JPH11157963A - Tabular composite and heat dissipating component using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for a heat dissipating component suitable for a semiconductor circuit board having high thermal conductivity, a low density, a thermal expansion coefficient close to that of a ceramic base plate and not causing warpage when heated, and therefore excellent in dimension stability. SOLUTION: This tabular composite is produced by impregnating a silicon carbide porous body with metals containing aluminum as a principal component. The difference in oxygen content between mutually confronting principal surfaces of the composite is in the range of <=0.5 wt.% and the composite preferably has the quantity of warpage in a heated state at 25-300 deg.C of <=5 μm/mm. This heat dissipating component is made of the tabular composite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high heat conductive composite material having excellent heat conduction characteristics and light weight, and suitable as a heat radiating component such as a heat sink of a semiconductor component such as a ceramic substrate or an IC package.

[0002]

2. Description of the Related Art Conventionally, circuit boards for mounting semiconductor elements using various substrates such as ceramic substrates and resin substrates have been known. In recent years, as circuit boards have been reduced in size and density, and semiconductor elements have been highly integrated, it has been desired to further improve the heat radiation characteristics of circuit boards.
Attention has been focused on ceramic substrates such as silicon carbide (SiC), aluminum nitride (AlN), and silicon nitride (Si ₃ N ₄ ) to which O) is added.

When a ceramic substrate is used as a circuit board, a package base, or the like, heat generated from the semiconductor element is radiated to the outside through a heat radiating component called a heat sink provided on the back surface of the circuit board or the like, and the operating characteristics of the semiconductor element are reduced. Etc. are secured.

In this case, copper (Cu) is used as a heat sink.
If a ceramic substrate and a heat sink are used, cracks may occur in the ceramic substrate due to the difference in the coefficient of thermal expansion between the ceramic substrate and the heat sink due to the heat bonding between the heat sink and the ceramic substrate, or the addition of a thermal cycle during the production or actual use of the ceramic circuit substrate. And cracks may occur. Therefore, when a ceramic substrate is used in a field where reliability is required, Mo, W having a small difference in thermal expansion coefficient from the ceramic substrate is used.
Was used as a heat sink.

A heat dissipating component using Mo or W is heavy due to heavy metals such as Mo and W, and is not preferable for applications in which it is desired to reduce the weight of the heat dissipating component. Further, since a heat sink using Mo or W is expensive, MMC (Metal Matrix C) in which copper, aluminum (Al), or an alloy thereof is reinforced with inorganic fibers or particles has recently been used.
Attention has been focused on a metal-ceramic composite (hereinafter, referred to as a composite), which is abbreviated as “composite”.

[0006] In general, the above-mentioned composite forms a preform by previously molding inorganic fibers or particles as a reinforcing material, and forms a base material (matrix) between fibers or particles of the preform. Alternatively, it is a composite impregnated (also called infiltration) with an alloy. Ceramics such as alumina, silicon carbide, aluminum nitride, silicon nitride, silica, and carbon are used as the reinforcing material.

However, in order to increase the thermal conductivity of the composite, it is necessary to select a material having a high thermal conductivity as a reinforcing material and a metal or an alloy. There are limitations that the wettability of the alloy and the reaction layer at the interface greatly contribute to the thermal conductivity, and that if the bonding between the matrix and the reinforcing material is insufficient, the strength of the composite is reduced in addition to the thermal conductivity.

[0008]

That is, when a heavy metal material such as Mo or W is used for the heat sink, the weight of the heat dissipating component becomes heavy, and the heat dissipating property is not always sufficient. With excellent heat dissipation
Even when u, Al, or the like is used as a heat sink, the difference in thermal expansion from the ceramic substrate is large, and in order to obtain a highly reliable structure, the bonding structure itself becomes very complicated, which increases the manufacturing cost and There is a problem that the thermal resistance as a heat dissipating component is increased.

