JP2000311980A - Lead frame and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low thermal expansion, high thermal conductivity lead frame excellent in deformation, and a semiconductor device employing it, by dispersing a specified ratio of compound particles as a mass of intricate shape where a plurality of particles are coupled. SOLUTION: Electrolytic Cu powder and Cu2O powder are employed as material powder, mixed at a specified ratio, injected into a die and cold pressed to produce a preliminary molding which is then sintered in an argon atmosphere. Cu2O aggregates in mixing process and swells in sintering process but the grain size is 50 μm or less and a fine texture is provided where Cu phase and Cu2O phase are dispersed uniformly. 95% or more of Cu2O particles, in cross-sectional area rate, are dispersed as a mass of irregular shape where a plurality of particles are coupled. Consequently, excellent workability is provided and the shape can be imparted easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel lead frame and a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, lead frame materials are roughly classified into iron-based alloys and copper-based alloys. From the viewpoint of thermal expansion characteristics, iron-based alloys (42 alloy, Kovar) have a low coefficient of thermal expansion and are excellent in compatibility with silicon and ceramics, while copper-based alloys have a large coefficient of thermal expansion, and Is characterized by having excellent consistency.

[0003] Representative iron-based alloys are ASTME15 and F30.
Are all austenitic (face-centered cubic) alloys.

[0004] The iron-nickel-cobalt alloy of F15 is commonly called kovar, and has been used as a lead frame material because it is the material having the best matching of thermal expansion characteristics with silicon. After that, as the price of cobalt soared, the mainstream of leadframe materials was 42% of iron and nickel.
Although Kovar has been changed to an alloy, Kovar is still used in some ceramic packages even now because of its good matching of thermal expansion characteristics with ceramics.

On the other hand, integrated circuits (ICs) in which electronic circuits are integrated on a single semiconductor chip are classified into memories, logics, microprocessors, and the like according to their functions.
Here, the power semiconductor element is called an electronic semiconductor element. The degree of integration and the operation speed of these semiconductor elements have been increasing year by year, and accordingly, the amount of heat generated has also increased. by the way,
In general, an electronic semiconductor element is housed in a package for the purpose of shutting it off from the outside air and preventing failure and deterioration.
Many of these are a ceramic package in which a semiconductor element is die-bonded to ceramics and sealed, and a plastic package in which the semiconductor element is sealed with resin.
Further, in order to cope with high reliability and high speed, a multi-chip module (MCM) in which a plurality of semiconductor devices are mounted on one substrate is also manufactured.

The plastic package has a structure in which a lead frame and terminals of a semiconductor element are connected by a bonding wire, and this is sealed with a resin. In recent years, with an increase in the amount of heat generated by a semiconductor element, a package in which a lead frame has heat dissipation properties and a package in which a heat dissipation plate for heat dissipation is mounted have appeared. For heat dissipation, a copper-based lead frame or a heat radiating plate having a large thermal conductivity is often used, but there is a concern about a problem due to a difference in thermal expansion from Si.

On the other hand, the ceramic package has a structure in which a semiconductor element is mounted on a ceramic substrate on which wiring is printed, and is sealed with a metal or ceramic cap. Furthermore, Cu-Mo or Cu
-W composite material or Kovar alloy is joined,
Although it is used as a heat radiating plate, each material is required to have low thermal expansion or high thermal conductivity as well as improved workability and low cost.

The MCM has a structure in which a plurality of semiconductor elements are mounted on a thin film wiring formed on a substrate made of Si, metal, or ceramics by a bare chip, placed in a ceramics package, and sealed with a lid. When heat dissipation is required, a heat sink or a heat dissipation fin is installed on the package. Copper or aluminum is used as a metal substrate material, which has the advantage of high thermal conductivity, but has a large coefficient of thermal expansion and poor compatibility with semiconductor elements. For this reason, Si or aluminum nitride (AlN) is used for the substrate of the highly reliable MCM. Further, since the heat radiating plate is bonded to the ceramic package, a material having good compatibility with the package material in terms of the coefficient of thermal expansion and having a large thermal conductivity is desired.

[0009]

As described above, any semiconductor device having a semiconductor element mounted thereon generates heat during its operation, and if stored, the function of the semiconductor element may be impaired. Therefore, a heat radiating plate having excellent thermal conductivity for dissipating generated heat to the outside is required. The heat sink is
Since the semiconductor element is bonded directly or via an insulating layer, the semiconductor element is required to have not only thermal conductivity but also thermal expansion.

Currently used semiconductor elements are mainly S
i and GaAs. These thermal expansion coefficients, respectively ^{2.6 × 10 -6 ~3.6 × 10 -6} /℃,5.7×10 -6
6.9 × 10 ⁻⁶ / ° C. Heat sink materials having a thermal expansion coefficient close to these include AlN, SiC, Mo,
Although W, Cu-W, etc. are known, since these are single materials, it is difficult to arbitrarily control the heat transfer coefficient and the thermal conductivity, and the workability is poor and the cost is high. There is. JP-A-8-78578 discloses C
A u-Mo sintered alloy is disclosed in Japanese Unexamined Patent Publication No. 9-181220.
W-Ni sintered alloy is disclosed in Japanese Unexamined Patent Publication No. 9-209058.
SiC sintered alloys are disclosed in Japanese Unexamined Patent Publication No. 9-15773.
C has been proposed. These conventionally known composite materials can control the heat transfer coefficient and the thermal conductivity over a wide range by changing the ratio of both components, but have low plastic workability, it is difficult to manufacture a thin plate, and the number of production steps is large. It becomes.

