CN115401196B - Bimetal material and preparation method thereof, bimetal paste and interconnection method - Google Patents

Bimetal material and preparation method thereof, bimetal paste and interconnection method Download PDF

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CN115401196B
CN115401196B CN202110593696.3A CN202110593696A CN115401196B CN 115401196 B CN115401196 B CN 115401196B CN 202110593696 A CN202110593696 A CN 202110593696A CN 115401196 B CN115401196 B CN 115401196B
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CN115401196A (en
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张昱
赖海其
崔成强
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Ji Hua Laboratory
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors

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Abstract

The invention discloses a bimetal material, a preparation method thereof, a bimetal paste and an interconnection method. The bimetal material comprises nano metal particles and micron metal particles, the bimetal material is of a core-shell structure, the micron metal particles are used as cores, the nano metal particles are used as shell layers, and the nano metal particles are coated on the micron metal particles. The bi-metallic material may be applied to interconnect processes of microelectronic packages.

Description

Bimetal material and preparation method thereof, bimetal paste and interconnection method
Technical Field
The invention relates to the technical field of preparation of microelectronic packaging interconnection materials, and mainly relates to a bimetal material, a preparation method thereof, a bimetal paste and an interconnection method.
Background
With the development trend of light, thin, short and small electronic products and the continuous update of microelectronic technologies, electronic packaging technologies are gradually entering into the ultra-high-speed development period due to the characteristics of high density and high performance, and the requirements on interconnection performance are also higher.
Today, micro-nano copper powder is a representative of a novel interconnect material with the advantages of higher thermal conductivity and electrical conductivity, lower melting point and cost, excellent high temperature resistance, and the like. However, micro-nano copper is polarized and easily oxidized, and the generated copper oxide has no conductivity, so that the electrical performance of the package interconnection is affected.
In order to solve the problem of poor oxidation resistance of micro-nano copper particles, researchers have developed an oxidation resistant particle with a copper-silver bimetallic structure. The copper-silver bimetallic core-shell nano-particle has the oxidation resistance of nano-silver and the electromigration resistance of nano-copper, the core-shell structure plays the advantages of nano-copper and nano-silver, overcomes the disadvantages of nano-copper and nano-silver, and is a representative of a more ideal novel packaging interconnection material.
The main methods for preparing the micro-nano bimetallic core-shell particles at present comprise a melting atomization method, a chemical reduction method, a displacement method and a displacement and chemical deposition composite method, wherein the melting atomization method has high requirements on process equipment, and micro-nano particles are difficult to prepare, so that the application range is not very wide. The main principle of the three methods is that silver ions in the solution are reduced into silver simple substance through electrons, and the silver simple substance is deposited on the surface of copper particles, so that the operation is convenient and controllable, and the particles with uniform relative components and uniform granularity can be obtained. The chemical reduction method adopts a reducing agent to directly reduce metal ions to prepare bimetallic core-shell particles, and generally the method can cause instability of silver plating solution due to quicker reaction, especially when a strong reducing agent is used, thereby influencing the coating effect. The replacement method adopts copper powder to replace silver ions in the solution, but the method generally obtains silver coated copper powder with a stippling structure in the silver plating process, and has the advantages of high replacement reaction speed and difficult control of the reaction. Therefore, many scholars adopt a method combining a displacement method and chemical deposition, so that the defects of the two methods are overcome, but the complex reaction system and the excessive influence factors are brought.
Disclosure of Invention
In view of the shortcomings of the prior art, the invention aims to provide a bimetal material, a preparation method thereof, a bimetal paste and an interconnection method, and aims to solve the problems that the particle size is difficult to control and the wrapping is uneven in the continuous preparation of a micro-nano bimetal core-shell material.
