Method for pulse current assisted preparation of graphite / aluminum laminated composite and composite substrate

Abstract

The application discloses a method for preparing a graphite / aluminum layered composite material by means of pulse current, and relates to the technical field of composite materials, in particular to a method for preparing a graphite / aluminum layered composite material by means of pulse current.The method comprises the following steps: pretreating an aluminum alloy to obtain an aluminum alloy piece; pretreating graphite to obtain a graphite piece; stacking the aluminum alloy piece, the graphite piece and the aluminum alloy piece in sequence to form a connecting assembly; placing the connecting assembly in the middle of electrodes of a pulse current diffusion connecting device; connecting the connecting assembly by applying pressure and pulse current under a protective atmosphere; and heating and cooling to room temperature to obtain a composite substrate.The method directly heats the connecting assembly by means of pulse current, can efficiently utilize energy, and maximally reduces energy loss; and by means of the field-induced effects of joule heat, electromigration and electric plasticity of the pulse current, element diffusion can be accelerated, and the process time required for bonding can be reduced, so that time cost is reduced.The application further discloses a composite substrate, which comprises two aluminum alloy pieces and one graphite piece.

Description

Technical Field

[0001] This invention relates to the field of graphite / aluminum layered composite materials technology, specifically to a method for pulsed current-assisted preparation of graphite / aluminum layered composite materials and a composite substrate. Background Technology

[0002] With the continuous development of electronic technology, various electronic devices are constantly evolving towards higher integration, miniaturization, and higher power, leading to a continuous increase in their heat flux density. To prevent device overheating and failure, heat needs to be transferred and dissipated in a timely manner, which places higher demands on the heat dissipation capacity of packaging materials. However, existing packaging materials, such as aluminum, copper, and aluminum silicon carbide, have low thermal conductivity and cannot meet the heat dissipation requirements of densely packed electronic devices.

[0003] High thermal conductivity graphite, such as graphene films and highly oriented pyrolytic graphite, possesses excellent in-plane thermal conductivity, enabling rapid heat transfer. However, graphite itself has poor mechanical strength, and detached graphite powder particles can easily cause short circuits in electronic devices. Therefore, it needs to be encapsulated with lightweight, high-strength aluminum alloys to form graphite / aluminum layered composite materials to meet reliability requirements. Existing preparation methods often employ vacuum hot pressing sintering, liquid phase pressure infiltration, and vacuum diffusion welding; however, these methods consume significant energy, are time-consuming, and have high equipment costs. Summary of the Invention

[0004] Therefore, the present invention provides a method for preparing graphite / aluminum layered composite materials and a composite substrate with pulsed current assistance, so as to reduce energy consumption, time and equipment costs in the preparation process of graphite / aluminum layered composite materials.

[0005] This invention proposes a method for pulsed current-assisted preparation of graphite / aluminum layered composite materials, comprising:

[0006] Pre-treating aluminum alloys to obtain aluminum alloy parts;

[0007] Pre-process graphite to obtain graphite parts;

[0008] The aluminum alloy parts, the graphite parts, and the aluminum alloy parts are stacked in sequence to form a connecting assembly. The connecting assembly is placed in the middle of the electrodes of the pulse current diffusion connecting device. Pressure and pulse current are applied to the connecting assembly under a protective atmosphere to connect them. After heating is completed and cooled to room temperature, a composite substrate is obtained.

[0009] The present invention discloses a pulsed current-assisted method for preparing graphite / aluminum layered composite materials. Utilizing the Joule heating and electromigration effects of the pulsed current, bonding between graphite and aluminum alloys can be achieved, thereby creating a composite substrate. Traditional composite substrate preparation methods include vacuum hot pressing, vacuum diffusion welding, or liquid-phase pressure infiltration, typically employing furnace heating and radiative heat transfer to the connecting components via a heating element. This method is inefficient, energy-intensive, time-consuming, and costly. The method described in this invention, however, directly heats the connecting components with a pulsed current, efficiently utilizing energy and minimizing energy loss. Furthermore, the Joule heating, electromigration, and electroplastic effects of the pulsed current accelerate element diffusion, reducing the bonding time and thus lowering time costs.

[0010] In some embodiments, the step of pretreating the aluminum alloy to obtain the aluminum alloy part includes:

[0011] The aluminum alloy surface was progressively sanded and polished using 800#, 1200#, and 2000# sandpaper.