An object of the present invention is to provide a lead frame having low thermal expansion, high thermal conductivity, and excellent plastic workability, and a semiconductor device using the same.

[0012]

According to the present invention, there is provided a lead frame having a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the compound particles have a cross-sectional area ratio of the whole of the particles. 95% or more are characterized in that a plurality of particles are dispersed as a complex-shaped mass in which they are connected to each other.

The present invention provides a lead frame having a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the number of the compound particles alone is 100 per 100 μm square in cross section. In the following, the remaining compound particles are characterized in that a plurality of particles are dispersed in the form of a complex-shaped mass connected to each other.

According to the present invention, there is provided a lead frame including a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the compound particles have a Vickers hardness of 300 or less.

The present invention relates to a lead frame comprising a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the lead frame has a thermal conductivity at 20 ° C. of 20 to 1 per 1 W / m · K.
The rate of increase of the average coefficient of thermal expansion at 50 ° C. is 0.025 to 0.0.
35 ppm / ° C.

The present invention is a lead frame comprising a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the compound particles are composed of a plurality of particles connected to each other and dispersed as a lump, The lump extends in a direction extended by plastic working.

According to the present invention, there is provided a lead frame comprising copper and at least one particle of copper oxide, aluminum oxide and silicon oxide.

According to the present invention, there is provided a lead frame having copper and copper oxide particles, wherein the copper oxide particles have a complex shape in which a plurality of particles are connected to each other by 95% or more of the total area of the particles in cross-sectional area ratio. It is characterized by being dispersed as a lump.

According to the present invention, there is provided a heat sink for a semiconductor device, characterized in that a Ni plating layer is provided on the surface of the lead frame described above.

The present invention comprises a semiconductor element, a lead frame on which the element is mounted, and a metal wire for electrically connecting the lead frame and the semiconductor element, wherein the semiconductor element is sealed with a resin composition. In the semiconductor device described above, the lead frame includes the lead frame described above.

According to the present invention, the semiconductor device described above is sealed with a composition containing epoxy resin, spherical quartz powder and a silicone polymer or containing no silicone polymer. Or in a non-surface-mount type resin-sealed semiconductor device. The spherical quartz powder accounts for 70% by weight or more, more preferably 80 to 95% by weight of the whole composition. In particular, according to the present invention, as a logic or memory semiconductor device, 82 to 90% by weight of quartz
And 90% or more of quartz powder is made of fused spherical quartz powder, and non-spherical (square) quartz powder is used for 3 to 10%. The present invention also provides a logic or memory semiconductor device having a surface-mount type QFP, a non-surface-mount type DILP for a logic having a thickness of 1.5 mm or more, and a SOJ or TSOP surface-mount type for a memory. A filler, preferably quartz powder, is sealed with a epoxy resin composition having 75 to 81% and silicon with respect to the surface mount type DILP. It is preferable to use 60 to 80% of the filler having a particle size of 5 μm to 100 μm in which fused spherical quartz powder is used, and to use the residual quartz powder having a particle size of less than 5 μm, preferably 3 μm or less (pulverized quartz powder). The spherical quartz powder is preferably 65 to 75%.

As the resin-sealed semiconductor device according to the present invention,
It is also used for structures such as SOP, PLCC and MSP.

That is, the lead frame according to the present invention uses Au, Ag, Cu, Al having high electric conductivity as a metal, and Cu is most excellent in that it has a high melting point and a high strength. Also, as described above, the inorganic compound is not a compound such as conventional SiC or Al ₂ O ₃ having extremely different hardness with respect to the base metal, but is relatively soft particles, and is stable after sintering. The average coefficient of thermal expansion in the range is preferably 5.0 × 10 ⁻⁶ / ° C. or less, more preferably 3.5 × 1
Those having a Vickers hardness of 300 or less at 0 ^-6 / ° C or less are preferable. By using soft inorganic compound particles in this way, high plastic workability by hot and cold after sintering can be obtained. A thin plate can be obtained. And since the composite material has the inorganic particles dispersed therein, high strength can be obtained. Copper oxide, tin oxide, lead oxide, nickel oxide and the like can be considered as the inorganic compound particles. However, soft copper oxide having the smallest thermal expansion coefficient is particularly preferable.

Further, the lead frame of the present invention is made of SiC,
It is preferable to include 5% by volume or less of fine ceramic particles having a Vickers hardness of 1000 or more and a hard average particle size of 3 μm or less, such as Al ₂ O ₃ , for further strengthening.

After melting or sintering, the lead frame of the present invention can be formed into a desired thickness by rolling or the like, and can be formed into a final shape by plastic working and cutting by pressing.

In particular, the lead frame according to the present invention is made of a copper (Cu) alloy containing 20 to 80% by volume of cuprous oxide (Cu ₂ O), in which the Cu ₂ O phase and the Cu phase are dispersed. It is preferable that the material has a texture, a coefficient of thermal expansion from room temperature to 300 ° C. of 5 × 10 ^{−6 to} 14 × 10 ⁻⁶ / ° C., and a thermal conductivity of 30 to 325 W / m · K.

The copper-copper oxide lead frame has the following features:
First copper oxide (Cu ₂ O) containing 20 to 80 vol%, the balance with the copper (Cu), have a tissue in which the Cu ₂ O phase and Cu phase is oriented, the thermal expansion coefficient at 300 ° C. from room temperature 5x
10 ^{−6 to} 14 × 10 ⁻⁶ / ° C. and a heat conductivity of 30
325 W / m · K, and the thermal conductivity in the orientation direction is preferably at least twice the direction perpendicular to the orientation direction.

The lead frame according to the present invention is obtained by a melting method or a powder metallurgy method.

