CN112475663B - Preparation method of lead-free composite soldering paste with high spreading rate - Google Patents
Preparation method of lead-free composite soldering paste with high spreading rate Download PDFInfo
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- CN112475663B CN112475663B CN202011287350.2A CN202011287350A CN112475663B CN 112475663 B CN112475663 B CN 112475663B CN 202011287350 A CN202011287350 A CN 202011287350A CN 112475663 B CN112475663 B CN 112475663B
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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
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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
Abstract
A process for preparing the lead-free composite solder paste with high spreading rate includes such steps as preparing the nano Sb2SnO5Granule addingAdding into tin-based solder paste, stirring at low temperature to obtain nanometer Sb2SnO5The particles are uniformly distributed in the tin-based solder paste to obtain the composite solder paste. The lead-free composite solder paste prepared by the method has high spreading rate and reliability, low resistivity and low preparation process and cost.
Description
Technical Field
The invention relates to the technical field of preparation methods of lead-free solder pastes, in particular to a preparation method of a lead-free composite solder paste with high spreading rate.
Background
The electronic industry is one of the most rapidly developing industries, particularly the promotion of automation and intellectualization, electronic products are the most important necessities of human beings, and assembly materials play a decisive role in the quality of the electronic products. The lead-free solder alloy is used as the most basic material of an electronic assembly process, the performance of the lead-free solder alloy is one of the focuses of the electronic packaging technical field, and the excellent weldability can effectively reduce the problems of insufficient solder, missing solder and the like generated in the welding process.
On the other hand, the electronic products are being miniaturized and miniaturized at present, and the required welding solder is less and less, which puts higher requirements on the performance of the solder, so that the solder alloy is required to have excellent welding performance, and the quality after welding is ensured. The appearance of the IMC layer of the intermetallic compound at the welding interface has important influence on the quality after welding, and the intermetallic compound layer formed at the welding interface is often uneven due to the particularity of welding materials, so that the reliability of a welding joint is reduced. Controlling the appearance of the welding interface and obtaining a welding interface with moderate, uniform and smooth thickness is also a goal pursued by solder developers.
Research finds that the trace Ag and Sn of the alloy matrix can form dispersed high-melting-point Ag3Sn particles, thereby improving the nucleation capability of the alloy and reducing the mass point diffusion capability in the matrix, and the addition of Ag element in the solder alloy can effectively improve the microstructure, reliability, mechanical property, electrical property, welding property and the like of the alloy. However, since the price of Ag element is relatively high, it is one of the research directions of solder developers to reduce the content of Ag element.
Sb2SnO5As an excellent conductive material, nanoparticle Sb thereof2SnO5The conductivity and wettability of the alloy can be improved, and the growth of alloy crystal grains can be inhibited, and the mechanism is as follows:
first, alloy oxide HmH higher than that of the simple substance of the alloymAnd Sb2SnO5V of similar composition to tin solder alloymThe values are similar, then the nano Sb2SnO5H of the particlesm/VmH of a value higher than that of the solder alloy elementm/VmIn the molten state, nano Sb2SnO5The tendency of the particles to be segregated on the surface of the melt is higher than that of the solder alloy elements, so that the surface tension of the solder alloy melt is reduced, and the spreadability of the solder alloy is improved;
second, Sb2SnO5Is Sb doped SnO2The product of (1) is essentially metal oxide, and when in welding, acidic substances in the solder paste can be mixed with Sb2SnO5Partial reaction, namely quickly releasing gas to expand the alloy melt and indirectly promote the melt to expand on the surface of the copper sheet, so that the wettability of the solder alloy to the copper sheet is indirectly improved;and because of the full stirring when mixing the solder paste, the nano Sb is uniformly distributed in the whole solder paste2SnO5Particle, when welding, whole fuse-element all is producing gas, promotes the fuse-element inflation and simultaneously more can reduce the bubble volume inside static (welding completion) solder joint: during welding, compared with the traditional solder paste which is closed and does not bubble during melting, the welding spot which bubbles rapidly is favorable for removing internal bubbles, and the rest bubbles are caused by Sb2SnO5The reliability of the fine bubbles generated by continuous reaction with the acidic material is higher than that of the welding spot containing large bubbles.
