TWI762584B - Bismuth-based glass powder, sealing material, and hermetic package - Google Patents

Abstract

The technical subject of the present invention is to create a bismuth-based glass that is difficult to generate soft errors in internal elements in a hermetically sealed package. In order to solve this problem, the bismuth-based glass powder of the present invention is characterized in that the α-ray emission rate is 0.15 cph/cm ² or less.

Description

Bismuth-based glass powder, sealing material, and hermetic package

The present invention relates to a bismuth-based glass powder, a sealing material, and a hermetically sealed package, and specifically, to a bismuth-based glass powder with a low alpha ray emission rate, a sealing material, and a hermetically sealed package.

A hermetically sealed package generally includes a package body, a light-transmitting glass cover, and internal elements housed in these.

Internal elements such as sensor elements mounted inside the hermetically sealed package may be degraded by moisture infiltrating from the surrounding environment. Heretofore, an organic resin-based adhesive having low-temperature curability has been used in order to integrate the package base and the glass cover. However, since the organic resin-based adhesive cannot completely shield moisture and gas, there is a possibility of deteriorating internal elements with time.

On the other hand, when a sealing material containing bismuth-based glass powder and refractory filler powder is used, the sealing portion is less likely to be deteriorated by moisture in the surrounding environment, and it is easy to ensure the airtight reliability of the airtight package.

However, since the softening temperature of the bismuth-based glass powder is higher than that of the organic resin-based adhesive, there is a possibility of thermal degradation of the internal elements during sealing. In this context, laser sealing has received attention in recent years. According to the laser sealing, only the portion to be sealed can be locally heated, and the package body and the glass cover can be airtightly integrated without thermally deteriorating the internal elements. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2013-239609 [Patent Document 2] Japanese Patent Laid-Open No. 2014-236202

THE PROBLEM TO BE SOLVED BY THE INVENTION However, when a hermetic package is produced by laser-sealing a glass cover and a package base using a sealing material containing bismuth-based glass powder, the obtained hermetic package may be obtained. Internal components inside the body malfunction due to soft errors, resulting in a decrease in reliability of the hermetic package.

Therefore, the present invention has been made in view of the above-mentioned circumstances, and its technical subject is to create a bismuth-based glass that is difficult to generate soft errors in internal elements in a hermetic package.

[MEANS TO SOLVE THE PROBLEM] The present inventors discovered that the said technical subject can be solved by reducing the alpha-ray emission rate of a bismuth-type glass powder, and proposes as this invention. That is, the bismuth-based glass powder of the present invention is characterized in that the α-ray emission rate is 0.15 cph/cm ² or less. Here, "bismuth-based glass powder" refers to glass powder mainly composed of Bi ₂ O ₃ , and specifically refers to glass powder in which the content of Bi ₂ O ₃ in the glass composition is 25 mol % or more. The "α-ray emission rate" can be measured by a commercially available scintillation counter.

The bismuth-based glass powder of the present invention is characterized in that the α-ray emission rate is 0.15 cph/cm ² or less. The cause of the soft error of the internal element is the ionization of alpha rays emitted from the bismuth-based glass. Furthermore, when the α-ray emission rate of the bismuth-based glass is reduced to 0.15 cph/cm ² or less, soft errors in internal elements can be prevented. In addition, the α-ray emission rate of the conventional bismuth-based glass powder is about 0.30 cph/cm ² to 5.00 cph/cm ² .

The α-ray emission rate of the bismuth-based glass powder is related to the α-ray emission rate in the glass raw material. That is, when the α-ray emission rate of the glass raw material is lowered, the α-ray emission rate of the bismuth-based glass powder can be easily reduced to 0.15 cph/cm ² or less. In particular, the introduction material of Bi ₂ O ₃ tends to have a higher α-ray emission rate than other glass raw materials, so it is extremely effective to reduce the α-ray emission rate of the Bi ₂ O ₃ introduction material. Furthermore, if the glass raw material (especially bismuth oxide) is repeatedly refined, the content of radioisotope elements (U, Th, etc.) in the glass raw material decreases, and the α-ray emission rate of the glass raw material can be reduced.

Second, the sealing material of the present invention is characterized in that it contains 40 to 100% by volume of bismuth-based glass powder, 0 to 60% by volume of refractory filler powder, and has an alpha ray emission rate of 0.15 cph/cm ² or less. . Compared with other glass-based glasses, bismuth-based glass has the advantage that it is easy to form a reaction layer on the surface layer of the package substrate (especially the ceramic substrate) during laser sealing. In addition, the refractory filler powder can improve the mechanical strength of the sealing material layer, and can reduce the thermal expansion coefficient of the sealing material layer.