The powder metallurgy method is as follows.

Press molding a mixed powder containing copper oxide (Cu ₂ O) as an example of inorganic compound particles and copper (Cu) powder as an example of metal;
It is characterized by including a step of sintering at 0 ° C. and a step of performing plastic working in a cold or hot state.

Further, the method of manufacturing a copper lead frame according to the present invention is characterized in that a mixed powder containing 10.8 to 48.8% by volume of copper dioxide (CuO) and the balance consisting of copper (Cu) and unavoidable impurities is used. Press forming process, 800 ° C.-1050
℃ of CuO reacted with Cu with molded solidified Cu ₂ O
It is preferable to include a sintering step of transforming into a sphere, a step of performing plastic working by cold or hot pressing, and a subsequent annealing step.

The lead frame according to the present invention has a capacity of 17.6.
Cu with a coefficient of thermal expansion of × 10 ^-6 / ° C, a high thermal conductivity of 391 W / m · K, and a thermal conductivity of 12 W / m · K and a low coefficient of thermal expansion of 2.7 × 10 ^-6 / ° C It is a material in which Cu ₂ O is compounded and has a sintered body composition of Cu-20.
８０80% by volume of Cu ₂ O, and the coefficient of thermal expansion from room temperature to 300 ° C. is 5 × 10 ^{−6 to} 14 × 10
⁻⁶ / ° C. and a thermal conductivity of 30 to 325 W / m · K
Can be provided. When the content of Cu ₂ O is 20% or more, the thermal expansion coefficient required for the heat sink can be obtained, and 80% by volume.
This is because sufficient thermal conductivity and strength as a structure can be obtained below.

In the present invention, Cu powder and Cu ₂ O powder or CuO powder are mixed at a predetermined ratio as raw material powder,
After being cold-pressed in a mold, it is sintered. And
Plastic working is performed cold or hot as needed.

The mixing of the raw material powder is performed by a V mixer, a pot mill, a mechanical alloying, or the like.
Since the particle size of the raw material powder affects the press formability and the dispersibility of Cu ₂ O after sintering, the particle size of Cu powder is 100 μm or less, and the particle size of Cu ₂ O and CuO powder is 10 μm or less, particularly 1-2 μm. Is preferred.

Next, a mixed powder is used in a mold, and
Cold press molding at a pressure of 2,000 kg / cm ²
It is desirable to increase the pressure as the ₂ O content increases.

The preform of the mixed powder is sintered under normal pressure, HIP or hot pressing in an argon gas atmosphere, preferably at 800 ° C. to 1050 ° C. for about 3 hours, and contains Cu ₂ O. The temperature increases as the volume increases. Although the sintering temperature varies depending on the base metal, in particular, at 800 ° C. or lower, a sintered body with a high density cannot be obtained. At 1050 ° C. or higher, there is a risk of partial melting due to the eutectic reaction between Cu and Cu ₂ O. For this reason, it is not preferable, and 900 ° C. to 1000 ° C. is preferable.

According to the present invention, since the constituent Cu and Cu ₂ O have low hardness and high ductility, cold or hot working such as rolling and forging can be performed. You. By imparting the processing, the material exhibits heat conduction anisotropy, but it is effective for applications requiring strength improvement and heat transfer in a certain direction.

In the present invention, CuO is used as a raw material powder, mixed with Cu powder and press-molded.
By internally oxidizing u, a sintered body having a structure in which a Cu phase and a Cu ₂ O phase are dispersed can be finally obtained. That is, when CuO coexists with Cu, it utilizes the fact that it is more thermally stable to transform to Cu ₂ O at high temperature according to the equation (1).

2Cu + CuO → Cu + Cu ₂ O (1) A predetermined time is required for the equation (1) to reach equilibrium. For example, when the sintering temperature is 900 ° C., about 3 hours is sufficient. .

The particle size of Cu ₂ O in the sintered body is preferably fine because it affects density, strength or plastic workability. However, the particle size is strongly affected by the method of mixing the powders, and the larger the mixing energy, the less the agglomeration between the powders, and a fine Cu ₂ O phase is obtained after sintering.

In the present invention, in a V mixer having a low mixing energy, the Cu ₂ O phase has a particle size of 50 to 200 μm in 50% by volume or less of the Cu ₂ O phase and the remaining 50 μm or less,
50 μm or less in a pot mill containing steel balls,
For mechanical alloying having the largest mixing energy, the diameter is specified to be 10 μm or less. Particle size 200μm
Above, the porosity greatly increases, and plastic working becomes difficult. When the porosity is 50% by volume or more of the Cu ₂ O phase, the thermal conductivity decreases and the variation in characteristics increases, and the heat dissipation of the semiconductor device is caused. Unsuitable for board. More preferred tissue is 50 μm
This is a structure in which the following Cu ₂ O phase is uniformly dispersed with the Cu phase.
Although the particle size of Cu ₂ O is extremely irregular, since the particles before sintering are continuous, the particle size before sintering can be seen by looking at a higher magnification. The Cu ₂ O phase is preferably 10 μm or less.

According to the present invention, there is provided a composite material for a lead frame having a metal and preferably an inorganic compound having a smaller coefficient of thermal expansion than the metal, wherein the compound is formed in a dendrite shape.

The present invention is characterized in that the compound is formed in a dendrite shape and is divided into granules in the growth direction of the dendrite.

The present invention is characterized in that the compound is formed in a dendrite shape, and the growth direction of the dendrite is oriented in one direction.

