JP2010208883A - Structure having carbon nanotube layer on substrate surface and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure which has a layer formed with a carbon nanotube (a carbon nanotube layer) on the substrate surface, where the carbon nanotube layer is firmly adhered to the substrate surface. <P>SOLUTION: The subject is solved by a structure which is characterized by having a substrate and a carbon nanotube layer formed on its surface by growing from a catalyst which is an alloy containing at least one kind of Fe, Ni or Co and has a melting point of 700-1,050°C and not exceeding the melting point of the substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a structure using a carbon nanotube layer, a heat dissipation component using the structure, and a manufacturing method thereof.

  As personal computers and mobile electronic devices become more sophisticated and densely mounted, the amount of heat generated per unit area of heat sources such as CPUs, GPUs, chipsets, and memory chips has increased dramatically. High performance is required.

  A simple and effective method as one of the heat dissipating devices is a method of reducing the heat resistance by attaching a heat dissipating sheet or interposing grease on the surface of the heat source. Such a heat radiating material has a high thermal conductivity, but the contact thermal resistance is lowered by entering the gap between minute irregularities present on the surface of the heat source without any gap. When there is a gap, air with a very low thermal conductivity is interposed there, so that the contact thermal resistance with the heat source increases.

  Inventors efficiently absorb heat by forming a layer made of carbon nanotubes on the surface of a substrate such as metal instead of the heat dissipation material, and bringing the tips of the carbon nanotubes, particularly the carbon nanotubes, into contact with the surface of the heat source. It has been found that the contact thermal resistance between the carbon nanotube and the heat source can be extremely reduced (for example, Japanese Patent Application No. 2007-274610). It has also been found that low thermal resistance can be realized by bringing carbon nanotubes into perpendicular contact with the surface of the heat source (Japanese Patent Application No. 2007-308263).

  It is said that the thermal conductivity of carbon nanotubes in the longitudinal direction is comparable to diamond. For example, when the tips of carbon nanotubes are brought into contact with the surface of the heating element, the tips of the fine carbon nanotubes become uneven portions on the surface of the heating element. Very good contact and low thermal resistance.

  The CVD method is widely used as a method for forming carbon nanotubes grown perpendicular to the substrate surface at a relatively low temperature. In the CVD method, after applying a catalyst such as Fe or Co to the substrate surface, a hydrocarbon gas or an alcohol gas is transported onto the substrate and reacted at a temperature of about 500 to 800 ° C. to grow carbon nanotubes from the catalyst. The carbon nanotubes tend to have a vertically aligned structure (Patent Document 1).

  In general, the carbon nanotubes formed by the CVD method have a low adhesion to the substrate, and may be easily peeled off only by rubbing by hand, resulting in a defect of lack of reliability.

JP 2001-048512 A

  An object of the present invention is to provide a structure in which a layer formed of carbon nanotubes is adhered to a substrate.

  Therefore, as a result of investigations for solving the above problems, the present inventor formed carbon nanotubes by a CVD method on a low melting point metal layer previously formed on the substrate surface as a method for improving the adhesion strength of the carbon nanotubes to the substrate. After that, the inventors considered a method of increasing the adhesion at the contact point of the carbon nanotube with the substrate by heating above the temperature at which the metal melts.

However, with this method, although considerable improvement is recognized, it has been found that the formed carbon nanotubes are likely to be buried in the low melting point metal, and the number of carbon nanotubes exposed on the surface is extremely reduced. That is, as shown in the conceptual diagram of FIG. 1, when the low melting point metal melts, the molten metal wets so as to cover the surface of the carbon nanotubes by capillary force. For this reason, the exposed part of the carbon nanotube is extremely reduced, and the flexibility specific to the carbon nanotube is reduced.
Therefore, when such a structure is used as a heat radiating component, the contact thermal resistance decreases because the contact with the counterpart material decreases. In addition, with this phenomenon, the surface is likely to be uneven, and more difficult to contact the counterpart material, resulting in an increase in thermal resistance.