Third, the hermetic package of the present invention is preferably a hermetic package formed by air-tight sealing between the package body and the glass cover via a sealing material layer, the sealing material layer being a sintered body of the sealing material, and the sealing material layer being a sintered body of the sealing material. The sealing material is the sealing material.

Fourth, in the hermetic package of the present invention, it is preferable that the α-ray emission amount of the sealing material layer inside the hermetic package is less than 1/7 of the α-ray emission amount of the glass cover inside the hermetic package. Here, the "α-ray emission amount of the sealing material layer inside the hermetic package" is calculated by multiplying the surface area of the sealing material layer exposed from the side where the internal elements are arranged by the α-ray emission rate of the sealing material layer value of . The "α-ray emission amount of the glass cover inside the hermetic package" is a value calculated by multiplying the surface area of the glass cover exposed from the side where the internal elements are arranged by the α-ray emission rate of the glass cover.

Fifth, in the hermetic package of the present invention, the average thickness of the sealing material layer is preferably less than 8.0 μm. In this case, it is difficult to generate soft errors in internal elements.

Sixthly, in the hermetic package of the present invention, preferably, the package base has a base portion and a frame portion provided on the base portion. For the internal components, a sealing material layer is arranged between the top of the frame portion of the package body and the glass cover. In this way, internal elements such as sensor elements can be easily accommodated in the frame portion.

Seventh, the hermetic package of the present invention is preferably any one of glass, glass ceramics, aluminum nitride, aluminum oxide, or a composite material of these as the package body matrix.

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view for explaining an embodiment of the present invention. As can be seen from FIG. 1 , the hermetic package 1 includes a package base 10 and a glass cover 11 . In addition, the package body 10 has a base portion 12 and a frame-shaped frame portion 13 on the outer peripheral edge of the base portion 12 . Furthermore, an internal element (for example, a sensor element) 14 is accommodated in the frame portion 13 of the package base 10 . Furthermore, electrical wirings (not shown) that electrically connect the internal elements (eg, sensor elements) 14 to the outside are formed in the package body 10 .

The α-ray emission rate of the sealing material layer 15 is 0.15 cph/cm ² or less, and the sealing material layer 15 extends over the frame portion 13 between the top of the frame portion 13 of the package base 10 and the surface of the glass cover 11 on the inner element 14 side. The perimeter of the top is equipped. In addition, the sealing material layer 15 contains a bismuth-based glass and a refractory filler powder with an α-ray emission rate of 0.15 cph/cm ² or less, but does not substantially contain a laser absorbing material. Furthermore, the width of the sealing material layer 15 is smaller than the width of the top of the frame portion 13 of the package body 10 , and is further separated from the edge of the glass cover 11 . Furthermore, the average thickness of the sealing material layer 15 is less than 8.0 μm.

In addition, the airtight package 1 can be produced as follows. First, the cover glass 11 having the sealing material layer 15 formed in advance is placed on the package base 10 so that the sealing material layer 15 is in contact with the top of the frame portion 13 . Next, while pressing the glass cover 11 using a pressing jig, the laser light L emitted from the laser irradiation device is irradiated along the sealing material layer 15 from the glass cover 11 side. Thereby, the sealing material layer 15 softens and flows, reacts with the surface layer on the top of the frame portion 13 of the package body 10 , and thereby airtightly integrates the package body 10 and the glass cover 11 , thereby forming a hermetic package 1 . Airtight structure.

The α-ray emission rate of the bismuth-based glass powder of the present invention is 0.15 cph/cm ² or less, preferably 0.12 cph/cm ² or less, 0.10 cph/cm ² or less, and 0.01 cph/cm ² to 0.08 cph/cm ² . When the α-ray emission rate of the bismuth-based glass powder is too high, soft errors in internal elements are likely to occur. Furthermore, when the α-ray emission rate of the bismuth-based glass powder is too low, a highly refined glass raw material is required, and the raw material cost of the bismuth-based glass powder tends to increase.

The bismuth-based glass powder preferably contains 28% to 60% of Bi ₂ O ₃ , 15% to 37% of B ₂ O ₃ , and 1% to 30% of ZnO as a glass composition in mol %. The reason for limiting the content range of each component as described above will be described below. In addition, in the description of the glass composition range, the representation of % means mole %.

Bi ₂ O ₃ is a main component for lowering the softening point. The content of Bi ₂ O ₃ is preferably 28% to 60%, 33% to 55%, especially 35% to 45%. When the content of Bi ₂ O ₃ is too small, the softening point is too high, and the softening fluidity tends to decrease. On the other hand, when the content of Bi ₂ O ₃ is too large, the glass tends to devitrify at the time of laser sealing, and the softening fluidity tends to decrease due to the devitrification.