The present invention is a composite material for a lead frame in which the above-mentioned metal and inorganic compound have unavoidable impurities with copper and copper oxide, and the copper oxide is formed in various shapes like dendrites. And

The present invention provides a composite material having a metal and an inorganic compound, wherein the inorganic compound is contained
90% or more of the cross-sectional area ratio is a rod having a diameter of 5 to 30 μm, and is characterized by being plastically processed.

According to the present invention, there is provided a composite material for a lead frame having copper, copper oxide and unavoidable impurities, wherein said copper oxide forms a dendrite at 10 to 55% by volume and has a linear expansion coefficient of 5 from room temperature to 300 ° C. × 10 ^{-6 to} 17 × 10 ^-6
It is characterized by having a thermal conductivity of 100 to 380 W / m · K at / ° C.

According to the present invention, the copper oxide is 10 to 55% by volume.
To form dendrites whose growth direction is oriented in one direction,
And a coefficient of linear expansion from room temperature to 300 ° C. is 5 × 10 ^{−6 to} 17
The thermal conductivity at × 10 ⁻⁶ / ° C. is 100 to 380 W / m · K, and the difference between the thermal conductivity in the orientation direction and the thermal conductivity in the direction perpendicular to the orientation direction is 5 to 100 W / m · K. There is a feature.

The present invention is characterized in that the eutectic copper oxide is dispersed in the copper in the above-mentioned composite material for lead frames having copper, copper oxide and unavoidable impurities.

The dissolution method is as follows.

The present invention resides in a method for producing and solidifying a metal and an inorganic compound which forms a eutectic structure with respect to the metal, and particularly to a method for producing a composite material for lead frames having copper and copper oxide. Casting after melting copper or copper and copper oxide in an atmosphere having an oxygen partial pressure of 10 ⁻² Pa to 10 ³ Pa; heat treatment at 800 ° C. to 1050 ° C .; plastic working in cold or hot Is applied.

Copper oxide used as a raw material is cuprous oxide (C
u ₂ O) or cupric dioxide (CuO).
The oxygen partial pressure during melting and casting is preferably 10 ⁻² Pa to 10 ³ Pa, and particularly preferably 10 ⁻¹ Pa to 10 ² Pa. Further, by changing the composition of the raw materials, the oxygen partial pressure, the cooling rate during solidification, and the like, the ratio of the Cu phase to the Cu ₂ O phase of the composite material,
The size and shape of the Cu ₂ O phase can be controlled. The ratio of the Cu ₂ O phase is preferably in the range of 10 to 55% by volume. Especially Cu ₂ O
When the phase content is 55% by volume or more, the thermal conductivity is reduced and the characteristics are varied, so that the phase becomes unsuitable for a heat sink of a semiconductor device. The shape of the Cu ₂ O phase is preferably a dendrite shape formed during solidification. This is because the dendrite tree is intricately intricate, and the expansion of the Cu phase having a large thermal expansion is pinned by the Cu ₂ O phase having a small thermal expansion. The dendrite dendrites formed during solidification can be controlled in the case of Cu phase, Cu ₂ O phase and CuO phase by changing the composition of the raw materials or the oxygen partial pressure. Also, due to the eutectic reaction, granular and fine Cu ₂
It is possible to improve the strength by dispersing the O 2 phase.
Further, after the casting, the size and shape of the Cu ₂ O phase can be controlled by performing a heat treatment at 800 ° C. to 1050 ° C. It is also possible to transform CuO formed at the time of solidification by the above-mentioned heat treatment into Cu ₂ O using an internal oxidation method. That is, when CuO coexists with Cu, it utilizes the fact that it is more thermally stable to transform to Cu ₂ O at a high temperature according to the above formula (1).

It takes a predetermined time for the equation (1) to reach equilibrium. For example, when the heat treatment temperature is 900 ° C., about 3 hours is sufficient. In addition, C
The size and shape of the fine Cu ₂ O phase generated by the eutectic reaction in the u phase can be controlled.

The melting method may be any method such as a unidirectional solidification method and a continuous thin plate casting method, in addition to ordinary casting. In ordinary casting, the composite material is isotropic because the dendrites are formed isotropically. In the unidirectional solidification method, the composite material can be provided with anisotropy by orienting the Cu phase and the Cu ₂ O phase in one direction. Further, in the continuous casting method of a thin plate, the dendrite becomes fine because the solidification rate is high, and the dendrite is oriented in the thickness direction, so that anisotropy can be imparted to the thin plate composite material, and the production cost can be reduced.

Further, in the composite material according to the present invention, the constituent Cu phase and Cu ₂ O phase have low hardness and high ductility.
Cold or hot working such as rolling or forging is possible, and is performed as necessary after casting or heat treatment. By giving the processing, the anisotropy is expressed in the composite material, and the strength can be improved. In particular, by cold or hot working, the Cu ₂ O phase is oriented in a certain direction, and anisotropy appears in the composite material. At this time, the difference between the thermal conductivity in the orientation direction and the thermal conductivity in the direction perpendicular to the orientation direction is 5 to 100 W / m · K.

Example 1 As raw material powder, electrolytic Cu powder having a particle size of 75 μm or less and Cu ₂ O having a purity of 3N and a particle size of 1 to ₂ μm were used.
Powder was used. After mixing 1400 g of Cu powder and Cu ₂ O powder at the ratio shown in Table 1, they were mixed in a dry pot mill containing steel balls for 10 hours or more. The mixed powder was poured into a mold having a diameter of 150 mm and cold-pressed at a pressure of 400 to 1000 kg / cm ² depending on the content of Cu ₂ O to obtain a preform having a diameter of 150 mm and a height of 17 to 19 mm. Thereafter, the preform was sintered in an argon gas atmosphere and subjected to chemical analysis, structure observation, measurement of thermal expansion coefficient, thermal conductivity, and measurement of Vickers hardness. The sintering temperature was varied between 900 ° C. and 1000 ° C. in accordance with the content of Cu ₂ O, and kept at each temperature for 3 hours. Thermal expansion coefficient from room temperature to 300 ℃
The thermal conductivity was measured using a TMA (Thermal Mechanical Analysis) device in the temperature range described above, and the thermal conductivity was measured by a laser flash method. The results are shown in Table 1.

