JP2001288526A - Heat radiating material and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high thermal conductivity and low thermal expansion heat radiating material composed of a heat radiating material low in thermal expansion and having high thermal conductivity in particular a material composed of an easily and efficiently producible Al-Si series material, and also provide its production method. SOLUTION: An Al-Si alloy containing, by weight, 13 to 80% Si is rapidly cooled at a rate of 300 to 800 K/sec and is molded by a diecasting method, by which the high thermal conduction and low thermal expansion heat radiating material in which the crystal grain size of an Si phase is <=50 μm, the thermal expansion coefficient is <=16×10-6/K, and the thermal conductivity is >=100/m.K can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat radiation material for substrates used in various applications such as communication, automobile, and semiconductor devices, and particularly to a portion to be bonded to a semiconductor or ceramic material such as a Si chip. The present invention relates to a heat dissipating material having low thermal expansion and high thermal conductivity, that is, good heat matching and good heat dissipating properties, and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the recent development of the information and communication industry, devices such as LSIs using semiconductor substrates have been developed, and today, the speed and density have been increased. Communication devices using lasers and light have also been developed and used in many fields. In these devices and devices, measures to dissipate heat from semiconductors and semiconductor substrates to be used have become indispensable as capacity and speed have been increased.

[0003] Heat dissipation materials for semiconductor substrates have high thermal conductivity
(100 W / mK or more), as well as good compatibility with the semiconductor or ceramic used, that is, the coefficient of thermal expansion of the semiconductor or ceramic is about 3 to 8 × 10 ^-6 / K. It is necessary to have an expansion coefficient.

[0004]

The low thermal expansion and high thermal conductive materials include metal (composite) materials such as Cu-W, Mo, and Cu-Mo. However, all of them are difficult to form and process, and because of their high density, they are heavy and difficult to process.
There is another problem that the cost is high.

[0005] As a low thermal expansion metal material, Kovar (29N
i-8Co-Fe) and 42 alloys (42Ni-Fe). However, these alloys have a small thermal conductivity of 30 to 50 W / m · K. In addition, composite materials of these alloys and Cu have also been developed, but in reality, they are not yet widely used because of their complicated and expensive manufacturing methods.

[0006] Ceramic materials such as BeO, AlN and SiC are also known to have high thermal conductivity and low thermal expansion. BeO Be
The use of these ceramic materials is limited by the powder metallurgy method and requires sintering at high temperatures, which results in high cost and complicated shapes. Actually, it is not used for any purpose other than special use because of difficulty in molding.

On the other hand, pure Al has a high thermal conductivity (237 W / m
・ K) It is a metal that is used in various places such as radiation fins of semiconductor bases, buildings, automobile parts, etc. as a light and light (2.7g / cm ³ ) material with excellent workability. is there.

However, the coefficient of thermal expansion of Al is as large as 23 × 10 ⁻⁶ / K, and is high for semiconductor Si and ceramics materials (coefficient of thermal expansion of 3).
88 × 10 ⁻⁶ / K) or in the heat cycle of heat generation, the difference in thermal expansion between the two causes cracking.

[0009] In addition, Fe, Cu, Ni, Mg, Mn, S
There are materials to which elements such as n, Si, and Zn are added, and it is known that not only the material strength is increased but also the thermal expansion coefficient is slightly reduced ((16 × 10 ⁻⁶ / K). With the addition of elements other than Si, even a small amount of addition, the thermal conductivity sharply decreases.

[0010] In an Al-Si alloy in which Si is added to Al, the coefficient of thermal expansion decreases and the thermal conductivity decreases with an increase in the Si content. For example, the eutectic composition of Al-12Si is 180 W / mK, Expansion coefficient 17
It is known that there is no significant decrease of × 10 ⁻⁶ / K.

[0011] However, the material used for a portion having a junction with a semiconductor Si chip or ceramics needs to have a smaller thermal expansion coefficient (up to about 10 × 10 ^-6 / K) and a thermal conductivity Is also required (150 W / m · K or more).

In order to satisfy these physical properties, it is necessary to produce an Al-Si alloy having a Si content larger than the eutectic composition of Al-12Si. Therefore, JP-A-63-16458, JP-A-2-119249
No. proposes to obtain a material with low thermal expansion by sintering Al-Si gas atomized powder with a high Si content in Al-Si.

