Diamond / copper composite heat sink and its preparation method

Abstract

The present invention discloses a diamond / copper composite heat sink and a preparation method thereof, belonging to the technical field of heat dissipation materials. The composite heat sink of the present invention is composed of a self-supporting diamond film processed with fins, copper / strong carbide metal composite modification layers on the upper and lower surfaces, and a thick copper layer filled on the surface of the fins. The preparation method includes the following steps: first, fins are processed on the surface of the self-supporting diamond film, then a copper / strong carbide metal composite coating is prepared on the surface of the fins and the lower surface of the diamond film, and finally a thick copper layer is deposited to thicken the copper coating on the surface of the fins until the fin gaps are completely filled. The composite heat sink of the present invention has the advantages of good insulation performance, adjustable thermal conductivity and thermal expansion coefficient, high mechanical strength, simple preparation, and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of thermal management materials, and particularly relates to a diamond / copper composite heat sink and a preparation method thereof. Background Art

[0002] With the rise of the microelectronics industry, the continuous improvement of the integration degree of integrated circuits, and the continuous trend of miniaturization and high power, the heat generation of electronic components has increased rapidly, seriously affecting the operation and lifespan of devices. Therefore, it is imperative to develop high-thermal-conductivity thermal management materials that match the chips. The diamond / copper composite material combines diamond, which has the highest thermal conductivity (Thermal conductivity, i.e., TC) and a relatively low coefficient of thermal expansion (Coefficient of Thermal Expansion, i.e., CTE) in nature (TC = 2000 W·m -1 ·K -1 , CTE = 2.3×10 -6 K -1 ) and metal copper with good thermal conductivity (TC = 400 W·m -1 ·K -1 , CTE = 16.5×10 -6 K -1 ), and is currently the most promising thermal management material.

[0003] Currently, there are mainly two forms of diamond-copper composites. One is to composite in the form of particles. Generally, nanoscale or micron-scale diamond particles are mixed with copper powder, and diamond composites are prepared under high temperature and a certain pressure. In this composite method, the distribution of diamond is arbitrary and uncontrollable, and it cannot be accurately quantified. In addition, the improvement of its thermal conductivity has a limit, about 1 / 4 to 1 / 2 of the diamond bulk material. The other is to composite a self-supporting membrane with Cu. The in-plane thermal conductivity of the composite material prepared in this way along the diamond membrane can reach more than 80% of that of diamond. However, copper is a non-carbide-forming element, and it is generally difficult to obtain a high-strength bonding interface with diamond. In addition, diamond mainly uses phonons as heat carriers, and copper uses electrons as heat carriers. The heat transfer methods at the interface are different, which will generate a large interfacial thermal resistance, thus restricting the thermal properties of the diamond / copper composite material. When the existing interface modification method prepares an interfacial layer on the diamond surface to enhance its bonding strength with copper, strict requirements are imposed on the interfacial layer. If it is too thin, it is not enough to resist thermal stress, and if it is too thick, it will increase the interfacial thermal resistance. In addition, the surface of the diamond membrane needs to be ground and polished, and the operation is complex and restricted by the process. Summary of the Invention

[0004] The object of the present invention is to provide a diamond / copper composite heat sink with a new structure and preparation method to solve the problems that the bonding strength between the self-supporting diamond film and copper is poor and the interfacial thermal resistance is high, which restricts the improvement of its heat dissipation performance.

[0005] The present invention is realized by the following technical solutions:

[0006] A diamond / copper composite heat sink includes a self-supporting diamond film. A plurality of fins are formed on the top surface of the self-supporting diamond film and are arranged along its front-rear direction. The fins are in the shape of convex ridges, and grooves are formed between adjacent fins. The plurality of fins are evenly distributed and form a continuous tooth-like structure as a whole;

[0007] A copper / strong carbide metal composite modification layer is deposited on the surface of the tooth-like structure on the top surface of the self-supporting diamond film. A thick copper layer is deposited on the copper / strong carbide metal composite modification layer. The thick copper layer fills and seals the grooves between adjacent fins and continues to deposit to form a continuous planar copper coating;

[0008] A copper / strong carbide metal composite modification layer is deposited on the bottom surface of the self-supporting diamond film;

[0009] The copper / strong carbide metal composite modification layer is composed of a strong carbide metal transition layer located in the inner layer and a copper metal thin layer located in the outer layer.

