CN113492277B - Low-temperature solder paste material with metal coating and carbon nano tube reinforcement and preparation method thereof - Google Patents
Low-temperature solder paste material with metal coating and carbon nano tube reinforcement and preparation method thereof Download PDFInfo
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- CN113492277B CN113492277B CN202010196593.9A CN202010196593A CN113492277B CN 113492277 B CN113492277 B CN 113492277B CN 202010196593 A CN202010196593 A CN 202010196593A CN 113492277 B CN113492277 B CN 113492277B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
- B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
- B23K35/0244—Powders, particles or spheres; Preforms made therefrom
- B23K35/025—Pastes, creams, slurries
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/26—Selection of soldering or welding materials proper with the principal constituent melting at less than 400 degrees C
- B23K35/262—Sn as the principal constituent
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/36—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
- B23K35/3612—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with organic compounds as principal constituents
Abstract
The invention belongs to the technical field of brazing, and relates to a low-temperature solder paste material and a preparation method thereof. The preparation method of the low-temperature solder paste material comprises the steps of adding the copper-plated or silver-plated carbon nano tube prepared by a polymer-assisted metal atom chemical electroless deposition method into SnBi-based low-temperature solder powder, adding the mixture into SnBi-based low-temperature solder alloy melt after ball milling and uniform mixing, obtaining SnBi-based low-temperature solder alloy powder after ultrasonic mixing, standing and powder blowing smelting, and then uniformly mixing the SnBi-based low-temperature solder alloy powder with soldering flux. The method relies on the uniformity of copper layers and silver layers and the good wettability of tin-copper or tin-silver interfaces, so that copper-plated or silver-plated carbon nanotubes obtain good dispersibility in a tin-bismuth alloy matrix, the bonding strength of the tin-bismuth-copper (silver) interfaces is enhanced, the brittleness and toughness of the traditional tin-bismuth alloy are improved in advance while the low-temperature melting point characteristic is kept unchanged, and when the tin-bismuth-copper (silver) interface is used for welding, a formed welding spot has a microstructure with a uniform tissue and a lower void ratio, so that the fatigue resistance and the breakage resistance of the welding spot can be improved.
Description
Technical Field
The invention belongs to the technical field of brazing, and particularly relates to a low-temperature tin paste material with a metal coating and carbon nanotube reinforcement function and a preparation method thereof.
Background
With the enhancement of the awareness of the environmental protection of human beings and the continuous innovation of the electronic information industry, the use of the traditional lead-containing brazing materials Sn63Pb37, Sn60Pb40 and the like is more and more limited by the policies of WEEE, ROHS and the like of the European Union. Related management policies are promulgated in 2006 to limit the use of heavy metals such as lead, mercury, cadmium, hexavalent chromium and the like. In 2017, the global chip giant intel company announces that more low-temperature tin solder is adopted in the future production of computer main boards, so that a huge development space is brought for the use of lead-free low-temperature tin paste. On one hand, the low-temperature solder reduces the energy consumption in the production process, on the other hand, the low-temperature soldering helps to reduce the damage of the PCBA in the reflow soldering process, and simultaneously inhibits the warping deformation of the PCB.
The low-melting point lead-free solder commonly used at present mainly takes Sn-Bi58 alloy as a substrate. However, the SnBi-based alloy solder is prone to dendrite segregation and coarsening of the structure during the soldering solidification process, and the stress imbalance causes peeling and destruction of the solder joint. Therefore, it is necessary to strengthen and toughen the current SnBi-based alloy solder to meet the requirements of low-temperature welding production. The carbon nanotube has a structure in which carbon atoms are hybridized by sp2, has a large length-diameter ratio of more than 1000, a diameter of nano-scale (several nanometers to tens of nanometers), a length of micro-scale (several micrometers to tens of micrometers), high strength (a theoretical value of 200GPa) and good electric and heat conduction characteristics.
