Conductive hot melt adhesive with near-infrared light welding characteristics and preparation method thereof

Abstract

The application discloses a conductive hot melt adhesive with near-infrared light welding characteristics, and belongs to the technical field of material science, which comprises gallium-indium liquid metal, thioctic acid and a multivalent crosslinking agent; a preparation method is as follows: the gallium-indium liquid metal, the thioctic acid and the multivalent crosslinking agent are mixed and placed into a garnet mortar for grinding to obtain a precursor powder; the precursor powder is heated to obtain the conductive hot melt adhesive with the near-infrared light welding characteristics. The prepared conductive hot melt adhesive has good conductivity, and can realize effective bonding for various solid substrates through near-infrared light irradiation. The preparation process of the conductive hot melt adhesive is simple, the conditions are mild, and the time is short, and the application is an energy-saving, green and environment-friendly synthesis method. The obtained conductive hot melt adhesive can be processed into different shapes for storage, and can be adhered to different substrates through direct heating or near-infrared light irradiation when needed, and can exhibit good bonding performance after room temperature curing.

Description

Technical Field

[0001] The present invention relates to the field of material science and technology, and in particular to a conductive hot melt adhesive with near-infrared light welding characteristics and a preparation method thereof. Background Art

[0002] Advances in modern electronics and information technology are driving the development of electronic devices toward high integration, miniaturization, lightweighting, and high performance. This poses new challenges to the assembly technology of high-density electronic devices. Electronic components, circuit connections, and chip packaging typically utilize traditional metal welding techniques, which face challenges such as corrosion, low solder joint strength, solder joint fatigue, cracking caused by internal stress in interconnects, and contamination. To address this, the international community is actively developing new bonding technologies based on conductive adhesives to replace traditional metal welding. Conductive adhesives are functional adhesives that possess both electrical conductivity and adhesive properties. They typically consist of a viscous polymer resin matrix (typically epoxy resin, silicone, polyamide, and polyurethane) and a conductive filler (such as metal, carbon material, or conductive polymer). Conductive adhesives can establish effective bonding with different substrates, including bonding with non-solderable surfaces such as ceramics and glass. Therefore, they are favored in various application scenarios such as assembly, connection, integration, and packaging of integrated microelectronic products (Zhang D, Liu S, Jiang Y, et al. A flexible adhesive with a conductivity of 5240S / cm[J]. Science bulletin, 2021, 66(7): 657-660. Pang Kaimin, Deng Zuozhu. A conductive silver adhesive and its preparation method and application: 202211231498[P]. Haque ABMT, Ho DH, Hwang D, et al. Electrically conductive liquid metal composite adhesives for reversible bonding of soft electronics[J]. Advanced Functional Materials, 2023: 2304101.). Currently, the bonding methods of conductive adhesives mainly include pressure-sensitive tape bonding, glue coating or heated melt coating (Zhang Jiuyang, Li Yan. A conductive hot melt adhesive and its preparation method: 202210288276[P]. Latko- P, Misiak M, Boczkowska A. Electrically conductive adhesive based on thermoplastic hot melt copolyamide and multi-walled carbon nanotubes[J]. Polymers, 2022, 14(20): 4371.). However, pressure-sensitive tape is limited by its low bonding strength and is only used as a coating material. The glue coating bonding method takes a long time to cure and is limited in the use environment, making it difficult to apply to the bonding of microelectronic components with highly limited spatial dimensions. The melt coating of conductive hot melt adhesive is the main bonding method used in electronic component assembly, that is, the conductive adhesive is contact-heated at the welding point, and after the conductive adhesive is melted, the electronic components, leads or high-density circuits are bonded. This contact heating method can easily cause damage to the electronic components or substrates around the conductive adhesive, and needs further improvement.

[0003] Therefore, providing a conductive hot melt adhesive with good conductivity and effective bonding to various solid substrates through infrared light irradiation and a preparation method thereof is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0004] In light of this, the present invention provides a light-weldable conductive hot melt adhesive containing liquid metal and a method for preparing the same. The conductive hot melt adhesive can effectively bond a variety of materials under heating or near-infrared light irradiation while maintaining its conductivity, and is suitable for applications such as packaging and bonding electronic components and assemblies.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The invention discloses a conductive hot melt adhesive with near-infrared light welding characteristics, which is composed of the following raw materials: gallium-indium liquid metal, thioctic acid and a multivalent cross-linking agent.

[0007] Preferably, the conductive hot melt adhesive with near-infrared light welding properties is composed of the following raw materials in percentage by mass: 65%-75% gallium-indium liquid metal, 22.5%-27.5% lipoic acid, and 2.5%-7.5% multivalent crosslinking agent.

