Electrical element mounting board and method for manufacturing board

Abstract

To provide an electric element mounting board having high bonding quality between a lid and the board, and a method for manufacturing the board.SOLUTION: In an electric element mounting board 100 for mounting an electric element 20 on the upper surface 12b of a protruding portion 12 protruding upward from the main surface of the board 10 and bonding a lid 30 covering the electric element 20 onto the main surface, the main surface to which the lid 30 is bonded is a mirror surface. The board 10 is manufactured by a step of forming an annular groove portion 201 on one main surface of a first board 200, a step of mirror-finishing one main surface of a second board 300, a step of bonding the first board 200 with the groove 201 formed thereon to the second board 300, and a step of removing the other main surface of the first board 200 until the groove portion 201 is opened.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electric element mounting board having a mounting portion for mounting an electric element, and a method for manufacturing the board. [Background technology]

[0002] An electric element mounting package is one in which an electric element is mounted on an electric element mounting board having a flat substrate and a pedestal protruding upward from the surface of the substrate, and a lid is attached to the electric element mounting board (see, for example, Patent Document 1). In this electric element mounting package, the electric element is mounted on the upper surface of the pedestal of the electric element mounting board, and the lid is attached to the surface of the electric element mounting board so as to cover the pedestal and the electric element mounted on the pedestal.

[0003] Patent Document 1 discloses a method for manufacturing a substrate for mounting electrical elements, in which a ceramic green sheet is pressed to form a convex portion corresponding to a base and a substrate surface surrounding the convex portion to which a lid is attached, and then the green sheet is fired. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-110262 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a package for mounting an electric element, in a light-emitting device mounting a light-emitting element, etc., in order to improve the reliability of the light-emitting device, it is required to hermetically seal the area sealed by the lid. However, in a conventional method for manufacturing a substrate for mounting an electric element, in which a green sheet is pressed and then fired, the surface roughness of the substrate surface to which the lid is attached may cause the bonding quality between the substrate and the lid to be insufficient. The bonding quality here refers to the airtightness and bonding strength of the region sealed by the lid. In addition, in the manufacture of a substrate having a three-dimensional structure in which a convex portion is formed, it is possible to form the substrate surface around the convex portion by laser processing, blast processing, machining processing, etc., but all processing methods have the same problem.

[0006] In view of the above problems, an object of the present invention is to provide an electric element mounting board having high bonding quality between the board and the lid, and a method for manufacturing the board. [Means for solving the problem]

[0007] The electric element mounting substrate is for mounting an electric element on the upper surface of a convex portion protruding upward from a main surface of the substrate and joining a lid body covering the electric element to the main surface, the main surface to which the lid body is joined being a mirror surface. The upper surface of the protrusion may be a mirror surface, and the side surface of the protrusion may be a rough surface. The method for manufacturing a substrate includes the steps of forming a ring-shaped groove on one main surface of a first substrate, mirror-finishing one main surface of a second substrate, joining the one main surface of the first substrate on which the groove is formed to the one main surface of the second substrate that has been mirror-finished, and removing the other main surface of the first substrate until the groove is open. This substrate manufacturing method may further include a step of forming a first metal layer on one main surface of the first substrate surrounded by the groove portion, and a step of forming a second metal layer on one main surface of the second substrate which has been mirror-finished, and the step of bonding the first substrate and the second substrate may be a step of bonding the first metal layer and the second metal layer. The step of removing and processing the other surface of the first substrate may be a step of making the removed surface of the first substrate into a mirror surface. Effect of the Invention

[0008] According to the electric element mounting board and the method for manufacturing the board of the present invention, it is possible to provide a board with high bonding quality between the lid and the board. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram for explaining an electric element mounting board according to one embodiment of the present invention, and is a cross-sectional view of a light emitting device in which a light emitting element is mounted on the electric element mounting board. [Diagram 2] 1A to 1C are schematic diagrams illustrating a method for manufacturing a substrate according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The electric element mounting board and the manufacturing method thereof according to the present invention will be described below with reference to the drawings. In the drawings, the scale and number of each structure may differ from the actual shape and structure in order to make each component easier to understand.

