High-temperature-resistant LED electrode protective agent and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant LED electrode protective agent used in the field of LED chip packaging and a preparation method of the high-temperature-resistant LED electrode protective agent. The high-temperature-resistant LED electrode protective agent comprises the following components in percentage by mass: 0.1-5% of a pH regulator, 20-30% of an alcohol solvent, 0.1-5% of a thiadiazole-containing imidazoline gemini quaternary ammonium salt surfactant, 0.1-5% of a sulfydryl-containing nitrogen-containing heterocyclic compound and 60-80% of deionized water, wherein the sum of the mass percentages of the components is 100%. The invention discloses a high-temperature-resistant LED electrode protective agent, and aims to provide the high-temperature-resistant LED electrode protective agent which is used for adsorbing a layer of uniform protective film on the surface of a chip after waxing of an LED wafer, and is not desorbed in a subsequent DBR (Distributed Bragg Reflector) process at the temperature of 200 DEG C or above until the surface of a chip electrode is protected from being polluted and attached by volatile solid crystal glue in a packaging and solid crystal link.

Description

Technical Field

[0001] This invention belongs to the field of LED manufacturing process and packaging, and particularly relates to a method for preparing a high-temperature resistant LED chip electrode protectant. Background Technology

[0002] A light-emitting diode (LED) is a semiconductor device that converts electrical energy into visible light. It differs from the tungsten filament principle of incandescent lamps and the tri-color phosphor principle of energy-saving lamps. LEDs are made of group III-IV compound semiconductors (such as gallium arsenide (GaAs), gallium phosphide (GaP), and gallium arsenide phosphide (GaAsP)). When a forward voltage exceeding a certain value is applied, the diode emits light of a specific color; the exact color depends on the materials used in its manufacture.

[0003] The core of an LED is a chip composed of p-type and n-type semiconductors, with a transition layer between the two types called a PN junction. In the PN junction of certain semiconductor materials, when injected minority carriers recombine with majority carriers, they release excess energy in the form of light, thus directly converting electrical energy into light energy. LEDs can be categorized based on factors such as color, light-emitting surface characteristics, materials, structure, and intensity angle.

[0004] LEDs have advantages such as energy saving, high efficiency, durability, greenness, and environmental friendliness. After several years of rapid development, they are now used in modern lighting, digital displays, and other fields. Moreover, the application of LEDs in various industries has also promoted the manufacturing and use of semiconductor LEDs.

[0005] The LED industry is typically divided into three main stages based on the supply chain: upstream (epitaxy growth), midstream (chip manufacturing), and downstream (packaging). In the downstream packaging stage, LED chip surface contamination is a common problem encountered by both LED chip manufacturers and LED packaging companies. Severe LED surface contamination can obstruct light emission from the chip, cause leakage after packaging, and lead to difficulties in wire bonding or failure due to poor soldering after bonding.

[0006] Currently, contamination of the chip electrode surface by volatile substances from the die-attach adhesive during the die-attach baking process, referred to as "adhesive gas contamination," is a significant cause of this problem. During the die-attach baking process, some unreacted small-molecule cross-linking agents containing hydroxyl groups in the die-attach adhesive volatilize and adsorb onto the hydroxyl groups present on the electrode surface through hydrogen bonds. Subsequently, the linking groups lose a water molecule to form covalent bonds, resulting in a large amount of die-attach adhesive contaminants containing C, O, and Si elements remaining on the chip surface. Figure 1 As shown.

[0007] Solutions to "glue gas contamination" are currently being developed simultaneously at both the die-attach adhesive and chip levels. At the die-attach adhesive level, process improvements such as molecular distillation and acid-catalyzed equilibrium reactions are being implemented to enhance raw material consistency and reduce glue gas contamination caused by small-molecule volatiles. However, the industry currently uses a wide variety of die-attach adhesives, requiring LED manufacturers and packaging companies to establish partnerships with different die-attach adhesive suppliers individually. Furthermore, the industry lacks unified standards for the small-molecule glue gas emission levels in die-attach adhesives, making optimization of die-attach adhesives extremely costly in terms of process improvements and communication. Due to the uncertain frequency of "glue gas contamination," chip manufacturers and packaging companies also find it difficult to inspect and identify truly qualified die-attach adhesives. Currently, improvements at the die-attach adhesive level are limited to a few high-end models.

