Near-infrared light cured conductive adhesive and preparation method thereof

Abstract

The invention discloses a near-infrared light cured conductive adhesive and a preparation method thereof, and belongs to the field of micro-nano electronic packaging and semiconductor materials. The problems that an existing conductive adhesive is high in curing temperature, long in curing time and poor in curing effect are solved. Silver-coated copper powder and silver nanowires serve as conductive filler and are mixed with epoxy acrylate resin, a reactive diluent, a photoinitiator, a thermal initiator, a defoaming agent and a flatting agent, grinding, defoaming and near-infrared light curing are conducted, and the conductive adhesive is obtained. The thermal initiator and the photoinitiator are combined, the near-infrared light is adopted for irradiation, the high-energy density of the near-infrared light directly permeates into the conductive adhesive film layer, the conductive adhesive film layer is heated at the same time and is not absorbed by the substrate, rapid curing of the conductive adhesive can be achieved, and when the radiation power is 120-300 W, the radiation time is 30-600 s and the irradiation frequency is 1-10 times, the conductive adhesive can be rapidly cured. And the cured conductive adhesive is low in volume resistance and high in bonding strength.

Description

Technical Field

[0001] The present invention belongs to the technical fields of micro-nano electronic packaging and semiconductor materials, and particularly relates to a near-infrared light-curable conductive adhesive and a preparation method thereof. Background Art

[0002] A conductive adhesive is a material used for micro-nano electronic packaging and interconnection of semiconductor components. Thermal curing and ultraviolet light curing are currently the two most commonly used curing technologies for conductive adhesives. A suitable curing method has a significant impact on the application of the conductive adhesive. The traditional thermal curing method is widely used, but it has problems such as high curing temperature, long curing time, and other complex and difficult-to-control curing processes. Ultraviolet light curing is fast, but ultraviolet light curing usually only acts on the surface layer and has limited effects on thicker materials or conductive adhesives that require deep curing. In the field of integrated circuit chip packaging, it is often necessary to use opaque conductive adhesives to meet specific functional requirements. In this case, traditional thermal curing and ultraviolet light curing may not achieve ideal curing effects, so alternative solutions need to be found. Therefore, it is necessary to develop a conductive adhesive with low curing temperature, short time, deep curing, and good curing effect. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a near-infrared light-curable conductive adhesive and a preparation method thereof.

[0004] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0005] One of the objectives of the present invention is to provide a preparation method of a near-infrared light-curable conductive adhesive, and the method includes:

[0006] (1) Add silver-coated copper powder to absolute ethanol, then add silver nanowires to obtain a dispersion liquid, and then perform the first ultrasonic oscillation. After the ultrasonic oscillation ends, add a coupling agent to the dispersion liquid, stir magnetically and then perform ultrasonic oscillation again, and then perform vacuum drying to obtain conductive fillers;

[0007] (2) Mix and stir epoxy acrylate resin, reactive diluent, photoinitiator, thermal initiator, defoamer, leveling agent with the conductive fillers obtained in (1) to obtain a mixed material, and then grind, degas, and cure the mixed material by near-infrared light to obtain a conductive adhesive.

[0008] Further defined, by weight, in (1), 50-80 parts of silver-coated copper powder, 0-10 parts of silver nanowires, and 1-3 parts of coupling agent.

[0009] Further defined, in (1), the mass ratio of silver-coated copper powder to absolute ethanol is 1:(5-15).

[0010] Further limitation: in (1), the magnetic stirring speed is 500 rpm and the time is 20 min.

[0011] Further limitation: in (1), the first ultrasonic oscillation time is 30 - 60 min and the second ultrasonic oscillation time is 30 - 60 min.

[0012] Further limitation: in (1), the vacuum drying temperature is 80 - 90 °C and the time is 2 - 3 h.

[0013] Further limitation: in (1), the particle size of the silver-coated copper powder is 5 - 20 μm, the thickness of the silver layer in the silver-coated copper powder is 5 - 10 μm, and the silver content in the silver-coated copper powder is 5 wt%.

[0014] Further limitation: in (1), the nanosilver wire has a diameter of 60 - 200 nm and a length of 50 - 80 μm.

[0015] Further limitation: in (1), the coupling agent is one or more of amino silane and epoxy silane.