The technical scheme of the invention is as follows:
the preparation method of the bimetallic material comprises the following steps:
a) Dispersing nano metal particles and micron metal particles in the solution respectively to obtain a nano metal solution and a micron metal solution;
b) Adding a cationic surfactant into the micrometer metal solution to make the surfaces of the micrometer metal particles positively charged, adding an anionic surfactant into the nanometer metal solution, adding a proper amount of OH-ions into the nanometer metal solution, and adjusting the pH value to 7-8 to make the nanometer metal solution slightly alkaline to make the surfaces of the nanometer metal particles negatively charged; or adding an anionic surfactant into the micrometer metal solution, adding a proper amount of OH-ions into the micrometer metal solution, adjusting the pH value to 7-8 to enable the micrometer metal solution to have weak alkalinity, enabling the surfaces of micrometer metal particles to be negatively charged, and adding a cationic surfactant into the nanometer metal solution to enable the surfaces of the nanometer metal particles to be positively charged;
c) Respectively carrying out water bath heating on the micrometer metal solution and the nanometer metal solution to enable the temperature to reach 60-70 ℃;
d) Mixing the micrometer metal solution and the nanometer metal solution, stirring to make the micrometer metal solution and the nanometer metal solution fully contact, reducing the temperature of the solution to 40-50 ℃ at the same time, and controlling the reaction time to be 30-45 min;
e) And centrifuging, cleaning and drying particles in the bimetallic solution.
The preparation method of the bimetal material comprises the steps that in the micrometer metal solution, the concentration of micrometer metal particles is 50-100 mg/mL; in the nano metal solution, the concentration of nano metal particles is 150-350 mg/mL; the mass ratio of the micrometer metal particles to the nanometer particles is 1: (2-4).
The preparation method of the bimetallic material comprises the following steps of b), wherein the molar concentration of the cationic surfactant in the metal solution is 0.01-0.05 mol/L; the molar concentration of the anionic surfactant in the metal solution is 0.01-0.05 mol/L;
when the cationic surfactant is added into the micrometer metal solution and the anionic surfactant is added into the nanometer particle solution, the molar concentration ratio of the cationic surfactant to the anionic surfactant is 1 (2-3); when an anionic surfactant is added into the micrometer metal solution and a cationic surfactant is added into the nanometer particle solution, the molar concentration ratio of the anionic surfactant to the cationic surfactant is 1 (2-3).
The preparation method of the bimetal material comprises the steps of in the step d), ultrasonic oscillation and mechanical stirring; the ultrasonic power of ultrasonic oscillation is 80-200W, the ultrasonic frequency is 40 KHz-100 KHz, and the mechanical stirring rotating speed is 500-1000 rpm.
The preparation method of the bimetal material, wherein in the step d), the process of mixing the micrometer metal solution and the nanometer metal solution specifically comprises the following steps:
adding one-fourth to one-half of the volume of nano metal solution into a first container, carrying out ultrasonic oscillation and mechanical stirring on the solution to enable nano metal to be uniformly suspended in the solution, placing the container on a magnetic panel, standing, and distributing nano metal particles on the bottom surface of the container under the action of magnetic force;
carrying out ultrasonic oscillation and mechanical stirring on all the micrometer metal solutions in other containers to uniformly suspend the micrometer metal in the solutions, then adding the solutions into a first container, standing, and distributing micrometer particles on the nanometer metal particles under the action of magnetic force;
carrying out ultrasonic oscillation and mechanical stirring on the rest nano metal solution in other containers to uniformly suspend nano metal in the solution, then adding the solution into a first container, standing, and distributing nano particles on the micrometer metal particles under the action of magnetic force;
the magnetic panel is removed.
In the preparation method of the bimetal material, in the step e), the rotating speed of centrifugal operation is 12000-15000 rpm, and the centrifugal time is 2-4 min.
The preparation method of the bimetal material comprises the steps that micrometer metal particles are selected from one of copper, platinum, palladium, gold, silver, tin, zinc and aluminum, and the particle size of the micrometer metal particles is 1-50 mu m; the nano metal particles are selected from one of iron, gold, silver, tin, platinum and palladium, and the particle size of the nano metal particles is 2 nm-500 nm;
the solution is absolute ethanol, ultrapure water, ethylene glycol, isopropanol or glycerol.
The bimetal material is prepared by adopting the preparation method of the bimetal material; the bimetal material comprises nano metal particles and micron metal particles, the bimetal material is of a core-shell structure, the micron metal particles are used as cores, the nano metal particles are used as shell layers, and the nano metal particles are coated on the micron metal particles.
The bimetal paste comprises, by mass, 10% -20% of a soldering flux and 80% -90% of the bimetal material.
An interconnection method, comprising the steps of:
coating the bimetallic paste on a metal substrate, and introducing 5%H 2 Hot-pressed sintering is carried out with mixed gas of 95 percent Ar;
in the hot pressing sintering process, the sintering temperature is 260-350 ℃ and the sintering pressure is 2-5 MPa.