[0008] Therefore, at the chip level, chip manufacturers and chemical solution manufacturers have established communication and cooperation to improve the final wet process (wax removal cleaning process) in LED manufacturing, which has become the optimal solution to the glue gas contamination problem. Patent CN116891784B mentions an LED solid wax cleaning agent and its cleaning process, which uses a special oleic acid-based phosphate ester anionic surfactant. The phosphate ester groups in the surfactant form a hydrophobic film on the surface, thereby protecting the chip surface to a certain extent and avoiding glue gas contamination. However, this surfactant only has one active site, the phosphate ester group, and the high-temperature stability of the adsorption film is limited.

[0009] After the LED waxing process in the downstream process of LED chip manufacturing, and before final dicing, a DBR (Distributed Bragg Reflector) process is required. This process involves an annealing treatment after thin film deposition, where the wafer is heated to 200-300°C, severely testing the adsorption stability of the protective film. CN116891784B mentions that the desorption temperature of the phosphate ester-type protective film is approximately 180°C-250°C. Desorption may occur at some sites during this process, reducing the protective effect on the chip surface in subsequent packaging processes. To avoid desorption of the protective film due to high temperatures during the DBR process, some processes involve a second wet process on the DBR-treated chip to adsorb a new protective film onto the surface. However, this additional process increases the risk of chip breakage during transfer, transportation, and cleaning, and incurs additional labor costs. Therefore, this invention is proposed. Summary of the Invention

[0010] This invention aims to provide a high-temperature resistant LED electrode protectant. After LED wafers are dewaxed, the solution is used to immerse the chip surface, adsorbing a uniform protective film that remains intact during subsequent DBR processes at temperatures above 200°C, and continues to protect the chip electrode surface from contamination by volatile die-bonding adhesive during the die-bonding stage. Compared to traditional electrode protectants, this invention offers advantages such as high-temperature resistance and long-lasting adsorption performance, avoiding chip breakage and labor costs caused by a second wet process after DBR, as well as the abnormal protective performance failure due to film desorption after prolonged storage.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A high-temperature resistant LED electrode protectant for LED chip packaging comprises the following components in 100% by mass: pH adjuster 0.1-5%, alcohol solvent 20-30%, imidazoline-type gemini quaternary ammonium salt surfactant containing thiadiazole 0.1-5%, mercapto-containing nitrogen-containing heterocyclic compound 0.1-5%, and deionized water 60-80%.

[0012] Furthermore, the general structural formula of the thiadiazole-containing imidazoline-type geminal quaternary ammonium salt surfactant is as follows: Where n is an integer between 11 and 17.

[0013] Furthermore, the pH adjuster is one or more of diethylene glycolamine, triethanolamine, N-butyldiethanolamine, 2-amino-2-methyl-1-propanol, and N-ethylethanolamine.

[0014] Furthermore, the alcohol solvent is one or more selected from n-propanol, benzyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, and dipropylene glycol butyl ether.

[0015] Further, the thiol-containing nitrogen-containing heterocyclic compound is one or more of 5-mercapto-1-phenyltetrazazole, 5-mercapto-1-methyltetrazazole, 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, and 1-ethyl-2-mercaptoimidazole. Furthermore, the water is deionized water with a resistivity greater than 16 MΩ·cm.

[0016] Furthermore, the preparation method of the high-temperature resistant LED electrode protectant includes the following steps: 1) Mix deionized water and alcohol solvent and stir for 5-10 minutes; 2) Add a thiadiazole-containing imidazoline-type gemini quaternary ammonium salt surfactant and a thiol-containing nitrogen-containing heterocyclic compound to the solution obtained in step (1), and stir for 10-30 min; 3) Add a pH adjuster to the solution obtained in step (2) and adjust the pH to 7-8; 4) Stop stirring and let stand at room temperature to obtain a clear and homogeneous composition.

