Modified plant polyphenol-chitosan composite coated tin ball soldering material and preparation method thereof

Abstract

The application provides a modified plant polyphenol-chitosan composite coated tin ball welding material and a preparation method, and belongs to the technical field of electronic packaging materials. The modified plant polyphenol-chitosan composite coated tin ball welding material comprises a tin ball base body and a composite antioxidant layer coated on the surface of the tin ball base body; the composite antioxidant layer is composed of quaternary ammonium quercetin nanocrystals, carboxymethyl chitosan and silane coupling agent modified nano-SiO2. The composite coated tin ball has excellent and durable antioxidant performance, strong coating adhesion and stable structure, the coating adhesion can reach 1.3-1.8 MPa, has good weldability and is environment-friendly and non-polluting, and solves the pain point that the existing coating is difficult to have both antioxidant performance and weldability.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials technology, and in particular to a modified plant polyphenol-chitosan composite coated solder ball soldering material and its preparation method. Background Technology

[0002] Solder balls, as a core welding material in the field of electronic packaging, are widely used in chip interconnection, printed circuit board assembly, and other scenarios. However, tin is chemically reactive, and its surface is easily oxidized to form oxide films such as SnO and SnO2 during room temperature storage or high-temperature soldering. This leads to decreased solder wettability and reduced joint strength, seriously affecting the reliability and lifespan of electronic devices. As electronic devices develop towards higher density and miniaturization, higher requirements are placed on the oxidation resistance and soldering performance of solder balls, and traditional protection solutions are no longer sufficient to meet practical application needs.

[0003] To solve the problem of solder ball oxidation, the existing technologies mainly adopt the following solutions: (1) Alloying modification, adding elements such as Ag, Cu, and Ni to tin to improve oxidation resistance, but this will increase production costs and may affect the welding melting point, resulting in a narrowing of the welding process window; (2) Inorganic coating, such as SiO2 and TiO2, although they have strong barrier properties, the coating is brittle and has poor adhesion, and is easy to fall off during the welding process, and it is difficult to achieve uniform coating of thin coatings; (3) Organic coating, such as epoxy resin and polylactic acid, although they have good flexibility, they are not environmentally friendly and are difficult to degrade, and are easy to decompose at high temperatures to produce harmful substances, polluting the welding environment and affecting the joint quality; (4) Natural polymer coating, such as chitosan-tannic acid composite coating, has green and environmentally friendly advantages, but the existing solutions are mostly simple physical mixing, which has defects such as low coating density, insufficient adhesion, and poor oxidation resistance and durability, and the coating is not completely decomposed at the welding temperature, which easily affects the solder ball's welding wettability and joint strength.

[0004] Both plant polyphenols and chitosan are natural biomass materials, characterized by their non-toxicity, biodegradability, and environmental friendliness. The catechol / pyrogallol structure in plant polyphenols can scavenge oxygen free radicals and inhibit oxidative chain reactions; the amino and hydroxyl groups in chitosan molecules can form a dense film layer, blocking oxygen and moisture. However, in existing technologies, the composites of plant polyphenols and chitosan are mostly physical blends with weak interfacial forces and a lack of targeted material modification, resulting in coating performance that fails to meet the comprehensive requirements of electronic packaging for solder ball oxidation resistance, solderability, and adhesion. Furthermore, while composite systems of carboxymethyl chitosan and nano-SiO2 exist in existing technologies (such as food packaging films and medical coatings), these systems do not address the specific requirements of electronic packaging scenarios (such as rapid high-temperature decomposition, no impact on solderability, and uniform thin-coating coverage), and therefore cannot be directly applied to solder ball protection. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing solder ball coatings, such as insufficient antioxidant properties, poor adhesion, poor environmental performance, or impact on solderability, and to provide a modified plant polyphenol-chitosan composite coated solder ball soldering material and its preparation method. By chemically modifying plant polyphenols and chitosan, introducing inorganic nanofillers, and employing a layer-by-layer self-assembly process, a composite coating with synergistic effects of "modified polyphenols-modified chitosan-nanofillers" is constructed. This achieves simultaneous improvement in antioxidant properties, adhesion, and solderability, and the preparation process is green, mild, and suitable for industrialization.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One of the technical solutions of the present invention is a modified plant polyphenol-chitosan composite coated solder ball welding material, comprising a solder ball substrate and a composite antioxidant layer coated on the surface of the solder ball substrate; the composite antioxidant layer is composed of quaternized quercetin nanocrystals, carboxymethylated chitosan and silane coupling agent modified nano-SiO2.

