High-performance heat-resistant soldering paste and preparation method thereof

Abstract

The application discloses a high-performance heat-resistant soldering tin paste and a preparation method thereof. The soldering tin paste is composed of solder powder, soldering flux and heat stabilizer, and the mass percentage of the soldering tin paste is as follows: the solder powder is 85-91.9%, the soldering flux is 8-14.5%, and the heat stabilizer is 0.1-0.5%. The soldering tin paste prepared by the application has low welding temperature, high activity, good heat stability, and is suitable for normal-temperature storage, transportation and application. The product has excellent welding performance, high reliability, and can effectively avoid the quality problems of low-tension soldering point, poor wetting, and easy drying at normal temperature or high temperature after soldering of the tin-bismuth series low-temperature soldering tin paste.

Description

Technical Field

[0001] This invention belongs to the technical field of low-temperature soldering materials for soft soldering, and specifically relates to a high-performance heat-resistant solder paste and its preparation method as a soldering material for electronic products. Background Technology

[0002] With the integration and miniaturization of electronic information products, SnAgCu alloy solder paste, used as an SMT soldering material, is prone to problems such as circuit board deformation and poor component soldering due to its high soldering temperature (above 240℃). The industry has begun to research the application of low-temperature tin-bismuth alloy solder pastes. However, because these solder pastes contain a large amount of bismuth metal, the solder joint strength is low, and they also suffer from drying out during storage and application, especially in summer when temperatures reach around 40℃, the adverse effects are even greater. Some SMT manufacturers fail to promptly repair faulty solder paste storage refrigerators, resulting in solder paste being stored at room temperature. Other SMT manufacturers lack air conditioning control in their solder paste usage environments, leading to solder paste drying out and becoming unusable. Therefore, the market has placed higher demands on the storage and application of solder paste, and providing high-performance heat-resistant solder paste to meet market needs is an urgent problem that solder paste manufacturers must solve. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-performance heat-resistant solder paste with low soldering temperature, high activity, good thermal stability and excellent solderability, as well as a preparation method thereof.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A high-performance heat-resistant solder paste, comprising solder powder, flux, and heat stabilizer; wherein the mass percentages are: solder powder 85-91.9%, flux 8-14.5%, and heat stabilizer 0.1-0.5%;

[0006] The solder powder includes tin-bismuth-silver alloy powder and nano-copper powder, wherein the nano-copper powder accounts for 0.03% to 0.05% by mass.

[0007] The flux paste comprises 60% by weight of inactive A flux paste and 40% by weight of active B flux paste. The A flux paste comprises 15% by weight of rosin glycerol ester, 8% by weight of thixotropic agent, 2% by weight of antioxidant, and 35% by weight of solvent. The B flux paste comprises 20% by weight of hydrogenated rosin, 10% by weight of activator, and 10% by weight of solvent.

[0008] The tin-bismuth-silver alloy powder is Sn42Bi57Ag1 alloy powder;

[0009] The thixotropic agent is one of Crayvallac Ultra, CRAYVALLAC SF, and CRAY VALLEY MT;

[0010] The antioxidant is IRGANOX 1098;

[0011] The active agent is one or more of adipic acid, sebacic acid, glutaric acid, succinic acid, and succinic anhydride;

[0012] The solvent is one of diethylene glycol hexyl ether and diethylene glycol butyl ether;

[0013] The heat stabilizer is methyltin mercaptan.

[0014] The method for preparing the high-performance heat-resistant solder paste of the present invention includes the following steps:

[0015] (1) Place rosin glycerol ester, thixotropic agent, antioxidant and solvent into a reactor in proportion and heat to 140-150℃. After the solid material is completely melted and stirred evenly, cool to obtain non-active A flux paste.

[0016] (2) Place hydrogenated rosin, activator and solvent into a reactor in proportion and heat to 130-140℃. After the solid material is completely melted and stirred evenly, the active B flux is obtained after cooling.