At present, the technology of modifying the SnBi-based alloy solder by adopting the carbon nano tube exists. For example, CN106363315A discloses a tin-plated carbon nanomaterial reinforced composite solder, which contains 84 to 95 parts by weight of tin-based solder, 0.01 to 0.2 parts by weight of carbon nanomaterial, and the balance of auxiliary agent. The preparation of the tin-plated carbon nano-material reinforced composite solder can be completed only by matching ultrasonic-assisted tin plating with carbon nano-material doping, specifically, firstly, mixing the carbon nano-material with liquid-phase tin-based solder, simultaneously assisting ultrasonic waves to promote wetting between the carbon nano-material and the tin-based solder so as to realize metallization of the surface of the carbon nano-material to obtain intermediate solder alloy, mixing the intermediate solder alloy with molten tin-based solder to obtain tin-plated carbon nano-material reinforced composite solder alloy, then preparing the tin-plated carbon nano-material reinforced composite solder alloy into intermediate solder alloy powder, and uniformly stirring and mixing the intermediate solder alloy powder with soldering flux to obtain the tin-plated carbon nano-material reinforced composite solder. The creep property and electromigration property of the tin-based solder can be improved by adopting the method, but the problems of plasticity and brittleness are not mentioned.
Disclosure of Invention
The invention aims to overcome the defect of low plasticity of the traditional low-temperature SnBi-based alloy solder, and provides a low-temperature solder paste material capable of improving plasticity and brittleness and a preparation method thereof.
As described above, CN106363315A discloses that a tin-plated carbon nanomaterial-reinforced composite solder is obtained by a method of ultrasonic-assisted tin plating and carbon nanomaterial doping, and has improved creepBut the surface compatibility between the carbon nano material and the solder is poor, the carbon nano material is difficult to realize good dispersion in the solder by ultrasonic-assisted infiltration, and the carbon nano tube in the finally obtained composite solder still possibly exists in the form of carbon nano material clusters, so that the brittleness and the toughness of the composite solder are not improved, and the voidage of a welding point formed when the composite solder is used for welding is high, and the plasticity of the welding point is not improved. The inventors of the present invention have found, after intensive research, that a nano copper layer or a nano silver layer having a uniform thickness can be formed on the surface of a carbon nanotube by modifying the surface of the carbon nanotube by chemical electroless deposition of copper or silver using a polymer-assisted method, and the uniform distribution of the copper layer or the silver layer in the radial direction of the metal-coated carbon nanotube thus obtained is isotropic, thereby not only effectively preventing the carbon nanotube from agglomerating and dispersing the carbon nanotube in a SnBi-based low temperature solder in a single form rather than a cluster form, but also forming Cu through a chemical reaction due to the good wettability of the tin-copper or tin-silver interface 6 Sn 5/ Ag 3 Sn promotes the obtained copper-plated or silver-plated carbon nano tube to obtain better dispersibility in a tin-bismuth alloy matrix, further enhances the bonding strength of a tin-bismuth-copper (silver) interface, improves the elongation of the tin-bismuth alloy, and can improve the brittleness and toughness of the traditional low-temperature tin-bismuth alloy. Based on this, the present invention has been completed.
The low-temperature tin paste material contains 75-95 wt% of SnBi-based low-temperature solder, 0.01-0.5 wt% of metal-coated carbon nano tubes and the balance of soldering flux, wherein the metal-coated carbon nano tubes are copper-plated or silver-plated carbon nano tubes prepared by a polymer-assisted metal atom chemical electroless deposition method.
Preferably, the SnBi-based low temperature solder is at least one selected from SnBi, SnBiAg, SnBiCu, SnBiIn, and SnBiZn.