Accordingly, as a result of further investigations based on these problems, the present inventor has found that it is effective to embed the base portion of the carbon nanotube in the catalyst metal, and completed the present invention. The present invention has the following configuration.
(1) A substrate and a carbon nanotube layer grown from a catalyst formed on the surface thereof, wherein the catalyst is an alloy containing at least one of Fe, Ni, or Co, and the melting point of the catalyst is 700 to 1050. A structure characterized in that it does not exceed the melting point of the substrate at ° C.
(2) The above, wherein the catalyst is an Fe-based alloy containing Fe as a first component and at least one of Ga, Ge, Nd, Zn, Zr, or Ce as a second component. The structure according to 1).
(3) The above-mentioned (1), wherein the catalyst is a Ni-based alloy containing Ni as the first component and at least one of Se, Te, Zr, Au, or Bi as the second component. The structure described in 1.
(4) The structure according to claim 1, wherein the catalyst is a Co-based alloy containing Co as a first component and at least one of Ge or Zn as a second component.
(5) The catalyst is a mixture of two or more of an Fe-based alloy specified in (2) above, an Ni-based alloy specified in (3) above, or a Co-based alloy specified in (4) above. The structure according to (1) above, which is a thing.

(6) The structure according to any one of (1) to (5), wherein the substrate is Cu or a Cu alloy.
(7) The structure according to any one of the above (1) to (6), wherein the carbon nanotube stands on the substrate surface.
(8) The structure according to any one of (1) to (7) above, wherein the carbon nanotube layer has a thickness of 50 to 500 μm.
(9) The structure according to any one of (1) to (8) above, wherein a void portion of the carbon nanotube layer is impregnated with a resin.
(10) A heat dissipation component using the structure according to any one of (1) to (9) above.

(11) The method for manufacturing the structure according to any one of (1) to (8) above, wherein the surface of the substrate is an alloy containing at least one of Fe, Ni, or Co as the first component. A first step of forming a catalyst having a melting point of the alloy of 700 to 1050 ° C. and not exceeding a melting point of the substrate, a second step of growing carbon nanotubes from the catalyst, a melting point of the catalyst or higher, and And a third step of heating at a temperature not exceeding the melting point of the substrate.
(12) The above catalyst, wherein the catalyst is an Fe-based alloy containing Fe as a first component and at least one of Ga, Ge, Nd, Zn, Zr, or Ce as a second component. The manufacturing method of the structure as described in 11).
(13) The catalyst according to (11), wherein the catalyst is a Ni-based alloy containing Ni as the first component and at least one of Se, Te, Zr, Au, or Bi as the second component. A method for producing the structure according to 1.
(14) The structure according to (11), wherein the catalyst is a Co-based alloy containing Co as a first component and at least one of Ge or Zn as a second component. Production method.
(15) The method for manufacturing a structure according to any one of (11) to (14), wherein the substrate is Cu or a Cu alloy.

The present invention provides a structure having a carbon nanotube layer that is firmly adhered to the surfaces of various substrates. When such a structure is applied as a heat dissipation component, the carbon nanotubes that lower the heat resistance of the heat dissipation plate are in close contact with the heat dissipation substrate, so that the carbon nanotubes do not easily fall off and a highly reliable heat dissipation component can be obtained. . The present invention is highly effective when used for heat sinks, heat pipes, heat spreaders and the like having a high heat dissipation performance including inexpensive Al and Cu substrates, and other high heat conduction heat dissipation substrates.
Furthermore, the structure according to the present invention can be used not only as the heat dissipation component but also as an electrical contact material, an electron emission material (emitter), or the like.

It is the schematic showing an example of the improvement example of a structure. It is the schematic showing an example of the structure concerning the present invention. It is a figure showing the outline of the apparatus which measures the thermal resistance used in the Example.

