A phosphate-free tin-copper co-plating additive, a preparation method thereof, a tin-copper co-plating solution and application thereof

Abstract

This disclosure provides a pyrophosphate-free tin-copper co-plating additive, its preparation method, a tin-copper co-plating solution, and its application. The aforementioned tin-copper co-plating additive includes a primary complexing agent and an auxiliary complexing agent. The primary complexing agent is a modified branched polyamine polymer, which is generated by reacting a branched polyamine polymer with an oxazolyl carboxylic acid compound. The modified branched polyamine polymer contains amino ligands and nitrogen-oxygen mixed polydentate ligands. The auxiliary complexing agent is a cationic oligosaccharide complex. This tin-copper co-plating additive, with its amino ligands and nitrogen-oxygen mixed polydentate ligands in the modified branched polyamine polymer, can effectively regulate tin-copper co-plating, achieving a high tin, low copper deposition effect. This allows tin and copper to co-deposit at a uniform rate, effectively refining tin-copper grains, forming a tin-whisker-free, uniformly crystallized, flat, and dense tin-copper co-plating layer; it is also environmentally friendly.

Description

Technical Field

[0001] This disclosure relates to the technical field of electroplating, and in particular to a pyrophosphate-free tin-copper coplating additive, its preparation method, tin-copper coplating solution, and its application. Background Technology

[0002] With the rapid development of 5G communication, new energy vehicles, and power devices, traditional single tin or copper plating can no longer simultaneously meet the multiple requirements of "low contact resistance, high solderability, excellent corrosion resistance, and mechanical strength." Tin-copper alloy (Sn-Cu) combines the low melting point and solderability of tin with the high electrical conductivity, high thermal conductivity, and high hardness of copper, making it a novel surface coating material for high-end connectors, ICB modules, power battery earpieces, and PCB pads. Compared to pure tin, Sn-Cu alloy can inhibit tin whisker growth and reduce insertion and extraction forces; compared to pure copper, it avoids the decrease in solderability caused by copper oxidation.

[0003] For example, patent CN200710008731 discloses a tin-copper co-plating layer, a tin-copper co-plating solution formulation, and an electroplating method, which includes stannous chloride, copper pyrophosphate, and potassium pyrophosphate at concentrations of 250-350 g / L. While this avoids the toxicity of cyanide, the high concentration of pyrophosphate easily leads to excessive total phosphorus in the wastewater. Relying solely on stannous chloride pentahydrate as a plating solution stabilizer, due to the strong reducing properties of the divalent tin ions it contains, easily results in insufficient oxidative stability. This leads to decreased plating solution stability, uneven tin crystallization, and insufficient crystal density in the plating layer. Furthermore, it also causes the plating solution to become turbid and results in a short bath-changing cycle.

[0004] In response, some scholars have attempted to utilize the tin-copper co-plating solution technical solutions disclosed in patents CN102102218A and CN1570219A. These tin-copper co-plating solutions primarily use thiourea or its derivatives as the main complexing agent. While this improves performance over a wider current density range and provides antioxidant properties, addressing to some extent the insufficient oxidative stability of traditional solutions relying solely on tin chloride pentahydrate as a plating solution stabilizer, the thiourea groups in these solutions possess high reducing power. They are easily oxidized and decomposed by dissolved oxygen and high-valence metal ions in the solution. This results in problems such as rapid decomposition, high consumption, large fluctuations in tin-copper co-plating solution content, and high difficulty in control. Furthermore, uneven tin crystallization still leads to insufficient crystal density in the plating layer, resulting in the formation of tin whiskers. Moreover, thiourea or its derivatives are toxic to human health, and long-term exposure can cause significant harm. Summary of the Invention

[0005] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a method for incorporating modified branched polyamine polymers that has resistance to Cu 2+ The extremely high affinity ligands enable Cu 2+ The actual reduction potential shifts significantly negatively, Sn 2+ The reduction potential is less affected, achieving a high tin, low copper deposition effect; it effectively controls tin-copper co-plating, allowing tin and copper to be reduced stably and continuously at a suitable ratio, enabling tin and copper to co-deposit at a uniform rate. Simultaneously, with the synergistic effect of the cationic oligosaccharide complex, it effectively refines tin-copper grains to form a uniform, flat, and dense tin-copper co-plating layer; it also reduces the decomposition rate of the modified branched polyamine polymer, thus not increasing the overall consumption of the modified branched polyamine polymer; and it also realizes a green and environmentally friendly pyrophosphate-free tin-copper co-plating additive, its preparation method, tin-copper co-plating solution, and its application.

[0006] The purpose of this disclosure is achieved through the following technical solution: A pyrophosphate-free tin-copper co-plating additive, comprising a primary complexing agent and an auxiliary complexing agent, characterized in that the primary complexing agent is a modified branched polyamine polymer, which is generated by reacting a branched polyamine polymer with an oxazolylcarboxylic acid compound, and the modified branched polyamine polymer contains amino ligands and nitrogen-oxygen mixed polydentate ligands; the auxiliary complexing agent is a cationic oligosaccharide complex.

[0007] In one embodiment, the branched polyamine polymer comprises at least one of branched polyethyleneimine and branched polyamide; and / or, The molecular weight of the branched polyamine polymer is 600 Da-1000 Da.

[0008] In one embodiment, the oxazolylcarboxylic acid compound comprises at least one selected from 2,4-dimethyloxazol-5-carboxylic acid, 5-oxazolcarboxylic acid, 3-(5-oxazolyl)benzoic acid, and 3-isooxazolcarboxylic acid; and / or, The molar ratio of the branched polyamine polymer to the oxazolyl carboxylic acid compound is 1:(3-4).

[0009] In one embodiment, the cationic oligosaccharide complex includes at least two of oligosaccharide ligands, oligosaccharide ligand derivatives, and cationic surfactants.

[0010] In one embodiment, the oligosaccharide ligand has a molecular weight of 800 Da-1200 Da; and / or, The oligosaccharide ligand derivative has a molecular weight of 800 Da-1200 Da; and / or, The oligosaccharide ligand includes at least one selected from chitosan oligosaccharide, glucosamine oligosaccharide, galactosamine oligosaccharide, and mannosamine oligosaccharide; and / or, The oligosaccharide ligand derivative includes at least one of carboxymethyl oligochitosan, ethylene glycol oligochitosan, and oligogalactosamine; and / or, The cationic surfactant includes at least one of N-octadecyl-4-styrylpyridine bromide, 1-octadecyl-4-(4-phenyl-1,3-butadienyl)pyridine bromide, N-octylpyridine bromide, and 1,1'-di-n-octyl-4,4'-bidibromopyridine bromide.

[0011] A method for preparing a pyrophosphate-free tin-copper co-plating additive includes the following steps: A mixed solution is obtained by mixing a branched polyamine polymer, an oxazolyl carboxylic acid compound, and a polar aprotic solvent. A core condensing agent, a condensing aid, and an acid neutralizer are added to the mixed solution to carry out an amidation condensation reaction, thereby obtaining a modified branched polyamine polymer precursor. The modified branched polyamine polymer precursor was separated and purified to obtain the modified branched polyamine polymer.

[0012] In one embodiment, the polar aprotic solvent includes at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, and dimethyl sulfoxide; and / or, The core condensing agent includes at least one of EDC·HCl, DDC, and DIC; and / or, The condensation aid includes at least one of HOAt, HOBt, OXyma Pure, and OXyma-B; and / or, The acid neutralizing agent includes at least one of triethylamine, N,N-diisopropylethylamine, N-methylmorpholine, and pyridine.

[0013] In one embodiment, the step of adding a core condensing agent, a condensing aid, and an acid neutralizing agent to the mixed solution to carry out an amidation condensation reaction includes the following specific steps: Under a nitrogen atmosphere and at room temperature, the mixture is added dropwise to a container, followed by the sequential addition of the core condensing agent, the condensation aid, and the acid neutralizing agent, and the reaction is continuously stirred for 12-20 hours; and / or, The step of separating and purifying the modified branched polyamine polymer precursor to obtain the modified branched polyamine polymer includes the following specific steps: The modified branched polyamine polymer precursor was added to a precipitant and then filtered to obtain a precipitate. The precipitate was subjected to precipitation washing and drying operations in sequence.

[0014] In one embodiment, the components, in terms of mass concentration, include the following: Stannous salts: 20 g / L - 60 g / L; Copper salt concentration: 1.5 g / L - 2.7 g / L; Main complexing agent 20g / L-40g / L; Auxiliary complexing agent 3.1g / L-10g / L; Brightening agent: 0.1g / L-2.0g / L; Antioxidant concentration: 8g / L-15g / L; Organic acids 120g / L-180g / L; Water balance; The main complexing agent is a modified branched polyamine polymer; The auxiliary complexing agent is a cationic oligosaccharide complex; The primary complexing agent and the secondary complexing agent constitute the pyrophosphate-free tin-copper co-plating additive described in any of the above embodiments.

[0015] An application of the tin-copper co-plating solution described in any of the above embodiments in a plated part.

