JP2008172113A - Wiring substrate - Google Patents

Abstract

The light emitting device includes a plurality of ceramic layers having a mounting surface, and can efficiently dissipate heat from the light emitting device, and a wiring layer of a required circuit can be easily arranged, and can be manufactured with simple and few processes. A possible wiring board is provided.
A first ceramic layer s1 (s1a, s1b) having a mounting surface 6 of an LED (light emitting element) 10 and a lower layer side containing a metal component and opposite to the mounting surface 6 of the first ceramic layer s1. A second ceramic layer s2 having a higher thermal conductivity than the first ceramic layer s1, and formed on the mounting surface 6 and having a surface layer coated with at least one of an Ag plating film 18 and an Au plating film 19. The first ceramic layer s1 includes a cavity 5a having a side surface 7a and a mounting surface 6 of the LED (light emitting element) 10, and the pad 8 is provided on the mounting surface 6. , 9 are formed on the wiring board 1a.
[Selection] Figure 2

Description

  The present invention relates to a wiring board having a mounting surface on which a light emitting element such as a light emitting diode is mounted and excellent in heat dissipation of heat generated by the light emitting element.

In order to easily obtain a high-intensity light quantity, an LED element is mounted on the upper surface of a metal or other heat radiating member that penetrates the central portion of the ceramic multilayer substrate, and the upper surface of the multilayer substrate surrounding the LED element is for light reflection There has been proposed a light emitting device in which a package in which the inclined surface is provided is formed and a mold resin for sealing the LED element is filled inside the package and a manufacturing method thereof (for example, see Patent Document 1).
The heat dissipating member used in the light emitting device effectively dissipates the heat generated by the LED element to the outside. The lower part having a large cross-sectional area exposed on the lower surface of each of them exhibits a rectangular shape or a circular shape similar to each other in plan view.

JP 2006-32804 A (pages 1 to 18, FIGS. 1 and 4)

  However, in the light emitting device, the heat generated by the LED element can be effectively dissipated to the outside. However, since a heat radiating member such as a metal penetrates the central portion of the ceramic multilayer substrate, it is formed inside the multilayer substrate. The layout of the power wiring layer is greatly restricted, and it becomes difficult to form a required circuit. In addition, in order to insert the heat radiating member into the central portion of the multilayer substrate, a process of forming large and small through holes in a plurality of green sheets or setting and brazing the heat radiating members in the through holes is required. Therefore, there is a problem that many complicated manufacturing processes are required.

  The present invention solves the problems described in the background art, and includes a wiring layer that includes a plurality of ceramic layers having a mounting surface of a light emitting element, can efficiently dissipate heat of the light emitting element, and forms a required circuit. It is an object of the present invention to provide a wiring board that can be easily arranged and can be manufactured by a simple and few process.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, the present invention is conceived by forming a substrate body by a first ceramic layer having a mounting surface of a light emitting element and a second ceramic layer having a higher thermal conductivity. It has been done.
That is, the wiring board of the present invention (Claim 1) includes a first ceramic layer having a light emitting element mounting surface and a metal component and is laminated on the opposite side of the first ceramic layer mounting surface. A second ceramic layer having a higher thermal conductivity than that of the first ceramic layer; and a conductor formed on the mounting surface and having a surface layer coated with at least one of an Ag plating film and an Au plating film. To do.

  According to this, for example, when a light emitting element is mounted on the conductor, the heat generated by the light emitting element is higher than that of the first ceramic layer without using a conventional heat dissipation member. Heat can be effectively radiated to the outside through the second ceramic layer. Further, since the substrate body is formed only by the first ceramic layer and the second ceramic layer, the space for the through hole for inserting the heat dissipation member as in the prior art is not required, and the wiring layer constituting the required circuit is the first. -It can be formed inside or between the second ceramic layers. In addition, in order to insert the heat radiating member into the central portion of the substrate body, a process of forming large and small through holes in a plurality of green sheets or setting and brazing the heat radiating members in the through holes becomes unnecessary. Therefore, it becomes possible to manufacture with simple and few processes.

