A solder bar with low melting point and high service life and its preparation process

Abstract

The present invention relates to the technical field of solder bar preparation, and specifically to a solder bar with a low melting point and high temperature service and a preparation process thereof. A solder bar with a low melting point and high temperature service and a preparation process thereof comprise: preparation of a synthetic resin, preparation of a flux, and preparation of a solder bar. The present invention uses a low melting point alloy as a matrix and adds indium. The introduction of indium can significantly reduce the melting point of the tin-based alloy, allowing the solder bar to melt at a lower temperature, meeting the requirements of low-temperature welding. Nano-GaN particles and nano-scale Cu@Ni core-shell structure particles are added, and the synergistic effect between the two improves the stability of the solder joint in a high-temperature working environment.

Description

Technical Field

[0001] The invention relates to the technical field of solder bar preparation, and in particular to a solder bar with a low melting point and high service life and a preparation process thereof. Background Art

[0002] In electronic equipment manufacturing, solder joints are key components for achieving electrical connections and mechanical fixation, and their reliability directly impacts the overall performance and service life of the product. As a commonly used welding material, solder bars play an indispensable role in various electronic assembly processes. The rapid advancement of electronic technology toward miniaturization and higher performance has placed increasingly stringent demands on the performance of solder bars.

[0003] On the one hand, the integration density of electronic components continues to rise, and a large number of heat-sensitive components are widely used. This makes traditional high-melting-point solder bars, due to the high temperatures required during the soldering process, highly susceptible to thermal damage to heat-sensitive components, leading to performance degradation or even failure. On the other hand, the service environment of electronic equipment is becoming increasingly complex and diverse, with harsh conditions such as high temperature, high humidity, and strong electromagnetic interference becoming commonplace. In such environments, solder joints must possess excellent high-temperature stability to ensure the reliability of electrical connections and the integrity of mechanical structures.

[0004] However, some existing low-melting-point solder bars are prone to softening, creeping, and even desoldering when used at high temperatures, which severely limits the stable operation of electronic devices in high-temperature environments.

[0005] Therefore, it is urgent to develop a low-temperature melting point and high-temperature service solder bar and its preparation process that can complete welding at low temperatures and still maintain good performance when serving at high temperatures. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a solder bar with a low melting point and high temperature service and a preparation process thereof.

[0007] A solder bar with a low melting point and high service life, comprising, by weight percentage:

[0008] Tin alloy 90.3-91.2%, functional filler 4-5% and the balance flux;

[0009] The tin alloy is 3-5% bismuth, 1.8-2.4% silver, 0.2-0.3% indium, 0.05-0.07% cerium, 0.03-0.08% germanium and the balance tin;

[0010] The functional fillers are nano-GaN particles and nano-scale Cu@Ni core-shell structure particles, and the mass ratio of nano-GaN particles to Cu@Ni core-shell structure particles is 1:10-12;

[0011] The flux is composed of modified rosin, activator, corrosion inhibitor, synthetic resin, thixotropic agent and organic solvent in a mass ratio of 5-6:1-2:2-3:0.3-0.5:0.4-0.8:3-5;

[0012] Synthetic resin is a rosin resin prepared from refined rosin and glycidyl methacrylate via epoxy ring-opening reaction.

[0013] As a preferred aspect, the activator is composed of itaconic acid, diphenylguanidine, and triethanolamine in a mass ratio of 1:2:0.2-0.3.

[0014] As a preferred aspect, the modified rosin is one or more of maleic rosin, hydrogenated rosin and acrylic rosin.

[0015] As a preferred aspect, the corrosion inhibitor is one or more of benzothiazole, benzotriazole, and benzimidazole.

[0016] As a preferred aspect, the thixotropic agent is one or more of fatty acid amide, stearyl wax, and hydrogenated castor oil.