[0010] As a preferred technical solution, the thickness of the diamond self-supporting film is not less than 500 μm.

[0011] As a preferred technical solution, the depth of the fins is 30-50% of the thickness of the diamond self-supporting film. The depth-width ratio of the fins is greater than 1:1, and the spacing between adjacent fins is less than the width of a single fin.

[0012] As a preferred technical solution, the shape of the fins is a cuboid or a cone.

[0013] As a preferred technical solution, the thickness of the strong carbide metal transition layer is 10-1000 nm, the thickness of the copper metal thin layer is 1-2 μm, and the strong carbide metal in the strong carbide metal transition layer is W, Mo, Ti, Cr, Zr.

[0014] Furthermore, the present invention also provides a preparation method for the above-mentioned diamond / copper composite heat sink, which specifically includes the following steps:

[0015] 1) Using the whole or part of the diamond self-supporting film as the heat sink substrate, and processing continuous tooth-like structure fins on its top surface by the laser method;

[0016] 2) Deposit a strong carbide metal transition layer and a thin copper metal layer successively on the surface of the tooth-like structure on the top surface of the self-supporting diamond film and on the bottom surface of the self-supporting diamond film to form a copper / strong carbide metal composite modification layer;

[0017] 3) Deposit a thick copper layer on the top surface of the self-supporting diamond film until the grooves between the fins are completely filled, and continue to deposit the thick copper layer until a continuous planar copper coating is formed;

[0018] 4) Remove the residual metal on the side of the diamond self-supporting film to ensure the insulation of the diamond self-supporting film, and finally obtain the diamond / copper composite heat sink.

[0019] As a preferred technical solution, the deposition method of the strong carbide metal transition layer includes magnetron sputtering, vacuum evaporation, and molten salt method.

[0020] As a preferred technical solution, the deposition method of the thin copper metal layer includes magnetron sputtering, vacuum evaporation, and electrodeposition.

[0021] As a preferred technical solution, the deposition method of the thick copper layer includes powder metallurgy, high temperature and high pressure method, and composite electrodeposition.

[0022] The technical principle of the diamond / copper composite heat sink of the present invention is as follows:

[0023] Diamond has excellent properties, but its surface energy is high, and its thermal expansion coefficient is also very different from that of other materials, making it difficult to achieve high-strength composite. In the present invention, fin textures are processed on the surface of the diamond self-supporting film, and its surface is successively modified with a strong carbide metal transition layer and a thin copper metal layer, and then a thick copper layer is continuously deposited until the fins are completely filled, and finally the diamond / copper composite heat sink is obtained. First, the processed fins can increase the contact area between the diamond and the coating to increase the bonding strength between the two; secondly, the intermediate strong carbide metal transition layer can enhance the bonding strength between the diamond and the transition layer by forming interfacial carbides, that is, chemical bonding, and at the same time change the connection between the diamond and other materials into a metal-to-metal connection, reducing the connection difficulty; the fins and the filled thick copper layer can also form a locking structure to improve the bonding strength through mechanical locking. The above-mentioned multi-faceted effects can solve the problem of poor bonding performance between the conventional diamond self-supporting film and copper, and ensure the bonding strength between the diamond and copper. A good bonding interface is also beneficial to reducing the interface thermal resistance and improving the thermal conductivity of the diamond / copper composite material.

[0024] At the same time, the present invention does not require polishing and grinding treatment of the diamond film, which can greatly reduce the production cycle. In addition, directly processing and modifying the unpolished diamond can also increase the contact area between the diamond and copper to a certain extent and increase the interface bonding strength.

[0025] The present invention can reasonably regulate the thicknesses of the diamond self-supporting film, the strong carbide metal transition layer, the copper metal thin layer, and the thick copper layer according to the heat dissipation requirements, thereby realizing the flexible regulation of the thermal conductivity and the coefficient of thermal expansion of the diamond / copper composite heat sink.

[0026] The diamond / copper composite heat sink of the present invention has the advantages of good insulation performance, adjustable thermal conductivity and coefficient of thermal expansion, high mechanical strength, simple preparation, and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings herein are used to provide further illustration of the present invention, and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation to the present invention.

[0028] Figure 1 It is a schematic diagram of the fins processed on the top and bottom surfaces of the diamond self-supporting film in the present invention.