According to a specific embodiment of the present invention, the metal-coated carbon nanotube is prepared according to the following method:
s1, uniformly dispersing the carbon nano tube in a solvent by an ultrasonic method or a high-speed shearing method, and freeze-drying the obtained dispersion liquid to obtain a pre-dispersed carbon nano tube;
s2, dissolving dopamine hydrochloride in tris-HCl buffer solution with the pH value of 8-9 to obtain dopamine hydrochloride buffer solution with the concentration of (0.1-0.3) g/100mL, then adding the pre-dispersed carbon nano tube, stirring and reacting at room temperature for 8-15 hours to enable dopamine hydrochloride to be polymerized on the surface of the carbon nano tube, and after the reaction is finished, sequentially filtering, washing and drying the self-polymerized product to obtain the dopamine hydrochloride surface-modified carbon nano tube;
s3, mixing ammonium tetrachloropalladate (Pd (NH) 4 ) 2 Cl 4 ) Dissolving in water to prepare an ammonium tetrachloropalladate solution with the concentration of (0.4-0.6) g/500mL, then adding the dopamine hydrochloride surface-modified carbon nano tube, stirring and reacting at room temperature for 0.5-5 h, and after the reaction is finished, sequentially filtering, washing and freeze-drying the obtained reaction product to obtain oxidative dopamine hydrochloride carbon nano tube powder;
s4, uniformly mixing a potassium sodium tartrate-alkaline substance mixed aqueous solution with a metal stock solution to obtain a mixed solution, wherein the concentration of potassium sodium tartrate in the mixed solution is (10-20) g/500mL, the concentration of an alkaline substance is (4-8) g/500mL, the concentration of the metal stock solution is (5-8) g/500mL, the metal stock solution is a soluble copper salt aqueous solution or a soluble silver salt aqueous solution, stirring and uniformly mixing the obtained mixed solution with a 1-2% formaldehyde aqueous solution according to the mass ratio of (0.5-2): 1, then adding the oxidative dopamine hydrochloride carbon nanotube powder, stirring and reacting for 30-60 minutes at room temperature, and after the reaction is finished, sequentially filtering, washing and freeze-drying the obtained reaction product to obtain the metal-coated carbon nanotube.
Preferably, the thickness of the copper layer or the silver layer on the surface of the metal-coated carbon nanotube is 10-1000 nanometers.
Preferably, the carbon nanotubes are single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
Preferably, the inner diameter of the carbon nano tube is less than 5 nanometers, the outer diameter of the carbon nano tube is less than or equal to 30 nanometers, the length of the carbon nano tube is less than 50 micrometers, and the purity of the carbon nano tube is higher than 95 percent.
Preferably, the active agent contained in the soldering flux is a compound active agent formed by compounding an organic acid and an imidazole iodide salt, wherein the organic acid is selected from at least one of malonic acid, succinic acid, adipic acid and suberic acid, and the imidazole iodide salt is selected from at least one of 1-ethyl-3-methylimidazole iodide, 1-propyl-3-methylimidazole iodide and 1-butyl-3-methylimidazole iodide.
Preferably, the water-in-oil emulsifier contained in the soldering flux is triglycerol monostearate.
Preferably, the solvent contained in the soldering flux is an alcohol ether solvent; the alcohol ether solvent is a compound alcohol ether solvent formed by compounding an alcohol ether solvent with low viscosity and low boiling point and an alcohol ether solvent with high viscosity and high boiling point, the alcohol ether solvent with low viscosity and low boiling point is selected from at least one of ethylene glycol diethyl ether, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, and the alcohol ether solvent with high viscosity and high boiling point is selected from at least one of diethylene glycol butyl ether, triethylene glycol dimethyl ether and tripropylene glycol methyl ether.
In addition, the invention also provides a preparation method of the low-temperature tin paste material, which comprises the steps of adding the metal coating carbon nano tube into SnBi-based low-temperature solder powder, adding the mixture into SnBi-based low-temperature solder alloy molten liquid at the temperature of 200-400 ℃ after ball-milling and uniform mixing, obtaining the SnBi-based low-temperature solder alloy powder enhanced by the metal coating carbon nano tube after ultrasonic mixing, standing and powder blowing smelting, and then stirring and uniformly mixing the SnBi-based low-temperature solder alloy powder and soldering flux to obtain the low-temperature tin paste material.
Preferably, the mass ratio of the SnBi-based low-temperature solder powder to the SnBi-based low-temperature solder alloy melt is 1 (8-10).
Preferably, the SnBi-based low-temperature solder powder and the SnBi-based low-temperature solder alloy powder are respectively and independently No. 3-6 powder (5-50 micrometers). Specifically, the powder 3 is 25-45 microns, the powder 4 is 20-38 microns, the powder 5 is 15-25 microns, and the powder 6 is 5-15 microns.
The beneficial effects of the invention include:
(1) the low-temperature melting point characteristic of the tin-bismuth-based alloy is kept unchanged, the brittleness of the tin-bismuth-based alloy is obviously improved, and the toughness of the tin-bismuth-based alloy is improved;
(2) the welding spot formed after welding has lower void ratio, and the fatigue resistance and the destructive resistance of the welding spot can be effectively improved.