[0011] First, the electric element mounting board according to the present invention will be described. Fig. 1 is a diagram for explaining the electric element mounting board according to one embodiment of the present invention, and is a cross-sectional view of a light emitting device in which a light emitting element is mounted on the electric element mounting board. The light emitting device 100 comprises an electric element mounting board 10 (hereinafter referred to as substrate 10), a light emitting element 20 mounted on the substrate 10, and a lid 30 that seals the light emitting element 20.

[0012] The substrate 10 includes a base 11 and a protrusion 12 disposed on a main surface 11a of the base 11 and in the center of the main surface 11a. The base 11 is a plate-like member made of aluminum nitride, with a length and width of 4 mm and a thickness of 2 mm, and the protrusion 12 is a plate-like member made of aluminum nitride, with a length and width of 2 mm and a thickness of 0.5 mm. The protrusion 12 is joined to the main surface 11a of the base 11 by a metal film 40 and protrudes upward from the main surface 11a. The protrusion 12, in a state where it is joined to the base 11, includes a side surface 12a erected from the main surface 11a and an upper surface 12b connected to the side surface 12a. The upper surface 12b is used as a mounting surface for mounting an electric element, and in the light-emitting device 100 of this embodiment, a light-emitting element 20 such as a semiconductor laser is mounted thereon. The upper surface 12b of the protrusion 12 and the light emitting element 20 are joined together by a solder film (not shown) formed on the upper surface 12b.

[0013] In addition, in the substrate 10, the main surface 11a of the base 11, which surrounds the protrusion 12 and corresponds to the outer edge of the substrate 10, is used as a bonding surface to be bonded to the lid 30. In this embodiment, a metal film 41 is formed on the main surface 11a, and the substrate 10 and the lid 30 are bonded to each other by this metal film 41.

[0014] Furthermore, the substrate 10 has a terminal electrode 13 on its back surface opposite to the main surface 11a of the base 11. The terminal electrode 13 is electrically connected to the light-emitting element 20 by a metal via penetrating the inside of the base 11, a wiring electrode connected to the metal via and formed on the main surface 11a, and a wiring electrode connected to the wiring electrode via a wire bond and formed on the upper surface 12b, all of which are not shown.

[0015] The cover 30 is made of a metal material or ceramic, and is provided with a base material having a length and width of 4 mm and a thickness of 22.5 mm, and a recess 31 having an opening length and width of 3 mm and a depth of 2 mm at the center of one main surface side of the base material. In addition, one side wall forming one side of the recess 31 has a rectangular window portion 32 with a side of 0.5 mm that passes through the inside and outside of the recess 31, and translucent glass is fitted into the window portion 32. The cover 30 is bonded to the main surface 11a of the base 11 by a metal film 41 so that the recess 31 covers the light emitting element 20 and the protrusion 12, and the light emitting element 20 and the protrusion 12 are airtightly sealed in the recess 31. The cover 30 is disposed on the substrate 10 so that the light emitted from the light emitting element 20 passes through the window portion 32 of the cover 30 and is radiated to the outside.

[0016] Here, in this embodiment, the main surface 11a of the base 11 and the upper surface 12b of the protrusion 12 are mirror surfaces, and the calculated average roughness Ra of the main surface 11a and the upper surface 12b is 0.05 μm. In addition, the side surface 12a of the protrusion 12 is a rough surface. In the present invention, the "mirror surface" refers to a surface having an arithmetic mean roughness (Ra) of 0.2 μm or less, and the "rough surface" refers to a surface having an Ra of more than 0.2 μm. In this way, by making the main surface 11a, which is the bonding surface between the lid 30 and the substrate 10, a mirror surface is formed, so that the adhesion between the main surface 11a and the lid 30 is improved, and the substrate 10 and the lid 30 can be bonded with high bonding quality. In particular, when an electric element that is required to be sealed airtight, such as the light-emitting element 20, is mounted on the substrate 10, the electric element can be sealed airtightly. Furthermore, by making the top surface 12b of the protrusion 12 on which the electric element is mounted also a mirror surface, the bonding strength between the electric element and the top surface 12b of the protrusion 12 is improved.

[0017] Next, a method for manufacturing a substrate according to the present invention will be described using the method for manufacturing the above-mentioned electric element mounting board 10 as an example. Fig. 2 is a schematic diagram showing a method for manufacturing a substrate according to one embodiment of the present invention. In the method for manufacturing a substrate in this embodiment, the substrate 10 is manufactured by bonding two substrates together.