[0008] Furthermore, the mass fraction of gallium in the gallium-indium liquid metal is 75.5% to 100%, and the mass fraction of indium is 24.5% to 0%.

[0009] The beneficial effect of adopting the above further solution is that in the above solution of the present invention, especially when the mass fraction of gallium in the gallium-indium liquid metal is 75.5% and the mass fraction of indium is 24.5%, its melting point is close to 25°C, which is conducive to application.

[0010] Furthermore, the gallium-indium liquid metal can be replaced by silver nanosheets or silver nanowires.

[0011] Furthermore, any one or more of the multivalent cross-linking agents selected from tannic acid, polyvinyl alcohol, N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine and chitosan are mixed.

[0012] The beneficial effect of adopting the above further scheme is that the present invention can prepare conductive hot melt adhesives with different properties by adjusting the types and contents of conductive fillers and multivalent crosslinking agents, which reflects the universality and performance adjustability of the process of the present invention.

[0013] Furthermore, the light source for optical welding is near-infrared light, the light source power is 0.5-2.0W, and the near-infrared light wavelength is 780-1100nm.

[0014] Furthermore, the distance between any light source and the conductive hot melt adhesive during the optical welding process is 2.5-10.0 cm.

[0015] The beneficial effect of adopting the above further solution is that the present invention can adjust the melting time of the conductive hot melt adhesive and the temperature of the light source irradiation point by adjusting the light source power and the distance between the light source and the conductive hot melt adhesive, making this conductive hot melt adhesive suitable for a variety of application scenarios.

[0016] The present invention also provides a method for preparing the conductive hot melt adhesive having near-infrared light welding properties, comprising the following steps:

[0017] (1) Weigh each raw material according to the above mass percentage;

[0018] (2) mixing gallium-indium liquid metal, thioctic acid, and a multivalent crosslinking agent in an agate mortar and grinding to obtain a precursor powder;

[0019] (3) The precursor powder is heated to obtain a conductive hot melt adhesive having near-infrared light welding properties.

[0020] Furthermore, the grinding time in step (2) is 15-25 min.

[0021] Furthermore, the heating temperature in step (2) is 75-85° C., and the heating time is 25-35 min.

[0022] Furthermore, the heating is any one of an oil bath, a water bath, an air bath and a metal bath.

[0023] The beneficial effect of adopting the above further solution is that the above solution of the present invention can make the raw materials mixed evenly and the reaction as thorough as possible.

[0024] The present invention provides a conductive hot melt adhesive with optical welding properties, comprising a metal conductive component, lipoic acid, and a multivalent crosslinking agent, and a preparation process thereof. The resulting conductive hot melt adhesive exhibits excellent electrical conductivity and can effectively bond to a variety of solid substrates through near-infrared light irradiation.

[0025] The present invention uses lipoic acid, a multivalent cross-linking agent, and a metal conductive component as raw materials. The three raw materials are first solid-phase ground to obtain a precursor powder, and then the precursor powder is heated to prepare a conductive hot melt adhesive with near-infrared light (808nm) welding properties. The preparation process of the conductive hot melt adhesive of the present invention is simple, the conditions are mild, and the preparation time is short. It is an energy-saving, green, and environmentally friendly synthesis method. The resulting conductive hot melt adhesive can be processed into different shapes for storage (such as amorphous powder, microspheres, blocks, etc.). When needed, it can be adhered to different substrates by direct heating or near-infrared light irradiation. After curing at room temperature, it can exhibit good bonding properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Photographs of solid powders of liquid metal, lipoic acid, and tannic acid before and after grinding in Example 1 of the present invention, as well as a digital photograph of the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive formed by heating the ground powder;

[0027] Figure 2 This is a digital photograph of the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive prepared in Example 1 of the present invention, which is able to conduct electricity after being cured in a mold and connected to a circuit;

[0028] Figure 3 This is a digital photograph of the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive prepared in Example 1 of the present invention bonded to different solid substrates;

[0029] Figure 4 This is a bar graph showing the shear tensile strength of the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive prepared in Example 1 of the present invention when bonded to different solid substrates;

[0030] Figure 5 This is a digital photograph of the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive prepared in Example 1 of the present invention being used to weld an LED lamp into a circuit under near-infrared light irradiation to form an effective loop. DETAILED DESCRIPTION

[0031] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0032] In the embodiments of the present application, the liquid metal specifically refers to gallium-indium liquid metal composed of 75.5% gallium and 24.5% indium.