Drawings
FIG. 1 is a transmission electron micrograph of a multi-walled carbon nanotube material used in the examples;
FIG. 2 is a scanning electron micrograph of the copper-plated carbon nanotube powder obtained in example 1.
Detailed Description
In the process of preparing the metal-coated carbon nanotube provided by the present invention, the solvent used in step S1 may be at least one selected from water, ethanol, N-dimethylformamide, acetone, hexafluoroisopropanol, xylene, and the like, and preferably water and/or hexafluoroisopropanol. The tris-HCl buffer solution used in step S2 may be a ready-made solution or a prepared solution, and the specific preparation process may be to adjust the pH value of the aqueous solution of 3- (hydroxymethyl) aminomethane (concentration is 1-2 g/500mL) to 8-9 with 0.1mol/L HCl. The alkaline substance used in step S4 may be, for example, at least one selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and the like. The aqueous solution of a soluble copper salt may be, for example, at least one selected from an aqueous copper sulfate solution, an aqueous copper nitrate solution, and an aqueous copper chloride solution, and the aqueous solution of a soluble silver salt may be, for example, an aqueous silver nitrate solution. When the surface of the carbon nano tube needs to be plated with a copper layer, the metal stock solution adopts a soluble copper salt aqueous solution; when the silver plating layer is needed, the metal stock solution adopts soluble silver aqueous solution.
In the present invention, the water-in-oil emulsifier contained in the soldering flux is preferably triglycerol monostearate, and this specific water-in-oil emulsifier is easily soluble in organic solvents and has a high HLB value and a strong emulsifying power.
In the invention, the active agent contained in the soldering flux is preferably a compound active agent formed by compounding an organic acid and an imidazole iodide salt. Specific examples of the organic acid include, but are not limited to: at least one of malonic acid, succinic acid, adipic acid, sebacic acid and suberic acid. Specific examples of the imidazolium iodide salt include, but are not limited to: at least one of 1-ethyl-3-methylimidazole iodide salt, 1-propyl-3-methylimidazole iodide salt and 1-butyl-3-methylimidazole iodide salt. In addition, the mass ratio of the organic acid to the imidazole iodide salt is preferably (3-5): 1. The compound activator is adopted to replace the traditional activator containing chlorine and bromine, so that the compound activator has higher activity, the welding capability is improved, and the welding effect is improved, thereby being more beneficial to improving the brittleness and the toughness of the low-temperature tin-bismuth-based alloy, and being capable of meeting the halogen-free regulation requirement.
In the invention, the soldering flux preferably adopts a relatively volatile alcohol ether solvent (with low viscosity and boiling point lower than 160 ℃), and particularly preferably adopts a compound alcohol ether solvent formed by compounding the alcohol ether solvent with low viscosity and low boiling point and the alcohol ether solvent with high viscosity and high boiling point. Specific examples of the alcohol ether solvent having a low viscosity and a low boiling point include, but are not limited to: at least one of ethylene glycol diethyl ether (boiling point of 121 ℃, viscosity of 0.65 mPas), ethylene glycol dimethyl ether (boiling point of 85.2 ℃, viscosity of 1.1 mPas) and diethylene glycol dimethyl ether (boiling point of 160 ℃, viscosity of 0.98 mPas). Specific examples of the alcohol ether solvent having a high viscosity and a high boiling point include, but are not limited to: diethylene glycol butyl ether (boiling point 230 ℃, viscosity 6.5 mPas), triethylene glycol dimethyl ether (boiling point 216 ℃, viscosity 3.8 mPas) and tripropylene glycol methyl ether (boiling point 236 ℃, viscosity 5.6 mPas). The mass ratio of the low-viscosity and low-boiling-point alcohol ether solvent to the high-viscosity and high-boiling-point alcohol ether solvent is preferably (1-2): 1. The adoption of the preferable solvent can realize the adjustment of viscosity to adapt to the low-temperature welding working environment.
