CN117123965A - Preparation method and application of novel SnBi-based composite low-temperature solder - Google Patents
Preparation method and application of novel SnBi-based composite low-temperature solder Download PDFInfo
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- 229910000679 solder Inorganic materials 0.000 title claims abstract description 76
- 239000002131 composite material Substances 0.000 title claims abstract description 38
- 238000002360 preparation method Methods 0.000 title claims abstract description 33
- 239000002245 particle Substances 0.000 claims abstract description 87
- 239000000843 powder Substances 0.000 claims abstract description 41
- 238000003466 welding Methods 0.000 claims abstract description 31
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 29
- 239000000956 alloy Substances 0.000 claims abstract description 29
- 229910017482 Cu 6 Sn 5 Inorganic materials 0.000 claims abstract description 19
- 229910052802 copper Inorganic materials 0.000 claims abstract description 15
- 238000007747 plating Methods 0.000 claims abstract description 14
- 229910052718 tin Inorganic materials 0.000 claims abstract description 14
- 238000004519 manufacturing process Methods 0.000 claims abstract description 9
- 238000004806 packaging method and process Methods 0.000 claims abstract description 6
- 239000010949 copper Substances 0.000 claims description 105
- 239000000243 solution Substances 0.000 claims description 28
- 238000005476 soldering Methods 0.000 claims description 22
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 18
- 238000002156 mixing Methods 0.000 claims description 13
- QIGBRXMKCJKVMJ-UHFFFAOYSA-N Hydroquinone Chemical compound OC1=CC=C(O)C=C1 QIGBRXMKCJKVMJ-UHFFFAOYSA-N 0.000 claims description 12
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 claims description 12
- FWPIDFUJEMBDLS-UHFFFAOYSA-L tin(II) chloride dihydrate Chemical compound O.O.Cl[Sn]Cl FWPIDFUJEMBDLS-UHFFFAOYSA-L 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- RSWGJHLUYNHPMX-UHFFFAOYSA-N Abietic-Saeure Natural products C12CCC(C(C)C)=CC2=CCC2C1(C)CCCC2(C)C(O)=O RSWGJHLUYNHPMX-UHFFFAOYSA-N 0.000 claims description 8
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 8
- KHPCPRHQVVSZAH-HUOMCSJISA-N Rosin Natural products O(C/C=C/c1ccccc1)[C@H]1[C@H](O)[C@@H](O)[C@@H](O)[C@@H](CO)O1 KHPCPRHQVVSZAH-HUOMCSJISA-N 0.000 claims description 8
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- KHPCPRHQVVSZAH-UHFFFAOYSA-N trans-cinnamyl beta-D-glucopyranoside Natural products OC1C(O)C(O)C(CO)OC1OCC=CC1=CC=CC=C1 KHPCPRHQVVSZAH-UHFFFAOYSA-N 0.000 claims description 8
- 238000004140 cleaning Methods 0.000 claims description 7
- 230000005496 eutectics Effects 0.000 claims description 7
- KWSLGOVYXMQPPX-UHFFFAOYSA-N 5-[3-(trifluoromethyl)phenyl]-2h-tetrazole Chemical compound FC(F)(F)C1=CC=CC(C2=NNN=N2)=C1 KWSLGOVYXMQPPX-UHFFFAOYSA-N 0.000 claims description 6
- 239000002202 Polyethylene glycol Substances 0.000 claims description 6
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 6
- 229960001484 edetic acid Drugs 0.000 claims description 6
- 229920001223 polyethylene glycol Polymers 0.000 claims description 6
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 6
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 6
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 6
- 229910001379 sodium hypophosphite Inorganic materials 0.000 claims description 6
- 239000006185 dispersion Substances 0.000 claims description 5
- 238000004100 electronic packaging Methods 0.000 claims description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000005554 pickling Methods 0.000 claims description 4
- 239000002243 precursor Substances 0.000 claims description 4
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 239000006228 supernatant Substances 0.000 claims description 4
- 229940057995 liquid paraffin Drugs 0.000 claims description 3
- 239000011259 mixed solution Substances 0.000 claims description 3
- 229910000570 Cupronickel Inorganic materials 0.000 claims description 2
- 239000002253 acid Substances 0.000 claims description 2
- JRBRVDCKNXZZGH-UHFFFAOYSA-N alumane;copper Chemical compound [AlH3].[Cu] JRBRVDCKNXZZGH-UHFFFAOYSA-N 0.000 claims description 2
- YOCUPQPZWBBYIX-UHFFFAOYSA-N copper nickel Chemical compound [Ni].[Cu] YOCUPQPZWBBYIX-UHFFFAOYSA-N 0.000 claims description 2