B ₂ O ₃ is an essential component as a glass-forming component. The content of B ₂ O ₃ is preferably 15% to 37%, 19% to 33%, especially 22% to 30%. When the content of B ₂ O ₃ is too small, it becomes difficult to form a glass network, and thus the glass tends to devitrify at the time of laser sealing. On the other hand, when the content of B ₂ O ₃ is too large, the viscosity of the glass increases, and the softening fluidity tends to decrease.

ZnO is a component which improves devitrification resistance. The content of ZnO is preferably 1% to 30%, 3% to 25%, 5% to 22%, especially 5% to 20%. When the content of ZnO is outside the above-mentioned range, the component balance of the glass composition collapses, and the devitrification resistance tends to decrease on the contrary.

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

SiO ₂ is a component that improves water resistance. The content of SiO ₂ is preferably 0% to 5%, 0% to 3%, 0% to 2%, especially 0% to 1%. When the content of SiO ₂ is too large, the softening point may increase unreasonably. In addition, the glass tends to devitrify at the time of laser sealing.

Al ₂ O ₃ is a component that improves water resistance. The content of Al ₂ O ₃ is preferably 0% to 10%, 0.1% to 5%, particularly 0.5% to 3%. When the content of Al ₂ O ₃ is too large, the softening point may increase unreasonably.

Li ₂ O, Na ₂ O, and K ₂ O are components that reduce devitrification resistance. Therefore, the content of Li ₂ O, Na ₂ O and K ₂ O is preferably 0% to 5%, 0% to 3%, particularly 0% to less than 1%, respectively.

MgO, CaO, SrO, and BaO are components that improve the devitrification resistance, but are components that increase the softening point. Therefore, the content of MgO, CaO, SrO and BaO is preferably 0% to 20%, 0% to 10%, particularly 0% to 5%, respectively.

In order to lower the softening point of bismuth-based glass, it is necessary to introduce a large amount of Bi ₂ O ₃ into the glass composition. However, if the content of Bi ₂ O ₃ is increased, the glass tends to devitrify during laser sealing. As a result, the softening fluidity becomes easy to decrease. In particular, this tendency becomes remarkable when the content of Bi ₂ O ₃ is 30% or more. As a countermeasure for this, if CuO is added, even if the content of Bi ₂ O ₃ is 30% or more, the decrease in devitrification resistance can be effectively suppressed. When CuO is further added, the laser absorption characteristics at the time of laser sealing can be improved. The content of CuO is preferably 0% to 40%, 1% to 40%, 5% to 35%, 10% to 30%, especially 13% to 25%. When the content of CuO is too large, the component balance of the glass composition is impaired, and the devitrification resistance tends to decrease on the contrary. In addition, the total light transmittance of the sealing material layer is too low, and it is difficult to locally heat the boundary region between the package body and the sealing material layer.

Fe ₂ O ₃ is a component that improves devitrification resistance and laser absorption properties. The content of Fe ₂ O ₃ is preferably 0% to 10%, 0.1% to 5%, particularly 0.4% to 2%. When the content of Fe ₂ O ₃ is too large, the component balance of the glass composition is collapsed, and the devitrification resistance tends to decrease on the contrary.

MnO is a component that improves laser absorption characteristics. The content of MnO is preferably 0% to 25%, particularly 5% to 15%. When the content of MnO is too large, the devitrification resistance tends to decrease.

Sb ₂ O ₃ is a component that improves devitrification resistance. The content of Sb ₂ O ₃ is preferably 0% to 5%, particularly 0% to 2%. When the content of Sb ₂ O ₃ is too large, the component balance of the glass composition is collapsed, and the devitrification resistance tends to decrease on the contrary.

The average particle diameter _D50 of the bismuth-based glass powder is preferably less than 15 μm, 0.5 μm to 10 μm, particularly 1 μm to 5 μm. The smaller the average particle diameter _D50 of the bismuth-based glass powder, the lower the softening point of the bismuth-based glass powder. Here, the "average particle diameter D ₅₀ " refers to a value measured on a volume basis by a laser diffraction method.

The sealing material of the present invention contains 40% to 100% by volume of bismuth-based glass powder, 0% to 60% by volume of refractory filler powder, preferably 55% to 95% by volume of bismuth-based glass powder, 5 The refractory filler powder in volume % to 45 volume %, more preferably bismuth-based glass powder in 60 volume % to 85 volume %, and refractory filler powder in 15 volume % to 40 volume %, particularly preferably 60 volume % to 60 volume %. 80% by volume of bismuth-based glass powder, 20% by volume to 40% by volume of refractory filler powder. The bismuth-based glass powder is a component that softens and deforms during laser sealing to airtightly integrate the package body and the glass cover. The refractory filler powder acts as an aggregate to lower the thermal expansion coefficient of the sealing material and increase the mechanical strength. However, when the content of the refractory filler powder is too large, the content of the glass powder is relatively small, so that the surface smoothness of the sealing material layer is lowered, and the precision of the laser sealing tends to be lowered. Furthermore, in addition to the glass powder and the refractory filler powder, the sealing material layer may also contain a laser absorbing material to improve light absorption properties.

