing material can be effectively reduced. It should be noted that it is known that the negative expansion of ceramic powder is manifested by micro cracks at the grain boundaries caused by the anisotropic expansion of the crystal grains.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 63-315536

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 8-59294 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] However, the thickness of the sealing layer can be designed according to the application, and in recent years, there has been a trend to reduce the thickness of the sealing layer. For example, in the case of laser sealing (sealing using laser irradiation), reducing the thickness of the sealing layer can significantly improve the laser sealing performance. In addition, reducing the thickness of the sealing layer can contribute to the thinning and miniaturization of the airtight package.

[0012] To reduce the thickness of the sealing layer, the particle size of the ceramic powder in the sealing material must be reduced. However, if the particle size of the negatively expanding ceramic powder decreases, the microcracks at the grain boundaries decrease, and the thermal expansion coefficient increases. As a result, the negative expansion of the ceramic powder is not fully realized, making it difficult to appropriately reduce the thermal expansion coefficient of the sealing material.

[0013] On the other hand, lowering the thermal expansion coefficient of the glass powder also reduces the thermal expansion coefficient of the sealing material. In this case, the glass powder is less likely to soften and deform, requiring increased laser output during laser sealing. This can easily lead to cracks in the sealed object and the sealing layer. Bi2O3-based glass powder, in particular, exhibits the following properties: it does not unduly increase the softening point and is less likely to reduce the thermal expansion coefficient.

[0014] The first technical task of the present invention is to create a ceramic powder that exhibits negative expansion even when the particle size is small.

[0015] Furthermore, the present invention sets as a second technical problem the creation of a sealing material that has both low expansion and a low softening point even when the sealing thickness is narrowed, and a composite powder material suitable for the sealing material.

[0016] Means for solving problems

[0017] As a result of the inventor's dedicated efforts, it was discovered that by selecting a ceramic powder of a lithium aluminum silicate system (hereinafter referred to as LAS system) with β-eucryptite or β-quartz solid solution as the main crystalline phase, the above-mentioned first technical problem can be solved, and thus the present invention is proposed. That is, the ceramic powder of the present invention is characterized in that β-eucryptite or β-quartz solid solution is precipitated as the main crystalline phase (the crystal with the largest amount of precipitation), and the thermal expansion coefficient of 30 to 300°C is negative. Here, the "thermal expansion coefficient of 30 to 300°C" can be measured by TMA (pressed rod thermal expansion coefficient measurement). It should be noted that although it is difficult to directly measure the thermal expansion coefficient of ceramic powder, if a sintered body of a composite powder containing glass powder and ceramic powder in a specified volume ratio is used as a measurement sample and the thermal expansion coefficient of the sintered body is measured, the thermal expansion coefficient of the ceramic powder alone can be calculated.

[0018] Within LAS-based crystals (Li2O-Al2O3-nSiO2), β-eucryptite (Li2O-Al2O3-2SiO2) and a β-quartz solid solution (Li2O-Al2O3-nSiO2: n>2) containing SiO2 further dissolved in β-eucryptite exhibit negative thermal expansion characteristics. On the other hand, if SiO2 is dissolved in LAS-based crystals (Li2O-Al2O3-nSiO2) until n exceeds approximately 4, the phase transition to a β-spodumene solid solution with a positive thermal expansion coefficient becomes more likely. Therefore, the ceramic powder of the present invention precipitates a β-eucryptite or β-quartz solid solution with negative thermal expansion characteristics as the main crystalline phase.

[0019] Conventional LAS ceramic powders absorb the positive expansion in the a-axis direction due to the microcracks present in the grain boundaries between the grains, reflecting the negative expansion in the c-axis direction, thereby causing the overall volume expansion of the grains to become negative. These microcracks are caused by the following reasons: strain is generated in the grain boundaries between the grains due to the anisotropic expansion of the grains. On the other hand, if the size of the grains becomes smaller, these microcracks are no longer generated. Therefore, when conventional LAS ceramic powders are used in sealing materials, it is difficult to refine the particles.

[0020] The inventor has found through detailed investigation that if a small amount of a component that does not constitute LAS system crystallization is solid-dissolved in the main crystal, for example, if a small amount of TiO2 and / or ZrO2 is solid-dissolved, then even if the size of the grain is small, the negative expansion characteristic can be maintained. Its mechanism has not been experimentally proven, but the inventor speculates that if a small amount of a heterogeneous component is solid-dissolved in the LAS system crystallization, strain is generated in the grain structure, and the positive expansion of the a-axis is reduced, so the volume expansion of the grain becomes negative, and as a result, the negative expansion characteristic is maintained regardless of whether there are microcracks. Moreover, when β-eucryptite or β-quartz solid solution is precipitated as the main crystal in the negative expansion ceramic powder, this mechanism is easily reflected. It is speculated that even outside the above method, if strain is generated in the grain structure and the positive expansion of the a-axis is reduced, the same effect can be enjoyed.