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical class [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 claims description 2
- TVZPLCNGKSPOJA-UHFFFAOYSA-N copper zinc Chemical compound [Cu].[Zn] TVZPLCNGKSPOJA-UHFFFAOYSA-N 0.000 claims description 2
- 239000007788 liquid Substances 0.000 claims description 2
- 239000011812 mixed powder Substances 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 238000003756 stirring Methods 0.000 claims description 2
- 238000000034 method Methods 0.000 abstract description 25
- 230000008569 process Effects 0.000 abstract description 11
- 238000007254 oxidation reaction Methods 0.000 abstract description 4
- 230000003647 oxidation Effects 0.000 abstract description 3
- 239000000126 substance Substances 0.000 abstract description 3
- 239000011159 matrix material Substances 0.000 abstract description 2
- 229910020830 Sn-Bi Inorganic materials 0.000 abstract 1
- 229910018728 Sn—Bi Inorganic materials 0.000 abstract 1
- 230000004907 flux Effects 0.000 abstract 1
- 238000012512 characterization method Methods 0.000 description 8
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 238000007772 electroless plating Methods 0.000 description 6
- 230000004048 modification Effects 0.000 description 6
- 238000012986 modification Methods 0.000 description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 5
- 238000005275 alloying Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 238000005204 segregation Methods 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 239000002105 nanoparticle Substances 0.000 description 3
- 238000001132 ultrasonic dispersion Methods 0.000 description 3
- 238000005219 brazing Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229910008433 SnCU Inorganic materials 0.000 description 1
- 229910006913 SnSb Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000007771 core particle Substances 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000006023 eutectic alloy Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000012536 packaging technology Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Classifications
-
- 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
Abstract
Preparation method and application of novel SnBi-based composite low-temperature solder mainly comprising SnBi-based alloy powder and Sn or Cu 3 Sn、Cu 6 Sn 5 Coated Cu-based particles and flux paste. The low-temperature welding is satisfied, and meanwhile, excellent electric conduction and heat conduction properties are achieved. The invention suppresses oxidation of Cu-based particles and also blocks metallurgical behavior between Cu-based particles and Sn-Bi alloys. In the post-weld structure, the Cu particles are micro-melted or unmelted and still stably exist in the solder matrix. The introduction of the Sn phase to form a hypereutectic structure avoids the enrichment of Bi caused by the deviation of Sn consumption from the hypereutectic structure during welding, so that the composite solder has more excellent performance and service stability. Meanwhile, the Cu-based particles are adopted to reduce the cost, the chemical plating process is simple, and the application prospect of the SnBi-based solder in the field of advanced electronic manufacturing and chip packaging is expanded.
Description
Technical Field
The invention relates to the field of low-temperature brazing, in particular to a preparation method and application of novel SnBi-based composite low-temperature brazing filler metal.
Background
With the development of lead-free solder paste in the electronics industry, lead-free solder pastes including SnCu, snAg, snAgCu, snBi, snZn and SnSb solders have been rapidly developed. And the method is extremely important to develop a low-temperature lead-free solder with excellent performance in facing to the preparation needs of multi-stage micro-welding spots of a multi-stage complex packaging structure in the new-era manufacturing industry. The low temperature lead-free solders mainly used in the market at present include SnBi, snIn, snZn and the like. Among them, snBi low-temperature solder is considered to be one of the more desirable low-temperature lead-free solders because of its excellent creep resistance, relatively low melting point (139 ℃) and low cost.