[0016] Further limitation: by weight, in (2), there are 20 - 30 parts of epoxy acrylate resin, 5 - 15 parts of reactive diluent, 1 - 4 parts of photoinitiator, 1 - 4 parts of thermal initiator, 1 part of defoamer, and 1 part of leveling agent.

[0017] Further limitation: in (2), the epoxy acrylate resin is one or more of bisphenol A epoxy acrylate resin and modified epoxy acrylate; the reactive diluent is one or more of 2-hydroxyethyl methacrylate, isobornyl acrylate, isobornyl methacrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, and trimethylolpropane triacrylate; the photoinitiator is one or more of α-hydroxy ketone and phosphorus oxide; the thermal initiator is one or several of acyl peroxides and azo polymerization initiators; the leveling agent is one or several of silicone oil, polydimethylsiloxane, polyether-modified silicone, and polyester-modified silicone; the defoamer is one or several of polyether defoamers, silicone defoamers, and polyether-modified silicone defoamers.

[0018] Further limitation: in (2), the near-infrared curing parameters are: radiation power 120 - 300 W, radiation time 30 - 600 s, and irradiation times 1 - 10 times.

[0019] The second object of the present invention is to provide a near-infrared light-curable conductive adhesive prepared by the above method.

[0020] Further limitation: the volume resistivity of the conductive adhesive is 100 - 300 μΩ·cm and the bonding strength is 4 - 5 MPa.

[0021] The beneficial effects of the present invention are:

[0022] (1) In the present invention, epoxy acrylate resin is used as the organic matrix, and conductive filler is used as the inorganic matrix. The conductive fillers, silver-coated copper powder and silver nanowires, are treated with a coupling agent, which can form a bonding layer of organic matrix - coupling agent - inorganic matrix, helping to improve the compatibility between the conductive filler and the organic polymer resin.

[0023] (2) The coupling agent in the present invention is 1 - 3 parts, which can not only fully wet the conductive filler to improve conductivity, but also avoid the formation of an overly thick coating layer on the surface of the conductive filler, preventing the contact of the conductive filler and thus being disadvantageous to the enhancement of conductivity. The reactive diluent in the present invention is 5 - 15 parts, which can improve the viscosity of the conductive adhesive and control its curing shrinkage rate, balancing the processability and conductivity of the conductive paste before the curing of the conductive adhesive. The combination of flaky silver-coated copper powder and silver nanowires in the conductive adhesive can not only significantly reduce the resistivity, but also improve the shear strength. The silver nanowires can connect the micron-sized fillers that are relatively far apart to form a conductive path by utilizing their high aspect ratio characteristics. Reasonable control of the addition amount of silver nanowires can optimize both the conductive performance and shear strength of the conductive adhesive.

[0024] (3) The present invention simultaneously uses a free radical photoinitiator and a thermal initiator, and also realizes the rapid curing of the conductive adhesive by using near-infrared energy. Due to the residual epoxy groups in the epoxy acrylate resin during its synthesis process, a self-polymerization reaction occurs between the epoxy groups and the unsaturated bonds of itself under the action of near-infrared irradiation, causing crosslinking and curing. Moreover, the free radical photoinitiator decomposes to generate free radical active factors under the action of near-infrared irradiation, and the free radicals will initiate a chain reaction. In addition, the near-infrared light energy has a high energy density, and this high energy density directly penetrates into the uncured conductive adhesive. The conductive adhesive absorbs the near-infrared irradiation energy, causing the temperature to rise. The thermal curing agent decomposes under the action of heat, initiating a free radical reaction and promoting the transformation of the epoxy acrylate resin system from a low-molecular linear structure to a high-molecular three-dimensional network structure, which can cure the conductive adhesive more quickly and efficiently. In addition, under the irradiation of high irradiation power, local melting signs appear in the silver nanowires in the conductive adhesive, which helps to form sintering necks between the nanowires and contributes to the construction of the conductive network, resulting in a decrease in the resistivity of the conductive adhesive. When the radiation power is 120 - 300 W, the radiation time is 30 - 600 s, and the number of irradiation times is 1 - 10 times, the present invention can achieve the curing of the conductive adhesive, and its volume resistance is low, being 100 - 300 μΩ·cm, and the bonding strength is 4 - 5 MPa. Detailed Embodiments

[0025] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with the embodiments of the specification.

