JP2003124408A - Heat radiative substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiative substrate having electrically conductive via holes for mounting a semiconductor in which high heat radiation characteristics are maintained, even when the semiconductor element for high optical output is mounted and large current is allowed to flow, and connectivity between the semiconductor element and the substrate is not deteriorated, and a breakage is not caused even when the substrate is repeatedly used. SOLUTION: The radiative substrate includes as a component member a ceramic substrate having a mount surface on which the semiconductor element is mounted and via holes passing through both the end surfaces of the substrate and filled with an electric conductive material such as tungsten are provided. In the part of the mount surface on which the semiconductor element is mounted, a plurality of via holes having the diameter of 0.05 to 0.5 mm are disposed so that the total area of the exposed end faces of the electric conductive materials occupies 5 to 40% of that part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be used as a heat dissipating substrate having a via hole which can be suitably used as a heat sink or a submount, and more particularly as a submount for a semiconductor laser element having conductivity between the semiconductor laser element and the heatsink. Heat dissipation substrate. More specifically, the present invention relates to a heat dissipation substrate that can be used as a submount on which a high-power laser element can be mounted.

[0002]

2. Description of the Related Art A submount is an insulating substrate located between a semiconductor laser element and a heat sink (a block made of metal such as copper), and has a capability of efficiently transferring heat generated from the semiconductor laser element to the heat sink side. Is to have.

In a general submount for a semiconductor laser device, as shown in Japanese Patent No. 316577, circuit patterns are provided on both surfaces of an insulating substrate, and a via hole penetrating between both surfaces is filled with a conductive material. By doing so, the circuit patterns on these two surfaces are electrically connected. And a semiconductor laser element on one side,
It is used by bonding a heat sink to the other side by soldering or the like.

[0004]

Conventionally, the optical output of a semiconductor element required for a laser light source for optical discs is several 1
Although it was about 0 mW, high output lasers for laser processing and medical fields, which are under development in recent years, are required to increase the optical output to W level. In the conventional submount, since the optical output of the mounted semiconductor element is not so high, the number of vias may be small, and the resistance between the front and back surfaces of the submount is about 20 mΩ. However, when a semiconductor element for high light output is mounted and used on such a conventionally used submount, it is necessary to flow a large current for high output, so heat is generated in the via hole of the submount, It has been found that not only the function as a heat dissipation substrate cannot be fulfilled, but also the heat generated causes damage to the semiconductor element and deterioration of the function. Therefore, an object of the present invention is to provide a heat dissipation board having a novel structure that can be used as a submount on which a high-power semiconductor element can be mounted.

[0005]

The inventors of the present invention have considered that the above problem can be solved by increasing the diameter of the via hole to reduce the resistance between the front and back surfaces of the submount, and have studied. Although it is possible to reduce heat generation in the via hole, if the via hole is formed immediately below the semiconductor element due to design requirements, increasing the via hole diameter will increase the sub-size of the semiconductor element after long-term use. It has become clear that a new problem occurs that the bonding state to the mount is deteriorated and the durability of the element is reduced. Therefore, a method for reducing heat generation in the via hole without causing such a problem was further investigated. As a result, in the above-described embodiment, when a large number of via holes having small hole diameters are uniformly dispersed and arranged, heat generation in the via holes can be reduced without causing problems such as deterioration in adhesion of the semiconductor element. And that the diameter of the via hole is within a specific range, and the total area of the exposed end faces of the conductive material filled in the via hole is the area of the portion where the semiconductor element is mounted (corresponding to the area of the bonding surface of the semiconductor element). The inventors have found that the above effect can be stably obtained when the ratio of) is within a specific range, and completed the present invention.

That is, the present invention is a ceramic substrate having a mounting surface for mounting a semiconductor element, wherein the mounting surface penetrates between both surfaces of the substrate, and a conductive substance is contained therein. In a heat dissipation substrate including a ceramic substrate having a filled via hole as a constituent member, a total area of exposed end faces of the conductive material occupying the portion of the mounting surface where the semiconductor element is mounted is 5 to 5 The heat dissipation substrate is characterized in that a plurality of via holes having a hole diameter of 0.05 to 0.5 mm are arranged so as to be 40%.

