Needle tube extrusion solder paste capable of achieving instant welding and preparation method

Abstract

The invention relates to the technical field of welding solder paste, and discloses needle tube extrusion solder paste capable of achieving instant welding and a preparation method thereof.The preparation method comprises the steps that compound rosin, an organic solvent, a corrosion inhibitor and imidazoline polyamide are heated to prepare a matrix; heating and dissolving an organic acid active agent, an alcohol solvent, an organic halide, an imidazole additive and liquid rubber, and mixing with the matrix to obtain paste flux; and finally, the flux paste and tin powder are mixed to prepare the needle tube extrusion solder paste capable of achieving instant welding. The imidazoline polyamide provides excellent thixotropy through a three-dimensional hydrogen bond network, and imidazoline heterocyclic rings of the imidazoline polyamide form a protective layer on a welding interface to improve corrosion inhibition. The imidazole auxiliary agent and the organic halide form a catalytic system to enhance the welding activity, liquid rubber crosslinking film formation guarantees high insulativity, and a buffer system formed by the alcohol solvent and the organic acid guarantees the storage stability. The multi-component function cooperation mechanism finally achieves optimal balance in the aspects of rheological properties, welding performance, corrosion protection and reliability.

Description

Technical Field

[0001] This invention relates to the field of solder paste technology, specifically to a needle-extruded solder paste capable of instant soldering and its preparation method. Background Technology

[0002] Solder paste, as a key electronic packaging material in surface mount technology, directly affects soldering quality and the reliability of the final product. In recent years, with the miniaturization and high-density development of electronic products, needle-extruded solder paste has attracted much attention due to its suitability for processes such as precision dispensing and soldering of irregularly shaped components. However, traditional needle-extruded solder paste still faces many challenges in achieving high soldering performance, long-term reliability, and excellent processability. The core issues lie in the performance limitations of the base materials and the lack of effective synergistic mechanisms among the components.

[0003] In the construction of soldering flux systems, compounded rosin serves as a film-forming agent and carrier, and its acid value, softening point, and thermal stability are crucial. Single rosin is insufficient to balance adhesion, soldering activity, and residual insulation. Therefore, compounded rosin is usually required, which involves combining different types of rosin (such as polymerized rosin and hydrogenated rosin) to adjust the overall performance and provide a stable and appropriately active matrix for solder paste.

[0004] Thixotropic agents and corrosion inhibitors are crucial for the printability and reliability of solder paste. Traditional polyamide thixotropic agents only provide physical thixotropy, while corrosion inhibition relies on additional corrosion inhibitors (such as benzotriazoles). This physical mixing can lead to poor compatibility or uneven functionality. A more significant issue is that post-soldering insulation reliability requires components like liquid rubber to cross-link and form a tough, dense protective film on the solder joint surface. This effectively blocks moisture and ion contamination from the environment, ensuring high surface insulation resistance over the long term. However, the compatibility of liquid rubber with traditional soldering flux systems and the uniformity of film formation present significant technical challenges.

[0005] The combination of organic acid surfactants is the core of removing oxides from metal surfaces, but excessive acidity or uncontrolled activity can exacerbate corrosion and affect storage stability. In this system, alcohol organic solvents not only serve as a dissolving medium, but also play a key role in regulating the polarity and viscosity of the system and forming a buffer system with organic acids to maintain the necessary balance between welding activity and storage stability.

[0006] The combination of imidazole additives and organohalides has been shown to produce a synergistic catalytic effect, significantly reducing the surface tension of the solder and promoting wetting and spreading. The activation efficiency and stability of this system also depend on the overall flux environment. Summary of the Invention

[0007] (a) Technical problems to be solved: To address the shortcomings of existing technologies, this invention provides a needle-extruded solder paste that can be instantly soldered and its preparation method, which solves the problems of solder beads and solder splattering that occur during instant soldering of traditional solder paste, as well as the problem of low surface insulation resistance of traditional instant soldering solder paste.

[0008] (II) Technical Solution: A method for preparing a needle-extruded solder paste that can be instantly soldered, the needle-extruded solder paste comprising 30-43 parts of compound rosin, 0.5-2 parts of corrosion inhibitor, 0.4-5 parts of antioxidant BHT, 4-8 parts of imidazoline polyamide, 3-6 parts of compound activator, 0.5-4 parts of imidazole additive, 25-40 parts of compound organic solvent, 0.4-2 parts of organic halide, 3-10 parts of liquid rubber, and 780-920 parts of solder powder.

