Metallic group diamond heat spreader material for electronic chips and method of making same

Abstract

The application discloses a metal-based diamond heat spreading material for electronic chips and a preparation method thereof, and belongs to the technical field of electronic chip materials.The metal-based diamond heat spreading material comprises the following steps: placing diamond particles in a hydrochloric acid, sodium hydroxide, acetone and ethanol solution and performing ultrasonic cleaning; plating tungsten on the surface of the diamond particles; mixing the diamond particles, tungsten powder and tungsten trioxide powder by ball milling, placing the mixture in an alumina crucible, and performing annealing treatment in a vacuum tube furnace to obtain diamond particles with a tungsten plating layer; mixing the diamond particles with the tungsten plating layer and a metal matrix by ball milling, pouring the mixture into a graphite mold, placing the graphite mold in a spark plasma sintering device, and performing sintering under certain pressure, temperature and holding time, and cooling the sintered product in the furnace after sintering is completed.The application can improve the phonon mismatch between the diamond and the metal matrix, prepare a metal-based diamond composite material in a short time, and enable the composite material to have high thermal conductivity and a thermal expansion coefficient matching the material of the chip.

Description

Technical Field

[0001] This invention belongs to the field of composite material preparation, specifically relating to a metal-based diamond heat-absorbing material for electronic chips and its preparation method. Background Technology

[0002] With the continuous development of science and technology, the size of electronic chips is gradually shrinking, while their power and integration are constantly increasing, leading to a sharp increase in local heat flux density. Effectively managing this localized heat accumulation and preventing the formation of hot spots is crucial for ensuring the stable and efficient operation of electronic devices. Therefore, a key solution is to use heat amplification to transfer the heat generated by hot spots to a larger heat dissipation surface for dissipation. Thus, heat amplification materials need to have high thermal conductivity to ensure that heat can be quickly transferred to the heat dissipation system. Simultaneously, these materials should also have a coefficient of thermal expansion (4–10 ppm / K) that matches the chip material, allowing for close contact between the heat-generating chip and the heat amplification material, ensuring effective heat dissipation.

[0003] Traditional heat-dampening materials, such as Mo-Cu alloys and Si-Al alloys, often cannot simultaneously possess both high thermal conductivity and a suitable coefficient of thermal expansion, thus failing to meet the heat dissipation requirements of current high-power electronic devices. Metal-based diamond composites utilize the extremely high thermal conductivity of diamond, embedding diamond particles as reinforcements into a metal matrix. Through the complementary and synergistic effects of the properties between diamond and metal, these composites exhibit high thermal conductivity, high strength, and a suitable coefficient of thermal expansion, thus better meeting the heat dissipation needs of future electronic chips.

[0004] In metal-based diamond composites, diamond exhibits stable chemical properties and high thermal conductivity. However, the poor interfacial wettability between diamond and the metal matrix leads to poor interfacial bonding, reducing the overall thermal performance of the composite. Surface treatment of diamond can effectively enhance its interfacial bonding with the metal matrix. Commonly used methods for preparing metal-based diamond composites include pressure melting, vacuum hot pressing, and spark plasma sintering. Among these, spark plasma sintering offers rapid heating and low energy consumption, enabling the production of high-density metal-based diamond composites in a short time, which is beneficial for mass production. However, the thermal conductivity of metal-based diamond composites prepared using spark plasma sintering technology is currently relatively low. Therefore, to further improve the thermal conductivity of metal-based diamond composites and achieve a suitable coefficient of thermal expansion, new technologies are needed. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a metal-based diamond heat-absorbing material for electronic chips.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: the metal matrix diamond heat expansion material is obtained by mixing diamond particles containing tungsten coating with a metal matrix and then sintering by spark plasma.

[0009] As a preferred embodiment of the material described in this invention, the metal-based diamond heat-diffusing material has the following technical features:

[0010] (a) The thermal conductivity of the metal-based diamond heat-diffusing material at room temperature (25°C) is not less than 440 W / m·K;

[0011] (b) The coefficient of thermal expansion at room temperature (25°C) is not higher than 10 ppm / K;

[0012] (c) The temperature change rate of the heat source chip with stable power is not higher than 3% when it is heated.

[0013] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a metal-based diamond heat-absorbing material for electronic chips.

[0014] As a preferred embodiment of the preparation method described in this invention, the diamond particles are sequentially placed in hydrochloric acid, sodium hydroxide, acetone and ethanol solutions, ultrasonicated, washed with deionized water and dried for later use.

[0015] Diamond particles, tungsten powder and tungsten trioxide powder are ball-milled and mixed, then annealed to obtain diamond with tungsten coating. After being cleaned and dried with deionized water, the diamond is ready for use.