As a result of chemical analysis, the composition of the sintered body was consistent with the composition. Table 1 shows the thermal expansion coefficient and thermal conductivity.
As is clear, by adjusting the composition ratio of Cu and Cu ₂ O, the composition changed over a wide range, and it was found that the thermal characteristics required for the lead frame could be controlled.

[0058]

[Table 1]

On the other hand, as a result of observing the microstructure at a magnification of 300 times, Cu ₂ O agglomerates in the mixing step and grows enlarged in the sintering step, but the particle size is 50 μm or less.
The phase and the Cu ₂ O phase had a dense structure in which the phases were uniformly dispersed.

It is also clear that 99% or more of the Cu ₂ O particles are dispersed in the form of irregularly shaped masses in which a plurality of particles are continuous in terms of the area ratio of the cross section.

As a result of the hardness measurement, the Cu phase was Hv 75 to 8
0, Cu ₂ O had a hardness of Hv 210 to 230. In addition, as a result of evaluating the machinability by lathe and drill processing,
It was found that the workability was very good, and that the shape was easily imparted.

(Example 2) Cu-55% by volume was obtained under the same conditions as in Example 1 except that the mixing of the powder was performed with a V mixer.
A Cu ₂ O sintered body was prepared, and the structure was observed and the same as in Example 1.
The thermal expansion coefficient and the thermal conductivity were measured.

Cu-55 volume% Cu ₂ O sintered body 300
The double microstructure is a structure in which Cu ₂ O having a large difference in size is mixed. The large-sized Cu ₂ O particles were generated by aggregation of the Cu ₂ O particles during mixing by the V mixer. The values of the coefficient of thermal expansion and thermal conductivity are C
Although no clear difference was observed with a sintered body of the same composition in which u and Cu ₂ O were uniformly dispersed, a tendency that the variation depending on the measurement location tended to be slightly increased was observed. As described above, it can be seen that most of the Cu ₂ O particles have an irregular shape in which a plurality of particles are connected and are dispersed in a larger lump than the above.

Example 3 As raw material powder, electrolytic Cu powder having a particle size of 74 μm or less and CuO powder having a purity of 3N and a particle size of 1 to 2 μm were used, and the composition ratio of the Cu powder and the CuO powder was Cu-22.4% by volume CuO. And 300 g in a 120 mm diameter planetary ball mill container containing 8 mm diameter steel balls.
Time mechanical alloying. Thereafter, the mixed powder was poured into a mold having a diameter of 80 mm, and was cold-pressed at a pressure of 1000 kg / cm ² to obtain a preform. Thereafter, the preform was sintered at 800 ° C. for 2 hours in an argon gas atmosphere, and subjected to structure observation, measurement of thermal expansion coefficient and thermal conductivity, and oxide X-ray diffraction in the same manner as in Example 1.

As a result of observing the microstructure of 1000 times,
Cu ₂ O is finer than that of Example 1 or 2,
Cu ₂ O having a particle size of 10 μm or less is uniformly dispersed. Refinement of the structure is suitable for improving strength and improving cold rolling properties. In addition, 95% or more of the Cu ₂ O particles form clumps having an irregular shape in the same manner as described above.
It was found that there were around 0 spherical particles.

[0066] The sintered body, the result of the identification of the oxide by X-ray diffraction, the detected diffraction peaks are only Cu ₂ O, that CuO has completely transformed to Cu ₂ O during sintering confirmed. As a result of the chemical analysis, the composition of the sintered body was Cu-40% by volume Cu ₂ O as set.

On the other hand, the thermal expansion coefficient and the thermal conductivity were equivalent to those of the same composition of Example 5 described later.

Example 4 Using the same raw material powder as in Example 1, Cu powder and Cu ₂ O powder were mixed with Cu-55% by volume Cu ₂
After mixing 550 g with a composition ratio of O 2, the mixture was mixed in a V mixer. The mixed powder is poured into a mold having a diameter of 80 mm, and
It was cold pressed at a pressure of kg / cm ² to obtain a preform having a diameter of 80 mm × 22 mm. Thereafter, the preformed body was sintered at 975 ° C. for 3 hours in an argon gas atmosphere. Then
The obtained sintered body was heated to 800 ° C., forged to a forging ratio of 1.8 with a 200-ton press, and then softened and annealed at 500 ° C.
In the same manner as in Example 1, the structure was observed and the heat transfer coefficient and the thermal conductivity were measured.

In the forged material, some edge cracks were observed on the side surface, but the other parts were sound. It was found that the copper composite material of the present invention was excellent in plastic workability.

In the microstructure 300 times larger than the plane parallel to the forging direction of the forged material, the Cu phase and Cu ₂ O phase are deformed and oriented in the forging direction, but defects such as cracks are recognized. Absent. In addition, it can be seen that the Cu ₂ O particles become a mass in which 95% or more are continuous, and are extended in the direction extended by the plastic working.

Table 2 shows the measurement results of the thermal conductivity by the laser flash method. In the as-sintered state without forging, no anisotropy of the thermal conductivity is observed. However, anisotropy is generated by forging, and the thermal conductivity in the L direction parallel to the orientation direction (forging direction) of the Cu phase and Cu ₂ O phase is in the C direction (forging direction) perpendicular to the direction. The value is twice or more. In addition, as a result of measuring the coefficient of thermal expansion from room temperature to 300 ° C., almost no anisotropy was observed.
Of the same composition.