However, the brittleness and poor electrical and thermal conductivity of SnBi low temperature solders limit their application in the field of electronic packaging. Therefore, modification of the SnBi low-temperature solder to obtain excellent comprehensive properties has become a research hotspot in the field of electronic packaging, and modification of the SnBi-based solder is currently performed mainly by adjusting the Bi phase concentration, or performing alloying and nanoparticle addition. Such as GNSs, ni nanoparticles, al 2 O 3 Addition of particles, ag, al, sn and Zn elements. However, adjusting the phase concentration may deviate from the eutectic point, resulting in a larger two-phase region that is detrimental to the wetting process; alloying is not beneficial to the stable existence of eutectic structures; the addition of inorganic nonmetallic nano particles has the problems of agglomeration with different degrees and interface bondability of the composite material, and the modification means mainly improves a specific property of the solder tin paste, which is not beneficial to the improvement of the comprehensive property under commercial conditions.
Because the SnBi alloy solder has excellent creep resistance, compared with the improvement of mechanical properties, the improvement of electric conduction and heat conduction properties is more important to solve the problem of microcrack expansion caused by Bi phase segregation in the service process caused by electromigration and thermomigration.
Most of the current researches focus on the application of the traditional surface mounting field, but with the development of the electronic packaging industry to higher density integration, sequential proposals of concepts such as chip (core particle) and 3D chip and the like, the chip packaging structure is more complicated and integrated, and the application of SnBi in the field of narrow-space micro-solder joint interconnection is also an important problem to be considered in the modification design process in the face of multi-stage micro-solder joint manufacturing in the chip packaging field. Therefore, the development of microelectronic packaging technology at present needs a low-temperature lead-free solder with excellent comprehensive performance and lower cost.
Disclosure of Invention
The invention aims to solve the problems of Bi phase offset and the like generated in the service process of a welding structure due to poor electric conduction and heat conduction performance of SnBi-based low-temperature lead-free solder in the prior art, and provides a novel preparation method and application of the SnBi-based composite low-temperature solder. The novel SnBi-based low-temperature lead-free solder has the advantages of excellent comprehensive physical properties, stable structure, wide application and the like.
In order to achieve the above purpose, the invention adopts the following technical scheme:
novel SnBi-based composite low-temperature solder added with nano-or micron-sized Sn or Cu 3 Sn、Cu 6 Sn 5 The coated Cu-based particles, the SnBi alloy powder and the soldering paste are uniformly mixed to prepare the novel solder paste. The main component of the soldering paste is rosin, the mass ratio of the soldering paste is 10% -20%, and the balance is Sn or Cu 3 Sn、Cu 6 Sn 5 Coated Cu-based particles and SnBi-based alloy powder.
Sn or Cu 3 Sn、Cu 6 Sn 5 The coating of the solder paste enables the addition of Cu-based particles in the SnBi-based solder paste to well improve the electric conductivity and the heat conductivity of the solder paste, and meanwhile, the Sn phase is introduced into the solder structure to avoid the Bi segregation problem caused by Sn consumption in the welding process. In addition, sn or Cu 3 Sn、Cu 6 Sn 5 The coating of the composite solder ensures that the Cu-based particles have excellent stability and oxidation resistance, the overall performance of the composite solder is improved, the structure is stable, the preparation process is simple, and the cost is lower.