  As shown in the conceptual diagram of FIG. 2, the structure according to the present invention includes a carbon nanotube layer in which a base portion of carbon nanotubes is embedded in a catalytic metal layer formed on a substrate surface, and which is firmly adhered to the substrate surface. It is the structure which has. Since the catalyst itself is a particulate low-melting-point metal and the catalyst particles are dispersed at an appropriate interval, when the catalyst is melted, the molten metal preferentially wets the substrate surface over the carbon nanotubes. For this reason, the exposure of the carbon nanotube is maintained and the surface of the structure becomes flat.

  The catalyst used in the present invention is an alloy containing at least one of Fe, Ni, or Co necessary for growing carbon nanotubes, and has a melting point in the range of 700 to 1050 ° C. If the upper limit is exceeded, for example, if a Cu substrate (melting point is 1080 ° C.) is used, the substrate is likely to be deformed. Fe, Ni, and Co each have a high melting point, and even when alloyed, it is difficult to lower the melting point to 700 ° C. or lower. In order to make it 700 degrees C or less, content of the 2nd component metal at the time of alloying will become high, and a Fe, Ni, Co ratio will fall and it will become difficult to produce | generate a carbon nanotube.

The Fe-based alloy is preferably an alloy containing Fe and at least one of Ga, Ge, Nd, Zn, Zr, or Ce as the second component.
The Ni alloy is preferably an alloy containing Ni and at least one of Se, Te, Zr, Au, or Bi as the second component.
The Co-based alloy is preferably an alloy containing Co and at least one of Ge, which is the second component, or Zn.
Any one or more of these Fe-based alloys, Ni-based alloys, and Co-based alloys may be mixed and used.

The substrate is not particularly limited, and various metal substrates, ceramic substrates, and the like can be used. When the structure according to the present invention is applied as a heat dissipation component, the thermal conductivity of the substrate is preferably 100 W / mK or more, and CuW, CuMo, SiC, AlN, carbon, diamond, Al, Al alloy, Cu Cu alloy is preferable. Of these, Al, Al alloy, Cu, Cu alloy, etc., which are inexpensive and have high thermal conductivity, are preferable.
Conventional catalytic metals such as Fe, Ni, and Co are metals having a high melting point. For this reason, when using a metal substrate having a lower melting point than these catalytic metals, it is necessary to make the melting point of the catalytic metal lower than the melting point of the metal substrate. In order to lower the melting point of the catalytic metal, it may be alloyed with a metal having a low melting point, but on the other hand, when the proportion of the non-catalytic metal is increased, there arises a problem that the production efficiency of the carbon nanotube is lowered. For this reason, the material of the substrate is preferably Cu or a Cu alloy having a small melting point difference from the catalyst metal (Fe, Ni, Co, etc.).

  In the case of a heat radiating component, the substrate may be a surface portion such as a heat sink, a heat pipe, or a heat spreader. Further, a component of a semiconductor package such as a CPU casing may be used as a substrate. By forming the carbon nanotube layer on the surface portion of the cooling body or the heating element in such a manner that the carbon nanotube layer is in contact with the counterpart material, the contact property with the counterpart material is improved and the heat dissipation effect is enhanced. In addition, since the carbon nanotube layer is firmly adhered to the substrate surface, the effect is not lowered even with repeated use, and the carbon nanotube layer is excellent in reliability.

  Although the thermal resistance is smaller when the carbon nanotubes are erected vertically with respect to the substrate surface, they may be disturbed. If formed vertically, the fine tips of the carbon nanotubes can easily come into contact with the minute irregularities on the surface of the counterpart material without gaps, but the effect is great even if they are slightly inclined with respect to the substrate surface. It will not be damaged.