Further, in order to solve the above-mentioned problems, a metal-
Although a ceramic composite is being studied, it is necessary to increase the ratio of ceramics, which is a reinforcing material having a low coefficient of thermal expansion, in order to obtain a coefficient of thermal expansion close to that of a ceramic substrate.
However, in order to increase the ratio of the ceramic component, it is necessary to mold the preform with a high molding pressure, which leads to an increase in cost and a problem that it is difficult to sufficiently impregnate the metal or alloy thereafter. For this reason, the development of a technology capable of providing a metal-ceramic composite having a high coefficient of thermal expansion close to that of a ceramic substrate and having a high thermal conductivity at low cost has been an issue.

On the other hand, when the above-described composite is used as a heat radiating component such as a heat sink, since the composite is used by bonding it to a circuit board or a radiating fin, the smoothness of the bonded portion, in other words, the warpage of the composite is very important. is there. For example, when applied to a heat sink, it is bonded to a circuit board such as a ceramic substrate by soldering or the like. Therefore, if the heat sink is warped, the thickness of the bonding interface becomes non-uniform. Occurs, and a non-uniform stress is generated on the circuit board, and a problem such as breakage of an insulating layer such as ceramics on the circuit board occurs. In addition, even if the material is small in warp at room temperature and can be bonded to a circuit board, if the material is heated during use and generates warp, peeling from the bonded portion or destruction of the circuit board is still required. There are problems such as.

Further, the ceramic circuit board or the like is usually used by being joined to a radiating fin or the like via a radiating component such as a heat sink. In this case, if the heat sink is warped, the joining with the radiating fin or the like becomes insufficient. In addition, heat generated from a semiconductor element or the like cannot be sufficiently dissipated, which causes a failure of components.

The present invention has been made in view of the above circumstances, and has high thermal conductivity, low specific gravity,
Also, to provide a highly thermally conductive composite having excellent thermal expansion coefficient, which is as small as a ceramic substrate, does not warp when heated, and has excellent dimensional stability, and a heat-dissipating component using the composite at a low cost. It is the purpose.

[0013]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that the strict control of the amount of oxygen in the complex can prevent the warpage of the complex. The present invention has been completed.

That is, the present invention relates to a plate-like composite obtained by impregnating a silicon carbide-based porous body with a metal containing aluminum as a main component, wherein the difference in oxygen content between the opposite main surfaces is 0.5% by weight. It is a plate-shaped composite characterized by the following.

Further, the present invention relates to a method for reducing the temperature from room temperature (25 ° C.) to 30 ° C.
The plate-shaped composite according to the above, wherein a warpage when heated to 0 ° C. is 5 μm or less with respect to a length of 1 mm in a direction in which the warp is maximum.

Further, the present invention provides a method for manufacturing a semiconductor device having a diameter of 3 mm and a length of 10 mm.
(A) and a test piece (B) having a diameter of 1.5 mm and a length of 10 mm were sampled so that the length direction was parallel to the main surface of the plate-like composite, and the thermal expansion coefficients of the test pieces were determined by a push-rod method. Wherein the difference between the apparent thermal expansion coefficients of the test piece (A) and the test piece (B) is 1 × 10 ⁻⁶ K ⁻¹ or less when measured with a thermal dilatometer. It is a plate-shaped composite.

In addition, the present invention is a heat dissipating component characterized by using the above-mentioned plate-shaped composite.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The coefficient of thermal expansion of a metal-ceramic composite is usually determined by the coefficients of thermal expansion of a ceramic serving as a reinforcing material and a metal serving as a base material, and their mixing ratio. The coefficient of thermal expansion of ceramics is considerably smaller than the coefficient of thermal expansion of metal, and it is effective to increase the ratio of ceramics to reduce the coefficient of thermal expansion of the composite. On the other hand, the thermal conductivity of a metal-ceramic composite is also basically determined by the thermal conductivity of the ceramic as the reinforcing material and the metal as the base material and their compounding ratio. The bonding state of the interface between the material and the substrate is also a major contributing factor. In general, metals have higher thermal conductivity among ceramics and metals, but silicon carbide (SiC), aluminum nitride (AlN), boron nitride (BN), and the like are equal to or more than metals (300 W / (m · K)).
It has the theoretical thermal conductivity described above and is very promising as a reinforcing material from the viewpoint of improving thermal conductivity.

