JP7356983B2 - UV element package - Google Patents

Description

The present invention relates to a light-emitting element such as a near-ultraviolet LED containing deep ultraviolet light used for, for example, ultraviolet sterilization, water purification, air purification, or curing of adhesives and resins, and an optical member provided at a position facing the light-emitting element. The present invention relates to an ultraviolet element package comprising:

Mercury lamps have traditionally been widely used for ultraviolet sterilization, but with the entry into force of the Minamata Convention on Mercury, the manufacture, import and export of mercury products will be restricted from 2020 onwards. Therefore, ultraviolet LEDs (Light Emitting Diodes), particularly deep ultraviolet LEDs with a wavelength of 280 nm or less, are attracting attention as an alternative light source after the life of currently used mercury lamps has expired.

As a device of this type, a light emitting module that outputs ultraviolet light with a wavelength of 200 nm to 360 nm has been disclosed (see, for example, Patent Document 1). This light emitting module includes a substrate having a bottomed recess on which a light emitting element is mounted, and a window member attached to cover the opening of the bottomed recess. This light emitting module is equipped with a lens section for controlling the light distribution of light emitted from the ultraviolet LED. The flange portion for bonding to the substrate is integrally formed with the lens portion.

In Patent Document 1, the window member is formed by pouring fused quartz made of quartz glass pellets or the like into a mold (see paragraph 0034). However, quartz glass has a very high softening point of about 1700°C, and even when heated to 1900°C, it remains very hard and difficult to process. Furthermore, since silica glass has a high vapor pressure, it directly changes from a solid state to a gas state, so it may not be in a molten state, and it is very difficult to obtain a desired lens shape from fused silica. Therefore, the traditional manufacturing method of glass lenses is generally used, which involves cutting and grinding quartz glass supplied in ingot form into a predetermined shape, and then polishing the surface to a mirror finish, resulting in very expensive lenses. It becomes.

On the other hand, although quartz glass has conventionally been used as a material that transmits deep ultraviolet rays with a wavelength of 300 nm or less with high transmittance, glasses that transmit deep ultraviolet rays with a wavelength of 300 nm or less with high transmittance have also been developed. The softening point of this type of glass is 1000°C or lower, and it is possible that a desired lens shape can be obtained by a manufacturing method other than the traditional glass lens manufacturing method described above (for example, see Patent Document 2). ).

JP2017-59716A Japanese Patent Application Publication No. 2006-310375

By the way, in the light emitting module of Patent Document 1, predetermined portions of the lens portion and the flange portion of the window member are masked, and titanium (Ti) is applied to the unmasked portions by a method such as vacuum evaporation or sputtering. ), copper (Cu), nickel (Ni), and gold (Au) are laminated in this order. However, it is not easy to mask a lens portion or a flange portion having a minute three-dimensional shape. However, if masking is insufficient and appropriate metallization processing is not performed, there is a risk that the bonding and sealing between the substrate and the window member will be incomplete. Ultraviolet rays, especially deep ultraviolet rays with short wavelengths, can significantly deteriorate resin materials, etc. Therefore, it is necessary to prevent the leakage of deep ultraviolet rays from the package of an optical module containing a light emitting element that handles deep ultraviolet rays. , which greatly affects product reliability.

The present invention was made to solve the above problems, and uses glass that has a lower softening point than quartz glass and a higher average transmittance for light with a wavelength of 250 to 400 nm or less, and can be used to fabricate a substrate using an inexpensive and simple process. An object of the present invention is to provide an ultraviolet element package that can bond an optical member with an optical member and has high sealing performance.

In order to achieve the above object, the present invention provides an ultraviolet element package including a light emitting element that emits ultraviolet light, a substrate on which the light emitting element is mounted, and an optical member provided at a position facing the light emitting element. The optical member is made of glass having a softening point of 1000° C. or less and an average transmittance of 80% or more for light with a wavelength of 250 to 400 nm, and the optical member is made of metal sealed and bonded to the optical member. is joined to the substrate via a pedestal, and the pedestal has an upper opening that is circular in plan view into which the optical member is fitted, and a lower opening that is approximately rectangular in bottom view in which the light emitting element is accommodated. A holding part is formed between the top side periphery of the bottom opening and the bottom side periphery of the top opening, and is formed of a plane parallel to the top and bottom surfaces of the pedestal and holds the optical member. It is characterized by

In the above ultraviolet element package, it is preferable that the pedestal is formed of a metal having a coefficient of thermal expansion substantially equal to a coefficient of thermal expansion of the glass.