The first ceramic layer has a whiteness higher than that of the second ceramic layer, and, for example, contains alumina or glass-alumina as a main component, and the light of the mounted light emitting element can be easily reflected by the mounting surface. The whiteness is measured with a spectrocolorimeter.
The second ceramic layer contains 5 to 50 wt% of a metal or metal oxide powder (average particle size of 10 μm or less) in a ceramic matrix. The metal contained in the second ceramic layer is W, Mo, Ag, Cu or the like, and the metal oxide is an oxide such as W, Mo, Ag, or Cu.
Further, the conductor is obtained by coating the surface of a W or Mo metallization layer formed on the mounting surface with an Ag or Au plating layer on the surface via a Ni plating layer. A plurality of such conductors are formed, and the surface layer of one of the conductors is coated with an Ag plating layer to mount a light emitting element and easily reflect the light. The remaining conductors are plated with Au on the surface layer. It is good also as an electrode which coat | covers a layer and carries out wire bonding with a light emitting element.
In addition, the light emitting element includes a light emitting diode (LED) and a semiconductor laser, and is mounted on the mounting surface of the first ceramic layer via a brazing material or a resin layer, or mounted on the conductor. Also good.

In the present invention, the first ceramic layer includes a cavity having a side surface and a mounting surface for the light emitting element, and the conductor is formed on the mounting surface (Claim 2). Is also included.
According to this, the light of the light emitting element mounted on the mounting surface or the conductor can be reflected to the side surface of the cavity and radiated to the outside, and the sealing resin is filled in the cavity. The mounted light emitting element can be sealed from the outside. In addition, since the heat generated by the light emitting element is effectively released to the outside through the first and second ceramic layers, stable light emission is possible.

The cavity has a circular shape in plan view and an overall cylindrical shape or substantially conical shape, an oval shape in plan view and an overall long cylindrical shape or substantially long cone shape, or an elliptical shape in plan view and the entire shape. Forms such as an elliptic cylinder or a substantially elliptic cone are included.
Further, the side surface of the cavity includes a vertical surface standing vertically from the periphery of the mounting surface, which is the bottom surface thereof, and an inclined surface inclined so as to expand obliquely upward.
Further, a light reflecting layer comprising a W or Mo metallized layer, a Ni plated layer, and an Ag plated layer may be formed on the side surface of the cavity.
In addition, the first ceramic layer having the cavity is formed of a ceramic layer having two layers, ie, an upper layer side having a through-hole having the side surface as an inner surface and a flat lower layer side having the mounting surface, or a multilayered ceramic. It is formed by stacking layers.

Furthermore, the present invention includes a wiring board (via claim 3) in which a via conductor is formed between the conductor formed on the mounting surface and the second ceramic layer.
According to this, since the heat generated by the light emitting element can be efficiently transferred to the second ceramic layer through the via conductor, it is possible to further improve the heat dissipation.
The via conductor is made of, for example, W, Mo, Ag, or Cu, and is provided between the mounting surface on which the light emitting element is mounted and at least the surface of the second ceramic layer, and between the mounting surface and the inside of the second ceramic layer. Or between the mounting surface and the back surface of the second ceramic layer, at least one is formed along the via hole formed in the first ceramic layer.

In the following, the best mode for carrying out the present invention will be described.
1 is a plan view showing a wiring board 1a according to an embodiment of the present invention, FIG. 2 is a vertical sectional view taken along line XX in FIG. 1, and FIG. 3 is a partially enlarged view in FIG. It is sectional drawing. As shown in FIGS. 1 and 2, the wiring substrate 1 a has a first ceramic layer s <b> 1 having a substantially square shape in plan view and having a mounting surface 6, and a second ceramic layer laminated on the opposite (lower layer) side of the mounting surface 6. A substrate body 2a composed of the ceramic layer s2 is provided.
The first ceramic layer s1 includes an upper ceramic layer s1a having a surface 3 of the substrate body 2a and a side surface 7a forming a cavity 5a, and a lower ceramic layer s1b having a mounting surface 6 which is a bottom surface of the cavity 5a. Laminated. The first ceramic layer s1 is mainly composed of alumina and has a whiteness higher than that of the second ceramic layer s2.

