JPH09129792A - Radiation board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize sufficient contact strength of a plating film by providing, on a metal surface layer, an underlying plating layer having specified or higher contact strength with respect to a carbon fiber composite material having a specified or higher thermal conductivity in one direction. SOLUTION: A board member 1 is made of a carbon fiber composite material, and a metal surface layer made of Ni, Cu or Au is formed on the surface of the board member 1. This metal surface layer is provided with an underlying plating layer 2 having contact strength not less than 2.0kgf/mm<2> with respect to a carbon fiber composite material having a thermal conductivity of at least 300W/m.K in one direction. Thus, in performing metal plating on the board member 1, the plating layer 2 has sufficient contact strength so that a desired coefficient of thermal expansion may be secured and a high heat transfer coefficient may be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a semiconductor element mounted thereon, and a heat dissipation substrate made of a carbon fiber composite material having high thermal conductivity, the surface of which is provided with a metal layer having high adhesion strength, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a heat dissipation substrate used for a semiconductor device having a semiconductor element mounted thereon, a material having a higher heat dissipation property is required as the integration progresses in recent years.

However, the performance of semiconductor elements such as Si and GaAs may deteriorate due to heat, and if the difference in the coefficient of thermal expansion from the substrate on which they are mounted is large, peeling may occur due to repeated use.

A specific material will be described. Copper is 3
High thermal conductivity of 80 W / mK, but coefficient of thermal expansion of 1
It is as large as 6.3 × 10 ^-6 / K, and it is difficult to use it for a high-precision semiconductor device because of a large difference from peripheral elements such as elements or ceramics.

On the other hand, Cu-W is often used because the difference in the coefficient of thermal expansion between the element and the peripheral members is moderate. This Cu-W has a thermal conductivity of 210/250 W / m · K and a thermal expansion coefficient of 6.5 to 8.5 × 10 ⁻⁶ / K, and is therefore excellent from the above physical property requirements. .

[0006]

However, in addition to the progress of integration, weight saving is an important factor in handy type devices such as handy personal computers and semiconductor devices operating in space.

Furthermore, recently, designs such as multichip modules in which a plurality of semiconductor elements are mounted have been put into practical use. In this case, in order to avoid noise between elements due to heat, it is necessary to reduce the weight as well as high thermal conductivity in order to avoid an increase in weight corresponding to a multi-chip, more than ever before.

From the viewpoint of weight reduction, the density of copper is 8.9.
g / cm ^3, Cu-W is heavier compared to Al ₂ O ^₃ 3.6g / cm ₃ as shown in the example of 15.5~17g / cm ³ and a peripheral member. AlN has a density of 4.5 g / cm ³ , a thermal conductivity of 170 to 200 W / m · K, and a thermal expansion coefficient of 4.4 × 1.
It features 0 ^-6 / K and is characterized by its lightness. Also, AlS
i (for example, Sumitomo Electric A40) has a density of 2.5 g / cm
³ , thermal conductivity 125W / mK, thermal expansion coefficient 3.0 × 1
It is 0 ^-6 / K, and the thermal conductivity of both AlN and AlSi is insufficient.

4.2 × 10 ⁻⁶ / K Si, 6.5 × 10
There is a demand for a heat dissipation substrate having a thermal expansion coefficient larger than that of a semiconductor such as ^-6 / K GaAs and smaller than that of Cu-W. Specifically, it has a thermal expansion coefficient in the range of 8.5 × 10 ^-6 / K or less, and more importantly, the thermal conductivity is 200 W / m · K or more, which is larger than AlN, and preferably 300 W / m · k. As described above, there is an increasing demand for a heat dissipation substrate that is larger than Cu-W and Al and that has a smaller density than copper and more desirably smaller than AlN.

In recent years, some carbon fiber composite materials have an excellent anisotropy, although they have anisotropy due to the way fibers are present. For example, CX-2 manufactured by Toyo Tanso Co., Ltd.
002U and FORCA UD C manufactured by Tonen Co., Ltd.
/ C etc.