[0009] The preparation method of instant solderable syringe extrusion solder paste is as follows: Step (1): Mix the imidazoline dicarboxylic acid compound, diamine, and antioxidant 1096 evenly, add them to a high-pressure reactor, seal with water, replace with N2, heat to 100-230℃, maintain the pressure at 1.5-2MPa, stir and react for 1-2 hours, then heat to 250-260℃, stir and react at normal pressure for 1-2 hours, and dry to obtain imidazoline polyamide.

[0010] Step (2): Add the compounded rosin and compounded organic solvent to container A, heat to 160-170℃, and stir to dissolve completely; then add the corrosion inhibitor and imidazoline polyamide in sequence, heat to 150-170℃, stir to dissolve completely, and cool to 120-130℃.

[0011] Step (3): Add a compound of organic acid activator, alcohol organic solvent, organic halide, imidazole additive, antioxidant BHT and liquid rubber to container B, heat to 120-135℃, stir to completely dissolve, add to container A of S1, stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste.

[0012] Step (4): Mix the flux and solder powder, and stir at 20-30 rpm for 20-30 minutes to obtain a syringe extrusion solder paste that can be instantly soldered.

[0013] Furthermore, in step (1), the diamine is one or more of the following: ethylenediamine, propylenediamine, butanediamine, pentanediamine, and hexanediamine.

[0014] Furthermore, in step (1), the ratio of imidazoline dioic acid compound, diamine, and antioxidant 1096 is 50g:(10-15)g:(0.4-0.6)g.

[0015] Furthermore, compound rosin is composed of crystalline rosin and non-crystalline rosin, and the ratio of crystalline rosin to non-crystalline rosin is generally (1-1.5) g: 1 g.

[0016] Furthermore, the imidazole adjuvant is composed of one or more of the following: 2-undecylimidazolium, 2-heptadecylimidazolium, 2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 2-phenylimidazolium, 2-phenyl-4-methylimidazolium, 1-benzyl-2-methylimidazolium, 1-benzyl-2-phenylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium, and 1-cyanoethyl-2-ethyl-4-methylimidazolium.

[0017] Furthermore, the compound surfactant is composed of one or more of the following: adipic acid, azelaic acid, eicosanoic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diethylene glycol, pyridine dicarboxylic acid, dibutylaniline diethylene glycol, pyridine carboxylic acid, octanoic acid, sebacic acid, thioglycolic acid, terephthalic acid, dodecanoic acid, p-hydroxyphenylacetic acid, pyridine carboxylic acid, phenyl succinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris(2-carboxyethyl)isocyanurate, glycine, 1,3-cyclohexanedicarboxylic acid, and 2,2-bis(hydroxymethyl)propionic acid.

[0018] Furthermore, the organohalides are composed of one or more of the following: diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, isopropylamine hydrobromide, cyclohexylamine hydrobromide, diethylamine hydrobromide, monoethylamine hydrobromide, 1,3-diphenylguanidine hydrobromide, dimethylamine hydrobromide, dimethylamine hydrobromide, rosinamine hydrobromide, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, chlorobrines, chlorobrines anhydride, o-iodobenzoic acid, m-iodobenzoic acid, and p-iodobenzoic acid.

[0019] Furthermore, alcohol ether organic solvents are compounded from one or more of the following: ether organic solvents include diethylene glycol hexyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dibutyl ether, and tripropylene glycol butyl ether; alcohol organic solvents include 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,3-dimethyl-2,3-butanediol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, terpineol, diethylene glycol, and triethylene glycol.

[0020] Furthermore, the corrosion inhibitor is one or more of the following: 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, phthalic acid dihydrazide, adipic acid dihydrazide, and piperazine corrosion inhibitors.

