JP2006228856A - Wiring board for packaging light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board for packaging a light emitting device capable of surely improving light emission efficiency of the light emitting device to be packaged. <P>SOLUTION: The wiring board 1 for packaging light emitting device comprises a board body 2 of ceramics (insulating material) which has a front surface 3 and a rear surface 4, a cavity 5 which is opened on the front surface 3 of the board body 2 and in which a light emitting device 8 is packaged on its bottom surface 7, and a light reflecting layer 10 formed on a tilted side surface 6 of the cavity 5. The thickness of an Ag layer included on the light reflecting layer 10 is more than 3 μm to 10 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

In a wiring board on which a light emitting element is mounted, a light reflecting layer made of metal is formed on a side surface of a cavity in which the light emitting element is mounted, and a sealing resin is filled in the cavity so that the surface is flat. Thus, the light emitted from the light emitting element can be made clear.
Therefore, in order to efficiently reflect the light from the light emitting element to the outside, a frame body having a through hole inside and a ceramic body is bonded to the upper surface of the ceramic substrate, and W and Mo are bonded to the inner surface of the through hole. There has been proposed a light-emitting element storage package in which a metal layer containing is deposited, and a Ni plating layer and an Ag plating layer or an Au plating layer are sequentially deposited on the metal layer (see, for example, Patent Document 1).

JP 2004-207672 A (pages 1 to 8, FIGS. 1 and 4)

  However, in the light emitting element storage package, the thickness of the Ag plating layer or the Au plating layer located on the surface layer to directly reflect the light emitted from the light emitting element is 0.1 to 3 μm. Due to uneven plating due to uneven thickness, the underlying Ni plating layer or the metal layer may be exposed on the inner surface of the through hole. As a result, there has been a problem that light from the mounted light emitting element cannot be efficiently reflected.

  An object of the present invention is to solve the problems in the background art described above and to provide a wiring board for mounting a light emitting element that can surely improve the light emission efficiency of the light emitting element to be mounted.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, the present invention includes a light reflecting layer formed on a side surface of a cavity of a substrate body on which a light emitting element is mounted on a bottom surface, and a thickness and gloss of an Ag layer that reflects light from the light emitting element. This is made by paying attention to the degree or the surface roughness within a predetermined range.
That is, a wiring board for mounting a light emitting element according to the present invention (Claim 1) has a substrate body having a front surface and a back surface and made of an insulating material, and a cavity that opens on the surface of the substrate body and mounts the light emitting element on the bottom surface And a light reflection layer formed on the side surface of the cavity, wherein the Ag layer included in the light reflection layer has a thickness in the range of more than 3 μm to 10 μm.

If the thickness of the Ag layer is 3 μm or less, there is a possibility that a deposit portion is generated due to, for example, uneven plating. On the other hand, if the thickness of the Ag layer is more than 10 μm, the cost is increased. The thickness of the Ag layer is desirably in the range of 4 μm to 10 μm, and more desirably in the range of 6 μm to 10 μm.
According to this, since the thickness of the Ag layer included in the light reflecting layer formed on the side surface of the cavity is in the range of more than 3 μm to 10 μm, uneven plating can be reduced even if the Ag layer is formed by plating, for example. In addition, it is formed on the side surface of the cavity with a relatively uniform thickness. Therefore, it becomes possible to efficiently reflect and emit the light emitted from the light emitting element mounted on the bottom surface of the cavity.

  The insulating material forming the substrate body is, for example, a ceramic mainly composed of alumina, a glass-ceramic that is a low-temperature fired ceramic, or various resins such as epoxy. The cavity has a substantially conical shape, a substantially elliptical cone shape, or a substantially long conical shape having side surfaces that are inclined from the periphery of a circular, elliptical, or oval bottom surface and extend toward the surface of the substrate body. In addition, a cylindrical shape, an elliptic cylindrical shape, or an overall cylindrical shape having a side surface of a long cylindrical shape is also included. Further, the light emitting element includes a semiconductor laser in addition to the light emitting diode. In addition, the Ag layer is formed by plating, vapor deposition, sputtering, or the like.

