Phase change heat conducting film based on low melting point alloy oxidation doping and preparation method thereof

Abstract

The application discloses a phase change heat conducting film based on low-melting alloy oxidation doping and a preparation method thereof. The phase change heat conducting film is composed of a low-melting alloy and in-situ oxidized and internalized metal oxides, the low-melting alloy is composed of a ternary alloy formed by three metals of indium, bismuth and tin, and the metal oxides include four kinds of indium oxide, bismuth oxide, tin oxide and stannous oxide. The low-melting alloy is doped into the alloy interior by stirring and in-situ generated metal oxides at the air interface, the film forming performance is improved by using the enhanced heterogeneous interface interaction force, the problem of leakage of molten metal after phase change of the phase change heat conducting film is solved, the thermal performance is much higher than that of the current phase change thermal interface material, the phase change heat conducting film can be recycled and reused, and good application prospect and commercial development value are shown.

Description

Technical Field

[0001] This invention relates to the field of thermal interface materials, and more specifically, to phase change thermally conductive thin films based on low-melting-point alloy oxide doping and their preparation methods. Background Technology

[0002] Thermal interface materials are primarily used to fill the micro-gaps of air between the rough contact interface of heat-generating electronic devices and heat dissipation units, establishing an effective interfacial heat conduction channel to achieve efficient heat dissipation for electronic devices. However, currently widely used single-phase thermal interface materials, including thermal grease (liquid), thermal gel (semi-solid), and thermal pads (solid), cannot combine the advantages of high void filling rate and low interfacial thermal resistance of liquid thermal interface materials with the high application convenience and reliability of solid thermal interface materials. This is one of the key pain points in the current application of traditional single-phase thermal interface materials.

[0003] In recent years, phase change thermal interface materials (PCIs) have emerged as a new type of thermal interface material for thermal management of microelectronic devices such as lithium batteries and LED chips, attracting widespread attention. Compared to traditional single-phase thermal interface materials, their most significant characteristic is the phase change that occurs within the operating temperature range of the electronic device. During installation and operation, they are in a solid state, making them convenient to use. When the electronic device heats up, they transition from a solid state to a molten state, further filling the interfacial gap between the heat dissipation module and the heat-generating electronic device, thereby more effectively reducing contact thermal resistance. This temperature-triggered phase switching is an ideal characteristic of thermal interface materials. However, current PCIs are generally composed of polydimethylsiloxane and olefin block copolymers as the matrix, with paraffin, polyolefins, and low-molecular-weight alcohols as phase change components. Clearly, the inherently low thermal conductivity (0.2–0.4 W / m·K) of organic polymers greatly limits the application of PCIs in current and future high heat flux density electronic devices, as their thermal conductivity is generally less than 5 W / m·K.

[0004] Low-melting-point alloys refer to a class of special alloys with melting points near room temperature. As a metallic phase change material, they possess ideal physical / chemical properties when used as phase change thermal interface materials, including thermal conductivity far exceeding that of organic polymers; suitable phase change temperature; solid mechanical properties of conventional metals in the crystalline state; and fluid compliance in the molten state. However, good reliability and excellent thermal performance are always mutually exclusive. For example, patent CN105838333A discloses a phase change alloy thermal interface composite material and its preparation method, and patent CN105483486A discloses a low-melting-point alloy and a thermal interface material made using the low-melting-point alloy. The leakage problem of the molten alloy in the above patents is not considered, which poses a risk of short circuits in electronic devices. Patent CN115197677A discloses a thermal interface material with phase change function, its preparation method and application, and patent CN103740978A discloses a multiphase liquid metal thermal interface material with overflow prevention function and its preparation method. While the aforementioned patents have solved the leakage problem of molten alloys, the introduction of the polymer phase and the presence of a large amount of rigid solid phase during use significantly increase the interfacial thermal resistance, thereby sacrificing the excellent thermal properties of the molten low-melting-point alloy itself. Therefore, there is an urgent need to develop low-melting-point alloy phase change thermal interface materials with high reliability and strong thermal performance, as well as their preparation processes. Summary of the Invention