The flux is generally rosin as a main component, and the remaining components other than the above three components may be conventionally selected in the art. According to one embodiment of the invention, the soldering flux contains 40-50 wt% of 1- (3-aminopropyl) imidazole rosin salt, 15-30 wt% of water-in-oil emulsifier, 5-8 wt% of activator, 13-25 wt% of solvent, 0.2-2 wt% of fumed silica, 0.2-2 wt% of hydrogenated castor oil and 0.05-2 wt% of corrosion inhibitor. The 1- (3-aminopropyl) imidazole rosin salt can be obtained by neutralizing 1- (3-aminopropyl) imidazole and rosin in a solvent according to the molar ratio of 1:1 and then drying. The rosin may be at least one of hydrogenated rosin, maleic acid-modified rosin, and acrylic acid-modified rosin. The fumed silica can be at least one of Waters model N20, Degussa model AEROSIL 380, Degussa model A200, Deshan model REOLOSIL QS40, and Carbobet M-5. The corrosion inhibitor can be at least one selected from 1,2, 3-benzotriazole, benzimidazole and methyl benzotriazole. The flux may be used in the form of a paste, a liquid, etc. In addition, the flux can be obtained by commercial products or modulation.
The following detailed description of embodiments of the invention is intended to be illustrative of the invention and is not to be construed as limiting the invention. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are conventional products which are commercially available, and are not indicated by manufacturers.
In the following examples and comparative examples, the raw materials SnBi58 tin bismuth based low temperature solder powder, multi-walled carbon nanotubes, rosin type flux paste are all commercially available products. Wherein, the SnBi58 tin-bismuth based low-temperature solder powder is No. 5 powder; the multi-walled carbon nano-tube is provided by Chengdu Kogyao nano, the purity is more than 95 wt%, the characterization result of a transmission electron microscope is shown in figure 1, as can be seen from figure 1, the inner diameter is less than 5 nm, the outer diameter is less than or equal to 30 nm, and the length is 10-30 microns; the solvent contained in the rosin type soldering paste is a compound alcohol ether solvent formed by compounding an alcohol ether solvent (specifically ethylene glycol dimethyl ether) with low viscosity and low boiling point and an alcohol ether solvent (specifically tripropylene glycol methyl ether) with high viscosity and high boiling point according to the mass ratio of 1:1, the active agent is a compound active agent formed by compounding an organic acid (specifically a mixture of adipic acid and sebacic acid according to the molar ratio of 1: 1) and an iodoimidazolium salt (specifically 1-butyl-3-methylimidazolium iodide) according to the mass ratio of 4:1, and the water-in-oil type emulsifier is triglycerol monostearate.
Example 1
(1) Preparing a copper-plated carbon nanotube:
s1: uniformly dispersing the multi-walled carbon nano-tube in hexafluoroisopropanol by a high-speed shearing method, controlling the rotating speed of a high-speed shearing machine to be 5000rpm, controlling the shearing time to be 25 minutes, and sequentially filtering, washing and freeze-drying the dispersion liquid to obtain a pre-dispersed carbon nano-tube;
s2: adjusting the pH value of 3- (hydroxymethyl) aminomethane water solution (1.214g/500mL) to 8.5 by using 0.1mol/L HCl solution to obtain tris-HCl buffer solution; dissolving dopamine hydrochloride in Stris-HCl buffer solution (0.2g/100mL), adding the pre-dispersed carbon nano tubes obtained in S1, stirring and reacting at room temperature for 12 hours to enable dopamine to be self-polymerized on the surfaces of the carbon tubes, filtering the obtained self-polymerized products after the reaction is finished, washing filter residues with deionized water to remove residual solvent, dopamine and the like, and then drying in vacuum at 60 ℃ for 12 hours to obtain dopamine hydrochloride surface modified carbon nano tubes;
s3: preparation of Pd (NH) 4 ) 2 Cl 4 Adding a deionized water solution (0.568g/500mL) into the dopamine hydrochloride surface-modified carbon nano tube obtained in the step S2, uniformly stirring and dispersing, then reacting at room temperature for 1h, and after the reaction is finished, sequentially filtering, washing and freeze-drying the obtained reaction product to obtain oxidative dopamine hydrochloride carbon nano tube powder;
s4: adding a copper sulfate aqueous solution into a mixed aqueous solution of potassium sodium tartrate and NaOH, uniformly mixing to obtain a mixed solution, wherein the concentration of potassium sodium tartrate in the mixed solution is 14.5g/500mL, the concentration of NaOH is 6g/500mL, and the concentration of copper sulfate is 6.5g/500mL, then uniformly stirring and mixing the mixed solution and a 1.5% formaldehyde aqueous solution according to the mass ratio of 1:1, then adding oxidative dopamine hydrochloride carbon nanotube powder obtained in S3, fully stirring and reacting for 30 minutes at room temperature, filtering, washing, and freeze-drying after the reaction is finished to obtain copper-plated carbon nanotube powder, wherein the thickness of a copper layer is 100-300 nanometers, and carrying out vacuum packaging for later use. The scanning electron microscope characterization result of the copper-plated carbon nanotube powder is shown in fig. 2, and it can be seen from fig. 2 that the nano-copper particles are effectively deposited on the surface of the carbon nanotube after 30 minutes of chemical deposition.