The beneficial effects are that: according to the invention, the bimetal particles are subjected to surface modification, and mixed in a solution to enable electrostatic adsorption to form a bimetal particle solution with a coating structure, and the bimetal particles are separated to obtain the bimetal material. The bimetallic core-shell material can be applied to the interconnection process of microelectronic packaging.
Drawings
FIG. 1 is a schematic diagram of an assembled bimetallic particle structure in accordance with the present invention.
Fig. 2 is an XRD diffractogram after sintering of the copper silver bi-metallic particles.
Description of the reference numerals: 1. micrometer metal particles; 2. nano-metal particles.
Detailed Description
The invention provides a bimetal material, a preparation method thereof, a bimetal paste and an interconnection method, and aims to make the purposes, the technical scheme and the effects of the invention clearer and more definite, and the invention is further described in detail below. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. In order to simplify the present disclosure, components and arrangements of specific examples are described below. They are, of course, merely examples and are not intended to limit the invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, which are for the purpose of brevity and clarity, and which do not themselves indicate the relationship between the various embodiments and/or arrangements discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the application of other processes and/or the use of other materials.
The invention provides a preparation method of a high-stability bimetallic material, which comprises the following steps:
a) And dispersing the nano metal particles 2 and the micro metal particles 1 in the solution respectively to obtain a nano metal solution and a micro metal solution.
In step a), the nano-sized metal particles 2 and the micro-sized metal particles 1 may be self-made or commercially available.
The solution may be selected from absolute ethanol, ultrapure water, ethylene glycol, isopropanol, glycerol, or the like.
In the preferred embodiment of the invention, in the micrometer metal solution, the concentration of the micrometer metal particles 1 is 50-100 mg/mL; in the nano metal solution, the concentration of nano metal particles 2 is 150-350 mg/mL; the mass ratio of the micrometer metal particles 1 to the nanometer particles is 1: (2-4). In the preferred embodiment of the present invention, the concentration and amount of nano-metal particles are higher than those of micro-metal particles 1, in order to increase the coating rate of nano-metal particles 2 on the surface of micro-metal particles 1.
The micrometer metal particles 1 may be selected from one of copper, platinum, palladium, gold, silver, tin, zinc, and aluminum as the core particles, and the micrometer core particles are required to have excellent electrical conductivity and thermal conductivity, and have a size ranging from 1 μm to 50 μm. The nano metal particles 2 can be selected from one of iron, gold, silver, tin, platinum and palladium as shell particles, and the nano shell metal particles have strong oxidation resistance and stability, and the size range is 2-500 nm.
b) Adding a cationic surfactant into the micrometer metal solution to make the surfaces of the micrometer metal particles 1 positively charged, adding an anionic surfactant into the nanometer metal solution, adding a proper amount of OH-ions into the nanometer metal solution, and adjusting the pH value to 7-8 to make the nanometer metal solution slightly alkaline to make the surfaces of the nanometer metal particles 2 negatively charged;
or adding an anionic surfactant into the micrometer metal solution, adding a proper amount of OH-ions into the micrometer metal solution, adjusting the pH value to 7-8 to enable the micrometer metal solution to have weak alkalinity, enabling the surfaces of the micrometer metal particles 1 to be negatively charged, and adding a cationic surfactant into the nanometer metal solution to enable the surfaces of the nanometer metal particles 2 to be positively charged.
In step b), a cationic surfactant or an anionic surfactant is added to the micrometer metal solution to generate more active sites on the surface of micrometer metal particles 1, so that the surface of micrometer metal particles 1 is positively or negatively charged. And adding an anionic surfactant or a cationic surfactant into the nanoparticle solution to generate more active sites on the surfaces of the nano metal particles 2, so that the surfaces of the nano metal particles 2 are negatively or positively charged.
In the embodiment of the present invention, there is no particular limitation on the cationic surfactant, and the cationic surfactant may be one of an amine salt or polyamine, a quaternary ammonium salt, a heterocyclic type, or an organic acid. The amine salt or polyamine may be polyethyleneimine, polymaleimide, primary amine salt (octadecylamine hydrochloride, etc.), secondary amine salt (dioctadecyl amine hydrochloride, etc.), tertiary amine salt (N, N-dimethyloctadecylamine hydrochloride, etc.), etc. The quaternary ammonium salt can be cetyl trimethyl ammonium bromide, quaternized polyacrylamide, polyvinyl pyridine salt or polydimethyl amine epichlorohydrin, etc. The heterocyclic ring may be a morpholine ring, a pyridine ring, an imidazole ring, a piperazine ring, a quinoline ring, or the like. The organic acid may be formic acid, acetic acid, propionic acid, butyric acid, caprylic acid, adipic acid, or the like.