[0005] To address the aforementioned problems and shortcomings, the present invention aims to provide a phase change thermally conductive thin film based on the oxidation doping of low-melting-point alloys and its preparation method. Combining the advantages of metallic materials and phase change materials, this invention not only overcomes the shortcomings of current polymer-based phase change thermal interface materials, such as low thermal conductivity and difficulty in significantly improving it, but also solves the problem of molten metal leakage during the use of low-melting-point metals as phase change thermal interface materials, thus enabling the film to possess the characteristics of high thermal conductivity, low thermal resistance, leakage resistance, flexible and convenient use, and recyclability.

[0006] The objective of this invention can be achieved through the following technical solutions.

[0007] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0008] (1) Heating a solid low-melting-point alloy to a molten state to obtain a molten low-melting-point alloy;

[0009] (2) In an air atmosphere, heat and stir the molten low-melting-point alloy obtained in step (1) to obtain a low-melting-point alloy paste containing metal oxides obtained by in-situ oxidation.

[0010] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a preheated glass substrate to obtain a low-melting-point alloy coating.

[0011] (4) After the low melting point alloy coating obtained in step (3) is naturally cooled to room temperature, it is peeled off to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0012] Preferably, in step (1), the solid low-melting-point alloy is composed of the following metals (in mass fraction): 51% indium, 32.5% bismuth, and 16.5% tin.

[0013] Preferably, in step (2), the metal oxide obtained by in-situ oxidation includes four types: indium oxide, bismuth oxide, tin oxide and tin oxide, and their total content in the low melting point alloy paste is 1000 to 5000 ppm.

[0014] Preferably, in step (2), the heating temperature is 80 to 120°C.

[0015] Preferably, in step (2), the stirring method is mechanical stirring, the stirring speed is 300-1000 rpm, and the stirring time is 6-30 minutes.

[0016] Preferably, in step (3), the coating method is flat plate coating, and the preheating temperature of the glass substrate is 80-120°C.

[0017] Preferably, in step (4), the room temperature condition is 25°C.

[0018] The phase change thermally conductive thin film based on the oxidation doping of low-melting-point alloys prepared by any of the above methods is composed of low-melting-point alloys and metal oxides obtained by in-situ oxidation of them.

[0019] Preferably, the metal oxide obtained by in-situ oxidation includes four types: indium oxide, bismuth oxide, tin oxide, and tin suboxide, and their total content in the entire phase change thermally conductive film is 1000-5000 ppm.

[0020] Preferably, the phase transition temperature of the phase transition thermally conductive thin film based on low-melting-point alloy oxide doping is 60.2 to 60.4 °C.

[0021] Preferably, the thickness of the phase change thermally conductive film based on low-melting-point alloy oxide doping is 25–400 μm.

[0022] Compared with the prior art, the phase change thermally conductive thin film based on low-melting-point alloy oxide doping and its preparation method provided by the present invention have the following beneficial effects:

[0023] (1) The phase change thermal conductive film based on low melting point alloy oxidation doping prepared by the present invention relies on the rapid growth and internalization of bismuth oxide and tin oxide during the oxidation doping process to generate more metal / metal oxide heterostructures in the low melting point alloy system, providing more van der Waals force interaction sites, enhancing the interfacial interaction between metal oxide and low melting point alloy, increasing the surface free energy, significantly changing the rheological properties of the original low melting point alloy system, significantly improving plasticity and viscosity, thereby effectively strengthening the film formation effect and endowing it with anti-leakage ability.

[0024] (2) The phase change thermal conductive film based on low melting point alloy oxidation doping prepared by this invention has unique material properties and preparation process. Before phase change, it exhibits excellent solid mechanical properties of conventional metals, and is lightweight and easy to shear, easy to assemble / disassemble, and its structure is not damaged. After phase change, it has autonomous anti-leakage function and good metal compatibility, which meets the requirements of convenience and reliability as a new type of phase change thermal interface material for cooling electronic devices, and can be reused multiple times.