(2) Preparing a low-temperature solder paste material:
adding the copper-plated carbon nanotube powder obtained in the step (1) into SnBi-based low-temperature solder powder, and fully mixing the powder by a ball mill mixer to preliminarily prepare composite alloy powder; after quantitative calculation, adding the composite gold powder into 400 ℃ SnBi-based low-temperature solder alloy melt (the mass ratio of the SnBi-based low-temperature solder powder to the SnBi-based low-temperature solder alloy melt is 1:9), and finally obtaining the copper-plated carbon nanotube reinforced SnBi-based low-temperature solder alloy powder with the powder model of No. 5 powder through processes of ultrasonic mixing, standing, powder blowing smelting and the like; and then, mixing the copper-plated carbon nanotube enhanced SnBi-based low-temperature solder alloy powder and the rosin type flux paste at a low speed (<120rpm) in a planetary stirrer or a propeller stirrer for 10 minutes to obtain a low-temperature SnBi58CNT0.05 solder paste material, and packaging for later use. The low-temperature SnBi58CNT0.05 solder paste material contains 95 wt% of SnBi58 tin bismuth-based low-temperature solder, 0.05 wt% of copper-plated carbon nano-tubes and the balance of rosin type soldering paste.
Example 2
(1) Preparing silver-plated carbon nanotubes:
the silver-plated carbon nanotube is prepared according to the method of the embodiment 1, except that in the step S4, the raw material copper sulfate aqueous solution is replaced by silver nitrate aqueous solution with the same concentration and dosage to obtain silver-plated carbon nanotube powder, wherein the thickness of the silver layer is 100-300 nanometers, and the silver layer is vacuum-packaged for later use.
(2) Preparing a low-temperature solder paste material:
adding the silver-plated carbon nanotube powder obtained in the step (1) into SnBi-based low-temperature solder powder, and fully mixing the silver-plated carbon nanotube powder and the SnBi-based low-temperature solder powder by a ball mill mixer to obtain composite alloy powder by preliminary preparation; after quantitative calculation, adding the composite gold powder into 400 ℃ SnBi-based low-temperature solder alloy molten liquid (the mass ratio of the SnBi-based low-temperature solder powder to the SnBi-based low-temperature solder alloy molten liquid is 1:9), and finally obtaining the enhanced SnBi-based low-temperature solder alloy powder of the silver-plated carbon nano tube by the processes of ultrasonic mixing, standing, powder blowing smelting and the like, wherein the powder type is No. 5 powder; and then mixing the silver-plated carbon nanotube enhanced SnBi-based low-temperature solder alloy powder and the rosin type flux paste in a planetary mixer or a propeller mixer at a low speed (<120rpm) for 10 minutes to obtain a low-temperature SnBi58CNT0.05 solder paste material, and packaging for later use. The low-temperature SnBi58CNT0.05 solder paste material contains 75 wt% of SnBi58 tin bismuth-based low-temperature solder, 0.5 wt% of silver-plated carbon nano-tubes and the balance of rosin type soldering paste.
Comparative example 1
A low temperature snbi58cnt0.05 solder paste material was prepared as in example 1, except that the carbon nanotubes were not modified by surface copper plating, and the other conditions were the same as in example 1, to obtain a reference low temperature snbi58cnt0.05 solder paste material. The reference low-temperature SnBi58CNT0.05 solder paste material contains 95 wt% of SnBi58 tin bismuth-based low-temperature solder, 0.05 wt% of unmodified carbon nano-tubes and the balance of rosin type soldering paste.
