CN1389326A - Nano particle reinforced Sn-Pb based composite brazing alloy and its prepn. - Google Patents

Abstract

A nanoparticle-reinforced tin-lead-based composite solder and a preparation method thereof belong to the technical field of metal-based composite materials. The brazing filler metal provided by the present invention is made by mixing granular tin-lead matrix and nano-particle reinforcement, and is characterized in that: the size of the granular tin-lead matrix is between 35-75 μm, wherein the weight percentage of tin 60-65%, the weight percentage of Ce-based mixed rare earth is 0-0.3%, and the rest is lead; the nano-particle reinforcement is TiO ₂ , Al ₂ O ₃ , industrial pure Ag or Cu, and the nominal size is 25 Between -90nm, the volume ratio in the composite solder is 0.5-5%; the solder is prepared by uniformly mixing the above-mentioned granular tin-lead matrix, nano-particle reinforcement and neutral flux, and stirring for 30-40min. Formed into a composite solder paste, the solder joint formed after melting has high creep resistance, and maintains a low melting temperature of the tin-lead solder during the soldering process, good wettability, excellent tensile strength and physical properties and other advantages, and the preparation method is simple, and can be widely used in the fields of electronics or optoelectronics.

Description

Nanoparticle-reinforced tin-lead-based composite solder and preparation method thereof

1. Technical field

A nanoparticle-reinforced tin-lead-based composite solder and a preparation method thereof belong to the technical field of metal-based composite materials.

2. Background technology

Tin-lead solder is widely used in the electronics industry to realize electrical and mechanical connections within components and between components and printed circuit boards. With the miniaturization of components and the development of surface assembly technology, the requirements for microstructure stability, mechanical properties, especially creep resistance of solder are getting higher and higher.

Near the car engine, the ambient temperature in winter can fluctuate in the range of -40°C to 200°C. The solder used in automotive electronics must withstand repeated thermal cycle stress, and also absorb the vibration load of the engine and road surface and the occasional impact encountered by driving. In the optical fiber cable engineering, the connection of the optical fiber is fixed. As time goes by, if the axis vertical plane of the optical fiber gradually deviates from the center due to creep, it will lead to a decrease in the signal transmission intensity. In optoelectronic assemblies, such as the coupling between a solid-state laser chip and a ball lens of an optical fiber, the coupling rate depends on the precise alignment of the axis-perpendicular plane of the optical fiber. The positioning between components must remain precise throughout the operating life. Any displacement caused by creep may affect the transmission quality of the optical signal, or even cause the transmission signal to be completely lost, which actually depends on the creep performance of the solder or Dimensional stability of joints. Therefore, on the basis of maintaining the good performance of tin-lead solder, it is very important to improve its creep resistance. Compared with conventional telecommunications and data communications, military and aerospace electronic equipment requires optical fiber modules to be able to serve in harsh environments such as vibration and acceleration for a long time, and the creep resistance of solder is also required to be higher.

At present, gold-based solder, such as 80Au-20Sn eutectic solder, is widely used in optoelectronic assembly. Although the solder has high creep resistance, the solder has a high melting point (273°C). During the brazing process, often Causes damage to optical fibers or optoelectronic devices, and is expensive.

The tin-lead eutectic or near-eutectic solder has a low melting point (183°C), low price, good brazing process performance, but poor creep resistance. Currently developed lead-free solders, although some lead-free solders have better creep resistance than tin-lead solders, but the melting temperature of these lead-free solders is generally about 40°C higher than that of tin-lead eutectic solders.

In 1998, Bell Laboratories of Lucent in the United States added alumina or titanium oxide nano-particles to 63Sn-37Pb eutectic solder, with sizes of 10nm and 5nm, respectively, and added a volume ratio of 3%, and made composite materials through repeated rolling. The constant-load compression creep rate test was performed on a composite material block with a size of 3.5mm×3.5mm×4.5mm. The results showed that the compression creep resistance of the composite material was better than that of the 80Au-20Sn solder alloy, but it was not tested after the material was melted. The performance test and the test of the required physical properties and process performance when used as a solder, that is, there is no data on whether it can be used as a solder.

