CN111702368A - Preparation method and packaging method of metal aerogel-based preformed soldering lug - Google Patents
Preparation method and packaging method of metal aerogel-based preformed soldering lug Download PDFInfo
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- CN111702368A CN111702368A CN202010583579.4A CN202010583579A CN111702368A CN 111702368 A CN111702368 A CN 111702368A CN 202010583579 A CN202010583579 A CN 202010583579A CN 111702368 A CN111702368 A CN 111702368A
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/0091—Preparation of aerogels, e.g. xerogels
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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
- B23K35/40—Making wire or rods for soldering or welding
Abstract
The invention provides a preparation method and a packaging method of a metal aerogel-based preformed soldering lug, wherein the preparation method of the metal aerogel-based preformed soldering lug comprises the following steps: preparing a metal aerogel matrix, cleaning the metal aerogel matrix and cutting the surface of the metal aerogel matrix; and compressing the obtained metal aerogel matrix, and cutting to obtain the preformed soldering lug. When the metal aerogel-based preformed soldering lug is used for packaging, the metal aerogel-based preformed soldering lug is processed according to a welding structure, so that the size and the shape of the metal aerogel-based preformed soldering lug are adapted; and then placing the processed metal aerogel based preformed soldering lug at a position to be welded, aligning, pressurizing, and applying a welding load to complete packaging. The nano metal aerogel-based material obtained by the technical scheme of the invention has good variability performance, structural adaptability and material compatibility; the welding flux does not contain extra welding flux, protective agent and the like, has low required welding temperature, high integrity of welding spots and good strength and high temperature performance after welding, and can solve the problems of large-size low-temperature packaging and high-temperature service of heterogeneous materials.
Description
Technical Field
The invention relates to the technical field of electronic packaging materials, in particular to a preparation method and a packaging method of a metal aerogel-based preformed soldering lug.
Background
With continuous innovation of the electronic industry and development of third-generation wide bandgap semiconductor silicon carbide (SiC) and gallium nitride (GaN), integration level and power density of electronic systems are increasingly improved, and power electronic devices with high-temperature (> 250 ℃) service requirements are more and more widely applied. However, conventional packaging materials and techniques have difficulty meeting the packaging and service requirements of such devices. The common Sn-based solder has a low melting point, and directly loses structural strength and stability under the condition of high temperature; high lead solder has severe environmental toxicity; the An-Sn series high-temperature solder alloy has extremely high cost, and the solders such as Zn base, Cu base, Al base and the like are easy to oxidize and have poor weldability; the method of Au-Au interconnection, Si-Si interconnection and the like has extremely high requirement on surface evenness; meanwhile, the high welding process temperature required by the materials can cause thermal damage and even failure of substrates, circuits and heat sensitive devices in an electronic system, so that a novel packaging material with low-temperature packaging requirements and high-temperature service performance is urgently needed.
Due to the nano-size effect, when the size of the material reaches the nano-scale (1-100 nm), the surface activity thereof will be greatly increased and cause a significant decrease in the melting point. For example, the melting point of silver is 961 ℃, but the nano silver can be sintered at 250-300 ℃ to form a block material with the performance close to that of silver simple substance. Therefore, the nanometer material as the packaging material can realize the interconnection requirement of high-temperature service under the lower temperature condition. However, the integration and packaging structure of electronic components is more and more complex, and special structures such as cavities, curved surfaces, step integration and the like are continuously generated in electronic systems. The existing nano-silver soldering paste is difficult to meet the packaging requirements of the structure, is difficult to coat, and is easy to cause the reliability problems of holes, insufficient strength and the like, even insufficient soldering and failure due to the volatilization of components such as soldering flux, surfactant and the like. Therefore, there is a need to develop a packaging material with adaptive soldering capability of complex structure.
Disclosure of Invention
Aiming at the technical problems, the invention discloses a preparation method and a packaging method of a metal aerogel-based preformed soldering lug.