The heat dissipation board of the present invention not only exhibits high heat dissipation characteristics with little heat generation in the via hole even when a high power semiconductor element is placed and used directly on the via hole, but also can be used for a long time. Also has a feature that the bondability of the element is not easily deteriorated or the element is not easily damaged. Among the heat dissipation substrates of the present invention, the ceramic substrate made of aluminum nitride, silicon carbide, beryllium oxide, or a ceramic containing any of these as a main component has particularly high heat dissipation characteristics and stability during use. When a conductive layer (metallized layer) is formed on the mounting surface of the ceramic substrate and the entire back surface thereof, the electric resistance value at 25 ° C. between both conductive layers is 1 mΩ or less, and
It is also possible to realize excellent characteristics as a submount having a thermal conductivity of 170 W or more at 5 ° C.

In the present invention, by arranging a large number of via holes each having a small hole diameter, the conductor cross-sectional area as a whole is increased to reduce the total resistance, the via holes are dispersed, and the semiconductor element is manufactured. The thermal expansion coefficient of the semiconductor element and the conductive substance filled in the via hole is so arranged that the semiconductor element comes into contact with the ceramic having a thermal expansion coefficient close to that of the material at a certain ratio or more when mounted. It is considered that such an excellent effect is exerted because the stress caused by the difference is dispersed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The heat dissipation substrate of the present invention will be described below with reference to the drawings. FIG. 1 shows a top view A and a sectional view B of a typical heat dissipation board of the present invention. A heat dissipation substrate 1 of the present invention shown in the figure is a ceramic substrate 3 having a mounting surface 2 on which a semiconductor element (not shown) is mounted. Including a ceramic substrate having a via hole 4 filled with a conductive material inside as a constituent member, and having the same cross-sectional area s (where the semiconductor element is mounted on the mounting surface 2). s has a basic structure in which a plurality of via holes 4 having an exposed surface of the conductive material filled in the via holes are arranged. Then, the ceramic substrate 3
A conductive layer 6 is formed on the entire upper surface of the mounting surface 2 and the solder layer 7 is formed on the portion 5 where the semiconductor element is mounted.
Are formed. Further, the conductive layer 6 is formed on the entire back surface (the surface opposite to the mounting surface) of the ceramic substrate 3.
Are formed. In the top view A, the end face of the conductive material filled in the via hole is shown by a dotted line in order to make the position of the via hole 4 easy to understand, but as shown in cross-sectional view B, a conductive layer is formed above it. 6 and a solder layer 7.

A known ceramic material can be used as the ceramic constituting the above-mentioned ceramic substrate, but it is preferable to use one having a high thermal conductivity in order to obtain high heat dissipation characteristics. Examples of ceramic materials that can be preferably used include aluminum nitride, beryllium oxide, silicon carbide, and ceramics containing any of these as a main component. Among these, aluminum nitride or ceramics containing aluminum nitride as a main component has a high thermal conductivity, so that the heat generated from the semiconductor laser element is efficiently released to the heat sink, and Si, which is a typical material of the semiconductor laser element, and thermal expansion. It is particularly preferably used because a heat dissipation board having a coefficient close to the element and having excellent stability when the element is mounted and used can be obtained. A thermal conductivity of 170 W can be obtained by using the above-mentioned suitable ceramic material, particularly an aluminum nitride ceramic material.
It is possible to obtain a heat dissipation substrate having a heat dissipation rate of / mK or more, and further 190 W / mK or more. 1 shows a plate-shaped ceramic substrate, the shape of the ceramic substrate used in the present invention is not limited to such a plate-shaped substrate, a mounting surface on which a semiconductor element is mounted. Any shape can be used as long as it has the following.
The surface roughness of the ceramic substrate varies depending on the purpose, but is usually Ra ≦ 0.8 μm, and more preferably Ra ≦ 0.8 μm.
The thickness of 0.05 μm is preferable because the reliability of die attachment of the semiconductor element is improved.

