JP7549802B2 - Protective cap, electronic device, and method for manufacturing protective cap - Google Patents

Description

The present invention relates to a protective cap, an electronic device, and a method for manufacturing the protective cap.

Electronic devices equipped with electronic components such as LEDs are now being used in a variety of fields, including lighting and communications, due to their long life span and energy conservation.

In this type of electronic device, in order to protect the electronic components, a protective cap may be placed over the base material on which the electronic components are mounted so that the electronic components are housed inside.

For example, as disclosed in Patent Document 1, the protective cap has a frame portion (called the second member in the document) that surrounds the electronic component, and a lid portion (called the cover member in the document) that covers one end opening of the frame portion.

International Publication No. 2015/190242

However, quartz glass has the property of being less likely to absorb light with wavelengths in the ultraviolet range. For this reason, when the electronic component is an ultraviolet LED, it is possible to construct both the frame and the lid from quartz glass in order to improve the ultraviolet transmittance of the protective cap.

However, the substrate is often made of metal, metal oxide ceramics, LTCC, or metal nitride ceramics, and is generally a material with a high expansion coefficient. On the other hand, the frame is made of quartz glass, and is therefore a material with a low expansion coefficient. For this reason, for example, when attempting to join the frame to the substrate using brazing material, it is difficult to match the thermal expansion coefficient of the brazing material to the thermal expansion coefficients of the substrate and the frame, because the difference in the expansion coefficients of the substrate and the frame is large. In other words, when the thermal expansion coefficient of the brazing material is matched to the thermal expansion coefficient of the substrate, the difference in the thermal expansion coefficients of the frame and the brazing material becomes large, and when the thermal expansion coefficient of the brazing material is matched to the frame, the difference in the thermal expansion coefficients of the substrate and the brazing material becomes large. As a result, residual stress occurs at or near the joint between the substrate and the frame, making it easier for damage (for example, cracks or other breakages) to occur. When the joint or its vicinity is damaged in this way, the airtightness of the space in which the electronic components are housed decreases, and the electronic components may deteriorate.

The objective of the present invention is to provide a protective cap and electronic device that can maintain high airtightness.

The protective cap according to the present invention, which has been invented to solve the above problems, comprises a frame, a lid covering one end opening of the frame, and a joint joining the frame and the lid, the lid being made of quartz glass, and the frame being made of a glass material having a thermal expansion coefficient of 30×10 ⁻⁷ to 100×10 ⁻⁷ /°C in a temperature range of 30 to 380°C. In this way, even if the lid is made of quartz glass, the thermal expansion coefficient of the frame matches not only the thermal expansion coefficient of the lid but also the thermal expansion coefficient of the base material made of metal, metal oxide ceramics, LTCC, or metal nitride ceramics. As a result, even if the protective cap is joined to the base material using, for example, a brazing material, breakage is unlikely to occur at or near the joint, so that high airtightness can be maintained. Here, "quartz glass" refers to a non-crystalline material containing 90 mass% or more of SiO ₂ , including synthetic quartz, fused quartz, etc. The "thermal expansion coefficient in a temperature range of 30 to 380°C" can be measured, for example, using a commercially available dilatometer.

In the above configuration, it is preferable that the joint is formed by directly welding the frame and the lid. In this way, since no other member such as a brazing material is interposed between the frame and the lid, the frame and the lid can be reliably joined even if the difference between the thermal expansion coefficients of the frame and the lid is relatively large.

In the above configuration, it is preferable that the glass material of the frame has a transmittance of 10% or more at an optical path length of 0.7 mm and a wavelength of 200 nm. In this way, in addition to the lid portion made of quartz glass, which has high ultraviolet transmittance, the frame also has ultraviolet transmittance, so that the protective cap as a whole can achieve high ultraviolet transmittance. Here, the "transmittance at an optical path length of 0.7 mm and a wavelength of 200 nm" may be measured after preparing a measurement sample with a thickness of 0.7 mm, or the transmittance may be measured in the thickness direction of the glass material and then converted to a value for an optical path length of 0.7 mm. The "transmittance at a wavelength of 200 nm" can be measured using a commercially available spectrophotometer (e.g., Hitachi's UV-3100).

In the above configuration, it is preferable that the strain point of the glass material of the frame is 430°C or higher. In this way, for example, when the frame of the protective cap is joined to the base material using a brazing material, it is possible to prevent distortion of the frame due to heating during brazing (reflow). Here, "strain point" refers to a value measured based on the method of ASTM C336.

In the above configuration, it is preferable that the softening point of the glass material of the frame is 1000°C or less. In this way, for example, when the lid and frame are directly welded by laser welding, the frame softens easily, and the bonding time between the lid and frame can be shortened. Here, "softening point" refers to a value measured based on the method of ASTM C338.

In the above configuration, the glass material of the frame _preferably contains, in mass %, 50-80% _SiO2 , 1-45% _Al2O3 +B2O3, 0-25% Li2O+ _Na2O + _K2O , _and 0-25% MgO ₊ CaO+ _SrO + _BaO . Here, " _Al2O3 + _B2O3 " is the total amount of _Al2O3 and _B2O3 . " _MgO +CaO+SrO+BaO" is the total amount of MgO, _CaO , _SrO , and BaO.

In the above configuration, it is preferable that a reflective film is formed on the inner peripheral surface of the frame. In this way, when an electronic device that emits light is manufactured using a protective cap, the light extraction efficiency is improved.

In the above configuration, it is preferable that an anti-reflection film is formed on at least one of the front and back surfaces of the lid. In this way, when an electronic device that emits light is manufactured using a protective cap, the light extraction efficiency is improved.

The electronic device according to the present invention, which was invented to solve the above problems, is characterized by comprising an electronic component, a substrate on which the electronic component is mounted, and a protective cap of the above configuration joined to the substrate so as to house the electronic component inside. In this way, it is possible to enjoy the same effects as the corresponding configuration of the protective cap already described.

In the above configuration, it is preferable that the protective cap and the base material are joined by a brazing material.

In the above configuration, it is preferable that the electronic component is an ultraviolet LED. In this way, it is possible to provide an electronic device (light-emitting device) that can achieve high ultraviolet extraction efficiency.