In contrast, the technical scheme adopted by the invention is as follows:
the preparation method of the metal aerogel based preformed soldering lug is characterized by comprising the following steps:
step S1, preparing a metal aerogel matrix, cleaning and cutting the surface of the metal aerogel matrix, and removing residual reagents and uneven areas;
and step S2, compressing the obtained metal aerogel matrix, and cutting to obtain the preformed soldering lug.
The aerogel is a gel material taking gas as a dispersion medium, and the size of the internal solid phase and the size of the pore structure of the aerogel are both in the nanometer order, so that the aerogel also has the size effect of a nanometer material and the advantages of low-temperature sintering and high-temperature service materials. The aerogel material is internally provided with a continuous three-dimensional network formed by interweaving nanowires, the macrostructure has excellent elastic flexibility and deformation capability, and can be placed on various complex structure interfaces such as concave surfaces, curved surfaces, rings, steps and the like to be self-adaptively matched and fill a welding area, so that the aerogel material is a packaging material with remarkable application and performance advantages, and the packaging problem of the background technology of the invention is expected to be solved.
As a further improvement of the present invention, the material of the metallic aerogel matrix includes at least one of metallic materials such as silver, copper, nickel, gold, tin, etc. That is, one kind of them or a combination of two or more kinds thereof may be used.
As a further improvement of the invention, the metal aerogel matrix is internally provided with a three-dimensional network consisting of metal nanowires. Furthermore, the diameter of the metal nanowire is 20-1000nm, the size of the space among the metal nanowires is 50 nm-10 mu m, and the density is 1-600 mg/cm3. By adopting the technical scheme, the size effect of the nano material can be utilized, the deformability and weldability of the material can be effectively improved, and the required manufacturing cost can be reduced.
As a further improvement of the invention, the thickness of the metallic aerogel matrix is 5-100 mm.
As a further improvement of the present invention, in step S1, the metallic aerogel matrix is cross-linked between nanophase by flocculation-freeze solidification or "one-step" liquid phase reduction based on three-dimensional growth activator, and residual solvent is removed by supercritical drying or freeze drying.
The one-step liquid phase reduction method based on the three-dimensional growth activator has the advantages of simple reaction flow, low requirements on environment and equipment, capability of ensuring that the three-dimensional growth process of the nanowire is performed quickly and fully to form a gel structure, capability of effectively removing incompletely-reacted precursors, surfactants, organic solvents and the like, and capability of avoiding collapse or damage of the gas gel structure due to the action of the surface tension of the liquid in the drying process. The flocculation-freezing solidification mode takes the nano wire as a raw material, the manufacturing and cleaning processes are complex, but large-scale drying can be carried out, and the preparation efficiency is high.
As a further improvement of the present invention, in step S1, the "one-step" liquid phase reduction based on three-dimensional growth activator to obtain the metal aerogel matrix is prepared by the following steps: prefabricating a three-dimensional growth active agent, namely adding an active matrix material into a solvent for mixing to obtain the three-dimensional growth active agent; mixing the metal precursor, the surfactant and the three-dimensional growth activator, and uniformly stirring; heating the mixture in a closed reaction mould to react to obtain a metal aerogel matrix tissue which has the same surface structure as the mould and contains a solvent inside; and taking out the semi-finished product of the aerogel, cleaning to remove residual solvent, free nanowire monomer and active agent, and drying to finally obtain the metal aerogel matrix tissue with the three-dimensional structure. The obtained metal aerogel matrix tissue is a jelly-shaped block, and the internal tissue of the metal aerogel matrix is a nanowire continuous network structure which is mutually crosslinked into a foam shape. The preparation process of the aerogel is simple, controllable and stable, and is suitable for large-scale industrial production. As a further improvement of the invention, the active material matrix is one or a mixture of more of lignin, cellulose, amino acids, paraffin materials and decomposition products of the materials.
As a further improvement of the invention, the mass ratio of the solvent in the three-dimensional growth activator is not less than 70%; the solvent is acetone, ethanol or polyalcohol. The mixing mode is heating, stirring, ball milling and other modes.
As a further improvement of the invention, the active material matrix is washed and activated and then added into the solvent for mixing and dissolving, so as to obtain the three-dimensional growth activator. The dissolution is dissolution or dispersion by means of heating, stirring, ball milling, or the like.
