SEALING LID FORMED FROM TRANSLUCENT MATERIAL

Abstract

The present invention relates to a sealing lid for a package containing an optical element. For the sealing lid, a translucent material such as glass that can transmit light such as visible light is used. The present invention includes a lid main body made of the translucent material. The lid main body includes a joining region having a frame shape corresponding to an outer circumferential shape of the lid main body. A plurality of pieces of brazing material made of a eutectic alloy are fused on the joining region of the lid main body. An arrangement state of the brazing material includes aligning spherical pieces of brazing material continuously to form a frame shape along the joining region.

Claims

1. A sealing lid that is joinable to a package main body containing an optical element and that is for producing a package hermetically sealed, the sealing lid comprising a lid main body comprising a translucent material through which at least one of visible light, ultraviolet light, and infrared light is transmittable, wherein the lid main body comprises a joining region having a frame shape corresponding to an outer circumferential shape of the lid main body, the joining region being formed on a surface of the lid main body that is to be joined to the package main body, and wherein a plurality of pieces of brazing material comprising a eutectic alloy are fused on the joining region of the lid main body.

2. The sealing lid according to claim 1, wherein the plurality of pieces of brazing material are continuously fused on the joining region to form a frame shape.

3. The sealing lid according to claim 1, wherein a material structure of a random cross section of at least one of the plurality of pieces of brazing material comprises a eutectic structure and optionally comprises a single phase having an equivalent circle diameter of equal to or less than 5 m.

4. The sealing lid according to claim 1, wherein at least one of the plurality of pieces of brazing material has a substantially circular projected shape.

5. The sealing lid according to claim 1, wherein at least one of the plurality of pieces of brazing material has a shape index (I.sub.s) that is equal to or larger than 0.9 and equal to or less than 2.5, the shape index (I.sub.s) being defined by a formula:
shape index(I.sub.s)=A.sup.1/2/V.sup.1/3,[Formula 1] where A represents a joining area between the lid main body and the brazing material (mm.sup.2), and V represents a volume of the brazing material (mm.sup.3).

6. The sealing lid according to claim 1, wherein the translucent material of the lid main body comprises at least one of glass, crystal, sapphire, silicon, and germanium.

7. The sealing lid according to claim 1, wherein the brazing material comprising the eutectic alloy is a Au-based eutectic brazing material.

8. The sealing lid according to claim 1, wherein the brazing material comprising the eutectic alloy is a AuSn brazing material.

9. The sealing lid according to claim 1, wherein a metallized film comprising at least one layer comprising metal is provided on at least a part of the lid main body surface, and the brazing material is fused on the metallized film.

10. The sealing lid according to claim 9, wherein the metallized film comprises a first metal layer comprising at least one of Au and Pt on a brazing material fused surface of the metallized film.

11. The sealing lid according to claim 9, wherein the metallized film comprises a second metal layer comprising at least one of Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Sb, Ta, W, Re, Os, and Ir on a surface of the lid main body.

12. The sealing lid according to claim 9, wherein a diffusion region formed by diffusion of a metal element of the metallized film into the brazing material has a width of equal to or less than 2 m.

13. The sealing lid according to claim 1, wherein the lid main body comprises a function film on one surface or both surfaces of the lid main body, the function film being for increasing transmittance or reflectance.

14. A hermetic sealing method comprising joining a sealing lid to a package main body, wherein the sealing lid joined is the sealing lid according to claim 1.

15. A package comprising the sealing lid according to claim 1.

16. The sealing lid according to claim 2, wherein a material structure of a random cross section of at least one of the plurality of pieces of brazing material comprises a eutectic structure and optionally comprises a single phase having an equivalent circle diameter of equal to or less than 5 m.

17. The sealing lid according to claim 2, wherein at least one of the plurality of pieces of brazing material has a substantially circular projected shape.

18. The sealing lid according to claim 3, wherein at least one of the plurality of pieces of brazing material has a substantially circular projected shape.

