A water-based defluxing cleaning agent for PCBA board SMT process

Abstract

The application discloses a water-based deflux cleaning agent for SMT process of a PCBA board, and the raw material composition of the cleaning agent is as follows: 5-20% of organic amine, 20-40% of organic alcohol ether solvent, 1-10% of polar solvent, 0-5% of organic chelating agent, 0.1-5% of rosin-based block polyether phosphate ester sodium salt surfactant and 30-50% of deionized water, with the sum of the mass percentages being 100%. Compared with a traditional deflux cleaning agent, the prepared cleaning agent has the advantages of strong penetration and wetting performance, high ion removal effect, a wide process window, no halogen element and the like, can greatly improve the cleanliness and long-term use reliability of the PCBA, and meets the production requirements of environmental protection and high reliability in a high-end electronic industry.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor SMT process, specifically relating to a water-based deflux cleaning agent for PCBA board SMT process. Background Technology

[0002] Surface Mount Technology (SMT) is an electronic assembly process that directly mounts leadless / short-lead microchip components onto PCB pads using solder paste bonding and reflow soldering. It is widely used in PCBA motherboards, automotive electronics, new energy, communications, and consumer electronics. However, residual flux in the SMT process can absorb moisture and ionize under alternating temperature and humidity conditions, leading to decreased insulation resistance, electrochemical migration, copper dendrite short circuits, and white spots on solder joints. This directly causes long-term failures in high-reliability products such as automotive electronics, power modules, medical devices, and communications. Therefore, to ensure high reliability, stable electrical performance, and long service life of PCBAs, improve PCBA appearance quality and yield, and avoid contaminant contamination and the resulting electromigration and electrochemical corrosion that cause circuit failures, it is necessary to clean the PCBA after the soldering process, removing solder paste residue, flux residue, oil, dust, pad oxide layers, fingerprints, organic contaminants, and particles.

[0003] Flux cleaning is a core process following SMT reflow soldering, wave soldering, and rework. It uses specialized cleaning agents to remove flux residue, rosin resin, organic acid activators, solder paste oxide residue, ultrafine copper powder particles, and metallic soap-based contaminants from the PCBA board surface, component bottoms, and micro-gap areas. Early DEFLUX cleaning agents used trichloroethane, CFCs, and other halogenated hydrocarbons, relying on solvents to dissolve rosin resin. While these agents offered strong cleaning power and fast drying, they were high in VOCs, highly toxic, flammable, and explosive, and depleted the ozone layer; therefore, they have been completely phased out of mass production lines. Currently, most mainstream DEFLUX cleaning agents on the market use water-based systems with deionized water and organic solvents as carriers. These cleaning agents offer advantages such as environmental friendliness, safety, and low overall cost, but they also generally have the following shortcomings: ① Poor penetrability of the cleaning solution, resulting in poor cleaning of rosin and adhesive residues in blind holes and crevices on components. They are particularly ineffective at cleaning the capillary resistance in the 50-200µm micro-gap of FC flip chips, ultra-fine pitch BGAs, and 01005 micro-components. To address this, patent CN 111892995A provides a novel, highly efficient flux cleaning agent for chip packaging processes, which improves the wetting properties of the solution by adding fluorinated organic compounds to solve this problem. However, the added fluorinated organic compounds are easily adsorbed onto the PCB surface and are difficult to rinse off with DI water, increasing the difficulty of rinsing. Furthermore, fluorinated organic compounds are subject to comprehensive restrictions under new domestic and international regulations, making long-term compliant use difficult. ② Incomplete cleaning of ionic contamination: Ionic residues in DEFLUX cleaning originate from organic acids, halogens, rosin metal soaps, and free copper, calcium, magnesium, and other metal ions in the flux. Conventional cleaning agents have limited ability to clean contamination from the various components generated during welding. For example, a flux removal composition provided by patent CN 117222729A uses only a combination of multiple solvents and acidic additives. This type of system has strong solubility for organic resin contaminants, but because the solvent cannot be saponified and there are no chelating agents to complex metal ions, this system cannot completely solve the ionic contamination caused by high ion loading, carbonized rosin, and metal soaps. ③ The process window is narrow, and the foam problem cannot adapt to the production requirements of high-pressure spraying. For example, the water-based flux cleaner provided by patent CN 114106935B uses a chelated surfactant with an amide and polycarboxyl anion structure, which provides a strong foaming skeleton and a long foam half-life. If high-pressure spraying is used, a large amount of foam will be generated, which will easily overflow the tank and block the spray nozzle. Therefore, it is only suitable for ultrasonic cleaning. However, if ultrasonic process is used, it will easily cause damage to the substrate (such as bottom filling epoxy glue, chip dispensing and encapsulating dPCBA, the cavitation impact of ultrasound will destroy the interface between the bottom filler and the chip and PCB, and produce micro gaps), which will have an immeasurable impact on the product yield. Summary of the Invention