The manufacturing method of the protective cap according to the present invention, which has been invented to solve the above problems, is characterized by comprising a preparation step of preparing a lid made of quartz glass and a frame made of a glass material having a thermal expansion coefficient of 30×10 ^-7 to 100×10 ^-7 /° C. in the temperature range of 30 to 380° C., and a joining step of directly fusing the lid and the frame by irradiating a laser to the contact portion of the lid and the frame in a state in which the lid is in contact with the frame so as to cover one end opening of the frame. In this way, it is possible to enjoy the same effects as the corresponding configuration of the protective cap already described.

The present invention provides a protective cap and electronic device that can maintain high airtightness.

1 is a cross-sectional view showing an electronic device according to a first embodiment. 2 is a cross-sectional view taken along line AA of FIG. 1. 1 is a graph showing the transmittance curves of BU-41 and quartz glass at wavelengths of 200 to 600 nm. 5A to 5C are cross-sectional views illustrating a manufacturing process of the electronic device according to the first embodiment. 5A to 5C are cross-sectional views illustrating a manufacturing process of the electronic device according to the first embodiment. 5A to 5C are cross-sectional views illustrating a manufacturing process of the electronic device according to the first embodiment. 5A to 5C are cross-sectional views illustrating a manufacturing process of the electronic device according to the first embodiment. FIG. 11 is a cross-sectional view showing an electronic device according to a second embodiment. 7A to 7C are cross-sectional views illustrating a manufacturing process of the electronic device according to the second embodiment. 7A to 7C are cross-sectional views illustrating a manufacturing process of the electronic device according to the second embodiment. 7A to 7C are cross-sectional views illustrating a manufacturing process of the electronic device according to the second embodiment. 10A to 10C are plan views illustrating a manufacturing process of an electronic device according to a second embodiment. FIG. 11 is a cross-sectional view showing a frame portion according to a third embodiment.

Embodiments of the present invention will be described below with reference to the drawings. Note that in each embodiment, corresponding components are given the same reference numerals, and duplicated descriptions may be omitted. When only a portion of a configuration is described in each embodiment, the configuration of another embodiment previously described may be applied to the other portions of the configuration. In addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments may be partially combined together even if not explicitly stated, provided that there is no particular problem with the combination.

First Embodiment
1 and 2 illustrate an electronic device 1 according to a first embodiment of the invention.

The electronic device 1 according to this embodiment includes an electronic component 2, a substrate 3 on which the electronic component 2 is mounted, a protective cap 4 disposed on the substrate 3 so as to house the electronic component 2 therein, and a joint 5 that joins the substrate 3 and the protective cap 4. In the following description, for convenience, the substrate 3 side is described as the bottom and the protective cap 4 side is described as the top, but the up-down direction is not limited to this.

The electronic component 2 is not particularly limited, but examples thereof include optical devices such as a laser module, an LED, an optical sensor, an imaging element, and an optical switch. In this embodiment, the electronic component 2 is an ultraviolet LED (light-emitting element), and the electronic device 1 is a light-emitting device.

The substrate 3 is made of, for example, a metal, a metal oxide ceramic, an LTCC, or a metal nitride ceramic. Examples of metals include copper and metal silicon. Examples of metal oxide ceramics include aluminum oxide. Examples of LTCC include sintered composite powders containing crystalline glass and refractory fillers. Examples of metal nitride ceramics include aluminum nitride. In this embodiment, the substrate 3 is made of aluminum nitride. The thermal expansion coefficient of aluminum nitride in the temperature range of 30 to 380° C. is, for example, 46×10 ⁻⁷ /° C. In this embodiment, the substrate 3 is a plate-shaped body having both an upper surface 3a and a lower surface 3b made of flat surfaces. Note that the substrate 3 may have a recess in the portion of the upper surface 3a on which the electronic component 2 is mounted.

The protective cap 4 includes a frame 6, a lid 7 that covers an opening at one end of the frame 6, and a joint 8 that joins the frame 6 and the lid 7. It is preferable to form various functional films on the surface of the protective cap 4. For example, in order to reduce light reflection loss, it is preferable to form an anti-reflection film on at least one of the upper and lower surfaces 7a and 7b of the lid 7. The anti-reflection film is preferably formed on each of the upper and lower surfaces 7a and 7b of the lid 7. The anti-reflection film may be formed only on the portion corresponding to the through hole H of the frame 6 of at least one of the upper and lower surfaces 7a and 7b of the lid 7, or may be formed on the entire surface. As the anti-reflection film, for example, a dielectric multilayer film in which a low refractive index layer with a relatively low refractive index and a high refractive index layer with a relatively high refractive index are alternately stacked is preferable. This makes it easier to control the reflectance at each wavelength. The anti-reflection film can be formed by, for example, a sputtering method or a CVD method. The reflectance of the anti-reflection film in the wavelength band of the light emitted from the electronic component 2 (e.g., 250 to 350 nm) is preferably, for example, 1% or less, 0.5% or less, 0.3% or less, and particularly preferably 0.1% or less.

The frame 6 is a cylindrical body having a through hole H extending in the thickness direction (vertical direction) at the center. The frame 6 surrounds the electronic component 2 housed in the space corresponding to the through hole H. In the illustrated example, the frame 6 is configured as a square tube, but may have other shapes such as a cylinder. The inner wall surface 6c of the frame 6 is configured as an inclined surface that transitions from the inside to the outside as it moves from the lower end surface 6b side of the frame 6 to the upper end surface 6a side, in order to improve the efficiency of extracting ultraviolet rays through the lid 7. The inner wall surface 6c may be a non-inclined surface (vertical surface). The through hole H can be formed by subjecting the original material of the frame 6 to etching, laser processing, sandblasting, etc.

The frame 6 is made of a glass material having a thermal expansion coefficient of 30×10 ⁻⁷ to 100×10 ⁻⁷ /°C in the temperature range of 30 to 380°C. The thermal expansion coefficient of the frame 6 is preferably 40×10 ⁻⁷ /°C or more, 50×10 ⁻⁷ /°C or more, 60×10 ⁻⁷ /°C or more, and particularly preferably 70×10 ⁻⁷ /°C or more. The thermal expansion coefficient of the frame 6 is preferably 95×10 ⁻⁷ /°C or less, and particularly preferably 90×10 ⁻⁷ /°C or less. In this way, the thermal expansion coefficient of the frame 6 matches the thermal expansion coefficient of the base material 3 made of metal, metal nitride ceramics, or the like. As a result, even if the frame 6 is joined to the base material 3 using, for example, a brazing material, breakage is unlikely to occur at the joint 8 or its vicinity, and high airtightness can be maintained.

