A high-temperature resistant lead-free solder bar and its preparation method

Abstract

The present invention discloses a high-temperature resistant lead-free solder bar and a preparation method thereof. The high-temperature resistant lead-free solder bar comprises a tin alloy and a soldering flux. The soldering flux comprises raw materials in the following mass percentages: 5-10% of an amphoteric polymer surfactant and 6-11% of a thixotropic agent. The amphoteric polymer surfactant in the soldering flux of the present invention enables the weld seam to have no defects such as local lack of penetration, lack of fusion, cracks, etc., improves the tensile strength and elongation rate of the high-temperature resistant lead-free solder bar, and improves the temperature resistance of the high-temperature resistant lead-free solder.

Description

Technical Field

[0001] The present invention belongs to the field of solder bars, and particularly relates to a high-temperature resistant lead-free solder bar and a preparation method thereof. Background Art

[0002] The solder bar consists of two parts: a tin alloy and a soldering flux. In actual welding engineering applications, the surface of the metal material to be welded is easily oxidized by the atmosphere, forming an unevenly thick oxide film on the surface of the metal material. The presence of the oxide film hinders the flow of the molten tin alloy on the surface of the solder pad, resulting in the occurrence of dry joints, and causing defects such as local incomplete penetration, lack of fusion, and cracks in the weld seam. The formed solder joints are not aesthetically pleasing, and further lead to a decline in the mechanical properties and temperature resistance of the solder bar. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a high-temperature resistant lead-free solder bar, which includes a tin alloy and a soldering flux. The amphoteric polymer surfactant in the soldering flux enables the weld seam to have no defects such as local incomplete penetration, lack of fusion, and cracks, improves the tensile strength and elongation rate of the high-temperature resistant lead-free solder bar, and improves the temperature resistance of the high-temperature resistant lead-free solder.

[0004] The purpose of the present invention is to provide a high-temperature resistant lead-free solder bar, including a tin alloy and a soldering flux. The soldering flux includes raw materials in the following mass percentages: 5-10% of an amphoteric polymer surfactant and 6-11% of a thixotropic agent.

[0005] Preferably, the tin alloy is a tin-silver-copper alloy.

[0006] Preferably, the tin-silver-copper alloy includes raw materials in the following mass percentages: 90-95% tin, 0.5-2% silver, and 3-9.5% copper.

[0007] Preferably, the structure of the amphoteric polymer surfactant is as follows:

[0008]

[0009] Wherein, m, n, and o are positive integers.

[0010] Preferably, the mass ratio of the tin alloy to the soldering flux is 90-95:5-10.

[0011] Preferably, the thixotropic agent includes at least one of ethylene bisstearamide, polyamide-modified hydrogenated castor oil, nano-sized diatomaceous earth, polyamide wax, hydroxyl silicone oil, fumed silica, and hydrogenated castor oil.

[0012] Preferably, the soldering flux further includes 30-45% of rosin, 1-5% of an antioxidant, and the balance of a solvent.

[0013] Preferably, the antioxidant includes at least one of 2-mercaptobenzimidazole, 2,6-di-tert-butyl-4-methylphenol, 1-vinylimidazole, 2-methylimidazole, benzotriazole, methylbenzotriazole, and phenylimidazole.

[0014] Preferably, the solvent includes at least one of ethyl octylene glycol, ethyl hexylene glycol, methyl pentylene glycol, tetraethylene glycol dimethyl ether, and diethylene glycol dimethyl monohexyl ether.

[0015] Another object of the present invention is to provide a method for preparing the high-temperature resistant lead-free solder bar, which includes the following steps:

[0016] Mix tin powder, copper powder, and silver powder, heat and melt them, add a flux, and stir; remove the impurities floating on the molten surface, cast and mold, and cool cyclically to obtain the high-temperature resistant lead-free solder bar.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The high-temperature resistant lead-free solder bar of the present invention includes a tin alloy and a flux. The flux contains an amphoteric polymer surfactant. The molecular structure of the amphoteric polymer surfactant contains a polar carboxyl group, a long side chain, and anions and cations; the polar carboxyl group can effectively remove the oxide film and other impurities on the surface during the welding process, making the weld metal flow better after melting; the long side chain is intertwined with various substances, enhancing the binding force between various substances; the anions and cations enhance the intermolecular force of the amphoteric polymer surfactant; so that there are no defects such as local incomplete penetration, lack of fusion, and cracks in the weld, improving the tensile strength and elongation of the high-temperature resistant lead-free solder bar, and improving the temperature resistance of the high-temperature resistant lead-free solder.