As a result of various studies on the reinforcing material, the present inventors have found that when a silicon carbide-based porous body such as a molded body of silicon carbide powder or a ceramic structure containing silicon carbide as a main component is used, a high thermal conductivity is obtained. The present invention has been found to be suitable for producing a metal-ceramic composite having a low coefficient of thermal expansion, and has led to the present invention.

In producing a composite, it is important that the reinforcing material and the metal have good wettability, and a combination thereof is important in order to obtain a dense composite. In addition, a metal-ceramic composite is generally manufactured by a high-pressure casting method in which a preform formed by molding a ceramic as a reinforcing material into a predetermined shape is impregnated with a metal as a base material at a high temperature and a high pressure. If the melting point of the metal to be impregnated is high, the temperature at the time of impregnation becomes high, and the ceramic may be oxidized or the ceramic and the metal may react to form a compound which is not characteristically favorable. Furthermore, when the melting point of the metal as the base material is high, the impregnation temperature is high, so that the materials such as the mold material are limited and expensive, and the casting cost itself increases, and the obtained composite becomes expensive. Would.

As a result of various studies on the metal as the base material, the present inventors have found that a good composite can be manufactured by using an alloy containing aluminum as a main component. That is, the composite of the present invention is obtained by impregnating a silicon carbide-based porous body with a metal containing aluminum as a main component.

Further, the content of the silicon carbide based porous material in the composite of the present invention is preferably 50 to 80% by volume, more preferably 60 to 70% by volume. When the content of the silicon carbide-based porous body is less than 50% by volume, the thermal expansion coefficient of the composite becomes high, and the highly reliable heat radiation component aimed at by the present invention may not be obtained. Increasing the content of the silicon carbide-based porous body is effective in terms of high thermal conductivity and low coefficient of thermal expansion of the composite. However, in order to produce a porous body having a bulk density exceeding 80%, it is necessary to increase the content. There are problems such as the necessity of a very high molding pressure in the reforming process, and the cost of the resulting composite becomes extremely high. Further, the content of the silicon carbide based porous material in the composite is 80%.
If the content exceeds the volume% and becomes extremely high, there are problems that mechanical properties such as strength and fracture toughness are reduced and thermal conductivity at high temperatures is reduced.

On the other hand, the metal in the silicon carbide composite of the present invention is an alloy containing aluminum as a main component, and preferably contains 20% by weight or less of silicon or 5% by weight or less of magnesium. By adjusting the components other than aluminum in the alloy, the thermal conductivity and thermal expansion coefficient of the alloy itself can be changed, and the thermal expansion coefficient and thermal conductivity of the resulting composite can also be adjusted. By adding silicon or magnesium to aluminum to form an alloy, the melting point of the alloy is reduced and the viscosity of the molten metal is reduced at a high temperature, so that a dense composite can be easily obtained by a high-temperature casting method or the like. Furthermore, by alloying aluminum metal, the hardness of the metal itself is increased, and as a result, mechanical properties such as strength of the obtained composite are improved. Regarding metal components other than aluminum, silicon and magnesium in the alloy, copper and the like can be contained as long as the properties of the alloy do not change extremely.

The composite of the present invention is plate-shaped, and the difference between the amounts of oxygen on the opposite main surfaces is 0.5% by weight or less. The coefficient of thermal expansion of the composite is strongly governed by the coefficient of thermal expansion of the silicon carbide necessary for forming the silicon carbide-based porous body and the oxide used to bond it, and furthermore, the metal or alloy and their content. When the difference in the amount of oxygen exceeds 0.5% by weight, the present inventors have found that the difference in the coefficient of thermal expansion between the opposite main surfaces of the composite becomes large, the composite is warped, and the heat sink and the like are generated. When it is used as a heat radiating component, it has been found that it cannot be sufficiently bonded to a circuit board or a heat radiating fin,
This has led to the present invention. Also, as the thickness of the board,
For example, it is 2 to 10 mm when used for a heat sink.