In the embodiment of the present invention, there is no particular limitation on the anionic surfactant, and the anionic surfactant may be one of carboxylate, sulfonate, sulfate, phosphate or organic amine. The carboxylate may be polyacrylic acid and its copolymer, butenoic acid and its copolymer, acrylic acid maleic anhydride copolymer, sodium pectate, sodium alginate, etc. The sulfonate may be sodium dodecyl sulfonate, lignin sulfonate, polystyrene sulfonate, etc. The sulfate salt can be sodium fatty alcohol sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, condensed alkyl phenyl ether sulfate, etc. The phosphate salt may be a monoester, a diester, or the like. The organic amine may be aliphatic amine, alcohol amine, amide, alicyclic amine, etc.
In the embodiment of the invention, the molar concentration of the cationic surfactant in the metal solution is 0.01-0.05 mol/L; the molar concentration of the anionic surfactant in the metal solution is 0.01-0.05 mol/L. Preferably, in order to increase the coating rate of the nano metal particles 2 on the surface of the micrometer metal particles 1, the number of the nano metal particles 2 is more than that of the micrometer metal particles 1, and in order to ensure that all the nano particles are positively or negatively charged, when the cationic surfactant is added into the micrometer metal solution and the anionic surfactant is added into the nanometer particle solution, the molar concentration ratio of the cationic surfactant to the anionic surfactant is 1 (2-3); when an anionic surfactant is added into the micrometer metal solution and a cationic surfactant is added into the nanometer particle solution, the molar concentration ratio of the anionic surfactant to the cationic surfactant is 1 (2-3).
c) And respectively carrying out water bath heating on the micrometer metal solution and the nanometer metal solution to ensure that the temperature reaches 60-70 ℃.
In the step c), the internal energy of the solution is increased by heating, so that the diffusion movement of the particles is more obvious, the dispersibility of the micrometer metal solution and the nanometer metal solution is increased, and the nanometer metal particles and the micrometer metal particles are more fully self-assembled.
Through steps b) and c), the surface of the bimetallic particles is modified, the pH value and the temperature of the solution are regulated, so that the surfaces of the kernel particles (namely, the micron metal particles 1) and the carrier particles (namely, the nanometer metal particles 2) have opposite charges, and then the two metal particles are self-assembled under the combined action of non-covalent intermolecular forces such as electrostatic adsorption, hydrogen bonds, van der Waals forces and the like, so that the nanometer metal particles 2 are deposited on the surfaces of the micron metal particles 1 to spontaneously form a stable and compact coating structure, as shown in figure 1.
d) Mixing the micrometer metal solution and the nanometer metal solution, stirring to make the micrometer metal solution and the nanometer metal solution fully contact, reducing the temperature of the solution to 40-50 ℃ at the same time, and controlling the reaction time to 30-45 min.
In the step d), the temperature is reduced after the two solutions are mixed so as to reduce the internal energy of the reaction solution and slow down disordered diffusion among particles so as to enhance the charge adsorption effect among the particles, and the nano metal particles and the micro metal particles can be self-assembled under the action of the cationic surfactant.
In step d), preferably, the stirring process includes ultrasonic vibration and mechanical stirring. Further, the ultrasonic power of ultrasonic oscillation is 80-200W, the ultrasonic frequency is 40 KHz-100 KHz, and the mechanical stirring rotating speed is 500-1000 rpm. In this step, the nanoparticles are uniformly and densely packed in the core microparticles through a series of physical methods such as ultrasonic agitation, through repeated interparticle actions.
In a preferred embodiment of the present invention, "mixing a micrometer metal solution with a nanometer metal solution" specifically includes the steps of:
adding one-fourth to one-half of the volume of nano metal solution into a first container, carrying out ultrasonic oscillation and mechanical stirring on the solution to enable nano metal to be uniformly suspended in the solution, placing the container on a magnetic panel, standing, and distributing nano metal particles on the bottom surface of the container under the action of magnetic force;
carrying out ultrasonic oscillation and mechanical stirring on all the micrometer metal solutions in other containers to uniformly suspend the micrometer metal in the solutions, then adding the solutions into a first container, standing, and distributing micrometer particles on the nanometer metal particles under the action of magnetic force;
carrying out ultrasonic oscillation and mechanical stirring on the rest nano metal solution in other containers to uniformly suspend nano metal in the solution, then adding the solution into a first container, standing, and distributing nano particles on the micrometer metal particles under the action of magnetic force;
the magnetic panel is removed.