[0017] The present invention also provides a process for preparing a solder bar with a low melting point and high service life. The specific steps of preparing the solder bar include:

[0018] S1. Preparation of synthetic resin;

[0019] 300-320 parts by weight of refined rosin, 152-155 parts by weight of glycidyl methacrylate, 2-3 parts by weight of potassium hydroxide and 0.9-1 part by weight of p-hydroxyanisole are mixed, and the mixture is stirred under a nitrogen atmosphere while being refluxed at a temperature of 80-82° C. until the acid value reaches 2-5 mgKOH / g, thereby obtaining a synthetic resin;

[0020] S2. Preparation of flux;

[0021] The modified rosin, synthetic resin, activator, corrosion inhibitor, thixotropic agent and organic solvent are mixed in the above mass ratio and stirred for 20-30 minutes to obtain a soldering flux;

[0022] S3, preparation of solder bars;

[0023] The components of the tin alloy are heated and melted in sequence according to the melting points of each material. When all substances are melted into liquid, functional fillers and flux are added under a nitrogen atmosphere. Ultrasonic stirring is performed at 300-500W for 30-40 minutes. After that, impurities floating on the molten surface are removed, and the mixture is poured into a mold and cooled to form a solder bar.

[0024] As a preferred aspect, a 0.13-0.15T rotating magnetic field is applied during pouring and cooling molding in step S3, and the rotation speed is 50-80r / min.

[0025] The present invention has the following advantages:

[0026] 1. The present invention uses a low-melting-point alloy as the matrix and adds indium. The introduction of indium can significantly lower the melting point of the tin-based alloy, allowing the solder bar to melt at a lower temperature, meeting the requirements of low-temperature welding. Cerium and germanium, as microalloying elements, mainly function to refine the grains, improve wettability and oxidation resistance, and help form solder joints with good performance at lower temperatures. At the same time, silver and tin can form stable intermetallic compounds. These compounds are not easy to soften at high temperatures, can pin dislocation movement, and significantly improve the high-temperature strength and creep resistance of the alloy. Cerium, as a rare earth element, can refine the tin alloy grains and inhibit grain growth. The refined grain boundaries can enhance the deformation resistance at high temperatures. Germanium can reduce the grain boundary energy of the tin alloy, inhibit the migration and slip of grain boundaries at high temperatures, and further improve the creep resistance, thereby achieving stable operation in a high-temperature environment.

[0027] 2. The present invention incorporates nano-GaN particles and nano-scale Cu@Ni core-shell structured particles. The nano-GaN particles dispersed in the tin alloy matrix can form "rigid support points" that hinder plastic deformation of the matrix at high temperatures, while improving the overall thermal conductivity and reducing thermal stress concentration at high temperatures. Higher thermal conductivity means that the solder joint can more effectively conduct heat away from the solder joint under high-temperature working conditions, reducing the operating temperature of the solder joint itself, thereby slowing down thermal aging, creep, and failure processes. In addition, the nano-GaN particles can significantly improve the hardness of the solder joint. The Cu@Ni core-shell structured particles can inhibit grain coarsening of the tin alloy matrix at high temperatures and share external forces through the "load transfer" effect, thereby improving the shear strength and fatigue performance of the solder joint at high temperatures. The Cu@Ni core-shell structured particles provide excellent dispersion strengthening and grain boundary pinning, significantly improving high-temperature strength, hardness, and creep resistance. The Ni shell protects the Cu core from excessive dissolution and forms a stable and strengthened IMC. The Cu@Ni core-shell structured particles provide interface strengthening, and the GaN enhances the overall rigidity. The synergistic effect between the two improves the stability of the solder joint under high-temperature working conditions.

[0028] 3. The present invention adds a synthetic resin to the soldering flux. The synthetic resin has a rosin ester as a skeleton. The non-polar skeleton of the rosin ester can be embedded in the molten solder, and its polar groups are oriented toward the interface between the solder melt and the metal oxide surface. Through this directional adsorption behavior at the interface, the surface tension of the molten state is reduced, the spreading of the solder on the metal surface is promoted, the cold solder joints and false solder joints are reduced, the bonding strength of the solder joints is improved, and the solderability is good. At the same time, the polar groups can form hydrogen bonds with the metal oxides to weaken the adhesion of the oxide layer and promote the peeling of the oxide film. It can also form a hydrogen bond network with activators such as itaconic acid to improve the efficiency of removing the oxide film. The rigid rosin ring structure of the synthetic resin has better heat resistance, avoids carbonization at high temperatures, reduces residue generation, and prevents the residue from affecting the wettability of the solder and the quality of the solder joints, thereby ensuring the stability of the welding process.