[0017] (3) Mix the tin-bismuth-silver alloy powder and nano copper powder evenly, and mix them with flux A evenly to obtain a mixture;

[0018] (4) Add flux B and methyl tin mercaptan to the mixture and continue stirring until homogeneous to obtain the high-performance heat-resistant solder paste.

[0019] The reason solder paste dries out during storage or use is that the activator in the flux reacts with the solder powder, causing continuous corrosion between the grain boundaries of the alloy powder, forming pores. A large amount of flux enters these pores, accelerating corrosion and forming metal oxides, leading to the solder paste drying out. Based on an in-depth analysis of the defects and formation mechanisms of existing solder paste technology, this invention proposes an effective technical solution. This invention has at least the following advantages:

[0020] (1) This invention divides the flux system into two groups: inactive and active. The inactive flux uses non-acidic rosin glycerol ester as a film-forming agent, and forms an inactive paste with antioxidants, thixotropic agents and certain solvents. The active flux uses high-acid-value hydrogenated rosin as a film-forming agent, and forms a highly active paste with organic acids, organic amines and solvents. When preparing solder paste, the inactive flux is first mixed with the solder powder and stirred evenly. The inactive flux first coats the solder powder, especially filling the cracks in the solder powder with flux without active agents, effectively reducing intergranular corrosion. It provides a protective film for the solder powder, preventing the solder powder from directly contacting and reacting rapidly with the active agent. When the active flux is added and mixed, the probability of the active agents such as organic acids and organic amines in the flux reacting with the solder powder is greatly reduced. Furthermore, the heat stabilizer inhibits the reaction between the solder powder and the organic active agent when heated, further enhancing the stability of the solder during transportation and storage.

[0021] (2) The high-performance heat-resistant solder paste of the present invention contains a trace amount of the heat stabilizer methyl tin mercaptan, which effectively inhibits the reaction between the solder metal and organic matter at high temperature and enhances the thermal stability of the solder paste. During the reflow process, the highly active organic acids and organic amines decompose upon heating to remove oxides from the pads and components. After the solder melts, it exhibits excellent wetting properties, ensuring the good solderability of the solder paste.

[0022] (3) The present invention uses the addition of trace amounts of nano copper powder to enhance the tensile strength of tin-bismuth-silver solder joints, increase the reliability of solder joints, and effectively solve the problems of high brittleness and low tensile strength of solder joints.

[0023] The solder paste prepared by this invention has a low soldering temperature, high activity, and good thermal stability, making it suitable for storage, transportation, and application at room temperature. Furthermore, the product exhibits excellent solderability and high reliability, effectively avoiding quality problems such as low tensile strength, poor wetting, and easy drying at room or high temperatures after soldering with tin-bismuth series low-temperature solder pastes. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments.

[0025] Example 1

[0026] This embodiment provides a high-performance heat-resistant solder paste, wherein the solder paste comprises, by mass percentage: 85% solder powder, 14.5% flux, and 0.5% heat stabilizer methyl tin mercaptan. Detailed formulation is as follows:

[0027] The solder powder includes 99.97 wt% Sn42Bi57Ag1 alloy powder and 0.03 wt% nano copper powder;

[0028] The flux consists of 60 wt% inactive flux A and 40 wt% active flux B. Inactive flux A includes 15% rosin glycerol ester, 8% thixotropic agent Crayvallac Ultra, 2% antioxidant IRGANOX 1098, and 35% diethylene glycol hexyl ether. Active flux B includes 20% hydrogenated rosin, 5% adipic acid, 5% sebacic acid, and 10% diethylene glycol hexyl ether.

[0029] The preparation method of high-performance heat-resistant solder paste is as follows:

[0030] (1) Place rosin glycerol ester, thixotropic agent Crayvallac Ultra, antioxidant IRGANOX 1098 and diethylene glycol hexyl ether into a reactor in proportion and heat to 140-150℃. After the solid materials are completely melted and stirred evenly, cool to obtain non-active A flux paste.