The glass material of the frame 6 is preferably ultraviolet-transmitting glass. In detail, the transmittance of the glass material of the frame 6 at an optical path length of 0.7 mm and a wavelength of 200 nm is preferably 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, and particularly preferably 80% or more. Also, the transmittance of the glass material of the frame 6 at an optical path length of 0.7 mm and a wavelength of 250 nm is preferably 50% or more, 60% or more, 70% or more, and particularly preferably 80% or more. Furthermore, in the glass material of the frame 6, when the transmittance at an optical path length of 0.7 mm and a wavelength of 250 nm is _T250 and the transmittance at an optical path length of 0.7 mm and a wavelength of 300 nm is _T300 , the value of _T250 / _T300 is preferably 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.85 or more, and particularly preferably 0.9 or more. In this way, although the transmittance of ultraviolet light is inferior to that of quartz glass, the light emitted from the electronic component 2 consisting of the ultraviolet LED can be transmitted without any problems, and the ultraviolet light extraction efficiency can be maintained at a high level.

The strain point of the glass material of the frame 6 is preferably 430°C or higher, 460°C or higher, 480°C or higher, 500°C or higher, 520°C or higher, 530°C or higher, and particularly preferably 550°C or higher. In this way, when the frame 6 is joined to the base material 3 using a brazing material, the occurrence of distortion in the frame 6 due to heating during brazing (e.g., about 300°C) can be suppressed.

The softening point of the glass material of the frame 6 is preferably 1000°C or less, 950°C or less, 900°C or less, or 850°C or less, and particularly preferably 800°C or less. In this way, when the frame 6 and the lid 7 are directly welded by laser welding or the like, the frame 6 softens easily, and the joining time can be shortened.

In the glass material of the frame 6, the temperature at 10 ^2.5 dPa·s is preferably 1580°C or less, 1550°C or less, 1520°C or less, 1500°C or less, 1480°C or less, and particularly preferably 1470°C or less. If the temperature at 10 ^2.5 dPa·s is too high, the melting property decreases, and the manufacturing cost of the glass tends to increase. Here, the "temperature at 10 ^2.5 dPa·s" can be measured by the platinum ball pulling method. The temperature at 10 ^2.5 dPa·s corresponds to the melting temperature, and the lower this temperature is, the better the melting property is.

The liquidus temperature of the glass material of the frame 6 is preferably less than 1150° C., 1120° C. or less, 1100° C. or less, 1080° C. or less, 1050° C. or less, 1030° C. or less, 980° C. or less, 960° C. or less, 950° C. or less, and particularly preferably 940° C. or less. The liquidus viscosity of the glass material of the frame 6 is preferably 10 ^4.0 dPa·s or more, 10 ^4.3 dPa·s or more, 10 ^4.5 dPa·s or more, 10 ^4.8 dPa·s or more, 10 ^5.1 dPa·s or more, 10 ^5.3 dPa·s or more, and particularly preferably 10 ^5.5 dPa·s or more. In this way, the devitrification resistance is improved. Here, the "liquidus temperature" is a value measured by placing a glass powder that has passed through a standard sieve of 30 mesh (500 μm) and remains on a 50 mesh (300 μm) in a platinum boat and holding it in a temperature gradient furnace for 24 hours, and then observing the temperature at which crystals precipitate, using a microscope. The "liquidus viscosity" is a value measured by measuring the viscosity of the glass at the liquidus temperature using a platinum ball pull-up method.

The Young's modulus of the glass material of the frame 6 is preferably 55 GPa or more, 60 GPa or more, 65 GPa or more, and particularly preferably 70 GPa or more. If the Young's modulus is too low, the frame 6 is more likely to deform, warp, or break. Here, "Young's modulus" refers to a value measured by the resonance method.

The glass material of the frame 6 _preferably has a glass composition, in mass %, of _SiO2 50-80%, _Al2O3 + _{B2O3 1-45} %, _Li2O + _Na2O + _K2O 0-25%, and MgO + CaO + SrO + BaO 0-25%. The reasons for limiting the content of each component as above are as follows. In the explanation of the content of each component, % denotes mass % unless otherwise specified.

SiO ₂ is the main component that forms the skeleton of glass. The content of SiO ₂ is preferably 50 to 80%, 55 to 75%, 58 to 70%, and particularly preferably 60 to 68%. If the content of SiO ₂ is too low, the Young's modulus and acid resistance tend to decrease. On the other hand, if the content of SiO ₂ is too high, the high-temperature viscosity increases, the melting property tends to decrease, and devitrified crystals such as cristobalite tend to precipitate, and the liquidus temperature tends to increase.

Al ₂ O ₃ and B ₂ O ₃ are components that enhance devitrification resistance. The content of Al ₂ O ₃ +B ₂ O ₃ is preferably 1 to 40%, 5 to 35%, 10 to 30%, and particularly preferably 15 to 25%. If the content of Al ₂ O ₃ +B ₂ O ₃ is too low, the glass is prone to devitrification. On the other hand, if the content of Al ₂ O ₃ +B ₂ O ₃ is too high, the component balance of the glass composition is impaired, and conversely, the glass is prone to devitrification.

Al ₂ O ₃ is a component that increases Young's modulus and also suppresses phase separation and devitrification. The content of Al ₂ O ₃ is preferably 1 to 20%, 3 to 18%, and particularly preferably 5 to 16%. If the content of Al ₂ O ₃ is too small, the Young's modulus is likely to decrease, and the glass is likely to undergo phase separation and devitrification. On the other hand, if the content of Al ₂ O ₃ is too large, the high-temperature viscosity increases, and the melting property is likely to decrease.

B ₂ O ₃ is a component that enhances melting property and devitrification resistance, and also improves scratch resistance and enhances strength. The content of B ₂ O ₃ is preferably 3 to 25%, 5 to 22%, 7 to 19%, and particularly preferably 9 to 16%. If the content of B ₂ O ₃ is too low, the melting property and devitrification resistance tend to decrease, and the resistance to hydrofluoric acid-based chemicals tend to decrease. On the other hand, if the content of B ₂ O ₃ is too high, the Young's modulus and acid resistance tend to decrease.