[0021] The ceramic powder of the present invention preferably contains TiO2 and / or ZrO2 in its composition.

[0022] The ceramic powder of the present invention preferably has an average particle size D 50 Here, the average particle size D 50 ” refers to a value measured by laser diffraction, and indicates a particle size at which the cumulative amount from the smallest particle reaches 50% in a volume-based cumulative particle size distribution curve measured by laser diffraction.

[0023] The ceramic powder of the present invention preferably contains, in mol%, 16-30% Li2O, 16-30% Al2O3, and 40-68% SiO2. This makes it difficult for the positively expanding β-spodumene solid solution to precipitate, making it easier to maintain negative expansion characteristics.

[0024] The ceramic powder of the present invention preferably does not substantially contain a glass phase. In this way, it becomes difficult for the ceramic powder (especially Li2O) to melt into the glass during sealing, so the sealing material becomes difficult to lose clarity and it becomes easy to maintain the thermal expansion coefficient of the sealing material. Here, the presence or absence of a glass phase can be determined by an X-ray diffraction device or the like. For example, if the crystallinity is 95% or more, it can also be determined that it does not substantially contain a glass phase. It should be noted that "crystallinity" refers to the value obtained by measuring X-ray diffraction by a powder method, thereby calculating the area of ​​the halo equivalent to the mass of the amorphous and the area of ​​the peak equivalent to the mass of the crystalline, and then calculating the value according to the formula [area of ​​the peak] × 100 / [area of ​​the peak + area of ​​the halo] (%).

[0025] When ceramic powder is produced by a solid-phase reaction, a ceramic powder substantially free of a glass phase is obtained. On the other hand, when ceramic powder is produced by a melting method, a glass phase remains in the ceramic powder. It should be noted that the melting method is a method of producing ceramic powder by temporarily melting a raw material batch to obtain a glass melt, then cooling and pulverizing the resulting melt, and optionally performing a heat treatment.

[0026] The inventors have diligently researched and discovered that the second technical problem can be solved by selecting an LAS-based ceramic powder containing a β-eucryptite or β-quartz solid solution as the main crystalline phase and compounding it with glass powder, thereby providing the present invention. Specifically, the composite powder material of the present invention is characterized in that, in the composite powder material containing glass powder and ceramic powder, the ceramic powder includes the aforementioned ceramic powder.

[0027] The composite powder material of the present invention preferably has a glass powder containing, in mol%, 28 to 60% of Bi2O3, 15 to 37% of B2O3, and 1 to 30% of ZnO as a glass composition.

[0028] The sealing material of the present invention, which has been created to solve the second technical problem, is characterized by containing the composite powder material.

[0029] The sealing material of the present invention is preferably used for laser sealing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic cross-sectional view for explaining one embodiment of the airtight package.

[0031] Figure 2This is an electron microscope photograph of Sample No. 1 (before pulverization) described in Table 2.

[0032] Figure 3 This is an electron microscope photograph of Sample No. 1 (after crushing) listed in Table 2.

[0033] Figure 4 This is an electron microscope photograph of Sample No. 2 (before pulverization) described in Table 2.

[0034] Figure 5 This is an electron microscope photograph of Sample No. 2 (after crushing) described in Table 2. DETAILED DESCRIPTION

[0035] In this embodiment, the composite powder material contains glass powder and ceramic powder. The glass powder acts as a flux, softening and flowing during laser sealing to achieve airtight integration of the sealed objects. The ceramic powder acts as an aggregate, reducing the thermal expansion coefficient of the composite powder material and increasing the mechanical strength of the sealing layer.

[0036] The ceramic powder preferably precipitates β-eucryptite or β-quartz solid solution as the main crystal phase without precipitating other crystals. However, other crystals may be precipitated in small amounts as long as the effects of the present invention are not significantly impaired.

[0037] The above-mentioned ceramic powder preferably contains, in mole %, 16-30% (preferably 18-25%) of Li2O, 10-35% (preferably 16-30%, more preferably 18-25%) of Al2O3, and 30-68% (preferably 40-68%, more preferably 48-64%) of SiO2 as a composition. If the composition of the ceramic powder is outside the above range, it becomes difficult to precipitate β-eucryptite or β-quartz solid solution as the main crystalline phase, and if the particle size becomes smaller, it becomes difficult to maintain the negative expansion characteristics. It should be noted that in addition to the above-mentioned components, other components such as sintering aids may also be introduced in a range of less than 10%.