As shown in FIG. 2, the second ceramic layer s2 has a back surface 4 of the substrate body 2a, and a W or Mo metal powder (metal component) having an average particle size of 10 μm or less with respect to the ceramic matrix phase in alumina or the like. ) Is contained in an amount of 5 to 50 wt%, and the thermal conductivity is higher than that of the first ceramic layer s1. If the content of the metal powder is less than 5 wt%, the improvement in thermal conductivity is insignificant. On the other hand, if the content exceeds 50 wt%, a short circuit may occur between wiring layers to be incorporated. It is a range.
As shown in FIGS. 1 and 2, the cavity 5a includes a mounting surface 6 that is circular in plan view, and a side surface 7a that is inclined so as to expand from the periphery of the mounting surface 6 toward the surface 3 of the substrate body 2a. The whole has a substantially conical shape. The elevation angle of the side surface 7a is approximately 30 to 70 degrees.

As shown in FIGS. 2 and 3, a large pad (conductor) 8 that is rectangular in plan view and a small pad (conductor) 9 that is adjacent to and spaced from the center are provided at the center of the mounting surface 6. Is formed. The large pad 8 is obtained by coating the surface of a W or Mo metallization layer 16 with a Ni plating layer 17 and an Ag plating layer 18. The uppermost Ag plating layer 18 is covered with a light emitting diode via a brazing material (not shown). (Light emitting element: hereinafter referred to as LED) 10 is mounted.
On the other hand, the small pad 9 is obtained by coating the same metallized layer 16 with the Ni plating layer 17 and the uppermost Au plating layer 19 and is connected to the LED 10 via a bonding wire (not shown). Is done. The surface layer of the pad 8 may be covered with an Au plating layer 19 instead of the Ag plating layer 18.

As shown in FIG. 2, a via conductor 11 connected to the pads 8 and 9 penetrates through the lower ceramic layer s1a of the first ceramic layer s1, and is between the first and second ceramic layers s1 and s2. Are connected to a plurality of wiring layers 12 formed on the substrate. The wiring layer 12 is individually connected to a plurality of terminals 14 formed near the periphery of the back surface 4 of the substrate body 2a through via conductors 13 penetrating the second ceramic layer s2. That is, the pads 8 and 9 are electrically connected to the terminal 14 via the via conductors 11 and 13 and the wiring layer 12. Furthermore, a plurality of via conductors 15 located between the pad 8 on which the LED 10 is mounted and the back surface 4 of the substrate body 2a penetrate the lower ceramic layer s1a and the second ceramic layer s2 of the first ceramic layer s1. is doing.
The via conductors 11, 13, 15, the wiring layer 12, and the terminal 14 are made of W or Mo as described above. In addition, a wiring layer (not shown) connected to the via conductors 11 and 13 may be formed inside the ceramic layer s1a and the second ceramic layer s2. Further, the via conductor 15 may be formed only between the pad 8 and the second ceramic layer s2, or the lower end may be located inside the second ceramic layer s2.

The wiring board 1a was manufactured as follows.
A ceramic slurry was previously prepared by mixing alumina powder, a resin binder, a solvent, and the like, and a first green sheet for a plurality of first ceramic layers s1 was manufactured by using the ceramic slurry by a doctor blade method. Separately, a ceramic slurry containing 5 to 50 wt% of Mo powder having an average particle size of 10 μm or less with respect to the alumina powder or the like is prepared, and the same method as described above is applied to the second ceramic. A second green sheet for the layer s2 was obtained.
One of the first green sheets was punched with a punch and a die having an inner diameter receiving hole larger than the outer diameter of the punch, and a through hole having an inclined inner peripheral surface was formed. .