[0012] The polished aluminum alloy is immersed in a diethylene glycol dimethyl ether solution for cleaning to obtain an aluminum alloy part.

[0013] In some embodiments, the step of pre-treating graphite to obtain a graphite part includes:

[0014] The graphite is ultrasonically cleaned to remove surface contaminants.

[0015] In some embodiments, the method further includes:

[0016] The cleaned graphite surface is then coated.

[0017] In some embodiments, the coating method is any one of magnetron sputtering, electroless plating, vacuum evaporation and electroplating, the coating type is any one of Ti, Zr, Mo, Si and W, and the thickness of the coating ranges from 0.1 μm to 10 μm.

[0018] In some embodiments, the aluminum alloy is industrial pure aluminum and any one of various aluminum alloy systems, and the graphite is any one of hot isostatic graphite, pyrolytic graphite, and graphene film.

[0019] In some embodiments, the heating method is pulsed current heating, wherein the pulse frequency of the pulsed current is 100Hz-10000Hz, the pulse width is 1μs-999ms, and the duty cycle is 1%-100%.

[0020] In some embodiments, the heating temperature range is 450℃-650℃, the holding time is 1min-120min, and the protective atmosphere is a vacuum atmosphere or an inert gas atmosphere, wherein the inert gas is any one of helium, argon or nitrogen.

[0021] In some embodiments, the pressure ranges from 1 MPa to 30 MPa, the heating rate is from 10 °C / min to 500 °C / min, and the cooling rate is from 5 °C / min to 200 °C / min.

[0022] The present invention also proposes a composite substrate comprising two aluminum alloy parts and a graphite part, wherein the graphite part is fixedly connected between the two aluminum alloy parts.

[0023] The composite substrate of this invention is manufactured by the method described above. This method utilizes the Joule heating and electromigration field effects of pulsed current to achieve bonding between graphite and aluminum alloy, thereby creating a composite substrate. Traditional composite substrate preparation methods include vacuum hot pressing sintering, vacuum diffusion welding, or liquid phase pressure infiltration. These methods generally employ furnace heating, using a heating belt to radiate heat to the connecting components. This approach is inefficient, energy-intensive, time-consuming, and costly. In contrast, the method described in this invention uses pulsed current to directly heat the connecting components, achieving efficient energy utilization and minimizing energy loss. Furthermore, the Joule heating, electromigration, and electroplastic field effects of pulsed current accelerate element diffusion, reducing the bonding time and thus lowering time costs. Attached Figure Description

[0024] Figure 1 This is a flowchart of a method for preparing graphite / aluminum layered composite materials with pulsed current assistance according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the structure of graphite / aluminum layered composite material prepared with pulsed current assistance.

[0026] Figure 3 yes Figure 1 The detailed steps of step S10 are shown in the diagram.

[0027] Figure 4 This is a schematic diagram of the structure of a composite substrate proposed in another embodiment of the present invention.

[0028] Figure 5 This is a scanning electron microscope image of the graphene / aluminum interface in one embodiment of the present invention. Detailed Implementation

[0029] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0030] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0031] Please see Figure 1 and Figure 2 This invention proposes a method for pulsed current-assisted preparation of graphite 20 / aluminum layered composite materials, comprising:

[0032] S10, pre-treated aluminum alloy 10, to obtain aluminum alloy parts.

[0033] Please see below. Figure 3 The step of pre-treating the aluminum alloy 10 to obtain the aluminum alloy part includes:

[0034] S11, using 800#, 1200#, and 2000# sandpaper to grind and polish the surface of aluminum alloy 10 step by step;

[0035] S12, the polished aluminum alloy 10 is immersed in diethylene glycol dimethyl ether solution for cleaning to obtain aluminum alloy parts.

[0036] Among them, aluminum alloy 10 can be industrial pure aluminum or any one of various aluminum alloys 10.

[0037] S20, pre-process graphite 20 to obtain graphite parts.

[0038] Among them, graphite 20 is any one of hot isostatic graphite 20, pyrolytic graphite 20, and graphene film 20.

[0039] In some embodiments, the step of pre-treating the graphite 20 to obtain a graphite part includes:

[0040] Graphite 20 was ultrasonically cleaned to remove surface contaminants.

[0041] In some embodiments, the method further includes:

[0042] The cleaned graphite 20 surface is coated.