[0031] (2) Hydrogenated rosin, adipic acid, sebacic acid and diethylene glycol hexyl ether are placed in a reactor in proportion and heated to 130-140°C. After the solid materials are completely melted and stirred evenly, the active B flux is obtained after cooling.

[0032] (3) Mix Sn42Bi57Ag1 alloy powder and nano copper powder evenly, and mix them with flux A evenly to obtain a mixture;

[0033] (4) Add flux B and methyl tin mercaptan to the mixture and continue stirring until homogeneous to obtain high-performance heat-resistant solder paste.

[0034] Example 2

[0035] This embodiment provides a high-performance heat-resistant solder paste, wherein the solder paste comprises the following percentages: 87% solder powder, 12.6% flux, and 0.4% heat stabilizer methyl tin mercaptan. Detailed formulation is as follows:

[0036] The solder powder consists of 99.96 wt% Sn42Bi57Ag1 alloy powder and 0.04 wt% nano copper powder;

[0037] The solder paste comprises 60 wt% inactive flux A and 40 wt% active flux B. Inactive flux A includes 15% rosin glycerol ester, 8% thixotropic agent CRAYVALLAC SF, 2% antioxidant IRGANOX 1098, and 35% diethylene glycol hexyl ether. Active flux B includes 20% hydrogenated rosin, 5% glutaric acid, 5% caprylic acid, and 10% diethylene glycol hexyl ether.

[0038] The preparation method of high-performance heat-resistant solder paste is as follows:

[0039] (1) Place rosin glycerol ester, thixotropic agent CRAYVALLAC SF, antioxidant IRGANOX 1098 and diethylene glycol hexyl ether into a reactor in proportion and heat to 140-150℃. After the solid material is completely melted and stirred evenly, cool to obtain non-active A flux paste.

[0040] (2) Hydrogenated rosin, glutaric acid, octanoic acid and diethylene glycol hexyl ether are placed in a reactor in proportion and heated to 130-140°C. After the solid materials are completely melted and stirred evenly, the active B flux is obtained after cooling.

[0041] (3) Mix Sn42Bi57Ag1 alloy powder and nano copper powder evenly, and mix them with flux A evenly to obtain a mixture;

[0042] (4) Add flux B and methyl tin mercaptan to the mixture and continue stirring until homogeneous to obtain high-performance heat-resistant solder paste.

[0043] Example 3

[0044] This embodiment provides a high-performance heat-resistant solder paste, wherein the solder paste comprises: 88.5% solder powder, 11.2% flux, and 0.3% heat stabilizer methyl tin mercaptan. Detailed formulation is as follows:

[0045] The solder powder includes 99.95 wt% Sn42Bi57Ag1 alloy powder and 0.05 wt% nano copper powder;

[0046] The flux consists of 60 wt% inactive flux A and 40 wt% active flux B. Inactive flux A includes 15% rosin glycerol ester, 8% thixotropic agent Crayvallac Ultra, 2% antioxidant IRGANOX 1098, and 35% diethylene glycol butyl ether. Active flux B includes 20% hydrogenated rosin, 5% adipic acid, 5% sebacic acid, and 10% diethylene glycol butyl ether.

[0047] The preparation method of high-performance heat-resistant solder paste is as follows:

[0048] (1) Place rosin glycerol ester, thixotropic agent Crayvallac Ultra, antioxidant IRGANOX 1098 and diethylene glycol butyl ether into a reactor in proportion and heat to 140-150℃. After the solid materials are completely melted and stirred evenly, cool to obtain non-active A flux paste.

[0049] (2) Place hydrogenated rosin, adipic acid, sebacic acid and diethylene glycol butyl ether into a reactor in proportion and heat to 130-140°C. After the solid materials are completely melted and stirred evenly, the active B flux is obtained after cooling.