In the sealing material of the present invention, the α-ray emission rate is 0.15 cph/cm ² or less, preferably 0.12 cph/cm ² or less, 0.10 cph/cm ² or less, and 0.01 cph/cm ² to 0.08 cph/cm ² . If the α-ray emission rate of the sealing material is too high, soft errors of internal elements are likely to occur. Furthermore, when the α-ray emission rate of the sealing material is too low, a highly refined glass raw material is required, and the raw material cost of the sealing material tends to increase.

The softening point of the sealing material is preferably 510°C or lower, 480°C or lower, particularly 450°C or lower. When the softening point of the sealing material is too high, it is difficult to improve the surface smoothness of the sealing material layer. The lower limit of the softening point of the sealing material is not particularly set, but when the thermal stability of the glass powder is considered, the softening point of the sealing material is preferably 350° C. or higher. Here, the "softening point" is the fourth inflection point when measured by a large-scale DTA apparatus, and corresponds to Ts in FIG. 2 .

The refractory filler powder is preferably one or more selected from the group consisting of cordierite, tin oxide, niobium oxide, willemite, β-eucryptite, and β-quartz solid solution, particularly preferably β-eucryptite or cordierite. These refractory filler powders have high mechanical strength, in addition to low α-ray emission rate and thermal expansion coefficient, and good compatibility with bismuth-based glass.

The average particle diameter _D50 of the refractory filler powder is preferably less than 2 μm, particularly 0.1 μm or more and less than 1.5 μm. When the average particle diameter _D50 of the refractory filler powder is too large, the surface smoothness of the sealing material layer is likely to decrease, and the average thickness of the sealing material layer is likely to increase. As a result, the precision of the laser sealing is likely to decrease.

The 99% particle diameter D ₉₉ of the refractory filler powder is preferably less than 5 μm and 4 μm or less, particularly 0.3 μm or more and 3 μm or less. When the 99% particle size D ₉₉ of the refractory filler powder is too large, the surface smoothness of the sealing material layer tends to decrease, and the average thickness of the sealing material layer tends to increase. As a result, the precision of laser sealing tends to decrease. Here, “99% particle size D ₉₉ ” refers to a value measured on a volume basis by a laser diffraction method.

In order to improve the light absorption characteristics, the sealing material may further include a laser absorbing material, and the laser absorbing material has the effect of promoting the devitrification of the bismuth-based glass. Therefore, the content of the laser absorbing material in the sealing material is preferably 15 vol % or less, 10 vol % or less, 5 vol % or less, 1 vol % or less, 0.5 vol % or less, and especially not substantially contained (0.1 vol % or less). % or less) is appropriate. When the devitrification resistance of the bismuth-based glass is good, in order to improve the laser absorption characteristics, a laser absorbing material may be introduced in an amount of 1 vol % or more, especially 3 vol % or more. In addition, as a laser absorbing material, a Cu-based oxide, an Fe-based oxide, a Cr-based oxide, a Mn-based oxide, a spinel-type composite oxide thereof, or the like can be used.

The thermal expansion coefficient of the sealing material (sealing material layer) is preferably 55×10 ^-7 /°C to 95×10 ^-7 /°C, 60×10 ^-7 /°C to 82×10 ^-7 /°C, particularly 65×10 ^-7 /℃～76× ^10-7 /℃. In this way, the thermal expansion coefficient of the sealing material layer is easily matched with the thermal expansion coefficient of the glass cover or the package base. In addition, "thermal expansion coefficient" is the value measured by the push rod type thermal expansion coefficient measurement (TMA) apparatus in the temperature range of 30 degreeC - 300 degreeC.

The hermetic package of the present invention is characterized in that: in the hermetic package formed by airtight sealing between the package body and the glass cover via a sealing material layer, the sealing material layer is a sintered body of the sealing material, and the sealing material for the sealing material. Hereinafter, the airtight package of the present invention will be described in detail.

In the hermetic package of the present invention, the package base preferably has a base portion and a frame portion provided on the base portion. In this way, internal elements such as sensor elements can be easily accommodated in the frame portion of the package base. The frame portion of the package body is preferably formed in a frame shape along the outer edge region of the package body. In this way, the effective area functioning as a device can be enlarged. In addition, internal elements such as sensor elements can be easily accommodated in the frame portion of the package base body, and wire bonding and the like can also be easily performed.