In the scheme, the upper surface and the lower surface of the microparticles are firstly adsorbed and assembled with most of the nanoparticles under the combined action of magnetic intervention, electrostatic adsorption, hydrogen bond, van der Waals force and other non-covalent intermolecular forces in advance, and finally the rest of the nanoparticles which are not adsorbed on the surfaces of the microparticles are freely assembled with the microparticles through ultrasonic vibration and mechanical stirring. Therefore, compared with a mode of directly mixing and freely assembling two liquids, the coating rate and the compactness of the nano particles to the micro particles can be better improved.
e) And centrifuging, cleaning and drying particles in the bimetal solution to obtain the bimetal material.
In step e), the rotational speed of the centrifugation is 12000-15000 rpm and the centrifugation time is 2-4 min.
The preparation method of the bimetallic material provided by the invention can be used for coating metal particles with various sizes (nano-size and micron-size). The bimetal material prepared by the preparation method of the bimetal material provided by the invention has the advantages of more continuous and uniform coating structure, easy control of the coating process, simple operation process and wide applicability. Preferably, the invention adopts the combination of micron-sized copper particles and nanometer-sized silver particles, and enables the copper particles and the nanometer-sized silver particles to form a compact cladding structure, thereby having higher oxidation resistance and greatly improving the oxidation resistance and stability of the bimetallic material. According to the scheme, micron particles are innovatively adopted as core particles, anti-oxidation nano particles are adopted as shell particles, a self-assembly method is used for preparing a bimetal core-shell structure, and the nano particles can form denser coating on the core particles by carrying out surface modification on the two metal particles. The micron particles have stronger oxidation resistance, and the coating of the shell particles further improves the oxidation resistance and stability of the bimetal material, so that the stability and the working reliability of the bimetal material after sintering are greatly improved.
The invention also provides a bimetal material, which is prepared by adopting the preparation method of the bimetal material; the bimetal material comprises nano metal particles and micron metal particles, the bimetal material is of a core-shell structure, the micron metal particles are used as cores, the nano metal particles are used as shell layers, and the nano metal particles are coated on the micron metal particles.
The invention also provides a bimetal paste, which comprises 80-90% of the bimetal material and 10-20% of soldering flux according to mass percent. And adding soldering flux into the bimetal material, and preparing the bimetal paste by mechanical stirring, ultrasonic vibration and mechanical mixing.
The soldering flux comprises, by mass, 15% -20% of an activating agent and 80% -85% of an organic solvent. The activator is selected from one of rosin, organic halide (halogen acid salt of fatty amine), organic acid (carboxylic acid and sulfonic acid), and organic amine (methylamine, dimethylamine and trimethylamine); the organic solvent is selected from one of monohydric alcohol (ethanol, 2-butanol), dihydric alcohol (ethylene glycol, propylene glycol) and polyhydric alcohol (glycerol).
The invention also provides an interconnection method, wherein the bimetallic paste is coated on a metal substrate and is introduced with 5%H 2 Hot-pressing sintering is carried out with mixed gas of 95% Ar, the sintering temperature is set to 260-350 ℃, and the sintering pressure is set to 2-5 MPa, so that the highly stable bimetal core-shell sintered body is prepared. Ultrasonic assisted sintering is applied during the sintering process. After sintering, the nano metal particles are tightly adhered to the surfaces of the micro metal particles, and a bimetal core-shell structure with the coating rate of 70% -95% is produced, so that a compact sintered body with good oxidation resistance and high stability is formed.
The invention is further illustrated by the following specific examples.
