A low-splash lead-free rosin-coated solder wire

Abstract

The invention relates to the technical field of solder, and in particular to a low-splash lead-free rosin-coated solder wire, wherein the alloy components of the solder wire are: Sn, Sb, Cu, Ge, P, Ga, In, Ni; the solder wire is formed by extrusion molding, and is coated with a flux composed of the following components: rosin resin, maleic anhydride, polyoxypropylene glycerol ether, composite ammonium salt, solvent, sodium carboxymethyl cellulose, polyvinyl butyral. The invention optimizes the alloy components and the flux formula, adds antimony, copper, germanium, phosphorus, gallium, indium and nickel elements, so as to improve the fluidity and wettability of the solder wire, so that the solder is easier to spread during the welding process, and the coated rosin decomposes during the welding process to generate active substances, which can remove oxides on the metal surface, promote good contact between the solder and the metal surface, and further reduce the surface tension of the solder, improve the fluidity of the solder, and thus significantly reduce the spatter rate.

Description

Technical Field

[0001] The invention relates to the technical field of solder, in particular to a low-splash lead-free rosin-coated solder wire. Background Art

[0002] With the enhancement of environmental awareness and the advancement of technology, lead-free solder wire has gradually replaced traditional lead-containing solder wire and become the mainstream. Lead-free solder wire mainly refers to solder alloys that do not contain lead (Pb), usually with tin (Sn) as the main component, and other alloy elements such as silver (Ag), copper (Cu), antimony (Sb), etc. are added to achieve the ideal melting point and mechanical properties. The development of lead-free solder wire is mainly due to the requirements of the EU RoHS Directive, which restricts the use of hazardous substances in electrical and electronic equipment, including lead. Lead-free solder wire not only reduces pollution to the environment, but also improves the safety and reliability of products.

[0003] Although lead-free solder wire has many advantages, there are still some problems in practical application, especially the spatter phenomenon is more serious. Spatter refers to the phenomenon that solder splashes out of the welding area at high temperature during the welding process, which not only wastes solder materials, but also may cause circuit short circuits or other quality problems around the welding points. Although the existing low-splash lead-free solder wire has made certain progress, there are still problems such as high spatter rate, more flux residue and less than ideal welding reliability, which leads to low application efficiency of lead-free solder wire in high-end electronic manufacturing and other fields. Summary of the invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a low-splash lead-free rosin-coated solder wire.

[0005] A low-splash lead-free rosin-coated solder wire, the alloy components of the solder wire and their mass percentages are: Sn 85-92%, Sb 3-7%, Cu 0.5-2%, Ge 0.008-0.015%, P 0.006-0.017%, Ga 0.004-0.009%, In0.003-0.05%, Ni 0.03-0.1%, and the balance is inevitable impurities;

[0006] The solder wire is made by extrusion molding and is coated with a flux composed of the following components by mass: 12-15 parts of rosin resin, 2-4 parts of maleic anhydride, 2-3 parts of polyoxypropylene glycerol ether, 2-3 parts of composite ammonium salt, 450-500 parts of solvent, 12-14 parts of sodium carboxymethyl cellulose, and 24-28 parts of polyvinyl butyral.

[0007] Preferably, the alloy components and their mass percentages are: Sn 88%, Sb 5%, Cu 1%, Ge 0.012%, P 0.010%, Ga 0.005%, In 0.005%, Ni 0.05%, and the remainder is inevitable impurities.

[0008] Preferably, the soldering flux comprises the following components in parts by mass: 14 parts of rosin resin, 2 parts of maleic anhydride, 2 parts of polyoxypropylene glycerol ether, 3 parts of complex ammonium salt, 460 parts of solvent, 13 parts of sodium carboxymethyl cellulose, and 25 parts of polyvinyl butyral.

[0009] Preferably, the composite ammonium salt is prepared by mixing ammonium sulfate, ammonium phosphate and ammonium nitrite in a mass ratio of 1.5:2:0.5.