[0025] (3) The phase change thermally conductive thin film based on low-melting-point alloy oxide doping prepared by this invention exhibits stable and easily controllable phase change behavior. Measurements show almost no supercooling, and the phase change temperature and enthalpy remain virtually unchanged before and after 500 phase change cycles. Its thermal conductivity reaches a maximum of 8.3 W / m·K, and its thermal resistance after phase change is as low as 0.01 cm. 2 With a K / W ratio, its thermal performance is significantly better than that of existing reported and commercially available phase change thermal interface materials.

[0026] (4) The present invention has a short preparation process, simple preparation process, fast preparation speed, mild process conditions and easy to meet, which is conducive to commercial application. Attached Figure Description

[0027] Figure 1 This is a flowchart of the preparation process of phase change thermally conductive thin films based on the oxidation doping of low-melting-point alloys.

[0028] Figure 2 These are schematic diagrams illustrating the working principle of heat dissipation in electronic devices as described in Examples 1-9.

[0029] Figure 3 This is a phase transition temperature diagram of Examples 1 to 9 before and after 500 phase transition cycles.

[0030] Specific examples

[0031] The embodiments of the present invention will be described in further detail below with reference to the examples and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0032] The fabrication process of this invention based on low-melting-point alloy oxide-doped phase change thermally conductive thin films is shown in the following flowchart. Figure 1 As shown.

[0033] Example 1

[0034] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0035] (1) The solid indium bismuth tin ternary low melting point alloy is heated to 100°C to melt it, and a molten low melting point alloy is obtained.

[0036] (2) In an air atmosphere at 100°C, the molten low melting point alloy obtained in step (1) is stirred uniformly at a speed of 300 rpm for 6 minutes using a stirrer to obtain an oxide-doped low melting point alloy paste, at which time the metal oxide content is 1000 ppm.

[0037] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a glass substrate preheated to 100°C to obtain a low-melting-point alloy coating. The coating thickness is controlled by a coating machine and the coating thickness is 100 μm.

[0038] (4) After the low melting point alloy coating obtained in step (3) has cooled naturally to room temperature of 25°C, it is manually peeled off from the glass substrate with stainless steel tweezers to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0039] The solid indium-bismuth-tin ternary low-melting-point alloy described in step (1) consists of the following components by mass fraction: 51% indium, 32.5% bismuth and 16.5% tin.

[0040] The specific composition of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The content of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using an oxygen, nitrogen, and hydrogen analyzer. The phase transition temperature and enthalpy of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping before and after 500 phase transition cycles were determined using differential scanning calorimetry. The thermal conductivity and post-phase transition thermal impedance of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping after 500 phase transition cycles were tested using the transient planar heat source method and the steady-state heat flow method, respectively. The metal compatibility of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was characterized using energy dispersive spectroscopy. The leakage of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was observed and the mass loss rate was statistically analyzed under test conditions of 200 psi and 100 °C.

[0041] Example 2

[0042] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0043] (1) The solid indium bismuth tin ternary low melting point alloy is heated to 100°C to melt it, and a molten low melting point alloy is obtained.

[0044] (2) In an air atmosphere at 100°C, the molten low melting point alloy obtained in step (1) is stirred uniformly at a speed of 700 rpm for 18 minutes using a stirrer to obtain an oxide-doped low melting point alloy paste, at which time the metal oxide content is 3000 ppm.

[0045] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a glass substrate preheated to 100°C to obtain a low-melting-point alloy coating. The coating thickness is controlled by a coating machine and the coating thickness is 100 μm.

[0046] (4) After the low melting point alloy coating obtained in step (3) has cooled naturally to room temperature of 25°C, it is manually peeled off from the glass substrate with stainless steel tweezers to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0047] The solid indium-bismuth-tin ternary low-melting-point alloy described in step (1) consists of the following components by mass fraction: 51% indium, 32.5% bismuth and 16.5% tin.