Comparative example 2
(1) Preparing the nickel-plated carbon nano tube:
the nickel-plated carbon nanotube is prepared according to the method of the embodiment 1, except that in the step S4, the raw material copper sulfate aqueous solution is replaced by the nickel nitrate aqueous solution with the same concentration and dosage to obtain the nickel-plated carbon nanotube powder, wherein the thickness of the nickel layer is 100-300 nanometers, and the nickel layer is vacuum-packaged for later use.
(2) Preparing a low-temperature solder paste material:
the low-temperature solder paste material is prepared according to the method of the embodiment 1, except that the copper-plated carbon nanotube powder is replaced by the nickel-plated carbon nanotube powder with the same weight part, so that the reference low-temperature SnBi58CNT0.05 solder paste material is obtained and packaged for later use. The reference low-temperature SnBi58CNT0.05 solder paste material contains 95 wt% of SnBi58 tin bismuth-based low-temperature solder, 0.05 wt% of nickel-plated carbon nano-tubes and the balance of rosin type solder paste.
Test example
(1) Measurement of melting point:
the melting points of the raw material SnBi 58-based low-temperature solder powder and the product low-temperature SnBi58CNT0.05 solder paste material are respectively measured according to a Differential Scanning Calorimetry (DSC), the heating rate is 10 ℃/min, and the obtained results are shown in Table 1 in a nitrogen environment.
(2) Determination of plasticity and brittleness:
the extension lengths of the raw material SnBi 58-based low-temperature solder powder and the product low-temperature SnBi58CNT0.05 solder paste material are respectively measured according to a GB/T228-2002 uniaxial tensile test method. Wherein the solder alloy area at the joint was a 2X 2mm cubic butt joint and the elongation rate was 5 μm/s, the results are shown in Table 1.
(3) Measuring the voidage of the welding spots:
the voidage of the solder joints formed by soldering the raw material SnBi 58-based low-temperature solder powder and the low-temperature SnBi58CNT0.05 solder paste material is respectively measured according to a slice microscopic observation method, and the obtained results are shown in Table 1.
TABLE 1
The results in table 1 show that the low-temperature solder paste material obtained by the method provided by the invention can improve the plasticity and toughness of the traditional tin-bismuth alloy in advance of keeping the low-temperature melting point characteristic unchanged, and when the low-temperature solder paste material obtained by the method is used for welding, the formed welding spot has a microstructure with uniform tissue and a lower void ratio, so that the fatigue resistance and the fracture resistance of the welding spot can be improved.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.
Claims (9)
1. The low-temperature tin paste material is characterized by comprising 75-95 wt% of SnBi-based low-temperature solder, 0.01-0.5 wt% of metal-coated carbon nanotubes and the balance of soldering flux, wherein the metal-coated carbon nanotubes are copper-coated or silver-coated carbon nanotubes prepared by a polymer-assisted metal atom chemical electroless deposition method, and the obtained metal-coated carbon nanotubes are isotropic due to uniform distribution of a copper layer or a silver layer in the radial direction;
the metal-coated carbon nanotube is prepared by the following method:
s1, uniformly dispersing the carbon nano tube in a solvent by an ultrasonic method or a high-speed shearing method, and freeze-drying the obtained dispersion liquid to obtain a pre-dispersed carbon nano tube;
s2, dissolving dopamine hydrochloride in tris-HCl buffer solution with the pH value of 8-9 to obtain dopamine hydrochloride buffer solution with the concentration of (0.1-0.3) g/100mL, then adding the pre-dispersed carbon nano tube, stirring and reacting at room temperature for 8-15 hours to enable dopamine hydrochloride to be polymerized on the surface of the carbon nano tube, and after the reaction is finished, sequentially filtering, washing and drying the self-polymerized product to obtain the dopamine hydrochloride surface-modified carbon nano tube;
s3, dissolving ammonium tetrachloropalladate in water to prepare an ammonium tetrachloropalladate solution with the concentration of (0.4-0.6) g/500mL, then adding the dopamine hydrochloride surface-modified carbon nano tube, stirring and reacting at room temperature for 0.5-5 h, and after the reaction is finished, sequentially filtering, washing and freeze-drying the obtained reaction product to obtain oxidative dopamine hydrochloride carbon nano tube powder;
s4, uniformly mixing a potassium sodium tartrate-alkaline substance mixed aqueous solution with a metal stock solution to obtain a mixed solution, wherein the concentration of potassium sodium tartrate in the mixed solution is (10-20) g/500mL, the concentration of an alkaline substance in the mixed solution is (4-8) g/500mL, the concentration of the metal stock solution is (5-8) g/500mL, the metal stock solution is a soluble copper salt aqueous solution or a soluble silver salt aqueous solution, and then mixing the mixed solution with a formaldehyde aqueous solution with the concentration of 1-2% according to the mass ratio of (0.5-2): 1, stirring and mixing uniformly, then adding the oxidative dopamine hydrochloride carbon nanotube powder, stirring and reacting for 30-60 minutes at room temperature, and after the reaction is finished, sequentially filtering, washing and freeze-drying the obtained reaction product to obtain the metal coating carbon nanotube.