Li ₂ O, Na ₂ O and K ₂ O are components that reduce high-temperature viscosity, significantly increase meltability, and contribute to the initial melting of glass raw materials. The content of Li ₂ O + Na ₂ O + K ₂ O is preferably 0-25%, 1-20%, 4-15%, and particularly preferably 7-13%. If the content of Li ₂ O + Na ₂ O + K ₂ O is too low, the meltability is likely to decrease. On the other hand, if the content of Na ₂ O is too high, the thermal expansion coefficient may become unduly high.

Li ₂ O is a component that reduces high-temperature viscosity, significantly increases meltability, and contributes to the initial melting of glass raw materials. The content of Li ₂ O is preferably 0-5%, 0-3%, 0-1%, and particularly preferably 0-0.1%. If the content of Li ₂ O is too low, the meltability is likely to decrease, and the thermal expansion coefficient may be unduly low. On the other hand, if the content of Li ₂ O is too high, the glass is likely to undergo phase separation.

Na ₂ O is a component that reduces high-temperature viscosity, significantly increases meltability, and contributes to the initial melting of glass raw materials. It is also a component for adjusting the thermal expansion coefficient. The content of Na ₂ O is preferably 0 to 25%, 1 to 20%, 3 to 18%, 5 to 15%, and particularly preferably 7 to 13%. If the content of Na ₂ O is too low, the meltability is likely to decrease, and the thermal expansion coefficient may become unduly low. On the other hand, if the content of Na ₂ O is too high, the thermal expansion coefficient may become unduly high.

K ₂ O is a component that reduces high-temperature viscosity, significantly increases meltability, and contributes to the initial melting of glass raw materials. It is also a component for adjusting the thermal expansion coefficient. The content of K ₂ O is preferably 0 to 15%, 0.1 to 10%, and particularly preferably 1 to 5%. If the content of K ₂ O is too high, the thermal expansion coefficient may become unduly high.

MgO, CaO, SrO and BaO are components that reduce high-temperature viscosity and increase meltability. The content of MgO+CaO+SrO+BaO is preferably 0-25%, 0-15%, 0.1-12%, or 1-5%. If the content of MgO+CaO+SrO+BaO is too high, the glass is prone to devitrification.

MgO is a component that reduces high-temperature viscosity and increases melting property, and among alkaline earth metal oxides, it is a component that significantly increases Young's modulus. The MgO content is preferably 0-10%, 0-8%, 0-5%, and particularly preferably 0-1%. If the MgO content is too high, devitrification resistance is likely to decrease.

CaO is a component that reduces high-temperature viscosity and significantly increases melting properties. In addition, among alkaline earth metal oxides, the raw materials used are relatively inexpensive, so it is a component that reduces raw material costs. The CaO content is preferably 0-15%, 0.5-10%, and particularly preferably 1-5%. If the CaO content is too high, the glass becomes more susceptible to devitrification. If the CaO content is too low, it becomes difficult to enjoy the above effects.

SrO is a component that enhances resistance to devitrification. The SrO content is preferably 0-7%, 0-5%, or 0-3%, and particularly preferably 0-1%. If the SrO content is too high, the glass becomes more susceptible to devitrification.

BaO is a component that enhances resistance to devitrification. The BaO content is preferably 0-7%, 0-5%, 0-3%, or less than 0-1%. If the BaO content is too high, the glass becomes more susceptible to devitrification.

In addition to the above components, other components may be introduced as optional components. From the viewpoint of accurately enjoying the effects of the present invention, the content of other components other than the above components is preferably 10% or less in total, 5% or less, and particularly 3% or less.

ZnO is a component that improves meltability, but if it is included in a large amount in the glass composition, the glass becomes more susceptible to devitrification. Therefore, the ZnO content is preferably 0-5%, 0-3%, 0-1%, or 0-less than 1%, and particularly preferably 0-0.1%.

_ZrO2 is a component that enhances acid resistance, but if it is contained in a large amount in the glass composition, the glass becomes prone to devitrification. Therefore, the content of _ZrO2 is preferably 0 to 5%, 0 to 3%, 0 to 1%, 0 to 0.5%, and particularly preferably 0.001 to 0.2%.

Fe ₂ O ₃ and TiO ₂ are components that reduce the transmittance in the deep ultraviolet region. The content of Fe ₂ O ₃ +TiO ₂ is preferably 100 ppm or less, 80 ppm or less, 60 ppm or less, 0.1 to 40 ppm or less, and particularly preferably 1 to 20 ppm. If the content of Fe ₂ O ₃ +TiO ₂ is too high, the glass becomes colored and the transmittance in the deep ultraviolet region tends to decrease. If the content of Fe ₂ O ₃ +TiO ₂ is too low, a high-purity glass raw material must be used, which leads to an increase in batch costs.

Fe ₂ O ₃ is a component that reduces the transmittance in the deep ultraviolet region. The content of Fe ₂ O ₃ is preferably 100 ppm or less, 80 ppm or less, 60 ppm or less, 40 ppm or less, 20 ppm or less, 10 ppm or less, and particularly preferably 1 to 8 ppm. If the content of Fe ₂ O ₃ is too high, the glass is colored and the transmittance in the deep ultraviolet region is likely to decrease. If the content of Fe ₂ O ₃ is too low, it is necessary to use high-purity glass raw materials, which leads to an increase in batch costs.

The Fe ions in the iron oxide exist in the form of Fe2 ⁺ or Fe3 ⁺ . If the ratio of ^Fe2+ is too small, the transmittance of deep ultraviolet light is likely to decrease. Therefore, the mass ratio of ^Fe2+ /( ^Fe2 ++Fe3 ⁺ ) in the iron oxide is preferably 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, and particularly preferably 0.5 or more.

_TiO2 is a component that reduces the transmittance in the deep ultraviolet region. The content of _TiO2 is preferably 100 ppm or less, 80 ppm or less, 60 ppm or less, 40 ppm or less, 20 ppm or less, 10 ppm or less, and particularly preferably 0.5 to 5 ppm. If the content of _TiO2 is too high, the glass is colored and the transmittance in the deep ultraviolet region is likely to decrease. If the content of _TiO2 is too low, it is necessary to use high-purity glass raw materials, which leads to an increase in batch costs.