The present invention also includes a wiring board for mounting a light-emitting element (Aspect 2), wherein the Ag layer has a glossiness of 0.2 or more.
According to this, since most of the light irradiated to the glossy Ag layer at a predetermined angle is specularly reflected, the light emitted from the light emitting element mounted on the bottom surface of the cavity is reflected more efficiently and reliably. It becomes possible to do.
In addition, when the glossiness of the Ag layer was less than 0.2, the ratio of regular reflection of the irradiated light was reduced, so this range was excluded. The glossiness of such an Ag layer is desirably in the range of 0.4 to 1.9, more desirably 0.9 to 1.9. As will be described later, the glossiness is higher as the GAM value is closer to 2 and lower as the GAM value is closer to 0.

Furthermore, the present invention includes a light emitting element mounting wiring board (Claim 3) in which the surface roughness of the Ag layer is 3 μm or less in terms of Ra (center line average roughness).
According to this, most of the light irradiated to the Ag layer having the above surface roughness at a predetermined angle is specularly reflected by the smooth surface of the Ag layer. It becomes possible to reflect light emitted from the element more efficiently and reliably.
When the surface roughness (Ra) of the Ag layer exceeds 3 μm, a considerable amount of the irradiated light is irregularly reflected, so this range is excluded. The surface roughness (Ra) of the Ag layer is desirably 1.5 μm or less, more desirably 1 μm or less.

In other words, in the present invention, the thickness of the Ag layer included in the light reflection layer is set to be in the range of more than 3 μm to 10 μm, preferably 4 μm to 10 μm, more preferably 6 μm to 10 μm, and the glossiness of the Ag layer is 0. It is also possible to include a light emitting element mounting wiring board that is .2 or more, preferably 0.4 to 1.9, more preferably 0.9 to 1.9.
In the present invention, the thickness of the Ag layer contained in the light reflection layer is in the range of more than 3 μm to 10 μm, preferably 4 μm to 10 μm, more preferably 6 μm to 10 μm, and the surface roughness of the Ag layer is Ra. A light-emitting element mounting wiring board having a range of 3 μm or less, desirably 1.5 μm or less, and more desirably 1 μm or less may be included.
In these cases, the light emitted from the light emitting element can be more efficiently and reliably reflected.

In the following, the best mode for carrying out the present invention will be described.
FIG. 1 is a vertical sectional view showing a light emitting element mounting wiring board (hereinafter simply referred to as a wiring board) 1 according to the present invention, and FIG. 2 is a partially enlarged view of an alternate long and short dash line portion X in FIG.
As shown in FIG. 1, the wiring substrate 1 includes a substrate body 2 having a front surface 3 and a back surface 4, and a cavity 5 that opens to the front surface 3 of the substrate body 2 and mounts a light emitting diode (light emitting element) 8 on the bottom surface 7. And a light reflecting layer 10 formed on the inclined side surface 6 of the cavity 5.
The substrate body 2 is composed of, for example, alumina-based ceramic (insulating material) layers s1 to s7 laminated together, and has a square of about 5 mm square in plan view and a thickness of about 1 mm.

Instead of the ceramic layers s1 to s7, a glass-ceramic (insulating material) layer or a resin (insulating material) layer such as a BT resin or an epoxy resin may be used. The glass-ceramic is a low-temperature fired ceramic such as a glass-alumina system having a firing temperature of 1000 ° C. or lower.
As shown in FIG. 1, the cavity 5 has a circular bottom surface 7 in plan view, and a side surface 6 that extends from the periphery of the bottom surface 7 through the ceramic layers s <b> 5 to s <b> 7 toward the surface 3 of the substrate body 2. And the whole has a substantially conical shape. The elevation angle of the side surface 6 is appropriately selected within a range of 30 degrees or more and 80 degrees or less. Further, the cavity 5 is formed by punching through a required clearance on an upper green sheet laminate obtained by laminating three unit green sheets or large green sheets that become ceramic layers s5 to s7 by firing, Alternatively, a conical mold is pushed into a cylindrical through-hole formed in advance to form a through-hole having a substantially conical side surface, and a lower green sheet laminate that becomes ceramic layers s1 to s4 by firing is formed thereunder. It is formed by stacking.

