JP2000294701A - Case for semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor for a case which can have a long-term reliability of a semiconductor element and can be manufactured inexpensively. SOLUTION: The case for a semiconductor includes a heat sink 104 having a semiconductor element 102 mounted thereon, a circular disk 105 for supporting the heat sink 104, and a cap 106 for covering the heat sink 104 and a mount part having the semiconductor element 102 mounted thereon to be joined to the disk 105 and to define a sealed space therein. In this case, the mount part, heat sink 104 and disk 105 are integrally compressed and molded with tungsten/ copper composite powder having a suitable weight ratio of tungsten and copper powder to form a molded body, and the compressed and molded body is sintered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor case for housing a semiconductor element used for optical transmission or the like.

[0002]

2. Description of the Related Art Compound semiconductor devices, such as laser diodes and light emitting diodes, which emit electromagnetic waves, such as GaAs, CaP, InAs, and CaBs, are sometimes deteriorated by heat generated by the generation of electromagnetic waves and lose long-term reliability. In order to prevent this deterioration and ensure long-term reliability, the semiconductor element is used by being housed in a semiconductor case. 6 and 7 show a conventional semiconductor case. The semiconductor case includes a submount 3 on which the semiconductor element 2 is mounted, a heat sink member 4 for supporting the submount 3, and a circular base 5 for supporting the heat sink member 4.
And a cap 6 that covers the heat sink member 4 supported by the circular substrate 5 and the submount 4 on which the semiconductor element 2 is mounted and that is joined to the circular substrate 5 by welding or the like to form a sealed space. The light extraction window 7 is mounted on the upper surface of the cap. The semiconductor case thus configured is used in a state where nitrogen gas or the like is sealed in the above-mentioned closed space and the semiconductor element is isolated from the outside air.
In the drawings, reference numerals 8 and 9 denote lead wires mounted on the circular base 5 via an insulating member 10, and reference numeral 11 denotes a lead wire for connecting one of the lead wires 8 to the semiconductor element 2.

It is desirable that the semiconductor case described above efficiently radiates heat generated from the semiconductor element 2 such as a laser diode or a light emitting diode. On the other hand, if there is a difference in the coefficient of thermal expansion between the semiconductor element 2 and the submount 3 on which the semiconductor element 2 is mounted, distortion occurs due to heat generation, and unnecessary stress is applied to the semiconductor element 2. Such stress accelerates performance deterioration of the semiconductor element 2 and further causes destruction. Accordingly, the material of the submount 2 is required to have a coefficient of thermal expansion close to the coefficient of thermal expansion of the semiconductor element, and the heat sink member 4 and the circular substrate 5 are required to have a material having a high thermal conductivity. In order to satisfy such a demand, in a conventional semiconductor case, the submount 3 is made of, for example, alumina or aluminum nitride having a coefficient of thermal expansion close to that of the semiconductor element 2, and the heat sink member 4 is made of copper or the like having good thermal conductivity. What is generally comprised from silver etc. and what comprised the circular base from the iron material which can be welded is used. However, in the case of the semiconductor described above, since the materials of the submount 3, the heat sink member 4, and the circular base 5 are different from each other, these must be brazed with a brazing material such as silver wax or Au-Su alloy. In addition, there is a problem that the productivity is low and the cost is high. In addition, it has been pointed out that the above-described semiconductor case has a problem that the thermal expansion coefficient and the thermal diffusion become unstable due to the brazing material, so that long-term reliability of the semiconductor element cannot be obtained.

[0004] In order to solve the above-mentioned problem, a composite material in which the submount, the heat sink member and the base are impregnated with copper by a molten metal infiltration method (infiltration method) in either tungsten or molybdenum or a tungsten-molybdenum alloy. For example, Japanese Patent Publication No. 24392/1990 and Japanese Patent Publication No. 2-343
No. 93 is disclosed. This composite material is formed by molding tungsten or molybdenum or a powder of tungsten and molybdenum into a plate, sintering it to form a network structure, and placing a high-purity copper plate on the network structure. By heating at a temperature of about 1200 ° C,
It is produced by melting copper and infiltrating the network structure.