[0008] In this invention, the synergistic mechanism of quaternized quercetin nanocrystals, carboxymethylated chitosan and silane coupling agent modified nano-SiO2 is as follows: (1) Electrostatic interaction: The cationic groups of quaternized quercetin nanocrystals and the carboxyl anions of carboxymethylated chitosan form a strong electrostatic interaction, which makes the coating components tightly bonded and improves the coating density; (2) Chemical bonding: The amino groups on the surface of silane coupling agent modified nano-SiO2 form hydrogen bonds with the hydroxyl / carboxyl groups of quaternized quercetin nanocrystals and carboxymethylated chitosan, and at the same time form covalent bonds with the hydroxyl groups on the surface of the tin ball, which significantly enhances the interfacial bonding force between the coating and the substrate; (3) Pore filling: Nano-SiO2 fills the pores inside the coating, reduces the penetration channels of oxygen and moisture, and forms a double barrier with the dense film layer of modified chitosan, which synergistically improves the antioxidant performance.

[0009] The second technical solution of the present invention is a method for preparing the above-mentioned modified plant polyphenol-chitosan composite coated solder ball welding material, comprising the following steps:

[0010] Carboxymethylated chitosan was dissolved in water to prepare a carboxymethylated chitosan solution;

[0011] Quaternized quercetin nanocrystals and silane coupling agent-modified nano-SiO2 were added to the carboxymethylated chitosan solution and stirred evenly to obtain a composite antioxidant liquid layer.

[0012] The tin ball matrix is ​​dispersed in the composite antioxidant liquid, stirred and adsorbed, then washed and dried to obtain the modified plant polyphenol-chitosan composite coated tin ball welding material.

[0013] The present invention discloses the following technical effects:

[0014] (1) Excellent antioxidant properties and strong durability: The pyrogallol structure of quaternized quercetin nanocrystals can efficiently scavenge oxygen free radicals, the dense film layer formed by carboxymethylated chitosan blocks oxygen and moisture, and the inorganic nanofiller fills the pores of the coating. The three work synergistically to significantly improve the antioxidant durability of the solder balls. According to the test, the oxidation induction time of the composite coated solder balls of the present invention can reach 110-150h under the thermal aging condition of 150℃, which is far better than that of uncoated solder balls (compared with conventional chitosan-tannic acid coated solder balls (<40h)); after 6 months of storage at room temperature, the oxide film thickness is ≤0.1μm, while the oxide film thickness of conventional coated solder balls is ≥0.3μm and the oxide film thickness of uncoated solder balls is ≥0.8μm.

[0015] (2) Strong coating adhesion and stable structure: The cations of quaternized quercetin nanocrystals and the anions of carboxymethylated chitosan form a strong electrostatic interaction. The nano-SiO2 modified by silane coupling agent forms chemical bonds with the modified polyphenols, modified chitosan and the surface of the tin balls, significantly improving the interfacial bonding force. The coating adhesion can reach 1.3-1.8 MPa by pull-off test, which is 1.6-2.2 times that of conventional chitosan-tannic acid coating (0.8 MPa). Moreover, there is no peeling or cracking after ultrasonic oscillation (200W, 30min, 40kHz).

[0016] (3) Excellent solderability and environmentally friendly: The composite coating has a thermal decomposition rate of ≥95% at a welding temperature of 230-260℃, and the mass fraction of thermal decomposition residue is ≤0.5%, with no harmful residues. It does not affect the wettability of the solder balls (wetting time 1.6-2.0s, comparable to uncoated solder balls). The strength of the welded joint decreases by ≤5% compared to uncoated solder balls, solving the pain point of existing coatings that "difficult to balance oxidation resistance and solderability".

[0017] (4) Green and environmentally friendly with strong compatibility: The raw materials are all natural biomass materials and inorganic nanofillers. The preparation process adopts an aqueous system, without the addition of toxic organic solvents. The coating is degradable and meets the environmental protection requirements of electronic materials. The coating thickness is only 0.5-3μm, which does not affect the dimensional accuracy of the solder balls and the compatibility of subsequent packaging processes.