2. The low temperature solder paste material of claim 1, wherein the SnBi-based low temperature solder is selected from at least one of SnBi, SnBiAg, SnBiCu, SnBiIn, and SnBiZn.
3. The low-temperature solder paste material as claimed in claim 1 or 2, wherein the thickness of the copper layer or the silver layer on the surface of the metal-coated carbon nanotube is 10-1000 nm.
4. The low temperature solder paste material of claim 1 or 2, wherein the carbon nanotubes are single-walled carbon nanotubes and/or multi-walled carbon nanotubes; the inner diameter of the carbon nano tube is less than 5 nanometers, the outer diameter of the carbon nano tube is less than or equal to 30 nanometers, the length of the carbon nano tube is less than 50 micrometers, and the purity of the carbon nano tube is higher than 95 percent.
5. The low-temperature solder paste material as claimed in claim 1 or 2, wherein the active agent contained in the soldering flux is a compound active agent formed by compounding organic acid and imidazole iodate; the organic acid is selected from at least one of malonic acid, succinic acid, adipic acid and suberic acid; the imidazole iodate is at least one selected from 1-ethyl-3-methylimidazole iodate, 1-propyl-3-methylimidazole iodate and 1-butyl-3-methylimidazole iodate.
6. A low temperature solder paste material according to claim 1 or 2, wherein the water-in-oil emulsifier contained in the flux is triglycerol monostearate.
7. The low temperature solder paste material according to claim 1 or 2, wherein the solvent contained in the flux is an alcohol ether solvent; the alcohol ether solvent is a compound alcohol ether solvent formed by compounding an alcohol ether solvent with low viscosity and low boiling point and an alcohol ether solvent with high viscosity and high boiling point, the alcohol ether solvent with low viscosity and low boiling point is selected from at least one of ethylene glycol diethyl ether, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, and the alcohol ether solvent with high viscosity and high boiling point is selected from at least one of diethylene glycol butyl ether, triethylene glycol dimethyl ether and tripropylene glycol methyl ether.
8. The method for preparing the low-temperature solder paste material according to any one of claims 1 to 7, wherein the method comprises the steps of adding the metal-coated carbon nanotube into SnBi-based low-temperature solder powder, performing ball milling and uniform mixing, adding the mixture into a SnBi-based low-temperature solder alloy molten liquid with the temperature of 200-400 ℃, performing ultrasonic mixing, standing and powder blowing smelting to obtain the SnBi-based low-temperature solder alloy powder enhanced by the metal-coated carbon nanotube, and then uniformly stirring and mixing the SnBi-based low-temperature solder alloy powder and a soldering flux to obtain the low-temperature solder paste material.
9. The method for preparing a low-temperature solder paste material according to claim 8, wherein the mass ratio of the SnBi-based low-temperature solder powder to the SnBi-based low-temperature solder alloy melt is 1: (8-10); the granularity of the SnBi-based low-temperature solder powder and the granularity of the SnBi-based low-temperature solder alloy powder are respectively 5-50 microns.
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| CN101418210B (en) * | 2007-10-26 | 2011-05-11 | 中国科学院理化技术研究所 | Method for preparing metal liquid mixed with granule having high heat-transfer performance |
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| CN101716707A (en) * | 2009-11-26 | 2010-06-02 | 深圳市亿铖达工业有限公司 | Nano reinforced lead-free composite soldering material |
| CN101817127A (en) * | 2010-05-10 | 2010-09-01 | 哈尔滨工业大学 | Sn-58Bi lead-free solder reinforced by carbon nano tube and preparation method thereof |
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