[0004] The purpose of this invention is to provide a water-based deflux cleaning agent for PCBA board SMT process, which has the advantages of good emulsification cleaning performance, strong wetting and penetration, good deionization effect, high cleaning cleanliness, and certain corrosion inhibition function. It can be used to clean various contaminant residues such as flux on the surface of PCBA board after reflow soldering, and is compatible with various types of PCBA products.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A water-based deflux cleaning agent for PCBA board SMT process, based on a total mass percentage of 100%, is composed of the following raw materials in the following mass percentages: 5-20% organic amine, 20-40% organic alcohol ether solvent, 1-10% polar solvent, 0.1-5% organic chelating agent, 0.1-5% rosin-based block polyether phosphate sodium salt surfactant, and 30-50% deionized water.

[0006] Further, the organic amine is one or more of isopropanolamine, diisopropanolamine, diethylene glycolamine, triethanolamine, diethanolamine, N-butyldiethanolamine, ammonia, 2-amino-2-methyl-1-propanol, N-methyldiethanolamine, N-ethylethanolamine, monoethanolamine, tert-butylamine, and N-tert-butyldiethanolamine.

[0007] Further, the organic alcohol ether solvent is one or more of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol methyl ether, diethylene glycol monobutyl ether, propylene glycol methyl ether, dipropylene glycol butyl ether, tripropylene glycol butyl ether, and dipropylene glycol monomethyl ether.

[0008] Further, the polar solvent is one or more of benzyl alcohol, N-methylformamide, propylene glycol methyl ether acetate, N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylacetamide, methyl ethyl ketone, N-vinyl-2-pyrrolidone, tetrahydrofurfuryl alcohol, ethylene glycol butyl ether acetate, propylene glycol diacetate, dipropylene glycol methyl ether acetate, and N,N-dimethylformamide.

[0009] Further, the organic chelating agent is one or more of the following: ethylenediaminetetraacetic acid salt, trisodium methylglycine diacetate, tetrasodium glutamate diacetate, sodium ethylenediaminedisuccinate, pentasodium diethylenetriaminepentaacetate, trisodium hydroxyethylethylenediaminetriacetate, trisodium citrate, sodium gluconate, diethylenetriaminepentamethylphosphonic acid, and hydroxyethylidene diphosphonic acid.

[0010] Furthermore, the resistivity of the deionized water is greater than 16 MΩ / cm.

[0011] Furthermore, the chemical structural formula of the rosin-based block polyether phosphate sodium salt surfactant is as follows: , where m and n are both integers selected from 1 to 10.