[0005]

The composite material manufactured by the above-described infiltration method produces a copper tungsten block, and the copper tungsten block is cut by a cutting tool to form a circular base and a heat sink. Must be formed. However, since the above composite material has poor machinability, it requires considerable time for cutting,
Since the cutting tool must be changed frequently, there is a problem that productivity is low and cost is increased. In addition, since the size and density of the pores in the network structure obtained by sintering the tungsten powder are not uniform, the density of copper infiltrating into the pores becomes non-uniform, and the thermal conductivity and the coefficient of thermal expansion vary depending on the location. However, there is a problem that it is not stable and lacks reliability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a main technical problem thereof is to provide a semiconductor case which can provide long-term reliability of a semiconductor element and can be manufactured at low cost. .

[0007]

According to the present invention, there is provided, in accordance with the present invention, a heat sink for mounting a semiconductor element, a circular base for supporting the heat sink, the heat sink and the heat sink. A cap that covers the semiconductor element and is joined to the circular base to form a sealed space;
In the semiconductor case, the heat sink portion and the circular base portion are integrally compression-molded with a tungsten-copper composite powder in which a tungsten powder and a copper powder are combined at an appropriate weight ratio, and the compression-molded molding is performed. Is constituted by a sintered body obtained by sintering the body at a predetermined temperature,
A semiconductor case is provided.

It is desirable that the particle diameter of the tungsten powder and the copper powder be 7 μm or less. The compact is filled with a granulated powder obtained by granulating the tungsten-copper composite powder into a mold and compression-molded. The tungsten-copper composite powder is composed of a composite powder obtained by reducing a tungsten-copper composite oxide. Preferably, the tungsten-copper composite oxide is mixed with either ammonium paratungstate or ammonium metatungstate, "Copper tungstate / tungsten trioxide" formed by mixing copper, cupric oxide, or copper hydroxide at an appropriate weight ratio to form a mixed powder, and dehydrating the mixed powder. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a semiconductor case constructed according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of a semiconductor case constructed according to the present invention, and FIG. 2 is a sectional view taken along line AA in FIG. The semiconductor case in the illustrated embodiment includes a heat sink 104 having a mount 103 on which the semiconductor element 102 is mounted,
A circular base portion 105 supporting the heat sink portion 104 is integrally compression-molded with a tungsten-copper composite powder in which a tungsten powder and a copper powder are combined at an appropriate weight ratio,
It is constituted by a sintered body obtained by sintering the compression molded body at a predetermined temperature. Reference numeral 106 denotes a heat sink portion 104 and a mounting portion 1 of the heat sink portion 104.
03 with a cap that covers the semiconductor element 102 mounted on
A light extraction window 107 is provided on the upper surface. Nitrogen gas or the like is sealed in a closed space covered by the cap 106 and the circular base portion 105. 108 and 1 in the figure
Reference numeral 09 denotes a lead wire mounted on the circular base portion 105 via the insulating member 110, and reference numeral 111 denotes a lead wire connecting one of the lead wires 108 to the semiconductor element 102. Although the semiconductor element 102 is desirably mounted directly on the mount 103 of the heat sink 104 as in the illustrated embodiment, it is mounted on a sub-mount member made of alumina, aluminum nitride, or the like due to a problem in handling the semiconductor element. It may be mounted on the mounting part 103 of the heat sink part 104 in a sub-mounted state.

FIGS. 3 to 5 show a heat sink 104 having a mount 103 on which the semiconductor element 102 is mounted.
And a circular base 10 supporting the heat sink 104
It is a perspective view which shows the example which integrally molded 5 from the sintered compact.
FIG. 3 shows a circular base 10 having a lead wire hole 105a.
5 and a heat sink 104 provided with a mount 103 are integrally formed. FIG. 4 shows a circular base portion 105 having a lead hole 105 a and a mounting portion 103.
And a concave portion 105b for irregularly reflecting and extinguishing unnecessary laser light emitted from the rear portion of the semiconductor laser directly below the mount portion 103 in the circular base portion 105. It was formed. FIG.
In this embodiment, a circular base portion 105 provided with a and a heat sink portion 104 provided with a projecting mount portion 103 are integrally formed.