As a further improvement of the invention, the metal precursor and the surfactant are corresponding reaction reagents required for preparing nanowires of Ag, Cu, Ni or Au and the like. Further, the metal precursor is corresponding salt or organic compound required for preparing metal nanowires such as Ag, Cu, Ni or Au, and the surfactant is corresponding PVP, hydrazine hydrate, glucose and other common surfactants.
Further, the mode of mixing the metal precursor, the surfactant and the three-dimensional growth activator is electromagnetic or mechanical stirring, and the stirring speed is 100-400 rpm, so that the stability of nucleation is ensured, and the excessive growth of crystal nuclei is inhibited.
As a further improvement of the invention, the closed reaction mold is a mold with an internal cavity made of polytetrafluoroethylene, stainless steel or other materials which do not react with the solvent physically and chemically.
As a further improvement of the invention, the depth of the inner cavity of the closed reaction mould is not equalGreater than 50 mm. This is because the growth of aerogels and nanowires is often influenced by the oxidation process, and even with deeper cavities, larger size aerogels cannot be obtained, only when other oxidants such as H are added2O2、O3、Fe3+When the reactivity is improved, a deeper cavity can be used.
As a further improvement of the invention, the cleaning is carried out by soaking and continuous solvent replacement. Furthermore, in the replacement process, the solvent completely submerges the metal aerogel tissue, deionized water-acetone/ethanol-deionized water or a single solvent is sequentially used in the replacement process, the replacement speed of the solvent is 1-50 ml/min, and the replacement time is 0.5-24 h. The solvent replacement speed is too fast, the damage of the gel structure is easy to cause, the cleaning of the interior of the gel cannot be realized if the replacement speed is too slow, and 0.5 h is the shortest replacement time required for ensuring the cleaning effect under the condition of high replacement speed.
As a further improvement of the invention, supercritical drying or ultralow temperature N is adopted2Drying is carried out in a freezing and vacuum freeze drying mode. The pure metal aerogel obtained by adopting the technical scheme of the invention has a three-dimensional structure and is a foam-shaped flexible block material completely formed by crosslinking nano wires. The drying method can avoid collapse or damage of the aerogel network structure caused by the surface tension of the liquid.
As a further improvement of the present invention, step S1 further comprises surface modification of the metallic aerogel matrix. Further, the surface treatment is surface activation, functional group grafting or interface transition material deposition. Furthermore, the deposition of the interface transition material is completed by filling liquid polymer material monomers and nanoparticles and adopting chemical plating, electrochemical plating, surface spraying or vapor deposition of a Ni, Au, Sn or Ti metal layer.
By adopting the technical scheme, the wettability and the interface reaction capability of the preformed soldering lug on various materials can be improved under the conditions of not damaging the metal aerogel matrix and not influencing the adaptive deformation capability of the soldering lug, so that the welding quality and the interface metallurgical reaction effect are improved.
As a further improvement of the present invention, in the compression process of step S2, the metal aerogel is heated or a protective, reducing atmosphere is applied. By adopting the technical scheme, the space density and the structural stability of the metal aerogel can be improved, and the processability, the usability and the storage and transportation performance are improved on the basis of not influencing the welding performance of the metal aerogel.
As a further improvement of the invention, the thickness of the preformed soldering lug is 2-1000 μm.
The invention also discloses a metal aerogel-based preformed soldering lug which is obtained by adopting the preparation method of any one of the metal aerogel-based preformed soldering lugs.
The invention also discloses a packaging method of the metal aerogel based preformed soldering lug, which comprises the following steps:
s11, processing the metal aerogel based preformed soldering lug according to the welding structure to adapt the size and the shape;
and S12, placing the metal aerogel based preformed soldering lug processed in the step S11 at a position to be soldered, aligning, pressurizing and applying a soldering load to complete the packaging. The metal aerogel is used for deforming, adapting and filling the area to be welded under the action of pressure.