[0072]

[Table 2]

(Example 5) Electrolytic Cu powder having a particle size of 74 µm or less and CuO powder having a purity of 3N and a particle size of 1 to 2 µm were used as raw material powders. After mixing 1400 g of Cu powder and CuO powder at the ratio shown in Table 3, they were mixed in a dry pot mill containing steel balls for 10 hours or more. The mixed powder is poured into a mold having a diameter of 150 mm,
A preform was obtained by cold pressing at a pressure of 10001000 kg / cm ² . After sintering the preform in an argon gas atmosphere, it was subjected to oxide X-ray diffraction, microstructure observation, and measurement of thermal expansion coefficient and thermal conductivity. The sintering temperature was changed between 900 ° C. and 1000 ° C. in accordance with the CuO content,
Hold for hours. The coefficient of thermal expansion was measured in a temperature range from room temperature to 300 ° C. using a TMA (Thermal Mechanical Analysis) device, and the thermal conductivity was measured by a laser flash method. The results are shown in Table 3.

[0074]

[Table 3]

[0075] The sintered body, the result of the identification of the oxide by X-ray diffraction, diffraction peaks of the detected cuprates are only Cu ₂ O, transformation from CuO during sintering to Cu ₂ O Was confirmed to have been completed.

[0076] In the 300 times microstructure of the obtained sample No.14, which exhibits the same tissue of the same composition of Example 1, Cu ₂ O phase is Cu ₂ produced by the oxidation reaction of Cu and CuO It consists of Cu ₂ O generated by decomposition of O 2 and CuO. Cu ₂ O particles are the same as in Example 1.

On the other hand, as is apparent from Table 3, the coefficient of thermal expansion is not significantly different from that of Example 1 in which Cu ₂ O powder is used as the raw material, but the thermal conductivity is CuO as the raw material. Is better when the content of CuO, that is, the content of Cu ₂ O is 50% by volume.
Above, there is a tendency to increase. This is because the density of the sintered body is higher when CuO is used as the raw powder.
FIG. 1 shows the thermal conductivity (x) and coefficient of thermal expansion shown in Tables 1 and 3.
It is a diagram showing the relationship with (y). In the present embodiment, these relationships are equal to or greater than the value determined by y = 0.31x + 4.65 and equal to or less than the value determined by y = 0.031x + 5.95. Therefore, the slope is 0.02 as an average coefficient of thermal expansion at 20 to 250 ° C. per 1 W / m · K of thermal conductivity at 20 ° C.
It is preferable to set the concentration to 5 to 0.035 ppm / ° C.

(Embodiment 6)

[0079]

[Table 4]

The linear expansion coefficient, thermal conductivity, and hardness of a composite material obtained by dissolving a raw material prepared by mixing copper and Cu ₂ O powder having a purity of 2N at a ratio shown in Table 4 and then casting the material in the air were measured. The coefficient of thermal expansion was measured in a temperature range from room temperature to 300 ° C. using a push bar type measuring device with a standard sample being SiO ₂ . The thermal conductivity was measured by a laser flash method. The results are shown in Table 1. Further, in the microstructure of the obtained sample No. 3, the copper oxide was formed in a dendrite shape, and further, a granular material having a particle size of 10 to 50 μm,
A μm mass was observed.

As is clear from Table 4, the thermal expansion coefficient and the thermal conductivity vary over a wide range by adjusting the composition ratio of Cu and Cu ₂ O. I found that I could control it.

On the other hand, as is clear from the microstructure, C
u ₂ O formed a dendrite and had a dense structure in which the Cu phase and the Cu ₂ O phase were uniformly dispersed.

As a result of the hardness measurement, the Cu phase was Hv 75 to 8
0, Cu ₂ O had a hardness of Hv 210 to 230. In addition, as a result of evaluating the machinability by lathe and drill processing,
It was found that the workability was very good, and that the shape was easily imparted.

(Embodiment 7)

[0085]

[Table 5]

Using a unidirectional solidification method, copper and C
Raw materials prepared by mixing the u ₂ O powders at the ratios shown in Table 5 were melted under various oxygen partial pressures and then cast to produce composite materials. Sample N cast after melting in an atmosphere with an oxygen partial pressure of 10 ^-2 Pa
In the microstructure of O.7, the Cu ₂ O phase formed dendrites, and the granules having a particle size of 5 to 50 μm continued linearly and were oriented in various directions.

The microstructure of Sample No. 8, which was cast after melting in an atmosphere having an oxygen partial pressure of 10 ³ Pa, was Cu ₂ O
The phase formed dendrites and had a structure oriented in one direction, and it was found that the shape and density of the Cu ₂ O phase could be controlled by changing the raw material and the oxygen partial pressure. Granular and rod-shaped particles having a particle size of 5 to 30 μm are formed at about half the height.

Table 5 shows the measurement results of the linear expansion coefficient and the thermal conductivity of the above two types of composite materials for lead frames. As a result, in each of the composite materials, anisotropy was recognized in the linear expansion coefficient and the thermal conductivity.

The same result as in the case of using oxygen as the atmosphere gas was obtained by bubbling oxygen gas into the raw material melt.