Next, the sintered body forming the heat sink portion 104 having the mount portion 103 and the circular base portion 105 will be described. It is important to use a tungsten-copper composite oxide in order to form a dense sintered body of the tungsten-copper composite powder having uniform thermal conductivity and no voids. The tungsten-copper composite oxide is produced from a predetermined amount of tungsten oxide and a predetermined amount of copper oxide. For example, the production methods disclosed in JP-A-8-239219 and JP-A-8-333119 Can be used. As the tungsten oxide, ammonium paratungstate (APT) (10NH4 5O.12WO3 .5H)
2 O) or ammonium metatungstate (AM
T) (6NH4 3O.12WO3.XH2O)
(Here, X 0.75 to 1.25) is preferable,
As the copper oxide, cuprous oxide, cupric oxide or copper hydroxide is preferable. Then, either ammonium paratungstate (APT) or ammonium metatungstate (AMT) and any of cuprous oxide, cupric oxide, or copper hydroxide are mixed at an appropriate weight ratio to form a mixed powder. Then, it is preferable to use "cupric tungstate (CuWO4) / tungsten trioxide (WO3)" which is a tungsten-copper composite oxide formed by dehydrating the mixed powder. A method for manufacturing a sintered body for forming the heat sink portion 104 and the circular base portion 105 using the tungsten-copper composite oxide (CuWO4 / WO3) will be described.

First, a tungsten-copper composite oxide (CuWO4 / WO3) produced from a predetermined amount of tungsten oxide and a predetermined amount of copper oxide is reduced in a hydrogen atmosphere to obtain tungsten-copper (W / Cu). Make composite powder. In this tungsten-copper (W / Cu) composite powder, cupric tungstate (CuWO4) is mixed in a state where copper and tungsten are uniformly dispersed at an atomic level, so that a tungsten-copper composite oxide is used. (CuW
In a state where O 4 / WO 3) is reduced, copper and tungsten are uniformly dispersed and mixed with each other. That is, at the time of reduction, copper is first reduced, and then this copper acts as a core to reduce tungsten therearound, so that a composite powder uniformly dispersed in each other is obtained. Even if the tungsten (W) powder and the copper (Cu) powder are mixed, it is not possible to produce a uniformly dispersed composite powder.

A wax is added to the tungsten-copper (W / Cu) composite powder produced as described above, and the mixture is granulated by, for example, a spray drier method. The reason why the tungsten-copper (W / Cu) composite powder is granulated is to improve the fluidity of the composite powder. That is, the fluidity of the powder changes remarkably at a particle size of 44 μm. Particle size 4
Powder having a size of 4 μm or less has poor fluidity under the influence of intermolecular force, gravity, static electricity, humidity and the like. Tungsten-copper (W / Cu) obtained by reducing tungsten-copper composite oxide
The composite powder has a very low fluidity because of its fine particle size of generally 30 μm or less. For this reason, it is difficult to industrially mold. Therefore, tungsten-copper (W / Cu)
Granulate the composite powder, for example, 60 mesh (250 μm)
To produce a granulated powder sieved with a sieve.

As described above, 60 mesh (250 μm)
m), the mold is filled with the granulated powder of tungsten-copper (W / Cu) sieved, and is pressed into a predetermined shape with a forming pressure of about 3.5 t / cm2. By using the granulated powder sieved with 60 mesh (250 μm) in this way, so-called bridging of the powders at the time of molding is prevented with good fluidity, and the molding is performed with a molding pressure of about 3.5 t / cm 2. Therefore, it is possible to obtain a dense and uniform molded article without defects.

Next, a compact made of the granulated powder of tungsten-copper (W / Cu) formed as described above is sintered in hydrogen. At this time, in order to uniformly perform sintering, the compact may be embedded in high-purity alumina particles and sintered. In addition, at the time of sintering, preferably 60 to 1
The temperature is raised at a rate of 20 ° C / hr, and 1150 to 1350 °
Sinter at the sintering temperature of C. In order to obtain a dense tungsten-copper (W / Cu) sintered body in which no pores remain, bonding (sintering) of tungsten particles is caused at a temperature before a liquid phase of copper is generated, and a liquid of copper is formed. It is necessary to completely attract the liquid phase without any gap due to the generation of the phase. For this purpose, it is necessary to reduce the particle size so that the sintering of the tungsten (W) particles proceeds at a low temperature (the sinterability is proportional to the cube of the particle size), and a uniform composition is obtained. To copper (C
The u) powder must also have a similar particle size to the tungsten (W) powder. However, in the present embodiment, the tungsten / copper (W / Cu) composite powder has a tungsten and copper particle size of 7 μm or less, preferably 3 μm or less.
m or less, and since tungsten is uniformly dispersed around copper, a dense tungsten / copper (W / Cu) sintered body that does not leave voids during sintering can be obtained.