19. The sealing lid according to claim 2, wherein at least one of the plurality of pieces of brazing material has a shape index (I.sub.s) that is equal to or larger than 0.9 and equal to or less than 2.5, the shape index (I.sub.s) being defined by a formula:
shape index(I.sub.s)=A.sup.1/2/V.sup.1/3,[Formula 1] where A represents a joining area between the lid main body and the brazing material (mm.sup.2), and V represents a volume of the brazing material (mm.sup.3).

20. The sealing lid according to claim 3, wherein at least one of the plurality of pieces of brazing material has a shape index (I.sub.s) that is equal to or larger than 0.9 and equal to or less than 2.5, the shape index (I.sub.s) being defined by a formula:
shape index(I.sub.s)=A.sup.1/2/V.sup.1/3,[Formula 1] where A represents a joining area between the lid main body and the brazing material (mm.sup.2), and V represents a volume of the brazing material (mm.sup.3).

Description

BRIEF DESCRIPTION OF DRAWINGS

[0058] FIG. 1 illustrates joining region examples in a lid main body according to the present invention.

[0059] FIG. 2 illustrates arrangement examples of a plurality of brazing material fused on the lid main body according to the present invention.

[0060] FIG. 3 illustrates a relationship between a shape index (I.sub.s) and a shape/dimension of the brazing material fused on the lid main body.

[0061] FIG. 4 illustrates examples of the shape (semispherical shape, stacked shape) of the brazing material fused on the lid main body.

[0062] FIG. 5 illustrates a configuration of a brazing material ejection device (process a) for fusing the brazing material.

[0063] FIG. 6 illustrates positions where the brazing material is fused by means of the brazing material ejection device (process a)

[0064] FIG. 7 illustrates external views of the brazing material fused by means of the brazing material ejection device (process a)

[0065] FIG. 8 illustrates an external view of ball shaped pieces of brazing material fused in a process b.

[0066] FIG. 9 illustrates a material structure of a brazing material (No. A4) fused in the process a.

[0067] FIG. 10 illustrates a material structure of a brazing material fused in the process b.

[0068] FIG. 11 illustrates a material structure of a brazing material (No. C2) fused in a process c.

MODES FOR CARRYING OUT THE INVENTION

[0069] The following describes an embodiment of the present invention. In this embodiment, a lid main body was made of quartz glass, which is a translucent material. To this lid main body, a AuSn brazing material, which is a brazing material of a eutectic alloy, was fused using various methods to produce a sealing lid. The lid thus produced was tested for its joining performance relative to a package main body to evaluate whether the lid main body was damaged. The lid also underwent a sealing test to confirm its airtightness performance.

[0070] The lid main body used in this embodiment is a flat plate (3.4 mm3.4 mm with a thickness of 0.3 mm) made of quartz glass or borosilicate glass. In this embodiment, a metallized film was formed in a frame region (outer size: 3.2 mm3.2 mm, inner size: 2.5 mm2.5 mm) on the surface of the glass lid main body.

[0071] The metallized film was formed by providing thin films of metals Cr (60 nm)/Ni (200 nm)/Au (100 nm) in this order from the lid main body surface. In some examples, a metallized film formed by providing Ti (60 nm)/Pt (200 nm)/Au (100 nm) in this order was used.

[0072] To the glass lid main body prepared as described above, a brazing material was fused. As the brazing material, a Au-22% by mass Sn brazing material was used. In this embodiment, the brazing material was fused to the lid main body to produce a lid by the following three different processes a to c.

[0073] Process a: In this process, the brazing material was fused with the use of a brazing material ejection device containing pre-molten brazing material to produce a lid. FIG. 5 illustrates a detailed configuration of this brazing material ejection device 101. The ejection device 101 includes: a tank 110, which contains a brazing material 201 and is kept at a controlled temperature so as to maintain the material in molten state; a chamber 111, which communicates with the tank 110; a diaphragm 112 and an aperture 113, which are for ejecting the brazing material 201 contained in the chamber 111; and a piezoelectric actuator 114, which drives the diaphragm 112.