By adopting the technical scheme, the metal aerogel with flexibility and elasticity can deform according to the structure of the area to be welded, so that a welding interface is matched and filled, and uniform and reliable interconnection of a complex structure is completed; by combining all welding loads, the welding efficiency and the heat affected zone can be optimized, and the problem of low-temperature and high-efficiency welding of various structures and materials is solved.
The metal aerogel with flexibility can be placed on the surfaces of parts to be welded with various complex structures such as planes, concave surfaces, curved surfaces and the like, and sintering welding is carried out by adjusting appropriate process parameters in a manner of not limited to thermocompression welding. The metal aerogel-based material with the three-dimensional network structure has a compact structure after being sintered, so that the shear strength after welding is higher, and meanwhile, the low conductivity of the metal silver meets the requirement of most electronic devices on interconnection materials. Compared with the nano-silver preformed sheet and the nano-silver paste, the nano-metal aerogel-based material has the advantages that the welding occasion is more flexible and easier to use, and the welded product has better performance and higher reliability; compared with the traditional solder, due to the characteristics of the nano material, the nano metal aerogel based preformed soldering lug has the advantages of low-temperature sintering and high-temperature service, and can be suitable for packaging high-power electronic devices sensitive to temperature.
As a further improvement of the present invention, in step S12, the region to be welded is a two-dimensional or three-dimensional structure including a concave-convex surface, a curved surface, a sawtooth surface, a circular surface, and a stepped structure.
As a further improvement of the invention, in step S12, the pressure of the alignment and pressurization is 0.01-20 MPa, the welding load is strong pressure, temperature, laser, microwave, ultrasound or current, and the welding time is 3S-20 min. By adopting the technical scheme, different welding processes can be selected to meet different welding requirements, particularly, cold welding can be realized under the condition of no integral heating through strong pressure, microwave and ultrasound, and the feasibility and compatibility of the welding process are further improved.
Compared with the prior art, the invention has the beneficial effects that:
firstly, the nano metal aerogel-based material obtained by the technical scheme of the invention has good variability performance, structural adaptability and material compatibility. The material can be conveniently placed on the surfaces of complex parts to be welded, such as concave-convex surfaces, curved surfaces, sawtooth surfaces and the like, and can be matched with various complex welding structures through structural deformation of the material to form a three-dimensional joint; furthermore, by means of proper surface modification, the wettability and the interface reaction characteristics of the heterogeneous material can be improved, so that a compact and reliable interconnection structure is formed among various heterogeneous materials.
Secondly, the metal aerogel base material obtained by the technical scheme of the invention has low welding temperature, high strength after welding and good high-temperature performance, and the size and pore structure of the internal three-dimensional network monomer are in nanometer level, so the sintering temperature of the metal aerogel base material is obviously lower than that of a common block material, and the temperature required by welding can be further reduced by means of special nanometer welding processes such as strong pressure, ultrasound, microwave, induction heating and the like, thereby solving the problems of low-temperature packaging and high-temperature service of heterogeneous materials.
Thirdly, the metal aerogel-based material prepared by the technical scheme of the invention has simple preparation process, strong machinability and lower cost, and the aerogel material with specific size, shape and space density can be prepared by adjusting the structure and cutting path of the die; compared with the traditional welding material, the material does not contain additional soldering flux, protective agent and the like, and avoids the pollution of a packaging structure and the problem of holes caused by the volatilization of soldering flux gas, so that the welding quality is more stable, the reliability is higher, and the packaging problem of a large-area device can be particularly solved; the welding efficiency can be improved by combining various welding technologies such as laser local heating, induction heating, ultrasonic friction welding and the like, so that the production requirements of large-scale welding of various heterogeneous materials are met.
Drawings
FIG. 1 is a schematic structural view of a metallic aerogel obtained in example 1 of the present invention; wherein, (a) is a macroscopic view of the metal aerogel, (b) is a microscopic structure view of the metal aerogel, and (c) is a microscopic structure view of the metal nanowires in the metal aerogel.
Fig. 2 is a schematic view of the soldering of a silver nanowire aerogel-based preformed solder piece in a convex structure according to example 1 of the present invention.