Sb ₂ O ₃ is a component that acts as a clarifier. The content of Sb ₂ O ₃ is preferably 1000 ppm or less, 800 ppm or less, 600 ppm or less, 400 ppm or less, 200 ppm or less, 100 ppm or less, and particularly preferably less than 50 ppm. If the content of Sb ₂ O ₃ is too high, the transmittance in the deep ultraviolet region tends to decrease.

_SnO2 is a component that acts as a clarifier. The content of _SnO2 is preferably 2000 ppm or less, 1700 ppm or less, 1400 ppm or less, 1100 ppm or less, 800 ppm or less, 500 ppm or less, 200 ppm or less, and particularly preferably 100 ppm or less. If the content of _SnO2 is too high, the transmittance in the deep ultraviolet region tends to decrease.

F ₂ , Cl ₂ and SO ₃ are components that act as clarifiers. The content of F ₂ +Cl ₂ +SO ₃ is preferably 10 to 10,000 ppm. The preferred lower limit range of F ₂ +Cl ₂ +SO ₃ is 10 ppm or more, 20 ppm or more, 50 ppm or more, 100 ppm or more, 300 ppm or more, particularly 500 ppm or more, and the preferred upper limit range is 3,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, particularly 800 ppm or less. The preferred lower limit ranges of _F2 , _Cl2 , and _SO3 are 10 ppm or more, 20 ppm or more, 50 ppm or more, 100 ppm or more, 300 ppm or more, particularly 500 ppm or more, and the preferred upper limit ranges are 3000 ppm or less, 2000 ppm or less, 1000 ppm or less, particularly 800 ppm or less. If the content of these components is too small, it is difficult to exert the fining effect. On the other hand, if the content of these components is too large, there is a risk that fining gas will remain as bubbles in glass.

The glass material of the frame 6 can be produced, for example, by mixing various glass raw materials to obtain a glass batch, melting the glass batch, clarifying and homogenizing the resulting molten glass, and forming it into a predetermined shape.

In the manufacturing process of the glass material of the frame 6, a reducing agent is preferably used as part of the glass raw material. In this way, Fe3 ⁺ contained in the glass is reduced, improving the transmittance in deep ultraviolet rays. As the reducing agent, materials such as wood powder, carbon powder, metallic aluminum, metallic silicon, and aluminum fluoride can be used, among which metallic silicon and aluminum fluoride are preferred.

In the manufacturing process of the glass material of the frame 6, metallic silicon is preferably used as part of the glass raw material, and the amount of metallic silicon added is preferably 0.001 to 3 mass%, 0.005 to 2 mass%, 0.01 to 1 mass%, and particularly preferably 0.03 to 0.1 mass% relative to the total mass of the glass batch. If the amount of metallic silicon added is too small, Fe3 ⁺ contained in the glass is not reduced, and the transmittance of deep ultraviolet light is likely to decrease. On the other hand, if the amount of metallic silicon added is too large, the glass tends to be colored brown.

It is also preferable to use aluminum fluoride (AlF ₃ ) as a part of the glass raw material, and the amount of addition is preferably 0.01 to 5 mass%, 0.05 to 4 mass%, 0.1 to 3 mass%, 0.2 to 2 mass%, or 0.3 to 1 mass% in terms of F ₂ relative to the total mass of the glass batch. On the other hand, if the amount of aluminum fluoride added is too large, F ₂ gas may remain as bubbles in the glass. If the amount of aluminum fluoride added is too small, Fe ³⁺ contained in the glass is not reduced, and the transmittance of deep ultraviolet light is likely to decrease.

In the manufacturing process of the glass material of the frame 6, it is preferable to form it into a flat plate shape by the down-draw method, especially the overflow down-draw method. The overflow down-draw method is a method in which molten glass is made to overflow from both sides of a heat-resistant trough-shaped structure, and the overflowed molten glass is stretched downward while joining at the lower end of the trough-shaped structure to form a glass plate. In the overflow down-draw method, the surface that should become the surface of the glass plate does not contact the trough-shaped refractory material and is formed in a free surface state. This makes it easier to produce a thin glass plate, and the plate thickness variation can be reduced without polishing the surface. As a result, the manufacturing cost of the glass plate can be reduced. The structure and material of the trough-shaped structure are not particularly limited as long as they can achieve the desired dimensions and surface accuracy. In addition, the method of applying force when performing downward stretching is not particularly limited. For example, a method may be used in which a heat-resistant roll having a sufficiently large width is rotated while in contact with the glass to stretch it, or a method may be used in which multiple pairs of heat-resistant rolls are in contact with only the vicinity of the edge of the glass to stretch it.

In addition to the overflow downdraw method, other methods such as the slot down method, redraw method, and float method can also be used to form the glass material of the frame portion 6.

Specifically, for example, BU-41 manufactured by Nippon Electric Glass Co., Ltd. can be used as the glass material of the frame 6. The thermal expansion coefficient of BU-41 in the temperature range of 30 to 380° C. is, for example, 42×10 ⁻⁷ /° C.

The thickness (vertical dimension) of the frame 6 is preferably larger than that of the electronic component 2, preferably 0.01 to 1 mm larger than that of the electronic component 2, more preferably 0.05 to 0.5 mm larger, and most preferably 0.1 to 0.2 mm larger.

The lid 7 is made of quartz glass. Quartz glass includes fused quartz and synthetic quartz. The thermal expansion coefficient of fused quartz glass in the temperature range of 30 to 380°C is, for example, 6.3×10 ⁻⁷ /°C, and the thermal expansion coefficient of synthetic quartz glass in the temperature range of 30 to 380°C is, for example, 4.0×10 ⁻⁷ /°C. In this embodiment, the lid 7 is a plate-like body with both the upper surface 7a and the lower surface 7b formed of flat surfaces.

The thickness (vertical dimension) of the lid portion 7 is preferably 0.1 to 1.0 mm, more preferably 0.2 to 0.8 mm, and most preferably 0.3 to 0.6 mm.

As shown in FIG. 2, in this embodiment, the joint 8 that joins the frame 6 and the lid 7 is formed from a welded portion 9 in which the frame 6 and the lid 7 are directly welded to each other. The welded portion 9 is formed by laser welding. In detail, the welded portion 9 is formed by melting at least one of the frame 6 and the lid 7 in the laser irradiation area and then solidifying the melted portion. In other words, the welded portion 9 is preferably made of, for example, the material of at least one of the frame 6 and the lid 7, and does not substantially contain materials other than the frame 6 and the lid 7.

