JP2006156510A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board including a metal layer for reflection having higher close contact strength in the side surface of a cavity to mount a light emitting element. <P>SOLUTION: The wiring board 1 comprises a substrate body 2 formed of a ceramic (insulating) material to include a front surface 3 and a rear surface 4, a cavity 5 opening to the front surface 3 of such substrate body 2 and including an mounting area (a) of a light emitting element 9 to a bottom surface 6, and a metal layer 10 formed continuously along the side surface 7 of at least cavity 5 and the front surface 3 of the substrate body 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wiring board for mounting a light emitting element such as a light emitting diode.

  In the wiring board for mounting the light emitting element, by forming a metal reflection layer on the side surface of the cavity for mounting the light emitting element and filling the cavity with a sealing resin so that the surface is flat, The light from the light emitting element can be made clear. Then, in order to fill the cavity with the light emitting element with the sealing resin without excess or deficiency and to flatten the surface, a frame-like metallization layer is formed on the upper surface of the ceramic substrate so as to surround the cavity, and the wetted seal is formed. There has been proposed a light-emitting element mounting substrate in which a part of the stopping resin is difficult to spread on the upper surface of a ceramic substrate (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 2003-347597 (pages 1 to 5, FIG. 1)

In the light emitting element mounting substrate, the metal reflective layer formed on the side surface of the cavity and the frame-like metallized layer formed on the upper surface of the ceramic substrate are formed separately and separated from each other.
By the way, the metal reflective layer formed on the side surface of the cavity is subjected to shrinkage stress accompanying the curing of the sealing resin when the sealing resin is filled after the light emitting element is mounted in the cavity. In particular, in the vicinity of the corner between the side surface of the cavity and the surface of the wiring substrate, the stress is remarkably generated. Therefore, the metal reflective layer at such a position has a low adhesion strength, and there is a possibility that it may be severely peeled off.

  An object of the present invention is to solve the problems described in the background art and to provide a wiring board having a reflective metal layer with high adhesion strength on the side surface of a cavity in which a light emitting element is mounted.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-described problems, the present invention has been conceived in that the metal layer formed on the side surface of the cavity is continuously formed across the surface of the substrate body.
That is, the wiring board of the present invention (Claim 1) includes a substrate body made of an insulating material and having a front surface and a back surface, a cavity having an opening on the surface of the substrate body and having a mounting area for a light emitting element on the bottom surface, and at least And a metal layer continuously formed along the side surface of the cavity and the surface of the substrate body.

According to this, the metal layer is continuously formed along the side surface of the cavity and the surface of the substrate body. For this reason, when the cavity is filled with the sealing resin later, the shrinkage stress accompanying the curing of the sealing resin is caused between the cavity side part in the metal layer and the surface side part located on the surface of the substrate body. Even if concentrated in the vicinity of the corner, the shrinkage stress can be dispersed also in the surface side portion of the metal layer. Therefore, since the adhesion strength of the cavity side portion of the metal layer is improved, it is possible to efficiently and stably reflect the light emitted from the light emitting element on the reflective surface which is the surface of the metal layer.
The insulating material includes, for example, a ceramic mainly composed of alumina and, for example, an epoxy-based synthetic resin.
Moreover, the surface side part of a board | substrate body among the said metal layers may be connected with the external conductor mentioned below so that conduction | electrical_connection is possible. That is, the metal layer can serve as a light reflection surface at the cavity side and also serve as a conduction path with an external circuit such as a mother board.

Further, the present invention includes a wiring board (Claim 2) further including an outer conductor formed continuously along the front and back surfaces of the substrate body and the outer surface between them.
According to this, the wiring layer, the internal electrode and the like built in the board body can be conducted to the mother board or the like on which the wiring board is to be mounted via the external conductor. Therefore, even if the light emitting element is mounted in the cavity and the metal layer is continuously formed along the side surface of the cavity and the surface of the substrate body, the operation of the internal wiring layer of the substrate body is hindered. Therefore, the required conduction can be ensured.