The coefficient of thermal expansion and the coefficient of thermal conductivity of the sintered body manufactured as described above are determined by using a tungsten oxide (ammonium paratungsten (APT), ammonium metatungsten) when manufacturing a tungsten-copper composite oxide. (AMT) or the like and copper oxide (cuprous oxide, cupric oxide, copper hydroxide, etc.) can be mixed to change the weight ratio of tungsten to copper. The thermal expansion coefficient and the thermal conductivity of the tungsten-copper (W / Cu) composite powder according to the weight ratio of tungsten to copper are as shown in Table 1. Table 1 shows the thermal expansion coefficients of various semiconductors and the thermal expansion coefficients and thermal conductivity of aluminum oxide (Al2O3) and an iron-nickel-cobalt alloy (Kovar).

[0018]

[Table 1]

[0019]

EXAMPLES Tungsten-copper composite oxide (CuWO4 / WO3) manufactured by OSRAM Sylvania, Inc. (Massachusetts, USA).
(TYPE 3) was reduced in a hydrogen atmosphere, and the average particle size of 90% tungsten (W) -10% copper (Cu) was 2
2.5% of wax (Carbowax-8000) was added to a 0 μm tungsten (W) -copper (Cu) composite powder, and the mixture was granulated by a spray drier method. Then, the granulated powder sieved with a sieve of 60 mesh (250 μm) is filled in a mold for integrally molding the heat sink part 104 having the mount part 103 and the circular base part 105, and is 3.5 t / cm.
Pressing was performed at a molding pressure of 2 to obtain a molded body. The circular base portion 105 of the molded body has a diameter of 10 mm and a thickness of 2 mm.
mm, and the heat sink portion 104 was 3 mm long × 3 mm wide × 3 mm thick. Next, in a hydrogen stream at 120 ° C./h
The temperature was raised at a rate of r, and the sintering was performed at 1350 ° C. for 4 hours. As a result, a defect-free sintered body having a density of 17.0 g / cm3 was obtained. The parallelism and flatness of this sintered body were 3/100 or less. When the thermal characteristics of the sintered body were measured, the thermal conductivity was 188 W / mK.
And the coefficient of thermal expansion is 5.8 × 10 −6 / ° C. [20 to 100
° C]. By using this sintered body, the coefficient of thermal expansion of the InAs semiconductor device (5.8 × 10 −6 /
° C), and a semiconductor case suitable for mounting an InAs semiconductor element could be obtained.

[0020]

Since the semiconductor case according to the present invention is constituted as described above, the following operation and effect can be obtained.

That is, according to the present invention, the heat sink portion and the circular base portion constituting the semiconductor case are integrally compression-molded with a tungsten-copper composite powder in which a tungsten powder and a copper powder are compounded at an appropriate weight ratio. Since the molded body is constituted by a sintered body sintered at a predetermined temperature, processing after sintering is not necessary or can be used with a small amount of processing. Obtainable.

Further, according to the present invention, since the particle diameter of the tungsten powder and the copper powder is 7 μm or less, and the composite powder in which copper and tungsten are uniformly dispersed, the skeleton structure of the tungsten after sintering is obtained. Is densely formed, and the dense skeletal structure is filled with copper without gaps to form a high-density tungsten / copper sintered body without generating voids, so that the thermal conductivity and the coefficient of thermal expansion are uniform. Thus, a highly reliable semiconductor case with good dimensional accuracy and stable quality can be obtained.