The silicon carbide composite of the present invention can be used at room temperature (25
° C) to 300 ° C, the amount of warpage is 5 µm or less, and preferably 2 µm or less, with respect to 1 mm in the length in the direction in which the warp is maximum. In general, a heat radiating component such as a heat sink is used by being joined to a circuit board, a heat radiating fin, or the like. However, if warpage occurs at the time of heating, problems such as peeling of the circuit board and destruction of the insulating layer as described above occur.

If the amount of warpage when heated from room temperature (25 ° C.) to 300 ° C. exceeds 5 μm with respect to the length of 1 mm in the direction in which the warp becomes the maximum, it may be difficult to join the circuit board and the radiation fins. At room temperature, even if the bonding condition is uniform at room temperature,
Under actual use, when a heat cycle is added,
The semiconductor element may be damaged due to the destruction of the circuit board or the deterioration of the heat radiation characteristics.

The composite of the present invention has a diameter of 3 mm and a length of 3 mm.
10mm test piece (A) and 1.5mm diameter 10mm length
Each of the test pieces (B) was placed in the longitudinal direction of the plate-shaped composite.
Samples are taken in parallel with the surface, and the coefficient of thermal expansion of each is
When measured with a bar type thermal dilatometer, the test piece (A)
The difference between the apparent thermal expansion coefficients of the pieces (B) is 1 × 10 ^-6
K^-1Below, preferably 0.5 × 10^-6K^-1It is as follows.
The apparent thermal expansion coefficient difference is 1 × 10^-6K^-1A place to cross
If the composite is very warped,
May cause problems.

The composite of the present invention has a thermal conductivity of 150 W /
(M · K) or more and the coefficient of thermal expansion at room temperature is 1 × 10 ⁻⁵ K
It is preferably ^-1 or less.

The composite of the present invention has a density of 3 g / c.
m ³ degree and the metal lighter compared with such as copper, is used as a heat-dissipating component such as is effective in weight reduction of the parts. In addition, the silicon carbide composite of the present invention has a high flexural strength of 300 MPa or more, and has sufficient mechanical properties to be used as a heat dissipation component or the like.

The composite of the present invention is excellent in heat conduction characteristics, has sufficient mechanical characteristics, and has a coefficient of thermal expansion as small as a ceramic substrate. It is suitable for use as the first heat radiation component. The composite of the present invention has a density of 3 g / c.
It is as light as about m ³ and is suitable as a heat dissipating component for mobile equipment.

The composite of the present invention has excellent thermal conductivity and a low coefficient of thermal expansion of 1 × 10 ⁻⁵ K ⁻¹ or less. The thermal expansion difference between the ceramic substrate and the ceramic substrate is smaller than that of the ceramic substrate. It is suitable as a heat dissipating component for use in mobile devices such as electric vehicles and automobiles that require high performance. The heat radiating component using the composite of the present invention has a very small warpage even when there is a temperature change, so that it can be sufficiently bonded to a circuit board or a heat radiating fin, and has a high heat radiation characteristic stably. It has the effect of being able to.

The method for obtaining the complex of the present invention includes the following methods. A predetermined amount of silica sol, alumina sol, or the like is added to silicon carbide powder as a binder and mixed to form a desired shape. As a molding method, press molding, extrusion molding, cast molding, or the like can be used, and a binder for shape retention may be added as necessary. In addition, as for the silicon carbide powder, one kind of powder may be used, or a plurality of powders may be used by blending the particle size. Next, the obtained molded body is heated at a temperature of 700 to 160 in the atmosphere or in an atmosphere such as nitrogen.
Calcination is performed at 0 ° C. to produce a silicon carbide porous body. Alternatively, silicon carbide powder can be added to and mixed with silicon powder as a binder, and can be manufactured in the same manner. Further, with respect to another method for producing a silicon carbide-based porous body, it can be produced by firing silicon carbide powder or a mixed powder of silicon powder and carbon powder at a temperature of 1600 to 2200 ° C. in an inert gas atmosphere.