[0018] (5) The process is simple, controllable and suitable for industrialization: conventional equipment such as ultrasonic cleaning, centrifugal separation and vacuum drying are used, without the need for special customized equipment. The operation is simple and the cost is low. The layer-by-layer self-assembly process can achieve precise control of coating thickness, which is suitable for large-scale production and the production efficiency can reach more than 10kg / h. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the modified plant polyphenol-chitosan composite coated solder ball welding material of the present invention, wherein a is a SEM image of the solder ball body, b is a SEM image of the composite coated solder ball, and c is a schematic diagram of the structure of the composite coated solder ball.

[0021] Figure 2 This is a comparison chart of the thermal aging oxidation induction time of Examples 1, 2, and 3 of the present invention and Comparative Examples 1, 2, and 3;

[0022] Figure 3 The images shown are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) spectra of the composite antioxidant layer in Embodiment 1 of the present invention; wherein, a is the surface morphology of the coating, b and c are high-magnification morphology images, and d is the energy dispersive spectroscopy of the elemental distribution.

[0023] Figure 4 The images show the scanning electron microscope (SEM) image and energy dispersive spectroscopy (EDS) spectrum of the solder ball in Comparative Example 1; where a is the surface morphology of the solder ball, b and c are high-magnification morphology images, and d is the elemental analysis result of the solder ball. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] The first aspect of the present invention provides a modified plant polyphenol-chitosan composite coated solder ball welding material, comprising a solder ball substrate and a composite antioxidant layer coated on the surface of the solder ball substrate; the composite antioxidant layer is composed of quaternized quercetin nanocrystals, carboxymethylated chitosan and silane coupling agent modified nano-SiO2.

[0030] In this invention, (1) Quaternized quercetin nanocrystals: Quaternization modification of quercetin can improve its water solubility and cationicity, forming a stronger electrostatic interaction with anionic modified chitosan. Nano-processing can increase the specific surface area and improve the antioxidant efficiency; (2) Carboxymethylated chitosan: Carboxymethylation modification can improve the water solubility and film-forming properties of chitosan and improve the coating density; (3) Silane coupling agent modified nano-SiO2: Modified nano-SiO2 can form hydrogen bonds and covalent bonds with quaternized quercetin nanocrystals and carboxymethylated chitosan, enhancing the structural stability and barrier properties of the coating. Specifically, quaternized quercetin nanocrystals and carboxymethylated chitosan are combined through electrostatic interaction. Modified nano-SiO2 fills the pores of the composite antioxidant layer and forms chemical bonds with both quaternized quercetin nanocrystals and carboxymethylated chitosan and the tin ball matrix, forming a synergistic antioxidant system of "electrostatic interaction-chemical bonding-pore filling".

[0031] In this invention, the composite antioxidant layer has a thermal decomposition rate of ≥95% at 230-260℃ and a thermal decomposition residue mass fraction of ≤0.5%.

[0032] In a preferred embodiment of the present invention, the thickness of the composite antioxidant layer is 0.5-3 μm, and the particle size of the tin ball substrate is 0.1-1 mm.

[0033] In a preferred embodiment of the present invention, the mass ratio of the quaternized quercetin nanocrystals to carboxymethylated chitosan is (1-8):(1-10), and the mass ratio of the quaternized quercetin nanocrystals to silane coupling agent modified nano-SiO2 is (1-8):(1-4).

[0034] More preferably, the mass ratio of the quaternized quercetin nanocrystals to carboxymethylated chitosan is 1:10, 2:9, 3:5, 4:5, 5:7, 5:8, or 6:7.

[0035] More preferably, the mass ratio of the quaternized quercetin nanocrystals to the silane coupling agent modified nano-SiO2 is 1:1, 2:1, 5:2, 3:1, 5:3 or 7:4.

[0036] In a preferred embodiment of the present invention, the quaternized quercetin nanocrystals have a particle size of 50-200 nm and a degree of quaternization of 0.3-0.6.

[0037] More preferably, the method for preparing the quaternized quercetin nanocrystals is as follows:

[0038] Quercetin was dissolved in ethanol, and then 3-chloro-2-hydroxypropyltrimethylammonium chloride was added. The mixture was reacted at 60-80°C under alkaline conditions for 4-6 hours. After purification by dialysis, the nanocrystals were obtained by nano-sizing using a high-pressure homogenizer. The mass ratio of quercetin to 3-chloro-2-hydroxypropyltrimethylammonium chloride was 10:6-8; the molecular weight cutoff during dialysis purification was 8000-14000 Da; and the pressure during nano-sizing using the high-pressure homogenizer was 80-120 MPa.