[0043] In some embodiments, the coating method is any one of magnetron sputtering, electroless plating, vacuum evaporation, and electroplating; the coating type is any one of Ti, Zr, Mo, Si, and W; and the coating thickness ranges from 0.1 μm to 10 μm. When the coating thickness meets the above range, the elements in the coating can react sufficiently with graphite 20 to form a continuous carbide layer, thereby achieving a reinforcing effect. However, when the coating thickness is outside the above range, on the one hand, the coating is prone to peeling off, and on the other hand, it will increase the interfacial thermal resistance.

[0044] S30, aluminum alloy parts, graphite parts and aluminum alloy parts are stacked in sequence to form a connecting assembly 100. The connecting assembly 100 is placed between the electrodes 210 of the pulse current diffusion connecting device 200. Pressure and pulse current are applied to the connecting assembly 100 under a protective atmosphere to connect them. After heating is completed and cooled to room temperature, a composite substrate is obtained.

[0045] In this embodiment, the aluminum alloy parts, graphite parts, and aluminum alloy parts are all layered structures.

[0046] The heating method is pulsed current heating, with a pulse frequency of 100Hz-10000Hz, a pulse width of 1μs-999ms, and a duty cycle of 1%-100%.

[0047] The heating temperature range is 450℃-650℃, and the holding time is 1min-120min. The temperature during the heating process is monitored by a thermocouple, infrared thermometer, or thermal imager. The reaction between heterogeneous materials requires a certain temperature and time; if the temperature is too low, the reaction driving force will be insufficient. Furthermore, aluminum's melting point is 660℃, and setting a maximum temperature of 650℃ can prevent aluminum from melting. Since the required time is inversely proportional to the temperature—the higher the temperature, the shorter the required time—a lower limit of 1min is set to ensure a sufficient reaction time. Conversely, excessively long times can lead to an overly thick reaction layer or coarse grains; therefore, an upper limit of 120min is set.

[0048] The protective atmosphere is either a vacuum atmosphere or an inert gas atmosphere, and the inert gas is any one of helium, argon or nitrogen.

[0049] The pressure range is 1 MPa to 30 MPa. A certain pressure is required to ensure close contact between the materials and form a complete conductive circuit. However, the yield strength of aluminum alloy 10 decreases as the temperature increases. Therefore, the upper limit of the pressure is set at 30 MPa to prevent excessive deformation.

[0050] The heating rate ranges from 10℃ / min to 500℃ / min, while the cooling rate ranges from 5℃ / min to 200℃ / min. Since the pulsed current directly acts on the connecting component 100, the heating rate can reach very high values. However, to prevent temperature overshoot and temperatures exceeding the melting point of aluminum, an upper limit of 500℃ / min is set. Reducing the heating rate can prevent this problem, but to shorten the heating time, a heating rate of 50℃ / min is set. Because the heat source in this method is the Joule heating effect of the pulsed current, the cooling rate of the connecting component 100 is extremely rapid after the current is turned off. However, to prevent excessive stress, the upper limit of the cooling rate is controlled at 200℃ / min. Reducing the cooling rate can mitigate this problem, but to shorten the cooling time, a lower limit of 50℃ / min is set.

[0051] The present invention discloses a method for preparing graphite 20 / aluminum layered composite materials with pulsed current assistance. This method utilizes the Joule heating and electromigration effects of the pulsed current to achieve bonding between graphite 20 and aluminum alloy 10, thereby creating a composite substrate. Traditional methods for preparing composite substrates include vacuum hot pressing, vacuum diffusion welding, or liquid-phase pressure infiltration, typically employing furnace heating. Heat is transferred to the connecting component 100 via radiation from a heating element, resulting in low efficiency, high energy consumption, long processing time, and high manufacturing costs. In contrast, the method of this invention directly heats the connecting component 100 with pulsed current, achieving efficient energy utilization and minimizing energy loss. Furthermore, the Joule heating, electromigration, and electroplastic effects of the pulsed current accelerate element diffusion, reducing the bonding time and thus lowering time costs.

[0052] Please see Figure 4 The present invention also proposes a composite substrate 300, comprising two aluminum alloy parts 310 and a graphite part 320, wherein the graphite part 320 is fixedly connected between the two aluminum alloy parts 310.