[0029] Figure 2 It is a schematic diagram after depositing the strong carbide metal transition layer on the top and bottom surfaces of the diamond in the present invention.

[0030] Figure 3 It is a schematic diagram of depositing a copper metal thin layer on the strong carbide metal transition layer in the present invention.

[0031] Figure 4 It is a schematic diagram of the final structure of the diamond / copper composite heat sink of the present invention.

[0032] Figure 5 It is a macro micrograph of the fins processed on the top and bottom surfaces of the diamond self-supporting film in the present invention.

[0033] In the figure: 1 - self-supporting diamond film, 2 - strong carbide metal transition layer, 3 - copper metal thin layer, 4 - thick copper layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to enable those skilled in the art to better understand the present invention, the present invention will be further clearly and completely described below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other.

[0035] Embodiment 1

[0036] A diamond / copper composite heat sink includes a self-supporting diamond film 1. On the top surface of the self-supporting diamond film 1, a plurality of fins are formed along its front-rear direction. The fins are in the shape of convex ridges, and grooves are formed between adjacent fins. The plurality of fins are evenly distributed and form a continuous tooth-like structure as a whole; the size of the self-supporting diamond film 1 is 10×10×1.2 mm. The fins are in the shape of a cuboid, with a width of 0.3 mm and a depth of 400 µm, and the spacing between adjacent fins is 0.2 mm.

[0037] On the surface of the tooth-like structure on the top surface of the self-supporting diamond film 1, a copper / strong carbide metal composite modified layer is deposited. On the copper / strong carbide metal composite modified layer, a thick copper layer 4 is deposited. The thick copper layer 4 fills and seals the grooves between adjacent fins and continues to deposit to form a continuous planar copper coating.

[0038] On the bottom surface of the self-supporting diamond film 1, a copper / strong carbide metal composite modified layer is deposited.

[0039] The copper / strong carbide metal composite modified layer is composed of an inner strong carbide metal transition layer 2 with a thickness of 200 nm and an outer copper metal thin layer 3 with a thickness of 2 µm. The material of the strong carbide metal transition layer 2 is Ti.

[0040] The preparation method of the above diamond / copper composite heat sink specifically includes the following steps:

[0041] 1) Place the self-supporting diamond film 1 with a size of 10×10×1.2 mm under a laser marking machine with a rated power of 20 W. Set the fin width to 0.3 mm and the fin spacing to 0.2 mm, generate an array, and perform continuous processing and marking. Among them, the processing speed is 100 mm / s, the processing power is 90%, and the processing frequency is 20 KHz. When the number of processing times is 200 times, the fin depth is about 400 µm. The processing schematic diagram is as Figure 1 shown, and the macroscopic morphology of the sample is as Figure 5 shown.

[0042] 2) Use the DC magnetron sputtering method to deposit a Ti coating and a Cu coating on the top and bottom surfaces of the processed self-supporting diamond film 1 in sequence to obtain a copper / strong carbide metal composite modified layer, where the thickness of the Ti coating is controlled at 200 nm and the thickness of the Cu coating is controlled at 2 µm; the vacuum degree of the preparation chamber is better than 2.3×10 -4 Pa, the Ar gas pressure during sputtering is maintained at 0.85 - 0.98 Pa, and the purities of the Ti target, Cu target, and Ar gas are all 99.999%. The preparation schematic diagrams are as Figure 2 and Figure 3 shown.

[0043] 3) Place the self-supporting diamond film 1 on the cathode of the electrodeposition device. The anode material is a phosphor copper plate, and the electroplating solution is a commercial CuSO4 solution. Perform composite electrodeposition under magnetic stirring to prepare the thick copper layer 4. Maintain a constant current of 0.2 A throughout the electroplating process and continue electroplating until the fin gaps are filled, and a continuous planar copper coating is formed on its surface. The preparation schematic diagram is as shown in Figure 4 as shown.

[0044] 4) Use a grinding machine to remove the residual metal on the side of the self-supporting diamond film 1 after electroplating to ensure the insulation of the side of the heat sink. Finally, obtain a diamond / copper composite heat sink whose surface can be both soldered and etched with circuits. The composite schematic diagram is as shown in Figure 4 as shown.