In the above ultraviolet element package, it is preferable that the pedestal is sealed and bonded to the optical member by an oxide film formed on the surface of the pedestal.

In the ultraviolet device package, a metallized portion subjected to a metallization treatment is formed at a joint portion of the substrate with the pedestal, and the pedestal and the metallized portion are bonded by a metal preform. preferable.

In the above ultraviolet element package, it is preferable that the optical member is a dome lens with a protruding light exit surface.

In the above ultraviolet element package, the optical member may be a flat lens having a flat light exit surface.

According to the present invention, since the optical member is molded from molten or softened glass pellets, the manufacturing process is cheaper and simpler than the traditional method of manufacturing glass lenses, which involves cutting and grinding quartz glass ingots. can be converted into In addition, the optical member has a circular outer shape on the surface facing the substrate, and the opening on the top surface of the pedestal into which the optical member is fitted is circular in plan view. By uniformly pulling and holding the radially spread glass, glass of uniform thickness is formed, and as a result, an airtight glass seal portion with high sealing performance can be obtained. Furthermore, since the optical member is integrally sealed and bonded to the metal pedestal at the same time as the optical member is molded, masking for metallization treatment and metal vapor deposition processes are not necessary. Further, by joining the pedestal integrated with the optical member and the metallized portion of the metallized substrate using a metal preform, the substrate and the optical member can be brought into airtight contact. As a result, a highly reliable ultraviolet light device package can be provided at low cost.

(a) is an exploded perspective view showing the configuration of an ultraviolet device package according to an embodiment of the present invention, and (b) is a completed perspective view. (a) is an exploded perspective view showing the structure of an ultraviolet element package according to a modification of the above embodiment, and (b) is a completed perspective view. 3 is a graph showing a transmittance distribution of glass constituting an optical member used in the ultraviolet device package. (a) is a perspective view of a pedestal used in the above-mentioned ultraviolet element package, (b) is a plan view, and (c) is a sectional view taken along the line AA in (b). (a) to (f) are process diagrams illustrating a method for manufacturing the ultraviolet element package, and in particular, diagrams illustrating a process for manufacturing an optical member integrated with a pedestal. (a) is a process diagram showing the manufacturing method of the ultraviolet element package, and (b) is a diagram specifically showing a second step of joining the optical member integrated with the substrate and the pedestal.

An ultraviolet device package according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of an ultraviolet device package 1 according to an embodiment of the present invention. As shown in FIGS. 1(a) and 1(b), the ultraviolet element package 1 is provided with a light emitting element 2 that emits deep ultraviolet light, a substrate 3 on which the light emitting element 2 is mounted, and a position facing the light emitting element 2. An optical member 4 is provided. The optical member 4 is joined to the substrate 3 via a metal pedestal 5 which is sealed and joined to the optical member 4 .

The light emitting element 2 is an ultraviolet element that emits ultraviolet light with a wavelength of 400 nm or less, and preferably a deep ultraviolet element that emits deep ultraviolet light with a wavelength of 280 nm or less, which is highly effective in ultraviolet sterilization. Further, the light emitting element 2 may be, for example, a single chip in which a single LED structure is formed on a sapphire substrate, or an integrated chip in which a plurality of LED structures are formed on a sapphire substrate. May be present (example).

The substrate 3 is approximately square in plan view, and the base material 31 is, for example, a submount substrate in which a circuit is formed on aluminum nitride, and the circuit is formed according to the form of the light emitting element 2, for example, a flip chip. Examples include molds, wire bonding molds, and the like. Note that the illustrated example shows a configuration in which element bonding portions 32 subjected to metallization treatment are formed on a base material 31, and the light emitting element 2 is arranged so as to straddle the two element bonding portions 32. Further, a pedestal 5 is bonded to the peripheral edge of the substrate 3, and a metallized portion 33 is formed at this bonded portion, which is subjected to a metallization process such as gold plating or gold vapor deposition. An insulating portion exists between the element bonding portion 32 and the metallized portion 33.