[0029] 4. The present invention applies a rotating magnetic field during the pouring and cooling molding process. The rotating magnetic field induces eddy currents in the molten alloy, and the nanoscale Cu@Ni core-shell particles and GaN particles rotate under the action of the Lorentz force. The Ni shell magnetic moment of the Cu@Ni particles is arranged along the direction of the magnetic field, which can construct an efficient heat conduction path, so that the solder joint can more effectively conduct heat under high-temperature working environment. At the same time, it strengthens the dispersed distribution of particles and avoids agglomeration and sedimentation. The continuous shear force of the rotating magnetic field offsets the gravity sedimentation, ensuring uniform distribution of the filler. The uniformly distributed filler is conducive to improving the stability of the solder joint under high-temperature working environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a process flow chart for preparing a low-melting-point, high-temperature-service solder bar used in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0032] Example 1, a process for preparing a solder bar with a low melting point and high service life, see Figure 1 ,include:

[0033] S1. Preparation of synthetic resin;

[0034] 300 parts by weight of refined rosin, 152 parts by weight of glycidyl methacrylate, 2 parts by weight of potassium hydroxide and 0.9 parts by weight of p-hydroxyanisole were mixed, and the mixture was stirred under a nitrogen atmosphere and refluxed at a temperature of 80° C. until the acid value reached 2 mgKOH / g, thereby obtaining a synthetic resin;

[0035] S2. Preparation of flux;

[0036] Modified rosin, synthetic resin, activator, corrosion inhibitor, thixotropic agent and organic solvent were mixed in a mass ratio of 5:1:2:0.3:0.4:3, and stirred for 20 minutes to obtain a flux;

[0037] The activator is composed of itaconic acid, diphenylguanidine, and triethanolamine in a mass ratio of 1:2:0.2;

[0038] S3, preparation of solder bars;

[0039] The materials were weighed according to 3% bismuth, 1.8% silver, 0.2% indium, 0.05% cerium, 0.03% germanium and the balance tin. The materials were then heated and melted in sequence according to the melting points of the materials in the tin alloy. When all the substances were melted into liquid, functional fillers and flux were added under a nitrogen atmosphere. Ultrasonic stirring was performed at 300W for 30 minutes. After that, impurities floating on the molten surface were removed, and the mixture was poured into a mold and cast and cooled to form. At the same time, a 0.13T rotating magnetic field was applied at a speed of 50r / min. Solder bars were obtained after forming.

[0040] The proportion of each component in solder is 90.3% tin alloy, 4% functional filler and the balance flux;

[0041] The functional fillers are nano-GaN particles and nano-scale Cu@Ni core-shell structure particles, and the mass ratio of nano-GaN particles and Cu@Ni core-shell structure particles is 1:10.

[0042] Example 2, a process for preparing a solder bar with a low melting point and high service life, see Figure 1 ,include:

[0043] S1. Preparation of synthetic resin;

[0044] 320 parts by weight of refined rosin, 155 parts by weight of glycidyl methacrylate, 3 parts by weight of potassium hydroxide and 1 part by weight of p-hydroxyanisole were mixed, and the mixture was refluxed under stirring at 80° C. under a nitrogen atmosphere until the acid value reached 2 mgKOH / g, thereby obtaining a synthetic resin;

[0045] S2. Preparation of flux;

[0046] Modified rosin, synthetic resin, activator, corrosion inhibitor, thixotropic agent and organic solvent were mixed in a mass ratio of 6:2:3:0.5:0.8:5, and stirred for 20 minutes to obtain a flux;

[0047] The activator is composed of itaconic acid, diphenylguanidine, and triethanolamine in a mass ratio of 1:2:0.3;

[0048] S3, preparation of solder bars;

[0049] The materials were weighed according to 5% bismuth, 2.4% silver, 0.3% indium, 0.07% cerium, 0.08% germanium and the balance tin. The materials were then heated and melted in sequence according to the melting points of the materials in the tin alloy. When all the substances were melted into liquid, functional fillers and flux were added under a nitrogen atmosphere. Ultrasonic stirring was performed at 300W for 30 minutes. After that, impurities floating on the molten surface were removed, and the mixture was poured into a mold and cooled to form. At the same time, a 0.13T rotating magnetic field was applied at a speed of 50r / min. Solder bars were obtained after forming.