[0026] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways than those specifically described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0027] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an individual or alternative embodiment that is mutually exclusive with other embodiments.

[0028] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used, unless otherwise specified, are all conventional materials, reagents, methods, and instruments in this field, and those skilled in the art can obtain them through commercial channels.

[0029] In the following embodiments, the bisphenol A type epoxy acrylate resin used was purchased from Shanghai Yinchang New Materials Co., Ltd., with the product number YC3380, and the modified epoxy acrylate was purchased from Shanghai Yinchang New Materials Co., Ltd., with the product number YC2683; 2-hydroxyethyl methacrylate (CAS: 86877-9), isobornyl acrylate (CAS: 5888-33-5), tripropylene glycol diacrylate (CAS: 42978-66-5), 1,6-hexanediol diacrylate (CAS: 13048-33-4), trimethylolpropane triacrylate (CAS: 15625-89-5); KH-550 (CAS: 91930-2), KH-560 (CAS: 2530-83-8); 1-hydroxy-cyclohexyl-phenyl ketone was purchased from BASF SE, with the product number Irgacure184, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide was purchased from BASF SE, with the product number Irgacure 819; benzoyl peroxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and azobisisobutyronitrile was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; polyether-modified polydimethylsiloxane was purchased from BYK Additives (Shanghai) Co., Ltd., with the product number BYK330, and polyester-modified polysiloxane was purchased from BYK Additives (Shanghai) Co., Ltd., with the product number BYK310; glycerol polyoxypropylene ether was purchased from Jiangsu Haian Petrochemical Factory, with the product number GP330, and the modified organic polysiloxane mixture was purchased from Foshan Nanhai Datian Chemical Co., Ltd., with the product number JS-60; silver-coated copper powder was purchased from Nangong Jingrui Alloy Products Co., Ltd., with the product number JR-AgCu; silver nanowires were purchased from Bohuasi Nano Technology (Ningbo) Co., Ltd., with the product number Brofos-Ag-X015.

[0030] In the present invention, the composition of the conductive adhesive is designed for the following reasons:

[0031] Active diluent: It has the functions of solvent, rheology adjustment and curing cross-linking. The polymerizable double bonds contained in its molecular structure can participate in the photoinitiated reaction, affect the curing process of the conductive adhesive system, and regulate the curing shrinkage rate of the conductive adhesive to affect the electrical properties of the conductive adhesive.

[0032] Coupling agent: Improves the interface performance between epoxy acrylate resin and conductive filler, reduces interface voids and resistance, which is manifested as a decrease in the overall resistivity of the conductive adhesive and forms a strong bond between inorganic and organic.

[0033] Photoinitiator: A compound that absorbs near-infrared radiation energy, undergoes optical changes after excitation, and produces free radicals, cations, etc., thereby initiating monomer polymerization, cross-linking and curing.

[0034] Thermal initiator: Initiates decomposition to produce free radicals and initiates polymerization of monomers.

[0035] Leveling agent: It can effectively reduce the surface tension of the conductive paste before the conductive adhesive is cured, and improve its leveling and uniformity.

[0036] Defoaming agent: Reduce the surface tension of the conductive paste before the conductive adhesive is cured, prevent the formation of foam, or reduce or eliminate the original foam.

[0037] Silver-coated copper powder: It not only overcomes the easy oxidation property of copper powder, but also has the characteristics of good conductivity, high chemical stability, not easy to oxidize, and low price.

[0038] Nano silver wire: good conductivity, high aspect ratio, few contact points, etc.

[0039] Example 1

[0040] The near-infrared light-curable conductive adhesive prepared in this embodiment includes the following raw materials in parts by weight:

[0041] 15 parts of epoxy acrylate resin, 10 parts of active diluent, 1 part of coupling agent, 2 parts of photoinitiator, 3 parts of thermal initiator, 1 part of leveling agent, 1 part of defoaming agent, and 70 parts of silver-coated copper powder.

[0042] Among them, the epoxy acrylate resin is bisphenol A type epoxy acrylate resin, the active diluent is a mixture of hydroxyethyl methacrylate and 1,6-hexanediol diacrylate in a mass ratio of 2:1, the coupling agent is KH-550, the photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone, the thermal initiator is dibenzoyl peroxide, the leveling agent is polyether modified polydimethylsiloxane, the defoaming agent is glycerol polyoxypropylene ether, the particle size of the silver-coated copper powder is 5-20μm, the thickness of the silver layer is 5-10μm, and the silver content in the silver-coated copper powder is 5wt%.