[0016] Compared with the prior art, this disclosure has at least the following advantages: 1) Since the main complexing agent is a modified branched polyamine polymer, which is generated by reacting a branched polyamine polymer with an oxazolylcarboxylic acid compound, the amino group of the branched polyamine polymer and the carboxyl group of the oxazolylcarboxylic acid compound undergo dehydration to form an amide bond, i.e., an amidation condensation reaction. This allows the oxazolylcarboxylic acid compound to be grafted onto the modified branched polyamine polymer, ensuring that the final modified branched polyamine polymer contains amino ligands and nitrogen-oxygen mixed polydentate ligands. The amino ligands mainly form stable five- or six-membered chelate ring structures with copper ions through the lone pair electrons on the nitrogen atom, selectively inhibiting the preferential deposition of copper ions. This mechanism significantly increases the copper deposition overpotential and significantly reduces the reduction rate of copper ions at the cathode, thus ensuring that the modified branched polyamine polymer has the ability to react with Cu. 2+ The extremely high affinity ligands enable Cu 2+ The actual reduction potential shifts significantly negatively, Sn 2+The reduction potential is less affected, achieving a high tin, low copper deposition effect. Furthermore, because the nitrogen-oxygen mixed multidentate ligand preferentially combines with copper ions in the tin-copper co-plating solution to form a stable complex, the copper concentration is further reduced, thus ensuring the high tin, low copper deposition effect and effectively avoiding large fluctuations in the tin-copper co-plating solution content, thereby reducing the difficulty of controlling the tin-copper co-plating solution. In other words, by regulating the tin-copper co-plating, tin and copper can be reduced stably and continuously at a suitable ratio, allowing for uniform co-deposition. This results in preferential adsorption near the cathode to microscopic protrusions or areas with high current density, forming a uniform, flat, and dense tin-copper co-plating layer. This effectively inhibits tin whisker growth, ensuring the formed tin-copper co-plating layer possesses excellent density, solderability, and corrosion resistance, meeting the stringent requirements of precision electronic components for highly stable tin-copper co-plating layers. In addition, this additive system completely eliminates pyrophosphate, avoiding the problems of phosphorus-containing wastewater treatment, and combines the advantages of being green, environmentally friendly, efficient, and producing excellent coating quality, making it better suited for the rapid development of the electroplating field.

[0017] Because the amide bonds formed by the reaction of the modified branched polyamine polymer with the oxazolyl carboxylic acid compound have good stability and are not easily oxidized and decomposed, the decomposition rate of the modified branched polyamine polymer is reduced; and the modified branched polyamine polymer is formed by the reaction of amino ligands and nitrogen-oxygen mixed polydentate ligands with metal ions (such as Cu). 2+ Sn 2+ The coordination complexation reaction that occurs does not destroy the covalent bond backbone of the modified branched polyamine polymer molecular main chain, ensuring that the molecular structure of the modified branched polyamine polymer remains intact after the coordination complexation reaction, further reducing the decomposition rate of the modified branched polyamine polymer, thus not increasing the overall consumption of the modified branched polyamine polymer.

[0018] 3) Since the toxicity of the amide bonds, amino ligands and nitrogen-oxygen mixed polydentate ligands contained in the modified branched polyamine polymer is lower than that of the thiourea group in thiourea or derivatives containing thiourea structure, the toxicity of the modified branched polyamine polymer to the human body is effectively reduced, thereby reducing the damage to the human body from long-term exposure.

[0019] 4) Since the auxiliary complexing agent is a cationic oligosaccharide complex, it contains oligosaccharide molecular structures. Furthermore, because the oligosaccharide molecular structures of the cationic oligosaccharide complex are positively charged through protonation, they form stable multi-point adsorption on the cathode surface. This allows it to work synergistically with the cationic surfactant of the cationic oligosaccharide complex to adsorb onto the cathode surface, thereby hindering the adsorption of metal ions (such as Sn). 2+ Cu 2+The diffusion rate to the cathode surface limits the migration ability of metal atoms on the crystal nucleus surface, making it difficult for metal atoms to continue to deposit and grow on the original grains, forcing the formation of more new crystal nuclei, thereby refining the tin-copper grains and narrowing the reduction potential difference between copper ions and tin ions. Furthermore, since the oligosaccharide molecule itself contains amino and hydroxyl groups, it can play a good role in complexing stability of tin ions in the tin-copper co-plating solution and inhibiting the oxidation of metal ions, while also improving the dispersion ability of the tin-copper co-plating solution. Thus, through the synergistic effect of the oligosaccharide molecule structure of the cationic oligosaccharide complex and the cationic surfactant, the deposition content of tin and copper in the tin-copper co-plating solution and the hydrogen evolution side reaction are effectively controlled, ensuring the uniformity and density of the tin-copper co-plating layer. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a scanning electron microscope (SEM) image of the tin-copper co-plating layer in Example 1 of the present invention; Figure 2 This is a scanning electron microscope (SEM) image of the tin-copper co-plating layer in Example 2 of the present invention; Figure 3 This is a scanning electron microscope (SEM) image of the tin-copper co-plating layer in Example 3 of the present invention; Figure 4 This is a scanning electron microscope (SEM) image of the tin-copper co-plating layer in Example 4 of the present invention; Figure 5 This is a scanning electron microscope (SEM) image of the tin-copper co-plating layer in Example 5 of the present invention; Figure 6 This is a scanning electron microscope (SEM) image of the tin-copper co-plated layer in Comparative Example 1 of the present invention. Figure 7 This is a scanning electron microscope (SEM) image of the tin-copper co-plated layer in Comparative Example 2 of the present invention. Figure 8 This is a scanning electron microscope (SEM) image of the tin-copper co-plated layer of Comparative Example 3 of the present invention. Figure 9 This is a scanning electron microscope (SEM) image of the tin-copper co-plated layer in Comparative Example 4 of the present invention. Figure 10 This is a scanning electron microscope (SEM) image of the tin-copper co-plated layer of Comparative Example 5 of the present invention. Detailed Implementation

[0022] To facilitate understanding of this disclosure, a more complete description will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the present disclosure. However, this disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0023] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] To better understand the technical solutions and beneficial effects of this disclosure, the following detailed description is provided in conjunction with specific embodiments: One embodiment of a pyrophosphate-free tin-copper co-plating additive includes a primary complexing agent and an auxiliary complexing agent. The primary complexing agent is a modified branched polyamine polymer, which is generated by reacting a branched polyamine polymer with an oxazolylcarboxylic acid compound. The modified branched polyamine polymer contains amino ligands and nitrogen-oxygen mixed polydentate ligands. The auxiliary complexing agent is a cationic oligosaccharide complex.

[0026] It is understood that, since the main complexing agent is a modified branched polyamine polymer, which is generated by reacting a branched polyamine polymer with an oxazolyl carboxylic acid compound, the amino group of the branched polyamine polymer undergoes dehydration to form an amide bond with the carboxyl group of the oxazolyl carboxylic acid compound. This allows the oxazolyl carboxylic acid compound to be grafted onto the modified branched polyamine polymer, ensuring that the final modified branched polyamine polymer contains amino ligands and nitrogen-oxygen mixed polydentate ligands. The amino ligands mainly form stable five- or six-membered chelate ring structures with copper ions through the lone pair electrons on the nitrogen atom, selectively inhibiting the preferential deposition of copper ions. This mechanism significantly increases the copper deposition overpotential and significantly reduces the reduction rate of copper ions at the cathode, thus ensuring that the modified branched polyamine polymer has the ability to react with Cu.2+ The extremely high affinity ligands enable Cu 2+ The actual reduction potential shifts significantly negatively, Sn 2+ The reduction potential is less affected, achieving a high tin, low copper deposition effect. Furthermore, because the nitrogen-oxygen mixed multidentate ligand preferentially combines with copper ions in the tin-copper co-plating solution to form a stable complex, the copper concentration is further reduced, thus ensuring the high tin, low copper deposition effect and effectively avoiding excessive fluctuations in the tin-copper co-plating solution content, thereby reducing the difficulty of controlling the tin-copper co-plating solution. In other words, by regulating the tin-copper co-plating, tin and copper can be reduced stably and continuously at a suitable ratio, allowing for uniform co-deposition. This results in preferential adsorption near the cathode to microscopic protrusions or areas with high current density, forming a uniform, flat, and dense tin-copper co-plating layer. This effectively inhibits tin whisker growth, ensuring the formed tin-copper co-plating layer possesses excellent density, solderability, and corrosion resistance, meeting the stringent requirements of precision electronic components for highly stable tin-copper co-plating layers. In addition, this additive system completely eliminates pyrophosphate, avoiding the problems of phosphorus-containing wastewater treatment, and combines the advantages of being green, environmentally friendly, efficient, and producing excellent coating quality, making it better suited for the rapid development of the electroplating field.

[0027] It can also be understood that, because the amide bonds formed by the reaction of the modified branched polyamine polymer with the oxazolyl carboxylic acid compound have good stability and are not easily oxidized and decomposed, the decomposition rate of the modified branched polyamine polymer is reduced; and the modified branched polyamine polymer is formed by the reaction of amino ligands and nitrogen-oxygen mixed polydentate ligands with metal ions (such as Cu). 2+ Sn 2+ The coordination complexation reaction that occurs does not destroy the covalent bond backbone of the modified branched polyamine polymer molecular main chain, ensuring that the molecular structure of the modified branched polyamine polymer remains intact after the coordination complexation reaction, further reducing the decomposition rate of the modified branched polyamine polymer, thus not increasing the overall consumption of the modified branched polyamine polymer.

[0028] It is also understood that, since the amide bonds, amino ligands and nitrogen-oxygen mixed polydentate ligands contained in the modified branched polyamine polymer are less toxic than the thiourea groups in thiourea or derivatives containing thiourea structures, the toxicity of the modified branched polyamine polymer to the human body is effectively reduced, thereby reducing the harm to the human body from long-term exposure.

[0029] It can also be understood that, since the auxiliary complexing agent is a cationic oligosaccharide complex, the cationic oligosaccharide complex contains oligosaccharide molecular structures. Furthermore, because the oligosaccharide molecular structures of the cationic oligosaccharide complex are positively charged through protonation, they can interact with the cationic surfactant of the cationic oligosaccharide complex and adsorb onto the cathode surface, thereby hindering the adsorption of metal ions (such as Cu). 2+ Sn 2+The diffusion rate to the cathode surface limits the migration ability of metal atoms on the crystal nucleus surface, making it difficult for metal atoms to continue to deposit and grow on the original grains, forcing the formation of more new crystal nuclei, thereby refining the tin-copper grains and narrowing the reduction potential difference between copper ions and tin ions. Furthermore, since the oligosaccharide molecule itself contains amino and hydroxyl groups, it can play a good role in complexing stability of tin ions in the tin-copper co-plating solution and inhibiting the oxidation of metal ions. At the same time, it also improves the dispersion ability of the tin-copper co-plating solution. Thus, through the synergistic effect of the oligosaccharide molecule structure of the cationic oligosaccharide complex and the cationic surfactant, the deposition content of tin and copper in the tin-copper co-plating solution and the hydrogen evolution side reaction are effectively controlled, ensuring the uniformity and density of the tin-copper co-plating layer.