[0074] In the fusing of the brazing material using this ejection device 101, the piezoelectric actuator 114 is controlled and driven by a computer to cause a fixed amount of the brazing material 201 in the chamber 111 to be ejected through the nozzle. By controlling the size of the aperture 113 and the drive amount and change rate of the piezoelectric actuator 114, the volume and airborne speed of the ejected brazing material 202 is adjusted. The lid main body is placed on a stage that is movable in the X, Y, and Z directions. By driving this stage, the brazing material can be fused continuously in a frame shape on the lid main body.

[0075] In this embodiment, as illustrated in FIG. 6, the brazing material was fused continuously in a row along the center position of the frame shaped metallized film, thereby shaping the brazing material into a frame. In this embodiment, in this process a, the size of molten metal droplets ejected was set to 0.1 mm or 0.125 mm in terms of sphere diameter, and the airborne speed of the brazing material was set to 1.6 m/second or higher. In addition, the number of pieces of the brazing material fused was calculated so that the thickness of the brazing material layer joined to the package main body would range from 10 to 25 m, and the pieces were placed on the lid main body at substantially equal intervals. It is to be noted that the temperature of the stage on which the lid main body was place was set to normal temperature. FIG. 7 illustrates an example external view of the lid produced by fusing the brazing material in this process a.

[0076] Process b: In this process, small blobs (ball shapes) of solid brazing material produced in advance were fused to the lid main body. In this embodiment, ball-shaped pieces of the brazing material having a diameter of 0.1 mm were placed on a frame shaped metallized film on the lid main body at substantially equal intervals. In this process, a carbon jig having 0.15-mm holes arranged in a frame shape was superimposed on the lid main body, and ball shaped pieces of the brazing material were sequentially inserted into the respective holes of the jig. Then, with the jig superimposed on the lid main body without displacement, the brazing material was fused through heating the brazing material for 1 minute or longer at 320 C. in an electric furnace of non-oxidizing atmosphere. In this process b, a lid on which the brazing material was placed similarly to the process a was produced. FIG. 8 illustrates an example external view of the lid produced by fusing the brazing material in the process b.

[0077] Process c: In this process, a piece of brazing material processed in a frame shape in advance was fused to the lid main body to produce a lid. This process serves as a comparative example relative to the above-described processes a and b. First, a Au-22% by mass Sn brazing material was punched out into a rectangular frame shape (outer size: 3.15 mm3.15 mm, inner size: 2.5 mm2.5 mm, thickness: 15 m, 25 m). Then, this preformed brazing material was placed on the lid main body, and reflowed and fused at 305 C. in a non-oxidizing atmosphere.

[0078] Based on the methods of the above-described processes a to c, pieces of brazing material having various shapes and dimensions were fused to a glass lid main body to produce sealing lids. For each type, ten sealing lids were produced. The sealing lids after the fusing step were examined for any break, cracking, or the like in the lid main body visually and under an optical microscope, and the number of non-defective products out of 10 was counted for evaluation in terms of proportion (non-defective rate).

[0079] Also, a material structure on a random cross section of the brazing material was observed. For structure observation of the lids produced in the processes a and b, pieces of brazing material were randomly selected; the lid main body was cut in the vicinity of the selected piece of brazing material and embedded with resin; the lid main body was polished as appropriate to make the cross section of the brazing material exposed; and the cross section was subjected to an observation. For the lids produced in the process c, the lid was cut at an arbitrary position on the lid and embedded with resin, and then polished as appropriate to observe the material structure on the cross section of the brazing material.

