Lead-free halogen-free solder paste and preparation method thereof

Abstract

The invention discloses a lead-free halogen-free solder paste and a preparation method thereof, the lead-free halogen-free solder paste comprises the following materials in percentage by weight: 86%-90% of solder powder and 10%-14% of soldering flux, the solder powder is tin-bismuth-silver alloy powder, and the soldering flux is composed of the following materials in percentage by weight: 30%-35% of a film-forming agent, 40%-46% of a solvent, 6%-8% of an active agent, 5%-8% of a thixotropic agent, 3%-5% of a corrosion inhibitor and 10% of thermosetting resin. The lead component in the lead-free halogen-free solder paste is replaced by silver and bismuth, and the halogen active agent is replaced by halogen-free organic acid. The corrosion inhibitor can effectively prevent organic acid in the active agent from making contact with solder powder and alloy powder, and corrosion of acid to the alloy powder is slowed down; and 2, the thixotropic agent is prepared from modified hydrogenated castor oil and fatty acid amide wax 6500 according to the optimal mass ratio, so that the thermal collapse resistance of the soldering paste can be greatly improved.

Description

Technical Field

[0001] This invention relates to the field of electronic soldering technology, and in particular to a lead-free and halogen-free solder paste and its preparation method. Background Technology

[0002] Solder paste, a gray paste made from a mixture of solder powder and flux, is a product that emerged with the advent of SMT (Surface Mount Technology). With industry development, solder paste is now primarily used for LED soldering, soldering between PCB boards and various components, and is widely applied in surface mount technology. The quality of the solder paste determines the stability of the soldering process.

[0003] With the increasing emphasis on environmental protection, regulations stipulate that electronic products on the market must not contain lead, and other metals such as silver, copper, and bismuth must be used instead. To prevent solder powder oxidation, halogen-containing activators are usually added. However, halogen-containing solder paste can easily corrode the soldered product during use. The activators remaining after soldering can absorb moisture, leading to electrical leakage, corrosion, and greening of the product. Furthermore, halogens are harmful to the environment and human health.

[0004] In view of the above, the present invention proposes a lead-free and halogen-free solder paste with good soldering performance and resistance to corrosion of solder pads. Summary of the Invention

[0005] The purpose of this invention is to provide a lead-free and halogen-free solder paste and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a lead-free and halogen-free solder paste and its preparation method, comprising the following materials by weight percentage: 86%-90% solder powder, 10%-14% flux, wherein the solder powder is a tin-bismuth-silver alloy powder, and the flux is composed of the following materials by weight percentage: 30%-35% film-forming agent, 40%-46% solvent, 6%-8% activator, 5%-8% thixotropic agent, 3%-5% corrosion inhibitor, and 10% thermosetting resin.

[0007] As a preferred embodiment of the present invention, the solder powder is any one of Sn:Bi:Ag ratio of 42:57-57.6:0.4-1.

[0008] As a preferred embodiment of the present invention, the film-forming agent is composed of one or more of KE-604 rosin, ice white rosin, AX-E rosin, and polymerized rosin.

[0009] As a preferred embodiment of the present invention, the solvent is composed of one or more of tetrahydrofurfuryl alcohol, diethylene glycol monomethyl ether, ethylene glycol ethyl ether, and dipropylene glycol dimethyl ether.

[0010] As a preferred embodiment of the present invention, the corrosion inhibitor is one of 2-methylimidazole and benzotriazole.

[0011] As a preferred embodiment of the present invention, the thixotropic agent is prepared by a modified hydrogenated castor oil and fatty acid amide wax 6500 in an optimal mass ratio of 1:1.

[0012] As a preferred embodiment of the present invention, the activator is composed of one or more of adipic acid, succinic acid, citric acid, and glutaric acid.

[0013] As a preferred embodiment of the present invention, the thermosetting resin is composed of acrylic resin and epoxy resin in an optimal mass ratio of 2:3.