Multiple welded portions 9 (two in the illustrated example) are formed in a concentric ring shape along the through hole H, but one may also be formed. The multiple welded portions 9 are radially spaced apart from one another, but may overlap in the radial direction. Each welded portion 9 is configured in a square ring shape in a plan view, but is not limited to this and may be configured in a circular ring shape or other ring shapes.

The welded portion 9 is formed continuously across the frame portion 6 and the lid portion 7 in the thickness direction. In this embodiment, there is no interface between the frame portion 6 and the lid portion 7 inside the welded portion 9. Of course, an interface may remain between the frame portion 6 and the lid portion 7 inside the welded portion 9.

The width S1 of the welded portion 9 is preferably 10 to 200 μm, more preferably 10 to 100 μm, and most preferably 10 to 50 μm. The thickness S2 of the welded portion 9 is preferably 10 to 200 μm, more preferably 10 to 150 μm, and most preferably 10 to 100 μm.

The maximum value of the planar residual stress of the welded portion 9 is preferably 10 MPa or less, more preferably 7 MPa or less, and most preferably 5 MPa or less. The maximum value of the planar residual stress is the maximum value when the birefringence (unit: nm) near the joint is measured using a Uniopto ABR-10A birefringence measuring device in a glass plate having dimensions of 10 mm x 10 mm or more, and converted into the planar residual stress. In addition, the residual stress value in the glass plate can be estimated by measuring the optical birefringence, that is, the optical path difference of orthogonal linearly polarized waves, and the deviatoric stress F (MPa) generated by the residual stress is expressed by the formula F = D/CW. "D" is the optical path difference (nm), "W" is the distance (cm) traveled by the polarized wave, and "C" is the photoelastic constant (proportionality constant), which is usually 20 to 40 (nm/cm)/(MPa). In addition, residual stress in the planar direction includes tensile stress and compressive stress, but in the above, the absolute values of both are evaluated.

The joint 5 for joining the frame 6 and the base material 3 is not particularly limited, but in this embodiment, the joint 5 includes a metallized layer 10 and a solder layer 11 in this order from the lower end surface 6b of the frame 6. The metallized layer 10 is a metal film formed on the lower end surface 6b of the frame 6 of the protective cap 4 by vapor deposition, sputtering, or the like, and has a role of improving adhesion with the solder layer 11. As the metallized layer 10, for example, Cr, Ti, Ni, Pt, Au, Co, and alloy layers containing these, or multilayer films of these metals and alloys, etc. can be used. As the solder layer (brazing material) 11, for example, Au, Sn, Ag, Pb, and alloys containing these metals, that is, Au-Sn solder, Sn-Ag solder, Pb solder, etc. can be used. The thermal expansion coefficient of the Au-Sn solder in the temperature range of 30 to 380°C is, for example, 175×10 ⁻⁷ /°C.

Figure 3 shows the transmittance curves of BU-41 (manufactured by Nippon Electric Glass Co., Ltd.) and quartz glass in the wavelength range of 200 to 600 nm. As shown in the figure, quartz glass has a transmittance of 90% or more in the deep ultraviolet range (e.g., wavelength range of 200 to 350 nm) without a decrease in transmittance as the thickness increases. On the other hand, BU-41 has a transmittance of 84% or more at a thickness of 0.2 mm in the deep ultraviolet range, and a transmittance of 70% or more at a thickness of 0.5 mm. In other words, BU-41 has good transmittance in the deep ultraviolet range, although it is slightly inferior to that of quartz glass. In the state of the electronic device (light-emitting device) 1, specifically, when both the lid 7 and the frame 6 are made of quartz glass having a thickness of 0.6 mm, the ultraviolet light extraction efficiency (output magnification of the electronic component (ultraviolet LED) 2) is 89% on average, and when the lid 7 is made of quartz glass having a thickness of 0.6 mm and the frame 6 is made of BU-41 having a thickness of 0.6 mm, the ultraviolet light extraction efficiency is 88% on average. Therefore, even if the lid 7 is made of quartz glass and the frame 6 is made of a glass material having ultraviolet light transmission other than quartz glass (e.g., BU-41), the ultraviolet light extraction efficiency can be maintained at a high level. In addition, in this case, since the thermal expansion coefficient of the frame 6 and the thermal expansion coefficient of the base material 3 match, even if the frame 6 is joined to the base material 3 using a brazing material or the like, damage is unlikely to occur at the joint 5 or its vicinity, and high airtightness can be maintained.

Figures 4 to 7 illustrate a method for manufacturing an electronic device 1 according to a first embodiment of the present invention.

The manufacturing method of the electronic device 1 according to this embodiment includes a first joining process for joining the lid portion 7 and the frame portion 6 to obtain the protective cap 4, and a second joining process for joining the base material 3 on which the electronic component 2 is mounted and the protective cap 4.

In the first joining step, first, as shown in FIG. 4, the lid portion 7 and the frame portion 6 on which the metallized layer 10 and the solder layer 11 are formed are prepared. Next, the lower surface 7b of the lid portion 7 and the upper end surface 6a of the frame portion 6 are brought into direct contact with each other. In this state, as shown in FIG. 5, the laser irradiation device 12 focuses and irradiates the contact portion between the lid portion 7 and the frame portion 6 with a laser L. The laser L is irradiated from at least one side of the lid portion 7 and the frame portion 6. In this embodiment, the laser L is irradiated from the lid portion 7 side. As a result, the contact portion is welded to form a welded portion 9, and the frame portion 6 and the lid portion 7 are joined by the welded portion 9.

The arithmetic mean roughness Ra of each of the lower surface 7b of the lid portion 7 and the upper end surface 6a of the frame portion 6 is preferably 2.0 nm or less, more preferably 1.0 nm or less, even more preferably 0.5 nm or less, and most preferably 0.2 nm or less. The arithmetic mean roughness Ra refers to a value measured by a method conforming to JIS B0601:2001. In this way, the lid portion 7 and the frame portion 6 are adhered to each other by intermolecular forces (optical contact) between the joining surfaces, improving handleability before laser joining.