[0080] In the observation of the material structure, first, the entire cross section of the brazing material was observed to see if there was any eutectic structure or single phase. Then, a main part of the cross section was magnified to measure the size of the single phase. In this embodiment, a eutectic structure was observed in all of the brazing materials fused in the processes a to c. For the processes b and c, some solid phases were observed to be clearly coarser than the solid phase constituting the eutectic structure. The equivalent circle diameter of the single phase was calculated based on an image magnified by 1500 to 2500 times obtained through SEM (acceleration voltage 15 kV). In a case where a plurality of single phases were observed, the average value of these was calculated. In a case where no solid phase identified as a single phase was clearly observed, in other words, for the brazing material with which only a eutectic structure was substantially observed, magnified images of arbitrary portions were obtained; five solid phases were randomly extracted from the images; their equivalent circle diameters were determined; it was confirmed that none of them exceeded 5 m; and it was confirmed that the equivalent circle diameter of the single phase was 5 m or less. It is to be noted that the equivalent circle diameter refers to the diameter of a circle having the same area as the observed single phase.

[0081] The width of the region where metallized film components were diffused in the brazing material was also measured. This measurement was carried out through observing the interfaces of the samples used in the cross-section observation with the metallized film of the brazing material through EPMA (electron-beam microprobe analysis) and conducting an elemental analysis. The analysis conditions for EPMA were an acceleration voltage of 20 kV and a measurement magnification of 5000. In this elemental analysis, a line analysis was performed from the inside of the metallized film toward the inside of the brazing material. Then, the count of the metal components (Ni, Pt) in the metallized film was assumed as 100%. Based on this assumption, the count of these components decreasing toward the brazing material was tracked. The point at which the count of the components dropped to 10% or less was determined to be an edge of the diffusion region. Then, the distance between the interface and the edge of the diffusion region was determined to be the width.

[0082] Furthermore, for each lid produced, the shape index (I.sub.s) of the fused brazing material was measured. In the measurement of the shape index, for the brazing material used for the lids produced in the processes a and b, the brazing material was peeled off the lids produced, and the average value of volumes based on the mass of the brazing material collected and the density and the number of pieces of brazing material was determined as the volume (V) of a piece of brazing material. As for the joining area (A) of the brazing material, the lid main bodies from which the brazing materials were peeled off were observed under a microscope; areas of the joining surfaces were measured; and the average of them was obtained. For the brazing material used for the lids produced in the process c, the volume (V) was determined from the dimensions of the pre-fused brazing material. Furthermore, the joining area (A) was calculated by measuring the profile of the post-fused brazing material.

[0083] Table 1 lists: observation and measurement results of material structures, shapes, and dimensions of the brazing materials sorted by the production processes for the sealing lids produced according to this embodiment; and occurrence of damage in the lid main bodies.

TABLE-US-00001 TABLE 1 Material structure Number Single phase Brazing material shape of equivalent Joining Shape Diffusion Fused non- Production Lid main brazing Metallized circle area Volume V index region defective No. process body material film diameter (10.sup.3mm.sup.2) (10.sup.3mm.sup.3) (I.sub.s) (m) rate A1 a quartz glass 56 Cr/Ni/Au 5 m or 3.74 0.57 0.7 0.5 9/10 less A2 5 m or 6.23 0.59 0.9 0.5 10/10 less A3 5 m or 12.47 0.52 1.4 0.5 10/10 less A4 5 m or 18.70 0.55 1.7 0.5 10/10 less A5 borosilicate Ti/Pt/Au 5 m or 21.75 0.55 1.8 0.5 10/10 glass less A6 quartz glass 112 Cr/Ni/Au 5 m or 13.64 1.04 1.2 0.5 10/10 less A7 5 m or 23.38 1.07 1.5 0.5 10/10 less A8 5 m or 48.70 1.10 2.1 0.5 10/10 less A9 144 5 m or 68.18 1.04 2.6 0.5 9/10 less B1 b quartz glass 56 Cr/Ni/Au 5.8 m 14.85 0.52 1.5 0.5 10/10 B2 8.8 m 17.67 0.53 1.6 0.5 10/10 B3 11.2 m 41.55 0.52 2.5 1.0 10/10 B4 15 m 57.26 0.53 3.0 2.0 9/10 C1 c quartz glass 1 Cr/Ni/Au 2.4 m 3964 39.64 5.8 1.0 6/10 C2 8.5 m 3964 79.28 4.6 3.0 2/10 Production process Process a: droplets of molten brazing material (ejection device) Process b: ball shaped brazing material Process c: frame shaped preformed brazing material (C1: 15 m thick, C2: 25 m thick)