[0030] In one embodiment, the branched polyamine polymer includes at least one of branched polyethyleneimine and branched polyamide. It is understood that both branched polyethyleneimine and branched polyamide contain amino ligands, ensuring that the added branched polyamine polymer can undergo an amidation condensation reaction with the oxazolyl carboxylic acid compound. Simultaneously, it ensures that the added branched polyamine polymer has low toxicity, effectively reducing the toxicity of the modified branched polyamine polymer to humans. Furthermore, the main chains of branched polyethyleneimine and branched polyamide also contain amine and amide bonds, exhibiting superior biodegradability, reducing the environmental accumulation and potential bioaccumulation risks of tin-copper co-plating additives, and achieving environmental friendliness and safety in the use of the tin-copper co-plating solution.

[0031] In one embodiment, the molecular weight of the branched polyamine polymer is 600 Da-1000 Da. This is to ensure that the molecular bond length of the branched polyamine polymer is suitable, guaranteeing that the modified branched polyamine polymer contains an appropriate concentration of amino ligands and nitrogen-oxygen mixed polydentate ligands, thereby achieving a stable complexation effect on copper ions. This effectively avoids situations where the amino density is too low due to molecular chains shorter than 600 Da, making it impossible to ensure that the prepared modified branched polyamine polymer contains amino ligands. Simultaneously, it avoids situations where the amino density is too high due to molecular chains longer than 1000 Da, causing the oxazole ring structure of the oxazole carboxylic acid compound to be easily wrapped and encapsulated by the branched polyamine polymer molecules after the amidation condensation reaction, resulting in insufficient exposure of the nitrogen-oxygen mixed polydentate ligands and affecting the complexation effect on copper ions.

[0032] In one embodiment, the oxazolylcarboxylic acid compound includes at least one selected from 2,4-dimethyloxazol-5-carboxylic acid, 5-oxazolylcarboxylic acid, 3-(5-oxazolyl)benzoic acid, and 3-isooxazolylcarboxylic acid. It is understood that since 2,4-dimethyloxazol-5-carboxylic acid, 5-oxazolylcarboxylic acid, 3-(5-oxazolyl)benzoic acid, and 3-isooxazolylcarboxylic acid all contain an oxazolyl ring and a carboxyl group, it ensures that the added oxazolylcarboxylic acid compound can undergo an amidation condensation reaction with the amino group of the branched polyamine polymer, thereby grafting the oxazolyl ring onto the branched polyamine polymer molecular chain and ensuring that the modified branched polyamine polymer generated by the reaction contains a nitrogen-oxygen mixed polydentate ligand.

[0033] It is also understandable that the oxazole ring of 2,4-dimethyloxazol-5-carboxylic acid has a dimethyl structure, which increases steric hindrance and makes the nitrogen-oxygen mixed polydentate ligands more effective against Sn. 2+ The complexation is more selective, avoiding excessive complexation that could lead to an excessively negative shift in the tin reduction potential, thus achieving a high tin, low copper deposition effect; because the oxazole ring of 5-oxazolamide is unsubstituent and has low steric hindrance, the nitrogen-oxygen mixed multidentate ligands facilitate Cu deposition. 2+ The complexation response is faster, enabling rapid deposition of high tin and low copper. Because 3-(5-oxazolyl)benzoic acid also contains a benzene ring, the introduced benzene ring significantly increases the hydrophobicity of the modified branched polyamine polymer, allowing tin and copper to be reduced steadily and continuously in a suitable ratio. This results in uniform tin-copper co-deposition, preferentially adsorbing onto microscopic protrusions or areas with high current density near the cathode to form a uniform, flat, and dense tin-copper co-plating layer, effectively inhibiting tin whisker growth. Furthermore, the isoxazolium ring of 3-isooxazolylcarboxylic acid contains a nitrogen-oxygen adjacent ring structure, allowing the nitrogen-oxygen adjacent structure to form a stable five-membered chelate ring structure with copper metal ions, which is beneficial for achieving a high tin and low copper deposition effect.

[0034] In one embodiment, the molar ratio of the branched polyamine polymer to the oxazolylcarboxylic acid compound is 1:(3-4). This 1:(3-4) ratio, especially when combined with the use of a branched polyamine polymer with a molecular weight of 600 Da-1000 Da, ensures that one molecule of the branched polyamine polymer contains 6-10 amino molecules. When one molecule of the branched polyamine polymer undergoes an amidation condensation reaction with 3-4 oxazolylcarboxylic acid compounds, only 3-4 amino molecules are consumed, leaving 2-7 unreacted amino molecules. These remaining amino molecules are retained on the modified branched polyamine polymer molecule to form multiple amino polyligands. Simultaneously, the grafted oxazolylcarboxylic acid compound contains a nitrogen-oxygen mixed polydentate ligand, ensuring that the formed modified branched polyamine polymer contains both amino ligands and nitrogen-oxygen mixed polydentate ligands, thereby ensuring that the modified branched polyamine polymer exhibits resistance to Cu. 2+While possessing extremely high affinity, it also ensures protection against Sn. 2+ The original potential is less affected, achieving a high tin, low copper deposition effect; it effectively avoids the problem of insufficient nitrogen-oxygen mixed multidentate ligands introduced into the modified branched polyamine polymer due to an excessively low molar ratio of branched polyamine polymer to oxazolyl carboxylic acid compound; at the same time, it also avoids the problem of excessively high molar ratio of branched polyamine polymer to oxazolyl carboxylic acid compound, which would reduce the residual amino ligands in the modified branched polyamine polymer, thereby reducing the impact on Cu. 2+ Due to its strong complexing ability, it cannot achieve a high tin, low copper deposition effect.

[0035] In one embodiment, the cationic oligosaccharide complex includes at least two of oligosaccharide ligands, oligosaccharide ligand derivatives, and cationic surfactants. Since the oligosaccharide ligands and oligosaccharide ligand derivatives in the cationic oligosaccharide complex share an oligosaccharide molecular structure, and since the oligosaccharide molecular structure of the oligosaccharide ligand or oligosaccharide ligand derivative carries a positive charge through protonation, it can interact with the cationic surfactant of the cationic oligosaccharide complex and adsorb onto the cathode surface, thereby hindering the adsorption of metal ions (such as Sn). 2+ Cu 2+ The diffusion rate to the cathode surface limits the migration ability of metal atoms on the crystal nucleus surface, making it difficult for metal atoms to continue to deposit and grow on the original grains, forcing the formation of more new crystal nuclei, thereby refining the tin-copper grains and narrowing the reduction potential difference between copper ions and tin ions. In this way, through the synergistic effect of the oligosaccharide molecular structure of the cationic oligosaccharide complex and the cationic surfactant, the deposition content of tin and copper and the hydrogen evolution side reaction in the tin-copper co-plating solution are effectively controlled, ensuring the uniformity and density of the tin-copper co-plating layer.

[0036] It is understood that, due to the protonation of the oligosaccharide ligand or oligosaccharide ligand derivative under acidic conditions, the amino groups in the molecular structure of the oligosaccharide ligand and oligosaccharide ligand derivative ( ) and hydrogen ions (H+) in organic acid solutions + ) combine, acquire a positive charge, and form an ammonium ion ( This ensures that the oligosaccharide ligands or their derivatives form an effect similar to cationic surfactants, thereby ensuring that the oligosaccharide ligands or their derivatives possess strong electrostatic adsorption properties and actively adsorb onto the cathode surface to form an adsorption layer. This increases the number of crystal nucleation sites, effectively refines the tin-copper grains, and narrows the reduction potential difference between copper ions and tin ions. Simultaneously, since the oligosaccharide ligands or their derivatives themselves contain amino and hydroxyl groups, they can complex and stabilize tin ions in the tin-copper co-plating solution and provide antioxidant effects, effectively reducing the decomposition rate of the modified branched polyamine polymer during the tin-copper electroplating process, thus reducing the overall consumption of tin-copper co-plating additives. Furthermore, the amino and hydroxyl groups contained in the oligosaccharide ligands or their derivatives can enhance the dispersion ability of the tin-copper co-plating solution, effectively controlling the deposition content of tin and copper and the hydrogen evolution side reaction in the tin-copper co-plating solution, ensuring the uniformity and density of the tin-copper co-plated layer.

[0037] In one embodiment, the cationic surfactant comprises at least one of N-octadecyl-4-styrylpyridine bromide, 1-octadecyl-4-(4-phenyl-1,3-butadienyl)pyridine bromide, N-octylpyridine bromide, and 1,1'-di-n-octyl-4,4'-bidibromide pyridine bromide, to ensure that the added cationic surfactant is an aromatic heterocyclic cationic surfactant. This allows the cationic surfactant to provide strong adsorption for tin-copper ions through the aromatic heterocyclic π-electron system and electrostatic interaction, thereby enhancing cathode polarization and forming an effective micro-bump selective adsorption layer on the cathode surface. This ensures that the heterocyclic π-electron system interacts with free Cu ions under the influence of the electric field. 2+ Sn 2+ Transient coordination occurs, regulating the interfacial ion concentration distribution to suppress Cu. 2+ Prioritized reduction effectively controls tin-copper co-plating, allowing tin and copper to be reduced stably and continuously at a suitable ratio. This ensures uniform tin-copper co-deposition and effectively avoids large fluctuations in the content of the tin-copper co-plating solution. Simultaneously, it provides a leveling effect on the plating layer and enhances the solution dispersion ability of the tin-copper co-plating solution. Especially with the synergistic effect of oligosaccharide ligands and oligosaccharide ligand derivatives, the cationic surfactant is less prone to partial desorption from the oligosaccharide ligands and derivatives under a strong electric field with a more negative potential. This effectively controls the deposition content of copper and tin in the tin-copper co-plating layer and the hydrogen evolution side reaction, resulting in a uniformly crystalline, flat, and dense tin-copper co-plating layer.