[0050] (3) Mix Sn42Bi57Ag1 alloy powder and nano copper powder evenly, and mix them with flux A evenly to obtain a mixture;

[0051] (4) Add flux B and methyl tin mercaptan to the mixture and continue stirring until homogeneous to obtain high-performance heat-resistant solder paste.

[0052] Example 4

[0053] This embodiment provides a high-performance heat-resistant solder paste, wherein the solder paste comprises: 90% solder powder, 9.8% flux, and 0.2% heat stabilizer methyl tin mercaptan. Detailed formulation is as follows:

[0054] The solder powder includes 99.96 wt% Sn42Bi57Ag1 alloy powder and 0.04 wt% nano copper powder;

[0055] The solder paste comprises 60 wt% inactive flux A and 40 wt% active flux B. Inactive flux A includes 15% rosin glycerol ester, 8% thixotropic agent CRAY VALLEY MT, 2% antioxidant IRGANOX 1098, and 35% diethylene glycol hexyl ether. Active flux B includes 20% hydrogenated rosin, 5% sebacic acid, 5% caprylic acid, and 10% diethylene glycol hexyl ether.

[0056] The preparation method of high-performance heat-resistant solder paste is as follows:

[0057] (1) Place rosin glycerol ester, thixotropic agent CRAY VALLEY MT, antioxidant IRGANOX 1098 and diethylene glycol hexyl ether into a reactor in proportion and heat to 140-150℃. After the solid materials are completely melted and stirred evenly, cool to obtain non-active A flux paste.

[0058] (2) Hydrogenated rosin, sebacic acid, octanoic acid and diethylene glycol hexyl ether are placed in a reactor in proportion and heated to 130-140°C. After the solid materials are completely melted and stirred evenly, the active B flux is obtained after cooling.

[0059] (3) Mix Sn42Bi57Ag1 alloy powder and nano copper powder evenly, and mix them with flux A evenly to obtain a mixture;

[0060] (4) Add flux B and methyl tin mercaptan to the mixture and continue stirring until homogeneous to obtain high-performance heat-resistant solder paste.

[0061] Example 5

[0062] This embodiment provides a high-performance heat-resistant solder paste, wherein the solder paste comprises the following percentages: 92% solder powder, 7.9% flux, and 0.1% heat stabilizer methyl tin mercaptan. Detailed formulation is as follows:

[0063] The solder powder includes 99.95 wt% Sn42Bi57Ag1 alloy powder and 0.05 wt% nano copper powder;

[0064] The flux consists of 60 wt% inactive flux A and 40 wt% active flux B. Inactive flux A includes 15% rosin glycerol ester, 8% thixotropic agent Crayvallac Ultra, 2% antioxidant IRGANOX 1098, and 35% diethylene glycol hexyl ether. Active flux B includes 20% hydrogenated rosin, 5% succinic anhydride, 5% sebacic acid, and 10% diethylene glycol butyl ether.

[0065] The preparation method of high-performance heat-resistant solder paste is as follows:

[0066] (1) Place rosin glycerol ester, thixotropic agent Crayvallac Ultra, antioxidant IRGANOX 1098 and diethylene glycol hexyl ether into a reactor in proportion and heat to 140-150℃. After the solid materials are completely melted and stirred evenly, cool to obtain non-active A flux paste.

[0067] (2) Hydrogenated rosin, succinic anhydride, sebacic acid and diethylene glycol butyl ether are placed in a reactor in proportion and heated to 130-140°C. After the solid materials are completely melted and stirred evenly, the active B flux is obtained after cooling.

[0068] (3) Mix Sn42Bi57Ag1 alloy powder and nano copper powder evenly, and mix them with flux A evenly to obtain a mixture;

[0069] (4) Add flux B and methyl tin mercaptan to the mixture and continue stirring until homogeneous to obtain high-performance heat-resistant solder paste.