It is preferable that the surface roughness Ra of the surface of the area|region in which the sealing material layer is arrange|positioned in the top part of a frame part is less than 1.0 micrometer. When the surface roughness Ra of this surface becomes large, the precision of laser sealing becomes easy to fall. Here, "surface roughness Ra" can be measured by, for example, a stylus type or non-contact type laser film thickness meter or a surface roughness meter.

The width of the top portion of the frame portion is preferably 100 μm to 3000 μm, 200 μm to 1500 μm, particularly 300 μm to 900 μm. When the width of the top portion of the frame portion is too narrow, it will be difficult to align the sealing material layer with the top portion of the frame portion. On the other hand, if the width of the top portion of the frame portion is too wide, the effective area functioning as a device becomes small.

The package body is preferably any one of glass, glass ceramics, aluminum nitride, and aluminum oxide, or a composite material thereof (for example, one obtained by integrating aluminum nitride and glass ceramics). Glass is easy to form a sealing material layer and a reaction layer, so a firm sealing strength can be ensured by laser sealing. Furthermore, since the thermal via hole can be easily formed, a situation in which the temperature of the hermetic package is excessively increased can be appropriately prevented. Since aluminum nitride and aluminum oxide have good heat dissipation properties, it is possible to appropriately prevent a situation in which the temperature of the hermetic package rises excessively.

Glass ceramics, aluminum nitride, and alumina are preferably dispersed with a black pigment (sintered in a state in which the black pigment is dispersed). If so, the package body can absorb the laser light transmitted through the sealing material layer. As a result, the portion of the package base in contact with the sealing material layer is heated during laser sealing, so that the formation of the reaction layer can be promoted at the interface between the sealing material layer and the package base.

The package matrix in which the black pigment is dispersed preferably has the property of absorbing the laser light to be irradiated, that is, the thickness is preferably 0.5 mm, and the total light transmittance of the wavelength of the laser light to be irradiated (808 nm) is 10% or less ( Ideally below 5%). In this way, the temperature of the sealing material layer at the interface between the package base and the sealing material layer is likely to rise.

The thickness of the base of the package body is preferably 0.1 mm to 2.5 mm, particularly 0.2 mm to 1.5 mm. Thereby, thinning of the hermetic package can be achieved.

The height of the frame portion of the package base body, that is, the height of the package base body minus the thickness of the base portion is preferably 100 μm to 2000 μm, particularly 200 μm to 900 μm. In this way, the internal components can be appropriately accommodated, and the thinning of the airtight package can be easily achieved.

Various types of glass can be used for the glass cover. For example, alkali-free glass, alkali borosilicate glass, soda lime glass can be used. Furthermore, the glass cover may also be a laminated glass formed by laminating a plurality of glass plates.

A functional film may be formed on the surface of the inner element side of the glass cover, or a functional film may be formed on the outer surface of the glass cover. The functional film is particularly preferably an antireflection film. Thereby, the light reflected on the surface of the glass cover can be reduced.

The thickness of the glass cover is preferably 0.1 mm or more, 0.15 mm to 2.0 mm, particularly 0.2 mm to 1.0 mm. When the thickness of the cover glass is small, the strength of the airtight package tends to decrease. On the other hand, when the thickness of the cover glass is large, it is difficult to reduce the thickness of the hermetic package.

The sealing material layer has the function of softening and deforming by absorbing the laser light, forming a reaction layer on the surface layer of the package base body, and airtightly integrating the package body base body and the glass cover.

The α-ray emission amount of the sealing material layer inside the hermetic package is preferably less than 1/7 of the α-ray emission amount of the glass cover inside the hermetic package, and more preferably 1/10 or less. If the α-ray emission amount of the sealing material layer inside the hermetic package is too large compared with the α-ray emission amount of the glass cover inside the hermetic package, soft errors of internal elements are likely to occur.

The difference in thermal expansion coefficient between the glass cover and the sealing material layer is preferably less than 50×10 ^-7 /°C, less than 40×10 ^-7 /°C, and particularly 30×10 ^-7 /°C or less. When the thermal expansion coefficient difference is too large, the stress remaining in the sealing portion becomes unreasonably high, and the airtight reliability of the airtight package tends to decrease.