[0013] The Al-Si alloy having a high Si content is brittle because the crystal phase of Si is precipitated as shown in FIG. 1, and the thermal conductivity is reduced because the Si is cracked by stress or heat. It is known.

In JP-A-1-05055 and JP-A-9-55460, an Al-Si alloy having a Si content of 50 to 80% by weight is treated by a powder metallurgy method, and in particular, an Al-Si alloy is melted. Al- by gas atomizing method
We have proposed a method of producing Si powder and sintering it to produce Al-Si.

[0015] However, it is known that the process is complicated, which leads to an increase in cost, and that the thermal conductivity of these powder sintered materials is lowered due to impurities such as oxygen and carbon entering from the powder or the binder. ing.

[0016] The present invention is intended to provide a heat dissipating material having a low thermal expansion and a high thermal conductivity, which is used for a portion to be bonded to a semiconductor or ceramic material such as a Si chip, and particularly easily and efficiently manufactured. It is an object of the present invention to provide a heat dissipating material made of an Al-Si-based material and a manufacturing method thereof.

[0017]

Means for Solving the Problems The inventors studied a casting method as a method for producing an Al-Si-based material. As a result, FIG.
As shown in the figure, it was found that the coefficient of thermal expansion monotonously decreased with an increase in the Si content. This is the same as described in
The result was almost equivalent to the material disclosed in No. 460.

On the other hand, as shown in FIG. 3, the thermal conductivity rapidly decreases with increasing Si up to the eutectic of Al-12Si (180 W / m · K in the Al-12Si composition). Is 12 wt% or more, the decrease is gradual with respect to the content of Si, for example, Al-50Si
It was found that the composition was 150 W / m · K. This value was much higher than that of the Al-Si-based material prepared by the powder metallurgy method of JP-A-9-55460.

However, as described above, an Al-Si alloy containing 12% by weight or more of Si has a mixed structure of an Al-12Si eutectic alloy and two phases of Si, and is hard and brittle as the Si content increases.
Since the Si phase increases, not only is plastic working difficult,
Moldability also deteriorates. In addition, it was found that in normal casting, cracks occurred in the Si phase during cooling, which caused brittleness and cracks, and further reduced the thermal conductivity.

The present inventors studied a method of rapidly cooling Al-Si in order to improve the formability and workability of a composition containing a large amount of Si.
That is, the cooling rate in the normal casting method is 50-200K / s
ec, 300-800K / sec by die casting method
Quenching at a speed of 5 to increase the average crystal grain size of Si to 5 to 3
It has been found that a material having good moldability and a hard but improved toughness can be easily and stably obtained as a result.

Further, in order to obtain a material having a low thermal expansion, a composition containing a large amount of Si is necessary, but it has been considered that casting is difficult due to an increase in melting point. However, the inventors studied the configuration of the mold, and by rapidly cooling and molding a high melting point Al-Si material by a die casting method, a composition containing a large amount of Si can be sufficiently molded and has no crack. It was found that a molded article was obtained.

Further, the present inventors have found that, despite the high crystallinity, the Al-Si material obtained by the quenching die-casting method can obtain a material that is hard and not brittle regardless of the high Si content. Further, it was confirmed that a heat-dissipating material having irregularities and pins could be formed by using a die-casting die having a different shape, and the present invention was completed.

That is, the present invention relates to an Al-Si containing 13 wt% or more and 80 wt% or less, more preferably 30 wt% or more and 60 wt% or less.
The alloy is quenched and molded at a speed of 300 to 800 K / sec by die casting, the average crystal grain size of the Si phase is 50 μm or less, the thermal expansion coefficient is 16 × 10 ⁻⁶ / K or less, and the thermal conductivity is 100 /. A heat dissipation material characterized by obtaining a heat dissipation material having a characteristic of m · K or more and a method for producing the same.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an Al-Si alloy composition contains 13 wt% or more and 80 wt% or less of Si. 13wt% Si
If it is less than 1, the coefficient of thermal expansion is large, and it is difficult to obtain the effect of rapid cooling by the die casting method. If it exceeds 80% by weight, the Si phase occupies 70% or more of the volume, making molding difficult. More preferably, Si is in a range of 30 wt% or more and 60 wt% or less.