The obtained silicon carbide porous body is heated to prevent cracking due to thermal shock, and impregnated at a high pressure with a molten metal mainly composed of aluminum heated to a temperature not lower than the melting point. Make a complex. The method for impregnating the metal component is not particularly limited, and a high pressure casting method, a die casting method, or the like can be used.

The method for analyzing the amount of oxygen on the opposite main surface in the composite according to the present invention is as follows.
A portion of 1 to 0.5 mm is collected and pulverized in a mortar or the like to obtain a powdery sample, and an oxygen / nitrogen simultaneous analyzer (LECO;
TC-436).

[0035]

The present invention will be described in more detail with reference to the following examples.

[Examples 1 to 4] Silicon carbide powder a (manufactured by Taiheiyo Random Corporation: NG-220, average particle size: 60 μm) 7
5 g, silicon carbide powder b (manufactured by Yakushima Denko Corporation: GC-100
0F, average particle diameter: 10 μm) and 4.5 g of silica sol (Nissan Chemical Co., Ltd .: Snowtex) in a solid content amount, and after mixing for 30 minutes with a stirring mixer, 120 mm ×
It was pressed into a shape of 120 mm × 5 mm at a pressure of 10 MPa to obtain a molded body. The obtained molded body was heated at a temperature of 1000 ° C. for 2 hours in an air atmosphere to produce a silicon carbide porous body. The relative density of the obtained porous silicon carbide body was calculated from its size and mass, and as a result, it was 64%.

Next, the obtained silicon carbide-based porous body was preheated to a temperature of 800 ° C. in an electric furnace, and placed in a preheated press die having an inner diameter of 200 mmφ.
Of the alloy shown in Table 1 heated to
Pressing was performed at a pressure of MPa for 2 minutes to impregnate the silicon carbide porous body with the alloy. After cooling to room temperature, the silicon carbide composite was cut out with a diamond processing jig. The obtained silicon carbide composite was obtained using a diamond processing jig.
Specimen A for measuring thermal expansion coefficient (3 mmφ × 10 mm), specimen B (1.5 mmφ × 10 mm), specimen for measuring thermal conductivity at room temperature (10 mmφ × 3 mm), specimen for evaluating three-point bending strength ( 3 mm × 4 mm × 40 mm) and a test piece for warpage measurement (100 mm × 50 mm × 3 mm).
The specimen C (20 mmφ × 0.4 mm) was observed from the upper surface of the opposite main surface of the obtained composite, and the specimen D (2 mm) was observed from the lower surface.
0 mmφ × 0.4 mm) by grinding.

[0038]

[Table 1]

Next, the thermal expansion coefficient from room temperature to 250 ° C. using a thermal dilatometer (manufactured by Seiko Electronics: TMA-300) and the thermal conductivity at room temperature using a laser flash method (Vacuum Riko Co., Ltd.) (TC-7000) and a bending tester (Shimazu Seisakusho; Autograph) to measure the three-point bending strength. Table 2 shows the obtained results. Further, the test pieces C and D were pulverized in a mortar, and the oxygen content was measured with an oxygen / nitrogen simultaneous analyzer (LECO; TC-436). Further, with respect to the amount of warpage, the test piece was placed in an electric furnace, heated from a temperature of 25 ° C. to 300 ° C., and a dimensional change at that time was measured with a macrometer to calculate the amount of warpage. Table 2 shows the obtained results.

[0040]

[Table 2]

Example 5, Comparative Examples 1 and 2 75 g of silicon carbide powder a, 75 g of silicon carbide powder b, 6 g of silica sol in solid content and 50 g of pure water were mixed, mixed with a stirring mixer for 30 minutes, and then mixed with 120 mm × The mixture was poured into a gypsum mold having a shape of 120 mm × 5 mm and dried at a temperature of 40 ° C. for 24 hours to produce a molded body. In Comparative Example 1, the amount of pure water to be added was 100 g, and in Comparative Example 2, the mixing time was 30 seconds. The obtained molded body was heated at a temperature of 1000 ° C. in an air atmosphere.
For 2 hours to produce a silicon carbide-based porous body. The obtained silicon carbide porous body was added to a shape of 20 mmφ × 5 mm, and the relative density was calculated from the size and mass. The relative density of Example 5 was 69%, the relative density of Comparative Example 1 was 64%, and the relative density of Comparative Example 2 was 62%.