[0010] Preferably, the solvent is one or more of ethylene glycol phenyl ether, propylene glycol monomethyl ether acetate, isophorone, ethylene glycol phenol ether, propylene glycol monomethyl ether, and ethylene glycol monobutyl ether.

[0011] Preferably, the solvent is a mixture of ethylene glycol phenyl ether and propylene glycol monomethyl ether acetate in a mass ratio of 1:1-4.

[0012] Preferably, the diameter of the low-splash lead-free rosin-coated solder wire is 0.5-1.6 mm.

[0013] Preferably, the method for preparing the low-splash lead-free rosin-coated solder wire comprises the following steps:

[0014] (a) Alloy smelting: Sn, Sb, Cu, Ge, P, Ga, In, and Ni alloy elements are weighed according to the ratio, added into a smelting furnace, and smelted at 700-800°C for 1-2h to obtain a uniform alloy liquid;

[0015] (b) Ingot casting: The alloy liquid is cast into rods or strips and rapidly cooled;

[0016] (c) Extrusion molding: The cooled alloy rod or strip material is placed in an extruder, extruded into a wire through an extrusion die, and then cooled to form a solder wire;

[0017] (d) Preparation of soldering flux: According to the soldering flux formula, rosin resin, maleic anhydride, polyoxypropylene glycerol ether, complex ammonium salt, solvent, sodium carboxymethyl cellulose, and polyvinyl butyral soldering flux components are uniformly mixed, and heated at 80-100° C. until completely dissolved to obtain a soldering flux solution;

[0018] (e) Coating with flux: Immerse the cooled solder wire in the flux solution for 10 seconds to 1 minute at a temperature of 50 to 80°C, using a uniform immersion method, including rotary immersion or spray immersion, so that the surface of the solder wire is evenly covered with flux;

[0019] (f) Drying treatment: The solder wire dipped in flux is dried at 80-120°C for 5-30 minutes to form a low-splash lead-free rosin-coated solder wire.

[0020] Preferably, the solder wire is protected by an inert gas during the smelting process, and the inert gas is nitrogen or argon.

[0021] Preferably, the rapid cooling is water cooling or air cooling, and the cooling speed is controlled. Water cooling includes spray cooling and circulating water cooling, and air cooling includes forced air cooling.

[0022] The beneficial effects achieved by the present invention are as follows: 1. The present invention can improve the performance of solder wire while reducing spatter by optimizing the alloy composition and the flux formula. Specifically, by adding antimony (Sb), copper (Cu), germanium (Ge), phosphorus (P), gallium (Ga), indium (In) and nickel (Ni), these elements can improve the fluidity and wettability of the solder wire, making the solder easier to spread during the welding process. The rosin coated on the outside can remove metal surface oxides during the welding process and promote good contact between the solder and the metal surface. The rosin decomposes during the heating process to produce active substances. These active substances can further reduce the surface tension of the solder and improve the fluidity of the solder, thereby significantly reducing the spatter rate, improving the comprehensive performance of the lead-free solder wire, and improving the welding reliability.

[0023] 2. The present invention further improves the wettability of the solder wire by optimizing the flux components, including the composition ratio of rosin resin, maleic anhydride, and polyoxypropylene glycerol ether. These components can effectively remove oxides on the welding surface, promote the fluidity and wettability of the solder, reduce the residual amount of the flux, and make it easier for the solder to form a good connection at the welding point.

[0024] 3. The present invention improves the mechanical strength of the solder wire by adding an appropriate amount of copper (Cu) and other trace elements. Copper can enhance the ductility and tensile strength of the solder wire, thereby forming a more stable welding point during the welding process, and improving the reliability and durability of welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart for preparing the low-splash lead-free rosin-coated solder wire used in the embodiments of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with specific embodiments.