The remaining first green sheet and second green sheet were punched with a small-diameter punch and a die with a receiving hole having substantially the same diameter to form a plurality of via holes. Via conductors 11, 13, and 15 were formed by filling the via holes with a conductive paste containing Mo powder.
Next, the same conductive paste as described above is screen-printed on at least one of the front and back surfaces of the remaining first green sheet and second green sheet, and the metallized layer 16, the wiring layer 12, and the terminals of the pads 8 and 9. 14 was formed. In place of the Mo powder, W powder may be used, or the remaining first green sheet and second green sheet may be formed in plural, and a wiring layer having a predetermined pattern may be formed between them.

Furthermore, from the upper layer side, a first green sheet in which a through hole having an inclined inner surface is formed, and the remaining first first layer in which the metallized layer 16 of the pads 8 and 9, the via conductors 11 and 15, and the wiring layer 12 are formed. A green sheet and a second green sheet on which the via conductors 13 and 15 and the terminals 14 were formed were sequentially laminated and pressed to form a green sheet laminate having the cavity 5a.
And after baking this green sheet laminated body in a predetermined temperature range, Ni plating and Ag plating or Au plating were sequentially coated on the surfaces of the metallized layers 16 and the terminals 14 of the pads 8 and 9.
As a result, the wiring board 1a provided with the first and second ceramic layers s1, s2, the cavity 5a, the mounting surface 6, the pads 8, 9 and the like could be manufactured.
Each of the above steps may be performed in the form of multiple pieces, and then fired in the same manner as described above, and a plurality of wiring boards 1a may be manufactured simultaneously by cutting and dividing the Ag and Au plated ceramic laminate. good.

According to the wiring board 1a as described above, when the LED 10 is mounted on the pad 8, the heat generated by the LED 10 passes through the first ceramic layer s1 and the second ceramic layer s2, and the board body 2a is heated. Heat can be effectively radiated from the back surface 4 side to the outside. Further, the heat dissipation can be further promoted by the plurality of via conductors 15 that penetrate the first and second ceramic layers s1 and s2 from the pad 8 and reach the back surface 4 of the substrate body 2a. On the other hand, the light emitted from the LED 10 to be mounted can be efficiently reflected on the white mounting surface 6 and the side surface 7a of the cavity 5a having high whiteness to be emitted to the outside.
In addition, since the substrate body 2a is formed only by the first and second ceramic layers s1 (s1a, s1b) and s2, a space for a through hole for inserting a heat radiating member as in the prior art becomes unnecessary, and a required wiring layer 12 or the like can be formed between or inside the first and second ceramic layers s1 and s2. In addition, it is not necessary to form a through hole for inserting the heat radiating member in the central portion of the substrate body 2a in a plurality of green sheets or to set and braze the heat radiating member in the through hole. Therefore, it becomes possible to manufacture with simple and few processes.

FIG. 4 is a plan view showing a wiring board 1b of a different form, and FIG. 5 is a vertical sectional view taken along the line YY in FIG.
4 and 5, the wiring substrate 1b includes a first ceramic layer s1 having a cavity 5b including the mounting surface 6, and a second ceramic layer s2 stacked on the opposite (lower layer) side of the mounting surface 6. A substrate main body 2b is provided.
The first ceramic layer s1 includes an upper ceramic layer s1c having a surface 3 of the substrate body 2b and a side surface 7b forming a cavity 5b, and a lower ceramic layer s1a having a mounting surface 6 which is a bottom surface of the cavity 5b. Laminated. The first ceramic layer s1 has a higher whiteness than the second ceramic layer s2 as described above.
As shown in FIG. 5, the second ceramic layer s2 has a back surface 4 of the substrate body 2b and contains the same W or Mo metal powder as described above, and has a thermal conductivity higher than that of the first ceramic layer s1. Is expensive.
As shown in FIGS. 4 and 5, the cavity 5b includes a mounting surface 6 that is circular in plan view, and a side surface 7b that stands vertically from the periphery of the mounting surface 6 toward the surface 3 of the substrate body 2b. The whole has a substantially cylindrical shape.