[0039] In a preferred embodiment of the present invention, the degree of substitution of the carboxymethylated chitosan is 0.5-0.8, and the molecular weight is 50,000-150,000 Da.

[0040] More preferably, the method for preparing the carboxymethylated chitosan is as follows:

[0041] Chitosan was dispersed in isopropanol, and chloroacetic acid and sodium hydroxide were added. The mixture was then etherified at 50-70°C for 3-5 hours. After neutralization to pH 6-7, the mixture was washed and dried to obtain carboxymethylated chitosan. The molar ratio of chitosan to chloroacetic acid and sodium hydroxide was 1:1.5-2.5:2-3.

[0042] In a preferred embodiment of the present invention, the particle size of the silane coupling agent modified nano-SiO2 is 20-100 nm, and the grafting rate of the silane coupling agent is 10%-25%; the silane coupling agent is silane coupling agent KH-550.

[0043] More preferably, the method for preparing the silane coupling agent modified nano-SiO2 is as follows:

[0044] Nano-SiO2 was dispersed in an ethanol-water solution, and a silane coupling agent was added. The mixture was stirred and reacted at 40-60℃ for 2-3 hours. After centrifugation and drying, silane coupling agent-modified nano-SiO2 was obtained. In the ethanol-water solution, the volume ratio of ethanol to water was 1:1; the mass ratio of nano-SiO2 to silane coupling agent was 10:1-3; and the drying temperature was 80-90℃ for 2-3 hours.

[0045] A schematic diagram of the modified plant polyphenol-chitosan composite coated solder ball soldering material of the present invention is shown below. Figure 1 As shown, a is the SEM image of the solder ball body, b is the SEM image of the composite coated solder ball, and c is the structural schematic diagram of the composite coated solder ball.

[0046] A second aspect of the present invention provides a method for preparing the above-mentioned modified plant polyphenol-chitosan composite coated solder ball welding material, comprising the following steps:

[0047] Carboxymethylated chitosan was dissolved in water to prepare a carboxymethylated chitosan solution;

[0048] Quaternized quercetin nanocrystals and silane coupling agent-modified nano-SiO2 were added to the carboxymethylated chitosan solution and stirred evenly to obtain a composite antioxidant liquid layer.

[0049] The tin ball matrix is ​​dispersed in the composite antioxidant liquid, stirred and adsorbed, then washed and dried to obtain the modified plant polyphenol-chitosan composite coated tin ball welding material.

[0050] In a preferred embodiment of the present invention, the concentration of the carboxymethylated chitosan solution is 1wt%-3wt%.

[0051] In a preferred embodiment of the present invention, the stirring parameters for uniform stirring are set as follows: stirring at 30-40℃ and 400-600r / min for 30-60min.

[0052] In a preferred embodiment of the present invention, the zeta potential of the composite antioxidant layer is -10 to +5 mV. The present invention achieves the final zeta potential of the composite antioxidant layer by adjusting the concentration of the carboxymethylated chitosan solution, the ratio of carboxymethylated chitosan to quaternized quercetin nanocrystals and silane coupling agent-modified nano-SiO2, and the pH of the composite antioxidant layer. When the zeta potential of the composite antioxidant layer is in the range of -10 to +5 mV, it ensures that the components are uniformly dispersed and form a stable system, avoiding aggregation.

[0053] Preferably, the reagent for adjusting the pH is a hydrochloric acid solution or a sodium hydroxide solution; the concentration of the hydrochloric acid solution is 0.1-0.5 mol / L, and the concentration of the sodium hydroxide solution is 0.1-0.5 mol / L.

[0054] Preferably, the pH is adjusted to 5.0-6.0.

[0055] In a preferred embodiment of the present invention, before dispersing the solder ball substrate in the composite antioxidant liquid, a pretreatment step of the solder ball substrate is further included; the pretreatment is as follows: the solder ball substrate is ultrasonically cleaned in a mixed solution of ethanol and water, and then dried to constant weight at 60-80°C under a protective atmosphere. The volume ratio of ethanol to water is (1-3):1; the ultrasonic power is 100-200W, the ultrasonic frequency is 20-40kHz; and the heating rate during drying is 5-10°C / min.

