Preparation process of lead-free solder wire

Abstract

This invention belongs to the field of lead-free solder wire processing technology, specifically relating to a preparation process of lead-free solder wire, including the following steps: S1, aluminum, copper, silver, and tin are placed in a crucible and placed in a vacuum furnace. The vacuum furnace is evacuated, filled with an inert protective gas, and heated until completely melted to obtain a molten mixed metal liquid; the mass ratio of aluminum, copper, silver, and tin is (2-4):(7-9):(1-2):(85-90); S2, under an inert protective gas atmosphere, an antioxidant is added to the molten mixed metal liquid, stirred evenly, poured, extruded, and drawn into wire to obtain a preliminary product; S3, the preliminary product is immersed in flux until the flux fully adheres to the surface of the preliminary product, the preliminary product is removed, dried, wound, and packaged to obtain lead-free solder wire. The lead-free solder wire prepared in this application is not easily oxidized, resulting in a high yield rate of soldered components.

Description

Technical Field

[0001] This invention belongs to the field of lead-free solder wire processing technology, specifically relating to a preparation process for lead-free solder wire. Background Technology

[0002] With societal development and increasing environmental awareness, the research and application of solder wire both domestically and internationally have embarked on a green and environmentally friendly development path. Lead-free solder wire has become a hot topic in the market. Lead-free solder wire boasts excellent wettability, conductivity, and thermal conductivity; it is easy to tin, prevents soldering spatter, ensures uniform flux distribution, eliminates flux breaks in the solder core, provides uniform and knot-free winding, and offers fast tinning speed and minimal residue. These advantages ensure the post-soldering reliability of electronic and electrical products and components.

[0003] The traditional manufacturing process of lead-free solder wire mainly involves steps such as melting, casting, extrusion, wire drawing, winding, and packaging. During the production of traditional lead-free solder wire, the alloy solution is prone to producing oxides, which not only affects the fluidity of the liquid solder but may also contaminate the PCBA board surface, directly affecting the soldering quality and reliability of the product. This results in a relatively low yield rate of lead-free solder wire and causes a huge waste of alloy solder. Summary of the Invention

[0004] In order to improve the defect that the alloy solution is prone to oxide formation during the production of lead-free solder wire, this application provides a preparation process for lead-free solder wire.

[0005] Firstly, this application provides a process for preparing lead-free solder wire, which is achieved using the following technical solution:

[0006] A process for preparing lead-free solder wire includes the following steps:

[0007] S1. Aluminum, copper, silver and tin are put into a crucible and placed in a vacuum furnace. The vacuum furnace is evacuated and filled with an inert protective gas. The vacuum furnace is heated until it is completely melted to obtain a molten mixed metal liquid. The mass ratio of aluminum, copper, silver and tin is (2-4):(7-9):(1-2):(85-90).

[0008] S2. Under an inert protective gas atmosphere, an antioxidant is added to the molten mixed metal liquid described in step S1, stirred evenly, poured, extruded, and drawn into wire to obtain the initial product.

[0009] S3. Immerse the initial product described in step S2 in flux until the flux fully adheres to the surface of the initial product. Remove the initial product, dry it, wind it, and package it to obtain lead-free solder wire.

[0010] By adopting the above technical solutions, the metal alloy composition of lead-free solder wire contains aluminum, copper, silver, and tin. Aluminum is the most reactive element, and its addition makes copper, silver, and tin less susceptible to oxidation during the melting process and in the molten state, increasing the number of bright solder joints. The inert protective gas prevents the alloy solution from generating oxides, and the addition of antioxidants prevents the molten mixed metal liquid from being oxidized during casting, extrusion, and wire drawing, improving the quality of the initial product. This, in turn, improves the quality of components soldered by lead-free solder wire, resulting in a higher number of bright solder joints, fewer open solder joints and bridging solder joints, and a higher yield rate.

[0011] Preferably, the mass ratio of the antioxidant to the molten mixed metal liquid is (1-2):100.

[0012] Preferably, the antioxidant is a mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tert-butylhydroquinone in a mass ratio of (2-3):1.

[0013] By adopting the above technical solution, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tert-butylhydroquinone have a synergistic effect, which significantly improves the antioxidant properties and makes them less susceptible to decomposition and destruction. This increases the number of bright solder joints and reduces the number of open solder joints and bridging solder joints.