[0050] The proportion of each component in solder is 91.2% tin alloy, 5% functional filler and the balance flux;

[0051] The functional fillers are nano-GaN particles and nano-scale Cu@Ni core-shell structure particles, and the mass ratio of nano-GaN particles and Cu@Ni core-shell structure particles is 1:12.

[0052] Example 3, a process for preparing a solder bar with a low melting point and high service life, see Figure 1 ,include:

[0053] S1. Preparation of synthetic resin;

[0054] 300 parts by weight of refined rosin, 152 parts by weight of glycidyl methacrylate, 2 parts by weight of potassium hydroxide and 0.9 parts by weight of p-hydroxyanisole were mixed, and the mixture was stirred under a nitrogen atmosphere and refluxed at a temperature of 82° C. until the acid value reached 5 mgKOH / g, thereby obtaining a synthetic resin;

[0055] S2. Preparation of flux;

[0056] Modified rosin, synthetic resin, activator, corrosion inhibitor, thixotropic agent and organic solvent were mixed in a mass ratio of 5:1:2:0.3:0.4:3, and stirred for 30 minutes to obtain a flux;

[0057] The activator is composed of itaconic acid, diphenylguanidine, and triethanolamine in a mass ratio of 1:2:0.2;

[0058] S3, preparation of solder bars;

[0059] The materials were weighed according to 3% bismuth, 1.8% silver, 0.2% indium, 0.05% cerium, 0.03% germanium and the balance tin. The materials were then heated and melted in sequence according to the melting points of the materials in the tin alloy. When all the substances were melted into liquid, functional fillers and flux were added under a nitrogen atmosphere. Ultrasonic stirring was performed at 500W for 40 minutes. After that, impurities floating on the molten surface were removed, and the mixture was poured into a mold and cooled to form. At the same time, a 0.15T rotating magnetic field was applied at a speed of 80r / min. Solder bars were obtained after forming.

[0060] The proportion of each component in solder is 90.3% tin alloy, 4% functional filler and the balance flux;

[0061] The functional fillers are nano-GaN particles and nano-scale Cu@Ni core-shell structure particles, and the mass ratio of nano-GaN particles and Cu@Ni core-shell structure particles is 1:10.

[0062] Comparative Example 1:

[0063] Compared with Example 1, the difference of Comparative Example 1 is that, in Comparative Example 1, the Cu@Ni core-shell structure particles in step S3 are replaced with GaN particles, and the remaining steps remain unchanged to prepare the solder bars, which is recorded as Comparative Example 1.

[0064] Comparative Example 2:

[0065] Compared with Example 1, the difference of Comparative Example 2 is that the GaN particles in step S3 are replaced with Cu@Ni core-shell structure particles, and the remaining steps remain unchanged to prepare the solder bars, which is recorded as Comparative Example 2.

[0066] Comparative Example 3:

[0067] Compared with Example 1, Comparative Example 3 is different in that the synthetic resin in Step S1 and Step S2 is removed in Comparative Example 3, and the solder bars are prepared with the remaining steps unchanged, which is recorded as Comparative Example 3.

[0068] Comparative Example 4:

[0069] Compared with Example 1, Comparative Example 4 is different in that the rotating magnetic field in step S3 is removed in Comparative Example 4, and the solder bars are prepared with the remaining steps unchanged, which is recorded as Comparative Example 4.

[0070] The solder bars of Examples 1-3 and Comparative Examples 1-2 and 4 were welded, and the shear strength of the joints was measured at room temperature (27° C.) and 250° C. The measurement results are shown in Table 1.

[0071] Table 1. Determination of shear strength:

[0072] ;

[0073] It can be seen from the data in Table 1 that the data of Comparative Examples 1-2 are significantly lower than those of the embodiment, indicating that the addition of nano-GaN particles and nano-scale Cu@Ni core-shell structure particles can significantly improve the shear strength at high temperatures, improve the stability of the solder joints in high-temperature working environments, and achieve high-temperature service effects. It can be seen from the data in Comparative Example 4 that applying a rotating magnetic field can also improve the shear strength, because applying a rotating magnetic field can make the functional fillers evenly distributed, thereby facilitating the improvement of the shear strength at room temperature and high temperature.