[0038] It is also understandable that, due to the large conjugated styrene group of N-octadecyl-4-styrylpyridine bromide, the π-electron adsorption effect is further enhanced, which can significantly improve the adsorption capacity of cationic surfactants on the cathode surface and the smoothing effect of the tin-copper co-plating layer. Furthermore, because the conjugated chain of 1-octadecyl-4-(4-phenyl-1,3-butadienyl)pyridine bromide is longer, the π-electron delocalization range is larger, enhancing its affinity for Cu under an electric field.2+ Sn 2+ The ability to undergo transient coordination allows for more effective control of tin-copper deposition. Due to the relatively small molecular weight of N-octylpyridine bromide, it exhibits a faster electromigration rate, preferentially adsorbing onto microscopic bumps at high current densities, thus providing an efficient leveling effect for the tin-copper co-plating layer. Furthermore, the presence of two positively charged head groups in 1,1'-di-n-octyl-4,4'-bidibromide pyridine allows for simultaneous adsorption on the cathode surface, forming extremely strong multi-point adsorption. This further stabilizes the adsorption layer, induces directional grain growth, and enhances the density and uniformity of the tin-copper co-plating layer.

[0039] In one embodiment, the molecular weight of the oligosaccharide ligand is 800 Da-1200 Da, or the molecular weight of the oligosaccharide ligand derivative is 800 Da-1200 Da, to ensure that the molecular chains of the oligosaccharide ligand and its derivative are suitable. This ensures that the oligosaccharide ligand and its derivative possess optimal molecular size and density of active amino and hydroxyl functional groups, enabling stable multi-site adsorption through the protonation of multiple amino groups while retaining a large number of hydroxyl groups, thereby ensuring that the oligosaccharide ligand and its derivative have appropriate desorption capacity. This ensures that the oligosaccharide ligands and oligosaccharide ligand derivatives form an adsorption layer on the cathode surface, providing nucleation sites to refine the grains, thus ensuring the uniformity and density of the tin-copper co-plating layer. It effectively avoids the decrease in flexibility and tendency for intramolecular entanglement of oligosaccharide ligands or oligosaccharide ligand derivatives due to excessively long molecular chains, which would result in some amino or hydroxyl groups being encapsulated within the molecule and unable to contact metal ions, thus affecting the adsorption effect on metal ions. It also effectively avoids the situation where oligosaccharide ligands or oligosaccharide ligand derivatives have insufficient amino and hydroxyl content due to excessively low molecular weight (<800 Da), making it difficult to form stable multi-point adsorption and thus failing to achieve the effect of refining the grains.

[0040] In one embodiment, the oligosaccharide ligand includes at least one of oligochitosan, oligoglucosamine, oligogalactosamine, and oligomannosamine to ensure that the oligosaccharide ligand itself contains amino and hydroxyl groups.

[0041] In one embodiment, the oligosaccharide ligand is unsubstituted oligochitosan. Because oligochitosan retains intact amino and hydroxyl groups, it possesses strong adsorption capacity for Sn. 2+ It exhibits significant complexation stabilization, high nucleation site density, and outstanding grain refinement effect.

[0042] In one embodiment, the oligosaccharide ligand derivative includes at least one of carboxymethyl oligochitosan, ethylene glycol oligochitosan, and oligogalactosamine to ensure that the oligosaccharide ligand derivative itself contains amino and hydroxyl groups.

[0043] It can also be understood that carboxymethyl oligochitosan, due to the introduction of carboxymethyl groups, possesses amphoteric polyelectrolyte properties. The carboxyl and amino groups form a proton buffer pair, which can effectively maintain the pH stability of the cathode surface and suppress hydrogen evolution side reactions. Because ethylene glycol oligochitosan introduces ethylene glycol groups through etherification of the hydroxyl groups, its hydrophilicity is enhanced, improving its dispersion ability in the tin-copper co-plating solution. This facilitates the formation of a more uniform adsorption layer on the cathode surface, thereby improving the leveling effect of the tin-copper co-plating layer. The hydroxypropyl groups introduced by hydroxypropyl chitosan have a certain steric hindrance, enhancing the interfacial retention ability of the oligosaccharide ligands and oligosaccharide ligand derivatives on the cathode surface, allowing tin and copper to be reduced smoothly and continuously in a suitable ratio, resulting in uniform tin-copper co-deposition.

[0044] This disclosure also provides a method for preparing a pyrophosphate-free tin-copper co-plating additive. First, a branched polyamine polymer, an oxazolyl carboxylic acid compound, and a polar aprotic solvent are mixed to obtain a mixed solution. Next, a core condensing agent, a condensing aid, and an acid neutralizing agent are added to the mixed solution to carry out an amidation condensation reaction to obtain a modified branched polyamine polymer precursor. Subsequently, the modified branched polyamine polymer precursor is separated and purified to obtain the modified branched polyamine polymer.

[0045] The above-mentioned method for preparing pyrophosphate-free tin-copper co-plating additives involves mixing branched polyamine polymers, oxazolyl carboxylic acid compounds, and polar aprotic solvents, followed by amidation condensation reactions and separation and purification operations. This method efficiently prepares modified branched polyamine polymers with relatively uniform and high-purity nitrogen-oxygen mixed multidentate ligand sites and amino ligand sites. It effectively avoids the problems of increased side reactions and increased difficulty in separation and purification operations caused by the simultaneous addition of core condensing agents, condensation aids, acid neutralizers, branched polyamine polymers, oxazolyl carboxylic acid compounds, and polar aprotic solvents. Furthermore, the raw materials involved in the reaction do not contain highly toxic substances, making the production process more green and environmentally friendly.

[0046] A method for preparing a pyrophosphate-free tin-copper co-plating additive, comprising some or all of the following steps: S101. The branched polyamine polymer, oxazolylcarboxylic acid compound, and polar aprotic solvent are mixed to obtain a mixed solution. It is understood that the polar aprotic solvent can fully dissolve the branched polyamine polymer and oxazolylcarboxylic acid compound, constructing a homogeneous reaction system. This allows the molecular chains of the branched polyamine polymer and the molecular bonds of the oxazolylcarboxylic acid compound to extend, ensuring a stable molecular contact environment for the subsequent amidation condensation reaction. This effectively avoids the branched polyamine polymer from being grafted with too many oxazol rings due to the amidation condensation reaction being too rapid, resulting in an overly dense concentration of nitrogen-oxygen mixed multidentate ligand sites. This slows down the copper deposition rate in the tin-copper co-plating solution, leading to a low copper content in the tin-copper co-plating layer and ultimately causing tin enrichment and precipitation.

[0047] In one embodiment, the polar aprotic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, and dimethyl sulfoxide, which can effectively dissolve the branched polyamine polymer molecular chains and the molecular bond extension of the oxazolyl carboxylic acid compound, thus facilitating the construction of a homogeneous reaction system.

[0048] In one embodiment, the molar ratio of the branched polyamine polymer to the oxazolylcarboxylic acid compound is 1:(3-4).

[0049] In one embodiment, the amount of the polar aprotic solvent used is 10 mL to 20 mL to ensure that the added polar aprotic solvent can fully dissolve the branched polyamine polymer and the oxazolyl carboxylic acid compound.

[0050] S102. Add a core condensing agent, a condensing aid, and an acid neutralizer to the mixed solution to carry out an amidation condensation reaction, so that the oxazolyl carboxylic acid is covalently grafted onto the branched polyamine polymer molecular chain, to ensure that the generated modified branched polyamine polymer contains both the amino ligand and the nitrogen-oxygen mixed polydentate ligand, thus obtaining the modified branched polyamine polymer precursor.

[0051] In one embodiment, the step of adding a core condensing agent, a condensation aid, and an acid neutralizer to the mixed solution for an amidation condensation reaction includes the following specific steps: under a nitrogen atmosphere and at room temperature, the mixed solution is dropped into a container bottle, and then the core condensing agent, the condensation aid, and the acid neutralizer are added sequentially and the mixture is stirred continuously for 12-20 hours.

[0052] It is understood that the amino groups in the branched polyamine polymer and the core condensing agent are easily oxidized in the presence of oxygen, leading to a decrease in reactant activity. Therefore, in this disclosure, the amidation condensation reaction needs to be carried out in a nitrogen-protected environment to effectively avoid amino oxidation and core condensing agent deactivation. Since the heterocyclic structure in the oxazolylcarboxylic acid compound and the branching point of the branched polyamine polymer can decompose or undergo side reactions under high-temperature conditions, in this disclosure, the reaction temperature of the oxazolylcarboxylic acid compound and the branched polyamine polymer needs to be controlled at room temperature. This can effectively reduce the decomposition or side reactions between the branched polyamine polymer and the oxazolylcarboxylic acid compound, thereby better protecting the structural integrity of the branched polyamine polymer and the oxazolylcarboxylic acid compound, ensuring that the final modified branched polyamine polymer contains both amino ligands and nitrogen-oxygen mixed polydentate ligands.

[0053] It can also be understood that in the step of adding a core condensing agent, condensing aid, and acid neutralizer to the mixed solution for the amidation condensation reaction, the core condensing agent, condensing aid, and acid neutralizer must be added sequentially to ensure that the core condensing agent added first can preferentially react with the carboxyl group of the oxazolylcarboxylic acid compound to generate an active O-acylisourea intermediate. The O-acylisourea intermediate is a key active species in the amidation reaction, which can significantly reduce the activation energy of the reaction between the amino and carboxyl groups, i.e., initiate the activation of the carboxyl group of the oxazolylcarboxylic acid compound. Then, the addition of the condensing aid can promptly capture the active oxyacylisourea intermediate, allowing the oxyacylisourea intermediate to react with the amino group of the branched polyamine polymer in an acyl-reactive reaction. The amination reaction effectively avoids the problem of side reactions easily occurring in the active oxyacyl isourea intermediate caused by the simultaneous addition of the core condensing agent, condensation aid, acid neutralizer, branched polyamine polymer, oxazolyl carboxylic acid compound, and polar aprotic solvent. This improves the purity and reaction efficiency of the modified branched polyamine polymer precursor. Finally, the addition of an acid neutralizer can neutralize the acid produced in the reaction, maintain the nucleophilic activity of the amino group of the branched polyamine polymer, and avoid the decomposition of the core condensing agent. This achieves a highly efficient and controllable amidation condensation reaction, and efficiently prepares a modified branched polyamine polymer precursor with relatively uniform and high-purity nitrogen-oxygen mixed multidentate ligand sites and amino ligand sites.