  In other words, the wiring board of the present invention may be configured such that the outer conductor is formed inside a recess opening in an outer surface of the substrate body or a recess opening in a corner between adjacent outer surfaces. Is possible. In this case, even if the light emitting element is mounted in the cavity and the metal layer is continuously formed along the side surface of the cavity and the surface of the substrate body, the wiring layer and the internal electrode incorporated in the substrate body, etc. Can be electrically connected to an external circuit device via an external conductor provided in the recess without causing an inadvertent short circuit.

  In addition, in the wiring board of the present invention, the side surface of the cavity may be an inclined surface that extends outward from the bottom surface of the cavity toward the surface of the substrate body. In this case, a large amount of light emitted from the light emitting element can be reflected at a wide range of angles.

In the following, the best mode for carrying out the present invention will be described.
1 is a plan view showing a wiring board 1 according to an embodiment of the present invention, FIG. 2 is a vertical sectional view taken along the line XX in FIG. 1, and FIG. FIG. 4 is a vertical cross-sectional view taken along the line ZZ in FIG. 1, and FIG. 4 is a vertical cross-sectional view taken along the line ZZ in FIG.
As shown in FIGS. 1 to 4, the wiring substrate 1 has a substrate body 2 having a substantially square shape in plan view and having a front surface 3 and a back surface 4, and an opening in the front surface 3 of the substrate body 2 and a circular shape in plan view. A cavity 5 and a metal layer 10 continuously formed along the side surface 7 of the cavity 5 and the surface 3 of the substrate body 2 are included.
The substrate body 2 is made of ceramic (insulating material) mainly composed of alumina, for example, and a wiring layer and internal electrodes (not shown) are formed in a predetermined pattern therein, and via conductors (not shown) are formed therebetween. ) Is present. Incidentally, the size of the substrate body 2 is about 5 mm × 5 mm × 0.9 mm.

On the bottom surface 6 of the cavity 5, a light emitting element 9 such as a light emitting diode having a square shape in plan view is mounted in the mounting area “a” via a brazing material 8 or an epoxy resin. The size of the cavity 5 is about 3.6 mm inside diameter × about 0.45 mm depth, and the brazing material 8 is made of, for example, an Au—Sn low melting point alloy.
Further, a metallized layer 13 having a stepped cross section made of W or Mo is formed on the bottom surface 6 and the side surface 7 of the cavity 5 and the surface 3 of the substrate body 2, and a Ni plating layer (not shown) has a thickness on the surface. It is coated with about 5 μm.

The metal layer 10 is made of, for example, an Ag, Pt, Rh, or Pd plating layer having a thickness of about 10 to 30 μm. As shown in FIG. 2 and an enlarged view of a one-dot chain line portion C in FIG. Are integrally formed with a cavity-side portion 11 that is inclined along the upper surface of the cavity-side portion 11 and a surface-side portion 12 that is continuous with the upper end of the cavity-side portion 11 and is formed along the surface 3 of the substrate body 2. The cavity side portion 11 of the metal layer 10 clearly reflects the light emitted from the light emitting element 9 and emits the light to the outside (not shown).
The inside of the cavity side portion 11 and the metallized layer 13 is filled with a brazing material 14 made of an Ag—Cu alloy having a substantially triangular cross section, and a metal layer is formed on the inclined surface via a Ni plating layer (not shown). Ten cavity-side portions 11 are Ag-plated or the like.

As shown in FIGS. 1 to 4, arc-shaped concave portions (outer surfaces) 15 are formed at the four corners of the substrate body 2 in a plan view, and the outer conductor has an arc-shaped cross section on the entire surface. 16, 20 are formed.
As shown in FIGS. 1 and 3, the external conductor 16 has a front surface electrode 17 located on the front surface 3 of the substrate body 2 and a back surface electrode 18 located on the back surface 4 of the substrate body 2. As shown in FIGS. 1 and 4, the external conductor 20 is located on the surface 3 of the substrate body 2 and is connected to the surface side portion 12 of the metal layer 10, A back electrode 22 located on the back surface 4 continuously.
The external conductors 16 and 20, the front surface electrode 17, the back surface electrodes 18 and 22, and the connection portion 21 are made of, for example, W, Mo, or Ag having a thickness of about 10 to 30 μm.