[0014] As a preferred technical solution of the present invention, a production process of lead-free and halogen-free solder paste includes the following steps: 1. Take the following materials by weight percentage: 6%-8% activator, 3%-5% corrosion inhibitor, add them to a container, set the temperature to 100℃-160℃, stir with a stirrer until completely melted and the solution becomes transparent. 2. Cool to 80℃-130℃, and take the following materials by weight percentage: 30%-35% film-forming agent, 40%-46% solvent, and 10% thermosetting resin. Add them to the solution described in step 1 and stir with a stirrer until the rosin is completely melted and the solution is transparent. 3. Heat to 100℃-140℃, take the following materials by weight percentage: 5%-8% thixotropic agent, add to the solution described in step 1, stir with a stirrer until completely melted and the solution becomes clear, cool to room temperature, and let stand for 24 hours to obtain flux; 4. Take the following materials by weight percentage: 10%-14% of the flux obtained in step 3 and 86%-90% of the solder powder, put them into a double planetary vacuum mixing chamber to obtain lead-free and halogen-free solder paste.

[0015] Compared with the prior art, the beneficial effects of the present invention are: In the lead-free and halogen-free solder paste proposed in this invention, the lead component is replaced by silver and bismuth, and the halogen activator is replaced by halogen-free organic acids.

[0016] 1. Using corrosion inhibitors can effectively prevent the organic acids in the activator from contacting the solder powder alloy powder, thus slowing down the corrosion of the alloy powder by the acid; 2. The thixotropic agent is composed of modified hydrogenated castor oil and fatty acid amide wax in an optimal mass ratio of 6500, which can significantly improve the heat slump resistance of solder paste; 3. The copolymer of rosin and thermosetting resin can not only increase the wettability of solder paste on metal substrates, but also further slow down the corrosion behavior of solder paste on substrates. Attached Figure Description

[0017] Figure 1 This is a flowchart of the preparation process of lead-free and halogen-free solder paste proposed in this invention; Figure 2 Microscopic morphology of Sn42Bi57Ag1 solder powder used in the preparation of lead-free and halogen-free solder paste proposed in this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1-2 This invention provides a technical solution for lead-free and halogen-free solder paste and its preparation method: A lead-free and halogen-free solder paste and its preparation method are disclosed, comprising the following materials by weight percentage: 86%-90% solder powder, 10%-14% flux, wherein the solder powder is a tin-bismuth-silver alloy powder, and the flux is composed of the following materials by weight percentage: 30%-35% film-forming agent, 40%-46% solvent, 6%-8% activator, 5%-8% thixotropic agent, 3%-5% corrosion inhibitor, and 10% thermosetting resin.

[0020] The solder powder is any one of Sn:Bi:Ag ratios of 42:57-57.6:0.4-1; the film-forming agent is composed of one or more of KE-604 rosin, ice white rosin, AX-E rosin, and polymerized rosin; the solvent is composed of one or more of tetrahydrofurfuryl alcohol, diethylene glycol monomethyl ether, ethylene glycol ethyl ether, and dipropylene glycol dimethyl ether; the corrosion inhibitor is one of 2-methylimidazole and benzotriazole; the thixotropic agent is composed of modified hydrogenated castor oil and fatty acid amide wax 6500 at an optimal mass ratio of 1:1; the activator is composed of one or more of adipic acid, succinic acid, citric acid, and glutaric acid; and the thermosetting resin is composed of acrylic resin and epoxy resin at an optimal mass ratio of 2:3.