[0054] In one embodiment, the core condensing agent includes at least one of EDC·HCl, DDC, and DIC. It is understood that since EDC·HCl, DDC, and DIC are all carbodiimide condensing agents, this ensures that the carbodiimide functional group contained in the core condensing agent can effectively initiate the carboxyl activation of the oxazolyl carboxylic acid compound.

[0055] In one embodiment, the condensation aid includes at least one of HOAt, HOBt, OXyma Pure, and OXyma-B.

[0056] It is understandable that since HOAt, HOBt, OXyma Pure, and OXyma-B are all auxiliary nucleophiles for carbodiimide condensing agents, the added condensing aids can promptly capture the active oxyacyl isourea intermediate, allowing the oxyacyl isourea intermediate to undergo amidation reaction with the amino group of the branched polyamine polymer. This effectively inhibits side reactions of the active oxyacyl isourea intermediate, thereby increasing the purity and reaction efficiency of the modified branched polyamine polymer precursor.

[0057] In one embodiment, the acid neutralizing agent includes at least one of triethylamine, N,N-diisopropylethylamine, N-methylmorpholine, and pyridine.

[0058] It is understandable that since triethylamine, N,N-diisopropylethylamine, N-methylmorpholine, and pyridine are all organic bases, this ensures that the amidation reaction system is in a weakly alkaline environment, thereby enhancing the nucleophilic activity of the amino groups on the branched polyamine polymer and avoiding the decomposition of the core condensing agent, thus achieving a highly efficient and controllable amidation condensation reaction.

[0059] S103. The modified branched polyamine polymer precursor is separated and purified to effectively remove residual polar aprotic solvent, a small amount of unreacted branched polyamine polymer and oxazolyl carboxylic acid compound, a small amount of condensation reaction byproducts, core condensing agent, condensation aid and acid neutralizer in the reaction system, so as to ensure that the modified branched polyamine polymer with relatively uniform nitrogen-oxygen mixed multidentate ligand sites and amino ligand sites and high purity is obtained.

[0060] In one embodiment, the step of separating and purifying the modified branched polyamine polymer precursor to obtain the modified branched polyamine polymer includes the following specific steps: First, the modified branched polyamine polymer precursor is added to a precipitant and then filtered to obtain a precipitate; then, the precipitate is subjected to precipitation washing and drying operations in sequence.

[0061] It is understandable that, due to the extremely low solubility of the modified branched polyamine polymer in the precipitant, the modified branched polyamine polymer precursor can rapidly form a solid precipitate in the precipitant, while the residual polar aprotic solvent, a small amount of unreacted branched polyamine polymer and oxazolyl carboxylic acid compound, a small amount of condensation reaction byproducts, the core condensing agent, condensation aid, and acid neutralizer in the reaction system remain dissolved in the precipitant, thus achieving efficient separation of the modified branched polyamine polymer from the impurities in the reaction system. Subsequently, the precipitation washing operation can further remove impurities attached to the surface of the modified branched polyamine polymer precursor, ensuring that the purity of the obtained modified branched polyamine polymer is further improved. Finally, a drying operation is performed to ensure that a high-purity modified branched polyamine polymer is obtained.

[0062] In one embodiment, the precipitant includes acetone, icy ether, ethanol, and ethyl acetate to ensure that the modified branched polyamine polymer can undergo a precipitation reaction with the precipitant.

[0063] In one embodiment, the precipitation washing operation includes the following specific steps: the modified branched polyamine polymer precursor is gradually added dropwise to the precipitant to generate a white to light yellow precipitate, which is then filtered to obtain the precipitate and subsequently washed with a detergent to ensure that the modified branched polyamine polymer with relatively uniform nitrogen-oxygen mixed multidentate ligand sites and amino ligand sites and high purity is obtained.

[0064] In one embodiment, the drying operation is performed under vacuum drying conditions; vacuum drying can remove volatile precipitants and detergents under mild conditions, while preventing the modified branched polyamine polymer from being oxidized and decomposed in a high-temperature aerobic environment, thereby obtaining a high-purity, stable, and easy-to-store dried solid of modified branched polyamine polymer.

[0065] This disclosure also provides a pyrophosphate-free tin-copper co-plating solution, comprising, by mass concentration, the following components: 20 g / L-60 g / L stannous salt compound; 1.5 g / L-2.7 g / L copper salt; 20 g / L-40 g / L main complexing agent; 3.1 g / L-10 g / L auxiliary complexing agent; 0.1 g / L-2.0 g / L brightener; 8 g / L-15 g / L antioxidant; 120 g / L-180 g / L organic acid, with the balance being water. The main complexing agent is a modified branched polyamine polymer; the auxiliary complexing agent is a cationic oligosaccharide complex; the main complexing agent and the auxiliary complexing agent constitute the pyrophosphate-free tin-copper co-plating additive described in any of the above embodiments.

[0066] In one embodiment, the water concentration is 720 g / L to 850 g / L by mass.

[0067] The aforementioned pyrophosphate-free tin-copper co-plating solution, through reasonable control of the mass concentrations of stannous salts, copper salts, primary complexing agents, auxiliary complexing agents, brighteners, antioxidants, and organic acids, ensures that the added modified branched polyamine polymer can achieve the desired Cu plating performance. 2+ The extremely high affinity ligands enable Cu 2+ The actual reduction potential shifts significantly negatively, Sn 2+ The reduction potential is less affected, achieving a high tin, low copper deposition effect; it effectively controls tin-copper co-plating, allowing tin and copper to be reduced stably and continuously at a suitable ratio, enabling tin and copper to co-deposit at a uniform rate, ensuring that the copper ion deposition content in tin-copper co-plating is less than 1%, which can improve the tin grain boundary structure, prevent tin grain growth and recrystallization, and effectively suppress tin whiskers; at the same time, with the synergistic effect of cationic oligosaccharide complexes, it can effectively refine tin-copper grains to form a uniform, flat and dense tin-copper co-plating layer; it also reduces the decomposition rate of modified branched polyamine polymers, avoiding an increase in the overall consumption of modified branched polyamine polymers, allowing the pyrophosphate-free tin-copper co-plating solution to be used stably for a long time, achieving green and environmentally friendly results.

[0068] In one embodiment, the stannous salt compound includes at least one of stannous methanesulfonate, stannous ethylsulfonate, and stannous propylsulfonate, which can provide Sn for pyrophosphate-free tin-copper co-plating solutions. 2+ .

[0069] In one embodiment, the copper salt is an alkyl sulfonate copper salt. The alkyl sulfonate copper salt includes at least one of copper methanesulfonate, copper ethanesulfonate, and copper propanesulfonate, capable of providing Cu to the pyrophosphate-free tin-copper co-plating solution. 2+ In particular, the use of 1.5g / L-2.7g / L copper salt, 20g / L-60g / L stannous salt compounds, 20g / L-40g / L main complexing agent and 3.1g / L-10g / L auxiliary complexing agent ensures that the tin-copper deposition content in the pyrophosphate-free tin-copper co-plating solution can be reduced steadily and continuously in a suitable ratio under the complexing effect of the main and auxiliary complexing agents. This allows tin and copper to co-deposit at a uniform rate, ensuring that the deposition content of copper ions in the tin-copper co-plating is less than 1%. This can improve the tin grain boundary structure, prevent tin grain growth and recrystallization, and effectively suppress tin whiskers.

[0070] In one embodiment, the brightener includes at least one of 1,4-dithiothreitol, 1-eicosenethiol, 1,16-hexadecanedithiol, 1-octadecylthiol, 11-mercapto-1-undecanol, cysteine, and mercapto-undecanamine hydrochloride. Since 1,4-dithiothreitol, 1-eicosenethiol, 1,16-hexadecanedithiol, 1-octadecylthiol, 11-mercapto-1-undecanol, cysteine, and mercapto-undecanamine hydrochloride are all small-molecule thiol compounds and are non-volatile, this ensures that the added brightener has a fast diffusion rate, high light extraction efficiency, and can induce tin-copper crystals to grow along low-energy surfaces, further refining the crystal structure to obtain a tin-copper co-plating layer with low internal stress, uniform tin-copper crystals, a smooth and dense surface, and high gloss.

[0071] In one embodiment, the antioxidant includes at least one selected from 2,5-dihydroxy-1,4-benzoquinone, 2-methyl-8-hydroxyquinoline, p-hydroxybenzoic acid, syringic acid, and gallic acid. Since 2,5-dihydroxy-1,4-benzoquinone, 2-methyl-8-hydroxyquinoline, p-hydroxybenzoic acid, syringic acid, and gallic acid are all aromatic compounds containing phenolic hydroxyl groups, they all possess the ability to inhibit Sn. 2+ Oxidized to This reduces the oxidation of divalent tin ions, thereby maintaining the Sn content in the tin-copper co-plating solution. 2+ The effective concentration ensures the stability of the tin-copper co-plating solution and extends its service life; it also avoids... The stannic acid precipitate formed by hydrolysis is deposited into the tin-copper co-plating layer to ensure the formation of a tin-copper co-plating layer with accurate composition, uniform tin crystals, and a smooth and dense structure.

[0072] In one embodiment, the organic acid includes at least one of methanesulfonic acid, fluoroalkyl sulfonic acid, and hydroxyethyl sulfonic acid to ensure that the added organic acid can improve the conductivity of the tin-copper co-plating solution and maintain a stable acidic working environment, thereby effectively preventing the hydrolysis of stannous ions to form precipitates and thus effectively maintaining the Sn content of the tin-copper co-plating solution. 2+ Effective concentration.