[0056] This invention uses an ethanol-water mixed solution for ultrasonic cleaning, which can effectively remove surface oil and oxide layers without damaging the solder ball substrate. Precise control of ultrasonic frequency and power can prevent microcracks from forming on the surface of the solder balls.

[0057] This invention controls the heating rate to prevent bubbles and cracks from forming in the coating during the drying process due to a sudden temperature rise, thus ensuring the coating's density.

[0058] In a preferred embodiment of the present invention, the solder ball substrate is dispersed in the composite antioxidant layer solution and adsorbed by stirring. Specifically, the solder ball substrate is dispersed in the composite antioxidant layer solution, stirred for adsorption, and then centrifuged to obtain initially coated solder balls. The initially coated solder balls are then dispersed again in a newly prepared composite antioxidant layer solution, and the adsorption-separation operation is repeated. After each adsorption-separation operation, the coating thickness increases by 0.2-0.8 μm, until the thickness of the composite antioxidant layer is 0.5-3 μm. The stirring adsorption temperature is 25-35℃, and the time is 20-40 min. The stirring speed during stirring adsorption is 200-300 r / min. The centrifugation speed is 3000-5000 r / min, and the time is 5-10 min. The present invention, through multiple adsorption-separation operations, can precisely control the thickness of the composite antioxidant layer and simultaneously improve the interfacial bonding force between the coating and the solder ball substrate.

[0059] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0060] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0061] In this embodiment, the preparation steps of quaternized quercetin nanocrystals are as follows:

[0062] 10g of quercetin was dissolved in 100mL of ethanol, and 8g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added. The pH was adjusted to 8.5 with 1mol / L sodium hydroxide solution, and the mixture was stirred at 70℃ for 5h. The reaction solution was transferred to a dialysis bag (molecular weight cutoff 10000Da), and dialyzed with deionized water for 3 days, with the dialysate changed twice a day. The dialyzed solution was then added to a high-pressure homogenizer and homogenized 3 times at 100MPa pressure to obtain quaternized quercetin nanocrystals (particle size 100nm, degree of quaternization substitution 0.4).

[0063] The preparation steps of carboxymethylated chitosan are as follows:

[0064] 10g of chitosan was dispersed in 100mL of isopropanol, 12g of chloroacetic acid and 8g of sodium hydroxide were added, and the mixture was stirred at 60℃ for 4h. After the reaction was completed, the mixture was neutralized to pH=6.5 with 1mol / L hydrochloric acid, the solid was collected by filtration, washed 3 times with ethanol, and dried in a vacuum drying oven at 60℃ for 8h to obtain carboxymethylated chitosan (degree of substitution 0.6, molecular weight 100000Da).

[0065] The preparation steps of silane coupling agent modified nano-SiO2 are as follows:

[0066] 20g of nano-SiO2 (particle size 50nm) was dispersed in 200mL of ethanol aqueous solution (ethanol to water volume ratio 1:1), 4g of KH-550 was added, and the mixture was stirred at 50℃ for 2.5h. The solid was collected by centrifugation (4000r / min, 10 min) and dried at 80℃ for 2h to obtain KH-550 modified nano-SiO2 (grafting rate 18%).

[0067] Example 1

[0068] (1) Pretreatment of solder balls: Select pure solder balls with a particle size of 0.3 mm, place them in a mixed solution of ethanol and deionized water in a volume ratio of 1:1, and ultrasonically clean them at 150 W and 30 kHz for 20 min. Then dry them at 70 °C under a nitrogen atmosphere to constant weight to obtain pretreated solder balls.

[0069] (2) Preparation of composite antioxidant layer solution: Dissolve the carboxymethylated chitosan prepared above in deionized water and stir until completely dissolved to obtain a carboxymethylated chitosan solution with a mass concentration of 2wt%; add quaternized quercetin nanocrystals and KH-550 modified nano-SiO2 to the carboxymethylated chitosan solution, wherein the mass ratio of quaternized quercetin nanocrystals, carboxymethylated chitosan and KH-550 modified nano-SiO2 is 5:8:2, stir for 45 min at 35℃ and 500 r / min, adjust the pH to 5.5 with 0.3 mol / L hydrochloric acid solution, and measure the zeta potential to be -2 mV to obtain the composite antioxidant layer solution;