Example 1
a) Commercial nano silver particles and micron copper particles are dispersed in ultrapure water to obtain a nano silver solution and a micron copper solution. The concentration of the micron copper particles in the solution is regulated to be 100mg/mL, and the concentration of the nanometer silver particles is regulated to be 200mg/mL. The particle size of the nano silver particles is 60nm, and the particle size of the micron copper particles is 1um.
b) Cetyl trimethyl ammonium bromide was added to the microparticle solution and its molar concentration was adjusted to 0.05mol/L to positively charge the surface of the copper microparticles. Adding sodium dodecyl sulfate into the nano-particle solution, regulating the molar concentration to be 0.1mol/L, adding a proper amount of OH-ions into the solution, regulating the PH to be 7-8 to ensure that the solution has weak alkalinity, and leading the surfaces of the nano-silver particles to be negatively charged.
c) And respectively carrying out water bath heating on the micrometer copper solution and the nanometer silver solution to ensure that the temperature reaches 60 ℃.
d) Mixing the micrometer copper solution and the nanometer silver solution, carrying out ultrasonic oscillation and mechanical stirring, setting the ultrasonic power of ultrasonic oscillation to be 100W, the ultrasonic frequency to be 40KHz, and the mechanical stirring rotating speed to be 900rpm. Simultaneously, the temperature of the solution is reduced to 50 ℃, so that two particles are self-assembled, and the reaction time is controlled to be 30min.
e) The particles in the bimetallic solution were centrifuged at 12000rmp for 2min. And (5) after centrifugation, cleaning and drying to obtain the bimetal material.
f) 80% of a bimetal material and 20% of a soldering flux (the soldering flux comprises 15% of rosin and 85% of glycerol according to the weight percentage) are added according to the weight percentage, and mechanical stirring, ultrasonic vibration and mechanical mixing are carried out to prepare the bimetal paste.
g) And (3) coating the bimetal paste on a copper substrate to prepare a sintering sample, performing hot-pressing sintering, setting the sintering temperature to 260 ℃ and the sintering pressure to 2MPa, and preparing the highly stable bimetal core-shell sintered body.
The bimetal obtained in example 1 was tested and had a particle size of 1.1. Mu.m. The bimetallic core-shell sintered body obtained in example 1 was examined, and the results were as follows:
FIG. 2 is an XRD diffraction pattern of sintered Cu-Ag bimetallic particles, as shown in FIG. 2The particles have no obvious oxidation peak after sintering and only contain diffraction peaks of copper and silver simple substances, so that the self-assembled bimetallic particles have better oxidation resistance, the micron copper particles of the inner core are not oxidized, and the self-assembled bimetallic particles also have higher coating rate. The bimetallic core-shell sintered body has the resistivity of 1.65 x 10 -7 Ωm。
Example 2
a) Commercial nano platinum particles and micron copper particles are dispersed in absolute ethyl alcohol to obtain nano platinum solution and micron copper solution. The concentration of the micron copper particles in the solution is regulated to be 100mg/mL, and the concentration of the nanometer platinum particles is regulated to be 200mg/mL. The particle size of the nano platinum particles is 50nm, and the particle size of the micron copper particles is 2um.
b) Cetyl trimethyl ammonium bromide was added to the microparticle solution and its molar concentration was adjusted to 0.05mol/L to positively charge the surface of the copper microparticles. Adding sodium dodecyl sulfate into the nano-particle solution, regulating the molar concentration to be 0.15mol/L, adding a proper amount of OH-ions into the solution, regulating the PH to be 7-8 to ensure that the solution has weak alkalinity, and leading the surfaces of the nano-platinum particles to be negatively charged.
c) And respectively carrying out water bath heating on the micrometer copper solution and the nanometer platinum solution to ensure that the temperature reaches 60 ℃.
d) Mixing the micrometer copper solution and the nanometer platinum solution, carrying out ultrasonic oscillation and mechanical stirring to ensure that the micrometer copper solution and the nanometer platinum solution are fully contacted, setting the ultrasonic power of ultrasonic oscillation to be 120W, the ultrasonic frequency to be 60KHz, and the mechanical stirring rotating speed to be 800rpm. Simultaneously, the temperature of the solution is reduced to 50 ℃, so that two particles are self-assembled, and the reaction time is controlled to be 45min.
e) The particles in the bimetallic solution were centrifuged at 12000rmp for 3min. And (5) after centrifugation, cleaning and drying to obtain the bimetal material.
f) According to the weight percentage, 80 percent of bimetal material and 20 percent of soldering flux (the soldering flux comprises 15 percent of rosin and 85 percent of glycerol) are added, and mechanical stirring, ultrasonic oscillation and mechanical mixing are carried out to prepare the micro-nano bimetal paste.
g) And (3) coating the paste on a copper substrate to prepare a sintering sample, performing hot-pressing sintering, setting the sintering temperature to 260 ℃ and the sintering pressure to 2MPa, and preparing the highly stable bimetal core-shell sintered body.