[0019] (2) The ethylene bisstearamide of the present invention contains an imide group and a long-chain structure, and has hydrogen bonding and intertwining interactions with the amphoteric polymer surfactant, further making there no defects such as local incomplete penetration, lack of fusion, and cracks in the weld, improving the tensile strength and elongation of the high-temperature resistant lead-free solder bar, and further improving the temperature resistance of the high-temperature resistant lead-free solder. Detailed Embodiments

[0020] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] Example 1: Preparation of an amphoteric polymer surfactant.

[0022] 1-Dodecyl-3-vinylimidazolium bromide, acrylic acid and dimethylaminoethyl methacrylate were added to a reaction vessel in a molar ratio of 1:2:3 along with the solvent ethanol. Under the action of an azobisisobutyronitrile initiator accounting for 0.8% of the total mass of the reactants, the above reaction system was refluxed at 71 °C for 7 h. Then, the solvent ethanol was removed. Subsequently, the crude product was dialyzed in ethanol and water (1:3) for 48 h to remove the unreacted 1-dodecyl-3-vinylimidazolium bromide, acrylic acid and dimethylaminoethyl methacrylate, and then freeze-dried to obtain the amphoteric polymer surfactant; the structure of the amphoteric polymer surfactant is as follows:

[0023]

[0024] Among them, m, n, and o are positive integers.

[0025] Example 2: Preparation of a high-temperature resistant lead-free solder bar.

[0026] By mass percentage, the raw materials of 95% tin-silver-copper alloy were mixed, heated and melted, 5% of a soldering flux was added, and stirred for 20 min; the impurities floating on the molten surface were removed, poured into a mold, and cooled cyclically to obtain the high-temperature resistant lead-free solder bar;

[0027] The tin-silver-copper alloy includes the following raw materials by mass percentage: 90% tin, 0.5% silver, 9.5% copper;

[0028] The soldering flux includes the following raw materials by mass percentage: 10% of the amphoteric polymer surfactant prepared in Example 1, 11% of a thixotropic agent, 30% of rosin, 5% of an antioxidant, and the balance of a solvent;

[0029] The thixotropic agent is selected from ethylene bisstearamide;

[0030] The antioxidant is selected from 2-mercaptobenzimidazole;

[0031] The solvent is selected from ethyl octanediol.

[0032] Example 3: Preparation of a high-temperature resistant lead-free solder bar.

[0033] By mass percentage, the raw materials of 90% tin-silver-copper alloy were mixed, heated and melted, 10% of a soldering flux was added, and stirred for 20 min; the impurities floating on the molten surface were removed, poured into a mold, and cooled cyclically to obtain the high-temperature resistant lead-free solder bar;

[0034] The tin-silver-copper alloy includes the following raw materials by mass percentage: 95% tin, 2% silver, 3% copper;

[0035] The soldering flux comprises raw materials in the following mass percentages: 5% of the amphoteric polymer surfactant prepared in Example 1, 6% of a thixotropic agent, 45% of rosin, 1% of an antioxidant, and the balance of a solvent;

[0036] The thixotropic agent is selected from ethylene bisstearamide;

[0037] The antioxidant is selected from 2-mercaptobenzimidazole;

[0038] The solvent is selected from ethyl octanediol.

[0039] Example 4: Preparation of a high-temperature lead-free solder bar.

[0040] By mass percentage, the raw materials of 92% tin-silver-copper alloy are mixed, heated and melted, 8% of the soldering flux is added, and stirring is carried out for 20 min; the impurities floating on the molten surface are removed, casting is carried out, and cyclic cooling is carried out to obtain the high-temperature lead-free solder bar;

[0041] The tin-silver-copper alloy comprises raw materials in the following mass percentages: 92% of tin, 1% of silver, and 7% of copper;

[0042] The soldering flux comprises raw materials in the following mass percentages: 8% of the amphoteric polymer surfactant prepared in Example 1, 9% of a thixotropic agent, 40% of rosin, 3% of an antioxidant, and the balance of a solvent;

[0043] The thixotropic agent is selected from ethylene bisstearamide;

[0044] The antioxidant is selected from 2-mercaptobenzimidazole;

[0045] The solvent is selected from ethyl octanediol.

[0046] Example 5: Preparation of a high-temperature lead-free solder bar.

[0047] By mass percentage, the raw materials of 92% tin-silver-copper alloy are mixed, heated and melted, 8% of the soldering flux is added, and stirring is carried out for 20 min; the impurities floating on the molten surface are removed, casting is carried out, and cyclic cooling is carried out to obtain the high-temperature lead-free solder bar;

[0048] The tin-silver-copper alloy comprises raw materials in the following mass percentages: 92% of tin, 1% of silver, and 7% of copper;

[0049] The soldering flux comprises raw materials in the following mass percentages: 8% of the amphoteric polymer surfactant prepared in Example 1, 9% of a thixotropic agent, 40% of rosin, 3% of an antioxidant, and the balance of a solvent;

[0050] The thixotropic agent is selected from hydroxy silicone oil;

[0051] The antioxidant is selected from 2-mercaptobenzimidazole;

[0052] The solvent is selected from ethyl octanediol.