[0084] As can be seen from Table 1, the occurrence of damage in the lid main bodies was extremely limited in the lids to which spherical pieces of brazing material were continuously fused with the use of the ejection device in the process a (Nos. A1 to A9). In particular, as for the lids of Nos. A2 to A8, the post-fused brazing material had shape indices of 0.9 to 2.1, and all the lid produced were determined to be non-defective (fused non-defective rate: 10/10). By contrast, as for the lids of Nos. A1 and A9, the post-fused brazing material had shape indices of 0.7 and 2.6, and damage was observed in some of the post-fused lid main bodies.

[0085] FIG. 9 illustrates an example cross sectional structure of the brazing material (No. A4) after the molten brazing material was fused in the process a. Almost the entirety of the brazing material fused to the lid main bodies according to this embodiment had a fine eutectic structure. The brazing material fused in the process a is expected to be less likely to include a coarse single phase. In the brazing materials fused in the process a, a single phase was identified based on the measurement criteria described above, with the result that the equivalent circle diameter was constantly 5 m or less.

[0086] For the lids to which the brazing material was fused in the process b, the brazing material has a similar shape to that of the brazing material in the process a, but has a different material structure. FIG. 10 illustrates the material structure of the brazing material (No. B2) fused in the process b. It was confirmed that, in addition to a eutectic structure, a single phase not belonging to the eutectic structure was generated. Since a AuSn brazing material was used in this embodiment, this single phase is presumably a 6 phase or phase. The measurement results of the particle diameter of the single phase in Table 1 show that the brazing material for the lids produced in the process b tends to generate a single phase, in addition to a eutectic structure. In the method for fusing the brazing material in the process b, the entire lid needs to be heated with the brazing material inserted in the jig, which requires a longer period of cooling time. This is presumably why the single phase is generated and grown.

[0087] It should be noted that the process b is a process by which the shape of the brazing material can be controlled. As for the lids in Nos. B1, B2, and B3, the brazing material successfully achieved shape indices of 1.5 to 2.5. Since no damage was observed in the lid main bodies, they can be presumably used for sealing packages. By this process b, a plurality of ball shaped small masses of brazing material can be fused, and thus the occurrence of damage in the lid main bodies during the fusing can be reduced.

[0088] It can be seen that compared with the examples of these processes a and b, the pieces of brazing material (Nos. C1 and C2) preformed in a frame shape in the process c tend to case cracking in the glass lid main body in the fusing process. These pieces of brazing material had large shape indices (I.sub.s) ranging from 4.6 to 5.8. Such large shape indices (I.sub.s) are because of an excessively large joining area for the preformed brazing material in a frame shape. Since brazing materials are different from glass in thermal expansion/contraction behavior, a larger joining area results in a larger residual stress when the brazing material is cured. Brazing materials having a large joining area like this brazing material in a frame shape relatively tend to have cracking due to residual stress.

[0089] Regarding the material structure of the preform brazing material in a frame shape, it is considered to be difficult to produce a preferable material structure having only a eutectic structure. FIG. 11 illustrates a cross sectional structure of the brazing material after the preform brazing material (brazing material thickness 25 m) of No. C2 was fused. It was observed that a small region of the material structure of this brazing material was occupied by the eutectic structure, and the rest of the material structure was occupied by a large number of coarse single phases having a particle diameter exceeding 5 m in terms of equivalent circle diameter. In this process, while the brazing material is being fused, the lid main body is heated together with the brazing material by reflow. This elongates the time during which the temperature of the brazing material exceeds the melting point, making the cooling speed lower. This presumably made it easier for single phases to be deposited. This preform brazing material in a frame shape caused damage in the lid main body in the fusing step and thus was unusable for the subsequent sealing test. Even if cracking is small enough to endure the sealing test, it is likely that the coarse single phase would affect the airtightness.