Furthermore, according to the present invention, since the compact is filled with a granulated powder obtained by granulating the tungsten-copper composite powder into a mold and compression-molded, the mass productivity is good, and the granules of the tungsten powder and the copper powder are obtained. Even if the diameter is small, the fluidity is good and so-called bridging between powders is prevented at the time of molding, so that a dense and uniform molded article without defects can be obtained.

Further, according to the present invention, the tungsten-copper composite oxide is reduced to form a tungsten-copper composite powder, which is different from the tungsten-copper powder obtained by mixing the tungsten powder and the copper powder. A dense powder in which copper and tungsten are tightly and uniformly dispersed at the atomic level to form a high-density sintered body with good sinterability and a high-quality semiconductor case with excellent dimensional accuracy. be able to. In addition, by changing the mixing ratio of ammonium paratungstate or ammonium metatungstate and cuprous oxide, cupric oxide or copper hydroxide, the weight ratio of tungsten to copper is appropriately adjusted to achieve the compound semiconductor element. Since a tungsten-copper sintered body having a coefficient of thermal expansion matching the coefficient of thermal expansion can be formed, the compound semiconductor element and the mount are well-adapted, and the compound semiconductor element is damaged by thermal strain. Does not occur. In addition, the tungsten-copper sintered body according to the present invention has a thermal conductivity of 10 times or more as compared with alumina and kovar having a thermal expansion coefficient close to that of the compound semiconductor element, and thus exhibits a sufficient cooling effect. As a result, long-term reliability of the compound semiconductor element can be ensured.

[Brief description of the drawings]

FIG. 1 is a plan view of a semiconductor case configured according to the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a perspective view showing an embodiment in which a heat sink portion provided with a mount portion and a circular base portion constituting a semiconductor case according to the present invention are integrally formed of a sintered body.

FIG. 4 is a perspective view showing another embodiment in which a heat sink portion provided with a mount portion and a circular base portion constituting a semiconductor case according to the present invention are integrally formed of a sintered body.

FIG. 5 is a perspective view showing still another embodiment in which a heat sink section provided with a mount section and a circular base section constituting a semiconductor case according to the present invention are integrally formed of a sintered body.

FIG. 6 is a plan view of a conventionally used semiconductor case.

FIG. 7 is a sectional view taken along line BB in FIG. 6;

[Explanation of symbols]

 102: Semiconductor element 104: Heat sink 105: Circular base 106: Cap 107: Light extraction window 108, 109: Lead wire 110: Insulating member 111: Lead wire

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Teruaki Maehata 3-25-21 Higashishinagawa, Shinagawa-ku, Tokyo Stock inside Technisco Corporation (72) Inventor Takuma Kishida 3-25-21 Higashishinagawa, Shinagawa-ku, Tokyo Stock Technisco Co., Ltd. (72) Inventor Satoshi Senoo 3-25-21 Higashishinagawa, Shinagawa-ku, Tokyo F-term (reference) 5F036 AA01 BB01 BD01

Claims (5)

[Claims] A heat sink for mounting a semiconductor element, a circular base for supporting the heat sink, a cap for covering the heat sink and the semiconductor element and joining to the circular base to form a sealed space; Wherein the heat sink portion and the circular base portion are integrally compression-molded with a tungsten-copper composite powder in which a tungsten powder and a copper powder are combined at an appropriate weight ratio, and the compression-molded molding is performed. A case for a semiconductor, comprising a sintered body obtained by sintering a body at a predetermined temperature. 2. The semiconductor case according to claim 1, wherein said tungsten powder has a particle size of 7 μm or less, and said copper powder has a particle size of 7 μm or less. 3. The semiconductor case according to claim 1, wherein the molded body is filled with a granulated powder obtained by granulating the tungsten-copper composite powder into a mold and compression-molded. 4. The semiconductor case according to claim 1, wherein said tungsten-copper composite powder comprises a composite powder obtained by reducing a tungsten-copper composite oxide. 5. The tungsten-copper composite oxide is prepared by mixing any one of ammonium paratungstate or ammonium metatungstate with any one of cuprous oxide, cupric oxide or copper hydroxide in an appropriate weight ratio. 5. The semiconductor case according to claim 4, wherein the mixed powder is “cupric tungstate / tungsten trioxide” formed by dehydrating the mixed powder.