[0038] The above-mentioned ceramic powder preferably contains TiO2 and / or ZrO2 in its composition. The total content thereof is preferably 0.005 to 5 mol%, particularly 0.1 to 4 mol%, and the individual contents are also preferably 0.005 to 5 mol%, particularly 0.1 to 4 mol%. When the content of TiO2 and / or ZrO2 is too low, the amount of TiO2 and / or ZrO2 dissolved in the LAS crystals decreases. As a result, if the particle size of the ceramic powder becomes smaller, it becomes difficult to maintain the negative expansion characteristics. On the other hand, if the content of TiO2 and / or ZrO2 is too high, neither TiO2 nor ZrO2 dissolves in the LAS crystals and tends to remain as oxides. As a result, it becomes difficult to maintain the negative expansion characteristics of the ceramic powder.

[0039] The average particle size D of the ceramic powder mentioned above 50 It is preferably less than 20 μm, less than 10 μm, less than 7 μm, less than 5 μm, and particularly less than 1 to 3 μm. The above-mentioned ceramic powder can maintain negative expansion characteristics even if the particle size is small. Therefore, the effect is that the smaller the particle size of the ceramic powder, the greater the proportion of its contribution to negative expansion. Here, the "average particle size D 50 ” refers to a value measured by laser diffraction, and indicates a particle size at which the cumulative amount from the smallest particle reaches 50% in a volume-based cumulative particle size distribution curve measured by laser diffraction.

[0040] The maximum particle size D of the ceramic powder mentioned above max It is preferably 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, and particularly 2 to 10 μm. The above-mentioned ceramic powder can maintain negative expansion characteristics even with a small particle size. Therefore, the smaller the particle size of the ceramic powder, the greater the proportion of its contribution to the negative expansion characteristics. Here, the "maximum particle size D max ” refers to a value measured by laser diffraction, and indicates a particle size at which the cumulative amount from the smallest particle reaches 99% in a cumulative particle size distribution curve based on volume when measured by laser diffraction.

[0041] The thermal expansion coefficient of the ceramic powder at 30-300°C is negative (less than 0×10 -7 / ℃), preferably -1×10 -7 / ℃ or less, -3×10 -7 / ℃ or below, especially -20×10 -7 / ℃ and above -4×10 -7 If the thermal expansion coefficient at 30 to 300° C. is too high, it becomes difficult to sufficiently reduce the thermal expansion coefficient of the sealing material.

[0042] In the composite powder material described above, the ceramic powder content is 1 to 45% by volume, preferably 10 to 45% by volume, 15 to 40% by volume, and particularly 20 to 35% by volume. If the ceramic powder content is too high, the glass powder content becomes relatively low, making it difficult to ensure the desired fluidity and thermal stability. However, if the ceramic powder content is too low, the effect of adding the ceramic powder is reduced.

[0043] In addition to the above-mentioned ceramic powders, other ceramic powders may also be introduced as ceramic powders. For example, the other ceramic powders may include one or more selected from cordierite, zircon, alumina, mullite, willemite, zirconium phosphate, zirconium phosphotungstate, zirconium tungstate, etc., and the total content thereof is preferably 0 to 15% by volume, particularly 0% by volume or more and less than 10% by volume.

[0044] In the above-mentioned composite powder material, various glass powders can be used as glass powder. For example, Bi2O3-based glass, V2O5-based glass, and SnO-based glass are suitable from the perspective of low melting point characteristics, and Bi2O3-based glass is particularly preferred from the perspective of thermal stability and water resistance. Here, the so-called "Bi2O3-based glass" refers to glass containing the specified components as essential components, and the total amount of the specified components is 25 mol% or more, preferably 30 mol% or more, and more preferably 35 mol% or more. It should be noted that, from an environmental perspective, the glass powder preferably does not substantially contain PbO (less than 0.1 mol%) in the glass composition.

[0045] Bi2O3-based glass preferably contains, in mol%, 28-60% Bi2O3, 15-37% B2O3, and 1-30% ZnO. The following explains the reasons for limiting the content ranges of each component as described above. It should be noted that the expression "%" in the description of glass composition ranges refers to mole %.

[0046] Bi2O3 is a major component for lowering the softening point, and its content is preferably 28-60%, 33-55%, and particularly 35-45%. If the Bi2O3 content is too low, the softening point becomes excessively high, and fluidity tends to decrease. On the other hand, if the Bi2O3 content is too high, the glass tends to devitrify during firing, and this devitrification tends to reduce fluidity.

[0047] B2O3 is an essential glass-forming component, and its content is preferably 15-37%, 20-33%, and particularly 25-30%. If the B2O3 content is too low, it becomes difficult to form a glass network, and the glass is prone to devitrification during firing. On the other hand, if the B2O3 content is too high, the viscosity of the glass increases, and the fluidity tends to decrease.

[0048] ZnO is a component that improves devitrification resistance, and its content is preferably 1-30%, 3-25%, 5-22%, and particularly 9-20%. If its content is less than 1% or more than 30%, the component balance of the glass composition is impaired, and devitrification resistance is likely to decrease.