When the high-melting-point refractory nanoparticles are added, because the nanoparticles are lighter relative to a melt and easily adsorb oxygen to form an oxide film between the nanoparticles and the melt, if a vacuum melting or atmosphere protection means is not adopted, the nanoparticles and the melt are always separated by a thicker oxide film, so that when the nanoparticles are directly added into the melt, the nanoparticles hardly enter the melt, and the nanoparticles are easily agglomerated, and the effect of inhibiting the abnormal growth of tissues by the nanoparticles is reduced. In order to solve the problem, researchers often ball mill and mix the nano particles and the solder, and then prepare the composite solder by a powder metallurgy method, but the preparation period is long, and the energy consumption is high.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a preparation method of a composite soldering paste with high spreading rate, which can effectively improve the spreadability of a welding spot, reduce the bubble size of the welding spot, has simple preparation process and low solder preparation cost.
The technical scheme adopted by the invention is as follows:
a process for preparing the lead-free composite solder paste with high spreading rate includes such steps as preparing the nano Sb2SnO5Adding the particles into tin-based solder paste, and stirring at low temperature to obtain nanometer Sb2SnO5The particles are uniformly distributed in the tin-based solder paste to obtain the composite solder paste.
Further, the stirring at low temperature is carried out by stirring with an electromagnetic stirrer under the condition of low-temperature circulating water, wherein the stirring speed is 20-40r/min, the temperature of the circulating water is 18-22 ℃, and the stirring is carried out at the temperature of 25-35 min.
Further, the nano Sb2SnO5The average particle diameter of the particles is 20-100 nm.
Further, the tin-based solder paste is a lead-free solder paste.
Further, the composite soldering paste contains nano Sb2SnO50.1-3.0 wt% of particles, 97.0-99.9 wt% of tin-based solder paste.
The method and the prepared composite soldering paste have the following beneficial effects:
(1) nano Sb used in the invention2SnO5The particles have high conductivity, can effectively replace Ag element to refine the alloy matrix, inhibit the abnormal growth of interface layer tissues and improve the conductivity of the solder. Nano Sb2SnO5The particles containing O element and Sb element2SnO5The solder paste has certain anti-oxidation effect. In addition, Sb2SnO5Is an oxide which is easy to react with acid, and part of Sb is Sb during welding2SnO5And the solder paste can react with acid substances in the solder paste to release gas, so that the fluidity of the alloy is improved, and the spreading rate of the welding spot is improved. The invention adds high-conductivity nano-particles into tin-based lead-free solder paste and uses conductive material nano Sb2SnO5The particles replace high-cost Ag element, so that the cost of the composite soldering paste is effectively reduced, and the better conductivity and reliability of the soldering paste are still maintained;
(2) compared with a vacuum smelting method and a powder metallurgy method, the composite soldering paste containing the nano particles is prepared by mixing the soldering paste, no impurity is introduced, the preparation cost is lower, the preparation process flow is short, and the preparation process problems of more impurities, long preparation period and high cost caused by the vacuum smelting casting method and the powder metallurgy method are effectively solved;
(3) when the composite soldering paste is used for soldering, part of nano Sb in the soldering paste is in nano-Sb2SnO5The particles react with acidic substances to release gas, and in the process, the gas continuously generated in the solder paste can push the solder paste to flow around, so that the fluidity of the solder paste is indirectly improved, and the spreading rate of the welding spots is improved;
(4) when the composite soldering paste is used for soldering, the nano Sb in the solder paste is2SnO5The particles and acidic substances react rapidly to release gas, and the alloy melt in the welding spot is in a boiling state for a short time, so that the melt can be promoted to remove internal gas;
(5) nano Sb2SnO5The particles have a higher H than other atoms in the alloy meltm/VmThe tendency of the surface of the partially-gathered melt is higher, so that the surface energy of the melt is effectively reduced, and the spreadability of a welding spot is improved;
(6) nano Sb2SnO5The particles still have stable thermal properties at 600 ℃, and have positive effects on improving the reliability of the solder;
(7) the method is simple, has low preparation cost, can effectively improve the spreadability of the soldering paste and the alloy micro-texture structure, reduces the bubble size of the welding spot, and improves the welding performance, the electric conductivity and the reliability.
Drawings
FIG. 1 shows the compound solder paste prepared by the method of the present invention and the solder paste without Sb2SnO5Comparing gold phase diagrams of the SnCu lead-free solder paste of the nano particles;
FIG. 2 is a graph comparing the spreading rates of solder joints;
FIG. 3 shows the compound solder paste prepared by the method of the present invention and the solder paste without Sb2SnO5Comparing gold phase diagrams of SnAgCu lead-free solder paste of the nano particles;
FIG. 4 shows the compound solder paste prepared by the method of the present invention and the solder paste without Sb2SnO5And (3) a welding spot nondestructive inspection comparison graph of the SnAgCu lead-free solder paste of the nano particles.