The optical member 4 has a circular outer shape on the surface facing the substrate 3, and in the configuration shown in FIGS. A light emitting surface 42 from which light is emitted is a protruding dome lens (see also FIG. 6(a) to be described later). Although the illustrated example shows a configuration in which the light exit surface 42 has a spherical shape, it may be an aspherical surface. Note that the optical member 4 only needs to have a circular outer shape on the surface facing the substrate 3. For example, as in the modified example shown in FIGS. It may be a flat lens. Since the dome lens acts in a condensing manner, it is used in an ultraviolet element package suitable for devices in which the light (deep ultraviolet rays) emitted from the light emitting element 2 has a narrow distribution. On the other hand, since a flat lens does not act as a light condenser, it is used in an ultraviolet element package suitable for a device or the like in which the light (deep ultraviolet rays) emitted from the light emitting element 2 has a wide light distribution.

The optical member 4 is made of glass, for example, which has a softening point of 1000° C. or lower and, as shown in FIG. It is formed. The components of this glass are mainly SiO ₂ and B ₂ O ₃ and further includes, for example, Al ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, CaO, BaO, ZnO, Y ₂ O ₃ , Contains ZrO ₂ , La ₂ O ₃ , Sb ₂ O, etc.

As shown in FIGS. 4(a) to 4(c), the pedestal 5 is a plate-shaped metal member having a substantially rectangular outer shape in a plan view and having a predetermined thickness, into which the optical member 4 is fitted. It has an upper opening 51 that is circular in plan view, and a lower opening 52 that is approximately rectangular in bottom view, in which the light emitting element 2 mounted on the substrate 3 is accommodated. The pedestal 5 has a top surface, a bottom surface, and four side surfaces, and the edges formed by the adjacent side surfaces are chamfered to have a gentle roundness.

The upper surface opening 51 is formed by a cylindrical hole carved from the upper surface of the pedestal 5, and the lower surface opening 52 is formed by a substantially rectangular cylindrical hole carved from the bottom surface of the pedestal 5. The upper surface opening 51 and the lower surface opening 52 are connected at a position closer to the upper surface of the pedestal 5 than at a substantially mid-thickness position in a cross-sectional view. Further, in a plan view, the opening diameter of the upper surface opening 51 is approximately equal to the length of the diagonal line of the opening of the lower surface opening 52, and is shorter than the interval between the opposing sides of the opening of the lower surface opening 52. Therefore, between the upper surface side periphery of the lower surface opening 52 and the bottom surface side periphery of the upper surface opening 51, a holding portion 53 is formed which is made of a plane parallel to the upper surface and the bottom surface and holds the optical member. 4 on the light incident surface 41 side is supported by this holding portion 53 (see also FIG. 6(a)).

The pedestal 5 is made of metal having a coefficient of thermal expansion substantially equal to the coefficient of thermal expansion of the glass constituting the optical member 4 . The coefficient of thermal expansion of the glass and the pedestal 5 is, for example, about 4.5 x 10-6 K-1 at room temperature, and the material of the pedestal 5 is, for example, Korver with a thickness of about 0.1 to 0.2 mm. ) can be used. Kovar is an alloy of iron, nickel, cobalt, etc., and is a common material used for bonding hard glass. The melting point of Kovar is about 1450°C, which is higher than the melting point of glass. The substrate 3 and the optical member 4 are joined by welding the metal pedestal 5 and the metallized portion 33 at the peripheral edge of the substrate 3 using a metal preform 6. The metal preform 6 is a thin metal (alloy) containing noble metals such as gold and tin that is formed into the shape of the joint portion.

Next, a method for manufacturing the ultraviolet element package 1 will be described with reference to FIGS. 5 and 6. FIG. 5 shows a method of manufacturing the optical member 4 used in the ultraviolet element package 1 as the first step in the method of manufacturing the ultraviolet element package 1, and the manufacturing process of the optical member 4 integrally sealed with the pedestal 5. shows. Further, FIG. 6 shows a step of bonding the substrate 3 and the optical member 4 as the second step in the method of manufacturing the ultraviolet element package 1.