Fig. 3 is a schematic view of welding of the nano copper wire aerogel-based preformed solder sheet containing nano silver in the step structure according to embodiment 2 of the present invention.
Detailed Description
Preferred embodiments of the present invention are described in further detail below.
Example 1
A silver nanowire aerogel-based preformed soldering lug and a packaging method thereof are disclosed, wherein the specific method comprises the following steps:
(1) preparation of three-dimensional growth activator by hydrolysis of monomers using lignin and amino acids, and incorporation of metal precursor (AgNO)3) Surfactant (PVP), oxidant (FeCl)3) And stirring uniformly; heating the mixture in a closed reaction mould, and reacting to obtain the silver nanowire aerogel containing the solvent insideCleaning the obtained silver nanowire gel tissue by using a sodium chloride solution (1M), removing residual reaction reagents and free nanowire monomers in the silver nanowire gel tissue, drying the silver nanowire gel tissue again, and performing surface cutting by using a low-pressure electron beam to remove an uneven area to obtain silver nanowire aerogel with the thickness of about 5 mm; the structural schematic diagram of the obtained silver nanowire aerogel is shown in fig. 1.
(2) Carrying out hot pressing on the obtained clean silver nanowire aerogel matrix, carrying out presintering, and then cutting the clean silver nanowire aerogel matrix into aerogel preformed sheets with the same size as a welding area, wherein the thickness of the aerogel preformed sheets is 20 micrometers, the hot pressing temperature is 200 ℃, and the hot pressing time is 10 min;
(3) as shown in fig. 2, placing the obtained silver nanowire aerogel-based preformed soldering lug 1 between a first convex surface 2 to be soldered and a second concave surface 3 to be soldered, aligning and applying 2MPa pressure, and soldering at 250 ℃ for 10 min;
the preparation process and the welding process of the silver nanowire aerogel in the embodiment are simple and controllable, the preparation process and the welding process are completely compatible with the existing packaging equipment and process, the aerogel can fully fill the arc-shaped connecting area in the welding process, the welding temperature is low (200-250 ℃), the obtained joint has good shear strength (> 20 MPa), and the joint still has certain structural strength (> 10 MPa) under the high-temperature condition of more than 400 ℃, and has low-temperature packaging and high-temperature service performance.
Example 2
The application of the packaging method of the nano-silver doped nano-copper wire aerogel-based preformed soldering lug comprises the following specific steps:
(1) preparing nano silver particles by using silver nitrate as a precursor, PVP as a surfactant, ferric chloride as an oxidant and ethylene glycol as a solvent through a liquid phase reduction method, wherein the average particle size of the nano silver particles is 30-50 nm; repeatedly cleaning the obtained nano silver particles by using deionized water and alcohol, and drying at 50 ℃ to obtain clean nano silver particles;
(2) preparing a copper nanowire by using copper sulfate pentahydrate as a precursor, sodium hypophosphite monohydrate as a reducing agent, diethylene glycol as a solvent and PVP as surface activity as a reducing agent through a liquid phase reduction method, repeatedly cleaning and centrifuging the obtained copper nanowire by using ethanol and a deionized water solution, and removing residual reaction reagents; removing residual active agents on the surfaces of the nanowires by adopting aqueous formic acid (2.5 vol.%) and sodium bromide (1.5M); and finally, repeatedly washing and centrifuging for 2-3 times by using deionized water to obtain a clean copper nanowire monomer.
(3) Re-dispersing the obtained clean nanowire monomer (1 g) in a small amount of deionized water (50 ml) to obtain a high-concentration nanowire suspension; placing the suspension on a copper column precooled by liquid nitrogen, inducing directional solidification crystallization of water, and promoting the distribution of copper nanowires along a specific direction and position; then freezing and drying to obtain a copper nanowire network structure; and then pre-sintering for 1 hour at 250 ℃ under the condition of nitrogen to form a continuous copper nanowire aerogel tissue.