[0012] Furthermore, the preparation method of the rosin-based block polyether phosphate sodium salt surfactant includes the following steps: a) Synthesis of rosin acyl chloride , Abrasive acid was added to anhydrous dichloromethane and cooled to 0-5°C in an ice-water bath under stirring. Then, a trace amount of DMF was added as a catalyst, and stirring was continued for 10 min to fully disperse and dissolve the abrasive acid. Then, excess SOCl2 was slowly added dropwise at 0-5°C to ensure complete conversion of the carboxyl group (the addition time was controlled at about 2 h). After the reaction was completed, the dichloromethane was removed by vacuum distillation at 40-50°C. Then, the temperature was raised to 60-70°C, and the residual thionyl chloride was removed by vacuum distillation to obtain abrasive acyl chloride, which was dried for later use. b) Synthesis of rosin-1,3-propanediol monoester , A large excess of 1,3-propanediol (to ensure only one end hydroxyl group reacts) and triethylamine, an acid-binding agent, were added to anhydrous dichloromethane. After stirring for 10 min to ensure complete miscibility, the mixture was cooled to 0-5°C in an ice-water bath, and a dichloromethane solution of rosin acyl chloride was slowly added dropwise (the addition time was controlled at 4 h). After the reaction was completed, the system was heated to room temperature, and the white solid of triethylamine hydrochloride was removed by filtration. The resulting organic phase was washed three times with ice water to remove excess 1,3-propanediol and water-soluble salts. After drying with anhydrous magnesium sulfate, the dichloromethane was removed by vacuum distillation at 40°C and -0.08 MPa to obtain a pale yellow viscous rosin 1,3-propanediol monoester. c) Synthesis of sodium rosin-based phosphate , The obtained rosin 1,3-propanediol monoester was dissolved in anhydrous dichloromethane, and then a dichloromethane solution of P2O5 was slowly added dropwise at 70-80℃ (the addition time was controlled at 4 h). After the reaction was completed, distilled water was added at 80℃ and the mixture was stirred and hydrolyzed for 2 h. The solvent was then removed by evaporation, and then NaOH was added in an ethanol solution to neutralize the solution to pH 8-9. Anhydrous ethanol was then added to remove the salt, and the solvent was removed by distillation to obtain NaOH-neutralized sodium rosin phosphate. d) Synthesis of rosin-based block polyether phosphate sodium salt surfactant , Sodium rosin-based phosphate, KOH catalyst, EO and PO were mixed under vacuum and block polymerization was carried out at 120~130℃ and 0.25 MPa. The reaction was terminated when the pressure inside the reactor returned to normal pressure, and the sodium salt surfactant of rosin-based block polyether phosphate was finally obtained.

[0013] In step a), the molar ratio of rosin acid to SOCl2 is 1:1.5.

[0014] The molar ratio of 1,3-propanediol, triethylamine, and rosinyl chloride used in step b) is 3:1.15:1.

[0015] The molar ratio of 1,3-propanediol monoester of rosin used in step c) is 1:3.

[0016] The molar ratio of sodium rosyl phosphate, KOH, EO and PO used in step d) is 1:0.01:m:n (m and n are both selected from integers from 1 to 10).

[0017] Furthermore, the preparation of the water-based deflux cleaning agent includes the following steps: 1) Mix deionized water and organic chelating agent and stir for 15-30 minutes; 2) Add rosin-based block polyether phosphate sodium salt surfactant to the mixed solution obtained in step 1), and mix and stir for 5-10 min; 3) Add organic alcohol ether solvent and polar solvent to the mixed solution obtained in step 2), and mix and stir for 5-10 minutes; 4) Add organic amine to the mixed solution obtained in step 3) and mix and stir for 10-20 minutes; 5) Stop stirring and let stand at room temperature to obtain a clear and homogeneous composition.

[0018] Furthermore, the water-based deflux cleaning agent is used by diluting it with water 5 to 10 times before cleaning the PCBA substrate.

[0019] Furthermore, the cleaning methods employed include, but are not limited to, spraying, bubbling, ultrasonic cleaning, misting, and wiping. Taking spray cleaning as an example, it specifically involves diluting a water-based deflux cleaning agent, heating it to 60±5℃, and then applying it at a pressure of 4 kg / cm³. 2 Spray cleaning at a spray pressure of 4 kg / cm² for 3-5 minutes; then rinse with deionized water at 40±5℃. 2 Spray cleaning under high pressure for 3-5 minutes, rinse, repeat twice, and then dry with hot air at 80-110℃ for 10-30 minutes.

[0020] Furthermore, the PCBA substrates being cleaned are categorized according to the type of devices they support, including but not limited to WIRE-BOND, BGA, FC-BGA, QFN, QFP ultra-fine pin ICs, and 01005 micro-components.