In the method for manufacturing the ultraviolet element package 1, the optical member 4 is compression-molded using a predetermined mold (jig) after glass is heated and melted or softened. As shown in FIG. 5A, a recess 21 corresponding to the lower opening 52 of the pedestal 5 is formed on the upper surface of the fixed jig 20. As shown in FIG. This recess 21 is carved in a large size so that its peripheral edge corresponds to the inner circumferential surface of the pedestal 5, and its central part is flat so as to be flush with the holding part 53 of the pedestal 5. The flat surface is transferred as the shape of the light entrance surface 41 of the optical member 4.

Then, as shown in FIG. 5(b), the pedestal 5 is fitted into the recess 21. Here, the pedestal 5 is subjected to oxidation treatment, and an oxide film is formed on its surface. The jig 20 is, for example, compression molded carbon powder into a predetermined shape as shown in the figure. Next, the glass supplied in the form of a rod is cut into glass pellets 10 of a predetermined size (predetermined volume or predetermined weight), and as shown in FIG. 5(c), the center of the pedestal 5 and the center of the glass pellet 10 are aligned. The glass pellet 10 is placed on the upper surface opening 51 of the pedestal 5 and the jig 20 so as to do so.

Next, as shown in FIG. 5(d), a jig 20 on which the pedestal 5 and the glass pellet 10 are placed, and a movable jig in which a recess 22 having a curved surface corresponding to the shape of the lens to be molded is formed. The components 23 are housed in the first heating furnace 40 and heated to a first temperature (for example, 1000° C.) higher than the softening point of glass in a nitrogen gas environment. Note that FIG. 5(d) depicts a state in which the glass pellet 10 is melted or softened. The jig 23 is also made by compression molding carbon powder into a predetermined shape as shown in the figure, and the jig 20 is made such that the center of the recess 21 of the jig 20 and the center of the recess 22 of the jig 23 coincide with each other. and a jig 23 are arranged, respectively.

When the glass pellet 10 is melted or softened to the extent that compression molding is possible, the movable jig 23 is gradually lowered toward the jig 20, as shown in FIG. The glass pellet 10 is deformed under pressure. As a result, the curved surface of the depression 22 is transferred to the surface of the molten glass pellet 10, and this becomes the light exit surface 42 of the optical member 4 (see FIG. 6(a)). In addition, when the glass pellet 10 is melted, the oxide film formed on the surface of the pedestal 5 improves the wettability between the pedestal 5 and the glass, improving the adhesion of the glass-metal interface, resulting in sealing (hermetic sealing). They are joined, and their boundary line becomes an airtight glass seal part GS. Note that the airtight glass seal portion GS itself has almost no thickness, and the airtight glass seal portion GS is exaggerated in FIG. 6(a) for the sake of explanation.

Next, after compression molding the optical member 4 by pressing the jig 23 against the jig 20 for a predetermined time and under a predetermined pressure, the temperature in the first heating furnace 40 is lowered, and the jig 20, the jig 23, and the molded The optical member 4 and the pedestal 5 are cooled. Here, as described above, since the material of the pedestal 5 and the coefficient of thermal expansion of the optical member 4 are substantially the same, the optical member 4 and the pedestal 5 contract at substantially the same rate during cooling. Therefore, the optical member 4 and the pedestal 5 are not separated, and the optical member 4 and the pedestal 5 are integrally sealed and joined even after cooling. After cooling to room temperature, the jig 20, the jig 23, the optical member 4, and the pedestal 5 are taken out from the first heating furnace 40, and the jig 23 is separated from the jig 20. Thereby, as shown in FIG. 5(f), the optical member 4 and the pedestal 5 which are sealed and bonded are obtained.

Here, in the ultraviolet element package 1 of the present embodiment, the optical member 4 has a circular outer shape on the surface facing the substrate 3, and the pedestal 5 has a circular upper surface in plan view into which the optical member 4 is fitted. It has an opening 51. That is, the airtight glass seal portion GS, which is the boundary line between the pedestal 5 and the glass, becomes circular. Therefore, when placing a disk-shaped (cylindrical) glass pellet on the oxidized pedestal 5 (jig 20) and melting and joining the glass, if the top opening 51 is circular, the glass spreads out in a radial manner. By pulling and holding it evenly, a glass of uniform thickness is formed. This can be easily imagined from the fact that the bodies of submarines and aircraft are designed to be round in order to withstand water and atmospheric pressure. If the top opening 51 is not circular, for example, square, even if a glass pellet processed to have a square cross section is used, the glass will not be pulled uniformly when melted, so the thickness of the glass will vary. This may cause unevenness and holes in the airtight glass seal. On the other hand, in this embodiment, since the upper surface opening 51 of the pedestal 5 is circular, the glass is molded to have a uniform thickness, and an airtight glass seal part GS having no holes and high sealing performance can be obtained.