[0017] The significant advantages of this invention are: 1) Multiple adsorption sites form a denser protective film, preventing desorption over time: The imidazoline-type geminal quaternary ammonium salt surfactant containing thiadiazole used in this invention innovatively introduces a thiadiazole group. The thiadiazole group contains 2 N atoms and 1 S atom, both containing lone pairs of electrons, which can adsorb onto metal surfaces (such as Fe). 2+ Cu 2+ The empty orbitals of the molecule form coordinate bonds (such as Fe-N, Fe-S, Cu-N bonds), which combine with the N atoms (2) of the imidazoline ring and the two positive charges of the quaternary ammonium salt of the gemini quaternary ammonium salt (electrostatic adsorption). The total number of adsorption sites of the molecule reaches 7. Through the complementary function of heterocyclic rings, the molecular performance is synergistically enhanced, and the adsorption membrane has stronger binding force and more complete coverage.

[0018] 2) Excellent high-temperature resistance, preventing desorption of the protective film during the DBR process: The introduced thiadiazole group, with its unique conjugated system, endows the entire molecule with extremely strong ring structure rigidity. The CN bond energy in the thiadiazole ring is higher than that of the ordinary CN bond in the imidazoline ring. The N and S atoms of the thiadiazole ring have a weak electron-withdrawing effect, which can "pull" the electron cloud portion of the N atom on the imidazoline ring towards the thiadiazole ring through the conjugated system, reducing the electron cloud density of the N atom and thus inhibiting the ring-opening reaction of the imidazoline ring. Thermogravimetric analysis shows that traditional imidazoline geminal quaternary ammonium salts begin to show significant mass loss at 180℃ (corresponding to ring-opening of the imidazoline ring), while after introducing the thiadiazole structure, the mass loss onset temperature is delayed to around 300℃.

[0019] 3) The formulation with nitrogen-containing heterocyclic compounds containing thiol groups (-SH) significantly increases the specific adsorption of gold electrodes: In high-power LEDs, gold electrodes are used in extremely high proportions. The strong covalent bonds (S-Au bonds) formed by these compounds, with bond energies far exceeding those of the N-Au bonds, ensure targeted adsorption of gold electrodes. Furthermore, due to their synergistic effect with imidazoline-type geminal quaternary ammonium salt surfactants containing thiadiazoles, a three-dimensional adsorption network is formed targeting different sites on the gold electrode, thereby significantly increasing the specific adsorption of gold electrodes. As the LED industry increasingly focuses on higher power LEDs, the adsorption advantages of this formulation will become increasingly pronounced. Attached Figure Description

[0020] Figure 1 The image on the right shows a magnified view of a portion of the chip surface, showing contaminants remaining on the die bond adhesive. Detailed Implementation

[0021] To make the above-mentioned features and advantages of the present invention more apparent and understandable, specific embodiments are described below in detail. Unless otherwise specified, the methods of the present invention are conventional methods in the art.

[0022] 1. A high-temperature resistant LED electrode protectant and its preparation method, comprising, by weight percentage (total 100%), the following raw materials in weight percentage: pH adjuster 0.1-5%, alcohol solvent 20-30%, imidazoline-type geminal quaternary ammonium salt surfactant containing thiadiazole 0.1-5%, mercapto-containing nitrogen-containing heterocyclic compound 0.1-5%, and deionized water 60-80%.

[0023] 2. The pH adjuster is one or more of isopropanolamine, diisopropylamine, diethylene glycolamine, triethanolamine, N-butyldiethanolamine, ammonia, 2-amino-2-methyl-1-propanol, N-ethylethanolamine, monoethanolamine, tert-butylamine, and N-tert-butyldiethanolamine.

