PCB board washing liquid formula and composition

PCB board washing solution is used in the electronics industry to remove flux, rosin, solder slag, ink, hand prints and other substances from circuit boards and SMT stencils. The traditional method of cleaning printed circuit boards is to use organic solvents, which are made of CFC-113 mixed with a small amount of ethanol (or isopropanol) to clean the residues of rosin flux, but are currently banned because CFC-113 destroys the atmospheric ozone layer. The non-ODS cleaning processes that can be selected are: water-based cleaning, semi-aqueous cleaning, solvent cleaning, and no-cleaning processes are also available. PCB board washer plays an important role in the electronics industry, which can be used to remove a variety of stains on circuit boards and SMT stencils. Traditional organic solvent cleaning methods are prohibited due to the destruction of the ozone layer by CFC-113, and non-ODS cleaning processes are now available, such as aqueous-based, semi-aqueous-based, solvent-cleaned, and no-clean processes.

Water-based cleaning The water-based cleaning process uses water as the cleaning medium, and in order to improve the cleaning effect, a small amount (generally 2% - 10%) of surfactants, detergents, corrosion inhibitors and other chemicals can be added to the water. And according to the specific situation of different properties of pollution on the printed circuit board, the corresponding substances can be added to the water-based cleaning agent, so as to broaden the scope of application of its cleaning. Water-based cleaning agents have good solubility to water-soluble dirt, and can achieve better cleaning results by combining physical cleaning methods such as heating, brushing, spray spraying, and ultrasonic cleaning. Water-based cleaning uses water as the medium, adds a small amount of chemicals, and cooperates with a variety of physical cleaning methods to clean the circuit board through three processes: cleaning, rinsing and drying.

Water-based cleaning process: The process flow of water-based cleaning includes three processes: cleaning, rinsing and drying. Firstly, the water-based cleaning agent with a concentration of 2% to 10% was used to clean the printed circuit board in batches with physical cleaning methods such as heating, brushing, spray spraying, and ultrasonic cleaning. Then, rinse 2-3 times using pure or ionized water (DI water); Finally, hot air drying is carried out. Water-based cleaning requires the use of pure water for rinsing, which is the reason for its high cost.

Typical water cleaning process: At a temperature of 55 °C, the electronic circuit board is cleaned in batches with a water-based cleaning agent, and cleaned with a strong jet for 5 minutes, then rinsed with deionized water at 55 °C for 15 minutes, and finally dried by hot air at a temperature of 60 °C for 20 minutes.

Semi-aqueous Cleaning Most semi-aqueous cleaners are also formulated with water, but the water content is small (only 5% - 20%), so from the outside, semi-aqueous solvents are clear, homogeneous solutions like solvent cleaners. Different from general solvent cleaning agents, semi-aqueous cleaning agents use organic solvents with higher boiling point and low volatility, so they do not need to be cleaned in a closed environment like solvent cleaning agents, and they do not need to change the cleaning agent frequently during the cleaning process, only need to properly replenish the cleaning dose. The appearance of the solvent of semi-aqueous cleaning is similar to that of solvent cleaning agent, the boiling point of organic solvent is high, the volatility is low, and the cleaning process includes three processes: cleaning, rinsing and drying.

Semi-aqueous cleaning process: Semi-aqueous cleaning process also includes cleaning, rinsing, drying three processes, the cleaning process is often combined with the use of ultrasonic cleaning to improve the cleaning effect, reduce the cleaning time, because the use of ultrasonic will increase the temperature of the cleaning agent, so it is necessary to strictly control the cleaning temperature, not to exceed the flash point of the cleaning solution (generally the cleaning temperature is controlled below 70 °C).