A preparation method of novel SnBi-based composite low-temperature solder comprises the following steps:
1) Washing Cu powder with acid to remove an oxide layer, then cleaning and drying for later use;
2) Preparing a precursor A solution of Sn plating solution, wherein the preparation method comprises the following steps: thiourea, citric acid, sodium hypophosphite, hydroquinone, polyethylene glycol, ethylene diamine tetraacetic acid and polyvinylpyrrolidone are heated and stirred to be dissolved in deionized water;
3) The preparation method of the solution B of the Sn plating solution comprises the following steps: dissolving stannous chloride dihydrate in aqueous hydrochloric acid;
4) Adding the solution B into the solution A under stirring, uniformly mixing, and regulating the pH;
5) Adding the Cu powder obtained in the step 1) after pickling and drying into the mixed solution obtained in the step 4) for dispersion;
6) Cleaning and drying the powder after the supernatant liquid is removed in the step 5) to obtain Sn-coated Cu-based particles;
7) And (3) mixing the Sn-coated Cu-based particles obtained in the step (6) with SnBi-based alloy powder, and then adding rosin-based soldering paste for mixing to complete the preparation of the novel SnBi-based composite low-temperature solder.
In the step 6), the Sn-coated Cu-based particles are reacted in liquid paraffin under the heating condition, and then are centrifuged and ultrasonically cleaned to obtain Cu 3 Sn or Cu 6 Sn 5 Coated Cu-based particles; in step 7), the Cu is reacted with 3 Sn or Cu 6 Sn 5 After the coated Cu-based particles are mixed with the SnBi alloy powder, rosin-based soldering paste is added for mixing, and the novel SnBi-based composite low-temperature solder is prepared. The heating temperature is 140-180 ℃ and the reaction time is 12-20 h.
In the step 2), the concentration of the component A is as follows: 70-1120 g/L of thiourea, 15-18 g/L of citric acid, 50-160 g/L of sodium hypophosphite, 1.2-11.8 g/L of hydroquinone, 5g/L of polyethylene glycol, 0.7-1.2 g/L of ethylenediamine tetraacetic acid and 1.5-1.8 g/L of polyvinylpyrrolidone; in the step 3), the concentration of the component of the solution B is as follows: 18-21 g/L stannous chloride dihydrate.
In the step 4), the pH is 2-3.
The particle diameter of the coated Cu-based particles is 0.1-50 mu m, and the particle diameter of the SnBi alloy powder is 20-50 mu m.
The SnBi-based alloy powder comprises at least one of eutectic or hypoeutectic SnBi, snBiAg, snBiSb, snBiCuAg, snBiIn or SnBiInAg; the Cu-based particles comprise at least one of pure copper, copper zinc, copper aluminum, copper nickel and copper tin alloy. According to the particle size requirement of the powder, the SnBi alloy powder is obtained by atomizing and pulverizing.
Sn or Cu 3 Sn、Cu 6 Sn 5 In the mixed powder of the coated Cu-based particles and the SnBi-based alloy powder, the mass ratio of the SnBi-based alloy powder is 70-90%, preferably 80-90%; sn or Cu 3 Sn、Cu 6 Sn 5 The mass ratio of the coated Cu-based particles is 10-30%, preferably 10-20%.
The prepared novel SnBi-based composite low-temperature solder is applied to the SMT electronic manufacturing industry of traditional electronic packaging and multistage micro-welding spots of advanced packaging structures, and the temperature is 150-180 ℃ and the time is 3-5 minutes through reflow soldering.
More preferably, in the weld joint structure of the invention, cu-based particles stably exist in the weld joint solder alloy and have excellent electric and heat conduction characteristics, the weld joint matrix structure is a eutectic SnBi alloy structure, the eutectic structure is uniform without dendrite, the surface of Cu-based particle powder is uniformly coated with intermetallic compounds, and the main component of the Cu-based particle powder is Cu 3 Sn or Cu 6 Sn 5 。
The invention can also carry out solder application on solder foils of the composite material, which are prepared by remelting and alloying the solder paste.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
1. compared with the scheme of modifying only the single performance of the SnBi-based solder in the prior art, the invention adopts the Sn or Cu doped method 3 Sn、Cu 6 Sn 5 The coated Cu-based particles are modified, so that the electric conductivity and the heat conductivity of the coated Cu-based particles can be remarkably improved, meanwhile, sn is introduced to form a hypereutectic structure, the problem of Bi segregation caused by Sn phase consumption in the welding process can be effectively solved, and the improvement of the comprehensive performance is achieved.