As impurities, 0.3 wt% or less of transition metal elements such as Fe, Cu, Cr and Mn; 0.5 wt% or less of alkali metal elements such as Na, Ca and Mg, and alkaline earth metal elements; Light elements such as P, B, etc. can tolerate 0.3 wt% or less. If any of the elements exceeds the above values, the thermal conductivity is undesirably reduced.

In the present invention, the average crystal grain size of the Si phase in the Al—Si alloy having the above composition is preferably 50 μm or less. It is characterized by obtaining a heat dissipation material. When the average crystal grain size of the Si phase exceeds 50 μm, cracks occur in the Si phase due to external stress or thermal stress, and the thermoelectric power decreases and the material becomes brittle.

[0027] In particular, as is apparent from the examples, even with the same composition material by the same casting method, due to the difference in cooling rate, FIG.
As shown in FIG. 4B, the structure has a completely different average crystal grain size of the Si phase. That is, the heat dissipation material according to the present invention has a thermal expansion coefficient of 16 × 10 ⁻⁶ / K or less and a thermal conductivity of 100 / by optimizing the above-described required composition and the average crystal grain size of the Si phase.
It is a material with high thermal conductivity and low thermal expansion having characteristics of mK or more and hard but improved in toughness.

The heat radiation material according to the present invention has a Vickers hardness average of 150 to 400, abrasion resistance of a friction speed of 5 m / sec, and a contact pressure of 0.2.
It has a characteristic of 2 mg / 1000 m or less at 5MP, and has excellent abrasion resistance, and is hard but not brittle, that is, excellent in toughness. However, tensile strength, tensile strength,
Elongation and the like decrease with an increase in the amount of Si.

The heat radiation material according to the present invention has a required composition of Al-Si
It is obtained by rapidly cooling and forming the alloy at a cooling rate of 300 to 800 K / sec by die casting. 300K cooling rate
If it is less than / sec, the average crystal grain size of the Si phase exceeds 50 μm, and the toughness decreases, which is not preferable. On the other hand, if it exceeds 800 K / sec, the average crystal grain size of the Si phase becomes too fine, so that the alloy melt is minutely aggregated and molding becomes difficult, which is not preferable.

The die casting method of the present invention can employ any known method or apparatus as long as the above-mentioned predetermined rapid cooling is possible. For example, the Al-Si alloy of the present invention is a high melting point material, and 300 to 800 K / sec from the high melting point temperature.
The amount of the cooling liquid supplied to the mold may be appropriately selected so that the cooling can be performed rapidly.

Preferred conditions for die casting are a molding temperature of + 50 ° C., a molding time of 3 to 5 seconds, a molding pressure of 10 to 20 MPa, and a cooling rate of about 500 K / sec.

[0032]

EXAMPLES Example 1 Al (equivalent to JIS P 1050) and Si (purity 3N) were blended in a weight ratio of 63:37, and were melted by high frequency melting in an Ar atmosphere. The dissolution temperature was 980 ° C. The melt was poured into a die casting mold, compression molded at 920 ° C. × 3 sec, 15 MPa, and quenched at 500 K / sec.

The obtained molded body had a thickness of 5 mm × 150 mm × 150 mm. Fig. 4A is a photograph of the cross-sectional structure of the die-cast material.
As shown in (magnification × 100), the average crystal grain size of Si was about 20 μm. The material has a coefficient of thermal expansion of 30.
× 10 ⁻⁶ / K, thermal conductivity at 150 ° C. was 150 W / m · K. The average Vickers hardness was 290, the tensile strength was 150 MPa, the elongation was 2.3%, the friction speed was 5 m / sec, and the amount of wear at a contact pressure of 0.5 MP was 1 mg / 1000 m.

As a comparison, the material which was rapidly cooled (cooling rate 50 K / sec) in a sand mold at the time of casting after melting of Al-37Si had an average crystal grain size of Si as shown in FIG.
It was 150 μm. The coefficient of thermal expansion of the comparative casting material is 30-100
The average was 13 × 10 ⁻⁶ / K at 150 ° C., and the thermal conductivity was 150 W / m · K at 30 ° C. The average Vickers hardness is 320 and the tensile strength is 75MP
a, elongation is 1.2%, wear amount under the same conditions as in Example 1 is 1.5 m
g / 1000m.

Example 2 Al (corresponding to JIS P 1050) and Si (purity: 3N) were blended at a weight ratio of 51:49, and were melted by high frequency melting in an Ar atmosphere. The dissolution temperature was 1100 ° C. The melt was poured into a die casting mold, compression-molded at 1000 ° C. × 3 sec, 20 MPa, and quenched at 600 K / sec.