[0016] After cleaning and drying, diamond particles containing tungsten coating are ball-milled and mixed with a metal matrix, then poured into a mold for spark plasma sintering. After sintering, the mixture is cooled in the furnace to obtain a metal-based diamond heat-diffusing material.

[0017] In a preferred embodiment of the preparation method described in this invention, the diamond particles have a particle size of 50 μm to 300 μm, and the mass ratio of diamond particles, tungsten powder, and tungsten trioxide powder is 1:1:1 to 1:1.5:1.5.

[0018] In a preferred embodiment of the preparation method described in this invention, the volume fractions of hydrochloric acid, sodium hydroxide, acetone, and ethanol are 20%.

[0019] In a preferred embodiment of the preparation method described in this invention, the drying temperature is 120°C and the drying time is 4 hours.

[0020] As a preferred embodiment of the preparation method described in this invention, the ball milling process is carried out without grinding media, the ball milling speed is 100 r / min, and the time is 12 h.

[0021] In a preferred embodiment of the preparation method described in this invention, the metal matrix includes one of copper, aluminum, magnesium, silver or tungsten; the volume ratio of diamond particles containing tungsten coating to the metal matrix is ​​1:1 to 1:2.

[0022] In a preferred embodiment of the preparation method described in this invention, the annealing process is carried out in a nitrogen-hydrogen mixture atmosphere at 1000℃ to 1200℃ for 0.5 to 1.5 hours.

[0023] As a preferred embodiment of the preparation method described in this invention, in the discharge plasma sintering, 2 to 3 sheets of graphite paper are used to place the powder at the graphite pressure head. The discharge plasma sintering preparation pressure is 30 MPa to 50 MPa, the heating rate is 100 °C / min, the sintering temperature is 700 °C to 1200 °C, and the holding time is 5 to 10 min.

[0024] Beneficial effects of this invention:

[0025] (1) This invention effectively solves the problem of poor interfacial bonding between the metal matrix and diamond in the preparation of metal-based diamond composite materials. By simply mixing and annealing the powder, a tungsten layer is coated on the surface of the diamond particles, which improves the wettability between the diamond and the metal matrix and strengthens the interfacial bonding. At the same time, the tungsten layer also improves the phonon mismatch between the diamond and the metal matrix, reduces phonon scattering at the interface, and improves the overall thermal conductivity of the composite material. By spark plasma sintering, under appropriate sintering temperature and holding time, the diamond forms an effective heat transfer network, which improves the thermal conductivity of the metal-based diamond composite material.

[0026] (2) The present invention can prepare metal-based diamond composite material with high thermal conductivity and thermal expansion coefficient matching chip material in a short time, which can be used as heat dissipation material for electronic chips. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0028] Figure 1 This is a scanning electron microscope image of diamond particles before the tungsten coating of the present invention.

[0029] Figure 2 This is a scanning electron microscope image of diamond particles after tungsten coating according to the present invention.

[0030] Figure 3 This is a schematic diagram of the discharge plasma sintering process of the present invention.

[0031] Figure 4 This is the temperature change curve over time in the heat expansion test of Embodiment 1 of the present invention.

[0032] Figure 5 This is the temperature versus power curve in the heat expansion test of Embodiment 1 of the present invention.

[0033] Figure 6 The thermal expansion coefficient curve of Embodiment 1 of the present invention.

[0034] Figure 7 This is a graph showing the coefficient of thermal expansion of Comparative Example 1 of the present invention. Detailed Implementation

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0038] Unless otherwise specified, all raw materials used in this invention are commercially available products.

[0039] Example 1

[0040] This invention provides a method for preparing a metal-based diamond heat-absorbing material for electronic chips:

[0041] (1) Pretreatment of diamond particles:

[0042] Diamond particles with a diameter of 300 μm were subjected to ultrasonic cleaning for 30 minutes in a 20 vol% solution of hydrochloric acid, sodium hydroxide, acetone, and ethanol to roughen the surface of the diamond particles and remove adhering oil and metal oxides. The diamond particles were then washed with deionized water and dried at 120°C for 4 hours before use. Figure 1 (As shown).

[0043] (2) Tungsten plating on the surface of diamond particles:

[0044] Diamond particles, tungsten powder, and tungsten trioxide powder were ball-milled at a mass ratio of 1:1.5:1.5. No grinding media were used during the ball milling process. The milling speed was 100 r / min for 12 hours. The mixed powder was then placed in an alumina crucible and annealed in a vacuum tube furnace at 1200℃ for 0.5 hours in a nitrogen-hydrogen mixture atmosphere. This annealing process coated the diamond particles with a tungsten layer. The diamond particles with the tungsten coating were then washed with deionized water and dried at 120℃ for 4 hours before use. Figure 2 (as shown);

[0045] (3) Preparation of metal-based diamond composite materials:

[0046] The cleaned diamond particles with tungsten coating prepared in step (2) were ball-milled with copper powder at a volume ratio of 1:1. The volume fraction of diamond in the composite material was 50%. No grinding media was used during the ball milling process. The ball milling speed was 100 r / min for 12 hours. The mixed particle powder was poured into a graphite mold and placed in a spark plasma sintering device (Labox-650). Two to three sheets of graphite paper were used to prevent powder leakage at the graphite pressure head. Then spark plasma sintering was performed (e.g., Figure 3 As shown, the spark plasma sintering method uses controllable pulsed current and axial pressure to purify and activate material particles and powders, generating a large amount of Joule heat at the contact points of the particles and powders through instantaneous high-frequency pulses for sintering. The preparation pressure is 40 MPa, the sintering temperature is 1000℃, the holding time is 10 min, and the material is cooled in the furnace after sintering to obtain a copper-based diamond composite material.

[0047] Comparative Example 1

[0048] The difference from Example 1 is that aluminum powder is used in step (3).

[0049] Example 2

[0050] The thermal properties of the metal-based diamond composite material prepared in Example 1 were evaluated:

[0051] 1cm 2 The heat-generating chip is placed in the middle of a copper-based diamond composite heat-diffusing substrate, with a water-cooled plate acting as the cold source to remove excess heat from the system. The temperatures of the heat source (heat-generating chip), the upper surface and surrounding area of ​​the heat-diffusing substrate, and the center and surrounding area of ​​the bottom surface of the substrate in contact with the water-cooled plate are measured. A power of 10W is applied to the chip every 10 minutes until the heat source temperature first exceeds the safe and stable operating temperature (100℃) of the electronic chip, at which point the test is stopped.

[0052] Compared to aluminum alloy heat spreaders, the copper-based diamond composite heat spreader substrate exhibits more stable heat source temperature during the heat spread process, indicating that its higher thermal conductivity allows for rapid expansion of excess heat from the heat source onto its larger heat dissipation area. (A 1cm sample is applied every 10 minutes.) 2 After applying 10W of power to the chip, the temperature of the copper-based diamond composite heat-dissipating substrate remained relatively stable, with a temperature change rate not exceeding 3% (e.g., Figure 4 (As shown). Meanwhile, while ensuring the safe and stable operation of the chip, the copper-based diamond composite heat spreader can support a chip operating power of up to 110W, 40W higher than the aluminum alloy heat spreader. When the heat-generating chip's operating power is 70W, the heat flux density is 70W / cm³. 2 At that time, the heat source temperature of the copper-based diamond composite heat spreader was 31.5℃ lower than that of the aluminum alloy heat spreader (e.g., Figure 5 (As shown).

[0053] The thermal conductivity of the copper-based diamond composite material in Example 1, measured using a laser flash thermal conductivity meter (LFA-467), was 662 W / (m·K). The coefficient of thermal expansion of the copper-based diamond composite material, measured using a thermal expansion meter (TMA402F3), was 162 W / (m·K). Figure 6 (As shown). The thermal conductivity of the aluminum-based diamond composite material in Example 2 was measured to be 440 W / (m·K) using a laser flash thermal conductivity meter (LFA-467). The coefficient of thermal expansion of the aluminum-based diamond composite material was measured using a thermal expansion meter (TMA402F3). Figure 7 (As shown).

[0054] Table 1

[0055]

[0056]

[0057] Comparative Example 2

[0058] In CN114985707B, (1) the aluminum diamond composite material prepared by hot pressing is cut into sheets using a laser cutting machine, the oxide layer on each surface is removed, and the surface is roughened and then washed; degreasing, pickling, water washing, and drying are performed; (2) the zinc melt temperature is 430℃, and the sheet is immersed in the zinc melt for 10s and then taken out, and the thickness of the zinc layer is about 5μm; (3) the obtained aluminum diamond sheet blank is fixed in the IGBT substrate die casting mold by aluminum support columns, and the whole is preheated to 350℃; (4) the ZL101A aluminum liquid is placed in the crucible of the pressure casting machine, heated to 700℃ and then squeezed into the mold cavity, held under pressure for 120s and then demolded to obtain an aluminum-clad aluminum diamond IGBT substrate blank; (5) the blank gating and riser are removed, the burrs are removed by grinding, and the holes are machined; after holding at 175℃ for 3h, the aluminum-clad aluminum diamond IGBT substrate is obtained.

[0059] Comparative Example 3

[0060] The difference from Example 1 is that step (3) does not use spark plasma sintering, but uses pressureless melting infiltration. In the pressureless melting infiltration method, the metal matrix is ​​heated above its melting point, and the molten metal spontaneously infiltrates into the diamond particles of the reinforcement under pressureless conditions.