(4) Dispersing the nano silver in gaps among the copper nanowire networks by using deionized water as a solvent and using a solvent replacement method; removing residual solvent in the copper nanowire gel by using a low-temperature freeze drying technology, and removing a non-uniform area on the surface by using a low-power laser to obtain the copper nanowire aerogel doped with nano silver with the thickness of about 70 mm;
(5) carrying out hot pressing on the copper nanowire aerogel base, and then cutting the copper nanowire aerogel base into a step-shaped preformed sheet, wherein the average thickness of the preformed sheet is 100 micrometers, the hot pressing temperature is 300 ℃, and the hot pressing time is 10 min;
(6) using Ar2Performing surface activation on aerogel by using plasma, placing the obtained high-activity aerogel preforming sheet 4 (in a step shape) between the step surface of the first part to be welded 5 and the step surface of the second part to be welded 6, and completing welding by using an ultrasonic hot-press welding machine at the welding temperature of 150 ℃, the welding process time of 10 s and the welding pressure of 0.5 MPa as shown in figure 3;
when the nano copper wire aerogel doped with nano silver is used as a welding material in the embodiment, besides the advantages of the embodiment 1, the nano silver is doped in the copper nanowires, so that the compactness and the connectivity of the material can be enhanced, and the cost can be effectively reduced; and the ultrasonic hot pressing method is used for welding, so that the welding temperature can be further reduced, the production efficiency is improved, and the method is particularly suitable for integration of temperature sensitive components.
Example 3
A silver nanowire aerogel preformed soldering lug with a Sn plating layer deposited on the surface and a packaging method thereof are disclosed, wherein the specific method comprises the following steps:
(1) the method comprises the steps of preparing silver nanowire aerogel by adopting a liquid-phase induced reduction reaction and supercritical drying method, cleaning the obtained silver nanowire aerogel by using a sodium chloride solution (1M), depositing a Sn plating layer with the thickness of about 20 nm on the surface of the silver nanowire aerogel by using a chemical plating method, and cutting by using a low-power laser to obtain the silver nanowire aerogel with the thickness of about 50 mm and containing the Sn plating layer.
(2) And carrying out low-temperature hot pressing on the obtained silver nanowire aerogel substrate with the Sn plating layer, and then cutting the silver nanowire aerogel substrate into preformed sheets, wherein the average thickness of the preformed sheets is 50 micrometers, the hot pressing temperature is 100 ℃, and the hot pressing time is 10 min.
(3) And placing the silver nanowire aerogel containing the Sn plating layer between ceramic materials with the Ti-Au plating layer, applying 0.5 MPa pressure, and welding by adopting an electromagnetic induction method, wherein the welding process temperature is about 300-450 ℃, and the welding process time is 10 s.
The Sn-containing silver-plated nanowire aerogel obtained in this embodiment has the advantages of embodiment 1, and can improve the wetting behavior of the substrate and the compactness of the structure after welding by using the characteristics of low Sn melting point, good fluidity, interface wetting, strong reactivity and the like, so that a dense joint can be formed in a short time, and Ag formed by the reaction can be formed3The Sn phase can suppress the occurrence of electro-thermal migration, and thus has more excellent structural integrity and long-term reliability than those of examples 1 and 2.
Example 4
A silver nanowire aerogel preformed soldering lug and a packaging method thereof are disclosed, and the specific method comprises the following steps:
(1) preparing silver nanowire aerogel with the average diameter of 70 nm by adopting a liquid-phase induced reduction reaction and supercritical drying method, cleaning the obtained silver nanowire aerogel by using a sodium chloride solution (1M), and cutting by using a low-power laser to obtain the silver nanowire aerogel with the thickness of about 10 mm;
(2) hot pressing the obtained silver nanowire aerogel base, cutting into preformed sheets with average thickness of 20 μm, hot pressing temperature of 350 deg.C, hot pressing time of 5 min, and passing Ar2+O2Performing surface activation by using plasma;
(3) placing the activated silver nanowire aerogel between a ceramic substrate with a Ti-Ag coating and an aluminum alloy heat sink, applying a strong pressure of 20-40 MPa, and completing connection at room temperature by means of ultrasound, wherein the welding process time is 10 s.