[0045] Example 2

[0046] A diamond / copper composite heat sink includes a self-supporting diamond film 1. Multiple fins are formed on the top surface of the self-supporting diamond film 1 and are arranged along its front-rear direction. The fins are in the shape of convex ridges, and grooves are formed between adjacent fins. The multiple fins are evenly distributed and form a continuous tooth-like structure as a whole. The size of the self-supporting diamond film 1 is Φ12.5 × 0.7 mm. The shape of the fins is cuboid, with a depth of 0.3 mm and a spacing of 0.2 mm between adjacent fins.

[0047] A copper / strong carbide metal composite modification layer is deposited on the surface of the tooth-like structure on the top surface of the self-supporting diamond film 1. A thick copper layer 4 is deposited on the copper / strong carbide metal composite modification layer. The thick copper layer 4 fills and seals the grooves between adjacent fins and continues to deposit to form a continuous planar copper coating.

[0048] A copper / strong carbide metal composite modification layer is deposited on the bottom surface of the self-supporting diamond film 1.

[0049] The copper / strong carbide metal composite modification layer consists of a strong carbide metal transition layer 2 with a thickness of 200 nm located in the inner layer and a copper metal thin layer 3 with a thickness of 2 µm located in the outer layer. The material of the strong carbide metal transition layer 2 is Cr.

[0050] The preparation method of the above diamond / copper composite heat sink specifically includes the following steps:

[0051] 1) Select a self-supporting diamond film 1 with a size of Φ12.5 × 0.7 mm, design the shape of the fins as cuboids with a depth of 0.3 mm, and the fin spacing is 0.2 mm. Use a laser cutting machine to perform fin array engraving. The cutting power is 12W, and the cutting frequency is 7 Hz. The macroscopic morphology of the sample is as shown in Figure 5 as shown.

[0052] 2) A 200-nm-thick Cr coating was deposited on the top and bottom surfaces of the treated self-supporting diamond film 1 using magnetron sputtering. After that, a 2-μm-thick Cu coating was deposited by vacuum evaporation to obtain a self-supporting diamond film 1 modified with a copper / strong carbide metal composite modification layer.

[0053] 3) Copper powder with a particle size of 20 μm was mixed into the Au–Sn solder, evenly sprinkled on the top surface of the self-supporting diamond film 1 and filled into the grooves between the fins, and then continued to be sprinkled and flattened on the surface. The self-supporting diamond film 1 was placed in a vacuum annealing furnace at a holding temperature of 1350 °C for 10 min, and at the same time, a heavy object was placed above the self-supporting diamond film 1 to apply a downward pressure of 5 MPa to obtain a preliminary complete diamond / copper composite heat sink.

[0054] 4) The residual metal on the side surface of the self-supporting diamond film 1 was removed using a grinding machine to ensure the insulation of the side surface of the heat sink, and finally a diamond / copper composite heat sink with a surface that can be both soldered and etched with circuits was obtained. The composite schematic diagram is as Figure 4 shown.

[0055] Example 3

[0056] A diamond / copper composite heat sink includes a self-supporting diamond film 1. A plurality of fins are formed on the top surface of the self-supporting diamond film 1 and are arranged in the front-back direction thereof. The fins are in the shape of convex ribs, and grooves are formed between adjacent fins. The plurality of fins are evenly distributed and form a continuous tooth-like structure as a whole. The size of the self-supporting diamond film 1 is Φ50 × 0.9 mm. The shape of the fin is conical, its depth is 0.4 mm, and the distance between adjacent fins is 0.1 mm.

[0057] A copper / strong carbide metal composite modification layer is deposited on the tooth-like structure surface of the top surface of the self-supporting diamond film 1. A thick copper layer 4 is deposited on the copper / strong carbide metal composite modification layer. The thick copper layer 4 fills and seals the grooves between adjacent fins and continues to deposit to form a continuous planar copper coating.

[0058] A copper / strong carbide metal composite modification layer is deposited on the bottom surface of the self-supporting diamond film 1.

[0059] The copper / strong carbide metal composite modification layer is composed of an inner strong carbide metal transition layer 2 with a thickness of 200 nm and an outer copper metal thin layer 3 with a thickness of 2 μm. The material of the strong carbide metal transition layer 2 is W.

[0060] The preparation method of the above diamond / copper composite heat sink specifically includes the following steps:

[0061] 1) Select a self-supporting diamond film 1 with a size of Φ50 × 0.9 mm. Design the shape of the fins as a cone with a depth of 0.4 mm and a fin pitch of 0.1 mm. Use a laser marking machine with a rated power of 10 W to engrave the fin array, where the processing speed is 100 mm / s, the processing power is 90%, and the processing frequency is 20 Hz.