[0021] The significant advantages of this invention are: The rosin-based block polyether phosphate sodium salt surfactant used in this invention possesses the triple structural advantages of a homologous rosin hydrophobic framework, flexible EO / PO block segments, and double-ionized phosphate hydrophilic groups. On one hand, the freely twistable EO / PO block structure endows the cleaning solution with extremely strong capillary penetration ability, allowing it to quickly penetrate into the micron-sized gaps at the roots of FC-BGA and WB leads, significantly reducing the surface tension of the cleaning solution, weakening capillary resistance, and achieving deep wetting of minute gaps. On the other hand, relying on the directional adsorption properties of the similar miscibility between the rosin fused rings and cross-linked rosin resin, combined with the flexible block chains to enhance liquid penetration, and the phosphate anionic groups forming a hydration film to strengthen overall wetting and stably disperse and remove residual residues, it possesses wetting and penetration performance far exceeding that of conventional surfactants. Therefore, the cleaning agent prepared using the rosin-based block polyether phosphate sodium salt surfactant of this invention has excellent specific emulsification cleaning performance and wetting and penetration performance, capable of thoroughly removing deep residues from narrow gaps between PCBA substrate components.

[0022] (2) This invention uses a unique rosin-based block polyether phosphate sodium salt surfactant with ultra-low foaming and certain corrosion inhibition functions, and is suitable for a wide range of product types and cleaning processes. Its ultra-low foaming characteristics stem from the advantages of its molecular structure: the hydrophobic PO block weakens the hydrogen bonding ability of water molecules, reducing the elasticity and stability of the foam liquid film; combined with the rigid large steric hindrance structure of tricyclic rosin, it disrupts the regular arrangement of molecules at the gas-liquid interface, allowing the foam to break down quickly under spraying and ultrasonic dynamic conditions, without foam accumulation or overflow problems, and belongs to the self-foaming type of low-foaming surfactant. At the same time, this surfactant has a dual corrosion inhibition effect. Its polar phosphate groups can be chemically adsorbed on the surface of copper, aluminum, and OSP substrates to form a dense passivation barrier film; the outer hydrophobic rosin skeleton constructs a hydrophobic shielding layer, which can isolate strong alkali, halogen and other corrosive media, effectively inhibit metal dissolution and substrate corrosion, and can also work with the system components to stabilize the cleaning effect, taking into account both powerful descaling and substrate safety.

[0023] (3) This invention uses a unique rosin-based block polyether phosphate sodium salt surfactant combined with organic amines, organic chelating agents, and polar solvents to thoroughly remove organic acids, halogens, rosin metal soaps, and free copper, calcium, magnesium, and other metal ion contaminants from the flux. Specifically, the organic amines in the system neutralize organic acids, generating water-soluble organic amine salts that are no longer adsorbed onto the PCB surface; the multi-carboxyl organic chelating agent has multiple coordination sites, forming stable water-soluble chelate complexes with metal ions such as Cu, Ca, and Mg; simultaneously, the phosphate anions in the surfactant structure adsorb dissociated halide salt particles, forming an electrostatic / steric hindrance layer, preventing halide salt agglomeration and re-adsorption onto the PCBA. The synergistic effect of these three components forms a perfect closed loop, eradicating ionic contamination on the PCBA substrate and significantly improving the insulation stability of the PCBA under high and low temperature and humid conditions, enabling it to meet the high reliability requirements of military and automotive electronics industries. Attached Figure Description

[0024] Figure 1 The image shows a comparison of the residual flux on the FC-BGA chip before and after cleaning with the cleaning agent prepared in Example 1. Detailed Implementation

[0025] A water-based deflux cleaning agent for PCBA board SMT process, based on a total mass percentage of 100%, is composed of the following raw materials in the following mass percentages: 5-20% organic amine, 20-40% organic alcohol ether solvent, 1-10% polar solvent, 0.1-5% organic chelating agent, 0.1-5% rosin-based block polyether phosphate sodium salt surfactant, and 30-50% deionized water.