[0021] (III) Beneficial technical effects: This invention prepares a zoline polyamide with both thixotropic and corrosion-inhibiting properties by polymerizing imidazoline dicarboxylic acid compounds and diamines. The polyamide backbone provides a stable three-dimensional hydrogen bond network, endowing the system with excellent thixotropic properties, achieving the high shear thinning behavior and good shape retention required for needle extrusion. At the same time, the imidazoline heterocycles embedded in its molecular structure act as highly efficient metal coordinating groups, forming a dense protective layer at the welding interface, significantly improving the corrosion inhibition performance of the system.

[0022] The instant-solderable syringe-extruded solder paste of this invention exhibits excellent extrusion performance, solder ball formation, and copper plate corrosion results. This is due to the thixotropic and corrosion-inhibiting properties of the zocloline polyamide, and the catalytic activation system composed of imidazole additives and organic halides, which synergistically deoxidizes at the solder interface, significantly reducing solder surface tension and ensuring excellent wetting and spreading properties. The instant-solderable syringe-extruded solder paste of this invention also has a high surface insulation resistance, exhibiting excellent surface insulation. This is because the liquid rubber forms a continuous and dense protective layer on the solder joint surface through a cross-linking film-forming mechanism, effectively blocking environmental corrosion and ensuring high insulation reliability. Furthermore, the buffer system formed by the alcohol solvent and the compounded organic acid activator maintains necessary soldering activity while ensuring storage stability. This multi-component synergistic mechanism ultimately enables the instant-solderable syringe-extruded solder paste of this invention to achieve an optimal balance in key indicators such as rheological properties, soldering performance, corrosion protection, and long-term reliability. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them.

[0024] Imidazolinic acid compounds were prepared according to the method described in the journal Applied Chemical Industry, 2016, 45(07):1328-1331+1335, "Study on the Corrosion Inhibition Performance of Carboxylated Imidazolin on A3 Steel in Oilfield Wastewater".

[0025] Example 1: Step (1): Mix 10 kg of imidazoline dicarboxylic acid compound, 2 kg of hexamethylenediamine, and 0.10 kg of antioxidant 1096 evenly, add them to a high-pressure reactor, seal with water, replace with N2, heat to 180°C, maintain the pressure at 1.75 MPa, stir and react for 1 h, then heat to 260°C, stir and react at normal pressure for 2 h, and dry to obtain imidazoline polyamide.

[0026] Step (2): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 5L of diethylene glycol dibutyl ether, and 20L of tetraethylene glycol dimethyl ether to container A, heat to 160℃, and stir to completely dissolve; then add 0.5kg of carboxybenzotriazole and 7kg of imidazoline polyamide in sequence, heat to 170℃, stir to completely dissolve, and cool to 120℃.

[0027] Step (3): Add 0.5 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 3 kg adipic acid, 10 L 2-ethyl-1,3-hexanediol, 0.5 kg o-iodobenzoic acid, 1.5 kg 2-undecylimidazolium, and 5 L liquid rubber to container B, heat to 135°C, stir to completely dissolve, and then add to container A from step (2). Stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux.

[0028] Step (4): Mix the flux and solder powder and stir at 25 rpm for 25 minutes to obtain a syringe extrusion solder paste that can be instantly soldered.

[0029] Example 2: Step (1): Mix 10 kg of imidazoline dicarboxylic acid compound, 3 kg of butanediamine, and 0.08 kg of antioxidant 1096 evenly, add them to a high-pressure reactor, seal with water, replace with N2, heat to 220°C, maintain the pressure at 1.5 MPa, stir and react for 2 h, then heat to 250°C, stir and react at normal pressure for 1 h, and dry to obtain imidazoline polyamide.

[0030] Step (2): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 5L of diethylene glycol dibutyl ether, and 20L of tetraethylene glycol dimethyl ether to container A, heat to 165℃, and stir to completely dissolve; then add 0.5kg of carboxybenzotriazole and 7kg of imidazoline polyamide in sequence, heat to 150℃, stir to completely dissolve, and cool to 130℃.

[0031] Step (3): Add 0.5 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 3 kg adipic acid, 10 L 2-ethyl-1,3-hexanediol, 0.5 kg o-iodobenzoic acid, 1.5 kg 2-undecylimidazolium, and 5 L liquid rubber to container B, heat to 120°C, stir to completely dissolve, add to container A from step (2), stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste.