The airtight glass seal portion GS is formed at the boundary between the inner surface of the upper surface opening 51 of the pedestal 5 and the outer surface of the optical member 4 in contact with the inner surface. Further, in the present embodiment, since the pedestal 5 is provided with the holding portion 53 between the upper surface side periphery of the lower surface opening 52 and the bottom surface side periphery of the upper surface opening 51, the airtight glass seal portion GS is It is also formed at the boundary between the top surface of the holding portion 53 and the bottom surface of the optical member 4. That is, since the airtight glass seal portion GS is formed not only on the vertical surface along the inner surface of the upper surface opening 51 but also on the horizontal surface along the holding portion 53, the sealing performance can be further improved. Further, since the optical member 4 is supported by the holding portion 53, even if the optical member 4 is pressed from the outside, the optical member 4 will not be pushed toward the light emitting element 2 side, and durability can be improved.

Further, the optical member 4 and the pedestal 5 are housed in a separate heating furnace (not shown), and the temperature is higher than the softening point of glass and lower than the first temperature (for example, 1000° C.) in an oxygen-containing air environment. Preferably, it is reheated to a second temperature (eg 800°C). By this reheating treatment, the surface of the optical member 4, which is textured by transferring the carbon powder, is remelted or softened again, and the molten or softened glass moves from the convex portion to the concave portion due to surface tension, and the optical member The unevenness of the surface of 4 is gradually leveled and smoothed. That is, by thermally polishing the surface of the lens through a simple reheating process, the surface of the lens can be given a mirror finish.

After the optical member 4 and the pedestal 5 are bonded, the oxide film on the surface of the pedestal 5 that is not bonded to the glass is cleaned and removed. Furthermore, the pedestal 5 made of Kovar is plated with nickel to prevent rust, and further plated with gold for bonding to the substrate 3. Note that these plating treatments are performed after the pedestal 5 is sealed and joined to the optical member 4, but since the optical member 4 made of glass is an insulator, no plating is applied to the surface of the optical member 4. . However, since the optical member 4 is also immersed in the plating solution, the glass constituting the optical member 4 is preferably one with high chemical resistance, such as one with excellent acid resistance. The optical member 4 joined to the pedestal 5 can be independently manufactured and sold commercially, and the joining process with the substrate 3 described below may be performed by a manufacturer different from the manufacturer of the optical member 4. may be done.

Next, as shown in FIG. 6(a), a substrate 3 on which a light emitting element 2 is mounted is prepared, and this substrate 3 and an optical member 4 sealed and bonded to a pedestal 5 formed in the above-described process are combined. A metal preform 6 made of an alloy containing a noble metal such as gold/tin or gold/germanium is placed between the metal preforms 6 and positioned so that the metallized portion 33 on the substrate 3 side and the lower surface of the pedestal 5 are in close contact with each other. Make adjustments. Then, as shown in FIG. 6(b), the substrate 3, metal preform 6, and optical member 4 are heated in a second heating furnace 50 to a temperature higher than at least the melting temperature of the metal preform 6 (200 to 400°C). Heat to temperature and weld them. Then, by cooling the metal preform 6 to a temperature below the melting temperature, the metal preform 6 is hardened, and the pedestal 5 integrated with the optical member 4 and the metallized portion 33 of the peripheral wall of the substrate 3 are formed. Bonded using inorganic material (preform).

The pedestal 5 is integrally and sealingly bonded to a portion of the lower surface of the optical member 4 on the side facing the substrate 3 that is bonded to the metallized portion 33 of the substrate 3 . Therefore, when the lower surface of the pedestal 5 and the metallized portion 33 of the substrate 3 are closely bonded by the metal preform 6, the lower surface opening 52 of the substrate 3, the pedestal 5, and the light incident surface 41 of the optical member 4 form a The space is sealed and isolated from the outside world. As a result, the deep ultraviolet light emitted from the light emitting element 2 does not leak through the gap between the joint between the substrate 3 and the optical member 4, preventing gas, moisture, etc. from entering from the outside, and protecting the light emitting element 2. , the product life can be extended. Moreover, resin products and the like existing around the ultraviolet element package 1 are not adversely affected.