[0062] 2) Use the molten salt method to deposit a 200-nm-thick W coating on the top and bottom surfaces of the treated self-supporting diamond film 1. Then, use magnetron sputtering to deposit a 2-µm Cu coating to obtain a self-supporting diamond film 1 modified with a copper / strong carbide metal composite modification layer.

[0063] 3) Mix copper powder with a particle size of 50 µm into the indium solder, evenly sprinkle it on the top surface of the self-supporting diamond film 1 and fill the grooves between the fins, and continue to sprinkle and flatten the surface. Place the self-supporting diamond film 1 in a brazing furnace, keep the temperature at 1150 °C for 30 min, and at the same time place a heavy object above the self-supporting diamond film 1 to apply a downward pressure of 10 MPa to obtain a preliminary complete diamond / copper composite heat sink.

[0064] 4) Use a grinding machine to remove the residual metal on the side of the self-supporting diamond film 1 to ensure the insulation of the side of the heat sink, and finally obtain a diamond / copper composite heat sink whose surface can be both soldered and etched with circuits. The composite schematic diagram is as Figure 4 shown.

[0065] The above clearly and completely describes the technical solutions in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

Claims

1. A diamond / copper composite heat sink, characterized in that: It includes a self-supporting diamond film. Multiple fins arranged along its front-back direction are formed on the top surface of the self-supporting diamond film. The fins are in the shape of convex ridges, and grooves are formed between adjacent fins. The multiple fins are evenly distributed and form a continuous tooth-like structure as a whole; A copper / strong carbide metal composite modification layer is deposited on the surface of the tooth-like structure on the top surface of the self-supporting diamond film. A thick copper layer is deposited on the copper / strong carbide metal composite modification layer. The thick copper layer fills and seals the grooves between adjacent fins and continues to deposit to form a continuous planar copper coating; A copper / strong carbide metal composite modification layer is deposited on the bottom surface of the self-supporting diamond film; The copper / strong carbide metal composite modification layer is composed of a strong carbide metal transition layer located in the inner layer and a copper metal thin layer located in the outer layer; The thickness of the diamond self-supporting film is not less than 500 μm. The depth of the fins is 30-50% of the thickness of the diamond self-supporting film. The depth-width ratio of the fins is greater than 1:1, and the spacing between adjacent fins is less than the width of a single fin; The thickness of the strong carbide metal transition layer is 10-1000 nm, the thickness of the copper metal thin layer is 1-2 μm, and the strong carbide metal in the strong carbide metal transition layer is W, Mo, Ti, Cr, Zr.

2. The diamond / copper composite heat sink according to claim 1, characterized in that: The shape of the fins is a cuboid or a cone.

3. The preparation method of the diamond / copper composite heat sink according to claim 1, characterized in that, It includes the following steps: 1) Use the self-supporting diamond film as a whole or in part as the heat sink substrate, and use the laser method to process fins with a continuous tooth-like structure on its top surface; 2) Deposit a strong carbide metal transition layer and a copper metal thin layer on the surface of the tooth-like structure on the top surface of the self-supporting diamond film and on the bottom surface of the self-supporting diamond film in sequence to form a copper / strong carbide metal composite modification layer; 3) Deposit a thick copper layer on the top surface of the self-supporting diamond film until the grooves between the fins are completely filled, and continue to deposit the thick copper layer until a continuous planar copper coating is formed; 4) Remove the residual metal on the side surface of the self-supporting diamond film to ensure the insulation of the self-supporting diamond film, and finally obtain the diamond / copper composite heat sink.

4. The preparation method of the diamond / copper composite heat sink according to claim 3, characterized in that: The deposition methods of the strong carbide metal transition layer include magnetron sputtering method, vacuum evaporation method, and molten salt method.

5. The preparation method of the diamond / copper composite heat sink according to claim 3, characterized in that: The deposition methods of the copper metal thin layer include magnetron sputtering method, vacuum evaporation method, and electroplating method.

6. The preparation method of the diamond / copper composite heat sink according to claim 3, characterized in that: The deposition methods of the thick copper layer include powder metallurgy method, high temperature and high pressure method, and composite electroplating method.

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