2. The invention adopts Cu or alloy particles thereof with low cost for modification, has low price and simple production procedures, and is suitable for mass industrial production.
3. The invention adopts a simpler chemical plating process to carry out surface coating modification on the second phase Cu or the alloy particles thereof, and the Sn is plated on the surfaces of the Cu or the alloy particles thereof or the Sn layer is ripened into Cu 3 Sn、Cu 6 Sn 5 The oxidation problem of Cu-based particles in the solder preparation process is effectively improved, the solder structure is stabilized, and the welding performance is improved.
4. The invention improves the chemical plating scheme by ice bath, ultrasonic dispersion and other methods, realizes the quick plating of copper powder tinning, can realize the uniform plating of a Sn layer on the surface of copper powder in 10-20 minutes, and is more suitable for industrial production.
5. The invention ensures the low-temperature welding performance and the practical application performance at the same time, and has low manufacturing cost. Meanwhile, the particle size of the particles can be selected for customized production according to the actual application field, and the application scene is rich.
6. The invention explores the limit of adding the second phase modified Cu-based particles, when the second phase modified Cu-based particles are added to 30%, the second phase modified Cu-based particles are difficult to be applied in a row, the optimal adding amount is 10% -20%, and the second phase modified Cu-based particles can be specifically selected according to the actual using amount.
7. Compared with the traditional technology for preparing the high-temperature-resistant welding spots by the ultrasonic auxiliary welding process through preparing Cu@X particles, the high-temperature-resistant welding spot forming method can be used for preparing the high-temperature-resistant welding spots through the conventional reflow welding process, and the welding spots are compact and uniform and can be used for quickly forming the high-temperature-resistant welding spots.
8. Compared with the traditional welding process for preparing the prefabricated soldering lug by Cu@X core-shell particles, the invention can be used for preparing soldering paste, has controllable welding size and wider application scene.
Drawings
FIG. 1 shows the morphology and EDS characterization results of the novel solder paste of example 3.
Fig. 2 is a structure morphology of a weld joint of practical welding application of the composite solder prepared in example 5 by using a 20 μm-sized Sn layer coated Cu particles with mass fractions of 10%, 20% and 30%, respectively.
Fig. 3 shows the dispersion and EDS characterization results of example 1 after plating a Sn layer on the 1 μm Cu particles using the electroless plating method of the present invention.
FIG. 4 shows that in example 2, a Sn layer was plated on the surface of 1 μm Cu particles by the electroless plating method of the present invention, and then aged to obtain Cu 3 And (5) surface morphology of the Sn-coated Cu particles and EDS characterization results.
FIG. 5 shows that in example 2, a Sn layer was plated on the surface of 1 μm Cu particles by the electroless plating method of the present invention, and then aged to obtain Cu 3 XRD characterization results of Sn-coated Cu particles.
Fig. 6 is a high temperature resistant solder joint of example 7 prepared by a conventional reflow soldering process at 250 c.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved more clear and obvious, the invention is further described in detail below with reference to the accompanying drawings and embodiments.
Example 1
Preparation of Sn-coated Cu-based particles
S1: cu particles with the particle size of 1 micron are adopted, the oxide layer is removed by pickling with dilute hydrochloric acid solution with the mass fraction of 5 percent, and then deionized water and alcohol are alternately cleaned and dried for standby.
S2: the preparation method of the precursor A solution for preparing the Sn plating solution comprises the following steps: thiourea: 80g/L; citric acid: 16g/L; sodium hypophosphite: 40g/L; hydroquinone: 1.6g/L; polyethylene glycol: 5g/L; EDTA (ethylenediamine tetraacetic acid): 0.8g/L; polyvinylpyrrolidone: 1.6g/L, then dissolved in 400ml deionized water at 80℃and 500 rpm.