[0061] Comparative Example 4

[0062] The difference from Example 1 is that in step (2), the mass ratio of diamond particles, tungsten powder and tungsten trioxide powder is 1:0.5:0.5.

[0063] Comparative Example 5

[0064] The difference from Example 1 is that in step (2), the mass ratio of diamond particles, tungsten powder and tungsten trioxide powder is 1:0.5:2.

[0065] Comparative Example 6

[0066] The difference from Example 1 is that tungsten powder is not added in step (2), while all other conditions are the same as in Example 1.

[0067] Comparative Example 7

[0068] The difference from Example 1 is that tungsten trioxide powder is not added in step (2), while all other conditions are the same as in Example 1.

[0069] Comparative Example 8

[0070] The difference from Example 1 is that in step (2), the mass ratio of diamond particles, tungsten powder and tungsten trioxide powder is 1:2:2, and all other conditions are the same as in Example 1.

[0071] Comparative Example 9

[0072] The difference from Example 1 is that in step (2), the mass ratio of diamond particles, tungsten powder and tungsten trioxide powder is 1:2:0.5, and all other conditions are the same as in Example 1.

[0073] Comparative Example 10

[0074] The difference from Example 1 is that the diamond particle size in step (1) is 30 μm.

[0075] Comparative Example 11

[0076] The difference from Example 1 is that the diamond particles in step (1) have a particle size of 400 μm.

[0077] Comparative Example 12

[0078] The difference from Example 1 is that a single layer of graphite paper is placed at the graphite indenter in step (3).

[0079] Comparative Example 13

[0080] The difference from Example 1 is that the volume fraction of diamond in the composite material in step (3) is 20%.

[0081] Comparative Example 14

[0082] The difference from Example 1 is that the volume fraction of diamond in the composite material in step (3) is 70%.

[0083] Table 2

[0084] Comparative Example 3 220 12.3 Comparative Example 4 506 7.4 Comparative Example 5 491 7.6 Comparative Example 6 333 11.2 Comparative Example 7 204 12.5 Comparative Example 8 447 9.8 Comparative Example 9 483 9.1 Comparative Example 10 510 6.9 Comparative Example 11 329 14.1 Comparative Example 12 552 6.3 Comparative Example 13 360 10.7 Comparative Example 14 402 4.1

[0085] In Comparative Example 2, the zinc plating process on the diamond surface involved placing it in a zinc solution. Since diamond and zinc cannot chemically react, this process did not improve the lack of wetting between diamond and the metal, resulting in poor zinc plating performance. Data from Comparative Examples 1, 3-14 show that the metal-based diamond composite material prepared by the method in Example 1 possesses the highest thermal conductivity and the most suitable coefficient of thermal expansion, making it suitable as a heat-dissipating material for future electronic chips and effectively reducing the chip's heat source temperature.

[0086] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a metal-based diamond heat-diffusing material for electronic chips, characterized in that: (1) Pretreatment of diamond particles: Diamond particles with a diameter of 300 μm were sequentially placed in a solution of 20 vol% hydrochloric acid, sodium hydroxide, acetone, and ethanol. The diamond particles were ultrasonically cleaned in the liquid for 30 minutes to roughen the surface of the diamond particles and remove the attached oil and metal oxides; the diamond particles were then washed with deionized water and dried at 120°C for 4 hours before use. (2) Tungsten plating on the surface of diamond particles: Diamond particles, tungsten powder, and tungsten trioxide powder were ball-milled at a mass ratio of 1:1.5:1.5 without grinding media at a speed of 100 r / min for 12 hours. The mixed powder was then placed in an alumina crucible and annealed in a vacuum tube furnace at 1200℃ for 0.5 hours under a nitrogen-hydrogen mixture atmosphere to coat the diamond particles with a tungsten layer. The diamond particles with the tungsten coating were then washed with deionized water and dried at 120℃ for 4 hours before use. (3) Preparation of metal-based diamond composite materials: The cleaned diamond particles with tungsten coating prepared in step (2) were ball-milled with copper powder at a volume ratio of 1:

1. The volume fraction of diamond in the composite material was 50%. No grinding media were used during the ball milling process, and the ball milling speed was 100 r / min. For 12 hours, the mixed granular powder was poured into a graphite mold, which was then placed in a spark plasma sintering (SPS) apparatus. Two to three sheets of graphite paper were used to prevent powder leakage at the graphite pressure head. SPS was then performed. The SPS method uses controllable pulsed current and axial pressure to purify and activate the material particles and powder. A large amount of Joule heat is generated at the contact points between the particles and powder using instantaneous high-frequency pulses for sintering. The preparation pressure was 40 MPa, the sintering temperature was 1000℃, and the holding time was 10 min. After sintering, the material was cooled in the furnace to obtain a copper-based diamond composite material.

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