[0014] Preferably, the raw materials for preparing the flux, by weight, include 10-12 parts of o-iodobenzoic acid, 2-4 parts of flux activator, 30-40 parts of film-forming agent, 0.6-0.8 parts of surfactant, and 60-80 parts of rosin co-modified with fumaric acid and acrylic acid.

[0015] By adopting the above technical solutions, o-iodobenzoic acid can remove oxides from the surface of solder and substrate. The rosin modified by fumaric acid and acrylic acid can not only remove oxides from the metal surface and increase the fluidity of the solder, but also improve the spreadability and wettability of the solder and improve the strength of the solder joint. This improves the quality of components soldered by lead-free solder wire, resulting in more bright solder joints and fewer open solder joints and bridging solder joints.

[0016] Preferably, the raw materials for preparing the rosin co-modified with fumaric acid and acrylic acid include rosin, acrylic acid, fumaric acid, and a composite antioxidant; the mass ratio of rosin, acrylic acid, fumaric acid, and composite antioxidant is (80-100):(4-7):(1-3):(0.3-0.5).

[0017] By adopting the above technical solution, the addition of composite antioxidants improves the antioxidant capacity of rosin, further removes oxides from the metal surface, increases the number of bright solder joints, and reduces the number of open solder joints and bridging solder joints.

[0018] Preferably, the composite antioxidant is composed of tea polyphenols, tert-butyl-4-hydroxyanisole and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] in a mass ratio of (2-3):(1.5-2.5):(0.5-1).

[0019] By adopting the above technical solution, tea polyphenols contain four catechins with different structures, flavanols, and small amounts of phenolic acids and flavonols. All of them have multiple phenolic hydroxyl groups in their molecules. The combination of tea polyphenols, tert-butyl-4-hydroxyanisole, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] has an antioxidant synergistic effect, improves the firmness and reliability of solder joints, thereby improving the quality of soldered components, resulting in a high yield rate, a large number of bright solder joints, and a small number of open solder joints and bridging solder joints.

[0020] Preferably, the rosin is polymerized rosin.

[0021] By adopting the above technical solution, the polymerized rosin has a high softening point, good oxidation resistance, and increased solder fluidity, thereby improving the quality and reliability of welding, resulting in a higher yield, more bright solder joints, and fewer open and bridging solder joints.

[0022] In this application, the flux activator is selected from one or more of oxalic acid, succinic acid, adipic acid, and gallic acid; preferably, the flux activator is gallic acid.

[0023] Gallic acid contains active phenolic hydroxyl and carboxyl groups, which enhances the activity of the flux and helps the solder wet the components and the metal being soldered, thereby removing the oxide layer on the surface of the components and the metal being soldered.

[0024] In this application, the film-forming agent is polyethylene glycol and / or sorbitol; preferably, the film-forming agent is sorbitol.

[0025] Sorbitol contains a large number of hydroxyl groups, which gives it excellent film-forming properties and can effectively protect the solder and base metal from oxidation during the welding process.

[0026] Preferably, in step S1, the temperature of the heat treatment is 750-850℃.

[0027] Preferably, the inert protective gas is one or a mixture of several of helium, neon, and argon.

[0028] Preferably, in step S3, the initial product is immersed in the flux for 3-4 hours.

[0029] In summary, this application has the following beneficial effects:

[0030] 1. This application uses an inert protective gas to prevent the alloy solution from generating oxides, uses an antioxidant to prevent the molten mixed metal liquid from being oxidized during casting, extrusion, and wire drawing, and adds aluminum to prevent copper, silver, and tin from being oxidized during melting and in the molten state. This increases the number of bright solder joints, reduces the number of open solder joints and bridging solder joints, and improves the quality of components soldered by lead-free solder wire.

[0031] 2. This application uses pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tert-butylhydroquinone in combination, which has a synergistic effect, significantly improves the antioxidant properties, and is not easily decomposed and destroyed, thereby increasing the number of bright solder joints and reducing the number of open solder joints and bridging solder joints.

[0032] 3. This application uses fumaric acid and acrylic acid to modify rosin, which can not only remove oxides on the metal surface and increase the fluidity of the solder, but also improve the spreadability and wettability of the solder, and improve the strength of the solder joint, thereby improving the quality of components soldered by lead-free solder wire, with more bright solder joints and fewer open solder joints and bridging solder joints. Detailed Implementation

[0033] The present application will be further described in detail below with reference to the embodiments.