However, these materials are porous, which is not suitable for practically preferable wet plating, and the fibers are in a certain direction, so that fluff remains at the time of cutting, and in the case of precision cutting with a blade. It is difficult to manage because the cutting resistance differs in the fiber direction or the direction perpendicular to it. Further still to overcome these, at least 1 kgf / cm ² or more required in the heat dissipation substrate used for a semiconductor device mounting a semiconductor device, preferably, the adhesion strength of 2 kgf / cm ² or more consider the case of assembling the lead wire There is no example in which the metal surface layer has been practically successful.

If so-called so-called carbon fiber composite materials can be metal-plated to obtain a heat dissipation board having sufficient adhesion strength as described above, it can be expected to be applied to a semiconductor device as a lightweight and high heat conduction board in the future. .

Therefore, the technical problem of the present invention is that when the carbon fiber composite material is plated with metal, the plating film has sufficient adhesion strength, a desired coefficient of thermal expansion, and a reduction in weight. Further, it is to provide a heat dissipation board having excellent thermal conductivity, a manufacturing method thereof, and a semiconductor device using the heat dissipation board.

[0014]

Means for Solving the Problems The inventors of the present invention formed a base plating layer having high adhesion strength by removing fluffy fibers of a carbon fiber composite material, and formed the carbon fiber composite material on a substrate member. As a result, a metal surface layer can be formed on the surface of the substrate member, and the present invention has been accomplished.

According to the present invention, in the heat dissipation substrate on which the semiconductor element is mounted, the heat dissipation substrate is substantially composed of a substrate member formed of a carbon fiber composite material and a metal surface layer formed on the surface of the substrate member. The fiber composite material has a thermal conductivity of at least 300 W / mK in at least one direction, and the metal surface layer is 2.0 kg relative to the carbon fiber composite material.
A heat dissipation board is obtained which is characterized by including a base plating layer having an adhesion strength of f / mm ² or more.

Further, according to the present invention, in a semiconductor device including a semiconductor element and a heat dissipation board on which the semiconductor element is mounted,
A semiconductor device is obtained which uses the heat dissipation substrate as the heat dissipation substrate.

Further, according to the present invention, in the method for manufacturing a heat dissipation substrate on which a semiconductor element is mounted, a carbon fiber composite material is prepared as a substrate member, and after the carbon fiber composite material is fluffed, the substrate member is A method for manufacturing a heat dissipation substrate is obtained, which is characterized in that a metal surface layer is formed on the surface of.

[0018]

Embodiments of the present invention will be described below.

The heat dissipation board according to the embodiment of the present invention is
It is used for a heat dissipation board for a semiconductor device on which a semiconductor element is mounted. This heat dissipation substrate is composed of a substrate member made of a carbon fiber composite material and a metal surface layer formed on the surface of the substrate member. This carbon fiber composite material has a thermal conductivity of at least one direction of the substrate of 300 W / m · K.
That is all. Further, the metal surface layer includes at least a base plating layer having an adhesion strength of ² kgf / mm ² or more with respect to the carbon fiber composite material.

Further, according to the method for manufacturing a heat dissipation substrate according to the embodiment of the present invention, the above-mentioned metal surface layer is formed on the surface of the substrate member made of the carbon fiber composite material by the steps described later. The above adhesion strength can be obtained for the composite material.

Here, a method of molding the carbon fiber composite material used for the substrate member according to the embodiment of the present invention will be described. Carbon fiber composite materials are basically cut, cut, and ground, but when the cut is large or when dimensional accuracy is strictly required, it is preferable to use wet method with alcohol, water medium, etc. It doesn't change.

The present inventors have found out that lapping cutting using silicon carbide abrasive grains is particularly suitable for ensuring the dimensional accuracy of the carbon fiber composite material as well as the surface roughness of the cut surface.