[0032] Step (4): Mix the flux and solder powder and stir at 20 rpm for 30 minutes to obtain a syringe extrusion solder paste that can be instantly soldered.

[0033] Example 3: Step (1): Mix 10 kg of imidazoline dicarboxylic acid compound, 2 kg of propylene diamine and 0.12 kg of antioxidant 1096 evenly, add to a high-pressure reactor, seal with water, replace with N2, heat to 230°C, maintain pressure at 2 MPa, stir and react for 1 h, then heat to 250°C, stir and react at normal pressure for 2 h, dry to obtain imidazoline polyamide.

[0034] Step (2): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 5L of diethylene glycol dibutyl ether, and 20L of tetraethylene glycol dimethyl ether to container A, heat to 170℃, and stir to dissolve completely; then add 0.5kg of carboxybenzotriazole and 7kg of imidazoline polyamide in sequence, heat to 160℃, stir to dissolve completely, and cool to 120℃.

[0035] Step (3): Add 0.5 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 3 kg adipic acid, 10 L 2-ethyl-1,3-hexanediol, 0.5 kg o-iodobenzoic acid, 1.5 kg 2-undecylimidazolium, and 5 L liquid rubber to container B, heat to 130°C, stir to completely dissolve, and then add to container A from step (2). Stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste.

[0036] Step (4): Mix the flux and solder powder and stir at 30 rpm for 20 minutes to obtain a syringe extrusion solder paste that can be instantly soldered.

[0037] Example 4: Step (1): Mix 10 kg of imidazoline dicarboxylic acid compound, 3 kg of pentanediamine and 0.10 kg of antioxidant 1096 evenly, add to a high-pressure reactor, seal with water, replace with N2, heat to 100°C, maintain pressure at 2 MPa, stir and react for 1 h, then heat to 260°C, stir and react at normal pressure for 2 h, dry to obtain imidazoline polyamide.

[0038] Step (2): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 5L of diethylene glycol dibutyl ether, and 20L of tetraethylene glycol dimethyl ether to container A, heat to 160℃, and stir to completely dissolve; then add 0.5kg of carboxybenzotriazole and 7kg of imidazoline polyamide in sequence, heat to 170℃, stir to completely dissolve, and cool to 120℃.

[0039] Step (3): Add 0.5 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 3 kg adipic acid, 10 L 2-ethyl-1,3-hexanediol, 0.5 kg o-iodobenzoic acid, 1.5 kg 2-undecylimidazolium, and 5 L liquid rubber to container B, heat to 130°C, stir to completely dissolve, and then add to container A from step (2). Stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste.

[0040] Step (4): Mix the flux and solder powder and stir at 25 rpm for 20 minutes to obtain a syringe extrusion solder paste that can be instantly soldered.

[0041] Comparative Example 1: The main difference from Example 1 is that no organic halide was added.

[0042] Step (1): Mix 10 kg of imidazoline dicarboxylic acid compound, 2 kg of hexamethylenediamine, and 0.10 kg of antioxidant 1096 evenly, add them to a high-pressure reactor, seal with water, replace with N2, heat to 180°C, maintain the pressure at 1.75 MPa, stir and react for 1 h, then heat to 260°C, stir and react at normal pressure for 2 h, and dry to obtain imidazoline polyamide.

[0043] Step (2): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 5L of diethylene glycol dibutyl ether, and 19.7L of tetraethylene glycol dimethyl ether to container A, heat to 160℃, and stir to dissolve completely; then add 0.8kg of carboxybenzotriazole and 7kg of imidazoline polyamide in sequence, heat to 170℃, stir to dissolve completely, and cool to 120℃.

[0044] Step (3): Add 0.5 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 4 kg adipic acid, 10 L 2-ethyl-1,3-hexanediol, 1 kg 2-undecylimidazol, and 5 L liquid rubber to container B, heat to 135°C, stir to completely dissolve, add to container A from step (2), stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste.

[0045] Step (4): Mix the flux and solder powder and stir at 25 rpm for 25 minutes to obtain solder paste.

[0046] Comparative Example 2: The main difference from Example 1 is that no imidazole adjuvants were added.