[0027] Embodiment 1: A low-splash lead-free rosin-coated solder wire, the alloy composition of the solder wire and its mass percentage are: Sn 88%, Sb 5%, Cu 1%, Ge 0.012%, P 0.010%, Ga 0.005%, In 0.005%, Ni 0.05%, and the balance is inevitable impurities; the solder wire is made by extrusion molding, and is coated with a flux composed of the following components in mass parts: rosin resin 14 parts, maleic anhydride 2 parts, polyoxypropylene glycerol ether 2 parts, complex ammonium salt 3 parts (ammonium sulfate, ammonium phosphate and ammonium nitrite mass ratio of 1.5:2:0.5), solvent 460 parts (ethylene glycol phenyl ether and propylene glycol monomethyl ether acetate mass ratio of 1:1), sodium carboxymethyl cellulose 13 parts, polyvinyl butyral 25 parts.

[0028] A method for preparing a low-splash lead-free rosin-coated solder wire, such as Figure 1 As shown, the following steps are included:

[0029] (a) Alloy smelting: Sn, Sb, Cu, Ge, P, Ga, In, and Ni alloy elements are weighed according to the ratio, added into a smelting furnace, and smelted at 750°C for 1.5 h. Nitrogen protection is used during the smelting process to obtain a uniform alloy liquid;

[0030] (b) Ingot casting: The alloy liquid is cast into a rod shape and rapidly cooled by water cooling;

[0031] (c) Extrusion molding: The cooled alloy rod is placed in an extruder and extruded into a wire with a diameter of 1.0 mm through an extrusion die. After extrusion, it is air-cooled to form a solder wire.

[0032] (d) Preparation of soldering flux: According to the soldering flux formula, rosin resin, maleic anhydride, polyoxypropylene glycerol ether, complex ammonium salt, solvent, sodium carboxymethyl cellulose, and polyvinyl butyral soldering flux components are uniformly mixed, and heated at 85° C. until completely dissolved to obtain a soldering flux solution;

[0033] (e) External coating with flux: Immerse the cooled solder wire in the flux solution for 30 seconds at a temperature of 60°C, using a rotary dipping method to evenly cover the surface of the solder wire with flux;

[0034] (f) Drying treatment: The solder wire dipped in flux is dried at 100°C for 20 minutes to form a low-splash lead-free rosin-coated solder wire.

[0035] Embodiment 2: A low-splash lead-free rosin-coated solder wire, the alloy composition of the solder wire and its mass percentage are: Sn 90%, Sb 4%, Cu 1%, Ge 0.010%, P 0.012%, Ga 0.006%, In 0.004%, Ni 0.04%, and the balance is inevitable impurities; the solder wire is made by extrusion molding, and is coated with a flux composed of the following components in mass parts: rosin resin 15 parts, maleic anhydride 2 parts, polyoxypropylene glycerol ether 2 parts, complex ammonium salt 3 parts (ammonium sulfate, ammonium phosphate and ammonium nitrite mass ratio of 1.5:2:0.5), solvent 480 parts (ethylene glycol phenyl ether and propylene glycol monomethyl ether acetate mass ratio of 1:2), sodium carboxymethyl cellulose 14 parts, polyvinyl butyral 26 parts.

[0036] A method for preparing a low-splash lead-free rosin-coated solder wire, such as Figure 1 As shown, the following steps are included:

[0037] (a) Alloy smelting: Sn, Sb, Cu, Ge, P, Ga, In, and Ni alloy elements were weighed according to the ratio, added into a smelting furnace, and smelted at 780°C for 1.2 h. Argon gas was used as protection during the smelting process to obtain a uniform alloy liquid;

[0038] (b) Ingot casting: The alloy liquid is cast into bars and rapidly cooled by air cooling;

[0039] (c) Extrusion molding: The cooled strip material is placed in an extruder and extruded into a wire material with a diameter of 0.8 mm through an extrusion die. After extrusion, it is water-cooled to form a solder wire;

[0040] (d) Preparation of flux: According to the flux formula, rosin resin, maleic anhydride, polyoxypropylene glycerol ether, complex ammonium salt, solvent, sodium carboxymethyl cellulose, and polyvinyl butyral flux components are uniformly mixed, and heated at 90° C. until completely dissolved to obtain a flux solution;

[0041] (e) External coating with flux: The cooled solder wire is immersed in the flux solution for 45 seconds at a temperature of 65°C, and a rotary dipping method is used to evenly cover the surface of the solder wire with flux;

[0042] (f) Drying treatment: The solder wire dipped in flux is dried at 110°C for 12 minutes to form a low-splash lead-free rosin-coated solder wire.