[0053] Performance tests were carried out on the high-temperature resistant lead-free solder bars of Examples 2 to 5.

[0054] Tensile strength and elongation test: The high-temperature resistant lead-free solder bars prepared in Examples 2 to 5 were subjected to tensile strength and elongation tests. The test instrument was a Shimadzu precision electronic materials universal testing machine (CMT4305), the tensile speed was 0.5 mm / s, the high-temperature resistant lead-free solder bar was 1.0 mm thick, 3.2 mm wide, the parallel length was 10 mm, the gauge length was 5 mm, and the strain rate was 10 -3 s -1 , and each sample was tested 5 times, and the average value was taken. The results are shown in Table 1.

[0055] Table 1. Performance test results.

[0056]

[0057] As can be seen from Table 1, the high-temperature resistant lead-free solder bars prepared in Examples 2 to 5 of the present invention have high tensile strength and elongation. It can be seen that the soldering flux of the present invention contains an amphoteric polymer surfactant, and the molecular structure of the amphoteric polymer surfactant contains a polar carboxyl group, a long side chain, and cations and anions; the polar carboxyl group can effectively remove the oxide film agent and other impurities on the surface during the welding process, making the weld metal flow well after melting; the long side chain is intertwined with various substances, enhancing the binding force between various substances; the cations and anions enhance the intermolecular force of the amphoteric polymer surfactant; so that there are no defects such as local lack of penetration, lack of fusion, and cracks in the weld, improving the tensile strength and elongation of the high-temperature resistant lead-free solder bar, and improving the temperature resistance of the high-temperature resistant lead-free solder.

[0058] The ethylene bisstearamide of the present invention contains an imide group and a long-chain structure, and has a hydrogen bond and an intertwining interaction with the amphoteric polymer surfactant, further making there be no defects such as local lack of penetration, lack of fusion, and cracks in the weld, improving the tensile strength and elongation of the high-temperature resistant lead-free solder bar, and further improving the temperature resistance of the high-temperature resistant lead-free solder.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that after reading the specification of this application, the specific implementation manners of the present invention can still be modified or equivalently replaced, but these modifications or changes do not depart from the protection scope of the pending claims of the present invention application.

Claims

1. A high-temperature resistant lead-free solder bar, characterized in that, It includes a tin alloy and a soldering flux. The soldering flux is composed of raw materials in the following mass percentages: 5-10% of an amphoteric polymer surfactant, 6-11% of a thixotropic agent, 30-45% of rosin, 1-5% of an antioxidant, and the balance of a solvent; the mass ratio of the tin alloy to the soldering flux is 90-95:5-10; The structure of the amphoteric polymer surfactant is as follows: wherein, m, n, and o are positive integers.

2. The high-temperature resistant lead-free solder bar according to claim 1, wherein The tin alloy is a tin-silver-copper alloy.

3. The high-temperature resistant lead-free solder bar according to claim 2, wherein, The tin-silver-copper alloy includes raw materials in the following mass percentages: 90-95% of tin, 0.5-2% of silver, and 3-9.5% of copper.

4. The high-temperature resistant lead-free solder bar according to claim 1, wherein The thixotropic agent includes at least one of ethylene bisstearamide, polyamide-modified hydrogenated castor oil, nano-sized diatomaceous earth, polyamide wax, hydroxy silicone oil, fumed silica, and hydrogenated castor oil.

5. The high-temperature resistant lead-free solder bar according to claim 1, wherein The antioxidant includes at least one of 2-mercaptobenzimidazole, 2,6-di-tert-butyl-4-methylphenol, 1-vinylimidazole, 2-methylimidazole, benzotriazole, methylbenzotriazole, and phenylimidazole.

6. The high-temperature resistant lead-free solder bar according to claim 1, wherein, The solvent includes at least one of ethyl octylene glycol, ethyl hexylene glycol, methyl pentylene glycol, tetraethylene glycol dimethyl ether, and diethylene glycol dimethyl monohexyl ether.

7. The preparation method of the high-temperature resistant lead-free solder bar according to any one of claims 1 to 6, characterized in that, It includes the following steps: Mix tin powder, copper powder, and silver powder, heat and melt them, add the soldering flux, and stir; remove the impurities floating on the molten surface, pour and mold, and cool cyclically to obtain the high-temperature resistant lead-free solder bar.

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