Next, this silicon carbide-based porous material was used in Example 1
An aluminum alloy was impregnated in the same manner as described above to produce a silicon carbide composite. The obtained composite was evaluated in the same manner as in Example 1. Table 3 shows the obtained results.

[0043]

[Table 3]

Example 6 The molded product of Example 5 was subjected to 1MP
In a nitrogen pressurized atmosphere of a, heating was performed at a temperature of 1500 ° C. for 3 hours to produce a silicon carbide-based porous body. The obtained silicon carbide-based porous body was impregnated with an aluminum alloy in the same manner as in Example 1 to produce a silicon carbide-based composite. The obtained composite was evaluated in the same manner as in Example 1. Table 4 shows the obtained results.

[0045]

[Table 4]

Examples 7 and 8 and Comparative Example 2 The silicon carbide composite produced in Example 5 was ground to 90 mm ×
90mm x 3mm, electroless nickel (Ni)
A plating process was performed to form a 10 μm-thick plating layer on the surface of the composite. A 50 μm-thick solder paste was screen-printed on the surface of the plated composite. In Example 7, a commercially available aluminum nitride substrate was mounted thereon, and in Example 8, a commercially available silicon nitride substrate was mounted. 300
Heat treatment was performed for 5 minutes in a reflow furnace at ℃ to bond the ceramic substrates. Note that Comparative Example 2 was performed using the copper plate in Example 7
After the plating treatment, the aluminum nitride substrate was joined in the same manner as described above.

Next, using a composite obtained by bonding these ceramic substrates, a temperature range of -40 ° C. to 150 ° C. is used.
00 heat cycle tests were performed. In Examples 8 and 9, even after the heat cycle test, abnormalities such as generation of cracks between circuits on the ceramic substrate and peeling of circuits were not observed. On the other hand, in Comparative Example 2, cracks occurred between the circuits on the ceramic substrate after 30 heat cycles.

[0048]

According to the composite of the present invention, the content and distribution of the silicon carbide porous body as a reinforcing material are adjusted, and as a result, the thermal conductivity is high and the thermal expansion coefficient is almost the same as that of the ceramic substrate. It is suitable for heat radiating components such as a heat sink which is used in connection with a ceramic substrate for mounting a semiconductor, because it has a characteristic of being extremely small and having a very small warpage even when subjected to a temperature change. Furthermore, the heat radiating component of the present invention
In addition to the above features, it is high in strength and lightweight, and thus is suitable as a heat dissipating component suitable for mobile devices such as electric vehicles and automobiles.

Claims (4)

[Claims] 1. A plate-shaped composite body in which a silicon carbide porous body is impregnated with a metal containing aluminum as a main component, wherein the difference in oxygen amount between the opposite main surfaces is 0.5% by weight or less. A plate-like composite characterized by the above-mentioned. 2. The method according to claim 1, wherein the amount of warpage when heated from room temperature (25 ° C.) to 300 ° C. is 5 μm or less for a length of 1 mm in a direction in which the warp is maximum. Plate composite. 3. A test piece (A) having a diameter of 3 mm and a length of 10 mm.
And a test piece (B) having a diameter of 1.5 mm and a length of 10 mm were sampled so that the length direction was parallel to the main surface of the plate-like composite, and the respective coefficients of thermal expansion were measured with a push-rod type thermal dilatometer. 2. The plate-like plate according to claim 1, wherein the difference between the apparent thermal expansion coefficients of the test piece (A) and the test piece (B) is 1 × 10 ⁻⁶ K ⁻¹ or less. Complex. 4. A heat-dissipating component using the plate-shaped composite according to claim 1, 2 or 3.