[0047] Step (1): Mix 10 kg of imidazoline dicarboxylic acid compound, 2 kg of hexamethylenediamine, and 0.10 kg of antioxidant 1096 evenly, add them to a high-pressure reactor, seal with water, replace with N2, heat to 180°C, maintain the pressure at 1.75 MPa, stir and react for 1 h, then heat to 260°C, stir and react at normal pressure for 2 h, and dry to obtain imidazoline polyamide.

[0048] Step (2): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 5L of diethylene glycol dibutyl ether, and 19.9L of tetraethylene glycol dimethyl ether to container A, heat to 160℃, and stir to dissolve completely; then add 0.5kg of carboxybenzotriazole and 7kg of imidazoline polyamide in sequence, heat to 170℃, stir to dissolve completely, and cool to 120℃.

[0049] Step (3): Add 0.8 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 3 kg adipic acid, 10 L 2-ethyl-1,3-hexanediol, 0.8 kg o-iodobenzoic acid, and 5 L liquid rubber to container B, heat to 135°C, stir to completely dissolve, and then add to container A from step (2), stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste.

[0050] Step (4): Mix the flux and solder powder and stir at 25 rpm for 25 minutes to obtain solder paste.

[0051] Comparative Example 3: The main difference from Example 1 is that no alcoholic organic solvents are added.

[0052] Step (1): Mix 10 kg of imidazoline dicarboxylic acid compound, 2 kg of hexamethylenediamine, and 0.10 kg of antioxidant 1096 evenly, add them to a high-pressure reactor, seal with water, replace with N2, heat to 180°C, maintain the pressure at 1.75 MPa, stir and react for 1 h, then heat to 260°C, stir and react at normal pressure for 2 h, and dry to obtain imidazoline polyamide.

[0053] Step (2): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 5L of diethylene glycol dibutyl ether, and 28.9L of tetraethylene glycol dimethyl ether to container A, heat to 160℃, and stir to dissolve completely; then add 0.5kg of carboxybenzotriazole and 7kg of imidazoline polyamide in sequence, heat to 170℃, stir to dissolve completely, and cool to 120℃.

[0054] Step (3): Add 0.8 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 3 kg adipic acid, 0.8 kg o-iodobenzoic acid, 1 kg 2-undecylimidazolium, and 5 L liquid rubber to container B, heat to 135°C, stir to completely dissolve, add to container A from step (2), stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste.

[0055] Step (4): Mix the flux and solder powder and stir at 25 rpm for 25 minutes to obtain solder paste.

[0056] Comparative Example 4: The main difference from Example 1 is that no liquid rubber was added.

[0057] Step (1): Mix 10 kg of imidazoline dicarboxylic acid compound, 2 kg of hexamethylenediamine, and 0.10 kg of antioxidant 1096 evenly, add them to a high-pressure reactor, seal with water, replace with N2, heat to 180°C, maintain the pressure at 1.75 MPa, stir and react for 1 h, then heat to 260°C, stir and react at normal pressure for 2 h, and dry to obtain imidazoline polyamide.

[0058] Step (2): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 10L of diethylene glycol dibutyl ether, and 18.9L of tetraethylene glycol dimethyl ether to container A, heat to 160℃, and stir to dissolve completely; then add 0.5kg of carboxybenzotriazole and 7kg of imidazoline polyamide in sequence, heat to 170℃, stir to dissolve completely, and cool to 120℃.

[0059] Step (3): Add 0.8 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 3 kg adipic acid, 10 L 2-ethyl-1,3-hexanediol, 0.8 kg o-iodobenzoic acid, and 1 kg 2-undecylimidazol to container B, heat to 135°C, stir to completely dissolve, add to container A from step (2), stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste.

[0060] Step (4): Mix the flux and solder powder and stir at 25 rpm for 25 minutes to obtain solder paste.

[0061] Comparative Example 5: The main difference from Example 1 is that imidazoline polyamide is not added.

[0062] Step (1): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 5L of diethylene glycol dibutyl ether, and 20L of tetraethylene glycol dimethyl ether to container A, heat to 160℃, and stir to dissolve completely; then add 0.5kg of carboxybenzotriazole, heat to 170℃, stir to dissolve completely, and cool to 120℃.