[0073] This disclosure also provides a method for preparing a pyrophosphate-free tin-copper co-plating solution, comprising the following steps: first, obtaining a modified branched polyamine polymer; then, adding an organic acid to water, followed by sequentially adding a stannous salt compound and a copper salt to mix, thereby obtaining a tin-copper mixture; subsequently, sequentially adding an antioxidant, a cationic oligosaccharide complex, the modified branched polyamine polymer, and a brightener to the tin-copper mixture and mixing, and then adjusting the volume with water to 1L to obtain a pyrophosphate-free tin-copper co-plating solution.

[0074] The above-described method for preparing a pyrophosphate-free tin-copper co-plating solution involves first mixing stannous salt compounds and copper salts in an aqueous organic acid solution. This creates a stable acidic environment for tin-copper ions, preventing hydrolysis and precipitation, and ensuring a uniformly dispersed tin-copper mixture. Subsequently, an antioxidant, a cationic oligosaccharide complex, a modified branched polyamine polymer, and a brightener are added sequentially. The antioxidant is added first to ensure a pre-constructed antioxidant environment, protecting the Sn in the tin-copper mixture. 2+ Not oxidized to Then, a cationic oligosaccharide complex is added. This complex contains amino and hydroxyl groups, which provide good complexation stability for stannous ions in the tin-copper co-plating solution and inhibit metal ion oxidation. This avoids the localized Sn oxidation that occurs when the modified branched polyamine polymer is added. 2+ Concentration fluctuations affect the complexation equilibrium; subsequently, a modified branched polyamine polymer is added to ensure that the amino ligands and nitrogen-oxygen mixed polydentate ligands contained in the modified branched polyamine polymer can react with Cu. 2+ It exhibits extremely high affinity, thereby allowing for precise control of the high tin and low copper deposition effect, which is beneficial for constructing a high tin and low copper deposition system; the final brightener can induce tin-copper crystals to grow along the low energy surface, further refining the crystallization, in order to obtain a tin-copper co-plating layer with low internal stress, uniform tin-copper crystals, flatness, density, and gloss.

[0075] In one embodiment, the water is deionized water to ensure that impurity ions in the water completely eliminate interference with the composition of the pyrophosphate-free tin-copper co-plating solution, thereby ensuring the stability of the pyrophosphate-free tin-copper co-plating solution.

[0076] In one embodiment, an organic acid is added to water, and then a stannous salt compound and a copper salt are added sequentially under stirring conditions to create a stable acidic environment to prevent the stannous salt compound and the copper salt from hydrolyzing and precipitating.

[0077] In one embodiment, when stannous salt compounds and copper salts are added sequentially and mixed under stirring conditions, the stirring speed is 15 r / min-60 r / min. This ensures that the stannous salt compounds and copper salts are rapidly and uniformly dispersed in the tin-copper co-plating solution, preventing excessively high local concentrations that could lead to the hydrolysis of the stannous salt compounds and copper salts. Simultaneously, it avoids the introduction of large amounts of dissolved oxygen due to excessive stirring, which could cause Sn to degrade. 2+ It is oxidized.

[0078] In one embodiment, after adding an antioxidant, a cationic oligosaccharide complex, a modified branched polyamine polymer, and a brightener sequentially to the tin-copper mixture and mixing them, and then adjusting the volume to 1L with water, the following steps are also included: sequentially allowing the pyrophosphate-free tin-copper co-plating solution to stand and filter; since stirring during the mixing process introduces a large number of tiny bubbles, the standing operation allows the bubbles to float and burst, thereby effectively removing bubbles and ensuring that there are no residual bubbles in the pyrophosphate-free tin-copper co-plating solution, avoiding the problem of insufficient density of the tin-copper co-plating layer caused by bubbles adsorbing on the cathode surface during subsequent electroplating; the filtration operation can effectively remove undissolved raw material solid particles that settle after standing in the pyrophosphate-free tin-copper co-plating solution, ensuring that a pyrophosphate-free tin-copper co-plating solution with high purity, uniform and stable component dispersion is obtained.

[0079] In one embodiment, the pyrophosphate-free tin-copper co-plating solution is allowed to stand for 0.5-2 hours to effectively remove bubbles.

[0080] This disclosure also provides an application of the pyrophosphate-free tin-copper co-plating solution as described in any of the above embodiments in a plated part. First, the drag plate is placed in the tin-copper co-plating solution; weak electrolysis is performed at 15°C-25°C with a current density of 2ASF-8ASF; then, the drag plate is subjected to rough electroplating at a current density of 20ASF-30ASF for 20-30 minutes to plate the part; subsequently, the part is subjected to formal electroplating at a current density of 5ASF-30ASF for 5-30 minutes to obtain part A, so that a tin-copper co-plating layer is formed on the surface of part A.

[0081] The application of the aforementioned pyrophosphate-free tin-copper co-plating solution in the plated parts utilizes a three-stage electroplating process: weak electrolysis, coarse electroplating, and formal electroplating. This three-stage process fully leverages the advantages of the pyrophosphate-free tin-copper co-plating additive, ensuring that the amino ligands and nitrogen-oxygen mixed multidentate ligands in the modified branched polyamine polymer exhibit coordination and complexation reactions with metal ions in the tin-copper co-plating solution. This allows for precise control of high tin and low copper deposition. Simultaneously, the use of cationic oligosaccharide complexes and brighteners refines the tin-copper grains, smoothing the tin-copper co-plating layer and ensuring a uniform, flat, and dense tin-copper co-plating layer. Furthermore, it effectively inhibits tin whisker growth, ensuring the formed tin-copper co-plating layer possesses excellent density, solderability, and corrosion resistance. Moreover, the complete elimination of pyrophosphate during the electroplating process avoids the challenges of treating phosphorus-containing wastewater.

[0082] The application of a tin-copper co-plating solution in a plated part according to one embodiment includes some or all of the following steps: S201. Place the drag plate in the tin-copper co-plating solution; perform weak electrolysis at 15℃-25℃ with a current density of 2ASF-8ASF. It can be understood that weak electrolysis at 15℃-25℃ with a current density of 2ASF-8ASF can remove impurities and activate the tin-copper co-plating solution before formal electroplating. Under the action of a current density of 2ASF-8ASF, impurity ions in the plating solution preferentially precipitate onto the drag plate, and the additive components of the anode and plating solution are activated. This removes the passivation film of the anode and promotes the complexation of the additive components with metal ions.

[0083] S202. Perform rough electroplating on the tin-copper co-plating bath for 20-30 minutes at a current density of 20-30 ASF. This is understandable, as performing rough electroplating at a current density of 20-30 ASF for 20-30 minutes facilitates the rapid removal of any impurities that may exist in the tin-copper co-plating solution. Ion hydrolysis products and anode mud are rapidly adsorbed or encapsulated and deposited into the plating plate, reducing physical defects caused by the plating layer of subsequent parts, thus ensuring that a tin-copper co-plating layer with no tin whiskers, uniform tin-copper crystals, flatness, density and strong connectivity is finally obtained.

[0084] In one embodiment, the rough electroplating adopts a drag-tank electrolysis method. By performing rough electroplating at medium to high current densities, such as 20 ASF-30 ASF, the drag-tank electrolysis process allows the components in the tin-copper co-plating solution to react fully, achieve a dynamic balance between adsorption and desorption, and release the internal stress of the tin-copper co-plating solution.

[0085] S203. Subsequently, the workpiece is electroplated for 5-30 minutes at a current density of 5 ASF-30 ASF to obtain workpiece A, which forms a tin-copper co-plating layer on its surface. It can be understood that under the low current density of 5 ASF-30 ASF, the nucleation rate of tin-copper ions in the plating solution is greater than the grain growth rate, which helps to form a fine, dense, and uniform grain structure on the tin-copper substrate, ultimately resulting in a tin-copper co-plating layer with fine, uniform, flat, dense grains, no tin whiskers, and excellent solderability.

[0086] In one embodiment, mechanical cathode oscillation is used for stirring during both the rough electroplating and the formal electroplating. This mechanical cathode oscillation generates strong convection on the cathode surface of the tin-copper co-plating solution, ensuring uniform dispersion of the components. The generated strong convection also helps to disperse the Sn in the tin-copper co-plating solution. 2+ and Cu 2+ Rapidly delivered to the cathode surface to eliminate Sn 2 + and Cu 2+ Concentration polarization near the cathode surface, while utilizing modified branched polyamine polymers for Cu 2+ Sn's strong complexing ability enables it to... 2+ and Cu 2+ By depositing tin in a uniform proportion on all parts of the cathode surface, tin-copper segregation can be effectively avoided, thereby obtaining a tin-copper co-plating layer with fine, uniform, flat, dense tin-copper grains, no tin whiskers, and excellent solderability.

[0087] In one embodiment, before placing the plated part in the tin-copper co-plating solution for electroplating, the following steps are included: sequentially performing pickling, degreasing, and micro-etching operations on the plated part to remove contaminants and oxide layers from the surface of the plated part, thereby obtaining a clean, activated plated part with suitable micro-roughness, providing a better adhesion substrate for the subsequent tin-copper substrate.

[0088] In one embodiment, the pickling operation involves: using a pickling solution with a concentration of 1%-10% and a temperature of 15°C-25°C to pickle the untreated plated parts for 20-30 seconds; the pickling operation can quickly dissolve the thin oxide layer and contaminants on the surface of the plated parts, resulting in clean plated parts with a uniform surface condition. Further, the acid solution is... .

[0089] In one embodiment, the degreasing operation involves using a degreasing solution at a temperature of 30°C-40°C and a concentration of 2%-5% to degrease the plated parts after pickling for 1-5 minutes. This degreasing operation not only deeply removes residual oil stains from the plated parts surface but also ensures that the plated parts surface is in a highly activated state. This ensures that the subsequent micro-etching solution and tin-copper co-plating solution can be evenly spread on the plated parts surface after degreasing, providing a highly activated plated parts surface for the tin-copper crystal nuclei formed in the early stage of electroplating. This allows the deposited tin-copper crystal nuclei to firmly bond to the plated parts surface, thereby significantly enhancing the continuity strength between the tin-copper co-plating layer and the plated parts surface, and preventing incomplete plating or peeling of the formed tin-copper co-plating layer caused by oil stains.