[0033] Embodiment 1

[0034] 140 mg of liquid metal, 50 mg of lipoic acid and 10 mg of tannic acid were respectively placed in a marver and ground at 25°C for 20 min to obtain a precursor powder. Subsequently, the precursor powder was placed in a 3 mL glass bottle and heated in an 80°C oil bath for 30 min to obtain a black viscous glue.

[0035] Figure 1 are photos of the solid powder of the liquid metal, lipoic acid and tannic acid before and after grinding, and a digital photo of the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive formed after heating of the ground powder; it can be seen from the photos that the sample of the ground powder changes from powder to viscous glue that can be drawn after heating to 80°C, indicating that the hot melt adhesive is formed.

[0036] Test Example 1: Conductivity Test

[0037] The powder sample of the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive prepared in Embodiment 1 was placed in a polytetrafluoroethylene mold with a size of 1.5 cm x 1.5 cm x 0.05 cm (length x width x height), and heated to 80°C to make it evenly laid in the mold, and then naturally cooled to 25°C to solidify for 10 min. The conductivity of the obtained block at 25°C was measured to be 2 x 10 4 S / m by using RTS-9 four-probe tester, indicating that the obtained liquid metal / lipoic acid / tannic acid conductive hot melt adhesive has good conductivity.

[0038] Figure 2 is a digital photo of the obtained liquid metal / lipoic acid / tannic acid conductive hot melt adhesive after solidification and shaping in the mold and connected to the circuit to form an effective conductive path, indicating that it has conductivity.

[0039] Test Example 2: Adhesion Test

[0040] The liquid metal / lipoic acid / tannic acid conductive hot melt adhesive powder prepared in Example 1 was placed on a nitrile glove and heated to 80°C using 808nm near-infrared light. Subsequently, objects of various materials (including a glass beaker, an agate mortar rod, a stainless steel weight, a Teflon reagent bottle, a wooden substrate, and a shell) were pressed onto the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive on the surface of the nitrile glove. Upon cooling to 25°C, the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive solidified to form an effective bond. The adhesive was then lifted, demonstrating the good adhesion of the resulting conductive hot melt adhesive.

[0041] In this test, a single-column universal testing machine was used to measure the lap shear strength of liquid metal / lipoic acid / tannic acid conductive hot melt adhesive on different substrates. First, the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive powder was placed on the surfaces of two substrates of the same material (stainless steel, titanium, polycarbonate, and polypropylene, with a length x width of 7 x 1.3 cm). Next, the liquid metal / lipoic acid / tannic acid conductive hot melt adhesive was heated to 80°C in an air bath. Two substrates of the same material were bonded together in an overlapping manner, with an overlap length of 2 cm and a thickness of 500 μm controlled using a steel needle. The bonded substrates were then cooled to 25°C in air and cured for 1 hour to measure their lap shear strength. Finally, the two solid substrates were fixed vertically on an electronic universal testing machine and stretched longitudinally at a speed of 10 mm / min. The maximum load required to pull the bonded substrates apart under a load parallel to the adhesive layer at 25°C was measured. The shear tensile strength was calculated based on the overlap area. The test results show that the lap shear strength of the obtained liquid metal / lipoic acid / tannic acid conductive hot melt adhesive on titanium, stainless steel, polycarbonate, and polypropylene substrates are 2.1±0.1MPa, 2.0±0.15MPa, 1.0±0.1MPa, and 0.52±0.04MPa, respectively.

[0042] Figure 3 This is a digital photo of liquid metal / lipoic acid / tannic acid conductive hot melt adhesive bonding different solid substrates; the picture shows that the conductive hot melt adhesive can bond solid objects of different materials and has obvious bonding ability.

[0043] Figure 4 This is a graph showing the shear tensile strength of liquid metal / lipoic acid / tannic acid conductive hot melt adhesive on different solid substrates. The graph shows that the bonding strength of liquid metal / lipoic acid / tannic acid conductive hot melt adhesive on high surface energy substrates is greater than 1 MPa, indicating strong bonding strength.

[0044] Test Example 3: Light Welding Performance of Conductive Hot Melt Adhesive

[0045] Figure 5is a digital photo of LED welded in the circuit by near-infrared light and forming an effective loop by liquid metal / sulphoxime acid / tannic acid conductive hot melt adhesive; it can be seen from the figure that the liquid metal / sulphoxime acid / tannic acid conductive hot melt adhesive can weld the LED lamp into the copper circuit under the irradiation of 808 nm near-infrared light and light up the LED lamp under the condition of turning on the battery power. The lighted LED lamp does not flicker and fall off during the pulling of the lead, indicating that the liquid metal / sulphoxime acid / tannic acid conductive hot melt adhesive has the light welding property.