In the wiring substrate 1 as described above, after the light emitting element 9 is mounted on the mounting area a located on the bottom surface 6 of the cavity 5 via the brazing material 8 or the like, as shown in FIG. The sealing resin r is filled in a molten state and solidified so that the surface thereof is flush with the surface 3 of the substrate body 2. At this time, even if the shrinkage stress accompanying the curing of the sealing resin r is concentrated in the vicinity of the corner between the cavity side portion 11 of the metal layer 10 and the surface side portion 12 on the surface 3 of the substrate body 2, it is applied. The shrinkage stress can also be distributed to the surface side portion 12 continuous with the cavity side portion 11.
Accordingly, the adhesion strength of the cavity-side portion 11 of the metal layer 10 that is the reflection surface is improved, and thus light emission from the light-emitting element 9 can be clearly and stably reflected.

As shown in FIG. 5, the wiring board 1 sealed in the cavity 5 with the sealing resin r has a surface electrode (not shown) located on a surface 25 of a printed board 24 such as a mother board and an external conductor 16 ( 20) and the back electrode 18 (22) thereof, and is mounted on the surface 25 of the printed circuit board 24 with a brazing material 26 formed therebetween.
The wiring board 1 as described above is formed by laminating and press-bonding a plurality of green sheets mainly composed of alumina in which a conductive paste containing a metal powder such as W or Mo is formed in a predetermined pattern on the surface. The laminate obtained by printing the conductive paste on the side surface 7 of the cavity 5 is fired in a required temperature range, and then the surface of the fired metallized layer 13 or brazing material 14 is subjected to Ag plating or the like. Manufactured.

Alternatively, the wiring board 1 can be manufactured by a multi-cavity method as described below.
First, as shown in FIG. 6, each of the plurality of product portions s that have the cavities 5 and are to be the substrate body 2 is provided with substantially upper half portions along the vertical and horizontal directions, and a plurality of green sheets are provided. A large-sized laminated body S1 is prepared. At each intersection of the planned cutting line c indicated by a broken line in FIG. 6, a cylindrical through hole h is formed later by press punching or the like.
As shown in FIG. 7, a screen mask M is placed on the surface 3 side of the large-sized laminate S1, and the screen mask M is located near the side surface 7 of the cavity 5 for each product portion s. A mesh portion m having a ring shape in a plan view and a required width dimension is disposed. As indicated by the one-dot chain line arrow in FIG. 7, air A is sucked downward in the vicinity of the ring-shaped mesh portion m. In the screen mask M, portions other than the mesh portion m are clogged by the emulsion coating.

In this state, as shown by the solid line arrow in FIG. 7, the conductive paste p is slid along the upper surface of the screen mask M while being pressed by the oblique squeegee 28. As a result, since the conductive paste p passes through the ring-shaped rough portion m, the metallized layer 13 can be printed.
Next, after laminating the laminate S1 on a plurality of green sheets that are substantially the lower half of each product portion s to form a large laminate S2, through holes h are formed at the intersections of the planned cutting line c. Form. Next, as shown in FIG. 8, a mesh portion m having a diameter larger than the inner diameter of the through hole h is arranged immediately above the through hole h in the screen mask M placed on the surface 3 side in the laminated body S2. To do.
Note that the same conductive paste is printed on the bottom surface 6 of the cavity 5 in each product portion s to form the horizontal portion of the metallized layer 13.

In this state, as indicated by the one-dot chain line arrow in FIG. 8, the air paste A is sucked from the back surface 4 side of the large-sized laminate S2 and the conductive paste p is slanted by the skid 28 in the same manner as described above. Slide while pressing. As a result, the outer conductors 16 and 20 and the surface electrode 18 thereof can be printed and formed. At this time, by extending a part of the mesh part m in the screen mask M to the cavity 5 side, the connection part 21 can be formed in a band shape at the same time. In addition, the said back surface electrodes 18 and 22 are printed and formed in the back surface 4 of laminated body S2 by the method similar to the above.
And after baking the laminated body S2 as described above in a required temperature range, the inside of the metallized layer 13 is filled with the brazing material 14, and on the surface and on the metallized layer 13 on the surface 3 of the substrate body 2. The metal layer 10 is formed by performing Ag plating through Ni plating. Such Ni plating or Ag plating is performed by bringing a dedicated plating electrode bar into contact with the external electrode 20.
Finally, a plurality of wiring boards 1 can be manufactured by cutting along the planned cutting line c.

