Introduction to four ways of PCB board cleaning technology
Published time: 2019-12-20 10:40:20
As we all know, circuit board cleaning technology has a very important position for pcb copy board. Because of the need to ensure the cleanliness of the board itself to accurately scan and generate the file map, the board cleaning technology has also become an important "technical activity", the main technical summary of the current technology of Jiedubang's own engineer Wang Gaogong Four ways of circuit board new generation cleaning technology.
1. Water cleaning technology for PCB copy board
Water cleaning technology is the development direction of cleaning technology in the future, and it is necessary to set up a pure water source and a discharge water treatment workshop. It uses water as a cleaning medium, and adds a surfactant, an auxiliary agent, a corrosion inhibitor, a chelating agent, etc. to the water to form a series of water-based cleaning agents. Water solvents and non-polar contaminants can be removed.
Its cleaning process features are:
(1) It is safe, does not burn, does not explode, and is basically non-toxic;
(2) The formula of the cleaning agent has a large degree of freedom, and it is easy to clean both polar and non-polar pollutants, and has a wide cleaning range;
(3) Multiple cleaning mechanisms. Water is a polar solvent with strong polarity. In addition to dissolution, it also has the combined effects of saponification, emulsification, displacement, dispersion, etc., and the use of ultrasound is much more effective than in organic solvents;
(4) As a natural solvent, its price is relatively low and its source is wide.
The disadvantages of water cleaning are:
(1) In areas where water resources are scarce, the cleaning method requires a large amount of water resources, which is limited by local natural conditions;
(2) Some components cannot be washed with water, and metal parts are prone to rust;
(3) The surface tension is large, it is difficult to clean small gaps, and the residual surfactant is difficult to remove thoroughly;
(4) Difficult to dry and consume more energy;
(5) The equipment cost is high, and the wastewater treatment device is required, and the equipment covers a large area.
2. Semi-water cleaning technology for PCB copy board
The semi-aqueous cleaning mainly uses an organic solvent and deionized water, plus a certain amount of a cleaning agent composed of an active agent and an additive. This type of cleaning is between solvent cleaning and water cleaning. These cleaning agents are organic solvents, are flammable solvents, have a relatively high flash point, are relatively low in toxicity, and are safe to use, but must be rinsed with water and then dried. Some cleaning agents add 5% to 20% water and a small amount of surfactant, which reduces flammability and makes rinsing easier.
The semi-water cleaning process features:
(1) The cleaning ability is relatively strong, and the polar pollutants and non-polar pollutants can be removed at the same time, and the washing ability is persistent;
(2) Washing and rinsing using two different media, rinsing generally uses pure water;
(3) Drying after rinsing.
The shortcoming of this technology is that waste liquid and wastewater treatment is a relatively complicated problem that needs to be completely solved.
3, PCB copy board no-clean technology
No-clean flux or no-clean solder paste is used in the soldering process. After soldering, it will not be cleaned directly into the next process. No-clean technology is currently the most used alternative technology, especially mobile communication products are basically free. Washing method to replace ODS. At present, many kinds of no-clean flux have been developed at home and abroad, such as Beijing No. 1 cleaning company.
No-clean fluxes can be broadly classified into three categories:
(1) Rosin type flux: Reflow soldering uses inert rosin solder (RMA) and is disposable.
(2) Water-soluble flux: Wash with water after welding.
(3) Low solid content flux: no cleaning.
No-clean technology has the advantage of simplifying the process flow, saving manufacturing costs and less pollution. In the past decade, the widespread use of no-clean soldering technology, no-clean solder and no-clean solder paste has been a feature of the electronics industry at the end of the 20th century. The ultimate way to replace CFCs is to achieve no-clean.
4. Solvent cleaning technology for PCB copy board
Solvent cleaning mainly uses the solvent to remove contaminants. Solvent cleaning, because of its fast evaporation, strong solubility, so the equipment requirements are simple. According to the selected cleaning agent, it can be divided into flammable cleaning agent and non-flammable cleaning agent. The former mainly includes organic hydrocarbons and alcohols (such as organic hydrocarbons, alcohols, glycol esters, etc.), and the latter mainly includes chlorine. Hydrocarbons and fluorinated hydrocarbons (such as HCFC and HFC).
HCFC cleaning agent and its cleaning process characteristics
This is a hydrogen-containing chlorofluorocarbon, which has low latent heat of vaporization, good volatility, easy decomposition in the atmosphere, and a relatively small effect of destroying the ozone layer. It is a transitional product and is required to be eliminated before 2040. Therefore, we This type of cleaning agent is not recommended.
There are two main problems: one is transitional. Because it has a destructive effect on the ozone layer, it is only allowed to be used until 2040; second, the price is relatively high, the cleaning ability is weak, and the cleaning cost is increased.
Chlorinated hydrocarbon cleaning process characteristics
Chlorinated hydrocarbons such as dichloromethane, trichloroethane, etc. are also non-ODS cleaning agents. Its cleaning process features are:
(1) The ability to clean grease and dirt is particularly strong;
(2) Like the ODS cleaning agent, it can also be washed by steam and vapor phase;
(3) The cleaning agent does not burn, does not explode, and is safe to use;
(4) The cleaning agent can be distilled and recycled, and it is economical to use repeatedly;
(5) The cleaning process is also the same as the ODS cleaning agent.
However, its shortcoming is that the toxicity of chlorinated hydrocarbons is relatively large, and the safety of workplaces needs special attention. Second, the compatibility of chlorinated hydrocarbons with general plastics and rubber is poor. Third, the stability of chlorinated hydrocarbons. Poor, always use stabilizer when using.
Hydrocarbon cleaning process characteristics
Hydrocarbons, that is, hydrocarbons, used gasoline and kerosene obtained by distilling crude oil as a cleaning agent. Hydrocarbons increase in flash point as carbon number increases, increasing safety, but poor drying; good drying and less safe use, so the two are very contradictory. Of course, as a cleaning agent, a cleaning agent with good fire safety and a relatively high flash point should be used. Its cleaning process features are:
(1) It has strong cleaning ability for grease and dirt, has long-lasting cleaning ability, and low surface tension, and has good cleaning effect on fine slits and fine pores;
(2) does not corrode the metal;
(3) It can be distilled and recycled, used repeatedly, and is economical;
(4) low toxicity and less environmental pollution;
(5) The same medium can be used for cleaning and rinsing, which is convenient to use.
The shortcomings of the hydrocarbon cleaning process, the most important is the safety issue, and there must be strict safety measures.
Alcohol cleaning process characteristics
Ethanol and isopropanol in alcohols are organic polar solvents commonly used in the industry. Methanol is more toxic and generally only used as an additive. The characteristics of the alcohol cleaning process are:
(1) It has good dissolving ability for ionic pollutants, and the effect of cleaning rosin flux is very good, and the ability to dissolve oils and fats is weak;
(2) It has good compatibility with metal materials and plastics, and does not cause corrosion and volume expansion;
(3) It is quick to dry, easy to dry or air dry, and it is not necessary to use hot air;
(4) Good dehydration, commonly used as a dehydrating agent.
The main problems of alcohol cleaning agents are high volatility, low flash point and easy burning. Explosion-proof measures must be taken for cleaning equipment and auxiliary equipment.Tag: PCB board