[0043] Embodiment 3: A low-splash lead-free rosin-coated solder wire, the alloy composition of the solder wire and its mass percentage are: Sn 86%, Sb 6%, Cu 1%, Ge 0.015%, P 0.010%, Ga 0.005%, In 0.005%, Ni 0.05%, and the balance is inevitable impurities; the solder wire is made by extrusion molding, and is coated with a flux composed of the following components in mass parts: rosin resin 12 parts, maleic anhydride 3 parts, polyoxypropylene glycerol ether 2 parts, complex ammonium salt 2 parts (ammonium sulfate, ammonium phosphate and ammonium nitrite mass ratio of 1.5:2:0.5), solvent 450 parts (ethylene glycol phenyl ether and propylene glycol monomethyl ether acetate mass ratio of 1:1), sodium carboxymethyl cellulose 12 parts, polyvinyl butyral 24 parts.

[0044] A method for preparing a low-splash lead-free rosin-coated solder wire, such as Figure 1 As shown, the following steps are included:

[0045] (a) Alloy smelting: Sn, Sb, Cu, Ge, P, Ga, In, and Ni alloy elements are weighed according to the ratio, added into a smelting furnace, and smelted at 800°C for 1 h. Nitrogen protection is used during the smelting process to obtain a uniform alloy liquid;

[0046] (b) Ingot casting: The alloy liquid is cast into a rod shape and rapidly cooled by spray cooling;

[0047] (c) Extrusion molding: The cooled alloy rod is placed in an extruder and extruded into a wire with a diameter of 1.2 mm through an extrusion die. After extrusion, it is air-cooled to form a solder wire;

[0048] (d) Preparation of flux: According to the flux formula, rosin resin, maleic anhydride, polyoxypropylene glycerol ether, complex ammonium salt, solvent, sodium carboxymethyl cellulose, and polyvinyl butyral flux components are uniformly mixed, and heated at 95° C. until completely dissolved to obtain a flux solution;

[0049] (e) External coating with flux: Immerse the cooled solder wire in the flux solution for 40 seconds at a temperature of 70°C, using a spray dipping method to evenly cover the surface of the solder wire with flux;

[0050] (f) Drying treatment: The solder wire dipped in flux is dried at 120°C for 8 minutes to form a low-splash lead-free rosin-coated solder wire.

[0051] Comparative Example: A conventional lead-free solder wire, the alloy composition and its mass percentage are: Sn 96.5%, Ag 3.0%, Cu 0.5%; the preparation method of the lead-free solder wire comprises the following steps:

[0052] (1) Alloy smelting: Weigh Sn, Ag, and Cu alloy elements according to the ratio, add them into a smelting furnace, and smelt them at 280°C for 1.5 hours to obtain a uniform alloy liquid;

[0053] (2) Ingot casting and cooling: The alloy liquid is cast into a rod shape and quickly cooled by water cooling;

[0054] (3) Extrusion molding and cooling: The cooled alloy rod is placed in an extruder, extruded into a wire with a diameter of 1.0 mm through an extrusion die, and air-cooled.

[0055] Performance test: The solder wires of Examples 1-3 and the comparative example were tested for wettability, spatter resistance, mechanical properties, oxidation resistance, welding reliability, flux residue and welding temperature range;

[0056] 1. Wettability test: According to GB / T 17391 "Solder Test Method", clean the sample plate with alcohol, heat the stainless steel sample plate to 250℃, place solder wire on the sample plate, record the time required for the solder wire to completely wet the surface of the sample plate, repeat the test, take the average value, and the standard wetting time should be less than 3 seconds; take photos of the wetting area, use image analysis software to calculate the wetting area, repeat the test, take the average value, and the standard wetting area should be greater than 95%.