[0090] In one embodiment, the degreasing solution is a 5% concentration M401 and A mixture of surfactants and acidic chemicals is used to ensure rapid degreasing and simultaneous activation of the plated surface through the synergistic effect of surfactant emulsification and acid chemical cleaning. It ensures that the surface of the plated part is prevented from being oxidized by air during the degreasing process, so as to achieve a pollution-free and highly activated plated surface.

[0091] In one embodiment, the micro-etching operation involves: using a micro-etching solution at a temperature of 25°C-35°C to perform micro-etching treatment on the degreased workpiece for 1-5 minutes to obtain the pre-treated workpiece; through the micro-etching operation, uniform and dense micro-etching pits can be formed on the surface of the workpiece, increasing the surface roughness of the workpiece, providing better adhesion for tin-copper crystals, significantly enhancing the continuity strength between the tin-copper co-plating layer and the surface of the workpiece, and facilitating the formation of a tin-copper co-plating layer on the surface of the workpiece that is free of tin whiskers, has uniform tin-copper crystals, is flat and dense, and has strong connectivity.

[0092] In one embodiment, the micro-etching solution is composed of a concentration... Composed of 40 g / L sodium persulfate, the synergistic effect of the strong oxidant sodium persulfate and acid ensures the formation of uniform and fine micro-etch pits on the surface of the plated parts, thereby significantly enhancing the adhesion between the plated parts and the tin-copper co-plating layer.

[0093] In one embodiment, the copper content in the tin-copper co-plating layer is <1%. When the copper content exceeds 1%, the tin-copper co-plating layer is prone to forming due to excessive copper content. ,and During formation, volume expansion occurs, increasing the internal compressive stress of the tin-copper co-plating layer and leading to tin whisker growth. Therefore, in this disclosure, by controlling the copper content to <1%, tin whisker growth can be significantly suppressed. The formation of this process effectively reduces the internal stress of the tin-copper co-plating layer, resulting in a uniform and dense tin-crystal tin co-plating layer. This effectively inhibits the growth of tin whiskers, and the uniform distribution of tin and copper components ensures performance stability during long-term storage and use. Furthermore, the tin-copper co-plating layer with a copper content of <1% closely resembles the characteristics of pure tin, exhibiting excellent and stable solderability and enabling rapid fusion with solder.

[0094] The following are some specific examples. When %, it refers to a percentage by weight. It should be noted that the following examples do not exhaustively list all possible scenarios, and unless otherwise specified, the materials used in the examples are commercially available. Example 1

[0095] 1. Branched polyethyleneimine with a molecular weight of 600 Da and 2,4-dimethyloxazol-5-carboxylic acid were mixed with 10 ml of N,N-dimethylformamide at a molar ratio of 1:3 to obtain a mixed solution. The mixed solution was added to a reaction vessel, and 1 mmol HOBt, 1 mmol EDC·HCl, and 0.85 mmol triethylamine were added sequentially under magnetic stirring (200 r / min). The reaction was carried out under nitrogen atmosphere and room temperature for 12 h to obtain a modified branched polyamine polymer precursor. After the reaction was completed, the modified branched polyamine polymer precursor was separated and purified to obtain the main complexing agent modified branched polyamine polymer ①. 2. Add 140 g / L methanesulfonic acid to an appropriate amount of deionized water, and then add 50 g / L stannous methanesulfonate and 2.4 g / L copper propanesulfonate in sequence while stirring. Stir until completely dissolved to obtain a tin-copper mixture. 3. Add 8 g / L of a combination of 2,5-dihydroxy-1,4-benzoquinone and gallic acid, 5 g / L of carboxymethyl oligochitosan and 0.5 g / L of N-octadecyl-4-styrylpyridine bromide, 20 g / L of modified branched polyamine polymer, 0.4 g / L of 1,4-dithiothreitol and 0.2 g / L of 1,16-hexadecanedithiol to the above tin-copper mixture in sequence. After stirring and dissolving evenly, dilute to 1 L with deionized water, let stand for 1 h, and filter to obtain a pyrophosphate-free tin-copper co-plating solution. Example 2

[0096] 1. Branched polyethyleneimine with a molecular weight of 1000 Da and 3-(5-oxazolyl)benzoic acid were mixed with 10 ml of N,N-dimethylformamide at a molar ratio of 1:4 to obtain a mixed solution. The mixed solution was added to a reaction vessel, and 1 mmol HOBt, 1 mmol EDC·HCl and 0.85 mmol triethylamine were added sequentially under magnetic stirring (200 r / min). The reaction was carried out under nitrogen atmosphere and room temperature for 20 h to obtain a modified branched polyamine polymer precursor. After the reaction was completed, the modified branched polyamine polymer precursor was separated and purified to obtain the main complexing agent modified branched polyamine polymer ②. 2. Add 120 g / L methanesulfonic acid to an appropriate amount of deionized water, and then add 60 g / L stannous ethyl sulfonate and 1.5 g / L copper methanesulfonate in sequence while stirring. Stir until completely dissolved to obtain a tin-copper mixture. 3. Add 10 g / L 2-methyl-8-hydroxyquinoline, 8 g / L oligochitosan, 0.8 g / L 1-octadecyl-4-(4-phenyl-1,3-butadienyl)pyridine bromide, 30 g / L modified branched polyamine polymer ②, and 0.6 g / L 11-mercapto-1-undecanol to the above tin-copper mixture in sequence. After stirring and dissolving evenly, dilute to 1 L with deionized water, let stand for 1 h, and filter to obtain a pyrophosphate-free tin-copper co-plating solution. Example 3

[0097] 1. Branched polyethyleneimine with a molecular weight of 800 Da and 3-isoxazolecarboxylic acid were mixed with 10 ml of N,N-dimethylformamide at a molar ratio of 1:3 to obtain a mixed solution. The mixed solution was added to a reaction vessel, and 1 mmol HOBt, 1 mmol EDC·HCl and 0.85 mmol triethylamine were added sequentially under magnetic stirring (200 r / min). The reaction was carried out under nitrogen atmosphere and room temperature for 15 h to obtain a modified branched polyamine polymer precursor. After the reaction was completed, the modified branched polyamine polymer precursor was separated and purified to obtain the main complexing agent modified branched polyamine polymer ③. 2. Add 160 g / L methanesulfonic acid to an appropriate amount of deionized water, and then add 30 g / L stannous ethyl sulfonate and 2.7 g / L copper ethanesulfonate in sequence while stirring. Stir until completely dissolved to obtain a tin-copper mixture. 3. Add 12 g / L of a combination of p-hydroxybenzoic acid and syringic acid, 3 g / L of hydroxypropyl chitosan and 0.2 g / L of 1,1'-di-n-octyl-4,4'-didibromopyridine to the above tin-copper mixture in sequence, 20 g / L of modified branched polyamine polymer ③, 0.6 g / L of 1-octadecyl mercaptan and 0.6 g / L of cysteine. After stirring and dissolving evenly, dilute to 1 L with deionized water, let stand for 1 h, and filter to obtain a pyrophosphate-free tin-copper co-plating solution. Example 4

[0098] 1. Branched polyethyleneimine with a molecular weight of 800 Da and 5-oxazolamide were mixed with 10 ml of N,N-dimethylformamide at a molar ratio of 1:3 to obtain a mixed solution. The mixed solution was added to a reaction vessel, and 1 mmol HOBt, 1 mmol EDC·HCl and 0.85 mmol triethylamine were added sequentially under magnetic stirring (200 r / min). The reaction was carried out under nitrogen atmosphere and room temperature for 12 h to obtain a modified branched polyamine polymer precursor. After the reaction was completed, the modified branched polyamine polymer precursor was separated and purified to obtain the main complexing agent modified branched polyamine polymer ④. 2. Add 160 g / L methanesulfonic acid to an appropriate amount of deionized water, and then add 20 g / L stannous methanesulfonate and 2.7 g / L copper methanesulfonate in sequence while stirring. Stir until completely dissolved to obtain a tin-copper mixture. 3. Add 15 g / L 2,5-dihydroxy-1,4-benzoquinone, 5 g / L ethylene glycol oligochitosan, 1.6 g / L N-octylpyridine bromide, 20 g / L modified branched polyamine polymer ④, 1.2 g / L mercapto-undecanamine hydrochloride and 0.8 g / L 1-eicosylthiol to the above tin-copper mixture in sequence. After stirring and dissolving evenly, dilute to 1 L with deionized water, let stand for 1 h, and filter to obtain a pyrophosphate-free tin-copper co-plating solution. Example 5

[0099] 1. Branched polyethyleneimine with a molecular weight of 800 Da and 2,4-dimethyloxazol-5-carboxylic acid were mixed with 10 ml of N,N-dimethylformamide at a molar ratio of 1:4 to obtain a mixed solution. The mixed solution was added to a reaction vessel, and 1 mmol HOBt, 1 mmol EDC·HCl, and 0.85 mmol triethylamine were added sequentially under magnetic stirring (200 r / min). The reaction was carried out under nitrogen atmosphere and room temperature for 12 h to obtain a modified branched polyamine polymer precursor. After the reaction was completed, the modified branched polyamine polymer precursor was separated and purified to obtain the main complexing agent modified branched polyamine polymer⑤. 2. Add 140 g / L methanesulfonic acid to an appropriate amount of deionized water, and then add 40 g / L stannous ethyl sulfonate and 2.1 g / L copper methanesulfonate in sequence while stirring. Stir until completely dissolved to obtain a tin-copper mixture. 3. Add 10 g / L of syringic acid and gallic acid combination, 6 g / L of oligochitosan and 1.0 g / L of N-octylpyridine bromide, 30 g / L of modified branched polyamine polymer⑤, 0.6 g / L of 1,4-dithiothreitol and 0.4 g / L of 1-eicosenethiol to the above tin-copper mixture in sequence. After stirring and dissolving evenly, dilute to 1 L with deionized water, let stand for 1 h, and filter to obtain a pyrophosphate-free tin-copper co-plating solution. Comparative Example 1 The difference from Example 1 is that the amount of the main complexing agent modified branched polyamine polymer in step 3 of Example 1 is reduced by 50%, while the rest remains unchanged.