[0021] A production process for lead-free and halogen-free solder paste includes the following steps: 1. Take the following materials by weight percentage: 6%-8% activator and 3%-5% corrosion inhibitor, add them to a container, set the temperature to 100℃-160℃, and stir with a stirrer until completely melted and the solution becomes transparent. 2. Cool to 80℃-130℃, and take the following materials by weight percentage: 30%-35% film-forming agent, 40%-46% solvent, and 10% thermosetting resin. Add them to the solution described in step 1 and stir with a stirrer until the rosin is completely melted and the solution is transparent. 3. Heat to 100℃-140℃, take the following materials by weight percentage: 5%-8% thixotropic agent, add to the solution described in step 1, stir with a stirrer until completely melted and the solution becomes clear, cool to room temperature, and let stand for 24 hours to obtain flux; 4. Take the following materials by weight percentage: 10%-14% of the flux obtained in step 3 and 86%-90% of the solder powder, put them into a double planetary vacuum mixing chamber to obtain lead-free and halogen-free solder paste.

[0022] Example 1

[0023] A lead-free and halogen-free solder paste comprises the following materials by weight percentage: 90% solder powder, 10% flux, wherein the solder powder has a Sn:Bi:Ag ratio of 42:57:1. For microstructure details, please refer to [link / reference]. Figure 2 The flux is composed of the following materials by weight percentage: Film-forming agents: KE-604 rosin 14%, AX-E rosin 18% Solvents: Tetrahydrofurfuryl alcohol 10%, ethylene glycol ethyl ether 15%, dipropylene glycol dimethyl ether 15% Surfactants: Adipic acid 2%, succinic acid 4%, glutaric acid 1% Corrosion inhibitor: 4% 2-methylimidazole Thixotropic agent: 7% 10% thermosetting resin The above-mentioned production process for lead-free and halogen-free solder paste includes the following steps: 1. Take the following materials by weight percentage: Activator: adipic acid 2%, succinic acid 4%, glutaric acid 1%; Corrosion inhibitor: 2-methylimidazole 4%. Add them to a container, set the temperature to 150℃, and stir with a stirrer until completely melted and the solution is transparent. 2. Cool down to 130℃ and take the following materials by weight percentage: film-forming agent: KE-604 rosin 14%, AX-E rosin 28%, solvent: tetrahydrofurfuryl alcohol 10%, ethylene glycol ethyl ether 15%, dipropylene glycol dimethyl ether 15%, thermosetting resin 10%, add to the solution described in step 1, stir with a stirrer until the rosin is completely melted and the solution is transparent; 3. Cool to 120℃ and take the following materials by weight percentage: 7% thixotropic agent, add to the solution described in step 2, stir with a stirrer until completely melted and the solution becomes clear, cool to room temperature, and let stand for 24 hours to obtain flux; 4. Take the following materials by weight percentage: 10% of the flux obtained in step 3 and 90% of the solder powder, put them into a double planetary vacuum mixer to obtain lead-free and halogen-free solder paste.

[0024] Example 2

[0025] A lead-free and halogen-free solder paste comprises the following materials by weight percentage: 89% solder powder, 11% flux, wherein the solder powder has a Sn:Bi:Ag ratio of 42:57.6:0.4. The flux is composed of the following materials by weight percentage: Film-forming agents: KE-604 rosin 10%, AX-E rosin 10%, Ice White rosin 15% Solvents: Tetrahydrofurfuryl alcohol 15%, diethylene glycol monomethyl ether 10%, ethylene glycol ethyl ether 15% Surfactants: 2% succinic acid, 4% citric acid Corrosion inhibitor: 4% 2-methylimidazole Thixotropic agent: 5% 10% thermosetting resin The above-mentioned production process for lead-free and halogen-free solder paste includes the following steps: 1. Take the following materials by weight percentage: surfactant: succinic acid 2%, citric acid 4%, corrosion inhibitor: 2-methylimidazole 4%, add to a container, set the temperature to 160℃, stir with a stirrer until completely melted and the solution is transparent; 2. Cool to 130℃ and take the following materials by weight percentage: film-forming agent: KE-604 rosin 10%, AX-E rosin 20%, ice white rosin 15%; solvent: tetrahydrofurfuryl alcohol 10%, ethylene glycol ethyl ether 15%, dipropylene glycol dimethyl ether 15%; thermosetting resin 10%, add to the solution described in step 1, stir with a stirrer until the rosin is completely melted and the solution is transparent; 3. Cool to 120℃ and take the following materials by weight percentage: 7% thixotropic agent, add to the solution described in step 2, stir with a stirrer until completely melted and the solution becomes clear, cool to room temperature, and let stand for 24 hours to obtain flux; 4. Take the following materials by weight percentage: 11% flux obtained in step 3 and 89% solder powder, put them into a double planetary vacuum mixer to obtain lead-free and halogen-free solder paste.