[0034] Preparation Example

[0035] Preparation Example 1 provides a rosin co-modified with fumaric acid and acrylic acid, the preparation steps of which are as follows:

[0036] 80 kg of rosin was added to a reaction vessel and heated to 180 °C under nitrogen protection to dissolve the rosin. 1 kg of fumaric acid was added while stirring, and the temperature was raised to 200 °C and reacted at 200 °C for 2 hours. Then 4 kg of acrylic acid was added, and the temperature was raised to 230 °C and reacted at 230 °C for 2 hours. The temperature was lowered to 210 °C, and 0.3 kg of composite antioxidant was added. The mixture was stirred evenly, cooled, and discharged to obtain rosin co-modified with fumaric acid and acrylic acid.

[0037] Among them, the rosin is Arakawa KE-100 rosin from Japan;

[0038] The compound antioxidant is a mixture of tea polyphenols, tert-butyl-4-hydroxyanisole, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], with a mass ratio of 2:1.5:0.5.

[0039] Preparation Examples 2-3 provide a rosin co-modified with fumaric acid and acrylic acid, which differs from Preparation Example 1 only in that the quality of the raw materials for preparing the co-modified rosin with fumaric acid and acrylic acid is different, as shown in Table 1.

[0040] Table 1. Mass of raw materials for the preparation of rosin co-modified with fumaric acid and acrylic acid in Examples 1-3 (kg)

[0041]

[0042] Preparation Example 4 provides a rosin co-modified with fumaric acid and acrylic acid, which differs from Preparation Example 3 only in that the mass ratio of tea polyphenols, tert-butyl-4-hydroxyanisole and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] is 3:2.5:1.

[0043] Preparation Example 5 provides a rosin co-modified with fumaric acid and acrylic acid, which differs from Preparation Example 4 only in that the rosin is POLY PALE polymerized rosin (purchased from Jining Tangyi Chemical Co., Ltd.).

[0044] Preparation Example 6 provides a rosin co-modified with fumaric acid and acrylic acid, which differs from Preparation Example 1 only in that the composite antioxidant is a mixture of tea polyphenols and tert-butyl-4-hydroxyanisole, with a mass ratio of tea polyphenols to tert-butyl-4-hydroxyanisole of 2:2.

[0045] Preparation Example 7 provides a rosin co-modified with fumaric acid and acrylic acid, which differs from Preparation Example 1 only in that the composite antioxidant is a mixture of tea polyphenols and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], with a mass ratio of tea polyphenols to pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] in 2:2.

[0046] Preparation Example 8 provides a rosin co-modified with fumaric acid and acrylic acid, which differs from Preparation Example 1 only in that the composite antioxidant is a mixture of tert-butyl-4-hydroxyanisole and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], with a mass ratio of 1.5:2.5 between tert-butyl-4-hydroxyanisole and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0047] Preparation Example 9 provides a flux, the preparation steps of which are as follows:

[0048] 60 kg of rosin modified with fumaric acid and acrylic acid was heated to 120°C until completely melted. Then, 10 kg of o-iodobenzoic acid, 2 kg of gallic acid, 30 kg of sorbitol and 0.6 kg of surfactant were added. The mixture was stirred at 120°C until completely dissolved and cooled to obtain flux.

[0049] The rosin co-modified with fumaric acid and acrylic acid was derived from Preparation Example 1;

[0050] The surfactant is a mixture of OP-10 and Tween-80, with a mass ratio of OP-10 to Tween-80 of 1:1.

[0051] Preparation Examples 10-16 provide a flux that differs from Preparation Example 9 only in that the source of the rosin co-modified with fumaric acid and acrylic acid is different, as detailed in Table 2.

[0052] Table 2. Sources of rosin co-modified with fumaric acid and acrylic acid in Examples 9-16.

[0053]

[0054] Preparation Examples 17-18 provide a flux that differs from Preparation Example 13 only in the quality of the raw materials used in the preparation of the flux, as detailed in Table 3.

[0055] Table 3 Mass of raw materials for flux preparation in Examples 13 and 17-18 (kg)

[0056]

[0057] Preparation of comparative examples

[0058] Comparative Example 1 provides a flux that differs from Preparation Example 16 only in that the rosin co-modified with fumaric acid and acrylic acid is replaced by Arakawa KE-100 rosin from Japan.

[0059] Example

[0060] Example 1 provides a process for preparing lead-free solder wire, the steps of which are as follows:

[0061] S1. Put 0.2 kg of aluminum, 0.7 kg of copper, 0.1 kg of silver and 8.5 kg of tin into a crucible, place it in a vacuum furnace, evacuate the vacuum furnace, fill it with argon gas, and heat the vacuum furnace to 750°C until the metal is completely melted to obtain a molten mixed metal liquid.