[0048] The specific composition of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The content of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using an oxygen, nitrogen, and hydrogen analyzer. The phase transition temperature and enthalpy of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping before and after 500 phase transition cycles were determined using differential scanning calorimetry. The thermal conductivity and post-phase transition thermal impedance of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping after 500 phase transition cycles were tested using the transient planar heat source method and the steady-state heat flow method, respectively. The metal compatibility of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was characterized using energy dispersive spectroscopy. The leakage of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was observed and the mass loss rate was statistically analyzed under test conditions of 200 psi and 100 °C.

[0049] Example 3

[0050] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0051] (1) The solid indium bismuth tin ternary low melting point alloy is heated to 100°C to melt it, and a molten low melting point alloy is obtained.

[0052] (2) In an air atmosphere at 100°C, the molten low melting point alloy obtained in step (1) is stirred uniformly at a speed of 1000 rpm for 30 minutes using a stirrer to obtain an oxide-doped low melting point alloy paste, at which time the metal oxide content is 5000 ppm.

[0053] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a glass substrate preheated to 100°C to obtain a low-melting-point alloy coating. The coating thickness is controlled by a coating machine and the coating thickness is 100 μm.

[0054] (4) After the low melting point alloy coating obtained in step (3) has cooled naturally to room temperature of 25°C, it is manually peeled off from the glass substrate with stainless steel tweezers to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0055] The solid indium-bismuth-tin ternary low-melting-point alloy described in step (1) consists of the following components by mass fraction: 51% indium, 32.5% bismuth and 16.5% tin.

[0056] The specific composition of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The content of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using an oxygen, nitrogen, and hydrogen analyzer. The phase transition temperature and enthalpy of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping before and after 500 phase transition cycles were determined using differential scanning calorimetry. The thermal conductivity and post-phase transition thermal impedance of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping after 500 phase transition cycles were tested using the transient planar heat source method and the steady-state heat flow method, respectively. The metallic compatibility between the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping and aluminum was characterized using energy dispersive spectroscopy. The leakage of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was observed and the mass loss rate was statistically analyzed under test conditions of 200 psi and 100 °C.

[0057] Example 4

[0058] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0059] (1) The solid indium bismuth tin ternary low melting point alloy is heated to 80°C to melt it, and a molten low melting point alloy is obtained;

[0060] (2) In an air atmosphere at 80°C, the molten low melting point alloy obtained in step (1) is stirred uniformly at a speed of 300 rpm for 6 minutes using a stirrer to obtain an oxide-doped low melting point alloy paste, at which time the metal oxide content is 1000 ppm.

[0061] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a glass substrate preheated to 100°C to obtain a low-melting-point alloy coating. The coating thickness is controlled by a coating machine and the coating thickness is 100 μm.

[0062] (4) After the low melting point alloy coating obtained in step (3) has cooled naturally to room temperature of 25°C, it is manually peeled off from the glass substrate with stainless steel tweezers to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0063] The solid indium-bismuth-tin ternary low-melting-point alloy described in step (1) consists of the following components by mass fraction: 51% indium, 32.5% bismuth and 16.5% tin.

[0064] The specific composition of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The content of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using an oxygen, nitrogen, and hydrogen analyzer. The phase transition temperature and enthalpy of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping before and after 500 phase transition cycles were determined using differential scanning calorimetry. The thermal conductivity and post-phase transition thermal impedance of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping after 500 phase transition cycles were tested using the transient planar heat source method and the steady-state heat flow method, respectively. The metallic compatibility between the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping and aluminum was characterized using energy dispersive spectroscopy. The leakage of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was observed and the mass loss rate was statistically analyzed under test conditions of 200 psi and 100 °C.

[0065] Example 5

[0066] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0067] (1) The solid indium bismuth tin ternary low melting point alloy is heated to 120°C to melt it, and a molten low melting point alloy is obtained;

[0068] (2) In an air atmosphere at 120°C, the molten low melting point alloy obtained in step (1) is stirred uniformly at a speed of 300 rpm for 6 minutes using a stirrer to obtain an oxide-doped low melting point alloy paste, at which time the metal oxide content is 1000 ppm.

[0069] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a glass substrate preheated to 100°C to obtain a low-melting-point alloy coating. The coating thickness is controlled by a coating machine and the coating thickness is 100 μm.