[0090] Next, a sealing test using package main bodies were performed with respect to the lid main bodies produced in the processes a and b, in which no significant damage occurred after the brazing material was fused. In this sealing test, ceramic package main bodies (having opening dimensions (inner size) of 2.4 mm2.4 mm and an opening edge end surface thickness of 0.8 mm) were prepared, and various sealing lids were joined to the package main bodies. In the package production method, each lid was superimposed on the corresponding package main body and positioned; the package was heated to 305 C. under a loading condition of 0.4 MPa; and the brazing material was re-melted. In this process, the set temperature was retained for 30 seconds, and upon elapse of the time, the heating was immediately stopped and cooling was started. After the package was sealed, the glass lid was examined under a stereoscopic microscope (20 times) for occurrence of cracking in the glass lid. In this evaluation, a parameter used was the number of lid main bodies (10 pieces) in the fusing step of the brazing material described above. In other words, those products that were damaged in the lid main bodies during the fusing of the brazing material were determined to be defective without subjecting them to the sealing test. The sealing test was conducted on those products determined as non-defective after the fusing of the brazing material, and the non-defective rate was evaluated.

[0091] Furthermore, those packages with no cracking in sealed lids were evaluated for airtightness, and the non-defective occurrence rate from the lid production step (brazing material fusing step) to the package production step (sealing step) was evaluated. The airtightness was evaluated through immersing the packages in a Fluorinert liquid heated to 120 C. and visually checking the generation of air bubbles from the inside of the packages. In this airtightness evaluation as well, a parameter used was the number of lid main bodies in the fusing step of the brazing material. The results of the sealing test are listed in Table 2.

TABLE-US-00002 TABLE 2 Material structure Single phase Shape equivalent index Diffusion Sealing-time Airtightness Production circle (I.sub.s) region non-defective non-defective No. process diameter 0.7 (m) rate rate A1 a 5 m or 0.7 0.5 9/10 8/10 less A2 5 m or 0.9 0.5 10/10 10/10 less A3 5 m or 1.4 0.5 10/10 10/10 less A4 5 m or 1.7 0.5 10/10 10/10 less A5 5 m or 1.8 0.5 10/10 10/10 less A6 5 m or 1.2 0.5 10/10 10/10 less A7 5 m or 1.5 0.5 10/10 10/10 less A8 5 m or 2.1 0.5 10/10 10/10 less A9 5 m or 2.6 0.5 9/10 8/10 less B1 b 5.8 m 1.5 0.5 8/10 6/10 B2 8.8 m 1.6 0.5 9/10 5/10 B3 11.2 m 2.5 1.0 8/10 7/10 B4 15 m 3.0 2.0 7/10 5/10 Production process Process a: droplets of molten brazing material (ejection device) Process b: ball shaped brazing material (jig arranged)

[0092] The results of the non-defective rate evaluation in the sealing process show that the process a is superior to the process b. This is presumably because of the 5 m or larger coarse single phases generated in the brazing material in the process b. Because of the generation of coarse single phases in the brazing material in the process b, a partial composition change occurred. This presumably caused the melting point to vary, resulting in formation of a region where the brazing material was not completely molten and not caused to flow.

[0093] The results of non-defective rate evaluation in terms of airtightness show that the process a is superior to the process b. This is also presumably because of the coarse single phases generated in the process b. Because of the generation of coarse single phases, a high melting point region was generated, which presumably caused a leak path to be generated. Thus, in order to produce the most effective lid both in the lid production step (fusing of the brazing material) and the package production step (re-melting and curing of the brazing material for sealing), it is preferable to optimize the composition and shape of the brazing material and use a suitable material structure.

INDUSTRIAL APPLICABILITY

[0094] As has been described hereinbefore, the sealing lid according to the present invention uses a translucent material such as glass for the sealing lid, and uses a brazing material made of a eutectic alloy as a joining material for sealing. The use of each material has its own advantages. The present invention provides a package containing an optical element with effective efficiency of utilization of light and high durability. The present invention is suitable for sealing materials for various devices that use optical elements including light emitting elements such as LEDs and light receiving elements.