As shown in FIGS. 4 and 5, pads (conductors) 8 and 9 similar to those described above are formed in the central portion of the mounting surface 6, and the LED 10 is mounted on the large pad 8, and a small size is achieved. Similarly to the above, the pad 9 is electrically connected to the LED 10 via a bonding wire (not shown).
As shown in FIG. 5, in the first ceramic layer s1, the lower via layer ceramic layer s1a is penetrated by the same via conductor 11, and the wiring layer 12 between the first and second ceramic layers s1 and s2 and It is connected. The wiring layer 12 is connected to a plurality of terminals 14 formed on the back surface 4 of the substrate body 2b through the same via conductors 13 as described above. Further, a plurality of via conductors 15 similar to those described above penetrate through the ceramic layer s1a and the second ceramic layer s2.

The wiring board 1b could be manufactured by the same method as the wiring board 1a except that a through hole having the side surface 7b was punched into the first green sheet.
According to the wiring board 1b as described above, similar to the wiring board 1a, it can be manufactured with excellent heat dissipation from the LED 10, excellent radiation of light from the LED 10, and relatively simple and less man-hours. There is an effect.

FIG. 6 is a plan view showing a wiring board 1c which is a modification of the wiring board 1a. The wiring board 1c also includes a substrate body 2a composed of a first ceramic layer s1 (s1a, s1b) and a second ceramic layer s2 similar to the above, a cavity 5a, and the like. The wiring board 1c is different from the wiring board 1a in that the mounting surface 6 which is the bottom surface of the cavity 5a occupies most of the area of the mounting surface 6 and is substantially circular in plan view as shown in FIG. In addition, the pad (conductor) 8a having a partially cut shape and the substantially crescent-shaped pad (conductor) 9a in the plan view are formed on the remaining mounting surface 6.
The pad 8a includes the same metallized layer 16, Ni plated layer 17, and Ag plated layer 18 as described above, and reflects light emitted from the LED 10 mounted at the center thereof. Such light is also reflected on the Ag plating layer 18 or the side surface 7a of the cavity 5a and emitted to the outside. On the other hand, the pad 9a includes the metallized layer 16, the Ni plating layer 17, and the Au plating layer 19 similar to those described above, and is electrically connected to the LED 10 by a bonding wire (not shown).

FIG. 7 is a plan view showing a wiring board 1d which is a modification of the wiring board 1b. The wiring substrate 1d also includes a substrate body 2b, a cavity 5b, and the like that are composed of the same first ceramic layer s1 (s1a, s1c) and the second ceramic layer s2. The wiring board 1d is different from the wiring board 1b in that the same pads 8a and 9a are formed on the mounting surface 6 of the cavity 5b as shown in FIG. The light emitted from the LED 10 mounted at the center of the pad 8a is reflected by the pad 8a and the side surface 7b of the cavity 5b and radiated to the outside.
The wiring boards 1c and 1d as described above are manufactured in the same manner as the wiring boards 1a and 1b. In the same manner as the wiring boards 1a and 1b, the heat dissipation from the LED 10 is excellent, and the light from the LED 10 is transmitted. The effect of being excellent in radioactivity and being relatively simple and capable of being manufactured with a small number of man-hours can be achieved.