As shown in FIG. 1, a light reflecting layer 10 including a later-described Ag layer 16 and the like is formed in a substantially conical shape on almost the entire side surface 6 of the cavity 5.
When the alumina-based ceramic is used as the insulating material of the substrate body 2 as the base of the light reflecting layer 10, for example, a refractory alloy such as W or Mo is applied, and the glass-ceramic is used. In this case, Ag or Cu capable of simultaneous firing is applied. Moreover, when using the said epoxy resin etc. for the insulating material of the board | substrate body 2, Cu etc. which can form a pattern by a well-known photography technique (for example, subtractive method etc.) are applied.
Further, as shown in FIG. 1, on the bottom surface 7 of the cavity 5, a pair of pads 17 made of W, Mo, Ag, or Cu and forming different circuits are located at the center of the bottom surface 7. The mounting areas are spaced apart from each other.

A light emitting diode 8 is mounted on the bottom surface 7 of the cavity 5 via a brazing material 9 or an epoxy resin adhesive. At that time, the bonding wires w are individually connected between the pair of pads 17. The cavity 5 is filled with a sealing resin before solidification, and the surface thereof is solidified with the surface 3 of the substrate body 2. The brazing material 9 is made of a low melting point alloy such as Sn—Ag.
Further, as shown in FIG. 1, the upper ends of a pair of via conductors 18 penetrating the ceramic layers s1 to s4 are individually connected to the pair of pads 17, and the lower ends of the via conductors 18 are connected to the substrate body 2. The pair of back surface electrodes 19 formed on the back surface 4 are individually connected. Each via conductor 18 is individually connected to a wiring layer (not shown) formed between the ceramic layers s1 to s4. In FIG. 1, for example, one of the two sets of the circuit composed of the pad 17, the via conductor 18 and the back electrode 19 which are positioned symmetrically forms a ground circuit and the other constitutes a signal circuit. The via conductor 18, the wiring layer, and the back electrode 19 are made of W, Mo, Ag, or Cu. Further, between the ceramic layers s5 to s7, wiring layers and via conductors (not shown) that are connected to the respective circuits are formed.

As shown in FIG. 2, the light reflecting layer 10 includes a base metal layer 11 made of W, Mo, Ag, or Cu formed on the side surface 6 of the cavity 5, and a Ni plating layer 12 formed thereon. The Au plating layer 15 formed on the Ni plating layer 12 and the Ag plating layer (Ag layer) 16 formed on the Au plating layer 15.
The metal layer 11 is W or Mo co-fired with the ceramic layers s1 to s7, or Cu or Ag co-fired with the glass-ceramic, and has a thickness of about 10 to several tens of micrometers. When the insulating material of the substrate body 2 is made of an epoxy resin or the like, the metal layer 11 is a Cu plating layer.

The Ni plating layer 12 is an underlayer for metal plating. As shown in FIG. 2, the Ni plating layer 13 having a thickness of 0.5 to 2 μm and a thickness of 1 to 9 μm are disposed on the first Ni plating layer 13. 2nd Ni plating layer 14, and the range of the whole thickness is 1.5 to 11 μm. The first Ni plating layer 13 is formed by electroless Ni plating or electrolytic Ni plating, and the second Ni plating layer 14 is formed by electrolytic Ni plating.
Furthermore, the Au plating layer 15 is mainly coated to ensure sufficient adhesion between the second Ni plating layer 14 and the Ag plating layer 16, and the thickness is 0.03 to 0.2 μm by electrolytic Au plating. It is formed in the range of