[0063] Step (2): Add 0.5 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 3 kg adipic acid, 10 L 2-ethyl-1,3-hexanediol, 0.5 kg o-iodobenzoic acid, 1.5 kg 2-undecylimidazolium, and 5 L liquid rubber to container B, heat to 135°C, stir to completely dissolve, and then add to container A from step (1), stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste.

[0064] Step (3): Mix the flux and solder powder and stir at 25 rpm for 25 minutes to obtain solder paste.

[0065] Comparative Example 6: The main difference from Example 1 is that succinic acid was used instead of imidazoline diic acid to prepare polyamide.

[0066] Step (1): Mix 10 kg succinic acid, 2 kg hexamethylenediamine and 0.10 kg antioxidant 1096 evenly, add to a high-pressure reactor, seal with water, replace with N2, heat to 180℃, maintain pressure at 1.75 MPa, stir and react for 1 h, then heat to 260℃, stir and react at normal pressure for 2 h, dry to obtain polyamide.

[0067] Step (2): Add 18kg of KE-604 non-crystalline rosin, 22kg of KR-616 crystalline rosin, 5L of diethylene glycol dibutyl ether, and 20L of tetraethylene glycol dimethyl ether to container A, heat to 160℃, and stir to completely dissolve; then add 0.5kg of carboxybenzotriazole and 7kg of polyamide in sequence, heat to 170℃, stir to completely dissolve, and cool to 120℃.

[0068] Step (3): Add 0.5 kg pyridine carboxylic acid, 3 kg 2,2-bis(hydroxymethyl)propionic acid, 3 kg BHT, 1 kg diethylene glycol, 3 kg adipic acid, 10 L 2-ethyl-1,3-hexanediol, 0.5 kg o-iodobenzoic acid, 1.5 kg 2-undecylimidazolium, and 5 L liquid rubber to container B, heat to 135°C, stir to completely dissolve, and then add to container A from step (2). Stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux.

[0069] Step (4): Mix the flux and solder powder and stir at 25 rpm for 25 minutes to obtain solder paste.

[0070] A syringe dotting test was used to evaluate the uniformity of the dotting amount at different time points: the amount of solder dispensed in the early, middle, and late stages of the syringe was compared. A: Completely extruded, uniform speed; B: Completely extruded, uneven; C: Not completely extruded.

[0071] A constant-temperature soldering iron is used to solder a measured amount of solder paste onto a clean copper plate for 2 seconds. After cooling, the residue is cleaned off. The results are evaluated by observing the surface gloss, wetting and spreading shape of the solder joints, and the presence of defects such as pinholes and shrinkage cavities. A: Excellent; B: Acceptable; C: Poor, unacceptable.

[0072] Using a temperature-controlled soldering iron, apply a measured amount of solder paste to a clean copper plate and solder for 2 seconds. After soldering, without moving the plate, immediately check the area around the solder joint (especially the heat-affected zone) for any solder balls. Evaluate the results by counting the number and size of the solder balls: A: Excellent; B: Acceptable; C: Poor, Unacceptable.

[0073] Referring to the IPC-TM-650 test method manual, the prepared solder paste was placed on the test copper plate according to the experimental requirements. After reflow soldering, the test sample was placed in a constant temperature and humidity environment of 40±1℃ and 93±2% for copper plate corrosion testing. The corrosion status and appearance color change of the copper plate were observed and recorded after 240 hours. L: No corrosion; M: Slight corrosion; H: Severe corrosion.

[0074] Referring to the relevant provisions of standard SJ / T 11389-2009 "Fluents for Lead-Free Soldering", the comb-shaped circuit board was cleaned with deionized water and anhydrous ethanol respectively, placed in a 90℃ oven for 1 hour, and then removed to test the surface insulation resistance. The selected board had an SIR value of not less than 1×10⁻⁶. 12 The Ω-shaped comb-shaped circuit board was used as the test piece for the final test. Ten comb-shaped circuit board test pieces were selected as a group. Solder paste was evenly applied to five of the comb-shaped circuit board test pieces using the corresponding standard printing screen, and the other five test pieces served as blank control pieces. All test pieces were placed in an oven at 300℃ for 30 seconds, removed and cooled, and then placed in an environment at 40℃ and 85% relative humidity to test the SIR value after 10 days of soldering.