8 is a plan view showing a further different form of the wiring board 1e, FIG. 9 is a vertical sectional view taken along the line ZZ in FIG. 8, and FIG. 10 is a partially enlarged sectional view in FIG. It is.
As shown in FIGS. 8 and 9, the wiring substrate 1 e has a first ceramic layer s <b> 1 that has a substantially square shape in plan view and has a mounting surface 3 that is a surface, and is laminated on the opposite (lower layer) side of the mounting surface 3. The substrate main body 2 including the second ceramic layer s2 is provided.
The first ceramic layer s1 is mainly composed of alumina, has a mounting surface 3 that is the surface of the substrate body 2, and has a higher whiteness than the second ceramic layer s2.
As shown in FIG. 9, the second ceramic layer s2 has the back surface 4 of the substrate body 2, and 5 or less of W or Mo metal powder (metal component) having an average particle size of 10 μm or less with respect to the ceramic such as alumina. -50 wt% is contained, and the thermal conductivity is higher than that of the first ceramic layer s1.

As shown in FIGS. 8 to 10, the same pads 8 and 9 are formed in the central portion of the mounting surface 3, and the large pad 8 has the Ni plating layer 17 and the surface of the same metallized layer 16. The LED 10 is mounted on the uppermost Ag plating layer 18 via a brazing material (not shown). On the other hand, the small pad 9 is obtained by coating the same metallized layer 16 with the Ni plating layer 17 and the uppermost Au plating layer 19 and is connected to the LED 10 via a bonding wire (not shown). Is done. The surface layer of the pad 8 may be covered with an Au plating layer 19 instead of the Ag plating layer 18.
As shown in FIG. 9, via conductors 11 connected to the pads 8 and 9 pass through the first ceramic layer s1, and a plurality of wiring layers 12 formed between the first and second ceramic layers s1 and s2. Connected. The wiring layer 12 is connected to a plurality of terminals 14 formed near the periphery of the back surface 4 of the substrate body 2 via via conductors 13 penetrating the second ceramic layer s2. Further, a plurality of via conductors 15 located between the pad 8 on which the LED 10 is mounted and the back surface 4 of the substrate body 2 pass through the first and second ceramic layers s1 and s2.

The wiring board 1e as described above could be manufactured in the same manner as the wiring boards 1a and 1b except for the step of forming the cavities 5a and 5b.
According to the wiring board 1e, when the LED 10 is mounted on the pad 8, the heat generated by the LED 10 passes through the first and second ceramic layers s1 and s2 from the back surface 4 side of the board body 2 to the outside. Can effectively dissipate heat. Furthermore, since the plurality of via conductors 15 that penetrate the first and second ceramic layers s1 and s2 from the pad 8 and reach the back surface 4 of the substrate body 2 are formed, the heat dissipation can be further promoted. In addition, the light emitted from the mounted LED 10 can be efficiently reflected on the mounting surface 3 of the first ceramic layer s1 having high whiteness and radiated to the outside.
In addition, since the substrate body 2 is formed only by the first and second ceramic layers s1 and s2, the wiring layer 12 and the like are interposed between the first and second ceramic layers s1 and s2 as compared with a conventional structure in which a heat dissipation member is inserted. Or they can be easily formed inside. In addition, a through hole for inserting the heat radiating member into the substrate body 2 is not formed in a plurality of green sheets, and a process of setting and brazing the heat radiating member in the through hole is not necessary. It is possible to manufacture with few processes.

FIG. 11 is a plan view showing a wiring board 1f which is a modification of the wiring board 1e. The wiring board 1f also includes a substrate body 2 composed of the same first and second ceramic layers s1 and s2, a wiring layer 12, via conductors 11 and 13, terminals 14 and the like.
The wiring board 1f is different from the wiring board 1e in that the mounting surface 3 of the first ceramic layer s1 occupies most of the mounting surface 3 and has a rectangular plan view 8b and a plan view provided near one side of the pad 8b. This is that a small pad 9b is formed in the rectangular cutout portion 8d and spaced from the periphery of the cutout portion 8d.
The pad 8b includes the metallized layer 16, the Ni plating layer 17, and the Ag plating layer 18 similar to the above, and reflects and emits the light emitted from the LED 10 mounted in the center thereof to the outside. On the other hand, the pad 9b includes the metallized layer 16, the Ni plating layer 17, and the Au plating layer 19 similar to those described above, and is electrically connected to the LED 10 by a bonding wire (not shown).