[0070] (4) After the low melting point alloy coating obtained in step (3) has cooled naturally to room temperature of 25°C, it is manually peeled off from the glass substrate with stainless steel tweezers to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0071] The solid indium-bismuth-tin ternary low-melting-point alloy described in step (1) consists of the following components by mass fraction: 51% indium, 32.5% bismuth and 16.5% tin.

[0072] The specific composition of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The content of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using an oxygen, nitrogen, and hydrogen analyzer. The phase transition temperature and enthalpy of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping before and after 500 phase transition cycles were determined using differential scanning calorimetry. The thermal conductivity and post-phase transition thermal impedance of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping after 500 phase transition cycles were tested using the transient planar heat source method and the steady-state heat flow method, respectively. The metallic compatibility between the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping and aluminum was characterized using energy dispersive spectroscopy. The leakage of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was observed and the mass loss rate was statistically analyzed under test conditions of 200 psi and 100 °C.

[0073] Example 6

[0074] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0075] (1) The solid indium bismuth tin ternary low melting point alloy is heated to 100°C to melt it, and a molten low melting point alloy is obtained.

[0076] (2) In an air atmosphere at 100°C, the molten low melting point alloy obtained in step (1) is stirred uniformly at a speed of 300 rpm for 6 minutes using a stirrer to obtain an oxide-doped low melting point alloy paste, at which time the metal oxide content is 1000 ppm.

[0077] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a glass substrate preheated to 80°C to obtain a low-melting-point alloy coating. The coating thickness is controlled by a coating machine and the coating thickness is 100 μm.

[0078] (4) After the low melting point alloy coating obtained in step (3) has cooled naturally to room temperature of 25°C, it is manually peeled off from the glass substrate with stainless steel tweezers to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0079] The solid indium-bismuth-tin ternary low-melting-point alloy described in step (1) consists of the following components by mass fraction: 51% indium, 32.5% bismuth and 16.5% tin.

[0080] The specific composition of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The content of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using an oxygen, nitrogen, and hydrogen analyzer. The phase transition temperature and enthalpy of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping before and after 500 phase transition cycles were determined using differential scanning calorimetry. The thermal conductivity and post-phase transition thermal impedance of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping after 500 phase transition cycles were tested using the transient planar heat source method and the steady-state heat flow method, respectively. The metallic compatibility between the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping and aluminum was characterized using energy dispersive spectroscopy. The leakage of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was observed and the mass loss rate was statistically analyzed under test conditions of 200 psi and 100 °C.

[0081] Example 7

[0082] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0083] (1) The solid indium bismuth tin ternary low melting point alloy is heated to 100°C to melt it, and a molten low melting point alloy is obtained.

[0084] (2) In an air atmosphere at 100°C, the molten low melting point alloy obtained in step (1) is stirred uniformly at a speed of 300 rpm for 6 minutes using a stirrer to obtain an oxide-doped low melting point alloy paste, at which time the metal oxide content is 1000 ppm.

[0085] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a glass substrate preheated to 120°C to obtain a low-melting-point alloy coating. The coating thickness is controlled by a coating machine and the coating thickness is 100 μm.

[0086] (4) After the low melting point alloy coating obtained in step (3) has cooled naturally to room temperature of 25°C, it is manually peeled off from the glass substrate with stainless steel tweezers to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0087] The solid indium-bismuth-tin ternary low-melting-point alloy described in step (1) consists of the following components by mass fraction: 51% indium, 32.5% bismuth and 16.5% tin.

[0088] The specific composition of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The content of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using an oxygen, nitrogen, and hydrogen analyzer. The phase transition temperature and enthalpy of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping before and after 500 phase transition cycles were determined using differential scanning calorimetry. The thermal conductivity and post-phase transition thermal impedance of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping after 500 phase transition cycles were tested using the transient planar heat source method and the steady-state heat flow method, respectively. The metallic compatibility between the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping and aluminum was characterized using energy dispersive spectroscopy. The leakage of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was observed and the mass loss rate was statistically analyzed under test conditions of 200 psi and 100 °C.