[0053] The composite substrate 300 of the present invention is manufactured by the method described above. This method utilizes the Joule heating and electromigration effects of pulsed current to achieve bonding between graphite and aluminum alloy, thereby producing the composite substrate 300. Traditional composite substrate fabrication methods include vacuum hot pressing sintering, vacuum diffusion welding, or liquid-phase pressure infiltration. These methods typically employ furnace heating, using a heating element to radiate heat to the connecting components. This approach is inefficient, energy-intensive, time-consuming, and costly. In contrast, the method of the present invention utilizes pulsed current to directly heat the connecting components, achieving efficient energy utilization and minimizing energy loss. Furthermore, the Joule heating, electromigration, and electroplastic effects of the pulsed current accelerate element diffusion, reducing the bonding time and thus lowering time costs.

[0054] The technical solution of the present invention is not limited to the specific embodiments exemplified below, but also includes any combination of the specific embodiments.

[0055] Example 1

[0056] Example 1 of this invention proposes a method for pulsed current-assisted preparation of graphite / aluminum layered composite materials, comprising the following steps:

[0057] Step 1: Use 800#, 1200#, and 2000# sandpaper to grind and polish the aluminum alloy surface step by step. Then, immerse the polished aluminum alloy in diethylene glycol dimethyl ether solution for cleaning to obtain the aluminum alloy parts.

[0058] Step 2: Perform ultrasonic cleaning on the pyrolytic graphite for 5 minutes to remove surface stains, and then air dry to obtain graphite parts;

[0059] Step 3: Stack aluminum alloy parts, graphite parts, and aluminum alloy parts in sequence to form a connecting assembly. Place the connecting assembly in the middle of the electrodes of the pulse current diffusion connecting device, introduce argon gas as a protective gas, apply an axial pressure of 10 MPa to the connecting assembly, and then apply a pulse current with a frequency of 1000 Hz and a pulse width of 1 ms. Monitor the temperature of the connecting assembly using an infrared thermometer. Then control the heating rate to rise to 550°C at 100°C / min and hold for 20 min. After that, control the cooling rate to cool to 200°C at 50°C / min. Finally, turn off the pulse current and cool to room temperature to obtain the composite substrate.

[0060] Example 2

[0061] This embodiment of a method for pulsed current-assisted preparation of graphite / aluminum layered composite materials includes the following steps:

[0062] Step 1: Use 800#, 1200#, and 2000# sandpaper to grind and polish the aluminum alloy surface step by step. Then, immerse the polished aluminum alloy in diethylene glycol dimethyl ether solution for cleaning to obtain the aluminum alloy parts.

[0063] Step 2: The graphene film is ultrasonically cleaned for 5 minutes to remove surface stains and then air-dried; then a 1 μm Ti film is deposited on the graphene surface by magnetron sputtering to obtain a graphite part.

[0064] Step 3: Stack aluminum alloy parts, graphite parts, and aluminum alloy parts in sequence to form a connecting assembly. Place the connecting assembly in the middle of the electrodes of the pulsed current diffusion connecting device, introduce argon gas as a protective gas, apply an axial pressure of 10 MPa to the connecting assembly, and then apply a pulsed current with a frequency of 10000 Hz and a pulse width of 0.1 ms. Monitor the temperature of the connecting assembly using an infrared thermometer. Then, control the heating rate to increase the temperature to 500℃ at 100℃ / min, hold for 40 min, and then control the cooling rate to decrease the temperature to 200℃ at 100℃ / min. Finally, turn off the pulsed current and cool to room temperature to obtain the composite substrate. The scanning electron microscope image of the graphene / aluminum interface in the composite substrate is shown below. Figure 5 As shown.

[0065] Example 3

[0066] This embodiment of a method for pulsed current-assisted preparation of graphite / aluminum layered composite materials includes the following steps:

[0067] Step 1: Use 800#, 1200#, and 2000# sandpaper to grind and polish the aluminum alloy surface step by step. Then, immerse the polished aluminum alloy in diethylene glycol dimethyl ether solution for cleaning to obtain the aluminum alloy parts.

[0068] Step 2: Perform ultrasonic cleaning on the hot isostatic graphite for 5 minutes to remove surface stains and air dry; then use magnetron sputtering to deposit a 3μm Zr film on the surface of the hot isostatic graphite to obtain a graphite part.