S3: preparing a solution B of Sn-plated solution, wherein the specific preparation method is stannous chloride dihydrate: 16g/L, then dissolved in aqueous hydrochloric acid to a volume of 50ml.
S4: and adding the solution B into the solution A at the rotating speed of 500rpm, uniformly mixing, and regulating the pH value to be 2.
S5: and adding the acid-washed and dried Cu powder into the bath, adjusting the rotating speed, performing ultrasonic dispersion, and continuously plating in an ice bath environment for 15 minutes to finish.
S6: and (3) removing supernatant from the powder prepared in the step (S4), alternately cleaning by deionized water and alcohol, and drying to prepare the Sn-plated Cu-based particles.
FIG. 3 is a graph showing the results of EDS characterization of FIG. 3 a) and FIG. 3 b) for the dispersion of the Sn layer plated on the surface of a 1 μm Cu particle in example 1 using the electroless plating method of the present invention. The result shows that the micron-sized Cu@Sn particle powder prepared by the method is uniformly dispersed, the surface coating is uniformly plated, and the thickness of the coating is uniform.
Example 2
Cu 3 Preparation of Sn-coated Cu-based particles
S1: cu particles with the particle size of 1 micron are adopted, the oxide layer is removed by pickling with dilute hydrochloric acid solution with the mass fraction of 5 percent, and then deionized water and alcohol are alternately cleaned and dried for standby.
S2: the preparation method of the precursor A solution for preparing the Sn plating solution comprises the following steps: thiourea: 80g/L; citric acid: 16g/L; sodium hypophosphite: 40g/L; hydroquinone: 1.6g/L; polyethylene glycol: 5g/L; EDTA (ethylenediamine tetraacetic acid): 0.8g/L; polyvinylpyrrolidone: 1.6g/L, then dissolved in 400ml deionized water at 80℃and 500 rpm.
S3: preparing a solution B of Sn-plated solution, wherein the specific preparation method is stannous chloride dihydrate: 16g/L, then dissolved in aqueous hydrochloric acid to a volume of 50ml.
S4: and adding the solution B into the solution A at the rotating speed of 500rpm, uniformly mixing, and regulating the pH value to be 2.
S5: and adding the acid-washed and dried Cu powder into the bath, adjusting the rotating speed, performing ultrasonic dispersion, and continuously plating in an ice bath environment for 15 minutes to finish.
S6: and (3) removing supernatant from the powder prepared in the step (S4), alternately cleaning by deionized water and alcohol, and drying to prepare the Sn-plated Cu-based particles.
S7: and (3) reacting the Cu-based particles plated with Sn in liquid paraffin at 150 ℃ for 12-24 hours, and then alternately centrifuging and ultrasonically cleaning by adopting a mixed solution of n-hexane and alcohol in equal proportion. Wherein centrifugation parameters were 10000 revolutions for 10 minutes.
FIG. 4 shows that in example 2, a Sn layer was plated on the surface of 1 μm Cu particles by the electroless plating method of the present invention, and then aged to obtain Cu 3 Surface morphology of Sn-coated Cu particles fig. 4 a) and EDS characterization results fig. 4 b). FIG. 5 shows that in example 2, a Sn layer was plated on the surface of 1 μm Cu particles by the electroless plating method of the present invention, and then aged to obtain Cu 3 XRD characterization results of Sn-coated Cu particles. The above results show that Cu@Cu prepared by the method of the invention 3 Sn particles, surface Sn layer is converted into Cu 3 Sn, the surface distribution is uniform, and the particle dispersion degree is good.
Example 3
Preparation of SnBi composite solder paste added with Sn-coated Cu powder
Sn-coated Cu particles with the particle size of 20 microns are prepared according to the scheme of the embodiment 1, and then are mixed with SnBi alloy powder with the particle size of 40-50 microns according to the mass ratio of 2:8, and then are added with the low-temperature rosin-based soldering paste for mixing. And (5) preparing the novel solder paste. The novel composite soldering paste is suitable for multi-scene application. The basic physical properties of the novel composite solder and the SnBi eutectic alloy are compared after remelting alloying, and detailed results are shown in table 1, and the addition of Cu-based particles after Sn cladding can greatly improve the electric conductivity and the heat conductivity of the composite solder alloy. Fig. 1 a) shows the structure morphology diagram of the novel solder paste in example 3, and fig. 1 b) shows the EDS characterization diagram result.