[0089] Example 8

[0090] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0091] (1) The solid indium bismuth tin ternary low melting point alloy is heated to 100°C to melt it, and a molten low melting point alloy is obtained.

[0092] (2) In an air atmosphere at 100°C, the molten low melting point alloy obtained in step (1) is stirred uniformly at a speed of 300 rpm for 6 minutes using a stirrer to obtain an oxide-doped low melting point alloy paste, at which time the metal oxide content is 1000 ppm.

[0093] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a glass substrate preheated to 100°C to obtain a low-melting-point alloy coating. The coating thickness is controlled by a coating machine and the coating thickness is 25 μm.

[0094] (4) After the low melting point alloy coating obtained in step (3) has cooled naturally to room temperature of 25°C, it is manually peeled off from the glass substrate with stainless steel tweezers to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0095] The solid indium-bismuth-tin ternary low-melting-point alloy described in step (1) consists of the following components by mass fraction: 51% indium, 32.5% bismuth and 16.5% tin.

[0096] The specific composition of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The content of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using an oxygen, nitrogen, and hydrogen analyzer. The phase transition temperature and enthalpy of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping before and after 500 phase transition cycles were determined using differential scanning calorimetry. The thermal conductivity and post-phase transition thermal impedance of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping after 500 phase transition cycles were tested using the transient planar heat source method and the steady-state heat flow method, respectively. The metallic compatibility between the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping and aluminum was characterized using energy dispersive spectroscopy. The leakage of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was observed and the mass loss rate was statistically analyzed under test conditions of 200 psi and 100 °C.

[0097] Example 9

[0098] The method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping includes the following steps:

[0099] (1) The solid indium bismuth tin ternary low melting point alloy is heated to 100°C to melt it, and a molten low melting point alloy is obtained.

[0100] (2) In an air atmosphere at 100°C, the molten low melting point alloy obtained in step (1) is stirred uniformly at a speed of 300 rpm for 6 minutes using a stirrer to obtain an oxide-doped low melting point alloy paste, at which time the metal oxide content is 1000 ppm.

[0101] (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a glass substrate preheated to 100°C to obtain a low-melting-point alloy coating. The coating thickness is controlled by a coating machine and the coating thickness is 400 μm.

[0102] (4) After the low melting point alloy coating obtained in step (3) has cooled naturally to room temperature of 25°C, it is manually peeled off from the glass substrate with stainless steel tweezers to obtain a phase change thermal conductive film based on low melting point alloy oxide doping.

[0103] The solid indium-bismuth-tin ternary low-melting-point alloy described in step (1) consists of the following components by mass fraction: 51% indium, 32.5% bismuth and 16.5% tin.

[0104] The specific composition of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The content of metal oxides in the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was determined using an oxygen, nitrogen, and hydrogen analyzer. The phase transition temperature and enthalpy of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping before and after 500 phase transition cycles were determined using differential scanning calorimetry. The thermal conductivity and post-phase transition thermal impedance of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping after 500 phase transition cycles were tested using the transient planar heat source method and the steady-state heat flow method, respectively. The metallic compatibility between the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping and aluminum was characterized using energy dispersive spectroscopy. The leakage of the obtained phase change thermally conductive film based on low-melting-point alloy oxide doping was observed and the mass loss rate was statistically analyzed under test conditions of 200 psi and 100 °C.