[0026] Example 3

[0027] A lead-free and halogen-free solder paste comprises the following materials by weight percentage: 86% solder powder, 14% flux, wherein the solder powder has a Sn:Bi:Ag ratio of 42:57:1. The flux is composed of the following materials by weight percentage: Film-forming agent: 20% AX-E rosin, 12% polymerized rosin Solvents: 10% tetrahydrofurfuryl alcohol, 35% dipropylene glycol dimethyl ether Surfactant: 7% glutaric acid Corrosion inhibitor: 3% benzotriazole Thixotropic agent: 5% 10% thermosetting resin The above-mentioned production process for lead-free and halogen-free solder paste includes the following steps: 1. Take the following materials by weight percentage: film-forming agent: AX-E rosin 20%, polymerized rosin 22%, solvent: tetrahydrofurfuryl alcohol 10%, dipropylene glycol dimethyl ether 35%, temperature set at 120℃, thermosetting resin 10%, stir with a stirrer until the rosin is completely melted and the solution is transparent; 2. Cool to 100℃ and take the following materials by weight percentage: activator: glutaric acid 7%, corrosion inhibitor: benzotriazole 3%, add to the container, add to the solution described in step 1, stir with a stirrer until completely melted and the solution becomes clear; 3. Heat to 120℃ and take the following materials by weight percentage: 5% thixotropic agent, add to the solution described in step 2, stir with a stirrer until the rosin is completely melted and the solution is clear, cool to room temperature, and let stand for 24 hours to obtain flux; 4. Take the following materials by weight percentage: 14% flux obtained in step 3 and 86% solder powder, put them into a double planetary vacuum mixer to obtain lead-free and halogen-free solder paste.

[0028] Example 4

[0029] A lead-free and halogen-free solder paste comprises the following materials by weight percentage: 90% solder powder, 10% flux, wherein the solder powder has a Sn:Bi:Ag ratio of 42:57.6:0.4. The flux is composed of the following materials by weight percentage: Film-forming agents: KE-604 rosin 15%, AX-E rosin 15% Solvents: 20% tetrahydrofurfuryl alcohol, 20% ethylene glycol ethyl ether Surfactants: 4% adipic acid, 4% glutaric acid Corrosion inhibitor: 5% benzotriazole Thixotropic agent: 7% 10% thermosetting resin The above-mentioned production process for lead-free and halogen-free solder paste includes the following steps: 1. Take the following materials by weight percentage: activator: adipic acid 4%, glutaric acid 4%, corrosion inhibitor: benzotriazole 5%, add to a container, set the temperature to 150℃, stir with a stirrer until completely melted and the solution is clear; 2. Cool down to 130℃ and take the following materials by weight percentage: film-forming agent: KE-604 rosin 15%, AX-E rosin 25%, solvent: tetrahydrofurfuryl alcohol 20%, ethylene glycol ethyl ether 20%, thermosetting resin 10%, add to the solution described in step 1, stir with a stirrer until the rosin is completely melted and the solution is transparent; 3. Cool to 120℃ and take the following materials by weight percentage: 7% thixotropic agent, add to the solution described in step 2, stir with a stirrer until completely melted and the solution becomes clear, cool to room temperature, and let stand for 24 hours to obtain flux; 4. Take the following materials by weight percentage: 11% flux obtained in step 3 and 89% solder powder, put them into a double planetary vacuum mixer to obtain lead-free and halogen-free solder paste.