TABLE 1
Example 4
Addition of Cu 3 Preparation of SnBi composite solder paste of Sn-coated Cu powder
Cu having a particle size of about 20 μm was first prepared according to the procedure of example 2 3 And mixing the Sn-coated Cu powder with SnBi alloy powder with the particle size of 40-50 microns according to the mass ratio of 1:9, and adding the low-temperature rosin-based soldering paste for mixing. And (5) preparing the novel solder paste. The novel composite soldering paste is suitable for multi-scene application.
Example 5
SnBi composite solder paste welding application of Cu powder coated by Sn
The novel solder paste in the embodiment 3 is coated on the surface of a bonding pad of an electronic component to be welded, and then the bonding pad is reflowed for 5 minutes at 150 ℃ to finish the bonding of the bonding pad.
Fig. 2 is a structure morphology of a weld joint of practical welding application of the composite solder prepared in example 5 by using a 20 μm-sized Sn layer coated Cu particles with mass fractions of 10%, 20% and 30%, respectively. The SEM result of the welding seam shows that the welding seam structure prepared by the novel composite soldering paste is compact, the thickness of the compound at the interface is uniform, and no obvious holes are generated near the second phase particles.
Example 6
Addition of Cu 3 SnBi composite solder paste welding application of Sn-coated Cu powder
The novel solder paste in example 4 was applied to the surface of the electronic component pad to be soldered, and then reflowed at 150 ℃ for 5 minutes to complete the chip soldering.
Example 7
The Sn coated Cu powder and the SnBi alloy powder are rolled into prefabricated soldering lug after being pressed into sheets, and reflow soldering is carried out on the clean Cu bonding pad coated with rosin at the temperature of 250 ℃. Fig. 6 is a high temperature resistant solder joint of example 7 prepared by a conventional reflow soldering process at 250 c. The result shows that the prefabricated welding lug can realize successful welding, and the welding rate meets the practical application.
In the present invention, sn or Cu 3 Sn、Cu 6 Sn 5 The coating of the Cu-based particles ensures that the Cu-based particles have excellent electric conductivity and heat conductivity and are low in price, so that the oxidization problem of the Cu-based particles in the preparation process can be solved. The Cu-based particle powder can be better infiltrated in the SnBi tissue, and can be stably existing in the solder paste. Wherein the surface of Cu-based particles is coated with Sn or Cu 3 Sn、Cu 6 Sn 5 The Sn phase structure in the SnBi-based alloy can be infiltrated on the surface, and Bi phase enrichment caused by diffusion is reduced, so that the problems of holes, microcracks and the like caused by Bi phase enrichment of a welding structure in the service process are avoided. At the same time Sn or Cu 3 Sn、Cu 6 Sn 5 The coated Cu-based particle powder is stably existing in the solder alloy and the welding structure, and the Cu has more excellent electric conduction and heat conduction properties, so that the electric conduction and heat conduction properties of the solder structure are more excellent, and the failure of the welding structure caused by the problems of thermal migration, electromigration and the like is avoided.
In conclusion, the invention ensures that the solder reacts with the Cu substrate and does not consume excessive Sn when soldering is performed, so that the solder is stabilized near the eutectic component, the segregation problem of Bi is avoided, and the performance is more excellent.