The ceramic substrate used as a constituent member of the heat dissipation substrate of the present invention can be supplied with power for driving the semiconductor element mounted on the mounting surface from the back surface of the substrate. For this purpose, a via hole (corresponding to 4 in FIG. 1) is formed penetrating both sides of the ceramic substrate and filled with a conductive substance. As the conductive substance filled in the via hole, a metal material usually used for such a purpose can be used without particular limitation. For example, such a via hole is formed by the co-firing method (C
When it is formed by the o-fire method), tungsten or molybdenum is preferably used because it has good heat resistance to high temperatures during firing and has relatively high electric conductivity. In addition, the via hole is post-fired (Post-fire method).
e method), because of high electrical conductivity,
At least one selected from the group consisting of copper, silver, gold, nickel, and palladium is preferably used. The via hole filled with the metal material as the conductive material is also referred to as a metal via hole hereinafter.

In the heat dissipation board of the present invention, a via hole filled with a conductive material such as a metal via hole is provided at a portion (corresponding to 5 in FIG. 1) of the mounting surface of the ceramic substrate on which the semiconductor element is mounted. The via hole arranged in this portion has a hole diameter of 0.05 to 0.5 mm, the number of arrangement is 2 or more, and the area of the exposed end surface of the conductive material occupying the portion (see FIG. The total ratio (corresponding to s of 1) (hereinafter, also simply referred to as conductive material area occupancy) is 5
It should be arranged so as to satisfy the condition of being -40%. The via holes are arranged on the mounting surface of the ceramic substrate where the semiconductor elements are mounted for the design reason based on the usage of the heat dissipation substrate, but the via holes are mounted on the mounting surface of the semiconductor elements. In the case of arranging in a site other than the site to be placed, even if the hole diameter of the via ball is made as large as possible, the problem of deterioration in stability and durability during use such as deterioration of the element bonding state does not occur. Further, when the diameter of the via hole is larger than 0.5 mm or the conductive material area occupancy ratio is larger than 40%, the deterioration of stability and durability during use cannot be avoided. Also,
It is technically difficult to make it less than 0.05 mm, and when the number of via holes is 1 or the conductive material area occupancy rate is less than 5%, the heat dissipation of the via holes during use deteriorates the heat dissipation characteristics. By satisfying such a condition, when a conductive layer (metallized layer) is formed on the entire mounting surface of the ceramic substrate and the back side thereof, the electric resistance value at 25 ° C. between both conductive layers is 1 mΩ or less, and further, It is also possible to set it to 0.7 mΩ or less. The via hole is the above-mentioned portion (corresponding to 5 in FIG. 1) from the viewpoint of high stability or durability when mounted with a high-power semiconductor element and low heat generation in the via hole.
It is preferable to disperse the via holes substantially uniformly over the entire surface, and to arrange a plurality of via holes having a hole diameter of 0.1 to 0.3 mm in an area ratio of the conductive material of 6 to 30%, particularly 6 to 20.
It is more preferable to disperse them evenly so as to have a ratio of%.

The heat dissipation substrate of the present invention is not particularly limited as long as the via hole includes the ceramic substrate arranged as described above as a constituent member, but at least the semiconductor element on the mounting surface of the ceramic substrate is mounted. It is preferable that the conductive layer (corresponding to 6 in FIG. 1) is formed so as to cover all the exposed surface of the conductive material filled in the via holes arranged on the front surface of the portion to be placed and the rear surface thereof. is there. Further, on the surface of the mounting surface of the ceramic substrate at least the portion where the semiconductor element is mounted, on the conductive layer,
It is preferable that a solder layer (corresponding to 7 in FIG. 1) for reflow soldering the semiconductor element is further formed.

In the present invention, the conductive layers formed on both sides of the insulating substrate are not particularly limited as long as they are conductive layers, but a metal film layer is usually used. As the material of the metal film, any known metal can be used without particular limitation as long as it is a metal capable of forming a film having adhesiveness on a ceramic substrate. When a ceramic substrate made of aluminum nitride or aluminum nitride-based ceramic is used From the viewpoint of adhesion, it is preferable to use at least one metal selected from the group consisting of titanium, chromium, molybdenum, tungsten, tungsten titanium, aluminum, nickel chromium, and tantalum. The conductive layer may have a multi-layer structure. When the conductive layer is composed of a laminate of two or more layers, a film made of a conductive material having good adhesion to the ceramic material is formed as the first layer, and electric conductivity and corrosion resistance are excellent on the film. However, it is preferable to form a layer of at least one selected from the group consisting of copper, nickel, palladium, platinum, and gold. The solder material forming the solder layer is not particularly limited, and known solder materials such as lead / tin solder, gold / tin solder, gold / silicon solder, and gold / germanium solder can be used without limitation. The solder layer may also have a multi-layer structure, and a metal layer for preventing diffusion of the solder material may be provided between the conductive layer and the solder layer. Platinum, tungsten, tungsten titanium, and molybdenum can be preferably used as the diffusion preventing layer.

