In the electronics industry, there will always be some residues left on the motherboard during production. At this time, electronic cleaners are needed to clean up the residues on the motherboard. Otherwise, the residues on the motherboard will easily lead to short circuits or other reasons in the later processing. However, in the cleaning process, the method is very important, and the residues in the dead corners are very difficult to clean. For this, the electronic cleaner manufacturer - Linhai Limin Chemicals Co., Ltd. will explain to you how to use the electronic cleaner:

　　The pollution introduced during PCB soldering can be divided into the following three categories according to the nature and cleaning countermeasures:

　　1. Polar pollutants are mainly halogen activators, salt in hand sweat, acid, etc. These substances can reduce the insulation resistance between conductors and corrode lines in hot and humid conditions. Such contamination should be dissolved and cleaned with polar solvents.

　　2. Non-polar pollutants, mainly non-polar pollutants remaining in the flux after welding, including rosin, resin, grease in hand sweat, etc. These substances will affect the good contact of the test probe and make the protective coating Decrease adhesion. Such contamination should be dissolved and cleaned with non-polar solvents.

　　3. Physical particle pollutants mainly include impurities such as dust, reaction products (insoluble), and solder balls. This type of pollution is generally cleaned by mechanical methods, such as pressure washing and ultrasonic cleaning. (Due to the particularity of electronic products, the use of ultrasonic waves should be determined according to the specific conditions of electronic components.)

　　Since the pollutants on the PCB have three types of substances, a method or process that can remove them all should be adopted during cleaning.

　　Commonly used are:

　　(1) Alcohols are added to CFC-113 to form an azeotrope (the composition contains polar solvents and non-polar solvents), and ultrasonic or spraying is performed.

　　(2) The semi-water cleaning method of cleaning with a solvent first, and then rinsing with pure water.

　　(3) Add saponification agents, surfactants, etc. that can dissolve non-polar pollutants in pure water, and perform ultrasonically or spray water-based cleaning methods.

　　With the improvement of environmental protection requirements, water-soluble solders, fluxes, and no-cleaning solders and fluxes have been developed. Correspondingly, water cleaning methods using pure water and no-cleaning treatment methods without cleaning have emerged. It can be seen that cleaning is mainly divided into four categories: solvent type, semi-aqueous type, water type, and no-cleaning based on the selection of solder and flux.

　　At this stage, various cleaning methods coexist. Process technicians in the electronics industry should understand the characteristics and development direction of cleaning technology, and choose different cleaning methods according to the specific requirements of their products and enterprise characteristics to ensure product reliability.

　　1 Solvent cleaning

　　Such solvents refer to non-aqueous solvents.

　　1.1 Solvent cleaning of ODS substances

　　Such substances include ODS (ozone-depleting substances solvents) such as CFC-113 and 1,1,1-trichloroethane, and CFC-113 is commonly used. Because of their stable performance, wide range of applications, good cleaning effect, good operability, and easy recycling, they have been widely used by many units in our country or are still used today. They have been the main solvents for cleaning electronic product circuit boards for many years. However, due to its destruction of the atmospheric ozone layer, the international community has decided to completely ban the use of such solvents. As a signatory to the Montreal Protocol, my country has stipulated that the use of such solvents will be completely banned in 2006, so this cleaning method will soon be phased out.

　　1.2 Solvent cleaning instead of ODS

　　At present, there are several alternative methods for CFC cleaning. Among them, HCFC and HFC cleaning solvents are fluorine-containing solvents with low or zero ODP values (ozone layer depletion potential value) researched and developed by people. The product is dry; the materials and components have good compatibility; there is no flammability hazard; the performance is similar to CFC, and it is fully compatible with the current CFC-113 cleaning equipment, and the destruction coefficient of the ozone layer is only one-tenth to CFC. Tens of one or non-destructive, its cleaning method is similar to the original CFC-113, the original process equipment is compatible, no need to change, it is considered to be the recommended substitute in the current transitional stage, and the cleaning effect reaches CFC-113 With a cleaning level of -113, the impurities and ion residues after cleaning are lower than the CFC level and have no adverse effects on the surface insulation resistance. The disadvantage is that although the cleaning solvent of HCFC is very low in damage to the atmosphere, it still has a destructive effect. This kind of cleaning solvent and cleaning process will be gradually eliminated, so it can only be used as a transitional substance for cleaning. Although HFC has no destructive effect on the ozone layer, it has a high greenhouse effect coefficient, so it is also a controlled substance.