3. Contents of the invention

The object of the present invention is to provide a tin-lead-based composite solder reinforced by nanoparticles with high creep resistance and simple preparation method and its preparation method.

The nano-particle-reinforced tin-lead-based composite solder provided by the present invention is made by mixing granular tin-lead matrix and nano-particle reinforcement, and is characterized in that: the size of the granular tin-lead matrix is 35-75 μm Among them, the weight percentage of tin is 60-65%, the weight percentage of Ce-based mixed rare earth is 0-0.3%, and the rest is lead; the nano-particle reinforcement is TiO ₂ , Al ₂ O ₃ metal oxide , Industrial pure metal Ag or Cu, the nominal size is between 25-90nm, and the volume ratio in the composite solder is 0.5-5%.

The preparation method of the tin-lead-based composite solder reinforced by nanoparticles provided by the present invention is characterized in that: uniformly mixing the above-mentioned granular tin-lead matrix, nano-particle reinforcement and neutral flux mechanically, and stirring for 30-40min Composite solder paste is made.

In order to simulate the size and cooling conditions of the actual electronic connection joints, the specimen used in the creep test is a miniature single lap joint, the lap area of the brazing joint is 1mm ² , the thickness of the brazing seam is 0.15mm, and the material to be connected is copper Foil, 0.1mm thick. In order to compare the creep properties of nanoparticle-reinforced composite solder and ordinary tin-lead solder, a tensile-shear creep life test was used. The test was carried out under constant-load tensile conditions. The constant tensile-shear stress of the specimen was 11.27Mpa, and the test temperature When the temperature is 15°C, the breaking time of the sample is its creep life. The spread area test refers to the provisions of the national standard GB11364-89 "Experimental method for spreadability and gap filling of solder". The substrate is a thin copper sheet with a thickness of 0.2mm and a size of 40mm×40mm. The Cu foil was polished with No. 600 sandpaper, washed with absolute ethanol and dried in air. The weight of the solder paste is 0.227g. Weighing with Sartorius electronic balance. The spreading welding test is carried out in the air with HZ-3C computer-controlled reflow welding machine. The five nanoparticle-reinforced tin-lead-based composite solder samples and the 63Sn-37Pb solder samples in the examples were all prepared and tested under the same conditions as above. Other test items include: tensile strength, melting temperature, electrical conductivity, etc.

The test results of the properties of the nanoparticle-reinforced tin-lead-based composite solder are shown in the attached table. The test results show that the nano-particle-reinforced tin-lead-based composite solder has low melting temperature and good wettability (larger spreading area and smaller wetting angle ), excellent tensile strength and physical properties, etc., the nanoparticle-reinforced composite solder joint has a longer creep life and better creep resistance.

4. Specific examples

Example 1: The matrix of nanoparticle-reinforced tin-lead composite solder is 60Sn-40Pb near-eutectic alloy, the nominal size is 35 μm, and the weight percentage of Ce-based mixed rare earth is 0.1%. The nano-particle reinforcement is Al ₂ O ₃ nano-oxide particles, the surface of which is treated with anti-agglomeration, the nominal size is 90nm, and the volume ratio in the composite solder is 0.5%. Weigh 0.024g of Al ₂ O ₃ and 0.01g of the above-mentioned mixed rare earth and 1.36g of no-cleaning neutral flux, put them into a crucible and stir them mechanically for 30min, after mixing evenly, add 10g of 60Sn-40Pb near-eutectic alloy, mechanically Stir for 30 minutes to make a composite solder paste, and store it at low temperature for later use.

Example 2: The matrix of nanoparticle-reinforced tin-lead composite solder is 63Sn-37Pb eutectic alloy, and the nominal size is 43 μm. The nanoparticle-like reinforcement is rutile oxide TiO ₂ , the surface is treated with anti-agglomeration, the nominal size is 70nm, and the volume ratio in the composite solder is 3%. Weigh 0.158g of TiO ₂ and 1.36g of no-cleaning neutral flux, put them into a crucible and stir them mechanically for 40 minutes, after mixing evenly, add 10g of 63Sn-37Pb eutectic alloy, stir them mechanically for 30 minutes to make a composite solder paste , stored at low temperature for later use.