[0074] The elongation and expansion ratios of Examples 1-3 and Comparative Example 3 were measured, and the measurement results are shown in Table 2. A greater elongation indicates better wettability of the solder bar; a greater expansion ratio indicates better solderability of the solder bar.

[0075] Table 2. Elongation and expansion rate measurement results:

[0076] ;

[0077] From the data in Table 2, it can be seen that adding the prepared synthetic resin into the flux can promote the spreading of solder on the metal surface and improve the wettability.

[0078] The welding melting point of Examples 1-3 was measured. The measurement results are shown in Table 3.

[0079] Table 3. Solder melting point determination results:

[0080] ;

[0081] It can be seen from the data in Table 3 that the solder bar prepared by the present invention can achieve welding at a relatively low temperature.

[0082] It should be understood that those skilled in the art may make improvements or modifications based on the above description, and all such improvements and modifications shall fall within the scope of protection of the appended claims. Any portion of this specification not described in detail is prior art known to those skilled in the art.

Claims

1. A solder bar with low melting point and high temperature service, characterized in that: Calculated by weight percentage, it comprises: 90.3-91.2% of tin alloy, 4-5% of functional filler and the balance of flux; The tin alloy is 3-5% bismuth, 1.8-2.4% silver, 0.2-0.3% indium, 0.05-0.07% cerium, 0.03-0.08% germanium and the balance tin; The functional fillers are nano-GaN particles and nano-scale Cu@Ni core-shell structure particles, and the mass ratio of nano-GaN particles to Cu@Ni core-shell structure particles is 1:10-12; The flux is composed of modified rosin, activator, corrosion inhibitor, synthetic resin, thixotropic agent and organic solvent in a mass ratio of 5-6:1-2:2-3:0.3-0.5:0.4-0.8:3-5; Synthetic resin is a rosin resin prepared from refined rosin and glycidyl methacrylate via epoxy ring-opening reaction.

2. The low-melting-point, high-temperature-service solder bar according to claim 1, characterized in that: The activator is composed of itaconic acid, diphenylguanidine and triethanolamine in a mass ratio of 1:2:0.2-0.

3.

3. The low-melting-point, high-temperature-service solder bar according to claim 1, characterized in that: The modified rosin is one or more of maleic rosin, hydrogenated rosin and acrylic rosin.

4. The low-melting-point, high-temperature-service solder bar according to claim 1, characterized in that: The corrosion inhibitor is one or more of benzothiazole, benzotriazole and benzimidazole.

5. The low-melting-point, high-temperature-service solder bar according to claim 1, characterized in that: The thixotropic agent is one or more of fatty acid amide, stearyl wax and hydrogenated castor oil.

6. The low-melting-point, high-temperature-service solder bar according to claim 1, characterized in that: The organic solvent is one or more of ethylene glycol phenyl ether and diethanol monobutyl ether.

7. A process for preparing the low-melting-point, high-temperature-service solder bar according to any one of claims 1 to 6, characterized in that: The specific steps for preparing solder bars include: S1. Preparation of synthetic resin; 300-320 parts by weight of refined rosin, 152-155 parts by weight of glycidyl methacrylate, 2-3 parts by weight of potassium hydroxide and 0.9-1 part by weight of p-hydroxyanisole are mixed, and the mixture is stirred under a nitrogen atmosphere while being refluxed at a temperature of 80-82° C. until the acid value reaches 2-5 mgKOH / g, thereby obtaining a synthetic resin; S2. Preparation of flux; The modified rosin, synthetic resin, activator, corrosion inhibitor, thixotropic agent and organic solvent are mixed in the above mass ratio and stirred for 20-30 minutes to obtain a soldering flux; S3, preparation of solder bars; The components of the tin alloy are heated and melted in sequence according to the melting points of each material. When all substances are melted into liquid, functional fillers and flux are added under a nitrogen atmosphere. Ultrasonic stirring is performed at 300-500W for 30-40 minutes. After that, impurities floating on the molten surface are removed, and the mixture is poured into a mold and cooled to form a solder bar.

8. The process for preparing a low-melting-point, high-temperature-service solder bar according to claim 7, characterized in that: During the pouring and cooling process in step S3, a rotating magnetic field of 0.13-0.15 T is applied at a rotation speed of 50-80 r / min.

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