[0070] (3) Layer-by-layer self-assembly coating: The pretreated tin balls are dispersed in the composite antioxidant layer solution and stirred and adsorbed for 30 min at 30℃ and 250 r / min. Then, they are centrifuged at 4000 r / min for 8 min to obtain the initial coated tin balls. The initial coated tin balls are dispersed again in the newly prepared composite antioxidant layer solution (the newly prepared composite antioxidant layer solution is the same as the composite antioxidant layer solution prepared in step 2). The adsorption-separation operation is repeated 3 times. After each adsorption, the coating thickness increases by 0.5 μm, 0.4 μm and 0.6 μm respectively.

[0071] (4) Post-treatment: The multilayer coated solder balls are washed three times with deionized water and dried in a vacuum drying oven at a vacuum degree of -0.09MPa and 80℃ for 3h at a heating rate of 8℃ / min to obtain composite coated solder balls with a composite anti-oxidation coating thickness of 1.5μm.

[0072] Figure 3 The images show scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) spectra of the composite coating in Example 1 of this invention. Image a shows the surface morphology of the coating, which is smooth and dense with no obvious pores. Images b and c are high-magnification morphology images, showing a tight bond between the coating and the tin ball substrate, and a uniform coating thickness of approximately 1.5 μm.

[0073] Table 1 and Figure 3 The elemental analysis results of the composite coating in d show that the surface-modified coating has successfully coated the tin balls, forming a composite phase with antioxidant stability.

[0074] Table 1 Elemental Analysis of Composite Coated Solder Balls

[0075] Example 2

[0076] (1) Pretreatment of solder balls: Select pure solder balls with a particle size of 0.5 mm, place them in a mixed solution of ethanol and deionized water with a volume ratio of 2:1, and ultrasonically clean them at 100 W and 25 kHz for 25 min. Then dry them at 60 °C under a nitrogen atmosphere to constant weight to obtain pretreated solder balls.

[0077] (2) Preparation of composite antioxidant layer solution: Dissolve carboxymethylated chitosan in deionized water and stir until completely dissolved to obtain a carboxymethylated chitosan solution with a mass concentration of 1wt%; add quaternized quercetin nanocrystals and KH-550 modified nano-SiO2 to the carboxymethylated chitosan solution, wherein the mass ratio of modified plant polyphenols, modified chitosan and inorganic nanofiller is 3:5:1, stir for 60 min at 30℃ and 400 r / min, adjust the pH to 5.0 with 0.1 mol / L hydrochloric acid solution, and measure the zeta potential to be -5 mV to obtain the composite antioxidant layer solution;

[0078] (3) Layer-by-layer self-assembly coating: The pretreated tin balls are dispersed in the composite antioxidant layer solution and stirred and adsorbed at 25℃ and 200r / min for 40min. Then, they are centrifuged at 3000r / min for 10min to obtain the initial coated tin balls. The initial coated tin balls are dispersed again in the newly prepared composite antioxidant layer solution (the newly prepared composite antioxidant layer solution is the same as the composite antioxidant layer solution prepared in step 2). The adsorption-separation operation is repeated twice. After each adsorption, the coating thickness increases by 0.3μm and 0.5μm respectively.

[0079] (4) Post-treatment: The multilayer coated tin balls are washed twice with deionized water and dried in a vacuum drying oven at a vacuum degree of -0.08MPa and 70℃ for 4h at a heating rate of 5℃ / min to obtain composite coated tin balls with a composite anti-oxidation coating thickness of 0.8μm.

[0080] Example 3

[0081] (1) Pretreatment of solder balls: Select pure solder balls with a particle size of 0.8 mm, place them in a mixed solution of ethanol and deionized water in a volume ratio of 3:1, and ultrasonically clean them at 200 W and 35 kHz for 15 min. Then dry them at 80 °C under a nitrogen atmosphere to constant weight to obtain pretreated solder balls.