Further, the inventors of the present invention have found that the plating strength in the plating step as the step of forming the metal surface layer after forming the carbon fiber composite material is such that the cut fibers are originally thin fibers on the surface. It was found that it changes depending on whether or not it is fluffy on the surface.

Therefore, by removing the fluffy fibers, it was possible to form the above-mentioned base plating layer having high adhesion strength and the metal surface layer.

Specifically, the fluffy fibers in the form of the thin fibers are ceramic balls and an object to be treated (hereinafter,
C / C substrate) can be removed by wet barrel polishing with the above alcohol or water. For example, □
The fluffy fibers when plating treatment to 20 × T1.0 was desired could be removed by using a D1.0 ball of SiC.

Here, as the carbon fiber composite material used in the embodiment of the present invention, two types of commercially available carbon fiber composite materials shown in Table 1 below are considered to have excellent thermal conductivity (//) in the fiber direction. Materials can be used.

[0027]

[Table 1]

However, the materials are not limited to those listed in Table 1. Each carbon fiber composite material has voids of about 20 vol%, and the density is 1.
Extremely lightweight with 7 g / cm ³ .

Next, the method for forming the metal surface layer according to the embodiment of the present invention will be described in more detail. The heat dissipation board used for the semiconductor element device mounting the semiconductor element is
In many cases, brazing with the peripheral members or solder plating is performed, and it is often required to form a metal surface layer of Ni, Cu, Au or the like on the outermost surface layer. Regarding the C / C base material and the material of the outermost surface layer, in order to secure the adhesion strength, it is preferable to exclude the combination of materials that significantly impair heat conduction and use the intermediate auxiliary layer.

Next, as a method of forming a metal surface layer according to an embodiment of the present invention, ion plating which is dry plating will be described. As a system that can withstand various heat histories of carbon, which is basically the material of the substrate member, and the heat dissipation substrate, the standard free energy of formation of carbides is stable, and in particular, the normal heat history range is -200 to 800 ° C.
It has been found that a metal of 10,000 cal / mol ° C or less is preferable. If selected from the standard free energy temperature diagram of this carbide, V, Ta, Ti, Zr, and Nb are selected as the metal forming the undercoating layer of the metal surface layer.

However, considering the thermal conductivity of the carbide when it is formed, Ta and Z are selected from these.
r is excluded. After all, V, Ti, Nb are Ni, Cu, A
It is preferably applied as a base plating layer of a metal surface layer such as u. Further, the C / C of the substrate member is preferably heated to 150 ° C. or higher during ion plating.

The base plating layer should be at least 0.2.
If it is not more than μm, there is a fear of pinholes due to the shape of the substrate member. Further, if it exceeds 0.5 μm, it is disadvantageous in terms of cost, and therefore it is not necessary to unnecessarily increase the thickness.

A ground plating layer formed by the above ion plating, or N on the ground plating layer
A metal surface layer of i, Cu, Au or the like is applied. This metal surface layer may be formed by a usual plating method. The one to which this metal surface layer is applied has an adhesion strength of 3 kgf / mm ² or more, and can be sufficiently used as a heat dissipation board in a semiconductor device mounting a semiconductor element. Alternatively, the base plating layer may be used as it is as a heat dissipation substrate.

Next, a wet plating method will be described as a method for forming a metal surface layer according to another embodiment of the present invention.

In one embodiment of the present invention, since the substrate member is made of carbon fiber composite material, unlike the case of plating on a metal body, it is not a good electric conductor and is porous.
How to make sure the seeding of plating,
The point is to increase the thickness of the plating layer and strengthen the adhesion strength after applying it thinly and evenly.

First, as a first step, in order to form a stable and reliable background, the surface of the substrate member is activated at a low temperature of 30 to 35 ° C. in the coexistence of palladium chloride and stannous chloride, and then tin is added with hydrochloric acid at room temperature. After elution, apply nickel oxide chemical nickel primary plating.