[0026] The organic amine is one or more of the following: isopropanolamine, diisopropanolamine, diethylene glycolamine, triethanolamine, diethanolamine, N-butyldiethanolamine, ammonia, 2-amino-2-methyl-1-propanol, N-methyldiethanolamine, N-ethylethanolamine, monoethanolamine, tert-butylamine, and N-tert-butyldiethanolamine.

[0027] The organic alcohol ether solvent is one or more of the following: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol methyl ether, diethylene glycol monobutyl ether, propylene glycol methyl ether, dipropylene glycol butyl ether, tripropylene glycol butyl ether, and dipropylene glycol monomethyl ether.

[0028] The polar solvent is one or more of benzyl alcohol, N-methylformamide, propylene glycol methyl ether acetate, N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylacetamide, methyl ethyl ketone, N-vinyl-2-pyrrolidone, tetrahydrofurfuryl alcohol, ethylene glycol butyl ether acetate, propylene glycol diacetate, dipropylene glycol methyl ether acetate, and N,N-dimethylformamide.

[0029] The organic chelating agent is one or more of the following: ethylenediaminetetraacetic acid, trisodium methylglycine diacetate, tetrasodium glutamate diacetate, sodium ethylenediaminedisuccinate, pentasodium diethylenetriaminepentaacetate, trisodium hydroxyethylethylenediaminetriacetate, trisodium citrate, sodium gluconate, diethylenetriaminepentamethylphosphonic acid, and hydroxyethylidene diphosphonic acid.

[0030] The resistivity of the deionized water is greater than 16 MΩ / cm.

[0031] The chemical structural formula of the rosin-based block polyether phosphate sodium salt surfactant is as follows: , where m and n are both integers selected from 1 to 10.

[0032] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0034] The preparation method of the rosin-based block polyether phosphate sodium salt surfactant used in the examples includes the following steps: 1) Synthesis of rosin acyl chloride Nitrogen gas was introduced into a 500 mL straight four-necked flask equipped with a condenser, stirrer, and thermometer to replace the air in the apparatus and prevent moisture from entering. Then, 0.1 mol of rosin acid and 100 mL of anhydrous dichloromethane were added as solvents. The stirrer was turned on, and the flask was cooled to 0-5 °C in an ice-water bath. Then, about 0.5 mL of trace DMF was added as a catalyst, and stirring was continued for 10 min to ensure that the rosin acid was fully dispersed and dissolved. Then, 0.15 mol (excess, to ensure complete conversion of carboxyl groups) of SOCl2 was added to a constant pressure dropping funnel and slowly added dropwise to the above solution (the temperature of the system was controlled at 0-5 °C throughout the dropping process, and the dropping time was controlled at about 2 h). The HCl and SO2 gases continuously generated during the dropping process were absorbed by passing them into an alkaline solution. After the reaction was completed, the dichloromethane was removed by vacuum distillation at 40-50 °C. Then, the temperature was raised to 60-70 °C, and the pressure was reduced again to completely distill off the residual excess thionyl chloride, yielding rosin acyl chloride, which was dried for later use.

[0035] 2) Synthesis of rosin-1,3-propanediol monoester In a 500 mL straight four-necked flask equipped with a condenser, stirrer, and thermometer, 100 mL of anhydrous dichloromethane was added as a solvent, along with 0.3 mol of 1,3-propanediol (in substantial excess to ensure only one end hydroxyl group reacts) and 0.115 mol of triethylamine as an acid-binding agent. The mixture was stirred for 10 min until completely miscible, then cooled to 0–5 °C in an ice-water bath while maintaining the system temperature. 0.1 mol of solid rosinyl chloride was dissolved in 70 mL of anhydrous dichloromethane and transferred to a constant-pressure dropping funnel, then slowly added dropwise to the above solution (dropping time controlled over 4 h, with the system temperature maintained at 0–5 °C throughout). After the reaction, the system was heated to room temperature, and the white solid triethylamine hydrochloride was removed by filtration. The resulting organic phase was washed three times with ice water to remove excess 1,3-propanediol and water-soluble salts, then dried with anhydrous magnesium sulfate for 1 h, and the drying agent was removed by filtration. Finally, the mixture was dried at 40 °C at -0.08 °C. Dichloromethane was removed by vacuum distillation under MPa conditions to obtain a pale yellow, viscous rosin 1,3-propanediol monoester.