[0024] 3. The alcohol solvent is one or more of the following: ethanol, n-propanol, n-butanol, isopropanol, isobutanol, cyclohexanol, hexanediol, ethylene glycol, benzyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, dipropylene glycol butyl ether, tripropylene glycol butyl ether, and dipropylene glycol methyl ether.

[0025] 4. The general structural formula of the thiadiazole-containing imidazoline-type geminal quaternary ammonium salt surfactant is as follows: Where n is an integer between 11 and 17.

[0026] 5. The preparation method of the thiadiazole-containing imidazoline-type geminal quaternary ammonium salt surfactant (taking n=11 as an example) includes the following steps: 1) Synthesis of imidazoline intermediate I 0.1 mol of lauric acid, 0.12 mol of diethylenetriamine, and 0.002 mol of alumina catalyst were added to a three-necked flask equipped with a thermometer, a reflux condenser, and a water separator. At the same time, 40 mL of xylene was added as a dehydrating agent. The intermolecular and intramolecular dehydration was carried out by a stepwise heating method at 140, 170, and 220 °C until no more water was generated. The temperature was then reduced to 140 °C and the mixture was distilled under reduced pressure to remove xylene, generating an amide which was then cyclized to obtain imidazoline intermediate I.

[0027] 2) Synthesis of single-chain imidazoline quaternary ammonium salts The above imidazoline intermediate I and benzyl chloride were added to a three-necked flask at a molar ratio of 1:1. A condenser and thermometer were attached, and a magnetic stirrer was turned on. The mixture was stirred continuously and the temperature was slowly raised to 90-110°C. After reacting for 4 hours, a single-chain imidazoline quaternary ammonium salt was obtained.

[0028] 3) Synthesis of thiadiazole-containing intermediate II Add 0.05 mol of cyanuric chloride and 100 mL of toluene to a three-necked flask, and stir at -5 to 0 °C until completely dissolved. Dissolve 0.055 mol of 2-mercapto-5-methyl-1,3,4-thiadiazole in 50 mL of acetone-water mixture (V... 丙酮 V 水 =2:1), after complete dissolution, add dropwise to a three-necked flask, and stir the reaction at 45~50℃ for 8 hours. Add distilled water to the reaction solution, and a large amount of white solid precipitates. Filter and wash the filter cake with hot acetone, and dry under vacuum to obtain intermediate II containing thiadiazole.

[0029] 4) Synthesis of thiadiazole-containing imidazoline-type geminal quaternary ammonium salt surfactants A single-chain imidazoline quaternary ammonium salt and thiadiazole-containing intermediate II were added to a three-necked flask at a molar ratio of 2:1. An appropriate amount of anhydrous ethanol was then added as a solvent, and the mixture was refluxed at 80°C for 4 hours. After the reaction was completed, the solvent was removed by vacuum distillation, and the mixture was purified by recrystallization with acetone multiple times to obtain the thiadiazole-containing imidazoline-type geminal quaternary ammonium salt surfactant (n=11).

[0030]

[0031] The structural characterization data of the thiadiazole-containing imidazoline-type geminal quaternary ammonium salt surfactants (n=11) are as follows: 1 H 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, 3H, 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); 13C 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 52 H 81 N 11 S2(M+H) + : 923.61, measured value: 924.42.

[0032] 6. The thiol-containing nitrogen-containing heterocyclic compound is one or more of the following: 5-mercapto-1-phenyltetrazazole, 5-mercapto-1-methyltetrazazole, 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptopyrimidine, 2-mercaptopyridine, propenylthiourea, 6-mercaptopurine, 2-mercapto-5-methoxybenzimidazole, mercaptotriazole, 1-ethyl-2-mercaptoimidazole, 5-amino-2-mercapto-1,3,4-thiadiazole, 2-mercapto-5-methyl-1,2,4-triazole, and 5-methyl-2-mercaptobenzothiazole.

[0033] 7. The water is deionized water with a resistivity greater than 16 MΩ·cm.