[0105] The composition and content of metal oxides in the phase change thermally conductive films based on low-melting-point alloy oxide doping prepared in Examples 1-9 were tested respectively; the phase change temperature and enthalpy before and after 500 phase change cycles; the thermal conductivity and thermal resistance after 500 phase change cycles; the metal compatibility with aluminum; and the leakage were also tested. The test results are shown in Tables 1-4. Table 1 shows the composition and content of metal oxides in Examples 1-9; Table 2 shows the changes in phase change temperature and enthalpy after 500 phase change cycles in the phase change thermally conductive films prepared in Examples 1-9; Table 3 shows the thermal conductivity and thermal resistance of the phase change thermally conductive films prepared in Examples 1-9; and Table 4 shows the mass loss rate and leakage of the phase change thermally conductive films prepared in Examples 1-9. As shown in Table 1, the obtained phase change thermally conductive films based on low-melting-point alloy oxide doping contain four metal oxides: indium oxide, bismuth oxide, tin oxide, and stannous oxide. Their content increases with increasing stirring rate and stirring time. The phase transition temperature and enthalpy remained almost unchanged after 500 phase transition cycles, with virtually no supercooling. Its thermal conductivity reached a maximum of 8.3 W / m·K, and its thermal resistance after the phase transition was a minimum of 0.01 cm⁻¹. 2 • K / W. After phase transformation, it exhibits good metallic compatibility and possesses independent anti-leakage function.

[0106] Figure 2 The working principle of Examples 1-9 applied between electronic devices and heat sinks is demonstrated.

[0107] Figure 3 The changes in phase transition temperature of Examples 1 to 9 before and after 500 phase transition cycles are shown.

[0108] Table 1

[0109]

[0110] Table 2

[0111]

[0112]

[0113] Table 3

[0114] Example Thermal conductivity (W / m·K) <![CDATA[Thermal impedance (K·cm 2 / W) <!-- 9 -->]]> Example 1 8.3 0.03 Example 2 6.8 0.07 Example 3 5.4 0.12 Example 4 8.3 0.03 Example 5 8.3 0.03 Example 6 8.3 0.03 Example 7 8.3 0.03 Example 8 8.3 0.01 Example 9 8.3 0.12

[0115] Table 4

[0116] Example Metal compatibility Quality loss rate (%) Leakage situation Example 1 good 0.41 No leakage Example 2 good 0.52 No leakage Example 3 good 0.39 No leakage Example 4 good 0.41 No leakage Example 5 good 0.38 No leakage Example 6 good 0.21 No leakage Example 7 good 0.18 No leakage Example 8 good 0.31 No leakage Example 9 good 0.25 No leakage

[0117] Matters not covered in this invention are common knowledge.

[0118] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing phase change thermally conductive thin films based on low-melting-point alloy oxide doping, characterized in that, Includes the following steps: (1) Heating a solid low-melting-point alloy to a molten state to obtain a molten low-melting-point alloy; the solid low-melting-point alloy is composed of the following metals, in mass fraction: 51% indium, 32.5% bismuth, and 16.5% tin; (2) In an air atmosphere, heat and uniformly stir the molten low-melting-point alloy obtained in step (1) at a heating temperature of 80-120°C, using mechanical stirring at a speed of 300-1000 rpm for 6-30 minutes to obtain a low-melting-point alloy paste containing metal oxides obtained by in-situ oxidation; the metal oxides obtained by in-situ oxidation include four types: indium oxide, bismuth oxide, tin oxide, and stannous oxide, and their total content in the low-melting-point alloy paste is 1000-5000 ppm; (3) The oxide-doped low-melting-point alloy paste obtained in step (2) is uniformly coated on a preheated glass substrate. The preheating temperature of the glass substrate is 80-120°C, and the coating method is flat plate coating to obtain a low-melting-point alloy coating. (4) After the low melting point alloy coating obtained in step (3) is naturally cooled to room temperature, it is peeled off to obtain a phase change thermal conductive film based on low melting point alloy oxide doping; the phase change thermal conductive film has a phase change temperature of 60.2 to 60.4°C and a thickness of 25 to 400 μm.

2. The phase change thermally conductive thin film based on low-melting-point alloy oxide doping prepared by the preparation method according to claim 1, characterized in that, The phase change thermally conductive film based on low-melting-point alloy oxidation doping is composed of low-melting-point alloy and metal oxides obtained by in-situ oxidation.

3. The phase change thermally conductive thin film based on low-melting-point alloy oxide doping according to claim 2, characterized in that, The metal oxides obtained by in-situ oxidation include four types: indium oxide, bismuth oxide, tin oxide, and tin oxide.

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