At this time, the chemical nickel primary plating is carried out in the presence of sodium hypophosphite and citric acid in a nickel sulfate solution at 30 to 35 ° C. and a slight alkali of pH 9 to 10. If the temperature is raised beyond this temperature range, it is easy to destroy the delicate reducing atmosphere or oxidizing atmosphere.
If a thick film portion is formed as the secondary plating, it is inconvenient because the subsequent secondary plating lacks stability.

Finally, electrolytic nickel plating substantially secures the desired thickness of the plated film and increases the adhesion strength.

According to the experiments conducted by the present inventors, it has been found that the adhesion strength cannot be obtained when the current density flowing through the object to be plated (commonly known as the work) is made to reach the required straightness. In consideration of this, it was found that the strength can be ensured by starting at 1/3 or less of the required maximum current density and reaching a predetermined current density in two or more steps.

As described above, low-temperature activation treatment in the presence of palladium chloride and stannous chloride, primary oxidation chemical plating are performed, and further, an electric secondary that increases the current density stepwise in two or more steps. Perform plating. As a result, a metal surface layer that is uniform and stable and has excellent adhesion strength can be produced.

The term "adhesion strength" as used herein refers to the degree of adhesion between a substrate member made of a carbon fiber composite material and a metal surface layer when the metal surface layer is pulled in the film forming direction.

On the other hand, regarding the adhesion strength, the necessity thereof has been described above, but the degree of the strength will be described.

It is desired that the heat dissipation board according to the embodiment of the present invention is firm in view of brazing with peripheral members and the like. For example, as a harsh case, in terms of tight contact when brazing a lead wire, a pin having a diameter of 0.8 mm must be able to withstand 3 kgf or more by pulling after brazing. This value is approximately 0.1 kgf / mm ^{2 when} converted per unit area.
Therefore, for sufficient safety, a strength of 1 kgf / mm ² or more is required. Further, in the case of a metal material base material, it is inconvenient that the metal surface layer peels off prior to the solder or brazing material itself, and it is said that 1-2 kgf / mm ² or more is sufficient as a standard. However, there is no theoretical background, and no accident has been confirmed even at this level.

As described above, in the embodiment of the present invention, since the carbon fiber composite material forming the substrate member is porous and is a non-electrical material, the same plating on the metal substrate member is performed. A reliable film cannot be obtained under the conditions, and it is necessary to develop an undercoat that matches the substrate material. As for the undercoating, so-called electroplating and ion plating were variously studied, and the combinations of the compositions of the metal surface layer that were practically practicable and were achieved are shown below.

From the bottom layer, electroplating bases; Ni, C
u / surface layer; combination of Ni, Cu, Ag, Au, or, in order from the bottom layer, ion plating base; Ti,
The combination of V, Nb / surface layer; Ni, Cu, Ag, Au enabled reliable undercoating.

[0046]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 Base material FORCA shown in Table 1 above
UD C / C was lapped and cut to T0.5 × 10 × 10 by an alcohol wet bandry cutting machine, and after washing, SiC balls with a diameter of 1.0 mm were about 10 in an aqueous medium.
Minute milling was performed to remove fluff. After washing with water, activation treatment is performed at 30 to 35 ° C. in the coexistence of palladium chloride and stannous chloride, and then after acceleration with HCl (Sn elution), oxidation chemical undercoating is started.

Next, as electrochemical primary plating, nickel hydrochloric acid was adjusted to pH 9.0 to 9.5 (33 to 36 ° C.) with ammonia water in the presence of sodium hypophosphite and citric acid, and Ni primary plating was performed. At 20 to 30 A / dm ²
A μm film was formed.

Finally, as the electrochemical secondary plating, plating was performed by putting the above base material in a solution containing nickel sulfate, nickel chloride, boric acid, etc. and energizing. The main purpose is to gradually increase the current density, but the voltage value is used for control purposes.
1.2V-2 minutes, 2.5V-1 minutes, 3.5V-1 minutes,
4.2V-2 minutes, 4.5V-10 minutes, current density 1.5A
/ Dm ² ) for a total of 16 minutes.