[0034] 8. The preparation method of the high-temperature resistant LED electrode protectant includes the following steps: 1) Mix deionized water and alcohol solvent and stir for 5-10 minutes; 2) Add a thiadiazole-containing imidazoline-type gemini quaternary ammonium salt surfactant and a thiol-containing nitrogen-containing heterocyclic compound to the solution obtained in step (1), and stir for 10-30 min; 3) Add a pH adjuster to the solution obtained in step (2) and adjust the pH to 7-8; 4) Stop stirring and let stand at room temperature to obtain a clear and homogeneous composition.

[0035] 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.

[0036] Table 1. Components and their contents in different protective agent compositions

[0037]

[0038]

[0039] Comprehensive performance tests were conducted on Examples 1-7 and Comparative Examples 1-4: (1) Performance 1: Test on the protective effect against deteriorating colloid gas pollution Degradation simulation experiments were conducted using Feedpool EP-3600-A8-1 die-attach adhesive. Eight groups of chips (all with gold electrodes) from different batches were used. The eight chip groups were die-attached onto a substrate, which was placed flat in a petri dish. Approximately 0.1g of die-attach adhesive was uniformly coated underneath the substrate. The petri dish was sealed with high-temperature resistant adhesive and baked in an oven at 300°C for 3 hours to simulate the contamination of the chips by volatiles from the die-attach adhesive under baking conditions. Electron microscopy was then used to observe the chips and calculate the proportion of chip groups contaminated by adhesive vapors.

[0040] (2) Performance 2: Gold wire tensile strength test The tensile test is a destructive test used to evaluate the mechanical strength of the gold wire bond points between the internal chip and the lead frame of an LED package. A tiny hook is used to hook the apex of the gold wire vertically upwards, and a vertically upward pulling force is applied until the gold wire breaks or the bond point detaches. The maximum tensile force value during the entire process is recorded. For this test, a tensile force F > 7g is considered acceptable for a gold wire with a diameter of Φ32µm. Die-bonding adhesive contamination on the chip surface can lead to poor wire bonding, resulting in a weaker tensile force value.

[0041] Table 2. Protective effect of different protective agent compositions on chip adhesive gas contamination and tensile test results.

[0042] As shown in Table 2, the proportion of deteriorated gel gas pollution in Examples 1, 2, 3, 4, 5, and 6 was 0%, indicating that the protective liquid prepared by the present invention has a significant protective effect on the electrode.

[0043] Compared to Example 3, Comparative Example 1 did not add a pH adjuster. The added thiol-based nitrogen-containing heterocyclic compounds and quaternary ammonium salt surfactants in this system caused the system pH to be lower, approximately 2-3. In contrast, thiadiazole-containing imidazoline-type geminal quaternary ammonium salt surfactants exhibit the strongest negative charge on metal surfaces and the strongest electrostatic attraction to imidazoline quaternary ammonium salt cations in a neutral to alkaline environment (pH 7-9), thus increasing the adsorption and film-forming rate. Therefore, without a pH adjuster, the adsorption and film-forming rate decreased, consequently affecting the protective effect against colloids and gases.

[0044] Compared to Example 3, Comparative Example 2 did not add any alcohol solvent. Nitrogen-containing heterocyclic compounds have low solubility in aqueous solutions, and without an alcohol solvent to aid dissolution, the amount added would be limited. Simultaneously, the addition of an alcohol solvent can further reduce the surface tension of the system, improving the adsorption rate and uniformity of the protective film on the electrode surface. Therefore, the absence of an alcohol solvent leads to a decrease in the protective effect against colloid vapors.

[0045] Compared to Example 3, Comparative Example 3 did not add nitrogen-containing heterocyclic compounds, but instead used a nitrogen-containing heterocyclic compound containing thiol groups (-SH). The strong covalent bond S-Au bond formed by this compound has a bond energy much higher than that of the N-Au bond, ensuring targeted adsorption onto the gold electrode. Furthermore, due to its synergistic effect with the imidazoline-type geminal quaternary ammonium salt surfactant containing thiadiazole, a three-dimensional adsorption network is formed targeting different sites on the gold electrode, significantly increasing the specific adsorption onto the gold electrode. Since the chips used in this experiment were all gold electrodes, the absence of nitrogen-containing heterocyclic compounds would lead to a decrease in adsorption sites and activity, significantly affecting the film density and thus reducing the gas protection effect.