The heat dissipation board of the present invention as described above may be formed, if necessary, after forming the via holes arranged so as to satisfy the above-mentioned conditions by, for example, the method of producing an insulating board having a metal via hole which is generally adopted. It is preferably manufactured by grinding or polishing the surface of the substrate by forming a conductive layer (conductive pattern) on both surfaces of the substrate and then forming a solder layer on the conductive layer on the mounting surface. As a method of manufacturing an insulating substrate having a metal via hole, a known technique can be used without limitation, and a cofire method or a postfire method can be preferably used.

When the co-firing method is adopted, a via hole is opened in the green sheet before firing by punching,
The via hole is filled with a metal paste by a printing method or a pressing method. Then, degreasing and firing are performed to obtain an insulating substrate having metal via holes. At this time, the firing temperature varies depending on the material of the insulating substrate, but is usually selected from the range of 1,000 to 2,000 ° C. For example, when the ceramic substrate is made of an aluminum nitride sintered body, it is fired at a temperature of 1,600 to 2,000 ° C, and more preferably 1,700 to 1,900 ° C.

When the post-fire method is adopted, a via hole is opened in the green sheet by punching or the like to degrease and fire it, or the green sheet or the press body is degreased and fired to obtain an insulating substrate. A ceramic substrate having a via hole can be obtained by forming a via hole in the substrate by laser processing, ultrasonic processing or the like, and then filling a metal paste and firing the ceramic substrate having a metal via hole. The firing temperature after filling the metal paste varies depending on the type of the metal paste, but it is usually fired at a temperature of 600 to 1,400 ° C.

The metal paste used for forming the metal via hole is a mixture of the above-mentioned powders of various metals with an organic binder such as ethyl cellulose and an organic solvent such as terpineol or butyl carbitol acetate. Can be used. At this time, in order to improve the adhesiveness of the metal paste, ceramic powder or active metal powder,
For example, when using an aluminum nitride substrate, it is also preferable to add aluminum nitride powder, titanium metal powder, or the like. The composition of the metal paste is usually 0.1 to 5 parts by weight of an organic binder, 1 to 20 parts by weight of an organic solvent, and 1 to 1 parts of the additive with respect to 100 parts by weight of the metal powder.
It is in the range of 0 parts by weight.

As a method for grinding or polishing the surface of the insulating substrate having the metal via holes obtained as described above as required, conventionally known methods such as lapping, polishing, barrel polishing, sand blasting, and polishing with a grinder are known. Method is used without limitation. In order to improve the reliability of die attachment of the semiconductor laser element, the substrate surface is R
It is preferable to polish so that a ≦ 0.8 μm, especially Ra ≦ 0.05 μm.

As a method of forming the conductive layer and the solder layer, a known film forming method such as a sputtering method, a vapor deposition method and an ion plating method can be adopted. For example, when the conductive layer is formed by the sputtering method, the substrate temperature is usually set to room temperature to 300 ° C., the inside of the vacuum chamber is evacuated to 2 × 10 ⁻³ Pa or less, and then Ar gas is introduced at 10 to 80 cc / min. Then, the conductive layer can be formed to a desired thickness by setting a pressure to 0.2 to 1.0 Pa and sputtering a predetermined target material with a power of an RF (high frequency) power source of 0.2 to 3 KW. The conductive layer or the solder layer can be patterned into a desired shape by adopting a metal mask method, a wet etching method, a dry etching method, or the like. For example, when patterning by a metal mask method, a metal mask on which a predetermined pattern is formed in advance is fixed on the insulating substrate,
The film may be formed by the sputtering method. Further, in the case of patterning by a dry etching method, a predetermined pattern is formed on the conductive layer by using a photoresist or the like on the insulating substrate on which the conductive layer is formed by a sputtering method or the like, and then conductive by ion milling or the like. After removing the layer, patterning may be performed by peeling the resist.