[0030] The use of corrosion inhibitors can effectively block the contact of organic acids in the activator with the solder powder alloy powder, thus slowing down the corrosion of the alloy powder by the acid; the thixotropic agent, with the optimal mass ratio of modified hydrogenated castor oil to fatty acid amide wax 6500, can significantly improve the heat slump resistance of the solder paste; the copolymer of rosin and thermosetting resin can not only increase the wettability of the solder paste to the metal substrate, but also further slow down the corrosion behavior of the solder paste on the substrate.

[0031] In the description of this invention, it should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0032] In this invention, unless otherwise explicitly specified and limited, for example, it can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two elements or an interaction between two elements. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A lead-free and halogen-free solder paste and its preparation method, characterized in that: The material comprises the following weight percentages: 86%-90% solder powder, 10%-14% flux, wherein the solder powder is a tin-bismuth-silver alloy powder, and the flux is composed of the following weight percentages: 30%-35% film-forming agent, 40%-46% solvent, 6%-8% activator, 5%-8% thixotropic agent, 3%-5% corrosion inhibitor, and 10% thermosetting resin.

2. The lead-free and halogen-free solder paste and its preparation method according to claim 1, characterized in that: The solder powder is any one of Sn:Bi:Ag ratios of 42:57-57.6:0.4-1.

3. The lead-free and halogen-free solder paste and its preparation method according to claim 1, characterized in that: The film-forming agent is composed of one or more of KE-604 rosin, ice white rosin, AX-E rosin, and polymerized rosin.

4. The lead-free and halogen-free solder paste and its preparation method according to claim 1, characterized in that: The solvent is composed of one or more of tetrahydrofurfuryl alcohol, diethylene glycol monomethyl ether, ethylene glycol ethyl ether, and dipropylene glycol dimethyl ether.

5. The lead-free and halogen-free solder paste and its preparation method according to claim 1, characterized in that: The corrosion inhibitor is either 2-methylimidazole or benzotriazole.

6. The lead-free and halogen-free solder paste and its preparation method according to claim 1, characterized in that: The thixotropic agent is composed of modified hydrogenated castor oil and fatty acid amide wax 6500 in an optimal mass ratio of 1:

1.

7. The lead-free and halogen-free solder paste and its preparation method according to claim 1, characterized in that: The activator is composed of one or more of adipic acid, succinic acid, citric acid, and glutaric acid.

8. The lead-free and halogen-free solder paste and its preparation method according to claim 1, characterized in that: The thermosetting resin is composed of acrylic resin and epoxy resin in an optimal mass ratio of 2:

3.

9. The lead-free and halogen-free solder paste and its preparation method according to claim 1, characterized in that: A production process for lead-free and halogen-free solder paste includes the following steps:

1. Take the following materials by weight percentage: 6%-8% activator and 3%-5% corrosion inhibitor, add them to a container, set the temperature to 100℃-160℃, and stir with a stirrer until completely melted and the solution becomes transparent. Cool the temperature to 80℃-130℃ and take the following materials by weight percentage: 30%-35% film-forming agent, 40%-46% solvent, and 10% thermosetting resin. Add them to the solution described in step 1 and stir with a stirrer until the rosin is completely melted and the solution is transparent. Heat the temperature to 100℃-140℃ and take the following weight percentage of materials: 5%-8% thixotropic agent, add to the solution described in step 1, stir with a stirrer until completely melted and the solution becomes clear, cool to room temperature, and let stand for 24 hours to obtain flux; Take the following materials by weight percentage: 10%-14% of the flux obtained in step 3 and 86%-90% of the solder powder, put them into a double planetary vacuum mixing chamber to obtain lead-free and halogen-free solder paste.

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