[0018] [Groove formation process: Figure 2(a)] First, a first substrate 200 made of a rectangular aluminum nitride substrate having a thickness of 1 mm is prepared. The first substrate 200 is a base material of the protrusion 12 of the substrate 10. Then, a groove 201 is formed on one main surface of the first substrate 200 by a known blasting technique or laser processing technique. The groove 201 is formed in a portion along the outer periphery of the protrusion 12 of the substrate 10, and in this embodiment, the groove has a width of 0.2 mm, a depth of 0.5 mm, and is formed in a square ring shape with one side of 2 mm. Since the groove 201 is formed by blasting or laser processing, the side and bottom surfaces of the groove 201 are rough.

[0019] [First metal layer formation process: Figure 2(b)] Next, as shown in FIG. 2(b), a first metal layer 202 is formed in the portion surrounded by the rectangular ring-shaped groove 201 by known photolithography and deposition techniques. The first metal layer 202 is made of an undercoat film and a surface film formed on the undercoat film. In this embodiment, the undercoat film is, for example, a Ti film that has good adhesion to the first substrate 200, and has a thickness of 0.05 μm. The surface film is a Cu film and has a thickness of 0.1 μm.

[0020] [Mirror polishing process] Next, a second substrate 300 made of aluminum nitride is prepared. The second substrate 300 is a base material of the base body 11 of the substrate 10. One main surface of the second substrate 300 (corresponding to the main surface 11a of the substrate 10) is polished by means of polishing or the like until it becomes a mirror surface. The thickness of the second substrate 11 after polishing is 2 mm.

[0021] [Second metal layer formation process: Figure 2(c)] Next, a second metal layer 301 is formed on one main surface of the second substrate 300 by known photolithography and deposition techniques. In this embodiment, the second metal layer 301 is a single-layer metal film, such as a Ti film, which has good adhesion to the second substrate 300. The second metal layer 301 has a thickness of 0.05 μm and is formed with the same outer shape and area as the first metal layer 202. Here, the second metal layer 301 may be a laminated film of a Ti film as an undercoat film and a Cu film as a surface film, the same as the first metal layer 202.

[0022] [Joining process: Figure 2(d)] Next, the first substrate 200 and the second substrate 300 are arranged so that the second metal layer 301 formed on the second substrate 300 faces the first metal layer 202 formed on the first substrate 200, and the first substrate 200 and the second substrate 300 are bonded together. The first substrate 200 and the second substrate 300 are bonded together by heating and melting the first metal layer 202 and the second metal layer 301 to bond the respective metal layers together. Here, the first metal layer 202 and the second metal layer 301 bonded together correspond to the metal film 40 on the substrate 10.

[0023] [First substrate grinding process: Figure 2(e)] Next, the other main surface opposite to one of the main surfaces of the first substrate 200 is ground. This grinding is performed until the bottom surface of the groove 201 formed on one of the main surfaces of the first substrate 200 is opened. In other words, grinding is performed until the part of the first substrate 200 surrounded by the rectangular ring-shaped groove 201 and the part located outside the groove 201 are separated. Here, the part of the first substrate 200 surrounded by the groove 201 is joined to the second substrate 300 by the first metal layer 202 and remains on the second substrate 300, becoming the protrusion 12 of the substrate 10. In addition, the part of the first substrate 200 located outside the groove 201 is separated and removed from the second substrate 300. Note that it is desirable for the ground surface of the first substrate 200 to be a mirror surface, and polishing may be performed after the grinding process.

[0024] [Wiring electrode formation process] Next, using known photolithography and plating techniques, wiring electrodes and a solder film (not shown) are formed on the ground surface of the first substrate 200 (upper surface 12b of the protrusion 12 in the substrate 10), and a metal film 41 and wiring electrodes (not shown) that join the lid 30 and the substrate 10 in the light emitting device 100 are formed on one surface of the second substrate 300. In addition, a metal via that penetrates the inside of the second substrate 300 and a terminal electrode 13 are formed on the other surface of the second substrate 300. With the above steps, the substrate 10 is completed.