As a result, Ni of the base plating layer was 1.0 μm.
m, and the surface was smooth. After this, normal Au
Plating was performed for 2 to 3 μm, and four samples were arranged by a tensile test by the method shown in FIG. 1 and the adhesion strength due to peeling of the plating layer was measured and found to be 2.3 kgf / mm ² . The thermal conductivity in the fiber direction of the base material of the obtained sample was 458 W / m · K (RT to 600 ° C).

Example 2 Base material FORCA in Table 1 above
UD C / C is cut with a wet inner cutter to remove T1.
The pieces were cut into 0 × 20 × 20 (fiber direction T1.0 thickness direction), and SiC balls having a diameter of 1.0 mm were milled in an aqueous medium for about 10 minutes in the same manner as in the previous example, and fluffing was performed. After washing this sample with water, 1,000 ℃ × 10 ^-6 Torr, 3H
r dried. Next, Ti was formed into a film by high frequency excitation type ion plating. Substrate is heated to 170 ° C for 20
A film having a thickness of 0.2 μm was formed in a minute. The obtained sample had a smooth surface and a dense film.

Further, ordinary Ni plating is added here by a few times.
When the adhesion strength was measured by the same method as in Example 1 after carrying out μm, it was 5.1 kgf / mm ² . The thermal conductivity in the fiber direction of the base material of the obtained sample is 472 W / m.
-It was K (RT-600 degreeC). As for the ground ion plating, V and Nb are almost the same (3
A film having an adhesion strength of ˜6 kgf / mm ² ) was obtained. In addition, the film thickness is uneconomical if it is 1 μm or more in accordance with the usual ion plating, and the thinner the better.

As a comparative example, when the film forming material was changed to Ni under the same conditions as the above-mentioned sample, the adhesion strength was 0.7 k.
Only gf / mm ² was obtained. Moreover, hair cracks were scattered on the surface. Also, when the film forming material was changed to Ta, the adhesion strength was obtained but the thermal conductivity was 280 W / m.
-Not only the characteristics of the carbon fiber composite material were not utilized, such as the occurrence of a portion where only K was obtained, but the result was similar to that of Cu-W.

Example 3 Base material CX-200 shown in Table 1 above.
2U of T is cut by an alcohol wet bandy cutting machine.
After lapping into 1.0 × 20 × 20 and washing, SiC balls with a diameter of 1.0 mm were milled in an aqueous medium for about 10 minutes to remove fluff. In the same steps as in Example 1, a primary Ni plating of 0.2 μm was formed, and the next electroplating was performed at an electrolysis voltage and plating time of 3.2 A / dm ² at the final current density, respectively. 2V-2 minutes, 2V-2
Min, 3V-1 min, 3.3V-10 min, a total of 15 minutes, and a 0.3 μm film was added. As a result, the thickness of the underlying plating layer was 0.5 μm. After this, with normal electroplating,
When Ni was applied at 1 μm and the adhesion strength was measured by the same method as in Example 1, 2.8 kgf / mm ² was obtained, and the thermal conductivity in the fiber direction was 460 W / m · K (RT to 600 ° C.). It was

Where the substrate is a metal, nickel is generally plated at about 3-5 A / dm ² , while carbon fiber composites have favored low current densities. However, if it is too low, it is not practical because of the stability of the device, etc.
/ Dm ² or more. For example, for a small item of 2 × 3 × 5 mm, the test was performed at 1.0 to 1.5 A / dm ² . Regarding the underlying electroplating, Cu could be formed under almost the same conditions.

On the other hand, when the activation treatment in the coexistence of palladium chloride and stannous chloride was omitted, or when the current density was 3.0 A
/ Dm ² is applied all at once, and in both cases, color unevenness on the surface and adhesion strength are 0.4 kgf / mm ² and 0.9 kgf.
/ Mm ² and less than 1 kgf / mm ² , a reliable heat dissipation board that can withstand use was not obtained.