Example 3: The matrix of nanoparticle-reinforced tin-lead composite solder is 65Sn-35Pb near-eutectic alloy, the nominal size is 75 μm, and the weight percentage of Ce-based mixed rare earth is 0.3%. The reinforcement in nanoparticle shape is anatase oxide TiO ₂ , the surface is treated with anti-agglomeration, the nominal size is 50nm, and the volume ratio in the composite solder is 5%. Weigh 0.269g of _TiO2 , 0.03g of the above-mentioned mixed rare earth and 1.36g of no-cleaning neutral flux, put them into a crucible and stir them mechanically for 30min, after mixing evenly, add 10g of 65Sn-35Pb near-eutectic alloy, and stir mechanically for 35min , made of composite solder paste, stored at low temperature for later use.

Example 4: The matrix of nanoparticle-reinforced tin-lead composite solder is 63Sn-37Pb eutectic alloy, and the nominal size is 43 μm. The nanoparticle reinforcement is pure metal Ag with a purity of 99.9%, a nominal size of 35nm, and a volume ratio of 3% in the composite solder. Weigh 0.389g of Ag and 1.36g of no-cleaning neutral flux, put them into a crucible and stir them mechanically for 35min, after mixing evenly, add 10g of 63Sn-37Pb eutectic alloy, stir mechanically for 30min to make a composite solder paste, Store at low temperature for later use.

Example 5: The matrix of nanoparticle-reinforced tin-lead composite solder is 63Sn-37Pb eutectic alloy, and the nominal size is 43 μm. The nanoparticle reinforcement is pure metal Cu with a purity of 99.9%, a nominal size of 25nm, and a volume ratio of 3% in the composite solder. Weigh 0.329g of Cu and 1.36g of no-cleaning neutral flux, put them into a crucible and stir them mechanically for 30min, after mixing evenly, add 10g of 63Sn-37Pb eutectic alloy, and stir mechanically for 40min to make a composite solder paste. Store at low temperature for later use. Attached table: performance test table of tin-lead-based composite solder material reinforced by nanoparticles of embodiments 1 to 5 Example Melting point (°C) Tensile strength (MPa) Spread area(mm ² ) Wetting angle (°) Surface tension (MN/m) Conductivity (%ICAS) relative creep life 63Sn37Pb 183 35.5 106.1 5.7 468 12.28 1 Example 1 183-190 43.7 106.6 7.3 469 12.31 7.0 Example 2 183 46.2 112.7 7.2 469 12.17 4.8 Example 3 183-186 47.5 109.1 7.7 469 12.05 4.4 Example 4 183 34.6 98.8 6.2 468 12.62 40 Example 5 183 48.0 81.8 6.9 469 12.98 6.5

* Relative creep life: if the creep life of 63Sn37Pb eutectic solder joint is 1, it means that the creep life of nanoparticle-reinforced composite solder joint is relative to its creep life multiple. (There are 12 creep test pieces for solder joints).

Claims (2)

1, a kind of Sn-Pb based composite brazing alloy of nano particle enhancing, strengthening body by granular tin lead base body and Nanoparticulate is mixed and made into, it is characterized in that: described granular tin lead base body size is between 35-75 μ m, wherein the percentage by weight of tin is 60-65%, the percentage by weight of Ce base mishmetal is 0-0.3%, and all the other are plumbous; It is TiO that described Nanoparticulate strengthens body ₂, Al ₂O ₃Metal oxide, technical pure metal A g or Cu, nominal size is between 25-90nm, and the volume ratio in composite soldering is 0.5-5%.

2, a kind of preparation method of Sn-Pb based composite brazing alloy of nano particle enhancing is characterized in that: by above-mentioned granular tin lead base body, Nanoparticulate being strengthened body and the evenly mixing of neutral scaling powder machinery, stirring 30-40min makes composite soldering cream.