(Embodiment 8)

[0091]

[Table 6]

The above sample No. 8 was heated at 900 ° C. for 90 hours.
%, The workability was sound and the composite material of the present invention was found to be excellent in plastic workability. In the microstructure of Sample No. 9 shown in Table 6, the orientation was remarkable as compared with the as-cast sample, and Cu
_{The 2} O phase was elongated in the plastic working direction and elongated in one direction to form a rod, and had a structure having an aspect ratio in the range of 1 to 20. The rod diameter is 20 μm or less, and most is 1 to 10 μm. As shown in Table 6, the sample No.
A more remarkable anisotropy was recognized in the coefficient of thermal expansion and the thermal conductivity of No. 9.

(Example 9) After performing plastic working using the sintered material and the cast material obtained in Examples 1 to 8, a tape for a lead frame was manufactured by cold rolling to a desired thickness. Further, by pressing, FIG.
A lead frame for mounting a plurality of semiconductor elements shown in FIG.

FIG. 2 shows the shape of a lead frame according to an embodiment of the present invention. In this embodiment, the lead frame 1 is made of a composite material of Cu and Cu ₂ O. Cu
Since the composite material of Cu and Cu ₂ O has excellent workability, a lead frame having such a shape can be formed by a thin plate punching method. This surface was plated with Ni.

As a lead frame shape of another embodiment of the present invention, the chip mounting portion 2 of the lead frame 1 has a higher Cu ₂ O content than other portions of the lead frame 1. For this reason, the difference in thermal expansion coefficient from the semiconductor chip is reduced, and thermal fatigue and thermal stress can be further reduced. In addition, since the content of Cu ₂ O in the other portion is low or substantially made of Cu, the conductivity is high, which is effective for reducing the on-resistance of the power transistor and increasing the capacity of an IC or the like.

(Embodiment 10) FIG. 3 shows that an LSI silicon element 20 is mounted on the lead frame obtained in Embodiment 9,
It is a perspective view of the surface mounting type resin-sealed semiconductor device resin-sealed with epoxy resin. The epoxy resin 19 uses a resin having a filler described below. 15 is an Au wire, 16 is its die bonding, 17 is an outer lead, and 18 is a support bar.

The various fillers and epoxy resin compositions shown in Table 7 were kneaded with a biaxial roll heated to 80 ° C. for 10 minutes.

The composition using the obtained spherical filler has an extremely low melt viscosity and a large fluidity even though the gelation time is almost the same as that of the composition using the square filler.
Further, a composition containing a filler having a smaller gradient n represented by an RRS particle size diagram has a lower melt viscosity and a higher fluidity. When the n value is 0.6 or less, the melt viscosity (1
80 ° C.) is undesirably increased.

[0099]

[Table 7]

Further, a spherical filler (sphere-1) is used as the filler.
Was used to prepare 70, 75, 80 and 85% by weight of a resin composition, respectively.

Transfer molding was performed using these resin compositions, post-curing was performed at 180 ° C. for 6 hours, and the linear expansion coefficient, flexural modulus and thermal stress at room temperature were measured.

Further, the semiconductor element having the zigzag wiring of aluminum formed on the surface is transfer-pressed and sealed at −55 ° C./30 minutes⇔ + 150 ° C./30/2000.
A cycle thermal cycle test was conducted to evaluate the crack resistance of the sealing resin layer, the lead / gold wire bonding, and the connection reliability of the aluminum wiring (if the resistance value changed by 50% or more was judged to be defective). Table 8 shows the results.

From Table 8, it is found that the composition containing a silicone polymer and containing 80% by weight or more of filler has a linear expansion coefficient of 1.3 × 10
^-5 / ° C or less and little increase in elastic modulus. Therefore, it can be seen that the thermal stress generated in the insert is also small.

The resin-encapsulated semiconductor device using the resin composition as in this example is extremely excellent in crack resistance and wiring connection reliability even when subjected to a thermal shock such as a thermal cycle test. .

In the present example, a spherical quartz powder having a particle diameter of 100 μm or less was used as 95% of the filler in the resin composition containing no siloxane, and the remainder was a square quartz powder having a particle diameter of 10 μm or less. It was 85% by weight. In addition, spherical quartz powder having a particle size of 100 μm or less was used as 70% of the filler in the resin composition containing siloxane, and the remainder was made up of square quartz powder having a particle size of 5 μm or less, and the total was 80.5% by weight.

[0106]

[Table 8]

The RRS particle size diagram is a particle size diagram showing a particle size distribution according to the Rosin-Rammler equation (distributed by the Japan Powder Industry Association: Powder Engineering Handbook, pp. 51-53). R (Dp) = 100exp (-b · Dp n) ... (1) [where, R (Dp): cumulative weight percent of the maximum particle size to the particle size Dp, Dp: particle size, b and n: constants] RRS The gradient in the particle size diagram is the value of n in the Rosin-Rammler equation where the cumulative weight% from the maximum particle size in the RRS particle size diagram is represented by a straight line connecting two points of 25% and 75%. Say

The particle size distribution when the filler ore is pulverized finely matches the Rosin-Rammler equation, and the RRS particle size diagram showing the particle size distribution based on this equation shows an almost straight line.

The present inventors measured the particle size distribution of various fillers. As a result, 90% by weight or more of all the fillers showed an RRS particle size diagram and showed almost linearity, unless special sieving was performed. It has been confirmed that the above formula is well matched.

The spherical fused silica powder used in the present invention is obtained by generating a fused silica powder, which has been previously ground to a predetermined particle size distribution, from a transporting apparatus using a combustible gas such as propane, butane, acetylene or hydrogen as a fuel. Spherical ones, which are fed into a high-temperature flame in a fixed amount and melted and then cooled, are most preferred. The above-mentioned fused quartz has a relatively small coefficient of linear expansion by itself and an extremely small amount of ionic impurities, and thus is suitable as a resin composition material for semiconductor element sealing.