The insulating substrate having metal via holes with conductive patterns formed on both sides of the substrate obtained as described above is usually cut into a predetermined size to become the heat-radiating substrate of the present invention. Cutting can be performed by using a dicing machine, although known techniques can be used without limitation. The cutting is usually to cut the insulating substrate portion, but it is also possible to cut the metal via hole portion.

[0022]

EXAMPLES Examples will be shown below to more specifically describe the present invention, but the present invention is not limited to these examples.

Example 1 Centrifugal particle size distribution device manufactured by Horiba Seisakusho Co., Ltd. The average particle size measured by CAPA500 by the sedimentation method is 1.60 μm, the specific surface area is 2.5 m ² / g, and the specific surface area is S (m ² / g )), 100 parts by weight of aluminum nitride powder having an average particle diameter (D) calculated from “D (μm) = 6 / S × 3.26” of 0.74 μm was used as a sintering aid, and a specific surface area of 12. 5
5 parts by weight of m ² / g yttrium oxide powder, 15 parts by weight of butyl methacrylate as an organic binder and a dispersant,
Add 5 parts by weight of dioctyl phthalate as a plasticizer,
Toluene was mixed with a ball mill using a solvent. After degassing this slurry, the thickness is 0.6 m by the doctor blade method.
It was formed into a sheet of m. A sheet having a length of 64 mm and a width of 64 mm was cut out from this green sheet, 4,080 via holes having a diameter of 250 μm were formed by punching, and the tungsten paste was filled into the via holes by a pressing method. The green sheet having the tungsten via holes thus produced was degreased in a nitrogen atmosphere at 800 ° C., and then the degreased body was placed in an aluminum nitride setter and heated in a nitrogen atmosphere at 1,850 ° C. for 8 hours to obtain a diameter of 200 μm. An aluminum nitride substrate having a tungsten via hole of 54 mm in length, 54 mm in width and 0.4 mm in thickness was obtained. When the thermal conductivity of the obtained substrate was measured, it was 200 W / mK.

A heat dissipation substrate was produced using this aluminum nitride substrate. That is, the substrate is processed into a double-sided mirror-finished surface having a thickness of 0.3 mm (surface roughness Ra: 0.03 μm), and a conductive layer (first layer / second layer / third layer = Ti: 0.1 μm / Pt: 0.2 μm / Au: 1.0
(μm) by a sputtering method, and then AuS is formed on the entire surface.
n (Au = 80 wt%) solder (thickness 5 μm) was formed by vapor deposition. Next, the substrate on which the conductive layer and the solder layer were formed was dicing cut into a length of 12 mm and a width of 2 mm to prepare a heat dissipation substrate. There are 51 via holes under the solder layer of this heat dissipation substrate, and the area occupied by the conductive material at this time is 6.7%. Further, when the resistance was measured at 10 points between the front surface side and the back surface side of this heat dissipation substrate, the average resistance value was 0.41 mΩ.

Further, a length of 1 is provided on the surface side of the heat dissipation substrate.
After soldering a GaAs dummy element with a width of 2 mm, a width of 2 mm, and a thickness of 0.6 mm, the back side of the heat dissipation substrate is AuSn.
(Au = 80 wt%) Solder was bonded to a copper heat sink. When 40 A was applied to the dummy element for 5 minutes, the temperature rose to 39 ° C. After that, -50 ° C:
Hold for 30 minutes → 125 ° C .: Perform a heat cycle test with 1 cycle of holding for 30 minutes for 1,000 cycles, and then cut out a heat dissipation substrate to which a dummy element is joined into a 2 mm square,
When a shear strength test was performed on the dummy element and the heat dissipation substrate, the average shear strength was 4.6 kgf.

Example 2 Length 64 mm and width 6 produced in the same manner as in Example 1.
4mm, 0.6mm thick aluminum nitride green sheet was punched to form via holes with a diameter of 250μm.
680 pieces were formed, and the tungsten paste was filled in the via hole by a pressing method. After that, degreasing and firing are performed under the same conditions as in Example 1, and a tungsten via hole having a diameter of 200 μm is provided, a length of 54 mm, a width of 54 mm, and a thickness of 0.3 mm.
An aluminum nitride substrate of was obtained. The thermal conductivity of the obtained substrate was 206 W / mK.