[0082] (2) Preparation of composite antioxidant layer solution: Dissolve carboxymethylated chitosan in deionized water and stir until completely dissolved to obtain a carboxymethylated chitosan solution with a mass concentration of 3wt%; add quaternized quercetin nanocrystals and KH-550 modified nano-SiO2 to the carboxymethylated chitosan solution, wherein the mass ratio of modified plant polyphenols, modified chitosan and inorganic nanofiller is 8:10:4, stir for 30 min at 40℃ and 600r / min, adjust the pH to 6.0 with 0.5mol / L sodium hydroxide solution, and measure the zeta potential of the coating solution to be +3mV to obtain the composite antioxidant layer solution;

[0083] (3) Layer-by-layer self-assembly coating: The pretreated tin balls are dispersed in the composite antioxidant layer solution and stirred and adsorbed for 20 min at 35℃ and 300 r / min. Then, they are centrifuged at 5000 r / min for 5 min to obtain the initial coated tin balls. The initial coated tin balls are dispersed again in the newly prepared composite antioxidant layer solution (the newly prepared composite antioxidant layer solution is the same as the composite antioxidant layer solution prepared in step 2). The adsorption-separation operation is repeated 4 times. After each adsorption, the coating thickness increases by 0.4 μm, 0.5 μm, 0.6 μm and 1.0 μm respectively.

[0084] (4) Post-treatment: The multilayer coated solder balls are washed three times with deionized water and dried in a vacuum drying oven at a vacuum degree of -0.1MPa and 90℃ for 2 hours at a heating rate of 10℃ / min to obtain composite coated solder balls with a composite anti-oxidation coating thickness of 2.5μm.

[0085] Comparative Example 1

[0086] Pure tin balls with the same particle size as in Example 1 were selected and used directly as Comparative Example 1 without any coating treatment.

[0087] Figure 4 The images show scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) spectra of the solder balls in Comparative Example 1 of this invention. Image a shows the surface morphology of the solder balls, revealing good sphericity and a particle size of approximately 300 μm. Images b and c are high-magnification morphology images, showing a relatively smooth overall surface of the solder balls, but with a small number of pores and defects. Table 2 and... Figure 4 In the figure, 'd' represents the elemental analysis results of the solder balls. The uncoated solder balls are SnPb alloys, and oxygen was detected on their surface, indicating that they are prone to oxidation and deterioration when exposed to air. Therefore, preparing an antioxidant coating on the surface of the solder balls is of great significance and can effectively improve their stability during transportation and storage.

[0088] Table 2 Elemental Analysis of Uncoated Solder Balls

[0089] Comparative Example 2

[0090] Conventional chitosan-tannic acid coated tin balls were prepared according to existing technology: chitosan was dissolved in 1wt% acetic acid solution to prepare a chitosan mass concentration of 2wt%, and then tannic acid (chitosan to tannic acid mass ratio 2:1) was added and stirred evenly to obtain a coating solution; after ultrasonic cleaning with ethanol, the tin balls were immersed in the coating solution for 30 min, and then dried at 60℃ for 2 h to obtain coated tin balls with a coating thickness of about 1.5 μm.

[0091] Comparative Example 3

[0092] The only difference from Example 1 is that quaternized quercetin nanocrystals are replaced with quercetin, carboxymethylated chitosan is replaced with chitosan, and KH-550 modified nano-SiO2 is replaced with nano-SiO2. Furthermore, the mass ratio of quercetin, chitosan, and nano-SiO2 is 5:8:2. All other steps and parameters are the same as in Example 1. Coated tin balls were prepared with a coating thickness of approximately 1.5 μm.

[0093] Performance testing

[0094] The solder balls of Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests, and the results are shown in Table 3. The comparison chart of thermal aging oxidation induction time is shown in the figure below. Figure 2 As shown, Figure 2 The horizontal axis represents the sample type, and the vertical axis represents the oxidation induction time (h). Figure 2 The text clearly demonstrates that the oxidation induction time in Example 1 of the present invention is significantly longer than that in the comparative examples:

[0095] (1) Antioxidant performance: The tin balls were placed in a 150℃ oven and the surface oxidation degree was tested periodically. The oxidation induction time (the time when the surface oxide film thickness reached 0.5μm) was recorded. After 6 months of storage at room temperature, the oxide film thickness was tested by X-ray photoelectron spectroscopy (XPS).

[0096] (2) Coating adhesion: The pull-off test was conducted according to GB / T 5210-2006 standard to determine the bonding strength between the coating and the solder ball substrate; at the same time, an ultrasonic oscillation test (200W, 30min, 40kHz) was performed to observe the coating peeling.