The Ag plating layer 16 is a layer that directly reflects the light emitted from the light emitting diode 8, and is formed by electrolytic Ag plating to have a thickness in the range of 3 to 10 μm. The desirable thickness of the Ag plating layer 16 is in the range of 4 to 10 [mu] m, more preferably 6 to 10 [mu] m. Further, since the thickness of the Ag plating layer 16 tends to be thin near the upper and lower ends of the light reflecting layer 10, the lower limit value of the thickness is satisfied at least near the upper and lower ends of the light reflecting layer 10.
The surface roughness (Ra) of the Ag plating layer 16 is 3 μm or less, desirably 1.5 μm or less, and more desirably 1 μm or less.
Further, the gloss (GAM value) of the Ag plating layer 16 is 0.2 or more, desirably 0.4 to 1.9, more desirably 0.9 to 1.9.
The glossiness (GAM value) is calculated by Equation 1.

The glossiness (GAM value) is measured by the method shown in FIG.
The light reflecting layer 10 including the Ag plating layer 16 is fixed in advance on a surface plate (not shown) with the Ag plating layer 16 facing upward. Further, as shown in FIG. 3, the projector 20 is disposed at an angle of 45 degrees above the surface plate, and the light receiver 22 is disposed along the vertical direction.
Next, light A is emitted from the projector 20 at an incident angle of 45 degrees with respect to the light reflecting layer 10. Since the light A is regularly reflected by the Ag plating layer 16 located on the surface layer of the light reflecting layer 10, most of the light A becomes light C having a reflection angle of 45 degrees. However, a part of the light B is received by the light receiver 22 as light B which is irregularly reflected due to the undulation and surface roughness on the surface of the Ag plating layer 16. The amount of the light B is measured by the light receiver 22 or the like.
As shown in Equation 1, the smaller the light B is, the closer the glossiness is to 2, and the more the light B is, the closer the glossiness is to 0.

That is, the Ag plating layer 16 having the glossiness of 0.2 or more, desirably 0.4 to 1.9, more desirably 0.9 to 1.9, has the thickness and surface roughness ( In conjunction with Ra), it is understood that the surface has a fairly smooth and uniform thickness. For this reason, since the light reflection layer 10 including the Ag plating layer 16 in the range of the thickness, the glossiness, and the surface roughness (Ra) is formed on the side surface 6 of the cavity 5, the light reflection layer 10 is formed on the bottom surface 7 later. The light emitted from the mounted light emitting diode 8 is efficiently and reliably reflected and radiated to the outside.
Therefore, according to the wiring substrate 1 as described above, the light of the diode 8 mounted on the bottom surface 7 of the cavity 5 can be reflected efficiently and reliably.

FIG. 4 is a vertical sectional view similar to the above showing a wiring board 1a of a different form.
As shown in FIG. 4, the wiring board 1 a includes a substrate body 2 a having the front surface 3 and the back surface 4, a cavity 5 a that opens on the surface 3 of the substrate body 2 a and mounts the light emitting diode 8 on the bottom surface 7. And a light reflection layer 10 formed on the vertical side surface 6a of the cavity 5a.
In the following description, portions different from the wiring board 1 will be described.
As shown in FIG. 4, the cavity 5a has a bottom surface 7 that is circular in plan view, and a cylindrical side surface 6a that stands vertically from the periphery of the bottom surface 7 and penetrates the ceramic layers s8 to s10. The whole is cylindrical.

The cavity 5a is formed by punching a three-layer green sheet, which becomes ceramic layers s8 to s10 by firing, by punching with a punch and a die through a minimum clearance, and an upper side green sheet laminate having a cylindrical through hole on the side surface. The body is formed, and this and the lower green sheet laminate are laminated.
On the cylindrical side surface 6a, as shown in FIG. 2, the metal layer 11 made of W, Mo, Ag, or Cu, the Ni plating layer 12 (13, 14), the Au plating layer 15, and the Ag plating layer ( A cylindrical light reflection layer 10 made of (Ag layer) 16 is formed in the same manner as described above.
Even with the wiring board 1a as described above, the same effects as those of the wiring board 1 can be exhibited and the effects can be achieved.