9 is a plan view showing a wiring board 30 of a different form, FIG. 10 is a vertical sectional view taken along the line VV in FIG. 9, and FIG. 11 is a partial bottom view of the wiring board 30. .
As shown in FIGS. 9 and 10, the wiring substrate 30 is made of a ceramic (insulating material) mainly composed of alumina or the like and has a substantially rectangular parallelepiped substrate body 32 having a front surface 33 and a back surface 34, and the substrate body 32. A cavity 35 having an elliptical shape in plan view that opens to the surface 33, and an inclined side surface 37 of the cavity 35 and a metal layer 40 formed continuously along the surface 33 of the substrate body 32 are included.
As shown in FIG. 10, the substrate body 32 is formed by laminating a plurality of ceramic layers s1 to s9 and firing them integrally. Between the ceramic layers s1 to s9, there are internal wiring layers and internal electrodes (not shown). It is formed with a predetermined pattern.

The cavity 35 is composed of a bottom surface 36 that is elliptical in plan view and has a mounting area a in the center, and a side surface 37 that is elliptical in plan view and has a substantially elliptical cone shape. Further, the metal layer 40 is made of Ag, Rh, Pd, etc., and is connected to the upper end of the cavity side portion 41 having an elliptical cone shape formed on the side surface 37 of the cavity 35 as shown in FIGS. In addition, the surface side portion 42 having an elliptical shape in plan view formed along the surface 33 of the substrate body 32 is formed. The metal layer 40 is formed by covering an Ag plating layer or the like via a metallization layer such as W and a Ni plating layer (not shown).
A light emitting element 39 such as a light emitting diode is mounted on the mounting area a in the bottom surface 36 of the cavity 35 through a brazing material 38 made of, for example, an Au—Sn low melting point alloy or an epoxy resin.

As shown in FIGS. 9 and 10, a connection terminal 43 is formed on the bottom surface 36 of the cavity 35, and is individually connected to the light emitting element 39 through the bonding wire w. The connection terminal 43 is connected to a via conductor 44 that passes through the ceramic layers s <b> 6 to s <b> 9 of the substrate body 32.
Further, a concave portion 45 having a substantially semicircular shape in plan view is individually formed in the vicinity of the center of each side surface of the substrate body 32, and an outer conductor 46 having a substantially semicircular cross section is formed in a substantially lower half of each concave portion 45. ing. Further, arc-shaped recesses 48 are formed at the four corners of the substrate body 32 in plan view, and outer conductors 49 having an arc-shaped cross section are formed on the entire surface. As shown on the left and right in FIGS. 9 to 11, the external conductor 46 is connected to a connection portion 47 formed on the back surface 34 of the substrate body 32 in a bottom view, which is substantially T-shaped. The lower end of the via conductor 44 is connected.

As shown in FIGS. 9 to 11, the outer conductors 49 located at the four corners of the substrate body 32 and the outer conductors 46 located near the center of the side surface of the long side of the substrate body 32 are the back surface 34 of the substrate body 32. Are individually connected to the back electrode 50 formed on the substrate. These backside electrodes 50 are utilized for mounting the wiring board 30 on a front surface electrode of a mother board (not shown) via a brazing material.
The outer conductors 46 and 49, the back electrode 50, and the connecting portion 47 are made of, for example, W or Mo having a thickness of about 10 to 30 μm, and the via conductor 44 is made of W or Mo having a diameter of about 50 to 300 μm. Become.