Claims (10)
1. The preparation method of the novel SnBi-based composite low-temperature solder is characterized by comprising the following steps of:
1) Washing Cu powder with acid to remove an oxide layer, then cleaning and drying for later use;
2) Preparing a precursor A solution of Sn plating solution, wherein the preparation method comprises the following steps: thiourea, citric acid, sodium hypophosphite, hydroquinone, polyethylene glycol, ethylene diamine tetraacetic acid and polyvinylpyrrolidone are heated and stirred to be dissolved in deionized water;
3) The preparation method of the solution B of the Sn plating solution comprises the following steps: dissolving stannous chloride dihydrate in aqueous hydrochloric acid;
4) Adding the solution B into the solution A under stirring, uniformly mixing, and regulating the pH;
5) Adding the Cu powder obtained in the step 1) after pickling and drying into the mixed solution obtained in the step 4) for dispersion;
6) Cleaning and drying the powder after the supernatant liquid is removed in the step 5) to obtain Sn-coated Cu-based particles;
7) And (3) mixing the Sn-coated Cu-based particles obtained in the step (6) with SnBi-based alloy powder, and then adding rosin-based soldering paste for mixing to complete the preparation of the novel SnBi-based composite low-temperature solder.
2. The preparation method of the novel SnBi-based composite low-temperature solder according to claim 1, which is characterized in that: in the step 6), the Sn-coated Cu-based particles are reacted in liquid paraffin under the heating condition, and then are centrifuged and ultrasonically cleaned to obtain Cu 3 Sn or Cu 6 Sn 5 Coated Cu-based particles; in step 7), the Cu is reacted with 3 Sn or Cu 6 Sn 5 After the coated Cu-based particles are mixed with the SnBi alloy powder, rosin-based soldering paste is added for mixing, and the novel SnBi-based composite low-temperature solder is prepared.
3. The preparation method of the novel SnBi-based composite low-temperature solder according to claim 2, which is characterized in that: the heating temperature is 140-180 ℃ and the reaction time is 12-20 h.
4. The preparation method of the novel SnBi-based composite low-temperature solder according to claim 1, which is characterized in that: in the step 2), the concentration of the component A is as follows: 70-1120 g/L of thiourea, 15-18 g/L of citric acid, 50-160 g/L of sodium hypophosphite, 1.2-11.8 g/L of hydroquinone, 5g/L of polyethylene glycol, 0.7-1.2 g/L of ethylenediamine tetraacetic acid and 1.5-1.8 g/L of polyvinylpyrrolidone; in the step 3), the concentration of the component of the solution B is as follows: 18-21 g/L stannous chloride dihydrate.
5. The preparation method of the novel SnBi-based composite low-temperature solder according to claim 1, which is characterized in that: in the step 4), the pH is 2-3.
6. The preparation method of the novel SnBi-based composite low-temperature solder according to claim 1 or 2, which is characterized in that: the particle diameter of the coated Cu-based particles is 0.1-50 mu m, and the particle diameter of the SnBi alloy powder is 20-50 mu m.
7. The preparation method of the novel SnBi-based composite low-temperature solder according to claim 1, which is characterized in that: the SnBi-based alloy powder comprises at least one of eutectic or hypoeutectic SnBi, snBiAg, snBiSb, snBiCuAg, snBiIn or SnBiInAg; the Cu-based particles comprise at least one of pure copper, copper zinc, copper aluminum, copper nickel and copper tin alloy.
8. The preparation method of the novel SnBi-based composite low-temperature solder according to claim 1 or 2, which is characterized in that: sn or Cu 3 Sn、Cu 6 Sn 5 In the mixed powder of the coated Cu-based particles and the SnBi-based alloy powder, the mass ratio of the SnBi-based alloy powder is 70-90%, preferably 80-90%; sn or Cu 3 Sn、Cu 6 Sn 5 The mass ratio of the coated Cu-based particles is 10-30%, preferably 10-20%.
9. The novel SnBi-based composite low-temperature solder prepared by the preparation method of any one of claims 1 to 8.
10. The use of the novel SnBi-based composite low temperature solder according to claim 9, wherein: the multi-stage micro-welding spot is applied to the SMT electronic manufacturing industry of traditional electronic packaging and advanced packaging structure, and the temperature is 150-180 ℃ and the time is 3-5 minutes through reflow soldering.
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