FIG. 5 is a vertical sectional view similar to the above showing a wiring board 1b which is an application form of the wiring board 1a, and FIG. 6 is a partially enlarged view of a one-dot chain line portion Y in FIG.
As shown in FIG. 5, the wiring board 1b has the same substrate body 2b having the front surface 3 and the back surface 4, and a light emitting diode 8 mounted on the bottom surface 7 that opens to the front surface 3 of the substrate body 2b and has a slightly larger diameter. And a light reflecting layer 10b formed across the vertical side surface 6b and the bottom surface 7 of the cavity 5b.
In the following description, parts different from the wiring board 1a will be described.

As shown in FIGS. 5 and 6, the light reflecting layer 10b has a ring shape in plan view and a vertical section of a substantially right triangle, and is formed in an approximately L shape along the bottom surface 7 and the side surface 6b of the cavity 5b. A metal layer 11 made of W, Mo, Ag, or Cu, and a first Ni plating layer 13 formed in an approximately L shape along the inside thereof. The metal layer 11 is interposed between the ceramic layers s4 and s8. The wiring part 11b extended horizontally is included.
As shown in FIG. 6, an Ag brazing material 16 b having a substantially right-angled cross section is formed on the inner corner side of the first Ni plating layer 13 having an approximately L shape.

As shown in FIG. 6, the second Ni plating layer 14 is formed across the inclined outer surface of the Ag brazing material 16b and the upper and lower ends of the first Ni plating layer 13 exposed above and below the Ag brazing material 16b. An Au plating layer 15 and an Ag plating layer (Ag layer) 16 are sequentially formed with the same thickness as described above. The Ag layer 16 also has the thickness, glossiness, and surface roughness (Ra) within the above ranges. As shown in FIG. 6, the upper and lower end portions of the Ag layer 16 are likely to be thin. Therefore, the thickness of 3 μm or more is applied at least to such a position.
Also with the wiring board 1b as described above, it is possible to exert the same effect as the wiring boards 1 and 1a and to achieve the effect.

The present invention is not limited to the individual remains described above.
The entire cavity may have a substantially conical shape, a substantially elliptical cone shape, a long cylindrical shape, or an elliptical columnar shape, and the light reflecting layers 10 and 10b may be formed on the side surfaces thereof. Alternatively, the cavity may have a square shape in plan view and a substantially regular pyramid shape, or a rectangular shape in plan view and a substantially quadrangular pyramid shape, and the surface may be curved at a corner between adjacent sides. The light reflecting layers 10 and 10b may be formed on the brazing material and each side surface.
Further, a plurality of cavities may be formed on a single substrate body. Alternatively, cavities having different shapes may be provided on the same substrate body.
Further, the Ni plating layer 12 (13, 14) and the Au plating layer 15 may be Ni layers or Au layers formed by vapor deposition or sputtering.

The vertical sectional view showing the wiring board of one form in the present invention. The elements on larger scale of the dashed-dotted line part X in FIG. Schematic which shows the measuring method of glossiness. The vertical sectional view which shows the wiring board of a different form. The vertical sectional view which shows the application form of the said wiring board. The elements on larger scale of the dashed-dotted line part Y in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Light-emitting-element mounting wiring board 2, 2a, 2b ... Substrate main body 3 ............... Front side 4 ............... Back side 5, 5a, 5b ... Cavity 6, 6a, 6b … Side 7 ………………… Bottom 8 ………………… Light Emitting Diode (Light Emitting Element)
10, 10b …… Light reflecting layer 16 ……………… Ag plating layer (Ag layer)

Claims (3)

A substrate body having a front surface and a back surface and made of an insulating material;
A cavity that opens on the surface of the substrate body and mounts the light emitting element on the bottom surface;
A light reflecting layer formed on a side surface of the cavity,
The thickness of the Ag layer contained in the light reflecting layer is in the range of more than 3 μm to 10 μm.
A wiring board for mounting a light-emitting element. The glossiness of the Ag layer is 0.2 or more.
The wiring board for mounting a light emitting element according to claim 1. The surface roughness of the Ag layer is 3 μm or less in Ra.
The wiring board for mounting a light-emitting element according to claim 1 or 2.

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