[0043] The method for preparing the near-infrared light-curable conductive adhesive in this embodiment is as follows:

[0044] (1) Add 70 parts by weight of silver-coated copper powder to absolute ethanol. The mass ratio of absolute ethanol to silver-coated copper powder is 1:15. Ultrasonically vibrate for 30 min. After the ultrasonic vibration ends, add 1 part by weight of coupling agent KH550, and magnetically stir at a speed of 500 rpm for 20 min. Ultrasonically vibrate again for 30 min, and then dry in a vacuum drying oven at 80 °C for 3 h to obtain conductive filler;

[0045] (2) Thoroughly stir and disperse 15 parts by weight of bisphenol A epoxy acrylate resin, 10 parts by weight of reactive diluent, 2 parts by weight of 1-hydroxy-cyclohexyl-phenyl ketone, 3 parts by weight of dibenzoyl peroxide, 1 part by weight of polyether-modified polydimethylsiloxane, 1 part by weight of glycerol polyoxypropylene ether and the conductive filler obtained in (1) to obtain a mixed material. Then, grind and defoam the mixed material in sequence, and perform near-infrared light curing using a NIR ultrafast sintering system (Adphos PBT, Germany). The radiation power is 120 W, the radiation time is 120 s, and the number of irradiations is 5 times to obtain a conductive adhesive (10 mm × 10 mm × 0.2 mm).

[0046] Example 2

[0047] The near-infrared light-curable conductive adhesive prepared in this embodiment comprises the following raw materials in parts by weight:

[0048] 20 parts of epoxy acrylate resin, 8 parts of reactive diluent, 3 parts of coupling agent, 4 parts of photoinitiator, 4 parts of thermal initiator, 1 part of leveling agent, 1 part of defoaming agent, 60 parts of silver-coated copper powder, and 5 parts of silver nanowires.

[0049] Among them, the epoxy acrylate resin is a modified epoxy acrylate, the reactive diluent is a mixture of isobornyl acrylate and trimethylolpropane triacrylate with a mass ratio of 3:2, the coupling agent is KH-550, the photoinitiator is a mixture of 1-hydroxy-cyclohexyl-phenyl ketone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide with a mass ratio of 1:1, the thermal initiator is dibenzoyl peroxide, the leveling agent is polyether-modified polydimethylsiloxane, the defoaming agent is glycerol polyoxypropylene ether, the particle size of the silver-coated copper powder is 5 - 20 μm, the silver layer thickness is 5 - 10 μm, the silver content in the silver-coated copper powder is 5 wt%, the diameter of the silver nanowires is 100 - 120 nm, and the length is 50 - 80 μm.

[0050] The method for preparing the near-infrared light-curable conductive adhesive in this embodiment is as follows:

[0051] (1) Add 60 parts by weight of silver-coated copper powder to absolute ethanol. The mass ratio of absolute ethanol to silver-coated copper powder is 1:15. Then add 5 parts by weight of silver nanowires to obtain a dispersion. Ultrasonically vibrate for 30 min. After the ultrasonic vibration ends, add 3 parts by weight of coupling agent KH550, and magnetically stir at a speed of 500 rpm for 20 min. Ultrasonically vibrate again for 60 min. Subsequently, dry in a vacuum drying oven at 90 °C for 2 h to obtain a conductive filler;

[0052] (2) Thoroughly stir and disperse 20 parts by weight of modified epoxy acrylate, 8 parts by weight of reactive diluent, 4 parts by weight of photoinitiator, 4 parts by weight of dibenzoyl peroxide, 1 part by weight of polyether-modified polydimethylsiloxane, 1 part by weight of glycerol polyoxypropylene ether and the conductive filler obtained in (1) to obtain a mixed material. Then grind and defoam the mixed material in turn, and carry out near-infrared light curing using a NIR ultrafast sintering system (Adphos PBT, Germany). The radiation power is 180 W, the radiation time is 60 s, and the irradiation times are 2 times to obtain a conductive adhesive (10 mm × 10 mm × 0.2 mm).