[0036] 3) Synthesis of sodium rosin-based phosphate In a 500 mL straight four-necked flask equipped with a condenser, stirrer, and thermometer, 100 mL of anhydrous dichloromethane was added as a solvent, along with 0.1 mol of rosin 1,3-propanediol monoester. 0.3 mol of P₂O₅ was dissolved in 50 mL of anhydrous dichloromethane and transferred to a dropping funnel. This solution was then slowly added dropwise to the above solution at 70–80 °C (dropping time controlled over 4 h). After the reaction was complete, an appropriate amount of distilled water was added to hydrolyze the generated phosphate ester at 80 °C for 2 h, followed by distillation to remove the solvent. Then, an ethanol solution of NaOH was added to neutralize the solution to pH 8–9. Anhydrous ethanol was then added for desalting, and the solvent was removed by distillation to obtain NaOH-neutralized sodium rosin-based phosphate.

[0037] 4) Synthesis of rosin-based block polyether phosphate sodium salt surfactant In a sealed reactor system, the mixture was purged with dry N2 and evacuated, repeated 2-3 times. Then, 0.1 mol of sodium rosin-based phosphate, 0.001 mol of KOH as a catalyst, and M times the molar amount of EO and N times the molar amount of PO were added. Block polymerization was carried out at 120-130℃ and 0.25 MPa. The reaction was terminated when the pressure inside the reactor returned to atmospheric pressure. After cooling, the reactor was opened, finally yielding a sodium rosin-based block polyether phosphate surfactant.

[0038] Taking m=5 and n=5 as an example, the structural characterization data of the obtained surfactant are as follows: 1H NMR (300Mhz, DMSO-d6), δ: 0.88 (m, 6H, CH3), 1.26 (s, 20H, CH2), 1.30 (s, 8H, C H2), 1.33 (s, 4H, CH2), 1.54 (m, 4H, CH2), 2.11 (t, 4H, CH3), 2.68 (s, 6H, CH3), 3 .3(t,4H,CH2),3.47(m,4H,CH2),3.50(m,4H,CH2),3.95(t,4H,CH2),4.50(t , 4H, CH2), 7.01 (s, 2H, NH), 7.16 (m, 4H, CH), 7.22 (m, 2H, CH), 7.25 (m, 4H, CH); 13 C NMR (125Mhz, DMSO-d6), δ: 14.1, 22.7, 31.9, 29.3, 29.6, 29.4, 22.6, 18.6, 26.5, 45.4, 45.7, 47.6, 56.3, 60.4, 125.7, 128.6, 129.0, 132.6, 159.1, 163.9, 194.7; HRMS calculated value C 47 H 84 NaO 16 P(M+H) + : 958.54, measured value: 959.14.

[0039] Example Prepare different deflux cleaning agents according to the proportions in Table 1. The preparation method includes the following steps: 1) Mix deionized water and organic chelating agent and stir for 20 minutes; 2) Add the surfactant to the mixed solution obtained in step 1) and mix and stir for 10 minutes; 3) Add alcohol ether solvent and polar solvent to the mixed solution obtained in step 2), and mix and stir for 10 min; 4) Add organic amine to the mixed solution obtained in step 3) and mix and stir for 10 min; 5) Stop stirring and let stand at room temperature to obtain a clear and homogeneous composition.