Solvent cleaning The use of organic solvents to clean printed circuit boards is based on its dissolving effect on dirt, after the elimination of CFC-113, TCA and other ODS cleaning agents, the current solvent cleaning agents are mainly HFC, HFC, HFE and other fluorine solvents, hydrocarbon solvents, alcohol solvents, etc. Because these fluorine-based solvents are also non-flammable and have properties very similar to CFC-113, the cleaning process and cleaning equipment do not need to be changed or slightly adjusted. Solvent cleaning uses organic solvents to dissolve dirt, now mainly uses fluorine solvents, hydrocarbon solvents, alcohol solvents, etc., the cleaning process is relatively simple, according to different processes can be combined in a variety of ways, some do not need a special drying process.

Solvent cleaning process: The solvent cleaning process is relatively simple, only need to use the same solvent cleaning agent for cleaning and rinsing, because the volatility of the solvent cleaning agent is mostly good, so there is no need for a special drying process.

Typical solvent cleaning processes include the following: 1) Ultrasonic plus immersion cleaning - spray cleaning - vapor phase rinsing and drying 2) Solvent heating immersion cleaning - cold rinse - spray cleaning - vapor phase rinsing and drying 3) Vapor phase cleaning - ultrasonic plus immersion cleaning - cold rinsing - vapor phase rinsing and drying 4) Vapor phase cleaning - spray cleaning - vapor phase rinsing and drying

Common PCB board washing fluid

Combustible non-ODS cleaners: common hydrocarbons, such as n-pentane, n-hexane, n-heptane, cyclohexane, benzene, toluene, xylene, terpenes, etc.; Alcohols, esters, ethers, ketone solvents, such as acetone, isopropanol, ethyl acetate, butyl acetate, propylene glycol methyl ether, diethylene glycol dimethyl ether, etc.

Non-flammable non-ODS cleaners: mainly organic solvents containing halogens, mainly including haloalkanes, such as dichloromethane, chloroform, dichloroethane, 1,1,2-trichloroethane, tetrachloroethane, n-bromopropane, isobromide propane, n-propyl bromide, dibromomethane; halogenated olefins, such as trichloroethylene, tetrachloroethylene; HCFC solvents, such as 141B, AK225; Fluoroethers and perfluoroalkanes (HFCs) such as decafluoropentane, etc.

Azeotropic Mixture Type Solvent Cleaner: This cleaner is particularly suitable for solvent dehydration drying and vapor phase cleaning, because its composition remains basically unchanged during boiling, evaporation and condensation, so it can be distilled to remove dirt after use, like a single-component solvent cleaner, and continue to be used after purification, which brings great convenience to the preparation of solvent cleaners.

Reference Formula 1) Formula 1 Components Feeding amount (g/L): Trichloroethylene 250 - 350 Hexane 100 - 200 Heptane 200 - 300 Diethylene glycol dimethyl ether 100 - 200 Isopropanol 100 - 200 Butanediol 100 - 200

2) Formula 2: Components: Feeding amount (g/L): cyclohexane 300 - 500, trichloroethylene 200 - 300, butyl acetate 100 - 200, propylene glycol methyl ether 100 - 200, acetone 100 - 200

Common cleaning agents on the market: environmentally friendly hydrocarbon cleaning agents, water-based cleaning agents (water-based degreasers, water-based degreasers, water-based metal cleaning agents), pickling agents, degreasing agents, polishing agents, rust removers (environmentally friendly water-based antirust agents), water film replacement anti-rust oil, dehydrated anti-rust oil, pickling paste (agent), degreasing powder, wax removal water, paint remover, plate washing water, net washing water, optical glass cleaning agent, solvent optical cleaning agent, etc.

Common PCB board washing fluids are divided into flammable non-ODS cleaners (such as hydrocarbons, alcohols and other solvents), non-flammable non-ODS cleaners (mainly halogen-containing organic solvents), and azeotropic mixture solvent cleaners (suitable for solvent dehydration and vapor cleaning). In addition, the reference formulations of the plate wash solution and the types of cleaning agents commonly available in the market, covering a wide range of types from environmentally friendly to functional, are given to meet different cleaning needs.