[0062] S2. Under an argon atmosphere, 95g of tert-butylhydroquinone is added to the molten mixed metal liquid described in step S1. After stirring evenly, it is poured into a mold, cast, extruded, and drawn into wire to obtain the initial product.

[0063] S3. Immerse the initial product described in step S2 in 60 kg of flux (from the preparation of comparative example 1) for 3 hours until the flux adheres to the surface of the initial product. Take out the initial product, dry it, wind it, and package it to obtain lead-free solder wire.

[0064] Example 2 provides a process for preparing lead-free solder wire, the steps of which are as follows:

[0065] S1. Put 0.4 kg of aluminum, 0.9 kg of copper, 0.2 kg of silver and 9 kg of tin into a crucible, place it in a vacuum furnace, evacuate the vacuum furnace, fill it with argon gas, and heat the vacuum furnace to 850°C until the metal is completely melted to obtain a molten mixed metal liquid.

[0066] S2. Under an argon atmosphere, 105g of tert-butylhydroquinone was added to the molten mixed metal liquid described in step S1. After stirring evenly, the mixture was poured into a mold, cast, extruded, and drawn into wire to obtain the initial product.

[0067] S3. Immerse the initial product described in step S2 in 60 kg of flux (derived from the preparation of Comparative Example 1) for 4 hours until the flux adheres to the surface of the initial product. Remove the initial product, dry it, wind it, and package it to obtain lead-free solder wire.

[0068] Example 3 provides a process for preparing lead-free solder wire, which differs from Example 2 only in that the mass of tert-butylhydroquinone is 210g.

[0069] Example 4 provides a process for preparing lead-free solder wire, which differs from Example 3 only in that tert-butylhydroquinone is replaced by pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0070] Example 5 provides a process for preparing lead-free solder wire, which differs from Example 3 only in that: tert-butylhydroquinone is replaced by a mixture of tert-butylhydroquinone and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], with the mass ratio of tert-butylhydroquinone to pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] being 1:2.

[0071] Example 6 provides a process for preparing lead-free solder wire, which differs from Example 5 only in that the mass ratio of tert-butylhydroquinone and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 1:3.

[0072] Examples 7-16 provide a process for preparing lead-free solder wire, which differs from Example 6 only in that the source of flux is different, see 4 for details.

[0073] Table 4. Flux Sources in Examples 6-16

[0074] Group Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Flux source Preparation of Comparative Example 1 Preparation Example 9 Preparation Example 10 Preparation Example 11 Preparation Example 12 Preparation Example 13 Group Example 12 Example 13 Example 14 Example 15 Example 16 / Flux source Preparation Example 14 Preparation Example 15 Preparation Example 16 Preparation Example 17 Preparation Example 18 /

[0075] Comparative Example

[0076] Comparative Example 1 provides a process for preparing lead-free solder wire, the steps of which are as follows:

[0077] S1. Put 0.2 kg of aluminum, 0.7 kg of copper, 0.1 kg of silver and 8.5 kg of tin into a crucible, place it in a vacuum furnace, and heat the vacuum furnace to 750°C until the metal is completely melted to obtain a molten mixed metal liquid.

[0078] S2. Add 95g of tert-butylhydroquinone to the molten metal mixture described in step S1, stir evenly, pour into a mold, cast, extrude, and draw into wire to obtain the initial product.

[0079] S3. Immerse the initial product described in step S2 in 60 kg of flux (from the preparation of comparative example 1) for 3 hours until the flux adheres to the surface of the initial product. Take out the initial product, dry it, wind it, and package it to obtain lead-free solder wire.

[0080] Comparative Example 2 provides a process for preparing lead-free solder wire, the steps of which are as follows:

[0081] S1. Put 0.7 kg of copper, 0.1 kg of silver and 8.5 kg of tin into a crucible, place it in a vacuum furnace, and heat the vacuum furnace to 750°C until the metal is completely melted to obtain a molten mixed metal liquid.

[0082] S2. Add 95g of tert-butylhydroquinone to the molten metal mixture described in step S1, stir evenly, pour into a mold, cast, extrude, and draw into wire to obtain the initial product.

[0083] S3. Immerse the initial product described in step S2 in 60 kg of flux (from the preparation of comparative example 1) for 3 hours until the flux adheres to the surface of the initial product. Take out the initial product, dry it, wind it, and package it to obtain lead-free solder wire.