Detailed Description
The invention will be further described with reference to the drawings and the embodiments without limiting the scope of the invention thereto.
Example 1
A process for preparing the lead-free composite solder paste with high spreading rate includes such steps as mixing 1 wt% of nano Sb2SnO5Adding the particles into 99 wt% lead-free SnAg0.3Cu0.7 solder paste, and using electricityStirring by a magnetic stirrer under the condition of low-temperature circulating water to ensure that the nano Sb2SnO5The particles are uniformly distributed in the tin-based solder paste to obtain the composite solder paste. The stirring speed of the electromagnetic stirrer is 40r/min, the temperature of circulating water is 18 ℃, and the stirring is carried out for 25min under the condition of heat preservation. The nano Sb2SnO5The average particle diameter of the particles is 20-50 nm. The prepared composite soldering paste contains nano Sb2SnO51 wt% and 99 wt% of particles. And refrigerating the prepared composite soldering paste for later use.
The lead-free composite solder paste prepared in this example and no Sb added2SnO5Comparison of nano-particle snag0.3cu0.7 lead-free solder pastes, as shown in fig. 1-4:
in FIG. 1, (a) is the gold phase diagram of SnAg0.3Cu0.7 solder paste in the prior art, and (b) is SnAg0.3Cu0.7-1.0Sb prepared by the method of the invention2SnO5The golden phase diagram of the lead-free composite solder paste is shown in figure 1, and the lead-free composite solder paste prepared by the method has finer grains and improved microstructure compared with the solder paste in the prior art.
FIG. 2(c) shows the spreading rate of the solder joint (No. 60) of the SnAg0.3Cu0.7 solder in the prior art, and (d) shows the spreading rate of the composite solder paste SnAg0.3Cu0.7-1.0Sb solder prepared by the method of the present invention2SnO5Spreading rate of solder joint (No. 58). As can be seen from fig. 2, the spreading rate of the composite solder paste prepared by the method of the present invention is significantly improved over the solder of the prior art.
FIG. 3 shows the lead-free composite solder paste prepared by the method of the present invention and the solder paste without Sb2SnO5Comparison of gold phase diagrams of nano-particle SnAgCu lead-free solder pastes. Fig. 3 (e) is a gold phase diagram of the sn0.3ag0.7cu solder paste of the prior art, and (f) is a gold phase diagram of the snag0.3cu0.7-1.0Sb2SnO5 lead-free composite solder paste prepared by the method of the present invention, and it can be seen from comparison of fig. 3 that the average layer thickness of the interface of the lead-free composite solder paste prepared by the method of the present invention is reduced compared with the average layer thickness of the solder paste of the prior art.
Fig. 4 shows the nondestructive inspection comparison of the solder joint of the composite solder paste prepared by the method of the present invention and the SnAgCu leadless solder paste without Sb2SnO5 nano-particles, wherein (g) in fig. 4 is the nondestructive inspection diagram of the solder joint of the SnAg0.3Cu0.7 solder paste, and (h) is the nondestructive inspection diagram of the solder joint of the SnAg0.3Cu0.7-1.0Sb2SnO5 composite solder paste prepared by the method of the present invention. As can be seen from the comparison of FIG. 4, the lead-free composite solder paste prepared by the method of the present invention has smaller cavities and more reliable solder joints compared with the solder paste of the prior art.
Through detection, the crystal grains of the composite soldering paste are more refined, and the microstructure is improved; the spreading rate is 76.86 percent, which is improved by 13.92 percent compared with the prior Sn0.3Ag0.7Cu solder paste; the average thickness of the interface layer is reduced by 1.90 mu m, which is reduced by 38.9 percent compared with the prior Sn0.3Ag0.7Cu solder paste; the resistivity is reduced to 1.04 x 10-7Omega.m, which is reduced by 14% compared with the existing Sn0.3Ag0.7Cu solder paste.
Example 2
A process for preparing the lead-free composite solder paste with high spreading rate includes such steps as mixing 0.1 wt% of nano Sb2SnO5Adding the particles into 99.9 wt% lead-free SnAg3.0Cu0.5 solder paste, and stirring with an electromagnetic stirrer under the condition of low-temperature circulating water to ensure that the nano Sb is2SnO5The particles are uniformly distributed in the tin-based solder paste to obtain the composite solder paste. The stirring speed of the electromagnetic stirrer is 30r/min, the temperature of circulating water is 20 ℃, and the stirring is carried out for 30min under the condition of heat preservation. The nano Sb2SnO5The average particle diameter of the particles is 60-80 nm. The prepared composite soldering paste contains nano Sb2SnO50.1 wt% of particles and 99.9 wt% of particles. And refrigerating the prepared composite soldering paste for later use.