[0100] Comparative Example 2 The difference from Example 2 is that the cationic surfactant (1-octadecyl-4-(4-phenyl-1,3-butadienyl)pyridine bromide) in step 3 of Example 2 is omitted, while the rest remains the same.

[0101] Comparative Example 3 The difference from Example 3 is that the brightening agent (1-octadecyl mercaptan and cysteine) in step 3 of Example 3 is omitted, while the rest remains the same.

[0102] Comparative Example 4 The difference from Example 4 is that the ethylene glycol oligochitosan in step 3 of Example 4 is omitted, while the rest remains the same.

[0103] Comparative Example 5 The difference from Example 5 is that copper methanesulfonate in step 2 of Example 5 is omitted, while the rest remains the same.

[0104] The pyrophosphate-free tin-copper co-plating solutions of the above embodiments and comparative examples were used according to the following application method for the plated parts, which included the following steps: (1) Perform pickling on the plated parts that have not undergone pretreatment. The pickling solution is of a certain concentration. The processing time was 30 seconds and the temperature was 20°C, resulting in the plated parts after pickling. (2) The plated parts after pickling are placed in a degreasing solution for degreasing treatment. The degreasing solution is 5% M401 and... The mixture was processed for 2 minutes at a temperature of 35°C to obtain the degreased plated parts. (3) Place the plated parts that have undergone degreasing treatment into a micro-etching solution for micro-etching treatment. The micro-etching solution has a concentration of A mixture of sodium persulfate and 40 g / L was used for 1 min at a temperature of 25 °C to obtain the pretreated plated part. (4) Prepare tin-copper co-plating solutions according to the preparation methods of each embodiment and comparative example. Place the dragging plate in the plating solution at 20°C and perform weak electrolysis with a current density of 5 ASF. Then, perform rough electroplating on the dragging plate for 30 minutes with a current density of 25 ASF and mechanical cathode oscillation stirring. After dragging the plate, perform electroplating on the pretreated plate for 15 minutes with a current density of 20 ASF and mechanical cathode oscillation stirring to obtain plated part A.

[0105] The tin-copper co-plated layers prepared in each embodiment and comparative example were subjected to tin whisker growth rate testing and tin-copper alloy content testing. The tin whisker growth rate test was conducted according to the JESD22-A121 test conditions of 60℃ / 87%RH for 4000h. If the observed tin whisker length was ≥50µm or a short circuit occurred, the layer was considered to have failed.

[0106] Table 1 Test Results As can be seen from the table above, because Examples 1-5 simultaneously used modified branched polyamine polymers and cationic oligosaccharide complexes, the amino ligands and nitrogen-oxygen mixed polydentate ligands in the modified branched polyamine polymers and cationic oligosaccharide complexes can pass through Cu 2+ The strong complexation allows for precise control of the high-tin, low-copper tin-copper co-plating process, enabling tin and copper to be reduced stably and continuously in a suitable ratio. This achieves uniform tin-copper co-deposition. In particular, the use of cationic oligosaccharide complexes, brighteners, and copper salts facilitates the formation of a tin-free, uniformly crystallized, smooth, dense, and well-stressed tin-copper co-plating layer with strong connectivity. This results in Examples 1-5 having significantly better overall performance than Comparative Examples 1-5. In Example 2, the tin-copper co-plating solution remained clear and transparent after being exposed to air for two weeks, exhibiting excellent stability and effectively avoiding the problems of rapid decomposition, high consumption, large content fluctuations, and high control difficulty associated with tin-copper co-plating solutions. Therefore, Example 2 achieved the best overall performance.

[0107] As can be seen from Example 1 and Comparative Example 1, since the amount of modified branched polyamine polymer ① added in Comparative Example 1 was reduced by 50%, the overall performance of Example 1 was significantly better than that of Comparative Example 1.

[0108] As can be seen from Example 2 and Comparative Example 2, since the cationic surfactant 1-octadecyl-4-(4-phenyl-1,3-butadienyl)pyridine bromide was not added to Comparative Example 2, the overall performance of Example 2 is significantly better than that of Comparative Example 2.

[0109] As can be seen from Example 3 and Comparative Example 3, since no brightener was added to Comparative Example 3, the overall performance of Example 3 is significantly better than that of Comparative Example 3.

[0110] As can be seen from Example 4 and Comparative Example 4, since no cationic oligosaccharide complex was added to Comparative Example 4, the overall performance of Example 4 is significantly better than that of Comparative Example 4.

[0111] As can be seen from Example 5 and Comparative Example 5, since copper methanesulfonate was not added to Comparative Example 5, the overall performance of Example 5 is significantly better than that of Comparative Example 5.

[0112] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A non-phosphate tin copper co-plating additive comprising a primary complexing agent and a secondary complexing agent, characterized in that, The primary complexing agent is a modified branched polyamine polymer, which is generated by reacting a branched polyamine polymer with an oxazolyl carboxylic acid compound. The modified branched polyamine polymer contains amino ligands and nitrogen-oxygen mixed polydentate ligands. The auxiliary complexing agent is a cationic oligosaccharide complex.

2. A non-phosphate-free tin copper co-plating additive according to claim 1, characterized in that, The branched polyamine polymer includes at least one of branched polyethyleneimine and branched polyamide; and / or, The branched polyamine polymer has a molecular weight of 600 Da-1000 Da.

3. The non-phosphate-free tin copper co-plating additive according to claim 1, characterized in that, The oxazolylcarboxylic acid compound comprises at least one selected from 2,4-dimethyloxazol-5-carboxylic acid, 5-oxazolcarboxylic acid, 3-(5-oxazolyl)benzoic acid, and 3-isooxazolcarboxylic acid; and / or, The molar ratio of the branched polyamine polymer to the oxazolyl carboxylic acid compound is 1:(3-4).

4. The non-phosphate tin copper co-plating additive according to claim 1, characterized in that, The cationic oligosaccharide complex includes at least two of the following: oligosaccharide ligands, oligosaccharide ligand derivatives, and cationic surfactants.

5. The pyrophosphate-free tin-copper co-plating additive according to claim 4, characterized in that, The oligosaccharide ligand has a molecular weight of 800 Da-1200 Da; and / or, The oligosaccharide ligand derivative has a molecular weight of 800 Da-1200 Da; and / or, The oligosaccharide ligand includes at least one selected from chitosan oligosaccharide, glucosamine oligosaccharide, galactosamine oligosaccharide, and mannosamine oligosaccharide; and / or, The oligosaccharide ligand derivative includes at least one of carboxymethyl oligochitosan, ethylene glycol oligochitosan, and oligogalactosamine; and / or, The cationic surfactant includes at least one of N-octadecyl-4-styrylpyridine bromide, 1-octadecyl-4-(4-phenyl-1,3-butadienyl)pyridine bromide, N-octylpyridine bromide, and 1,1'-di-n-octyl-4,4'-bidibromopyridine bromide.

6. A method for preparing a pyrophosphate-free tin-copper co-plating additive, characterized in that, Includes the following steps: A mixed solution is obtained by mixing a branched polyamine polymer, an oxazolyl carboxylic acid compound, and a polar aprotic solvent. A core condensing agent, a condensing aid, and an acid neutralizer are added to the mixed solution to carry out an amidation condensation reaction, thereby obtaining a modified branched polyamine polymer precursor. The modified branched polyamine polymer precursor was separated and purified to obtain the modified branched polyamine polymer.

7. The method for preparing the pyrophosphate-free tin-copper co-plating additive according to claim 6, characterized in that, The polar aprotic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, and dimethyl sulfoxide; and / or, The core condensing agent includes at least one of EDC·HCl, DDC, and DIC; and / or, The condensation aid includes at least one of HOAt, HOBt, OXyma Pure, and OXyma-B; and / or, The acid neutralizing agent includes at least one of triethylamine, N,N-diisopropylethylamine, N-methylmorpholine, and pyridine.

8. The method for preparing the pyrophosphate-free tin-copper co-plating additive according to claim 6, characterized in that, The step of adding a core condensing agent, a condensing aid, and an acid neutralizing agent to the mixed solution for an amidation condensation reaction includes the following specific steps: Under a nitrogen atmosphere and at room temperature, the mixture is added dropwise to a container, followed by the sequential addition of the core condensing agent, the condensation aid, and the acid neutralizing agent, and the reaction is continuously stirred for 12-20 hours; and / or, The step of separating and purifying the modified branched polyamine polymer precursor to obtain the modified branched polyamine polymer includes the following specific steps: The modified branched polyamine polymer precursor was added to a precipitant and then filtered to obtain a precipitate. The precipitate was subjected to precipitation washing and drying operations in sequence.

9. A pyrophosphate-free tin-copper co-plating solution, characterized in that, Based on mass concentration, it includes the following components: Stannous salts: 20 g / L - 60 g / L; Copper salt concentration: 1.5 g / L - 2.7 g / L; Main complexing agent 20g / L-40g / L; Auxiliary complexing agent 3.1g / L-10g / L; Brightening agent: 0.1g / L-2.0g / L; Antioxidant concentration: 8g / L-15g / L; Organic acids 120g / L-180g / L; Water balance; The main complexing agent is a modified branched polyamine polymer; The auxiliary complexing agent is a cationic oligosaccharide complex; The primary complexing agent and the secondary complexing agent constitute the pyrophosphate-free tin-copper co-plating additive according to any one of claims 1-5.

10. An application of the tin-copper co-plating solution as described in any one of claims 1-5 in a plated part.

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