[0049] In addition to the above-mentioned components, for example, the following components may be added.

[0050] SiO2 is a component that improves water resistance, but also has the effect of raising the softening point. Therefore, the SiO2 content is preferably 0-5%, 0-3%, 0-2%, and particularly 0-1%. In addition, if the SiO2 content is too high, the glass will easily lose clarity during firing.

[0051] Al2O3 is a component that improves water resistance, and its content is preferably 0 to 10%, 0 to 5%, and particularly 0.1 to 2%. If the Al2O3 content is too high, the softening point may be unduly increased.

[0052] Li2O, Na2O, and K2O are components that reduce devitrification resistance. Therefore, the contents of Li2O, Na2O, and K2O are 0 to 5%, 0 to 3%, and particularly 0% or more and less than 1%, respectively.

[0053] MgO, CaO, SrO, and BaO are components that improve devitrification resistance but also increase the softening point. Therefore, the contents of MgO, CaO, SrO, and BaO are 0-20%, 0-10%, and particularly 0-5%, respectively.

[0054] In order to lower the softening point of Bi2O3-based glass, a large amount of Bi2O3 needs to be introduced into the glass composition. However, if the Bi2O3 content is increased, the glass becomes more likely to lose clarity during firing, and the fluidity is easily reduced due to this loss of clarity. In particular, this tendency becomes significant when the Bi2O3 content reaches 30% or more. As a countermeasure, the addition of CuO can effectively suppress the loss of clarity of the glass even when the Bi2O3 content is 30% or more. In addition, the addition of CuO can improve the laser absorption characteristics during laser sealing. The CuO content is preferably 0-40%, 5-35%, 10-30%, and particularly 15-25%. If the CuO content is too high, the component balance of the glass composition is impaired, and the resistance to loss of clarity is easily reduced.

[0055] Fe2O3 is a component that improves devitrification resistance and laser absorption properties, and its content is preferably 0-10%, 0.1-5%, and particularly 0.5-3%. If the Fe2O3 content is too high, the component balance of the glass composition is impaired, and the devitrification resistance is easily reduced.

[0056] Sb2O3 is a component that improves devitrification resistance, and its content is preferably 0 to 5%, particularly 0 to 2%. If the Sb2O3 content is too high, the component balance of the glass composition is impaired, and devitrification resistance tends to decrease.

[0057] The average particle size D of the glass powder mentioned above 50 The average particle size D of the glass powder is preferably less than 15 μm, 0.5 to 10 μm, and particularly 1 to 5 μm. 50 The smaller the particle size, the lower the softening point of the glass powder. 50 ” refers to a value measured by laser diffraction, and indicates a particle size at which the cumulative amount from the smallest particle reaches 50% in a volume-based cumulative particle size distribution curve measured by laser diffraction.

[0058] The composite powder material described above may contain other powder materials besides glass powder and ceramic powder. For example, to enhance laser absorption properties, it may contain 1-15% by volume of a laser absorbent such as a Mn-Fe-Al oxide, carbon, or a Mn-Fe-Cr oxide. Furthermore, glass beads, spacers, and the like may be incorporated.

[0059] The above-mentioned composite powder material can also be used in a powder state, but if it is evenly mixed with a vehicle liquid and pasted, it becomes easy to operate and is preferred. The vehicle liquid usually contains a solvent and a resin. The resin is added for the purpose of adjusting the viscosity of the paste. In addition, a surfactant, a thickener, etc. can also be added as needed. The paste produced can be applied to the surface of the sealed object using a coating machine such as a dispenser or a screen printer.

[0060] As the resin, acrylate (acrylic resin), ethyl cellulose, polyethylene glycol derivatives, nitrocellulose, polymethylstyrene, polyethylene carbonate, methacrylate, etc. Acrylate and nitrocellulose are particularly preferred due to their good thermal decomposition properties.

[0061] Examples of solvents that can be used include N,N′-dimethylformamide (DMF), α-terpineol, higher alcohols, γ-butyrolactone (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, dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone. α-terpineol is particularly preferred because it has high viscosity and good solubility in resins and the like.

[0062] The ceramic powder is preferably produced by the following manufacturing method. Specifically, the manufacturing method preferably includes the following steps: sintering a raw material batch to obtain a sintered body through a solid-phase reaction, wherein the sintered body precipitates a β-eucryptite or β-quartz solid solution as the main crystalline phase; and pulverizing the sintered body to obtain the ceramic powder.

[0063] In the ceramic powder production method, if a sintered body is produced through a solid-phase reaction as described above, no glass phase remains in the sintered body. As a result, the ceramic powder (particularly Li2O) is less likely to melt into the glass during sealing, preventing the glass from devitrifying and making it easier to maintain the thermal expansion coefficient of the sealing material.