[0053] Example 3

[0054] The near-infrared light-curable conductive adhesive prepared in this example comprises the following raw materials in parts by weight:

[0055] 25 parts of epoxy acrylate resin, 10 parts of reactive diluent, 3 parts of coupling agent, 2 parts of photoinitiator, 2 parts of thermal initiator, 1 part of leveling agent, 1 part of defoaming agent, 60 parts of silver-coated copper powder, and 10 parts of silver nanowires.

[0056] Among them, the epoxy acrylate resin is bisphenol A type epoxy acrylate resin, the reactive diluent is a mixture of isobornyl acrylate and 1,6-hexanediol diacrylate with a mass ratio of 2:1, the coupling agent is KH-550, the photoinitiator is a mixture of 1-hydroxy-cyclohexyl-phenyl ketone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide with a mass ratio of 1:1, the thermal initiator is azobisisobutyronitrile, the leveling agent is polyester-modified polysiloxane, the defoaming agent is a modified organopolysiloxane mixture, the particle size of the silver-coated copper powder is 5 - 20 μm, the silver layer thickness is 5 - 10 μm, the silver content in the silver-coated copper powder is 5 wt%, the diameter of the silver nanowires is 100 - 120 nm, and the length is 50 - 80 μm.

[0057] The method for preparing the near-infrared light-curable conductive adhesive in this example is as follows:

[0058] (1) Add 60 parts by weight of silver-coated copper powder to absolute ethanol. The mass ratio of absolute ethanol to silver-coated copper powder is 1:10. Then add 10 parts by weight of silver nanowires to obtain a dispersion. Ultrasonically vibrate for 30 min. After the ultrasonic vibration ends, add 3 parts by weight of coupling agent KH550, and magnetically stir at a speed of 500 rpm for 20 min. Ultrasonically vibrate again for 60 min. Subsequently, dry in a vacuum drying oven at 90 °C for 2 h to obtain a conductive filler;

[0059] (2) Thoroughly stir and disperse 25 parts by weight of bisphenol A epoxy acrylate resin, 10 parts by weight of reactive diluent, 2 parts by weight of photoinitiator, 2 parts by weight of azobisisobutyronitrile, 1 part by weight of polyester-modified polysiloxane, 1 part by weight of modified organopolysiloxane mixture and the conductive filler obtained in (1) to obtain a mixed material. Then grind and defoam the mixed material in turn, and carry out near-infrared light curing using a NIR ultrafast sintering system (Adphos PBT, Germany). The radiation power is 240 W, the radiation time is 60 s, and the number of irradiations is 1 time to obtain a conductive adhesive (10 mm × 10 mm × 0.2 mm).

[0060] Example 4

[0061] The near-infrared light-curable conductive adhesive prepared in this example comprises the following raw materials in parts by weight:

[0062] 15 parts of epoxy acrylate resin, 5 parts of reactive diluent, 3 parts of coupling agent, 2 parts of photoinitiator, 2 parts of thermal initiator, 1 part of leveling agent, 1 part of defoaming agent, 80 parts of silver-coated copper powder.

[0063] Among them, the epoxy acrylate resin is bisphenol A epoxy acrylate resin, the reactive diluent is a mixture of isobornyl acrylate and 1,6-hexanediol diacrylate in a mass ratio of 2:1, the coupling agent is KH-550, the photoinitiator is a mixture of 1-hydroxy-cyclohexyl-phenyl ketone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide in a mass ratio of 1:1, the thermal initiator is a mixture of azobisisobutyronitrile and dibenzoyl peroxide in a mass ratio of 1:1, the leveling agent is polyester-modified polysiloxane, the defoaming agent is a modified organopolysiloxane mixture, the particle size of the silver-coated copper powder is 5 - 20 μm, the silver layer thickness is 5 - 10 μm, and the silver content in the silver-coated copper powder is 5 wt%.