[0084] Performance testing

[0085] The following performance tests were conducted on the lead-free solder wires prepared in Examples 1-16 and Comparative Examples 1-2 of this application.

[0086] Using an automatic soldering machine and an HST-9 constant temperature and humidity chamber (purchased from Shanghai Shiteng Electric Co., Ltd.), 100 points of lead-free solder wire prepared in Examples 1-16 and Comparative Examples 1-2 were soldered on the components at 400℃ according to JIS Z3197 standard. The number of bright solder points and the number of solder points without open circuits and bridging were counted. The test results are shown in Table 5.

[0087] Table 5 Test Results

[0088]

[0089]

[0090] The following section details this application based on the test data in Table 5.

[0091] The test data from Example 1 and Comparative Examples 1-2 show that the inert protective gas makes it less likely for the alloy solution to produce oxides, and the addition of aluminum makes it less likely for copper, silver and tin to be oxidized during the melting process, which significantly increases the number of bright solder joints, while also reducing the number of open solder joints and bridging solder joints to some extent.

[0092] Test data from Examples 5-6 and Examples 3-4 show that the combination of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tert-butylhydroquinone has a synergistic effect, significantly improving antioxidant properties and making it less susceptible to decomposition and destruction. This increases the number of bright solder joints and reduces the number of open and bridging solder joints.

[0093] The test data from Examples 6 and 7 show that the co-modification of rosin with fumaric acid and acrylic acid improves the quality of components soldered by lead-free solder wire, resulting in more bright solder joints and fewer open solder joints and bridging solder joints.

[0094] The test data from Examples 10 and 11 show that polymerized rosin improves the quality and reliability of welding, resulting in a higher yield, more bright solder joints, and fewer open and bridging solder joints.

[0095] Test data from Examples 7 and 12-14 show that the combination of tea polyphenols, tert-butyl-4-hydroxyanisole, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] has an antioxidant synergistic effect, improves the firmness and reliability of solder joints, thereby improving the quality of soldered components, resulting in a high yield, a large number of bright solder joints, and a small number of open solder joints and bridging solder joints.

[0096] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A process for preparing lead-free solder wire, characterized in that, Includes the following steps: S1. Aluminum, copper, silver and tin are put into a crucible and placed in a vacuum furnace. The vacuum furnace is evacuated and filled with an inert protective gas. The vacuum furnace is heated until it is completely melted to obtain a molten mixed metal liquid. The mass ratio of aluminum, copper, silver and tin is (2-4):(7-9):(1-2):(85-90). S2. Under an inert protective gas atmosphere, an antioxidant is added to the molten mixed metal liquid described in step S1, stirred evenly, poured, extruded, and drawn into wire to obtain a preliminary product. The antioxidant is composed of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tert-butylhydroquinone in a mass ratio of (2-3):

1. S3. Immerse the initial product described in step S2 in flux until the flux fully adheres to the surface of the initial product. Remove the initial product, dry it, wind it, and package it to obtain lead-free solder wire. The raw materials for preparing the flux include 10-12 parts of o-iodobenzoic acid, 2-4 parts of flux activator, 30-40 parts of film-forming agent, 0.6-0.8 parts of surfactant, and 60-80 parts of rosin co-modified with fumaric acid and acrylic acid. The raw materials for preparing the rosin co-modified with fumaric acid and acrylic acid include polymerized rosin, acrylic acid, fumaric acid, and a composite antioxidant. The composite antioxidant is composed of tea polyphenols, tert-butyl-4-hydroxyanisole, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] in a mass ratio of (2-3):(1.5-2.5):(0.5-1).

2. The preparation process of lead-free solder wire according to claim 1, characterized in that, The mass ratio of the antioxidant to the molten mixed metal liquid is (1-2):

100.

3. The preparation process of lead-free solder wire according to claim 1, characterized in that, The mass ratio of the polymerized rosin, acrylic acid, fumaric acid, and composite antioxidant is (80-100):(4-7):(1-3):(0.3-0.5).

4. The preparation process of lead-free solder wire according to claim 1, characterized in that, In step S1, the temperature of the heat treatment is 750-850℃.

5. The preparation process of lead-free solder wire according to claim 1, characterized in that, The inert protective gas is one or a mixture of several of helium, neon, and argon.

6. The preparation process of lead-free solder wire according to claim 1, characterized in that, In step S3, the initial product is immersed in flux for 3-4 hours.

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