The bimetal obtained in example 2 was tested and had a particle size of 2.1um. The bimetallic core-shell sintered body obtained in example 2 was tested to have a specific resistance of 8.25×10 -8 Ωm。
Example 3
a) Commercial nano palladium particles and micron copper particles are dispersed in ethylene glycol to obtain nano palladium solution and micron copper solution. The concentration of the micron copper particles in the solution is regulated to be 100mg/mL, and the concentration of the nanometer palladium particles is regulated to be 200mg/mL. The particle diameter of the nano palladium particles is 20nm, and the particle diameter of the micro copper particles is 1.5 mu m.
b) And adding quaternized polyacrylamide into the micron particle solution, and adjusting the molar concentration to be 0.05mol/L to ensure that the surfaces of the micron copper particles are positively charged. Adding sodium fatty alcohol sulfate into the nano-particle solution, regulating the molar concentration to be 0.15mol/L, adding a proper amount of OH-ions into the solution, regulating the PH to be 7-8 to ensure that the solution has weak alkalinity, and leading the surfaces of the nano-palladium particles to be negatively charged.
c) And respectively carrying out water bath heating on the micrometer copper solution and the nanometer palladium solution to ensure that the temperature reaches 60 ℃.
d) Adding one-fourth volume of nano palladium solution into a first container, carrying out ultrasonic oscillation and mechanical stirring on the solution to uniformly suspend nano palladium particles in the solution, placing the container on a magnetic panel, standing, and distributing the nano palladium particles on the bottom surface of the container under the action of magnetic force; carrying out ultrasonic oscillation and mechanical stirring on all the micrometer copper solutions in other containers to uniformly suspend the micrometer copper in the solutions, then adding the solutions into a first container, standing, and distributing micrometer copper particles on nanometer palladium particles under the action of magnetic force; carrying out ultrasonic oscillation and mechanical stirring on the rest nano palladium solution in other containers to uniformly suspend nano palladium particles in the solution, then adding the solution into a first container, standing, and distributing the nano palladium particles on the micron copper particles under the action of magnetic force; the magnetic panel is removed, the ultrasonic and mechanical stirring are carried out to ensure that the ultrasonic power of ultrasonic oscillation is 150W, the ultrasonic frequency is 60KHz, and the mechanical stirring rotating speed is 900rpm. Simultaneously, the temperature of the solution is reduced to 50 ℃, so that two particles are self-assembled, and the reaction time is controlled to be 45min.
e) The particles in the bimetallic solution were centrifuged at 15000rmp for 3min. And (5) after centrifugation, cleaning and drying to obtain the bimetal material.
f) According to the weight percentage, 80 percent of bimetal material and 20 percent of soldering flux (the soldering flux comprises 15 percent of rosin and 85 percent of glycerol) are added, and mechanical stirring, ultrasonic oscillation and mechanical mixing are carried out to prepare the micro-nano bimetal paste.
g) And (3) coating the paste on a copper substrate to prepare a sintering sample, performing hot-pressing sintering, setting the sintering temperature to 300 ℃ and the sintering pressure to 5MPa, and preparing the highly stable bimetal core-shell sintered body.
The bimetal obtained in example 3 was tested and had a particle size of 1.6. Mu.m. The bimetallic core-shell sintered body obtained in example 3 was tested to have a specific resistance of 1.32×10 -7 Ωm。
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.