FIG. 12 is a plan view showing a wiring board 1g which is a different modification of the wiring board 1e. The wiring board 1g also includes a substrate main body 2 composed of the first and second ceramic layers s1 and s2, and the wiring board 1g. Layer 12, via conductors 11 and 13, terminals 14 and the like are provided. The wiring board 1g is different from the wiring board 1e in that the mounting surface 3 of the first ceramic layer s1 occupies most of the mounting board 3 and is substantially rectangular in plan view, and a plan view provided on one side of the pad 8c. Is that a small pad 9b spaced from the edge of the notch 8e is formed in the substantially rectangular notch 8e. The pads 8c and 9b are the same as the pads 8b and 9b of the wiring board 1f.
The wiring boards 1f and 1g can also be manufactured in the same manner as the wiring board 1e, and the same effects as the wiring board 1e can be obtained.
Further, in the wiring boards 1f and 1g, the via conductors 15 penetrating the first and second ceramic layers s1 and s2 are formed on the peripheral side of the pads 8b and 8c, so that the back surface 4 of the substrate body 2 is formed. It becomes possible to directly contact the plurality of terminals 14 positioned, and the heat of the LED 10 can be radiated more efficiently.

Here, specific examples of the present invention will be described together with comparative examples.
A predetermined amount of alumina powder, resin binder, solvent, etc. was previously blended into a ceramic slurry, and a plurality of first green sheets for the first ceramic layer s1 were produced from the ceramic slurry by a doctor blade method. Separately, a ceramic slurry in which Mo powder having an average particle size of 10 μm or less is further contained in a proportion of 30 wt% with respect to the above-described alumina and the like is applied to the second ceramic layer s 2. A plurality of second green sheets were produced.
Further, some of the first green sheets were penetrated through a plurality of via holes and filled with a conductive paste containing W or Mo powder to form a plurality of via conductors 15a and 15b individually.

Next, after laminating the second green sheet on the lower layer side opposite to the mounting surface 3 of the first green sheet, these are fired, and as shown at the left end of FIG. 13, the first and second ceramic layers s1, s2 The substrate body of Example 1 having the mounting surface (front surface) 3 and the back surface 4 was formed. The first ceramic layer s1 has a thickness of 1 mm, and the second ceramic layer s2 has a thickness of 150 μm. These are cylindrical bodies having a diameter of 10 mm in plan view.
Further, the second green sheet is laminated on the lower layer side of the first green sheet through which the plurality of via conductors 15a made of W penetrate, and these are fired, and as shown in the central left side of FIG. The substrate main body of Example 2 having the via conductor 15a, the mounting surface 3, and the back surface 4 was formed.
Further, the second green sheet is laminated on the lower layer side of the first green sheet through which the plurality of via conductors 15b made of Mo penetrate, and these are fired, and as shown in the center right side of FIG. The substrate main body of Example 3 having the via conductor 15b, the mounting surface 3, and the back surface 4 was formed. The plurality of via conductors 15a and 15b occupy 25% of the volume in the first ceramic layer s1 as a whole, and their lower ends were in contact with the second ceramic layer s2.

In addition, the first green sheet is laminated in two upper and lower layers, and these are fired, and as shown at the right end of FIG. 13, the entire upper and lower first ceramic layers s1 having the same thickness and shape as described above are used. Thus, the substrate body of the comparative example having the mounting surface 3 and the back surface 4 was formed.
By sequentially heating the mounting surface 3 side of each of the substrate bodies of Examples 1 to 3 and the comparative example from room temperature to 400 ° C. with a laser, and measuring the heat propagated from the mounting surface 3 to the back surface 4 for each example, The specific heat and the thermal expansion rate were measured, and the thermal conductivity between the mounting surface 3 and the back surface 4 for each example was calculated based on these two parameters. The results are shown in the graph of FIG. In addition, between the mounting surface 3 and the back surface 4 for each example, heat insulation was performed by arranging a heat insulating material in the middle of the peripheral surface (side surface) for each substrate body of each example.