90% by weight or more of the filler has a particle size of 0.5 to 1
It is preferably in the range of 00 μm. When the number of fine particles having a particle size of less than 0.5 μm increases, the thixotropic property of the resin composition increases, and the viscosity increases and the fluidity decreases. Also,
If the number of particles exceeding 100 μm increases, the Au wire of the semiconductor element may be deformed or cut during sealing, or coarse particles may cause clogging in the mold, and resin filling failure may easily occur. is there.

Next, the gradient n shown in the RRS particle size diagram is set to 0.
It is most preferred to be 6 to 0.95, and when n is larger than 0.95, the filler becomes bulky, the particle size of the resin composition increases and the fluidity decreases. Therefore, it is desirable that n is as small as possible, but in the present invention, it is desirable that 90% or more of the filler is in the particle size range of 0.5 to 100 μm. This is the smallest possible value.

The silicone polymer used in the present invention is a polydimethylsiloxane having a functional group such as an amino group, a carboxyl group, an epoxy group, a hydroxyl group or a pyrimidine group at a terminal or a side chain.

The epoxy resin which is solid at room temperature refers to a cresol novolak type epoxy resin, a phenol novolak type epoxy resin, a bisphenol A type epoxy resin or the like as a semiconductor encapsulating material. An acid anhydride such as pyromellitic anhydride or benzophenone anhydride is used, and a curing accelerator, a flexible agent, a coupling agent,
A coloring agent, a flame retardant, a release agent, and the like can be added as needed.

This epoxy resin composition was prepared by adding 70% to each material.
The mixture can be kneaded with a biaxial roll or an extruder heated to １００100 ° C. and molded by a transfer press at a mold temperature of 160 to 190 ° C., a molding pressure of 30 to 100 kg / cm ² , and a curing time of 1 to 3 minutes.

The linear expansion coefficient of the cured product is 1.3 × as described above.
By making it as low as 10 ^-5 / ° C or less, the elastic modulus can be made small. Therefore, the deformation and disconnection of the Au bonding wire of the semiconductor element at the time of sealing are small, and the thermal stress based on the difference in linear expansion coefficient is small, so that the temperature cycle resistance, heat resistance, moisture resistance and the like are good.

By melting and spheroidizing quartz powder as a filler, the bulk is reduced and the filler is easily filled. Further, at the time of sealing the semiconductor element, it is possible to prevent the corners of the filler from damaging the element and adversely affecting the element characteristics.
Furthermore, the elastic modulus can be reduced by blending the silicon polymer, and the thermal stress caused by the difference in linear expansion coefficient can be further reduced.

[0118]

According to the present invention, a lead frame having low thermal expansion, high thermal conductivity and high plastic workability, and a semiconductor device using the same can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a thermal expansion coefficient and a thermal conductivity.

FIG. 2 is a plan view of a lead frame.

FIG. 3 is a perspective view of a resin-sealed semiconductor device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lead frame, 2 ... Chip mounting part, 15 ... Au
Wire, 16: die bonding, 17: outer lead,
18 ... Support bar, 20 ... LSI silicon element.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiko Koike 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Junya Kanada 7-chome, Omikamachi, Hitachi City, Ibaraki Prefecture No. 1 F-term in Hitachi Research Laboratory, Hitachi, Ltd. (Reference) 5F067 EA00

Claims (13)

[Claims] 1. A composite material comprising a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, a plurality of the compound particles having a cross-sectional area ratio of 95% or more of the whole particles connected to each other. A lead frame characterized in that it is dispersed as a block having a complicated shape. 2. A composite material comprising a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the number of the compound particles alone is 100 or less in a 100 μm square section, A lead frame, wherein the remaining compound particles are dispersed in a complex-shaped mass in which a plurality of the compound particles are connected to each other. 3. A composite material comprising a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the compound particles have a Vickers hardness of 300 or less. 4. A composite material comprising a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, the average coefficient of thermal expansion at 20 to 150 ° C. per 1 w / m · K of thermal conductivity at 20 ° C. The lead frame has a rate of increase of 0.025 to 0.035 ppm / ° C. 5. A composite material comprising a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the compound particles are connected to each other and dispersed as a lump, and the lump is stretched by plastic working. A lead frame extending in a direction. 6. A lead frame comprising copper and at least one particle of copper oxide, aluminum oxide and silicon oxide. 7. Copper oxide particles comprising copper and copper oxide particles, wherein 95% or more of the copper oxide particles are dispersed as a complex mass in which a plurality of particles are connected to each other. And lead frame. 8. A lead frame comprising a metal and an inorganic compound, wherein the inorganic compound is rod-shaped and is plastically processed. 9. A lead frame according to claim 1, further comprising a Ni plating layer on the surface. 10. A semiconductor device comprising: a semiconductor element; a lead frame on which the semiconductor element is mounted; and a metal wire for electrically connecting the lead frame and the semiconductor element, wherein the semiconductor element is sealed with a resin composition. 10. A semiconductor device according to claim 1, wherein said lead frame comprises the lead frame according to claim 1. 11. The semiconductor device according to claim 10, wherein said resin composition comprises an epoxy resin and an inorganic filler or a composition containing an epoxy resin, an inorganic filler and a silicon polymer. 12. The inorganic filler comprises spherical quartz powder,
12. The semiconductor device according to claim 11, wherein 90% by weight or more thereof has a particle size of 0.5 to 100 [mu] m. 13. The fused spherical quartz powder, wherein the spherical quartz powder is a fused spherical quartz powder obtained by melting quartz powder to form a sphere.
3. The semiconductor device according to 2.