[0057]

As described above, according to the present invention, a substrate member made of a carbon fiber composite material and a metal surface layer formed on the surface of the substrate member are provided. 2kgf / mm for this carbon fiber composite
By including a base plating layer having an adhesion strength of ² or more, a heat dissipation substrate for a semiconductor device having a desired coefficient of thermal expansion, weight reduction, and excellent thermal conductivity, and its manufacture A method can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method of measuring adhesion strength by peeling a plating layer of a heat dissipation substrate sample according to an example of the present invention.

[Explanation of symbols]

 1 base material 2 plating layer 3 brazing material 4 pulling jig 5 arrow indicating the direction of applied force

Claims (12)

[Claims] 1. A heat dissipation board on which a semiconductor element is mounted, which substantially consists of a substrate member formed of a carbon fiber composite material and a metal surface layer formed on the surface of the substrate member. , The thermal conductivity in at least one direction is 300 W / m · K or more, and the metal surface layer is 2.0 kgf / mm ^{2 with} respect to the carbon fiber composite material.
A heat dissipation substrate comprising a base plating layer having the above adhesion strength. 2. The heat dissipation board according to claim 1, wherein the metal constituting the metal surface layer is Ti, V, Ni, Nb,
A heat dissipation board comprising at least one of Ag, Cu and Au. 3. The heat dissipation board according to claim 2, wherein the metal surface layer includes the undercoat plating layer, and the undercoat plating layer is at least one of Ni and Cu having a film thickness of 0.5 to 3 μm. A heat dissipation substrate, which is formed of the plating film of. 4. The heat dissipation substrate according to claim 2, wherein the metal surface layer includes the undercoat plating layer, and the undercoat plating layer has a thickness of 0.2 to 0.5 μm such as Ti, V, and N.
A heat dissipation substrate formed of at least one plating film of b. 5. A semiconductor device comprising a semiconductor element and a heat dissipation board on which the semiconductor element is mounted, wherein the heat dissipation board according to any one of claims 1 to 4 is used as the heat dissipation board. Semiconductor device. 6. A method of manufacturing a heat dissipation board on which a semiconductor element is mounted, wherein a carbon fiber composite material is prepared as a board member,
A method for manufacturing a heat dissipation substrate, comprising forming a metal surface layer after performing fluffing of the carbon fiber composite material. 7. The method for manufacturing a heat dissipation board according to claim 6, wherein the metal constituting the metal surface layer is Ti, V, N.
A method of manufacturing a heat dissipation substrate, which is characterized by comprising at least one of i, Nb, Ag, Cu, and Au. 8. The method of manufacturing a heat dissipation board according to claim 7, wherein a base plating layer is formed on the board member when the metal surface layer is formed. 9. The method for manufacturing a heat dissipation board according to claim 8, wherein the underlying plating layer is subjected to activation treatment in the coexistence of palladium chloride / stannous chloride, nickel chloride or chloride by secondary plating after oxidation chemical plating. By gradually increasing the current density to the substrate in the copper solution,
A method for manufacturing a heat dissipation substrate, which is formed from at least one of Ni and Cu while being controlled to 4.0 A / dm ² . 10. The method of manufacturing a heat dissipation board according to claim 9, wherein the thickness of the base plating layer is 0.5 to 3 μm. 11. The method for manufacturing a heat dissipation substrate according to claim 8, wherein the base plating layer is subjected to ion plating while heating the substrate member to form Ti, V and Nb.
A method for manufacturing a heat dissipation board, comprising forming at least one of the following. 12. The method for manufacturing a heat dissipation board according to claim 11, wherein the thickness of the undercoat plating layer is 0.2 to 0.5.
A method for manufacturing a heat dissipation substrate, wherein the heat dissipation substrate is μm.