　　In addition, the common non-ODS cleaning agents in the electronics industry are alcohol. The advantage is that the cleaning effect of rosin flux is very good, and it has good compatibility with the materials used in electronic components. However, due to their easy combustion and explosion, their use is limited. widely used.

　　Many large companies have also developed a variety of non-ODS solvent cleaning agents and put them into use, such as DuPont's Vertrel series of products, which are solvent azeotropes with an ODP value of 0. Among them, there are types suitable for PCB cleaning, and CFC- 113 cleaning equipment. However, so far, no substitute is similar to CFC-113 in the scope of application and cleaning effect. Therefore, people are studying a cleaning agent that has no impact on the environment and can completely replace Freon.

　　1.3 Equipment and precautions for non-aqueous solvent cleaning

　　Solvent cleaning equipment is generally a multi-tank cleaning machine, which can complete functions such as dipping (or additional ultrasonic), manual spraying, rinsing, gas phase cleaning, and condensation recovery.

　　Precautions for cleaning with non-aqueous solvents are mainly

　　(1) Pay attention to the pollution, flammability, toxicity, and other properties of the solvent, and choose carefully.

　　(2) Make full use of the recyclability of materials and save them as much as possible.

　　1.4 Non-aqueous solvent cleaning process route

　　Optional for low boiling point solvents: solvent immersion (additional ultrasonic) → solvent spray → vapor phase rinsing → drying

　　Optional for higher boiling point solvents: solvent immersion (additional ultrasonic) → solvent rinsing → clean solvent spray → drying

　　2 half water wash

　　2.1 Characteristics of semi-water cleaning

　　Firstly, rosin and grease impurities are decomposed by solvent, and then polar pollution and rinsing solvent are cleaned with water. Since these two cleaning processes are completed in one piece of equipment, they are collectively called semi-water cleaning. The process consists of two parts:

　　Solvent cleaning: Solvent washing, emulsification, and cleaning remove flux residues and organic pollutants on printed boards. This solvent should have good dissolving power for non-polar pollution, and at the same time have good compatibility with water, to facilitate the next step of water rinsing.

　　Water Rinse: Use deionized water to remove ionic contaminants and cleaning agents left over from solvent washes.

　　Semi-aqueous cleaning is very suitable for cleaning rosin-based flux, solder paste, and SMA after wave soldering and reflow soldering. The process control is simple, and the chemical balance can be maintained without complicated control. Semi-aqueous cleaning solvents are generally flammable solvents, but they have a higher flash point and are safer to use. Some solvents add a small amount of water and surfactants to make emulsifiers, which not only reduce flammability but also make rinsing easier. Solvents are divided into terpenes, hydrocarbon solvents, etc. The commonly used terpene EC-7 is one of the products recommended by the United Nations Environmental Protection Agency to replace CFC-113 for cleaning.

　　2.2 Semi-water cleaning process equipment and precautions

　　At present, there are two types of semi-aqueous cleaning equipment: an on-line cleaning machine and a batch cleaning machine. Online cleaning mainly adopts the spray method, and the number of conveying circuit board assemblies is large, which is suitable for high-production printed circuit board assembly units. The batch cleaning machine adopts ultrasonic, centrifugal, and jet methods, and its output is small, which is suitable for the assembly plant of printed board components with low and medium output.

　　Semi-aqueous cleaning uses different cleaning agents, resulting in the diversity of this process, so corresponding equipment should be used for different semi-aqueous cleaning processes. No matter what kind of process equipment requires some kind of mechanical excitation, the purpose is to strengthen the mutual contact and collision between the semi-water cleaning solvent and the printed board, to make the cleaning more effective. The four methods used to enhance cleaning are spray, flow in a solvent bath, pressurized spray under immersion, and ultrasonic waves.

　　The semi-aqueous cleaning process has the following points to note:

　　1. For flammable solvents, corresponding protective measures (such as nitrogen environmental protection) must be taken when using them by spraying.

　　2. Wastewater treatment should be considered, and the drying step should be reliable.

　　3. For some solvents that have a harmful odor or are volatile substances, ventilation, and other measures should be strengthened.

　　4. The resistivity of rinsing water must meet the requirements of the product, generally from 100K to 1 trillion, and the requirements for special products are higher.

　　2.3 Semi-water cleaning process

　　The semi-aqueous cleaning process is: solvent or emulsifier cleaning (additional spray, ultrasonic) → water rinsing (two steps) → hot air drying

　　Auxiliary equipment includes pure water preparation, wastewater treatment, etc.

　　Our electronic cleaner effect in the industry is remarkable, and it has won unanimous praise from customers. Welcome to inquire!