[0064] The method for preparing the near-infrared light-curable conductive adhesive in this example is as follows:

[0065] (1) Add 80 parts by weight of silver-coated copper powder to absolute ethanol. The mass ratio of absolute ethanol to silver-coated copper powder is 1:10. Ultrasonically vibrate for 30 min. After the ultrasonic vibration ends, add 3 parts by weight of coupling agent KH550, and magnetically stir at a speed of 500 rpm for 20 min. Ultrasonically vibrate again for 60 min, and then dry in a vacuum drying oven at 90 °C for 2 h to obtain a conductive filler;

[0066] (2) Thoroughly stir and disperse 15 parts by weight of bisphenol A epoxy acrylate resin, 5 parts by weight of reactive diluent, 2 parts by weight of photoinitiator, 2 parts by weight of azobisisobutyronitrile, 1 part by weight of polyester-modified polysiloxane, 1 part by weight of modified organopolysiloxane mixture and the conductive filler obtained in (1) to obtain a mixed material. Then, grind and defoam the mixed material in sequence, and perform near-infrared light curing using a NIR ultrafast sintering system (Adphos PBT, Germany). The radiation power is 300 W, the radiation time is 30 s, and the irradiation times is 2 times to obtain a conductive adhesive (10 mm × 10 mm × 0.2 mm).

[0067] Comparative Example 1

[0068] The near-infrared light-curable conductive adhesive prepared in this comparative example comprises the following raw materials in parts by weight:

[0069] 30 parts of epoxy acrylate resin, 10 parts of reactive diluent, 3 parts of coupling agent, 2 parts of photoinitiator, 2 parts of thermal initiator, 1 part of leveling agent, 1 part of defoaming agent, and 50 parts of silver-coated copper powder.

[0070] Among them, the epoxy acrylate resin is bisphenol A epoxy acrylate resin, the reactive diluent is a mixture of isobornyl acrylate and 1,6-hexanediol diacrylate with a mass ratio of 2:1, the coupling agent is KH550, the photoinitiator is a mixture of 1-hydroxy-cyclohexyl-phenyl ketone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide with a mass ratio of 1:1, the thermal initiator is a mixture of azobisisobutyronitrile and dibenzoyl peroxide with a mass ratio of 1:1, the leveling agent is polyester-modified polysiloxane, the defoaming agent is a modified organopolysiloxane mixture, the particle size of the silver-coated copper powder is 5 - 20 μm, the silver layer thickness is 5 - 10 μm, and the silver content in the silver-coated copper powder is 5 wt%.

[0071] The method for preparing the near-infrared light-curable conductive adhesive in this comparative example is as follows:

[0072] (1) Add 50 parts by weight of silver-coated copper powder to absolute ethanol. The mass ratio of absolute ethanol to silver-coated copper powder is 1:10. Ultrasonically vibrate for 30 min. After the ultrasonic vibration ends, add 3 parts by weight of coupling agent KH550, and magnetically stir at a speed of 500 rpm for 20 min. Ultrasonically vibrate again for 60 min, and then dry in a vacuum drying oven at 90 °C for 2 h to obtain a conductive filler;

[0073] (2) 30 parts by weight of bisphenol A epoxy acrylate resin, 10 parts by weight of reactive diluent, 2 parts by weight of photoinitiator, 2 parts by weight of azobisisobutyronitrile, 1 part by weight of polyester-modified polysiloxane, and 1 part by weight of modified organopolysiloxane mixture were thoroughly stirred and dispersed with the conductive filler obtained in (1) to obtain a mixed material. Then, the mixed material was ground and degassed in sequence, and near-infrared light curing was carried out using a NIR ultrafast sintering system (Adphos PBT, Germany) with a radiation power of 300 W, a radiation time of 30 s, and an irradiation times of 2 times to obtain a conductive adhesive (10 mm × 10 mm × 0.2 mm).

[0074] Performance evaluation

[0075] The volume resistance and shear strength of the conductive adhesives prepared in Examples 1-4 and Comparative Example 1 were tested as follows.

[0076] 1. Volume resistance: The resistance of the conductive adhesives prepared in Examples 1-4 and Comparative Example 1 was tested by the four-point probe method using an ST2263 double-electrode digital four-probe tester, and the volume resistance was calculated. The results are shown in Table 1 below.