[0040] Table 1. Components and their contents in different deflux cleaning agents

[0041] The cleaning agents obtained in the examples and comparative examples were subjected to comprehensive performance tests: (1) Flux cleaning effect test A 1×1cm FC-BGA chip containing flux residue was placed in the cleaning agent (immersion concentration of 20% wt aqueous solution) of the examples and comparative examples at 60±5℃, respectively, at 4 kg / cm². 2 Under pressure, spray clean for 5 minutes; then rinse with deionized water at 40±5℃ at 4 kg / cm³. 2 The flux was sprayed and rinsed under pressure for 5 minutes, and then rinsed twice. After that, it was dried with hot air at 80-110℃ for 30 minutes. The cleaning effect of the flux is shown in Table 2.

[0042] Table 2 Cleaning effect of different deflux cleaning agents

[0043] As shown in Table 2, the cleaning agents prepared in the examples can completely and clearly remove the residual flux on the FC-BGA chip, while the cleaning agents prepared in the comparative examples all have varying degrees of residue after cleaning.

[0044] Compared with Example 1, Comparative Example 1 used ordinary block polyether L64 as a surfactant, and a small amount of residue remained after cleaning. This is mainly because the rosin-based hydrophobic segment in the sodium salt of rosin-based block polyether phosphate surfactant is structurally homologous to the rosin acid, dehydrorosin acid, and dimer rosin acid in the flux, and has a very strong like-like-like-like-like-like-like effect. It can quickly swell and disintegrate the rosin scale that has been cured after high-temperature soldering and the semi-cured flux residue at the bottom of the BGA. L64 is an aliphatic hydrophobic chain, which lacks the rosin-based structure and has weak compatibility with rosin resin. It can only emulsify the surface oil and has difficulty penetrating the hardened rosin in the gaps and micropores, and is prone to whitening and hazy residue.

[0045] Compared with Example 1, Comparative Example 2 did not add surfactant, and a large amount of flux residue remained after cleaning. This is because the lack of surfactant significantly reduced the emulsification, cleaning, wetting and penetration performance of the solution on flux residue. It could only dissolve a small amount of uncrosslinked rosin by acid-base saponification and organic solvents to wash away surface scum, but could not swell, peel off and cure rosin resin residue.

[0046] Compared with Example 1, Comparative Example 3 used intermediate sodium rosin-based phosphate as a surfactant. After cleaning, a small amount of flux residue remained. This was because it lacked a block polyether structure, which led to a significant decrease in wetting and penetration performance. It could only act on the surface of the residue and was ineffective in cleaning the rosin residue that had been carbonized and polymerized at high temperatures during reflow soldering, resulting in cleaning residue. At the same time, due to the lack of PO blocks, which imparted low-foaming and dynamic foam suppression properties, the cleaning foam was high. The foam would also adsorb contaminants and impurities, and could easily cause secondary pollution when it broke up.

[0047] (2) Ion residual performance test The FC-BGA chips treated in Example 1 and the comparative example in the cleaning performance test were used to test the ion contamination level using an ion chromatography analyzer according to the IPC-TM-6502.3.28B standard. The results are shown in Table 3. Table 3. Ion residues after cleaning with different deflux cleaning agents

[0048] As shown in Table 3, the amount of residual ions on the FC-BGA chip treated with the cleaning agent of the examples was significantly lower than that of the control group.

[0049] Compared to Example 1, Comparative Example 1 used ordinary block polyether L64 as a surfactant, and its ionic residue after cleaning was higher. This was mainly due to the Cl contained in the rosin flux. - ,Br - Organic acid radicals and metal oxide micropowders are among the causes of ion residue. The sodium phosphate salt in rosin-based block polyether phosphate surfactant is negatively charged and can encapsulate rosin microparticles to form a double electric layer repulsion, completely preventing rosin particles from flocculating and agglomerating. However, L64 lacks a phosphate salt structure and has no charge repulsion, relying only on steric hindrance, which easily leads to the agglomeration and sedimentation of high-concentration rosin residue, resulting in severe sludge accumulation in the circulation tank and secondary adsorption on the PCB board surface. At the same time, in terms of chemical rinsing, L64, as a macromolecular polyether, forms a non-volatile organic film after drying, which can interfere with ion chromatography detection. In contrast, rosin sodium phosphate leaves no clean residue after rinsing and is more likely to pass halogen-free and ion contamination control in one go.