[0075] Table 1 Performance Tests of Solder Paste As shown in the table, the instant-solderable needle-extruded solder pastes prepared in Examples 1-4 exhibit excellent extrusion performance, solder ball formation, and copper plate corrosion results. This is mainly due to the stable three-dimensional hydrogen bond network provided by the polyamide skeleton of imidazoline polyamide, which endows the system with excellent thixotropic properties, achieving the high shear thinning behavior and good shape retention required for needle extrusion. Simultaneously, the imidazoline heterocycles embedded in its molecular structure act as highly efficient metal coordinating groups, forming a dense protective layer at the soldering interface, significantly improving the system's corrosion inhibition performance. Furthermore, the catalytic activation system composed of imidazoline additives and organic halides produces a synergistic deoxidation effect at the soldering interface, significantly reducing the surface tension of the solder and ensuring excellent wetting and spreading performance. The instant-solderable needle-extruded solder pastes of Examples 1-4 have a high surface insulation resistance and good surface insulation properties. This is because the liquid rubber forms a continuous and dense protective layer on the solder joint surface through a cross-linking film-forming mechanism, effectively blocking environmental corrosion and ensuring the product's high insulation reliability. In addition, the buffer system formed by the alcohol solvent and the compounded organic acid activator maintains the necessary welding activity while ensuring storage stability. This multi-component synergistic mechanism ultimately enables Examples 1-4 to achieve an optimal balance in key indicators such as rheological properties, welding performance, corrosion protection, and long-term reliability.

[0076] Comparative Example 1 is solder paste without organic halides, which disrupts the catalytic activation system composed of azole additives and organic halides. Without the synergistic effect of halogens, the deoxidation efficiency of the solder interface is greatly reduced, resulting in deterioration of solder wettability, increase of solder residue, and the generation of solder balls.

[0077] Comparative Example 2 is solder paste without imidazole additives. It lacks the imidazole-halogen synergistic activation mechanism, which leads to a decrease in soldering performance. It also loses the corrosion inhibition and auxiliary function of imidazole substances themselves, resulting in a simultaneous deterioration of soldering effect and corrosion resistance.

[0078] Comparative Example 3 is solder paste without alcohol-based organic solvents. The absence of alcohol-based solvents disrupts the acid-base buffer system, leading to uncontrolled activity of organic acids. The overly aggressive acidic environment also exacerbates the corrosion tendency of the copper plate.

[0079] Comparative Example 4 is solder paste without liquid rubber. Due to the cross-linking film protection of liquid rubber, a dense insulating layer cannot be formed on the surface of the solder joint. Moisture and pollutants in the environment directly corrode the solder joint, resulting in a significant reduction in surface insulation resistance and making it difficult to guarantee long-term reliability.

[0080] Comparative Example 5 is the solder paste without imidazoline polyamide. Due to the absence of imidazoline polyamide, the system lacks a stable three-dimensional hydrogen bond network, leading to deteriorated thixotropic properties and uncontrolled extrusion morphology. Furthermore, the lack of metal coordination protection from the imidazoline heterocycle results in the failure of the corrosion protection mechanism at the solder interface, leading to severe copper corrosion.

[0081] Comparative Example 6 uses succinic acid instead of imidazoline dicarboxylic acid to prepare polyamide. The resulting solder paste completely lacks the imidazoline heterocyclic structure, resulting in a decline in corrosion inhibition performance and the inability to form an effective protective layer on the metal surface.

[0082] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be considered as the content disclosed by the present invention.

Claims

1. A method for preparing a needle-extruded solder paste capable of instant soldering, characterized in that, The instant solderable needle-extruded solder paste comprises 30-43 parts of compound rosin, 0.5-2 parts of corrosion inhibitor, 0.4-5 parts of antioxidant BHT, 4-8 parts of imidazoline polyamide, 3-6 parts of compound activator, 0.5-4 parts of imidazolium auxiliaries, 25-40 parts of compound organic solvent, 0.4-2 parts of organic halide, 3-10 parts of liquid rubber, and 780-920 parts of solder powder. The preparation method of instant solderable syringe extrusion solder paste is as follows: S1. Add the compounded rosin and compounded organic solvent to container A, heat to 160-170℃, and stir to dissolve completely; then add the corrosion inhibitor and imidazoline polyamide in sequence, heat to 150-170℃, stir to dissolve completely, and cool to 120-130℃. S2. Add a compound of organic acid activator, alcohol organic solvent, organic halide, imidazole additive, antioxidant BHT, liquid rubber, antioxidant, and liquid rubber to container B, heat to 120-135℃, stir to completely dissolve, add to container A of S1, stir evenly, cool to room temperature, and let stand for 12 hours to obtain flux paste. S3. Mix the flux and solder powder, and stir at 20-30 rpm for 20-30 minutes to obtain a syringe extrusion solder paste that can be instantly soldered.