[0064] As the raw materials for the introduction of Li, Al, and Si, various raw materials can be used, but it is preferred to use a pulverized product of a pre-sintered body containing Li, Al, and Si. If all or part of the raw materials are pre-sintered, it becomes possible to achieve homogenization of the precipitated crystals, which can reduce the variation in the characteristics of the ceramic powder. In addition to the pulverized product of the pre-sintered body containing Li, Al, and Si, oxide raw materials, hydroxide raw materials, carbonate raw materials, etc. can also be used.

[0065] When TiO2 and / or ZrO2 are dissolved in LAS-based crystals, various raw materials can be used as the raw materials for introducing Ti and Zr, for example, crushed materials of pre-sintered bodies containing Ti and Zr, oxide raw materials, hydroxide raw materials, carbonate raw materials, etc.

[0066] The firing of the raw material batch can be carried out by an electric furnace, a gas furnace, etc. The firing temperature of the raw material batch is preferably 1000-1450°C, in particular 1250-1400°C. If the firing temperature is too low, the amount of precipitated crystals of the ceramic powder will tend to decrease. On the other hand, if the firing temperature is too high, part of the sintered body will be vitrified, and it will tend to leave a glass phase in the sintered body. In addition, the sintering degree of the sintered body will increase, and therefore the crushing of the sintered body will become difficult. The firing time of the raw material batch is preferably 15-40 hours. If the firing time is too short, the amount of precipitated crystals of the ceramic powder will tend to decrease. On the other hand, if the firing time is too long, the sintering degree of the sintered body will increase, and therefore the crushing of the sintered body will become difficult.

[0067] The raw material batch is preferably wet-milled and mixed using a ball mill, etc. This improves the homogeneity of the raw material batch, thereby promoting the solid phase reaction.

[0068] The pulverization of the sintered body can be carried out by a ball mill, a jaw crusher, a jet mill, a disc mill, a high-energy ball mill (SpectroMill), a grinder, a mixing mill, etc. From the viewpoint of operating cost and pulverization efficiency, it is preferred to use a ball mill and perform the pulverization in a wet or dry manner. The pulverized particle size of the sintered body is preferably smaller than the size of the precipitated grains, and is preferably adjusted to a degree that substantially does not contain microcracks at the grain boundaries between the grains. In this way, the particle size of the ceramic powder becomes smaller, and therefore becomes suitable for use in an airtight package with a small thickness of the sealing layer. It should be noted that if the average particle size D of the ceramic powder is less than 0.05, the average particle size D of the ceramic powder is less than 0.05, and ... 50 When the particle size is less than 10 μm, microcracks are substantially not present in the grain boundaries between the precipitated grains.

[0069] After the sintered body is pulverized, it is preferably subjected to sieve classification or air classification as needed to adjust the particle size.

[0070] The composite powder material exhibits high fluidity and a low thermal expansion coefficient during laser sealing, making it suitable for use as a sealing material during laser sealing. Specifically, it can be suitably used for laser sealing between the package base and the glass cover of an airtight package. Specifically, in an airtight package in which the package base and the glass cover are hermetically sealed via a sealing layer, the sealing layer preferably comprises a sintered body of the composite powder material. The airtight package is described in detail below.

[0071] The package base preferably includes a base and a frame portion provided on the base. This facilitates the placement of internal components, such as sensor elements, within the package base frame. The package base frame is preferably formed in a frame-like shape along the outer edge of the package base. This increases the effective area within which the device functions. Furthermore, internal components, such as sensor elements, can be easily accommodated within the space within the package base, and wiring bonding and the like are also facilitated.

[0072] The surface roughness Ra of the area where the sealing layer is placed on the top of the frame is preferably less than 1.0 μm. If the surface roughness Ra of this surface increases, the accuracy of laser sealing will be easily reduced. Here, "surface roughness Ra" can be measured, for example, using a stylus-type or non-contact laser film thickness meter or surface roughness meter.

[0073] The width of the frame top is preferably 100 to 7000 μm, 200 to 6000 μm, and particularly 300 to 5000 μm. If the width of the frame top is too narrow, alignment of the sealing layer and the frame top becomes difficult. On the other hand, if the width of the frame top is too wide, the effective area for the device to function becomes smaller.

[0074] The package substrate is preferably any one of glass ceramic, aluminum nitride, aluminum oxide, or a composite material thereof (e.g., a composite material formed by integrating aluminum nitride with glass ceramic). Glass ceramic easily forms a reaction layer with the sealing layer, so that a strong sealing strength can be ensured by laser sealing. In addition, thermal vias can be easily formed, so that the temperature of the airtight package can be appropriately prevented from excessively rising. Aluminum nitride and aluminum oxide have good heat dissipation properties, so the temperature of the airtight package can be appropriately prevented from excessively rising.