As the laser L, an ultrashort pulse laser with a pulse width on the order of picoseconds or femtoseconds is preferably used.

The wavelength of the laser L is not particularly limited as long as it is a wavelength that transmits through the glass member, but is preferably 400 to 1600 nm, and more preferably 500 to 1300 nm, for example. The pulse width of the laser L is preferably 10 ps or less, more preferably 5 ps or less, and most preferably 200 fs to 3 ps. The focused diameter of the laser L is preferably 50 μm or less, more preferably 30 μm or less, and preferably 20 μm or less.

The repetition frequency of the laser L must be sufficient to cause continuous heat accumulation, and specifically, it is preferably 100 kHz or more, more preferably 200 kHz or more, and even more preferably 500 kHz or more.

It is also preferable to use a method (burst mode) in which one pulse is divided into multiple parts and the pulse interval is further shortened. This makes it easier for heat to accumulate, and the joint 8 can be formed stably.

As shown in FIG. 6, the laser L is scanned so as to trace a circular orbit T along the outside of the through hole H. In this case, the laser L is scanned so as to circle the circular orbit T while the irradiation area R overlaps on the circular orbit T. Alternatively, the laser L is scanned so as to circle the circular orbit T multiple times. When multiple welds 9 are formed in a concentric ring shape, multiple circular orbits T for scanning the laser L are also set in a concentric ring shape.

Four straight lines may be crossed in a crisscross pattern to surround the through hole H, forming a frame-shaped joint. This allows multiple protective caps 4 to be produced at once, improving the manufacturing efficiency of the electronic device 1.

In the above first joining step, the metallized layer 10 and the solder layer 11 are pre-formed on the frame portion 6, but these layers 10, 11 may be formed on the frame portion 6 after the first joining step (after the lid portion 7 and the frame portion 6 are joined).

In the second joining step, first, as shown in FIG. 7, the protective cap 4 obtained in the first joining step and the substrate 3 on which the electronic component 2 is mounted are prepared. Next, the lower end surface 6b of the frame 6 and the upper surface 3a of the substrate 3 are brought into contact with each other via the metallized layer 10 and the solder layer 11. By heating in this state, the solder layer 11 is softened and fluidized (reflowed), and the frame 6 and the substrate 3 are joined by the solder layer 11. The solder layer 11 may be heated using a heating furnace or a laser.

Second Embodiment
8 illustrates an electronic device 1 according to a second embodiment of the present invention. In the second embodiment, the configuration of a joint 5 that joins a frame 6 and a base material 3 is different from that of the first embodiment.

In this embodiment, the joint 5 is formed from a welded portion 21 in which the frame 6 and the base material 3 are directly welded together. The welded portion 21 is formed by laser welding. In detail, the welded portion 21 is formed by melting at least one of the frame 6 and the base material 3 in the laser irradiation area, and then solidifying the melted portion. In other words, the welded portion 21 is preferably made of, for example, at least one of the materials of the frame 6 and the base material 3, and does not substantially contain materials other than the frame 6 and the base material 3.

The rest of the configuration of the welded portion 21 is similar to that of the welded portion 9 described in the first embodiment, so a detailed description will be omitted.

Figures 9 to 12 illustrate a method for manufacturing an electronic device 1 according to a second embodiment of the present invention.

The manufacturing method of the electronic device 1 according to this embodiment includes a first joining process for joining the lid portion 7 and the frame portion 6 to obtain the protective cap 4, and a second joining process for joining the base material 3 on which the electronic component 2 is mounted and the protective cap 4.

As shown in Figures 9 and 10, the first joining process is the same as the first joining process described in the first embodiment, and is a process in which the lid portion 7 and the frame portion 6 are directly welded together using a laser L emitted from a laser irradiation device 12. Note that the metallized layer 10 and the solder layer 11 are not formed on the frame portion 6, and the lower end surface 6b of the frame portion 6 is exposed.

As shown in Figures 11 and 12, in the second joining step, first, the lower end surface 6b of the frame 6 of the protective cap 4 obtained in the first joining step is brought into direct contact with the upper surface 3a of the base material 3. In this state, the laser L is focused and irradiated to the contact portion between the frame 6 and the base material 3 by the laser irradiation device 12. The laser L is irradiated from the frame 6 side, which transmits the laser L, of the frame 6 and the base material 3. As a result, the contact portion is welded to form a welded portion 21, and the frame 6 and the base material 3 are joined by the welded portion 21.

The arithmetic mean roughness Ra of each of the lower end surface 6b of the frame 6 and the upper surface 3a of the substrate 3 is preferably 2.0 nm or less, more preferably 1.0 nm or less, even more preferably 0.5 nm or less, and most preferably 0.2 nm or less. In this way, the frame 6 and the substrate 3 are adhered to each other by intermolecular forces between the bonding surfaces, improving the handling properties before laser bonding.

The conditions for the type, wavelength, scanning method, and other aspects of the laser L used in the second bonding process can be the same as those for the first bonding process described in the first embodiment.

The present invention is not limited to the configuration of the above embodiment, nor is it limited to the above-mentioned effects. Various modifications of the present invention are possible without departing from the gist of the present invention.

In the above embodiment, the frame 6 and the lid 7 are directly welded to each other, but the method of joining the frame 6 and the lid 7 is not limited to this. For example, the frame 6 and the lid 7 may be bonded to each other via an adhesive layer (e.g., a glass adhesive).

In the above embodiment, the lid 7 may be joined to the frame 6 after the frame 6 and the substrate 3 are joined. In this case, the electronic component 2 may be mounted on the substrate 3 after the frame 6 and the substrate 3 are joined, and then the lid 7 may be joined to the frame 6. However, when considering workability, it is preferable to mount the electronic component 2 on the substrate 3 before the frame 6 and the substrate 3 are joined.

Third Embodiment
13 illustrates a frame 6 according to a third embodiment of the present invention. In this embodiment, a reflective film 31 is formed on an inner circumferential surface 6c of the frame 6 in order to improve the light extraction efficiency.

The reflective film 31 is a layer that reflects the light emitted from the electronic component 2. The reflective film 31 is preferably made of a resin paint or glass paste that contains a metal such as aluminum or gold, or a ceramic such as alumina, zirconia, or titania.

The thickness of the reflective film 31 is preferably, for example, 0.1 to 100 μm.