The sealing material layer is preferably formed in such a manner that the contact position with the frame portion is spaced apart from the inner edge of the top of the frame portion, and is formed in such a manner as to be spaced apart from the outer edge of the top portion of the frame portion, and is further preferably formed on the outer edge of the top portion of the frame portion. The inner edge of the top of the portion is separated from positions of 50 μm or more, 60 μm or more, 70 μm to 2000 μm, especially 80 μm to 1000 μm. If the distance between the inner edge of the top of the frame and the sealing material layer is too short, the heat generated by local heating during laser sealing is difficult to escape, so the glass cover is easily damaged during cooling. On the other hand, when the distance between the inner edge of the top portion of the frame portion and the sealing material layer is too long, it becomes difficult to reduce the size of the airtight package. In addition, it is preferably formed at a position separated from the outer edge of the top of the frame portion by 50 μm or more, 60 μm or more, 70 μm to 2000 μm, particularly 80 μm to 1000 μm. If the distance between the outer edge of the top of the frame and the sealing material layer is too short, the heat generated by local heating during laser sealing is difficult to escape, so the glass cover is easily damaged during cooling. On the other hand, if the distance between the outer edge of the top portion of the frame portion and the sealing material layer is too long, it will be difficult to reduce the size of the hermetic package.

The sealing material layer is preferably formed so that the contact position with the glass cover is separated from the edge of the glass cover by 50 μm or more, 60 μm or more, 70 μm to 1500 μm, especially 80 μm to 800 μm. If the distance between the edge of the glass cover and the sealing material layer is too short, during laser sealing, the surface temperature difference between the surface of the inner element side and the outer surface of the glass cover in the edge area of the glass cover will increase, and the glass cover will Easily damaged.

The sealing material layer is preferably formed on the center line of the top portion of the frame portion in the width direction, that is, formed in the central region of the top portion of the frame portion. In this case, the heat generated by local heating during laser sealing is easy to escape, so that the glass cover is not easily damaged. Furthermore, when 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 in the width direction of the top portion of the frame portion.

The average thickness of the sealing material layer is preferably less than 8.0 μm, particularly 1.0 μm or more and less than 6.0 μm. The smaller the average thickness of the sealing material layer, the smaller the α-ray emission rate in the hermetic package, and therefore, it is easy to prevent soft errors of internal elements. The smaller the average thickness of the sealing material layer, the more accurate the laser sealing is. Furthermore, when the thermal expansion coefficients of the sealing material layer and the glass cover do not match, the stress remaining in the sealing portion can also be reduced after laser sealing. In addition, as a method of restricting the average thickness of the sealing material layer as described above, a method of applying a thin sealing material paste and a method of polishing the surface of the sealing material layer can be mentioned.

The maximum width of the sealing material layer is preferably 1 μm or more and 2000 μm or less, 10 μm or more and 1000 μm or less, 50 μm or more and 800 μm or less, particularly 100 μm or more and 600 μm or less. When the maximum width of the sealing material layer is narrowed, the sealing material layer can be easily separated from the edge of the frame portion, so that the stress remaining in the sealing portion after the laser sealing is easily reduced. Furthermore, the width of the frame portion of the package body can be narrowed, and the effective area functioning as a device can be enlarged. On the other hand, if the maximum width of the sealing material layer is too narrow, when a large shear stress is applied to the sealing material layer, the sealing material layer is likely to be broken in its entirety. Furthermore, the precision of laser sealing becomes easy to fall.

The sealing material layer can be formed by various methods, and among them, coating and baking of a sealing material paste are preferable. In addition, it is preferable to use a dispenser or a coater such as a screen printing machine for the coating of the sealing material paste. In this way, the dimensional accuracy of the sealing material layer (the dimensional accuracy of the width of the sealing material layer) can be improved. Here, the sealing material paste is a mixture of a sealing material and a vehicle. Also, the vehicle typically includes a solvent and a resin. The resin is added for the purpose of adjusting the viscosity of the paste. In addition, a surfactant, a tackifier, etc. may be added as necessary.

The sealing material paste is usually produced by kneading the sealing material and the vehicle with three rolls or the like. The vehicle usually contains a resin and a solvent. As the resin used for the vehicle, acrylate (acrylic resin), ethyl cellulose, polyethylene glycol derivatives, nitrocellulose, polymethyl styrene, polyethylene carbonate, polypropylene carbonate can be used Diesters, methacrylates, etc. As the solvent used in the vehicle, N,N'-dimethylformamide (N,N'-dimethylformamide, DMF), α-terpineol, higher alcohol, γ-butyl lactone ( γ-BL), tetralin (tetralin), butyl carbitol acetate, ethyl acetate, isoamyl acetate, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, benzyl alcohol, Toluene, 3-methoxy-3-methylbutanol, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monomethyl ether Propylene glycol monobutyl ether, propylene carbonate, dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone, etc.

The sealing material paste can also be applied on the top of the frame portion of the package body, preferably in a frame shape along the outer peripheral edge region of the glass cover. In this way, firing of the sealing material layer for the package base body is not required, and thermal degradation of internal elements such as sensor elements can be suppressed.