It is preferable that the exposed carbon nanotube layer is thicker because the carbon nanotube can easily follow even when the flatness of the surface of the counterpart material is low, and the contact property is improved. The effect is large when the thickness is 50 μm or more. When the thickness exceeds 500 μm, the effect of improving contactability is saturated. However, when the flatness of the counterpart material is high, it may be smaller than this thickness.
It is preferable to impregnate such a gap portion of the carbon nanotube layer with a resin such as grease because the contact property with the counterpart material is further improved and the thermal resistance is lowered.

  The method for producing a structure according to the present invention includes a first step of forming a catalytic metal on a substrate surface, a second step of forming a carbon nanotube from the catalytic metal, a melting point of the catalytic metal or higher, and And a third step of heating at a temperature not exceeding the melting point of the substrate. The catalytic metal is an alloy containing at least one of Fe, Ni, or Co, and has a melting point of 700 to 1050 ° C. and does not exceed the melting point of the substrate.

  In the above production method, the catalyst metal is (1) an alloy containing Fe as the first component and at least one of Ga, Ge, Nd, Zn, Zr, or Ce as the second component, or (2 ) An alloy containing Ni as the first component and at least one of Se, Te, Zr, Au, or Bi as the second component, or (3) Co as the first component and the second component It is preferable that it is an alloy containing at least one of Ge and Zn. Further, any one or more of these Fe alloys, Ni alloys, and Co alloys may be mixed and used.

  The substrate is not particularly limited, and various metal substrates, ceramic substrates, and the like can be used. When the structure provided by this manufacturing method is applied as a heat dissipation component, the thermal conductivity of the substrate is preferably 100 W / mK or more, and CuW, CuMo, SiC, AlN, carbon, diamond, Al, Al. An alloy, Cu, Cu alloy or the like is preferable. Of these, Al, Al alloy, Cu, Cu alloy, etc., which are inexpensive and have high thermal conductivity, are preferable. As described above, when a metal substrate having a melting point lower than that of the catalyst metal is used, Cu or a Cu alloy having a small difference in melting point from the catalyst metal is preferable.

Below, an example of the manufacturing method of the structure which concerns on this invention is shown for a Fe type catalyst as an example.
First, an Fe alloy catalyst is deposited on the surface of the Cu substrate by sputtering (first step). For example, Fe and Zn targets are prepared, and an Fe-50Zn alloy catalyst is formed by binary simultaneous sputtering. The melting point of this alloy is about 800 ° C.
Next, this substrate is placed in a CVD furnace to form carbon nanotubes (second step). There are no particular restrictions on the raw materials and reaction conditions, and known methods can be used.
Finally, the substrate is heated at 900 ° C. to melt the alloy catalyst and the treatment is completed (third step).

  Thus, in the manufacturing method according to the present invention, it is not necessary to previously form a low melting point metal layer on the surface of the substrate, so that the number of steps is reduced, and a carbon nanotube film with high adhesion can be formed at low cost.

(1) Material <Board>
A Cu substrate having a size of 10 × 10 mm and a thickness of 0.25 mm was used.
<Formation of carbon nanotubes>
It formed as follows.
Various alloy catalysts were sputtered on the substrate. The melting point of the catalyst was confirmed by differential thermal analysis (DTA).
Next, the substrate was placed in a CVD furnace, a carbon nanotube layer was formed using ethanol gas and argon gas as a carrier gas, and then heat-treated in the same furnace at various temperatures and under vacuum (using a rotary pump).

[Comparative example]
A plating layer made of an Ag-28 wt% Cu alloy having a thickness of 25 μm was formed on both surfaces of the substrate by plating.
On the plating layer, Fe, Ni, or Co was sputtered. Thereafter, the substrate was placed in a CVD furnace, carbon nanotubes were formed in the same manner as in the examples, and heat treatment was performed.