[0046] Example 2

[0047] According to the technical solution of Example 1, other conditions are fixed, 50 mg of sulphoxime acid and 10 mg of tannic acid are changed to 65 mg of sulphoxime acid and 5 mg of tannic acid, and the conductive hot melt adhesive is prepared. Then the conductivity, tensile property and photo-thermal property of the conductive hot melt adhesive are detected according to the steps of the above test example. The conductivity test measures that the conductivity of the conductive hot melt adhesive is 2.1 x 10 4 S / m. The lap shear of the conductive hot melt adhesive to titanium, stainless steel, polycarbonate and polypropylene is 2.0 ± 0.15 MPa, 2.0 ± 0.2 MPa, 1.0 ± 0.1 MPa and 0.5 ± 0.07 MPa respectively. The conductive hot melt adhesive is irradiated under the near-infrared lamp with a power of 0.5 W and a wavelength of 808 nm for 1 min, and still can obtain the conductive hot melt adhesive with good bonding ability and conductivity.

[0048] Example 3

[0049] According to the technical solution of Example 1, other conditions are fixed, 50 mg of sulphoxime acid and 10 mg of tannic acid are changed to 45 mg of sulphoxime acid and 15 mg of tannic acid, and the conductive hot melt adhesive is prepared. Then the conductivity, tensile property and photo-thermal property of the conductive hot melt adhesive are detected according to the steps of the above test example. The conductivity test measures that the conductivity of the conductive hot melt adhesive is 2.0 x 10 4 S / m. The lap shear of the conductive hot melt adhesive to titanium, stainless steel, polycarbonate and polypropylene is 2.2 ± 0.26 MPa, 2.2 ± 0.1 MPa, 1.1 ± 0.05 MPa and 0.7 ± 0.02 MPa respectively. The conductive hot melt adhesive is irradiated under the near-infrared lamp with a power of 0.5 W and a wavelength of 808 nm for 1 min, and still can obtain the conductive hot melt adhesive with good bonding ability and conductivity.

[0050] Example 4

[0051] According to the technical solution of Example 1, keeping other conditions unchanged, the 140mg liquid metal was replaced with 130mg liquid metal and 10mg silver nanowires to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.3×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.9±0.18 MPa, 2.0±0.2 MPa, 0.9±0.21 MPa, and 0.61±0.1 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0052] Example 5

[0053] According to the technical solution of Example 1, keeping other conditions unchanged, 140 mg of liquid metal was replaced with 130 mg of liquid metal and 10 mg of silver nanosheets to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test showed that the conductive hot melt adhesive had a conductivity of 2.5×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.9±0.1MPa, 2.0±0.14MPa, 0.8±0.12MPa, and 0.58±0.08MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0054] Example 6

[0055] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 8 mg of polyvinyl alcohol (PVA) to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.0×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.9±0.1MPa, 1.8±0.1MPa, 0.94±0.11MPa, and 0.55±0.02MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0056] Example 7

[0057] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 12.5 mg of chitosan to prepare a conductive hot melt adhesive. Then, the conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were tested according to the steps of the test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.0×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive on titanium, stainless steel, polycarbonate, and polypropylene were 2.0±0.18 MPa, 1.8±0.1 MPa, 0.85±0.16 MPa, and 0.64±0.06 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0058] Example 8

[0059] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 11 mg of N,N,N',N'-tetrakis(2-hydroxyethyl) to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.1×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.9±0.2 MPa, 1.8±0.17 MPa, 0.98±0.14 MPa, and 0.60±0.05 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0060] Example 9

[0061] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 5 mg of tannic acid and 5 mg of PVA to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.0×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.9±0.15 MPa, 1.9±0.2 MPa, 1.0±0.07 MPa, and 0.68±0.09 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0062] Example 10

[0063] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 5 mg of tannic acid and 5 mg of chitosan to prepare a conductive hot melt adhesive. Then, the conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.0×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.8±0.2 MPa, 1.9±0.13 MPa, 0.95±0.1 MPa, and 0.58±0.07 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0064] Example 11

[0065] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 5 mg of tannic acid and 5 mg of N,N,N',N'-tetrakis(2-hydroxyethyl) to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.1×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive on titanium, stainless steel, polycarbonate, and polypropylene were 2.0±0.1MPa, 2.1±0.13MPa, 1.2±0.2MPa, and 0.75±0.08MPa, respectively. After irradiating the conductive hot melt adhesive under a near-infrared lamp with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0066] Example 12

[0067] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 5 mg of PVA and 5 mg of chitosan to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.0×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.9±0.11 MPa, 1.9±0.15 MPa, 0.97±0.1 MPa, and 0.62±0.04 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0068] Example 13