[0057] 2. Anti-splash test: According to GB / T 17391 "Solder Test Method", heat the stainless steel sample plate to 250℃, use a soldering iron to perform a welding test on the sample plate for 5 seconds. During the welding process, use a spatter collection device to collect spatter particles, use a microscope or digital camera to record the number and size of spatter particles, calculate the spatter rate (the proportion of spatter particles to the total amount of solder), repeat the test, and take the average value. The standard spatter rate should be less than 5%.

[0058] 3. Mechanical properties test: Fix the solder wire on a universal material testing machine, stretch the solder wire at a constant speed of 1mm / min until it breaks, record the maximum tensile force, repeat the test, and take the average value. The standard tensile strength should be greater than 10MPa.

[0059] 4. Anti-oxidation test: According to GB / T 17391 "Solder Test Method", put the solder wire into a high-temperature furnace, raise the furnace temperature to 250℃ and keep it warm for 1 hour, take out the solder wire and cool it to room temperature, observe whether there is oxidation on the surface of the solder wire, and record the observation results. The standard is that there is no obvious oxidation on the surface of the solder wire after keeping it warm at 250℃ for 1 hour.

[0060] 5. Welding reliability test: According to GB / T 18358 "Technical Requirements for Welding of Electronic Components", prepare the circuit board, use a soldering iron to solder at the set temperature (250°C) for 5 seconds, use a shear tester to measure the strength of the soldered joint, check the appearance of the soldered joint to ensure that there are no defects such as cracks and voids, repeat the test and take the average value.

[0061] 6. Flux residue test: According to GB / T 2423.26 "Environmental testing for electric and electronic products Part 2: Test method Test Ea and guidance: Cleanliness test", prepare the sample board, use a soldering iron to solder at the set temperature (250°C) for 5 seconds, use an analytical balance to measure the weight change of the solder wire before and after soldering, calculate the flux residue, repeat the test, and take the average value. The standard flux residue should be less than 100ppm.

[0062] 7. Welding temperature range test: According to GB / T 20878 "Classification and Nomenclature of Solder Alloys", use a DSC instrument to measure the melting temperature of the solder wire, determine the welding temperature range based on the melting temperature, use welding equipment to conduct welding tests at different temperatures to determine the optimal welding temperature, repeat the test and take the average value.

[0063] Test results As can be seen from Table 1-Table 3, the low-splash lead-free rosin-coated solder wires of Examples 1-3 all show excellent performance in wettability, spatter resistance, mechanical properties, oxidation resistance and welding reliability. Specifically, the wetting time of Example 1, Example 2 and Example 3 is less than 3 seconds, and the wetting area is more than 95%, indicating that the solder wire has good wetting performance; the spatter rate is less than 5%, showing a low spatter characteristic; the tensile strength is more than 10MPa, indicating that the solder wire has sufficient mechanical strength; the strength of the welded joint is more than 1400N, and there are no defects such as cracks and voids on the surface of the welded joint, indicating that the solder wire has reliable welding performance; the flux residue is less than 100ppm, indicating that the flux residue is well controlled; the melting temperature is between 215-225℃, which is suitable for practical application requirements. In contrast, the comparative examples performed worse than the new solder wire in various performance tests. In summary, the solder wires of Example 1, Example 2 and Example 3 are superior to the comparative examples in all aspects and have better performance in practical applications.

[0064] Table 1 Solder wire wettability and anti-spatter test results

[0065] Test items Wetting time / S Wetted area / % Splash rate / % Example 1 2.2 97.5 3.2 Example 2 2.3 97.0 3.0 Example 3 2.4 96.5 2.8 Comparative Example 2.8 95.0 4.5

[0066] Table 2 Test results of mechanical properties and oxidation resistance of solder wire

[0067] Test items Tensile strength / MPa Oxidation phenomenon Example 1 13.5 none Example 2 13.0 none Example 3 12.5 none Comparative Example 10.5 none

[0068] Table 3 Test results of solder wire welding reliability, flux residue and welding temperature range