[0046] Compared with Example 3, Comparative Example 4 did not add a thiadiazole-containing imidazoline-type geminal quaternary ammonium salt surfactant. The thiadiazole-containing imidazoline-type geminal quaternary ammonium salt surfactant used in this invention introduces a thiadiazole group with two N atoms and one S atom, both containing lone pairs of electrons, which can react with metal surfaces (such as Fe). 2+ Cu 2+ The empty orbitals of the thiadiazole ring form coordinate bonds (such as Fe-N, Fe-S, Cu-N bonds), which combine with the two N atoms of the imidazoline ring and the two positive charges of the quaternary ammonium salt of the geminal quaternary ammonium salt (electrostatic adsorption), resulting in a total of seven adsorption sites. Through the complementary functions of the heterocycles, the molecular performance is synergistically enhanced, resulting in stronger adsorption film binding and more complete coverage. Simultaneously, the introduced thiadiazole group, with its unique conjugated system, endows the entire molecule with extremely strong ring structure rigidity, greatly improving the high-temperature resistance of the protective film. The CN bond energy in the thiadiazole ring is higher than that of the ordinary CN bond in the imidazoline ring. The N and S atoms of the thiadiazole ring have a weak electron-withdrawing effect, which can "pull" the electron cloud portion of the N atom on the imidazoline ring towards the thiadiazole ring through the conjugated system, reducing the electron cloud density of the N atom and thus inhibiting the ring-opening reaction of the imidazoline ring. Thermogravimetric analysis revealed that traditional imidazoline geminal quaternary ammonium salts exhibit significant mass loss starting at 180℃ (corresponding to ring opening of the imidazoline ring), while the introduction of a thiadiazole structure delayed the onset of mass loss to around 300℃. Without thiadiazole-containing imidazoline geminal quaternary ammonium salt surfactants, the adsorption film-forming effect and high-temperature resistance of the protective agent would be compromised.

[0047] 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 high-temperature-resistant LED electrode protective agent, characterized in that, The pH regulator is one or more of isopropyl alcohol amine, diisopropyl amine, diethylene glycol amine, triethanolamine, N-butyl diethanolamine, ammonia, 2-amino-2-methyl-1-propanol, N-ethyl ethanolamine, monoethanolamine, t-butylamine, N-t-butyl diethanolamine.

2. The high temperature resistant LED electrode protectant of claim 1, wherein, The alcohol solvent is one or more of ethanol, n-propanol, n-butanol, isopropanol, isobutanol, cyclohexanol, hexanediol, ethylene glycol, benzyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, dipropylene glycol butyl ether, tripropylene glycol butyl ether, dipropylene glycol methyl ether.

3. The high temperature resistant LED electrode protectant of claim 1, wherein, The structure general formula of the imidazoline type gemini quaternary ammonium salt surfactant containing thiazole is as follows:

4. The high temperature resistant LED electrode protectant of claim 1, wherein, The water is deionized water with a resistivity greater than 16 MΩ·cm. wherein n is an integer from 11 to 17.

5. The high temperature resistant LED electrode protectant of claim 1, wherein, The method comprises the following steps:

6. The high temperature resistant LED electrode protectant of claim 1, wherein, 1) mixing and stirring the deionized water and the alcohol solvent for 5-10 min; 7. The method for preparing the high-temperature resistant LED electrode protectant according to claim 1, characterized in that, 2) adding the imidazoline type gemini quaternary ammonium salt surfactant containing thiazole and the nitrogen-containing heterocyclic compound containing sulfydryl to the solution obtained in step (1) and stirring for 10-30 min; 3) adding the pH regulator to the solution obtained in step (2) and adjusting the pH to 7-8; 4) stopping stirring and standing to room temperature to obtain a transparent and clear uniform composition. ​ ​

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