[0025] The substrate 10 on which electric elements such as the light-emitting element 20 are mounted is a very fine component, and it is very difficult to mirror-finish the main surface 11a of the base 11 around the protrusions 12 when the protrusions 12 are formed. However, in the substrate manufacturing method of the present embodiment, the first substrate 200 and the second substrate 300 are bonded together after the second substrate 300 is mirror-finished. Therefore, even if the component is very fine, the main surface 11a of the base 11 around the protrusions 12 can be mirror-finished easily and accurately.

[0026] The substrate manufacturing method of the present embodiment may be performed in the form of an aggregate substrate in which a plurality of substrates 10 are manufactured from the first substrate 200 and the second substrate 300. In that case, the first substrate 200 and the second substrate 300 having a size that allows a plurality of desired substrates 10 to be obtained are prepared, and processes from the groove forming process to the wiring electrode forming process are carried out, and finally the aggregate substrate 10 is divided.

[0027] In addition, in this embodiment, the first substrate 200 is ground after bonding the first substrate 200 and the second substrate 300 to form the portion that will become the convex portion 12 in the substrate 10, but the first substrate 200 may be processed to match the outer shape of the convex portion 12 and then bonded to the second substrate 300. However, in this case, the first substrate 200 processed to the shape of the convex portion 12 becomes individual pieces, and when the convex portion 12 is small, it is difficult to handle. Furthermore, when manufacturing multiple substrates 10, it is necessary to bond the individual convex portions 12 to one base 11 each time, which is not efficient. Therefore, when manufacturing multiple substrates 10, it is preferable to perform the above-mentioned embodiment in which the convex portion 12 is formed after bonding the first substrate 200 and the second substrate 300.

[0028] The electric element mounting board and the manufacturing method of the board of the present invention have been described above based on the embodiments, but the scope of the present invention is not limited to the above-mentioned embodiments and can be changed as desired within the scope of the technical idea of ​​the present invention. For example, the base 11 and the protrusions 12 of the substrate 10 are made of aluminum nitride, but they are not limited to aluminum nitride and other materials such as aluminum oxide may be used. The base 11 and the protrusions 12 may be made of different materials. The substrate is not limited to a rectangular substrate and may be a circular substrate. The first metal layer 202 formed on the first substrate 200 and the second metal layer 301 formed on the second substrate 300 are not limited to a Ti film or a Cu film and may be a metal layer such as Au or a material other than a metal as long as it can be used as a bonding material. [Explanation of symbols]

[0029] 100 Light emitting device 10. Electrical element mounting board (substrate) 11 Base 11a Main surface 12 Convex part 12a side 12b Top surface 13 Terminal electrode 20 Light emitting element 30 Lid 31 Recess 32 Window 40 Metal Film 41 Metal Film 200 First board 201 Groove 202 First metal layer 300 Second board 301 Second metal layer

Claims

1. An electric element mounting substrate for mounting an electric element on an upper surface of a protrusion protruding upward from a main surface of a substrate, and bonding a lid body for covering the electric element to the main surface, comprising:

13. An electric element mounting board, wherein the main surface to which the lid is bonded is a mirror surface.

2. 2. The electrical element mounting board according to claim 1, wherein the upper surface of the protrusion is a mirror surface.

3. 2. The electrical element mounting board according to claim 1, wherein the side surfaces of the protrusions are rough.

4. A method for manufacturing a substrate, comprising the steps of: forming an annular groove on one main surface of a first substrate; A step of mirror-finishing one main surface of the second substrate; a step of bonding one main surface of the first substrate in which the groove is formed and one main surface of the second substrate which has been mirror-finished; removing the other main surface of the first substrate until the groove portion is opened; A method for manufacturing a substrate comprising the steps of:

5. forming a first metal layer on one main surface of the first substrate surrounded by the groove; forming a second metal layer on one main surface of the second substrate that has been mirror-finished; 5. The method for manufacturing a substrate according to claim 4, wherein the step of bonding the first substrate and the second substrate is a step of bonding the first metal layer and the second metal layer.

6. 6. The method for manufacturing a substrate according to claim 4, wherein the step of removing and processing the other surface of the first substrate is a step of making the removed surface of the first substrate a mirror surface.

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