(2) Evaluation <Measurement of thermal resistance>
The sample was set in the thermal resistance measuring apparatus shown in FIG.
Silicon grease having a thermal conductivity of 0.8 W / mK was applied to the surface of the lower Cu holder in advance to a thickness of 150 μm, and then the sample was sandwiched between the upper and lower Cu holders. An amount of heat Q was added by heating at 13.3 V and 220 mA with an AlN heater from the top. The temperature at each position of the upper and lower Cu holders was measured and held until it reached a steady state. The circumference of the Cu holder was surrounded by a heat insulating material.

The upper and lower copper holders sandwiching the sample are provided with five thermocouple insertion holes each, and the temperature of the heating element surface and the fin tip of the heat sink was extrapolated from the gradient of the temperature distribution at these positions. . While adjusting the surface pressure, pressurization was performed so that the distance between the Cu holders was 450 μm (the distance between the substrate surface and the Cu holder surface was 100 μm), and the pressure was released after holding for 30 seconds. After repeating this 50 times (samples No. 1 and 3 were not subjected to this operation), the thermal resistance was measured in a state where the distance between the Cu holders was 450 μm.
The surface temperature (T1) and back surface temperature (T2) of the sample were extrapolated from the temperature gradient in each Cu holder when the steady state was reached.

The thermal resistance was calculated by the following formula.
Thermal resistance (K / W) = (T1-T2) / Q

<Result>
The results are shown in Table 1.
The product of the present invention maintained a low thermal resistance even after repeated stress loading and an open test. This is considered because the adhesion strength of the carbon nanotube to the substrate is high.

Claims (15)

A substrate and a carbon nanotube layer grown from a catalyst formed on the surface of the substrate;
The catalyst is an alloy containing at least one of Fe, Ni, or Co;
A structure characterized in that the melting point of the catalyst is 700 to 1050 ° C. and does not exceed the melting point of the substrate.   2. The Fe-based alloy containing Fe as a first component and at least one of Ga, Ge, Nd, Zn, Zr, or Ce as a second component, according to claim 1. Structure.   2. The structure according to claim 1, wherein the catalyst is a Ni-based alloy containing Ni as a first component and at least one of Se, Te, Zr, Au, or Bi as a second component. body.   2. The structure according to claim 1, wherein the catalyst is a Co-based alloy containing Co as a first component and at least one of Ge or Zn as a second component.   The catalyst is a mixture of two or more of an Fe-based alloy defined in claim 2, a Ni-based alloy defined in claim 3, or a Co-based alloy defined in claim 4. The structure according to claim 1.   The structure according to claim 1, wherein the substrate is Cu or a Cu alloy.   The structure according to any one of claims 1 to 6, wherein the carbon nanotube stands on the substrate surface.   The structure according to claim 1, wherein the carbon nanotube layer has a thickness of 50 to 500 μm.   The structure according to any one of claims 1 to 8, wherein a void portion of the carbon nanotube layer is impregnated with a resin.   A heat dissipation component using the structure according to any one of claims 1 to 9. It is a manufacturing method of the structure according to any one of claims 1 to 8,
A first alloy is formed on the surface of the substrate, which is an alloy containing at least one of Fe, Ni, or Co as the first component, and has a melting point of 700 to 1050 ° C. and does not exceed the melting point of the substrate. Process,
A second step of growing carbon nanotubes from the catalyst;
And a third step of heating at a temperature not lower than the melting point of the catalyst and not exceeding the melting point of the substrate.   12. The Fe-based alloy containing Fe as a first component and at least one of Ga, Ge, Nd, Zn, Zr, or Ce as a second component. Method for manufacturing the structure.   12. The structure according to claim 11, wherein the catalyst is a Ni-based alloy containing Ni as a first component and at least one of Se, Te, Zr, Au, or Bi as a second component. Body manufacturing method.   The method for producing a structure according to claim 11, wherein the catalyst is a Co-based alloy containing Co as a first component and at least one of Ge or Zn as a second component.   The method of manufacturing a structure according to claim 11, wherein the substrate is Cu or a Cu alloy.

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