[0097] (3) Solderability: Wetting performance (wetting time) was tested using the wetting balance method at a soldering temperature of 250℃. The shear strength of the solder joint was tested according to GB / T 11364-2008 standard, and the strength retention rate was calculated (compared with the uncoated solder ball). Thermogravimetric analysis (TGA) was used to test the thermal decomposition rate of the coating at 230-260℃.

[0098] (4) Long-term stability: The solder balls were stored in a constant temperature and humidity chamber at 40℃ and 85% relative humidity for 6 months, and the changes in oxide film thickness and welding performance were tested.

[0099] Table 3 Performance Test Results

[0100] As shown in Table 3, the composite-coated solder balls of Examples 1-3 of this invention are significantly superior to Comparative Example 1 (uncoated solder balls), Comparative Example 2 (conventional chitosan-tannic acid coated solder balls), and Comparative Example 3 (unmodified composite-coated solder balls) in terms of oxidation induction time, room temperature storage stability, coating adhesion, and solder joint strength retention rate. Specifically, the oxidation induction time of Example 1 is 3.86 times that of Comparative Example 2 and 2.08 times that of Comparative Example 3; the coating adhesion is 2 times that of Comparative Example 2 and 1.78 times that of Comparative Example 3; and the thermal decomposition rate at 250℃ exceeds 96%, far higher than that of Comparative Examples 2 and 3. This demonstrates that the technical solution of this invention achieves simultaneous improvement in oxidation resistance, adhesion, and solderability through material modification and synergistic design.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A modified plant polyphenol-chitosan composite coated solder ball welding material, characterized in that, It includes a tin ball substrate and a composite antioxidant layer coated on the surface of the tin ball substrate; the composite antioxidant layer is composed of quaternized quercetin nanocrystals, carboxymethylated chitosan and silane coupling agent modified nano-SiO2.

2. The modified plant polyphenol-chitosan composite coated solder ball welding material according to claim 1, characterized in that, The thickness of the composite antioxidant layer is 0.5-3 μm, and the particle size of the tin ball substrate is 0.1-1 mm.

3. The modified plant polyphenol-chitosan composite coated solder ball welding material according to claim 1, characterized in that, The mass ratio of the quaternized quercetin nanocrystals to carboxymethylated chitosan is (1-8):(1-10), and the mass ratio of the quaternized quercetin nanocrystals to silane coupling agent modified nano-SiO2 is (1-8):(1-4).

4. The modified plant polyphenol-chitosan composite coated solder ball welding material according to claim 1, characterized in that, The quaternized quercetin nanocrystals have a particle size of 50-200 nm and a degree of quaternization of 0.3-0.

6.

5. The modified plant polyphenol-chitosan composite coated solder ball welding material according to claim 1, characterized in that, The degree of substitution of the carboxymethylated chitosan is 0.5-0.8, and the molecular weight is 50,000-150,000 Da.

6. The modified plant polyphenol-chitosan composite coated solder ball welding material according to claim 1, characterized in that, The particle size of the silane coupling agent modified nano-SiO2 is 20-100nm, and the grafting rate of the silane coupling agent is 10%-25%; the silane coupling agent is silane coupling agent KH-550.

7. The preparation method of the modified plant polyphenol-chitosan composite coated solder ball soldering material as described in claim 1, characterized in that, Includes the following steps: Carboxymethylated chitosan was dissolved in water to prepare a carboxymethylated chitosan solution; Quaternized quercetin nanocrystals and silane coupling agent-modified nano-SiO2 were added to the carboxymethylated chitosan solution and stirred evenly to obtain a composite antioxidant liquid layer. The tin ball matrix is ​​dispersed in the composite antioxidant liquid, stirred and adsorbed, then washed and dried to obtain the modified plant polyphenol-chitosan composite coated tin ball welding material.

8. The preparation method according to claim 7, characterized in that, The concentration of the carboxymethylated chitosan solution is 1wt%-3wt%.

9. The preparation method according to claim 7, characterized in that, The zeta potential of the composite antioxidant liquid layer is -10 to +5 mV.

10. The preparation method according to claim 7, characterized in that, Before dispersing the solder ball substrate in the composite antioxidant liquid, the process further includes a pretreatment step for the solder ball substrate; the pretreatment involves ultrasonically cleaning the solder ball substrate in a mixed solution of ethanol and water, and then drying it to constant weight at 60-80°C under a protective atmosphere.

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