[0069] According to the technical solution of Example 1, keeping other conditions unchanged, 10mg of tannic acid was replaced with 5mg of PVA and 5mg of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.1×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.8±0.12 MPa, 1.7±0.2 MPa, 0.86±0.1 MPa, and 0.51±0.07 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0070] Example 14

[0071] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 5 mg of chitosan and 5 mg of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine) to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.1×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.7±0.15 MPa, 1.7±0.2 MPa, 0.84±0.1 MPa, and 0.52±0.02 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0072] Example 15

[0073] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 3 mg of tannic acid, 3 mg of PVA, and 4 mg of chitosan to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.1×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.8±0.2 MPa, 1.9±0.2 MPa, 1.0±0.1 MPa, and 0.7±0.09 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0074] Example 16

[0075] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 3 mg of tannic acid, 3 mg of PVA, and 4 mg of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.0×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.8±0.13 MPa, 1.8±0.1 MPa, 1.0±0.1 MPa, and 0.73±0.03 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0076] Example 17

[0077] According to the technical solution of Example 1, keeping other conditions unchanged, 10mg of tannic acid was replaced with 3mg of PVA, 3mg of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, and 4mg of chitosan to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test showed that the conductive hot melt adhesive had a conductivity of 2.0×10 4 S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.7±0.2 MPa, 1.8±0.15 MPa, 0.95±0.09 MPa, and 0.81±0.07 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0078] Example 18

[0079] According to the technical solution of Example 1, keeping other conditions unchanged, 10 mg of tannic acid was replaced with 2.5 mg of tannic acid, 2.5 mg of PVA, 2.5 mg of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, and 2.5 mg of chitosan to prepare a conductive hot melt adhesive. The conductivity, tensile properties, and photothermal properties of the conductive hot melt adhesive were then tested according to the steps of the above test example. The conductivity test measured that the conductive hot melt adhesive had a conductivity of 2.1×10 4S / m. The lap shear strengths of the conductive hot melt adhesive for titanium, stainless steel, polycarbonate, and polypropylene were 1.8±0.11 MPa, 1.9±0.1 MPa, 1.0±0.18 MPa, and 0.68±0.04 MPa, respectively. After irradiating the conductive hot melt adhesive under near-infrared light with a power of 0.5W and a wavelength of 808nm for 1 minute, the adhesive still exhibited excellent bonding and electrical conductivity.

[0080] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A conductive hot melt adhesive with near-infrared light welding properties, characterized in that: The invention is composed of the following raw materials: gallium-indium liquid metal, lipoic acid and a multivalent cross-linking agent; The invention is composed of the following raw materials in percentage by mass: 65%-75% of gallium-indium liquid metal, 22.5%-27.5% of lipoic acid, and 2.5%-7.5% of a multivalent cross-linking agent; The multivalent cross-linking agent is a mixture of any one or more of tannic acid, polyvinyl alcohol, N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine and chitosan.

2. The conductive hot melt adhesive with near-infrared light welding properties according to claim 1, characterized in that: The mass fraction of gallium in the gallium-indium liquid metal is 75.5% to 100%, and the mass fraction of indium is 0% to 24.5%.

3. The conductive hot melt adhesive with near-infrared light welding properties according to claim 1, characterized in that: The light source for optical welding is near-infrared light, the power of the light source is 0.5-2.0W, and the wavelength of the near-infrared light is 780-1100nm.

4. The conductive hot melt adhesive with near-infrared light welding properties according to claim 3, characterized in that: During the optical welding process, the distance between any light source and the conductive hot melt adhesive is 2.5-10.0 cm.

5. A method for preparing a conductive hot melt adhesive having near-infrared light welding properties, characterized in that: The following steps are involved: (1) Weigh the raw materials according to the mass percentages described in any one of claims 1 to 4; (2) Gallium-indium liquid metal, thioctic acid, and a multivalent crosslinking agent are mixed in an agate mortar and ground to obtain a precursor powder; (3) The precursor powder is heated to obtain a conductive hot melt adhesive with near-infrared light welding properties.

6. The method for preparing a conductive hot melt adhesive having near-infrared light welding properties according to claim 5, characterized in that: The grinding time in step (2) is 15-25 minutes.

7. The method for preparing a conductive hot melt adhesive having near-infrared light welding properties according to claim 5, characterized in that: The heating temperature in step (3) is 75-85°C, and the heating time is 25-35 minutes.

8. The method for preparing a conductive hot melt adhesive having near-infrared light welding properties according to claim 7, characterized in that: The heating is any one of an oil bath, a water bath, an air bath and a metal bath.

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