[0075] Glass ceramic, aluminum nitride, or aluminum oxide is preferably dispersed with a black pigment (sintered while still containing the black pigment). This allows the package substrate to absorb the laser light transmitted through the sealing layer. As a result, the portion of the package substrate in contact with the sealing layer is heated during laser sealing, promoting the formation of a reaction layer at the interface between the sealing layer and the package substrate.

[0076] The package substrate in which the black pigment is dispersed preferably has the property of absorbing the laser light to be irradiated. For example, it is preferably 0.5 mm thick and has a total light transmittance of 10% or less (ideally 5% or less) at the wavelength of the laser light to be irradiated (808 nm). This will facilitate the temperature increase of the sealing layer at the interface between the package substrate and the sealing layer.

[0077] The thickness of the base portion of the package base is 0.1 to 2.5 mm, particularly 0.2 to 1.5 mm, thereby achieving a thinner airtight package.

[0078] The height of the frame 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. This allows for adequate storage of internal components and facilitates thinning of the airtight package.

[0079] As the glass cover, various glasses can be used. For example, alkali-free glass, alkali borosilicate glass, and soda-lime glass can be used. It should be noted that the glass cover can also be laminated glass formed by laminating multiple glass plates.

[0080] The functional film can be formed on the surface of the glass cover facing the inner element, or on the outer surface of the glass cover. An antireflection film is particularly preferred as the functional film. This can reduce light reflected from the surface of the glass cover.

[0081] The thickness of the glass cover is preferably 0.1 mm or more, 0.15 to 2.0 mm, and particularly 0.2 to 1.0 mm. If the thickness of the glass cover is small, the strength of the airtight package is likely to decrease. On the other hand, if the thickness of the glass cover is large, it is difficult to achieve a thinner airtight package.

[0082] The sealing layer softens and deforms by absorbing the laser light, forming a reaction layer on the surface of the package base, which has the function of airtightly integrating the package base and the glass cover.

[0083] The difference in thermal expansion coefficient between the glass cover and the sealing layer is preferably less than 50×10 -7 / ℃, less than 40×10 -7 / ℃, especially 30×10 -7 If the difference in thermal expansion coefficient is too large, the stress remaining in the sealed portion becomes excessively high, and the airtight reliability of the airtight package is likely to decrease.

[0084] The sealing layer is preferably formed in a manner that the contact position with the frame is staggered from the inner end edge of the top of the frame, and is formed in a manner that is staggered from the outer end edge of the top of the frame, and is more preferably formed at a position 50 μm or more, 60 μm or more, 70 to 2000 μm, and especially 80 to 1000 μm away from the inner end edge of the top of the frame. If the distance between the inner end edge of the top of the frame and the sealing layer is too short, the heat generated by local heating during laser sealing is difficult to dissipate, so the glass cover is easily damaged during the cooling process. On the other hand, if the distance between the inner end edge of the top of the frame and the sealing layer is too long, the miniaturization of the airtight package becomes difficult. In addition, it is preferably formed at a position 50 μm or more, 60 μm or more, 70 to 2000 μm, and especially 80 to 1000 μm away from the outer end edge of the top of the frame. If the distance between the outer edge of the frame top and the sealing layer is too short, the heat generated by localized heating during laser sealing will be difficult to dissipate, and the glass cover will be more likely to break during the cooling process. On the other hand, if the distance between the outer edge of the frame top and the sealing layer is too long, it will be difficult to miniaturize the airtight package.

[0085] The sealing layer is preferably formed so that the contact point with the cover glass is at least 50 μm, at least 60 μm, 70 to 1500 μm, and particularly 80 to 800 μm from the edge of the cover glass. If the distance between the edge of the cover glass and the sealing layer is too short, the surface temperature difference between the inner component-side surface and the outer surface of the cover glass at the edge of the cover glass during laser sealing will increase, making the cover glass more susceptible to breakage.

[0086] The sealing layer is preferably formed along the centerline of the width of the frame top, that is, in the central area of ​​the frame top. This allows heat generated by localized heating during laser sealing to dissipate more easily, thus preventing the glass cover from breaking. It should be noted that if the width of the frame top is sufficiently large, the sealing layer does not need to be formed along the centerline of the width of the frame top.

[0087] The average thickness of the sealing layer is preferably less than 8.0 μm, in particular, greater than 1.0 μm and less than 7.0 μm. The smaller the average thickness of the sealing layer, the less the α-ray emission rate in the airtight package, and thus it is easy to prevent soft errors (soft errors) of internal components. The smaller the average thickness of the sealing layer, the higher the accuracy of laser sealing. In addition, when the thermal expansion coefficient of the sealing layer does not match that of the glass cover, the stress remaining in the sealing portion after laser sealing can also be reduced. It should be noted that as a method of limiting the average thickness of the sealing layer as described above, a method of thinly applying a composite powder material paste and a method of grinding the surface of the sealing layer can be cited.