[0070] Unless otherwise stated, all percentages mentioned in this invention are mass percentages.

[0071] The nano-copper powder described in this invention is copper powder with a particle size of less than 100 nm. The solder powder, rosin glycerol ester, hydrogenated rosin, thixotropic agent, antioxidant, activator, solvent, and stabilizer methyltin mercaptan mentioned above are all commercially available. The reactor used in the preparation method of this invention is existing technology equipment.

[0072] Performance Evaluation

[0073] A commercially available low-temperature solder paste with the same alloy (Sn42Bi57Ag1) was compared with the high-performance heat-resistant solder paste prepared in the above embodiment. The commercially available low-temperature solder paste (Sn42Bi57Ag1 alloy) and the solder paste from the above embodiment were printed on a PCB board, components were mounted, and reflow soldering was performed. Five identical capacitor components were used for push-pull force testing. The push-pull force that the solder joints could withstand is shown in Table 1, with the unit of push force being g. The solder paste was then placed in a 40℃ constant temperature chamber for thermal stability testing. The state of the solder paste was observed every 1, 3, 10, and 30 days, and the test results are compared in Table 2. Tables 1 and 2 show that the thermal stability and push-pull force resistance reliability of the solder joints of the present invention are superior to those of the commercially available solder paste with the same alloy.

[0074] Table 1 Weld joint thrust test

[0075]

[0076] Table 2 Thermal stability test of solder paste

[0077]

[0078] Other embodiments of the present invention can also be prepared using other proportions as described in the claims and specification. The foregoing embodiments are merely illustrative, used to explain some features of the method described in the present invention, and the embodiments presented herein are merely illustrative of selected implementations based on combinations of all possible embodiments. The appended claims are intended to claim the broadest possible scope.

Claims

1. A high-performance heat-resistant solder paste, characterized in that: The solder paste is composed of solder powder, flux, and heat stabilizer; its mass percentage is: solder powder 85-91.9%, flux 8-14.5%, and heat stabilizer 0.1-0.5%. The solder powder comprises tin-bismuth-silver alloy powder and nano-copper powder, wherein the nano-copper powder accounts for 0.03% to 0.05% by mass. The flux paste comprises 60% by weight of inactive A flux paste and 40% by weight of active B flux paste. The inactive A flux paste comprises 15% by weight of rosin glycerol ester, 8% by weight of thixotropic agent, 2% by weight of antioxidant, and 35% by weight of solvent. The active B flux paste comprises 20% by weight of hydrogenated rosin, 10% by weight of activator, and 10% by weight of solvent. The tin-bismuth-silver alloy powder is Sn42Bi57Ag1 alloy powder; The thixotropic agent is one of Crayvallac Ultra, CRAYVALLAC SF, and CRAY VALLEY MT; The antioxidant is IRGANOX 1098; The active agent is one or more of adipic acid, sebacic acid, glutaric acid, succinic acid, and succinic anhydride; The solvent is one of diethylene glycol hexyl ether and diethylene glycol butyl ether; The heat stabilizer is methyltin mercaptan.

2. The method for preparing a high-performance heat-resistant solder paste as described in claim 1, characterized in that, Includes the following steps: (1) Place rosin glycerol ester, thixotropic agent, antioxidant and solvent into a reactor in proportion and heat to 140-150℃. After the solid material is completely melted and stirred evenly, cool to obtain non-active A flux paste. (2) Place hydrogenated rosin, activator and solvent into a reactor in proportion and heat to 130-140℃. After the solid material is completely melted and stirred evenly, the active B flux is obtained after cooling. (3) Mix the tin-bismuth-silver alloy powder and nano copper powder evenly, and mix them evenly with non-active A flux to obtain a mixture; (4) Add active B flux and thiol methyl tin to the mixture and continue stirring until homogeneous to obtain the high-performance heat-resistant solder paste.

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