Through detection, the spreading rate of the composite solder paste is 79.29%, which is improved by 15.52% compared with the existing SnAg3.0Cu0.5 solder paste; the thickness of the interface layer is reduced by 1.76 mu m, which is reduced by 32.2 percent compared with the prior SnAg3.0Cu0.5 soldering paste; the resistivity is reduced to 1.0 multiplied by 10-7Omega.m, which is reduced by 16.7 percent compared with the prior SnAg3.0Cu0.5 solder paste.
Example 3
A process for preparing the lead-free composite solder paste with high spreading rate includes such steps as mixing 3 wt% of nano Sb2SnO5Adding the particles into 97 wt% lead-free solder paste, and stirring with an electromagnetic stirrer under the condition of low-temperature circulating water to obtain nano Sb2SnO5The particles are uniformly distributed in the tin-based solder paste to obtain a compositeSolder paste. The stirring speed of the electromagnetic stirrer is 20r/min, the temperature of circulating water is 22 ℃, and the stirring is carried out for 35min under the condition of heat preservation. The nano Sb2SnO5The average particle diameter of the particles is 50-80 nm. The lead-free solder paste is one of SnCu0.7, Sn42Bi58, Sn95Sb5, Sn91Zn9 and the like. The prepared composite soldering paste contains nano Sb2SnO53 wt% and 97 wt% of particles.
The detection shows that the spreading rate, the metallographic structure, the thickness of the interface layer, the resistivity and the like of the composite solder paste have the same effects as those of the examples 1 and 2.
The invention is not limited to SnCu, SnAgCu, SnBi, SnSb series lead-free solder paste products, other embodiments can be formulated with the parameters of the claims and the specification.
Claims (3)
1. A preparation method of lead-free composite solder paste with high spreading rate is characterized in that nano Sb is added2SnO5Adding the particles into tin-based solder paste, and stirring at low temperature to obtain nanometer Sb2SnO5The particles are uniformly distributed in the tin-based solder paste to obtain the composite solder paste; the nano Sb2SnO5The average particle diameter of the particles is 20-100 nm; the composite soldering paste contains nano Sb2SnO50.1-3.0 wt% of particles, 97.0-99.9 wt% of tin-based solder paste.
2. The preparation method of the lead-free composite solder paste with high spreading rate as claimed in claim 1, wherein the stirring at low temperature is carried out by an electromagnetic stirrer under the condition of low-temperature circulating water, the stirring speed is 20-40r/min, the temperature of the circulating water is 18-22 ℃, and the stirring at low temperature is carried out for 25-35 min.
3. The method for preparing the lead-free composite solder paste with high spreading rate as claimed in claim 1, wherein the tin-based solder paste is a lead-free solder paste.
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| GB415181A (en) * | 1933-03-23 | 1934-08-23 | Henry Ambrose Pudsay Littledal | Improvements in hard soldering mixtures and hard soldering processes |
| US7303698B2 (en) * | 2003-11-19 | 2007-12-04 | E.I. Du Pont De Nemours And Company | Thick film conductor case compositions for LTCC tape |
| JP4953873B2 (en) * | 2007-03-26 | 2012-06-13 | 日本碍子株式会社 | Composite bonding material and bonded body |
| CN107877030B (en) * | 2017-11-07 | 2020-01-14 | 深圳市汉尔信电子科技有限公司 | Nano tin-bismuth composite soldering paste and preparation method thereof |
| CN108326471B (en) * | 2017-12-11 | 2020-11-20 | 安徽信达家居有限公司 | Additive for soldering flux |
| CN111230353B (en) * | 2020-01-19 | 2021-08-17 | 深圳第三代半导体研究院 | Nano Ag-SnO for improving silver electromigration2Preparation method and application of solder paste |
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Address after: 650501 No.2, Yunjing Road, information industry base, Kunming Economic and Technological Development Zone, Yunnan Province Patentee after: YUNNAN TIN NEW MATERIAL Co.,Ltd. Address before: 650501 No.2, Yunjing Road, information industry base, Kunming Economic and Technological Development Zone, Yunnan Province Patentee before: YUNNAN TIN MATERIAL Co.,Ltd. |