The silver nanowire aerogel obtained in the embodiment has the advantages of the embodiment 1, and can realize large-area cold-pressing welding under the condition of no heating condition by means of the characteristic of extremely high surface activity of the activated silver nanowires, and the welding time can be shortened by applying ultrasonic waves, so that the low-temperature welding performance and the welding efficiency are more excellent.
Comparative example 1
The Au-Sn eutectic solder is prepared by adopting a metal smelting mode, and is prepared into powder, and then the powder is mixed with soldering flux and an active agent to prepare the soldering paste. In the welding process, Au-Sn soldering paste is coated on a bonding pad, the alignment and the stacking of components are completed by means of a surface mount technology, then the soldering paste is melted by adopting a reflow process, an interface reaction is initiated, and finally, welding residues are cleaned to obtain a complete interconnection joint.
Under the process conditions of the comparative example, the melting point of the Au-Sn eutectic solder is 280 ℃, a substrate and a Si-based device in the device can be thermally damaged in the reflow process, and the Au-Sn eutectic solder can be remelted under the working environment with the temperature higher than the temperature, so that the welding spot fails; the solder contains various soldering fluxes, which easily causes the problems of PCB corrosion, short circuit, holes caused by gas volatilization and the like; meanwhile, the Au content in the Au-Sn eutectic solder can reach 80 percent, so the material cost is extremely high. In summary, the present invention has significant cost, performance and reliability advantages over this embodiment.
Comparative example 2
Preparing nano silver particles by using silver nitrate as a precursor through a polyol method; carrying out surface cleaning on the nano-silver by acid or an organic solvent, carrying out ultrasonic cleaning and centrifugation for multiple times, and adding the obtained clean nano-silver into the mixed organic solution for ultrasonic dispersion; mixing the surfactant and the organic carrier to obtain nano-silver soldering paste; and uniformly coating the prepared nano silver paste on the surface to be welded, preserving heat at 250-300 ℃ for 10-210 min, and applying pressure of 0.1-5 MPa to promote mutual sintering of nano silver so as to complete metallurgical interconnection.
The resulting joint of the nano-silver paste of this comparative example has excellent interconnection strength and reliability, but the nano-silver paste cannot be used for interconnection of a complicated structure and a part of materials such as glass, ceramics, etc. due to fluidity of the paste itself and compatibility of materials, but is formed into a preformed sheet, which in turn causes hardening and embrittlement of the materials, making transportation and processing very difficult. The metal aerogel-based preformed sheet has excellent elastic flexibility and deformability, can be processed into various sizes and shapes, is adaptive to match and fill various complex structures and heterogeneous materials, and has obvious processing and application advantages.
Comparative example 3
Dispersing metal particles with the particle size of about 10-50 mu m or plastic pellets plated with a metal coating on the surface in a resin material matrix to prepare anisotropic conductive adhesive, bonding the conductive adhesive between a device to be welded and a substrate, applying pressure of 0.1-1 MPa, and maintaining the pressure at 25-100 ℃ for 30 min to complete connection, wherein the obtained joint has certain heat conductivity and electrical conductivity.
The comparative example mainly relies on the surface wetting power (adhesion) and self-adhesive power (cohesion) of the resin material matrix to combine the two materials together, and the connection can be completed under the condition of extremely low temperature. However, the joint obtained by the conductive adhesive has obviously lower connection strength, electric conduction and heat dissipation performance than that of a metal aerogel-based welding material, the shear strength is generally not more than 10 MPa, and the heat conductivity is higher than that of a metal aerogel-based welding material<10W/mK, conductivity of about 1-10 x 10-4Omega cm, much lower than the bulk metal material, and is susceptible to material or structural instability at high temperatures. The strength of the metal aerogel interconnecting joint can reach 60 MPa, the heat conductivity can reach 40-50W/mK, and the electric conductivity can reach 1-3 x 10-5Ω cm. In summary, the present invention is relativelyThis comparative example has significant performance advantages.