Claims (9)

1. The preparation method of the bimetallic material is characterized by comprising the following steps of:
a) Dispersing nano metal particles and micron metal particles in the solution respectively to obtain a nano metal solution and a micron metal solution;
b) Adding cationic surfactant into micrometer metal solution to make micrometer metal particles surface positively charged, adding anionic surfactant into nanometer metal solution, and adding proper quantity of OH into nanometer metal solution - The ion is regulated to pH 7-8 to make the nano metal solution have weak alkalinity and make the nano metal particle surfaceThe surface is negatively charged; alternatively, an anionic surfactant is added to the micrometer metal solution, and a suitable amount of OH is added to the micrometer metal solution - The pH value is regulated to 7-8 to enable the micrometer metal solution to have weak alkalinity, the surface of micrometer metal particles is negatively charged, and a cationic surfactant is added into the nanometer metal solution to enable the surface of the nanometer metal particles to be positively charged;
c) Respectively carrying out water bath heating on the micrometer metal solution and the nanometer metal solution to enable the temperature to reach 60-70 ℃;
d) Mixing the micrometer metal solution and the nanometer metal solution, stirring to make the micrometer metal solution and the nanometer metal solution fully contact, reducing the temperature of the solution to 40-50 ℃ at the same time, and controlling the reaction time to 30-45 min;
e) Centrifuging, cleaning and drying particles in the bimetallic solution;
in the micrometer metal solution, the concentration of micrometer metal particles is 50-100 mg/mL; in the nano metal solution, the concentration of nano metal particles is 150-350 mg/mL; the mass ratio of the micrometer metal particles to the nanometer particles is 1: (2-4);
the micrometer metal particles are selected from one of copper, platinum, palladium, gold, silver, tin, zinc and aluminum, and the particle size of the micrometer metal particles is 1-50 mu m; the nano metal particles are selected from one of iron, gold, silver, tin, platinum and palladium, and the particle size of the nano metal particles is 2 nm-500 nm.
2. The method for producing a bimetal material according to claim 1, wherein in the step b), the molar concentration of the cationic surfactant in the metal solution is 0.01 to 0.05mol/L; the molar concentration of the anionic surfactant in the metal solution is 0.01-0.05 mol/L; when the cationic surfactant is added into the micrometer metal solution and the anionic surfactant is added into the nanometer particle solution, the molar concentration ratio of the cationic surfactant to the anionic surfactant is 1 (2-3); when an anionic surfactant is added into the micrometer metal solution and a cationic surfactant is added into the nanometer particle solution, the molar concentration ratio of the anionic surfactant to the cationic surfactant is 1 (2-3).
3. The method of preparing a bimetallic material as set forth in claim 1, wherein in step d), the stirring process includes ultrasonic vibration and mechanical stirring; the ultrasonic power of ultrasonic oscillation is 80-200W, the ultrasonic frequency is 40 KHz-100 KHz, and the mechanical stirring rotating speed is 500-1000 rpm.
4. The method for preparing a bimetal material according to claim 1, wherein in the step d), the process of mixing the micrometer metal solution with the nanometer metal solution comprises the following steps:
adding one-fourth to one-half of the volume of nano metal solution into a first container, carrying out ultrasonic oscillation and mechanical stirring on the solution to enable nano metal to be uniformly suspended in the solution, placing the container on a magnetic panel, standing, and distributing nano metal particles on the bottom surface of the container under the action of magnetic force; carrying out ultrasonic oscillation and mechanical stirring on all the micrometer metal solutions in other containers to uniformly suspend the micrometer metal in the solutions, then adding the solutions into a first container, standing, and distributing micrometer particles on the nanometer metal particles under the action of magnetic force; carrying out ultrasonic oscillation and mechanical stirring on the rest nano metal solution in other containers to uniformly suspend nano metal in the solution, then adding the solution into a first container, standing, and distributing nano particles on the micrometer metal particles under the action of magnetic force; the magnetic panel is removed.
5. The method of producing a bimetal according to claim 1, wherein in step e), the rotational speed of the centrifugal operation is 12000 to 15000rpm and the centrifugal time is 2 to 4 minutes.
6. The method for producing a bimetal material according to claim 1, wherein the solution is absolute ethanol, ultrapure water, ethylene glycol, isopropanol or glycerol.
7. A bimetal material, characterized in that the bimetal material is prepared by the preparation method of the bimetal material according to any one of claims 1-6; the bimetal material comprises nano metal particles and micron metal particles, the bimetal material is of a core-shell structure, the micron metal particles are used as cores, the nano metal particles are used as shell layers, and the nano metal particles are coated on the micron metal particles.
8. A bimetal paste, which is characterized by comprising 10-20% of soldering flux and 80-90% of bimetal material as claimed in claim 7 according to mass percent.
9. An interconnection method, comprising the steps of: coating the bimetallic paste as set forth in claim 8 on a metal substrate, and introducing 5%H 2 Hot-pressed sintering is carried out with mixed gas of 95 percent Ar; in the hot pressing sintering process, the sintering temperature is 260-350 ℃ and the sintering pressure is 2-5 MPa.
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