[0077] 2. Shear strength: According to the methods of Examples 1-4 and Comparative Example 1 respectively, the slurries obtained by degassing in step (2) of each example and comparative example were printed on a glass sheet (10 mm × 10 mm × 3 mm) to form a glue film with a size of 10 mm × 10 mm × 0.2 mm. A glass sheet (5 mm × 5 mm × 3 mm) was placed on the glue film, and a "sandwich" structure was formed by two glass sheets and one glue film. After near-infrared light curing, it was tested using a ZD / WDW-05 single-arm electronic universal testing machine (Zhuode Instruments, Shanghai), and the test mode was shear mode with a thrust rate of 0.5 cm·min -1 . Although the 5 test cases for testing the shear strength first coated the degassed slurry on the glass sheet to form a glue film, and then formed a "sandwich" structure due to another glass sheet and then carried out near-infrared light curing, which was slightly different from the steps of Examples 1-4 and Comparative Example 1, the purpose was to test the shear strength of the conductive adhesives in Examples 1-4 and Comparative Example 1, and the parameters involved in the shear strength test were the same as those in Examples 1-4 and Comparative Example 1. Its essence was to test the shear strength of the conductive adhesives prepared in Examples 1-4 and Comparative Example 1, and the test results are shown in Table 2 below.

[0078] Table 1

[0079] Experimental group Example 1 Example 2 Example 3 Example 4 Comparative example 1 Irradiation power / W 120 180 240 300 300 Irradiation time / s 120 60 60 30 30 Irradiation times / times 5 2 1 2 2 Volume resistance (μΩ·cm) 220 143 97 164 <![CDATA[4.1×10 8 >

[0080] Table 2

[0081] Experimental group Example 1 Example 2 Example 3 Example 4 Comparative example 1 Irradiation power / W 120 180 240 300 300 Irradiation time / s 120 60 60 30 30 Irradiation times / times 5 2 1 2 1 Shear strength (MPa) 4.7 4.3 4.9 5.3 5.3

[0082] As described above, it is only the preferred specific implementation manner of the present invention. However, the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a near-infrared light-cured conductive adhesive, characterized in that: The method includes: (1) adding silver-coated copper powder to anhydrous ethanol, and then adding nano silver wires to obtain a dispersion, ultrasonically vibrating the dispersion, adding a coupling agent to the dispersion after the ultrasonic vibration, magnetically stirring and ultrasonically vibrating the dispersion again, and then vacuum drying to obtain a conductive filler; (2) Mixing and stirring the epoxy acrylate resin, reactive diluent, photoinitiator, thermal initiator, defoamer, leveling agent and the conductive filler obtained in (1) to obtain a mixed material, and then grinding, degassing and near-infrared curing the mixed material in sequence to obtain a conductive adhesive.

2. The preparation method according to claim 1, characterized in that: By weight, (1) 50-80 parts of silver-coated copper powder, 0-10 parts of nano silver wire, and 1-3 parts of coupling agent.

3. The preparation method according to claim 1, characterized in that: (1) The mass ratio of silver-coated copper powder to anhydrous ethanol is 1:(5-15).

4. The preparation method according to claim 1, characterized in that: (1) The vacuum drying temperature is 80-90°C and the time is 2-3 hours.

5. The preparation method according to claim 1, characterized in that: (1) The particle size of the silver-coated copper powder is 5-20 μm, the thickness of the silver layer in the silver-coated copper powder is 5-10 μm, and the silver content in the silver-coated copper powder is 5wt%; the particle size of the nano silver wire is 60-200 nm and the length is 50-80 μm.

6. The preparation method according to claim 1, characterized in that: The coupling agent in (1) is one or more of aminosilane and epoxysilane.

7. The preparation method according to claim 1, characterized in that: In terms of weight, (2) comprises 20-30 parts of epoxy acrylate resin, 5-15 parts of active diluent, 1-4 parts of photoinitiator, 1-4 parts of thermal initiator, 1 part of defoamer and 1 part of leveling agent.

8. The preparation method according to claim 1, characterized in that: (2) wherein the epoxy acrylate resin is one or more of bisphenol A epoxy acrylate resin and modified epoxy acrylate; the active diluent is one or more of hydroxyethyl methacrylate, isobornyl acrylate, isobornyl methacrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, and trimethylolpropane triacrylate; the photoinitiator is one or more of α-hydroxy ketone and phosphorus oxide; the thermal initiator is one or more of acyl peroxide and azo polymerization initiator; the leveling agent is one or more of silicone oil, polydimethylsiloxane, polyether-modified organosiloxane, and polyester-modified organosiloxane; the defoamer is one or more of polyether-type defoamer, silicone-type defoamer, and polyether-modified silicone defoamer.

9. The preparation method according to claim 1, characterized in that: (2) Medium photon curing time is 30-600s.

10. A near-infrared light-cured conductive adhesive, characterized in that: The method is prepared by any one of claims 1 to 9.