2. The method for preparing the instant-solderable needle-extruded solder paste according to claim 1, characterized in that, The compound rosin is composed of crystalline rosin and non-crystalline rosin, and the ratio of crystalline rosin to non-crystalline rosin is generally (1-1.5) g: 1 g.

3. The method for preparing the instant-solderable needle-extruded solder paste according to claim 1, characterized in that, The imidazole adjuvant is composed of one or more of the following: 2-undecylimidazolium, 2-heptadecylimidazolium, 2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 2-phenylimidazolium, 2-phenyl-4-methylimidazolium, 1-benzyl-2-methylimidazolium, 1-benzyl-2-phenylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium.

4. The method for preparing the instant-solderable needle-extruded solder paste according to claim 1, characterized in that, The compound activator is composed of one or more of the following: adipic acid, azelaic acid, eicosanoic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diethylene glycol, pyridine dicarboxylic acid, dibutylaniline diethylene glycol, pyridine carboxylic acid, octanoic acid, sebacic acid, thioglycolic acid, terephthalic acid, dodecanoic acid, p-hydroxyphenylacetic acid, pyridine carboxylic acid, phenyl succinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris(2-carboxyethyl)isocyanurate, glycine, 1,3-cyclohexanedicarboxylic acid, and 2,2-bis(hydroxymethyl)propionic acid.

5. The method for preparing the instant-solderable needle-extruded solder paste according to claim 1, characterized in that, The organohalides are composed of one or more of the following: diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, isopropylamine hydrobromide, cyclohexylamine hydrobromide, diethylamine hydrobromide, monoethylamine hydrobromide, 1,3-diphenylguanidine hydrobromide, dimethylamine hydrobromide, dimethylamine hydrobromide, rosinamine hydrobromide, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrobromide, chlorobridged acid, chlorobridged anhydride, o-iodobenzoic acid, m-iodobenzoic acid, and p-iodobenzoic acid.

6. The method for preparing the instant-solderable needle-extruded solder paste according to claim 1, characterized in that, The alcohol-ether organic solvents are formulated from one or more of the following: ether organic solvents include diethylene glycol hexyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dibutyl ether, and tripropylene glycol butyl ether; alcohol organic solvents include 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,3-dimethyl-2,3-butanediol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, terpineol, diethylene glycol, and triethylene glycol.

7. The method for preparing the instant-solderable needle-extruded solder paste according to claim 1, characterized in that, The corrosion inhibitor is one or more of the following: 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, phthalic acid dihydrazide, adipic acid dihydrazide, and piperazine corrosion inhibitors.

8. The method for preparing the instant-solderable needle-extruded solder paste according to claim 1, characterized in that, The preparation method of the imidazoline polyamide is as follows: the imidazoline dicarboxylic acid compound, diamine, and antioxidant 1096 are mixed evenly and added to a high-pressure reactor. The reactor is sealed with water, replaced with N2, heated to 100-230℃, and the pressure is maintained at 1.5-2MPa. The mixture is stirred and reacted for 1-2 hours, then heated to 250-260℃ and stirred and reacted at normal pressure for 1-2 hours. The mixture is then dried to obtain imidazoline polyamide.

9. The method for preparing the instant-solderable needle-extruded solder paste according to claim 8, characterized in that, The diamine is one or more of the following: ethylenediamine, propylenediamine, butanediamine, pentanediamine, and hexamethylenediamine.

10. The method for preparing the instant-solderable needle-extruded solder paste according to claim 8, characterized in that, The ratio of the imidazolinide compound, diamine, and antioxidant 1096 is 50g:(10-15)g:(0.4-0.6)g.

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