[0036] The obtained molded body has a thickness of 20 mm x 40 mm x 60 mm and a thickness of 2 mm.
Lunch box type. The average crystal grain size of Si of the die-cast material was about 25 μm. The thermal expansion coefficient of the material is 10.2 × 10 ⁻⁶ / K on average at 30 to 100 ° C., and the thermal conductivity is 3
It was 147 W / mK at 0 ° C. Vickers hardness is average
390, tensile strength 70 MPa, elongation 0.9%, wear amount under the same conditions as in Example 1 was 0.3 mg / 1000 m.

[0037]

The heat dissipating material according to the present invention can be used as a heat dissipating material for substrates used in various applications such as communications, automobiles and semiconductor devices. It is a material that is effective in places where good compatibility and good heat conduction are required.

[0038] The high Si content Al-Si heat radiation material according to the present invention is:
In addition to low thermal expansion and high thermal conductivity, Al and Si have abundant resources, are environmentally friendly elements, and are light in weight.

Further, by designing the die in the die casting method, it is possible to form a complicated shape including a hole having a diameter of, for example, about 3 mm, and the molding speed is as fast as 20 to 60 seconds / shot. It is possible to stably mass-produce certain homogeneous heat radiation materials.

[Brief description of the drawings]

FIG. 1 is an Al-Si phase diagram.

FIG. 2 is a graph showing the relationship between the Si content of an Al—Si alloy and the average coefficient of thermal expansion.

FIG. 3 is a graph showing the relationship between the Si content and the thermal conductivity of an Al—Si alloy, where a solid line represents a material obtained by the die casting method of the present invention, and a broken line represents a material obtained by the powder metallurgy method.

FIG. 4 is a photograph of a cross-sectional structure of the material (magnification × 100), wherein A is a material obtained by the die casting method of the present invention, and B is a material obtained by sand casting.

[Procedure amendment]

[Submission date] December 27, 2000 (200.12.
27)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

4. The heat dissipation material according to claim 1, wherein the average crystal grain size of the Si phase in the Al—Si alloy is 50 μm or less.

5. The heat dissipating material according to claim 1, which has a thermal expansion coefficient of 16 × 10 ⁻⁶ / K or less and a thermal conductivity of 100 / m · K or more.

6. An Al-Si alloy containing 13% by weight or more and 80% by weight or less of Si is 300 to 80% by die casting.
A method for producing a heat dissipating material that is rapidly cooled and formed at a speed of 0 K / sec.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0023

[Correction method] Change

[Correction contents]

That is, according to the present invention, 13% by weight of Si is used.
The Al-Si alloy containing not less than 80 wt%, more preferably not less than 30 wt% and not more than 60 wt% is quenched and formed at a speed of 300 to 800 K / sec by die casting method,
Preferably, the amount of the transition metal element of the impurity is 0.3 wt% or less.
The average crystal grain size of the Si phase is 50 μm or less, the thermal expansion coefficient is 16 × 10 ⁻⁶ / K or less, and the thermal conductivity is 100 / m ·
A heat dissipation material characterized by obtaining a heat dissipation material having characteristics of K or more, and a method for manufacturing the same.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tsunekazu Saigo 2- 15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Sumitomo Special Metals Co., Ltd. Yamazaki Works F-term (reference) 5F036 AA01 BB01 BD03

Claims (5)

[Claims] 1. A heat-dissipating material which is an Al-Si alloy containing 13 wt% or more and 80 wt% or less of Si, and is formed by quenching by a die casting method. 2. The heat radiation material according to claim 1, wherein the Al-Si alloy contains Si in an amount of 30 wt% or more and 60 wt% or less. 3. The average crystal grain size of the Si phase in the Al-Si alloy is
2. The heat dissipation material according to claim 1, which has a thickness of 50 μm or less. 4. The heat dissipating material according to claim 1, which has a thermal expansion coefficient of 16 × 10 ⁻⁶ / K or less and a thermal conductivity of 100 / m · K or more. 5. A method for producing a heat-dissipating material, wherein an Al-Si alloy containing 13 wt% or more and 80 wt% or less of Si is rapidly cooled and formed at a rate of 300 to 800 K / sec by a die casting method.