[0088] The maximum width of the sealing layer is preferably greater than 1 μm and less than 2000 μm, particularly greater than 100 μm and less than 1500 μm. If the maximum width of the sealing layer is narrowed, it is easy to offset the sealing layer from the end edge of the frame, thereby easily reducing the stress remaining in the sealed portion after laser sealing. In addition, the width of the frame portion of the package base can be narrowed, which can expand the effective area that functions as a device. On the other hand, if the maximum width of the sealing layer is too narrow, when a large shear stress is applied to the sealing layer, the sealing layer is easily destroyed as a whole. Furthermore, the accuracy of laser sealing becomes easily reduced.

[0089] Below, with reference to the attached Figure 1 An embodiment of the airtight package will be described. Figure 1 As shown, the airtight package 1 includes a package base 10 and a glass cover 11. The package base 10 also includes a base 12, and a frame 13 in the form of a frame frame on the outer edge of the base 12. An internal component 14 is housed within the space enclosed by the frame 13 of the package base 10. It should be noted that electrical wiring (not shown) is formed within the package base 10 to electrically connect the internal component 14 to the outside.

[0090] The sealing layer 15 is a sintered body of a composite powder material comprising glass powder and refractory filler powder containing the aforementioned ceramic powder, and contains substantially no laser absorber. Furthermore, the glass powder contains, in mole percent, 28-60% Bi2O3, 15-37% B2O3, and 1-30% ZnO, and contains substantially no PbO. Furthermore, the sealing layer 15 is disposed between the top of the frame 13 of the package base 10 and the surface of the glass cover 11 on the side facing the internal element 14, extending around the periphery of the top of the frame 13. The width of the sealing layer 15 is smaller than the width of the top of the frame 13 of the package base 10 and is offset from the edge of the glass cover 11. Furthermore, the average thickness of the sealing layer 15 is less than 8.0 μm.

[0091] The airtight package 1 can be manufactured as follows. First, a glass cover 11, which has been pre-formed with a sealing layer 15, is placed on the package base 10 so that the sealing layer 15 contacts the top of the frame 13. Next, while pressing the glass cover 11 with a pressing jig, laser light L emitted from a laser irradiation device is irradiated from the glass cover 11 side along the sealing layer 15. As a result, the sealing layer 15 softens and flows, reacting with the surface layer at the top of the frame 13 of the package base 10, and the package base 10 and the glass cover 11 are airtightly integrated, thereby forming the airtight structure of the airtight package 1.

[0092] It should be noted that the ceramic powder is preferably used as a composite powder material with glass powder, but its use is not limited to this. In addition to sealing applications, the composite powder material can also be used for insulation coatings against low-expansion materials, and can also be used for painting by adding or mixing pigments.

[0093] Example

[0094] The present invention will be described in detail below based on the following examples. It should be noted that the following examples are merely illustrative and the present invention is not limited to the following examples.

[0095] (Production of Pulverized Material of Pre-sintered Body)

[0096] The raw materials listed in Table 1 were placed in an alumina can with an internal volume of 3.6 L and subjected to wet grinding and mixing for 12 hours to prepare a raw material batch. The grinding and mixing used 3000 g of 3.0 mm φ zirconium oxide grinding balls and 600 ml of alcohol as the dispersion medium.

[0097] [Table 1]

[0098] (quality%) Pre-sintered body 1 Pre-sintered body 2 aluminum hydroxide 44 31 lithium carbonate 23 15 Silicon oxide 33 54

[0099] Next, the raw material batch was dried and crushed, held at 800°C in an electric furnace for 8 hours, and then calcined at 1350°C for 16 hours. The heating rate from room temperature to 800°C was 5°C / min, the heating rate from 800°C to 1350°C was 1°C / min, and the cooling rate from 1350°C was 1°C / min.

[0100] The obtained sintered body is then pulverized by dry pulverization and wet pulverization to an average particle size of D 50 =1.0 μm, and a pulverized product of the pre-sintered body was produced.

[0101] (Production of ceramic powder)

[0102] The raw material batches listed in Table 2 were placed in an alumina can with an internal volume of 3.6 L and subjected to wet grinding and mixing for 12 hours. During the grinding and mixing, 3000 g of 3.0 mm φ zirconium oxide grinding balls were used, and 600 ml of alcohol was used as the dispersion medium.

[0103] [Table 2]

[0104] (quality%) No.1 No.2 No.3 Pre-sintered body 1 98 98 0 Pre-sintered body 2 0 0 98 aluminum hydroxide 0 0 0 lithium carbonate 0 0 0 Silicon oxide 0 0 0 titanium oxide 2 0 0 Zirconia 0 2 2

[0105] Next, the raw material batch was dried and crushed, held at 800°C in an electric furnace for 8 hours, and then calcined at 1350°C for 16 hours. The heating rate from room temperature to 800°C was 5°C / min, the heating rate from 800°C to 1350°C was 1°C / min, and the cooling rate from 1350°C was 1°C / min.