By the way, in the manufacturing process of the optical member 4 integrally joined to the pedestal 5 shown in FIG. 5, the jig 20 and the jig 23 are each formed by compressing carbon powder. Therefore, the shape of the minute carbon powder is transferred to the surface of the optical member 4 molded in FIG. 5(f), resulting in a textured surface, giving the surface a so-called matte finish. . Further, there may be cases where peeled carbon powder adheres to the surface of the optical member 4. Therefore, after the step shown in FIG. 5(f), a cleaning step may be provided to clean the surface of the molded optical member 4 and remove the attached carbon powder. Specifically, the surface of the optical member 4 is cleaned using hydrochloric acid, hydrogen fluoride water, deionized water, or the like. In order to polish the surface of the optical member 4 after cleaning, it is desirable to heat it again to melt the surface and perform thermal polishing (not shown).

Note that if it is desired to diffuse and irradiate the deep ultraviolet rays emitted from the light emitting element 2, it may be better for the surface of the optical member 4 to remain uneven. In that case, by discontinuing the thermal polishing shown in FIG. 5(f), the surface will remain uneven.

As explained above, according to the present invention, glass having a softening point of 1000° C. or less and an average transmittance of 80% or more for light with a wavelength of 250 to 400 nm is used, and a jig is used to attach the molten or softened glass pellet 10 to the glass pellet 10. Since the optical member 4 is pressure-molded by pressing 23, the number of manufacturing steps is small and the process itself is simple. Further, since the pedestal 5 is integrally joined to the optical member 4 at the same time as the optical member 4 is molded, masking and vapor deposition steps for metallization processing are not necessary. Furthermore, since the joint surfaces of the pedestal 5 integrated with the optical member 4 and the metallized portion 33 of the metallized peripheral wall of the substrate 3 are metal, the use of the metal preform 6 makes it easy to It can be bonded with an inorganic material (preform), which further simplifies the manufacturing process. As a result, a highly reliable ultraviolet device package 1 can be provided at low cost. Furthermore, the material of the glass is not limited to those exemplified above, and even if the transmittance to deep ultraviolet rays with shorter wavelengths (e.g. 265 nm) is lower than 80%, it still has a practically sufficient transmittance (e.g. 70%). above).

1 UV element package 2 Light emitting element 3 Substrate 33 Metallized part 4 Optical member (dome lens, flat lens)
42 Light exit surface 5 Pedestal 51 Top opening 52 Bottom opening 53 Holding part 6 Metal preform

Claims (6)

An ultraviolet element package comprising a light emitting element that emits ultraviolet light, a substrate on which the light emitting element is mounted, and an optical member provided at a position facing the light emitting element,
The optical member is made of glass having a softening point of 1000° C. or less and an average transmittance of 80% or more for light with a wavelength of 250 to 400 nm. is bonded to the substrate by
The pedestal has an upper opening that is circular in plan view into which the optical member is fitted, and a lower opening that is approximately rectangular in bottom view and in which the light emitting element is housed .
A holding part is formed between the top side periphery of the bottom opening and the bottom side periphery of the top opening, and is made of a plane parallel to the top and bottom surfaces of the pedestal and holds the optical member. A UV element package featuring: 2. The ultraviolet device package according to claim 1, wherein the pedestal is made of metal having a coefficient of thermal expansion substantially equal to a coefficient of thermal expansion of the glass. 3. The ultraviolet device package according to claim 1, wherein the pedestal is sealingly bonded to the optical member by an oxide film formed on the surface of the pedestal. A metallized portion subjected to metallization treatment is formed at a joint portion of the substrate with the pedestal,
The ultraviolet device package according to any one of claims 1 to 3, wherein the pedestal and the metallized portion are joined by a metal preform. The ultraviolet element package according to any one of claims 1 to 4, wherein the optical member is a dome lens with a protruding light exit surface . The ultraviolet device package according to any one of claims 1 to 5, wherein the optical member is a flat lens having a flat light exit surface.

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