[0069] Step 3: Stack aluminum alloy parts, graphite parts, and aluminum alloy parts in sequence to form a connecting assembly. Place the connecting assembly in the middle of the electrodes of the pulse current diffusion connecting device, introduce nitrogen gas as a protective gas, apply an axial pressure of 10 MPa to the connecting assembly, and then apply a pulse current with a frequency of 10000 Hz and a pulse width of 0.1 ms. Monitor the temperature of the connecting assembly using an infrared thermometer. Then control the heating rate to rise to 500℃ at 100℃ / min and hold for 40 min. After that, control the cooling rate to cool down to 200℃ at 100℃ / min. Finally, turn off the pulse current and cool to room temperature to obtain the composite substrate.

[0070] Example 4:

[0071] This embodiment of a method for pulsed current-assisted preparation of graphite / aluminum layered composite materials includes the following steps:

[0072] Step 1: Use 800#, 1200#, and 2000# sandpaper to grind and polish the aluminum alloy surface step by step. Then, immerse the polished aluminum alloy in diethylene glycol dimethyl ether solution for cleaning to obtain the aluminum alloy parts.

[0073] Step 2: The graphene block is ultrasonically cleaned for 5 minutes to remove surface stains and then air-dried; then a 1-micron Ti film is deposited on the surface of the graphene block by vacuum evaporation to obtain a graphite part.

[0074] Step 3: Stack aluminum alloy parts, graphite parts, and aluminum alloy parts in sequence to form a connecting assembly. Place the connecting assembly in the middle of the electrodes of the pulse current diffusion connecting device, introduce argon gas as a protective gas, apply an axial pressure of 8MPa to the connecting assembly, and then apply a pulse current with a frequency of 10000Hz and a pulse width of 0.1ms. Monitor the temperature of the connecting assembly using an infrared thermometer. Then control the heating rate to rise to 530℃ at 100℃ / min and hold for 30min. After that, control the cooling rate to cool down to 200℃ at 100℃ / min. Finally, turn off the pulse current and cool to room temperature to obtain the composite substrate.

[0075] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be embraced within this application.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application 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 this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A method for preparing graphite / aluminum layered composite materials with pulsed current assistance, characterized in that, include: Pre-treating aluminum alloy to obtain aluminum alloy parts, wherein the aluminum alloy is any one of various aluminum alloy systems; Pre-treated graphite is subjected to a coating treatment on the cleaned graphite surface. The thickness of the coating ranges from 0.1 μm to 10 μm. The coating method is any one of magnetron sputtering, chemical plating, vacuum evaporation, and electroplating. The coating type is any one of Ti, Zr, Mo, Si, and W to obtain a graphite part. The aluminum alloy parts, graphite parts, and aluminum alloy parts are stacked in sequence to form a connecting assembly. The connecting assembly is placed in the middle of the electrodes of the pulse current diffusion connecting device. Pressure and pulse current are applied to the connecting assembly under a protective atmosphere to form a connection. The pressure range is 1MPa-30MPa. After heating is completed and cooled to room temperature, a composite substrate is obtained. The heating method is pulse current heating. The pulse frequency of the pulse current is 100 Hz-10000Hz, the heating temperature range is 450℃-650℃, and the holding time is 1 min-120 min.

2. The method for preparing graphite / aluminum layered composite materials with pulsed current assistance according to claim 1, characterized in that, The step of pre-treating the aluminum alloy to obtain the aluminum alloy part includes: Use 800#, 1200#, and 2000# sandpaper to grind and polish the aluminum alloy surface step by step; The polished aluminum alloy is immersed in a diethylene glycol dimethyl ether solution for cleaning to obtain an aluminum alloy part.

3. The method for preparing graphite / aluminum layered composite materials with pulsed current assistance according to claim 1, characterized in that, The step of pre-treating graphite to obtain graphite parts includes: The graphite is ultrasonically cleaned to remove surface contaminants.

4. The method for preparing graphite / aluminum layered composite materials with pulsed current assistance according to claim 1, characterized in that, The graphite is any one of hot isostatic graphite, pyrolytic graphite, and graphene film.

5. The method for preparing graphite / aluminum layered composite materials with pulsed current assistance according to claim 1, characterized in that, The protective atmosphere is a vacuum atmosphere or an inert gas atmosphere, wherein the inert gas is any one of helium, argon or nitrogen.

6. The method for preparing graphite / aluminum layered composite materials with pulsed current assistance according to claim 1, characterized in that, The heating rate is 50℃ / min - 500℃ / min, and the cooling rate is 50℃ / min - 200℃ / min.

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