The reflectance of the reflective film 31 in the wavelength band of the light emitted from the electronic component 2 (e.g., 250-350 nm) is preferably 10%, 20%, 30%, 40%, 50%, 60% or more, and particularly preferably 70% or more. Here, the reflectance can be calculated by measuring the transmittance at each wavelength in the wavelength range of 250-350 nm using a Hitachi High-Tech Science UH-4150.

As a method for forming the reflective film 31 on the inner peripheral surface 6c of the frame portion 6, it is preferable to use a spray coating method. When using the spray coating method, the flat parts of the upper and lower end faces 6a and 6b of the frame portion 6 are protected by a mask, and a spray coating liquid (liquid that becomes a reflective film) is applied to the inner peripheral surface of the frame portion 6, and then the mask is peeled off, so that the reflective film 31 can be easily formed on the inner peripheral surface 6c of the frame portion 6. Note that the method for forming the reflective film 31 is not limited to this, and for example, a dip coating method can also be used. When using the dip coating method, the frame portion 6 having the through hole H is immersed in a dip coating liquid (liquid that becomes the reflective film 31), and then the reflective film 31 formed on the unnecessary parts of the surface of the frame portion 6 (such as the upper and lower end faces 6a and 6b) is removed by polishing or the like, so that the reflective film 31 can be formed on the inner peripheral surface 6c of the frame portion 6. In this case, when removing the reflective film 31 from the unnecessary parts, the upper end face 6a of the frame portion 6 is polished, so that the surface accuracy at the time of joining with the lid portion 7 can be adjusted.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

(1) Protective caps A and B Protective cap A was produced as a comparative example by joining a lid made of quartz glass and a frame made of quartz glass with a brazing material (gold-tin solder: thermal expansion coefficient 176×10 ⁻⁷ /°C). Protective cap B was produced as an example by directly welding a lid made of quartz glass and a frame made of BU-41 (thermal expansion coefficient 42×10 ⁻⁷ /°C) by laser irradiation.

For the resulting protective caps A and B, metallization layers of Cr, Ni, and Au were sequentially formed at the joints with the base material, and a solder layer composed of Au-Sn solder was then formed on top of them.

Protective caps A and B with a solder layer formed on them were used to heat mount onto an aluminum nitride substrate to produce an electronic device, and the rate of cracking of the protective caps was measured. As a result, approximately 4% of protective caps had cracks after mounting, but no cracks occurred in protective cap B after mounting.

(2) Protective caps C and D Protective cap C was produced as an example by welding a lid made of quartz glass, on both sides of which an ultraviolet ray anti-reflection film was formed, and a frame made of BU-41 by laser irradiation. Protective cap D was produced as an example by welding a lid made of quartz glass, on both sides of which an ultraviolet ray anti-reflection film was formed, and a frame made of BU-41, on the inner surface of which an ultraviolet ray reflective film was formed, by laser irradiation.

For the resulting protective caps C and D, metallization layers of Cr, Ni, and Au were sequentially formed at the joints with the substrate, and a solder layer composed of Au-Sn solder was then formed on top of them.

Using protective caps C and D on which a solder layer was formed, electronic devices were fabricated by thermally mounting the device on an aluminum nitride substrate, and the light extraction efficiency was measured. As a result, the electronic device using protective cap D had a 3% improvement in light extraction efficiency compared to the electronic device using protective cap C.

In the above examples, the present invention was explained using an example in which BU-41 was used for the frame, but in addition to BU-41, glass samples No. 1 to 3 shown in Table 1 can also be used. In the table below, Ps is the strain point, Ta is the annealing point, Ts is the softening point, α is the thermal expansion coefficient, E is Young's modulus, TL is the liquidus temperature, and Log η at TL is the liquidus viscosity.

Reference Signs List 1 Electronic device 2 Electronic component 3 Base material 4 Protective cap 5 Joint portion 6 Frame portion 7 Lid portion 8 Joint portion 9 Welded portion 10 Metallized layer 11 Solder layer 21 Welded portion

Claims (12)

A protective cap for protecting an electronic component,
a frame portion, a lid portion that covers an opening at one end of the frame portion, and a joint portion that joins the frame portion and the lid portion,
The lid portion is made of quartz glass,
The protective cap is characterized in that the frame is made of a glass material having a thermal expansion coefficient of 30×10 ⁻⁷ to 100×10 ⁻⁷ /° C. in a temperature range of 30 to 380° C. The protective cap according to claim 1, wherein the joint is formed by directly welding the frame and the lid. A protective cap according to claim 1 or 2, in which the glass material of the frame has a thickness of 0.7 mm and a transmittance of 10% or more at a wavelength of 200 nm. A protective cap according to any one of claims 1 to 3, in which the strain point of the glass material of the frame is 430°C or higher. A protective cap according to any one of claims 1 to 4, in which the softening point of the glass material of the frame is 1000°C or less. The protective cap according to any one of claims 1 to 5, wherein the glass material of the frame contains, in mass %, 50 to 80% SiO ₂ , 1 to 45% Al ₂ O ₃ + B ₂ O ₃ , 0 to 25% Li ₂ O + Na ₂ O + K ₂ O , and 0 to 25% MgO + CaO + SrO + BaO. A protective cap according to any one of claims 1 to 6, in which a reflective film is formed on the inner peripheral surface of the frame. A protective cap according to any one of claims 1 to 7, in which an anti-reflection film is formed on at least one of the front and back surfaces of the lid. An electronic device comprising an electronic component, a substrate on which the electronic component is mounted, and a protective cap according to any one of claims 1 to 8 bonded to the substrate so as to house the electronic component therein. The electronic device according to claim 9, wherein the protective cap and the base material are joined by a brazing material. The electronic device according to claim 9 or 10, wherein the electronic component is an ultraviolet LED. A method for manufacturing a protective cap for protecting an electronic component, comprising the steps of:
a preparation step of preparing a cover made of quartz glass and a frame made of a glass material having a thermal expansion coefficient of 30×10 ⁻⁷ to 100×10 ⁻⁷ /° C. in a temperature range of 30 to 380° C.;
a joining process in which the lid portion is brought into contact with the frame portion so as to cover one end opening of the frame portion, and a laser is irradiated to the contact portion of the lid portion and the frame portion to directly weld the lid portion and the frame portion together.