As a method of manufacturing the hermetically sealed package of the present invention, it is preferable to irradiate the sealing material layer with laser light from the glass cover side to soften and deform the sealing material layer, thereby airtightly sealing the package body and the glass cover to obtain a gaseous seal. Sealed body. In this case, the glass cover may be arranged below the package base, but from the viewpoint of the efficiency of laser sealing, the glass cover is preferably arranged above the package base.

As the laser, various lasers can be used. In terms of ease of operation, the best ones are semiconductor lasers, Yttrium-Aluminum-Garnet (YAG) lasers, CO ₂ lasers, excimer lasers, and infrared lasers.

The environment in which the laser sealing is performed is not particularly limited, and may be an atmospheric environment or an inert environment such as a nitrogen environment.

Preferably, the laser sealing is performed in a state where the glass cover is pressed. Thereby, it becomes easy to improve the laser sealing strength. [Example]

Hereinafter, the present invention will be described in detail based on examples. In addition, the following Examples are only an illustration. The present invention is not limited at all by the following examples.

Table 1 shows the Examples (Sample No. 1 to Sample No. 3) and Comparative Examples (Sample No. 4 to Sample No. 6) of the present invention.

[Table 1]

Initially, 39% Bi ₂ O ₃ , 23.7% B ₂ O ₃ , 14.1% ZnO, 2.7% Al ₂ O ₃ , 20% CuO, 0.6% Fe ₂ O were prepared in molar %. ₃ As a form of glass composition, glass batches prepared with raw materials such as various oxides and carbonates were prepared, put into a platinum crucible, and melted at 1200° C. for 2 hours. Next, the obtained molten glass is formed into a sheet shape by a water-cooled roll. Finally, the flaky bismuth-based glass was pulverized by a ball mill, and air-classified to obtain bismuth-based glass powder. In addition, the bismuth-based glass powder used for Sample No. 1 to Sample No. 3 and the bismuth-based glass powder used for Sample No. 4 to Sample No. 6 have the same glass composition and particle size, but the α-ray The emission rate is different, and the α-ray emission rate can be adjusted by changing the type of glass raw material.

Next, the bismuth-based glass powder was mixed in a ratio of 90.0 mass % and the refractory filler powder was 10.0 mass % to prepare a sealing material. Here, the average particle diameter D ₅₀ of the bismuth-based glass powder was 1.0 μm, the 99% particle diameter D ₉₉ was 2.5 μm, the average particle diameter D ₅₀ of the refractory filler powder was 1.0 μm, and the 99% particle diameter D 50 was 1.0 μm. The particle size D _{99 was} set to 2.5 μm. In addition, the refractory filler powder is β-eucryptite.

The thermal expansion coefficient of the obtained sealing material was measured, and as a result, the thermal expansion coefficient was 71×10 ^-7 /°C. In addition, the thermal expansion coefficient was measured by a push rod type TMA apparatus, and the measurement temperature range was 30 degreeC - 300 degreeC.

Next, a frame-shaped sealing material layer was formed using the sealing material along the outer peripheral edge of a glass cover (thickness 0.4 mm, alpha ray emission rate 0.003 cph/cm ² ) containing borosilicate glass. To describe in detail, firstly, after kneading the above-mentioned sealing material, vehicle and solvent so that the viscosity becomes about 100 Pa·s (25°C, Shear rate: 4), the three-roller The grinder performs mixing until the powder is uniformly dispersed, and pastes it to obtain a sealing material paste. As the vehicle, one in which ethyl cellulose resin was dissolved in a glycol ether solvent was used. Next, along the outer peripheral edge of the glass cover, the sealing material paste is printed in a frame shape using a screen printing machine. Furthermore, after drying at 120° C. for 10 minutes in an atmospheric environment, the sealing material layer was formed on the cover glass by firing at 500° C. for 10 minutes in an atmospheric environment.

The inner circumference size and thickness of the sealing material layer are as shown in Table 1, and the average width of the sealing material layer is 0.2 mm.

In addition, a package base (thickness 0.8 mm) containing aluminum oxide was prepared. The package body has the same vertical and lateral dimensions as the glass cover, and the surface roughness Ra of the package body is 0.1 μm to 1.0 μm.

Finally, the package body and the glass cover are laminated and arranged with the sealing material layer interposed therebetween. Then, using a pressing jig, while pressing the glass cover, irradiate a semiconductor laser with a wavelength of 808 nm, an output of 4 W, and an irradiation diameter f of 0.5 mm from the side of the glass cover to the sealing material layer at an irradiation speed of 15 mm/sec. By softening and deforming, the package body and the glass cover were airtightly integrated to obtain the airtight packages of Sample No. 1 to Sample No. 6.