  In the wiring board 30 as described above, after mounting the light emitting element 39 on the mounting area a located on the bottom surface 36 of the cavity 35 via the brazing material 38 or the like, a sealing resin (not shown) is placed in the surrounding cavity 35. It is filled in a molten state and solidified so that its surface is flush with the surface 33 of the substrate body 32. At this time, even if the shrinkage stress accompanying the curing of the sealing resin is concentrated in the vicinity of the corner between the cavity side portion 41 of the metal layer 40 and the surface side portion 42 on the surface 33 of the substrate body 32, it is applied. The shrinkage stress can be distributed to the surface portion 42. Accordingly, the adhesion strength of the cavity-side portion 41 of the metal layer 40 is improved and the inclined surface of the portion 41 that is the reflecting surface is stabilized, so that a large amount of light emitted from the light-emitting element 39 is efficiently and stably reflected. It becomes possible to do.

The wiring board 30 as described above is also laminated and pressure-bonded with a plurality of green sheets mainly composed of alumina, the surface of which is a conductive paste containing a metal powder such as W or Mo formed in advance in a predetermined pattern. After the body is fired at a required temperature range, the surface of the fired metallized layer is manufactured by Ag plating or the like.
The green sheets g to be the ceramic layers s1 to s5 forming the cavity 35 are formed by punching with a required clearance between the punch P (not shown) and the through hole of the die.

The present invention is not limited to the embodiments described above.
The ceramic which is an insulating material forming the substrate bodies 2 and 32 may be, for example, a material mainly containing mullite or aluminum nitride, or a glass-ceramic.
The insulating material forming the substrate bodies 2 and 32 may be an epoxy resin, and a plurality of resin insulating layers made of, for example, an epoxy resin are sequentially laminated on the surface of the resin thin plate or metal thin plate. Then, a cavity may be formed in each relatively upper resin insulating layer by a known photolithography technique, and the metal layer continuous along the side surface and the surface near the opening may be formed by plating.

Furthermore, the side surface 37 of the cavity 35 in the wiring substrate 30 may be perpendicular to the cavity side portion 41 of the metal layer 40 along the side surface.
Further, the shape of the cavity is not limited to the circular shape or the elliptical shape, but the elliptical shape in a plan view, or a square or a rectangle, and a conductive paste is filled in an arc shape at these four corners, and the elliptical shape in a plan view. In addition to the shape or oval shape, the cavity side portion of the metal layer may be formed on these side surfaces.
In addition, the wiring board of the present invention has a plurality of cavities opened on the surface of one substrate body, or a plurality of mounting areas arranged on the bottom surface of a single cavity, and light emitting elements are individually mounted on these. It is also possible to adopt a form.

The top view which shows the wiring board of one form in this invention. Sectional drawing along the arrow of XX in FIG. 1, and the enlarged view which expanded the part. Sectional drawing along the arrow of the YY line in FIG. Sectional drawing along the arrow of the ZZ line in FIG. The schematic sectional drawing which shows the mounting state of the said wiring board. Schematic which shows one manufacturing process for obtaining the said wiring board. Schematic which shows the manufacturing process following FIG. Schematic which shows the manufacturing process following FIG. The top view which shows the wiring board of a different form. FIG. 10 is a vertical sectional view taken along line VV in FIG. 9; The partial bottom view which shows the said wiring board.

Explanation of symbols

1,30 …………………… Wiring board 2,32 …………………… Board body 3,33 …………………… Front side 4,34 …………………… Back side 5, 35 …………………… Cavity 6, 36 …………………… Bottom 7, 37 …………………… Side 9, 39 …………………… Light Emitting Element 10 , 40 .................. Metal layer 11, 41 ............... Cavity side portion 12, 42 .................. Surface side portion 15, 45, 48 ............ Recess (outside surface) )
16, 20, 46, 49 ... Outer conductor a ..................... Mounting area s1 to s9 ............ Ceramic layer (insulating material)

Claims (2)

A substrate body made of an insulating material and having a front surface and a back surface;
A cavity having an opening on the surface of the substrate body and a mounting area of the light emitting element on the bottom surface;
A metal layer formed continuously along at least the side surface of the cavity and the surface of the substrate body,
A wiring board characterized by that. And further including an outer conductor formed continuously along the front and back surfaces of the substrate body and the outer surface therebetween.
The wiring board according to claim 1.

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