The use of water-based old circuit board cleaner board wash water method

With the rapid development of the electronics industry, electronic equipment has been used in almost all fields of the national economy, which has also led to the generation of a large number of waste electronic products. At present, in the recycling of used electronic products, it is basically the reuse of printed circuit boards (PCBs) or electronic components that are in good function, and the metal and plastic materials in damaged PCBs or components are shredded and recycled. In the recycling process of functional PCB or electronic components, the cleaning process is a more important link, and the types of stains mainly include dust, oil, thermal grease, conformal paint, sugar stains, etc., which are different from the stains in the circuit board production process. The ultrasonic cleaning method disperses, emulsifies and peels off the dirt with the help of a variety of functions, including rough washing, soaking, fine washing, rinsing and other processes; Centrifugal cleaning relies on centrifugal force to separate the dirt. Available in water, semi-aqueous and solvent cleaning agents, water-based cleaning offers many advantages and can be formulated in a flexible manner. Cleaning examples illustrate specific materials, equipment and procedures.

1. Cleaning method suggestions: 1. Ultrasonic cleaning method: Ultrasonic cleaning method is to have direct and indirect effects on liquids and dirt through the cavitation, acceleration and direct flow of ultrasonic waves in the liquid, so that the dirt layer is dispersed, emulsified and peeled off, so as to achieve the purpose of cleaning, this method is more suitable for cleaning items with micro complex structures. Main processes: (1) Rough washing (optional, not essential): Put the old circuit board or electronic components into an ultrasonic cleaner filled with clean water, and use ultrasonic cleaning to remove most of the dirt; (2) Soaking (optional, not required): soak the old circuit board or electronic components that have been coarsely washed in an ultrasonic cleaner equipped with cleaning agent, the soaking time should not be too long, and ultrasonic vibration can be used within 3 times during the soaking process, and the vibration time of each vibration is less than 20 minutes; (3) Fine washing: put the soaked old circuit board or electronic components into an ultrasonic cleaning machine equipped with cleaning agent for cleaning, if conditions permit, proper heating will make the cleaning effect better; (4) Rinse: Use deionized water (or distilled water) to rinse the old circuit board or electronic components thoroughly after fine washing to remove the cleaning agent and residual dirt. 2. Centrifugal cleaning: Centrifugal cleaning technology is a cleaning process that uses centrifugal force to clean electronic circuit components, precision parts and semiconductor components, which has good penetration, dissolution and decontamination effects, and will not cause damage to components while ensuring the cleanliness of components. The working principle of centrifugal cleaning technology is that in the sealed process chamber, the components are driven by the motor to rotate and move up and down. The cleaning agent in the process chamber creates a centrifugal force that acts on the dirt on the circuit board. In this way, the dirt will be gradually separated under the action of centrifugal force, so as to achieve the purpose of cleaning. When the component immersed in the cleaning solution begins to rotate, the space under the component and the direction of the force are applied in the same plane. The centrifugal and combined centripetal forces formed during rotation cause the components to be washed to be surrounded by a mixture of cleaning solutions. As the direction of rotation changes, the solution cleaner flows in all directions, and these forces work together to act on the dirt, causing it to be quickly dissolved and washed away. When the cleaning is complete and the rotating component leaves the solution, the force that pushes the liquid into the space at the bottom of the component also spins off the liquid on the assembly. The components are then rotated in hot air to remove the residue. In the recycling of used electronics, the cleaning process is crucial. The factors that affect the cleaning effect are cleaning temperature, cleaning time and cleaning power, the temperature will affect the activity of the cleaning agent but too high will have adverse effects, with the extension of time, the residual amount of stains will tend to be balanced, the higher the power, the better the cleaning effect, but the equipment cost is high and may affect the wearing parts.

2. Types of cleaning agents: Circuit board cleaning can be divided into three types: water cleaning, semi-water cleaning and solvent cleaning. Water cleaning is a cleaning operation that uses water or water containing additives (surfactants and cleaning aids) for fine washing and rinsing. Semi-aqueous cleaning is a cleaning operation process that first washes with organic solvent and then rinses with water. Solvent cleaning is a cleaning operation that uses organic solvents for primary washing and rinsing. The water-based cleaning process uses water as the cleaning medium, and in order to improve the cleaning effect, water-based PCB circuit board cleaning agent (water-based board washing water) can be added to the water. The water-based cleaning agent is based on pure water, which has good safety, low surface tension, good wetting and permeability to contaminants, and can emulsify polar and non-polar contaminants into stable emulsions. Water-based cleaners are environmentally friendly and can be used over and over again. Most water-based cleaners are low toxicity and generally do not endanger the health of workers, nor do they pose a risk of fire or explosion. Therefore, from the perspective of environmental protection and human health, water-based cleaning has great advantages, which is why European and American countries that pay attention to environmental protection regard water-based cleaning as the preferred process. Water-based cleaners are flexible in their formulation design and options, and can be formulated according to the type of stain. The use of ultrasonic cleaning in the aqueous cleaning process can achieve better cleaning results because ultrasonic produces a better cavitation effect in a dense medium, and the density of water is higher than that of organic solvents, so ultrasonic cleaning is more suitable for aqueous cleaning.

3. Cleaning examples:

<!--[if !supportLists]-->1.<!--[endif]-->Materials and equipment: water, ultrasonic cleaner, NW610 water-based cleaner, purified water, etc.

<!--[if !supportLists]-->2.<!--[endif]-->Brief steps: (1) Prepare diluent: dilute the cleaning agent with water at a ratio of 1:30 to obtain the diluent (for example, 1 kg of cleaning agent is diluted with 30 kg of water); (2) Pour the diluent into the ultrasonic cleaner; (3) Use an ultrasonic cleaner to clean at room temperature for 10 minutes; (4) Rinse with clean water.

4. Brief analysis of the factors affecting the cleaning effect: 1. Cleaning temperature: The temperature of the cleaning agent will directly affect the activity of the cleaning agent, and the activity is weak when the temperature is low, and it takes longer to clean the same amount of stains; However, if the cleaning temperature is too high, it is easy to cause abnormal phenomena such as shortening the life of the cleaning agent, discoloration or detachment of the labels on the surface of electronic components, and discoloration or even corrosion of surface-treated metal structural parts. If the cleaning agent contains a high content of alkaline components, it will also cause discoloration of the device pins under high temperature conditions, forming blue-black or dark black stains, affecting the appearance and electrical properties of the product, and the cleaning temperature should be comprehensively adjusted according to the characteristics of the cleaning object to achieve the best cleaning effect. 2. Cleaning time: Cleaning time is an important parameter in the cleaning process, with the extension of time, the residual amount of stains on the circuit board assembly will gradually decrease until the balance is reached. As a rule of thumb, the amount of stain residue does not change after a certain cleaning time (e.g. 10-15 minutes). Extending the cleaning time indefinitely will not further improve the cleaning effect, and at the same time, for vulnerable and sensitive devices, extending the cleaning time will affect the reliability of electronic devices. The cleaning time needs to be reasonably determined according to the cleaning requirements, cleaning objects and production cycles. 3. Cleaning power: Generally speaking, the higher the cleaning power, the better the cleaning effect, but the higher the cleaning power, the higher the equipment cost. In addition, excessive power can also have a negative impact on consumable parts and sensitive components.

In short, the cleaning process in the recycling of waste electronic products needs to comprehensively consider a variety of factors, select appropriate cleaning methods and cleaning agents, and reasonably adjust the parameters that affect the cleaning effect, so as to achieve effective cleaning of functional PCBs or electronic components, and improve the efficiency and quality of recycling.