The α-ray emission rate of the sealing material layer and the cover glass is a value measured by a scintillation counter. In addition, in Sample No. 1 to Sample No. 6, the α-ray emission rate of the refractory filler powder in the sealing material layer was significantly smaller than that of the bismuth-based glass. Therefore, in Sample No. 1 to Sample No. 6, the α-ray emission rate of the sealing material layer is considered to be approximately equal to the α-ray emission rate of the bismuth-based glass powder.

The α-ray emission amount of the inner sealing material layer is a value calculated by multiplying the surface area of the sealing material layer exposed from the side where the internal elements are arranged by the α-ray emission rate of the sealing material layer. The α-ray emission amount of the glass cover inside is a value calculated by multiplying the surface area of the glass cover exposed from the side where the internal elements are arranged by the α-ray emission rate of the glass cover.

The cracks and airtight reliability after laser sealing were evaluated for Sample No. 1 to Sample No. 6. First, the sealing portion was observed with an optical microscope, and as a result, the occurrence of cracks was not confirmed. Next, the obtained hermetic package was subjected to a high temperature, high humidity and high pressure test: HAST test (Highly Accelerated Temperature and Humidity Stress test), and the vicinity of the sealing material layer was observed. As a result, no deterioration, cracking, peeling, or the like was confirmed at all. In addition, the conditions of the HAST test were 121 degreeC, 100% of humidity, 2 atm, 24 hours.

As is clear from Table 1, since the α-ray emission rates of the sealing material layers of Sample No. 1 to Sample No. 3 are low, it is considered that soft errors in internal elements are unlikely to occur. On the other hand, since the α-ray emission rates of the sealing material layers of Sample No. 4 to Sample No. 6 are high, it is considered that a soft error of the internal element is likely to occur. [Industrial Availability]

The bismuth-based glass and the sealing material of the present invention are suitable for sealing various materials, and are particularly suitable for laser sealing of a hermetic package. In addition, the hermetic package of the present invention is suitable for a hermetically sealed package in which internal elements such as sensor elements are mounted, and is also suitable for housing deep ultraviolet LED elements, piezoelectric vibrating elements, and resins. In a hermetic package or the like of a wavelength conversion element in which quantum dots are dispersed.

1‧‧‧Hermetically sealed package body 10‧‧‧Package body base body 11‧‧‧Glass cover 12‧‧‧Base part 13‧‧‧Frame part 14‧‧‧Internal components (eg, sensor components) 15‧‧‧ Sealing material layer L‧‧‧Laser light Ts‧‧‧softening point

FIG. 1 is a schematic cross-sectional view for explaining an embodiment of the present invention. FIG. 2 is a schematic diagram showing the softening point of the sealing material when measured by a large-scale differential thermal analysis (DTA) apparatus.

1‧‧‧Hermetically sealed package

10‧‧‧Package body

11‧‧‧Glass cover

12‧‧‧Base

13‧‧‧Frame

14‧‧‧Internal components (eg sensor components)

15‧‧‧Sealing material layer

L‧‧‧laser light

Claims (7)

A bismuth-based glass powder is characterized in that: the glass composition contains 1 mol % to 40 mol % of CuO, and the alpha ray emission rate is 0.01 cph/cm ² to 0.15 cph/cm ² . A sealing material, characterized in that it contains 40% to 100% by volume of bismuth-based glass powder, 0% to 60% by volume of refractory filler powder, and an alpha ray emission rate of 0.01cph/cm ² to 0.15cph/cm ^2. The glass composition contains 1 mol% to 40 mol% of CuO. An airtight package body is formed by airtightly sealing a package body base body and a glass cover through a sealing material layer. The airtight package body is characterized in that: the sealing material layer is a sintered body of the sealing material, so The sealing material is the sealing material described in claim 2 of the scope of the application. The hermetic package according to claim 3, wherein the alpha ray emission amount of the sealing material layer inside the hermetic package is less than alpha of the glass cover inside the hermetic package 1/7 of the ray output. The hermetic package according to claim 3 or claim 4, wherein the sealing material layer has an average thickness of 1.0 μm to less than 8.0 μm. The hermetic package according to claim 3 or 4, wherein the package base has a base portion and a frame portion provided on the base portion, and is accommodated in the frame portion of the package base There are internal components, and the sealing material layer is disposed between the top of the frame portion of the package body and the glass cover. The hermetic package body according to item 3 or item 4 of the claimed scope, wherein the package body base is any one of glass, glass ceramics, aluminum nitride, aluminum oxide, or a composite material thereof.

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