The aluminum nitride substrate was polished, sputtered, vapor-deposited and cut in the same manner as in Example 1 to give a length of 12
A heat dissipation substrate having a width of 2.0 mm and a width of 2.0 mm was obtained. There are 96 via holes under the solder layer of this heat dissipation substrate, and the area occupied by the conductive material at this time is 12.6%. Further, when the resistance was measured in the same manner as in Example 1,
The average was 0.25 mΩ. Further, a dummy element made of GaAs was bonded in the same manner as in Example 1, and after bonding to the heat sink and 40A was energized for 5 minutes, the temperature rose to 35 ° C. After that, the heat cycle test was performed for 1,000 cycles in the same manner as in Example 1, the heat dissipation substrate was cut into 2 mm square, and the shear strength test was performed. The average shear strength was 4.
It was 1 kgf.

Example 3 A length of 64 mm and a width of 6 produced in the same manner as in Example 1.
Punch a 4 mm thick aluminum nitride green sheet with a diameter of 250 μm to 2 via holes.
0,720 pieces were formed. Then, degreasing and firing were performed under the same conditions as in Example 1 to obtain an aluminum nitride substrate having a via hole with a diameter of 200 μm, a length of 54 mm, a width of 54 mm, and a thickness of 0.3 mm. The thermal conductivity of the substrate is 195 W / mK
Met.

After polishing and sputtering this aluminum nitride substrate in the same manner as in Example 1, a conductive paste was embedded in the via hole and baked at 900 ° C. Then, the vapor deposition and cutting steps are performed in the same manner as in Example 1, and the length is 12 mm,
A heat dissipation substrate having a width of 2.0 mm was obtained. There are 259 tungsten via holes in this heat dissipation substrate, and the area ratio of the conductive material is 33.9%. When the resistance was measured in the same manner as in Example 1, the average was 0.12 m.
It was Ω. Further, when a dummy element made of GaAs was bonded in the same manner as in Example 1 and bonded to a heat sink and then 40A was applied to the dummy element for 5 minutes, the temperature rose to 28 ° C. Then, the heat cycle test was conducted for 1,000 cycles in the same manner as in Example 1, the heat dissipating substrate was cut into 2 mm square, and the shear strength test was conducted. The average shear strength was 3.3 kgf. .

Comparative Example 1 Length 64 mm and width 6 produced in the same manner as in Example 1.
A 4 mm thick 0.6 mm thick aluminum nitride green sheet is punched to form a via hole with a diameter of 250 μm.
360 pieces were formed, and the tungsten paste was filled into the via holes by a pressing method. After that, degreasing and firing were performed under the same conditions as in Example 1 to obtain a tungsten via hole having a diameter of 200 μm.
54mm, width 54mm, thickness 0.3mm
An aluminum nitride substrate of was obtained. The thermal conductivity of the substrate was 208 W / mK.

The aluminum nitride substrate was polished, sputtered, vapor-deposited and cut in the same manner as in Example 1 to give a length of 12
A heat dissipation substrate having a width of 2.0 mm and a width of 2.0 mm was obtained. This heat dissipation substrate has 17 via holes, and the conductive material area occupancy rate is 2.2%. When the resistance was measured in the same manner as in Example 1, the average was 1.12 mΩ. Further, a GaAs dummy element was bonded in the same manner as in Example 1 and, after bonding to the heat sink, 40A was energized for 5 minutes.
The temperature rose to. Then, after performing a heat cycle test for 1,000 cycles in the same manner as in Example 1, the heat dissipation substrate was cut into a 2 mm square and a shear strength test was performed. The average shear strength was 4.8 kgf. .

Comparative Example 2 A length of 64 mm and a width of 6 produced in the same manner as in Example 1.
A 4 mm thick 0.6 mm thick aluminum nitride green sheet was punched to form a 250 μm square via hole 20,7.
Twenty were formed. After that, degreasing under the same conditions as in Example 1
Fired, 54m long with 200μm square via holes
An aluminum nitride substrate with m, a width of 54 mm and a thickness of 0.3 mm was obtained. The thermal conductivity of the substrate was 193 W / mK.