As shown in the graph of FIG. 14, the thermal conductivity of Example 1 is higher by about 1 to 2 W / m · K at each temperature from room temperature to 400 ° C. compared to the comparative example. Compared with the comparative example, the temperature was about 4 to 5 W / m · K at each temperature from room temperature to 400 ° C.
The reason why the thermal conductivity of Example 3 is slightly higher than that of Example 2 is estimated to be due to the difference between the materials W and Mo of the via conductors 15a and 15b.
The effects of the wiring board according to the present invention including the first and second ceramic layers s1 and s2 were supported by Examples 1 to 3 as described above.

The present invention is not limited to the embodiments described above.
For example, the first and second ceramic layers s1 and s2 may be low-temperature fired ceramics made of glass-alumina. In such a form, the metallized layers 16 such as the pads 8 and 9 and the via conductors 11, 13 and 15, The metallized layer of the terminal 14 such as the wiring layer 12 may be formed of Ag or Cu, or Ag or Cu powder may be used for the metal component of the second ceramic layer s2.
A plurality of light emitting elements may be mounted on the pads 8a to 8c having a relatively large area.
Further, two small pads 9, 9a, 9b may be arranged symmetrically on both sides of the large pads 8a-8c. In such a form, the LED 10 can be mounted by a resin layer.
In addition, the cavities 5a and 5b of the wiring boards 1a to 1d may be filled and solidified with a light-transmitting sealing resin after the LEDs 10 are mounted on the mounting surfaces 6 thereof.

The top view which shows the wiring board of one form in this invention. FIG. 2 is a vertical sectional view taken along line XX in FIG. 1. The partial expanded sectional view in FIG. The top view which shows the wiring board of a different form. FIG. 5 is a vertical sectional view taken along the line Y-Y in FIG. 4. The top view which shows the deformation | transformation form of the wiring board shown to FIG. The top view which shows the deformation | transformation form of the wiring board shown to FIG. Furthermore, the top view which shows the wiring board of a different form. FIG. 9 is a vertical sectional view taken along the line ZZ in FIG. 8. The partial expanded sectional view in FIG. The top view which shows the deformation | transformation form of the wiring board shown to FIG. The top view which shows the different deformation | transformation form of the wiring board shown to FIG. Schematic which shows an Example and a comparative example. The graph which shows the relationship between the temperature and thermal conductivity of an Example and a comparative example.

Explanation of symbols

1a to 1g ……………… Wiring substrate 3, 6 …………………… Mounting surface 5a, 5b ……………… Cavity 7a, 7b ……………… Side surface 8, 8a-8c… ……… Pad (conductor)
9, 9a, 9b ………… Pad (conductor)
10 ………………………… LED (light emitting element)
15 ... …………………… Via conductor 18 ……………………… Ag plating layer 19 ……………………… Au plating layer s1 (s1a to s1c)… first ceramic layer s2 ……………………… Second ceramic layer

Claims (3)

A first ceramic layer having a light emitting element mounting surface;
A second ceramic layer containing a metal component and laminated on the opposite side of the mounting surface of the first ceramic layer, and having a higher thermal conductivity than the first ceramic layer;
A conductor formed on the mounting surface and having a surface layer coated with at least one of an Ag plating film and an Au plating film,
A wiring board characterized by that. The first ceramic layer includes a cavity having a side surface and a mounting surface for the light emitting element, and the conductor is formed on the mounting surface.
The wiring board according to claim 1. A via conductor is formed between the conductor formed on the mounting surface and the second ceramic layer.
The wiring board according to claim 1 or 2, wherein

Images