[0106] The obtained sintered body is then pulverized by dry pulverization and wet pulverization to an average particle size of D 50 =1.0 μm, and samples No. 1 to 3 were obtained. The compositions of samples No. 1 to 3 are shown in Table 3. Note that the main crystals of samples No. 1 and 2 were β-eucryptite, and the main crystal of sample No. 3 was a β-spodumene solid solution.

[0107] [Table 3]

[0108]

[0109] (Preparation of Bi2O3-based glass powder)

[0110] In order to obtain glass powder containing Bi2O3 38%, B2O3 27%, ZnO 5%, BaO 4%, CuO 24%, Fe2O3 1% and Al2O3 1% as glass composition in mol%, a glass batch containing various oxides, carbonates and other raw materials is prepared, placed in a platinum crucible, and melted at 1000-1100°C for 2 hours. Next, the obtained molten glass is formed into flakes by water-cooled rollers. Finally, the flake-shaped glass is crushed by a ball mill and air-classified to obtain Bi2O3-based glass powder. It should be noted that the average particle size D of the Bi2O3-based glass powder is 2.37mm. 50 The maximum particle size is 2.5 μm and the maximum particle size D max The thermal expansion coefficient of 10μm and 30-300℃ is 104×10 -7 / ℃.

[0111] (Production of composite powder materials)

[0112] The Bi2O3-based glass powder and the ceramic powder listed in Table 3 were mixed at a volume ratio of 75:25 to obtain a composite powder material (sealing material).

[0113] The resulting composite powder material was sintered at 500°C to obtain a dense sintered body. This sintered body was then processed into a predetermined shape to prepare a sample for TMA (Temperature Measurement of Thermal Expansion). Using this sample, TMA was performed within a temperature range of 30-300°C. Based on the thermal expansion coefficient of the resulting composite powder material, the thermal expansion coefficient α of the ceramic powders listed in Table 3 was calculated.

[0114] Figure 2 This is an electron microscope photograph of Sample No. 1 (before pulverization) described in Tables 2 and 3. Figure 3 This is an electron microscope photograph of Sample No. 1 (after crushing) described in Tables 2 and 3. Figure 4 This is an electron microscope photograph of Sample No. 2 (before pulverization) described in Tables 2 and 3. Figure 5 This is an electron microscope photograph of Sample No. 2 (after crushing) listed in Tables 2 and 3. Figures 2 to 5 It is found that the grain size of Samples No. 1 and 2 before pulverization was approximately 10 μm, and that pulverization reduced the grain size of Samples No. 1 and 2 to a smaller size. Furthermore, it is found that Samples No. 1 and 2 contain substantially no microcracks at the grain boundaries between the grains.

[0115] Table 3 shows that despite having small particle sizes, Samples No. 1 and 2 exhibit negative expansion. Therefore, the composite powder materials used in Samples No. 1 and 2 have low coefficients of thermal expansion, making it possible to easily match the thermal expansion coefficient of the sealed object even with a small seal thickness. On the other hand, Sample No. 3 exhibits positive expansion. Therefore, the composite powder material used in Sample No. 3 exhibits high coefficients of thermal expansion, making it difficult to match the thermal expansion coefficient of the sealed object with a small seal thickness.

[0116] It is considered that the effects shown in Nos. 1 and 2 above can also be confirmed in combination with the Bi2O3-based glass shown in Table 4.

[0117] [Table 4]

[0118]

[0119] Explanation of symbols

[0120] 1…hermetic sealing body

[0121] 10…package base

[0122] 11…Glass cover

[0123] 12…base

[0124] 13…Frame

[0125] 14…Internal components

[0126] 15…Sealing layer

[0127] L…Laser

Claims

1. A composite powder material, characterized in that: In the composite powder material containing glass powder and ceramic powder, The glass powder contains Bi2O3 32.6% to 60%, B2O3 15% to 37%, ZnO 1% to 30%, and CuO 5% to 30% as a glass composition in terms of mol%. The ceramic powder precipitates a β-eucryptite or β-quartz solid solution as a main crystalline phase, contains TiO2 and / or ZrO2 as a composition, and the TiO2 and / or ZrO2 are solid-dissolved in the main crystal. The ceramic powder does not substantially contain a glass phase. The thermal expansion coefficient of ceramic powder at 30℃~300℃ is -20×10 -7 / ℃ and above -1×10 -7 / ℃ below.

2. The composite powder material according to claim 1, wherein The ceramic powder contains, in mol%, 16% to 30% of Li2O, 10% to 35% of Al2O3, and 30% to 68% of SiO2.

3. The composite powder material according to claim 1 or 2, characterized in that: Used for sealing.

4. The composite powder material according to claim 1 or 2, characterized in that: For laser sealing.

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