After polishing and sputtering this aluminum nitride substrate in the same manner as in Example 1, a conductive paste was embedded in the via hole and baked at 900 ° C. Then, the vapor deposition and cutting steps are performed in the same manner as in Example 1, and the length is 12 mm,
A heat dissipation substrate having a width of 2.0 mm was obtained. There are 259 tungsten via holes in this heat dissipation substrate, and the area ratio of the conductive material is 43.2%. Moreover, when the resistance was measured in the same manner as in Example 1, the average was 0.1 mΩ.
Met. Further, a dummy element made of GaAs was bonded in the same manner as in Example 1, and after bonding to the heat sink, 40A was energized for 5 minutes.
The temperature rose to 29 ° C. Then, after performing a heat cycle test for 1,000 cycles in the same manner as in Example 1, the heat dissipation substrate was cut into 2 mm square and a shear strength test was performed. The average shear strength was 1.3 kgf. .

Comparative Example 3 A length of 64 mm and a width of 6 produced in the same manner as in Example 1.
A 4 mm thick 0.6 mm thick aluminum nitride green sheet was punched to form three 1.25 mm diameter via holes.
Twenty were formed. After that, degreasing under the same conditions as in Example 1
Fired, 54 mm long with via holes 1 mm in diameter,
An aluminum nitride substrate having a width of 54 mm and a thickness of 0.3 mm was obtained. The thermal conductivity of the substrate was 200 W / mK.
The aluminum nitride substrate was polished and sputtered in Example 1.
Then, the conductive paste was embedded in the via hole and baked at 900 ° C. Then, vapor deposition and cutting steps were performed in the same manner as in Example 1 to obtain a heat dissipation substrate having a length of 12 mm and a width of 2.0 mm. There are four via holes in this heat dissipation substrate, and the conductive material area occupancy rate is 13.1%. When the resistance was measured in the same manner as in Example 1, the average was 0.20 mΩ. Furthermore, Example 1
Bond a dummy element made of GaAs in the same manner as above, and then bond 40A to the dummy element after bonding to the heat sink.
When electricity was applied for 5 minutes, the temperature rose to 33 ° C. Then, the heat cycle test was conducted in the same manner as in Example 1,
After conducting 00 cycles, the heat-dissipating substrate was cut into 2 mm square and a shear strength test was conducted. As a result, the average shear strength was 0.7 kgf.

[0035]

The heat dissipating substrate of the present invention has a structure in which a metal via hole is provided immediately below the element on which the element is mounted, but a semiconductor element such as a high-power semiconductor laser element is mounted and used. In this case, the heat generated in the via hole is small even when a large current is passed, and not only does it have excellent heat dissipation characteristics, but it does not deteriorate or break the bondability between the semiconductor element and the substrate even after repeated use. Shows high stability and durability.

[Brief description of drawings]

FIG. 1 is a top view (A) and a sectional view (B) of a typical heat dissipation board of the present invention.

[Explanation of symbols]

1 Heat dissipation board 2 Placement surface 3 Ceramic substrate 4 Via holes filled with conductive material 5 Parts where semiconductor elements are placed 6 Conductive layer 7 Solder layer s Area of exposed surface of conductive material filled in via hole

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H01L 23/373 H01L 23/14 C H01S 5/022 M

Claims (3)

[Claims] 1. A ceramic substrate having a mounting surface for mounting a semiconductor element, wherein the mounting surface penetrates between both surfaces of the substrate, and a via hole filled with a conductive substance therein. In a heat dissipative substrate including a ceramic substrate as a constituent member, the total area of the exposed end faces of the conductive material in the portion of the mounting surface on which the semiconductor element is mounted is 5 to 40%. Pore size 0.05 to 0.5
A heat-radiating substrate having a plurality of mm via holes arranged therein. 2. The heat-radiating substrate according to claim 1, wherein the ceramic substrate is made of aluminum nitride, silicon carbide, beryllium oxide, or a ceramic containing any one of these as a main component. 3. The electrical resistance value at 25 ° C. between both conductive layers is 1 mΩ or less when a conductive layer is formed on the mounting surface of the ceramic substrate and the entire back surface thereof, and the ceramic substrate at 25 ° C. Thermal conductivity is 170
It is W or more, The heat dissipation board | substrate of Claim 1 or 2 characterized by the above-mentioned.