[0050] Compared with Example 1, Comparative Example 2 did not add surfactant, and its ion residue was high after cleaning. The main reason is that organic acid and halogen ion contamination comes from flux, so the ion residue rate is positively correlated with the cleanliness of flux cleaning. Secondly, due to the lack of surfactant dispersion, weak chelation and wetting effect, the rinsing performance of the solution is poor, and water stains and watermarks are easily formed, which further aggravates the occurrence of ion residue.

[0051] Compared with Example 1, Comparative Example 3 used sodium rosin-based phosphate surfactant, and the ion residue after cleaning was higher. This is partly because the ion residue is positively correlated with the degree of cleanliness of the cleaning performance, and partly because sodium rosin-based phosphate surfactant lacks a block polyether structure, which reduces the wetting and penetration performance, resulting in weak cleaning residue and foam suppression performance. High foam rinsing residue will cause secondary pollution residue.

[0052] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A water-based deflux cleaning agent for SMT processes of PCBA boards, characterized in that, The cleaning agent, in a total mass percentage of 100%, is composed of the following raw materials in the following mass percentages: 5-20% organic amine, 20-40% organic alcohol ether solvent, 1-10% polar solvent, 0.1-5% organic chelating agent, 0.1-5% rosin-based block polyether phosphate sodium salt surfactant, and 30-50% deionized water.

2. The water-based deflux cleaning agent according to claim 1, characterized in that, The organic amine is one or more of the following: isopropanolamine, diisopropanolamine, diethylene glycolamine, triethanolamine, diethanolamine, N-butyldiethanolamine, ammonia, 2-amino-2-methyl-1-propanol, N-methyldiethanolamine, N-ethylethanolamine, monoethanolamine, tert-butylamine, and N-tert-butyldiethanolamine.

3. The water-based deflux cleaning agent according to claim 1, characterized in that, The organic alcohol ether solvent is one or more of the following: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol methyl ether, diethylene glycol monobutyl ether, propylene glycol methyl ether, dipropylene glycol butyl ether, tripropylene glycol butyl ether, and dipropylene glycol monomethyl ether.

4. The water-based deflux cleaning agent according to claim 1, characterized in that, The polar solvent is one or more of benzyl alcohol, N-methylformamide, propylene glycol methyl ether acetate, N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylacetamide, methyl ethyl ketone, N-vinyl-2-pyrrolidone, tetrahydrofurfuryl alcohol, ethylene glycol butyl ether acetate, propylene glycol diacetate, dipropylene glycol methyl ether acetate, and N,N-dimethylformamide.

5. The water-based deflux cleaning agent according to claim 1, characterized in that, The organic chelating agent is one or more of the following: ethylenediaminetetraacetic acid, trisodium methylglycine diacetate, tetrasodium glutamate diacetate, sodium ethylenediaminedisuccinate, pentasodium diethylenetriaminepentaacetate, trisodium hydroxyethylethylenediaminetriacetate, trisodium citrate, sodium gluconate, diethylenetriaminepentamethylphosphonic acid, and hydroxyethylidene diphosphonic acid.

6. The water-based deflux cleaning agent according to claim 1, characterized in that, The chemical structural formula of the rosin-based block polyether phosphate sodium salt surfactant is as follows: , where m and n are both integers selected from 1 to 10.

7. The water-based deflux cleaning agent according to claim 1, characterized in that, The resistivity of the deionized water is greater than 16 MΩ / cm.

8. The water-based deflux cleaning agent according to claim 1, characterized in that, Its preparation includes the following steps: 1) Mix deionized water and organic chelating agent and stir for 15-30 minutes; 2) Add rosin-based block polyether phosphate sodium salt surfactant to the mixed solution obtained in step 1), and mix and stir for 5-10 min; 3) Add organic alcohol ether solvent and polar solvent to the mixed solution obtained in step 2), and mix and stir for 5-10 minutes; 4) Add organic amine to the mixed solution obtained in step 3) and mix and stir for 10-20 minutes; 5) Stop stirring and let stand at room temperature to obtain a clear and homogeneous composition.

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