As can be seen from the comparison between the above embodiment and the comparative example, the metal aerogel based preform sheet adopting the technical scheme of the invention can be used for welding the surfaces of various parts to be welded with complex structures, and the welding temperature is low, but the metal aerogel based preform sheet can be used at high temperature, and the shear strength after welding is higher.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (10)
1. The preparation method of the metal aerogel based preformed soldering lug is characterized by comprising the following steps:
step S1, preparing a metal aerogel matrix, cleaning and cutting the surface of the metal aerogel matrix, and removing residual reagents and uneven areas;
and step S2, compressing the obtained metal aerogel matrix, and cutting to obtain the preformed soldering lug.
2. The method of making a metal aerogel-based preformed solder fillet as in claim 1, wherein: the material of the metal aerogel matrix comprises at least one of silver, copper, nickel, gold and tin.
3. The method of making a metal aerogel-based preformed solder fillet as in claim 1, wherein: the inside of the metal aerogel matrix is a three-dimensional network consisting of metal nanowires, the diameters of the metal nanowires are 20-1000nm, the sizes of gaps among the metal nanowires are 50 nm-10 mu m, and the density is 1-600 mg/cm3(ii) a The thickness of the metal aerogel matrix is 5-100 mm.
4. The method of making a metal aerogel-based preformed solder fillet as in claim 1, wherein: in step S1, the metal aerogel matrix is cross-linked between nanophase by flocculation-freeze solidification or "one-step" liquid phase reduction based on three-dimensional growth activator, and residual solvent is removed by supercritical drying or freeze drying.
5. The method of making a metallic aerogel-based preformed solder fillet of claim 4, wherein:
in step S1, the "one-step" liquid phase reduction based on three-dimensional growth activator to obtain the metal aerogel matrix is prepared by the following steps: adding an active matrix material into a solvent and mixing to obtain a three-dimensional growth active agent; mixing a metal precursor, a surfactant and a three-dimensional growth activator, uniformly stirring, putting into a closed reaction mold, heating, and reacting to obtain a metal aerogel matrix tissue which has the same surface structure as the mold and contains a solvent inside; taking out the aerogel semi-finished product, cleaning to remove residual solvent, free nanowire monomer and active agent, and drying to finally obtain the metal aerogel matrix with the three-dimensional structure;
the active material matrix is one or a mixture of more of lignin, cellulose, amino acid, paraffin materials and decomposition products of the materials.
6. The method of manufacturing a metal aerogel based pre-formed solder tab according to any of claims 1 to 5, wherein: step S1 further includes surface modifying the metallic aerogel matrix; the surface treatment is surface activation, functional group grafting or interface transition material deposition; the deposition of the interface transition material is completed by filling liquid high polymer material monomers and nano particles and adopting chemical plating, electrochemical plating, surface spraying or vapor deposition of Ni, Au, Sn or Ti metal layers.
7. The method of making a metal aerogel-based preformed solder fillet of claim 6, wherein: in the compression process of step S2, the metal aerogel is heated or subjected to a protective, reducing atmosphere.
8. A packaging method of metal aerogel based preformed soldering lug is characterized in that: the metal aerogel based preformed soldering lug is obtained by adopting the preparation method of the metal aerogel based preformed soldering lug as claimed in any one of claims 1 to 7, and the packaging method of the metal aerogel based preformed soldering lug comprises the following steps:
s11, processing the metal aerogel based preformed soldering lug according to the welding structure to adapt the size and the shape;
and S12, placing the metal aerogel based preformed soldering lug processed in the step S11 at a position to be soldered, aligning, pressurizing and applying a soldering load to complete the packaging.
9. The method of encapsulating a metal aerogel-based pre-formed solder tab of claim 8, wherein: in step S12, the region to be welded is a two-dimensional or three-dimensional structure including a concave-convex surface, a curved surface, a sawtooth surface, a circular surface, and a stepped structure.
10. The method of encapsulating a metal aerogel-based pre-formed solder tab of claim 8, wherein: in step S12, the aligning and pressurizing pressure is 0.01-20 MPa, the welding load is strong pressure, temperature, laser, microwave, ultrasound or current, and the welding time is 3S-20 min.
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