[0069] Test items Welding joint strength / N Flux residue / ppm Melting temperature / ℃ Example 1 1700 70 215 Example 2 1650 75 220 Example 3 1600 80 223 Comparative Example 1400 - 218

[0070] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A low-splash lead-free rosin-coated solder wire, characterized in that: The alloy components of the solder wire and their mass percentages are: Sn 85-92%, Sb 3-7%, Cu 0.5-2%, Ge 0.008-0.015%, P 0.006-0.017%, Ga 0.004-0.009%, In 0.003-0.05%, Ni 0.03-0.1%, and the balance is inevitable impurities; the solder wire is made by extrusion molding, and is coated with a flux composed of the following mass parts: rosin resin 12-15 parts, maleic anhydride 2-4 parts, polyoxypropylene glycerol ether 2-3 parts, composite ammonium salt 2-3 parts, solvent 450-500 parts, sodium carboxymethyl cellulose 12-14 parts, polyvinyl butyral 24-28 parts; The composite ammonium salt is prepared by mixing ammonium sulfate, ammonium phosphate and ammonium nitrite in a mass ratio of 1.5:2:0.5; the solvent is one or more of ethylene glycol phenyl ether, propylene glycol monomethyl ether acetate, isophorone, ethylene glycol phenol ether, propylene glycol monomethyl ether and ethylene glycol monobutyl ether.

2. The low-splash lead-free rosin-coated solder wire according to claim 1, characterized in that: The alloy components and their mass percentages are: Sn 88%, Sb 5%, Cu 1%, Ge 0.012%, P 0.010%, Ga 0.005%, In 0.005%, Ni 0.05%, and the remainder is inevitable impurities.

3. The low-splash lead-free rosin-coated solder wire according to claim 1, characterized in that: The soldering flux comprises the following components in parts by mass: 14 parts of rosin resin, 2 parts of maleic anhydride, 2 parts of polyoxypropylene glycerol ether, 3 parts of composite ammonium salt, 460 parts of solvent, 13 parts of sodium carboxymethyl cellulose and 25 parts of polyvinyl butyral.

4. The low-splash lead-free rosin-coated solder wire according to claim 1, characterized in that: The solvent is a mixture of ethylene glycol phenyl ether and propylene glycol monomethyl ether acetate in a mass ratio of 1:1-4.

5. The low-splash lead-free rosin-coated solder wire according to claim 1, characterized in that: The diameter of the low-splash lead-free rosin-coated solder wire is 0.5-1.6 mm.

6. The method for preparing a low-splash lead-free rosin-coated solder wire according to claim 1, characterized in that: The following steps are involved: (a) Alloy smelting: Sn, Sb, Cu, Ge, P, Ga, In, and Ni alloy elements are weighed according to the ratio, added into a smelting furnace, and smelted at 700-800°C for 1-2h to obtain a uniform alloy liquid; (b) Ingot casting: The alloy liquid is cast into rods or strips and rapidly cooled; (c) Extrusion molding: The cooled alloy rod or strip material is placed in an extruder, extruded into a wire through an extrusion die, and then cooled to form a solder wire; (d) Preparation of flux: according to the flux formula, the flux components are mixed uniformly, and heated at 80-100° C. until they are completely dissolved to obtain a flux solution; (e) External coating with flux: Immerse the cooled solder wire in the flux solution for 10 seconds to 1 minute at a temperature of 50 to 80°C, using rotary dipping or spray dipping to evenly cover the surface with flux; (f) Drying treatment: The solder wire dipped in flux is dried at 80-120°C for 5-30 minutes to form a low-splash lead-free rosin-coated solder wire.

7. The method for preparing a low-splash lead-free rosin-coated solder wire according to claim 6, characterized in that: The solder wire is protected by an inert gas during the melting process, and the inert gas is nitrogen or argon.

8. The method for preparing a low-splash lead-free rosin-coated solder wire according to claim 6, characterized in that: The rapid cooling is water cooling or air cooling, water cooling includes spray cooling and circulating water cooling, and air cooling includes forced air cooling.

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