PCB Blog - Printed circuit boards cleaning technology of PCB copy board

As we all know, p rinted circuit boards cleaning technology plays a very important role in PCB copying. Since it is necessary to ensure the cleanliness of the circuit board itself to accurately scan and generate the document map, the cleaning technology of the circuit board has also become an important "technical activity". Wang Gaogong, the engineer of Jieduobang, mainly summarizes the current technology. Four ways of the new generation of circuit board cleaning technology are presented.

1. Water cleaning technology for PCB copy board
Water cleaning technology is the development direction of cleaning technology in the future, and pure water sources and discharge water treatment workshops must be set up. It uses water as the cleaning medium, and adds surfactants, additives, corrosion inhibitors, chelating agents, etc. to the water to form a series of water-based cleaning agents. Aqueous solvents and non-polar contaminants can be removed. Its cleaning process features are:
(1) Good safety, non-flammable, non-explosive, basically non-toxic;
(2) The formulation of the cleaning agent has a large degree of freedom, and it is easy to clean off both polar and non-polar pollutants, and the cleaning range is wide;
(3) Multiple cleaning mechanisms. Water is a polar solvent with strong polarity. In addition to dissolving, it also has the joint effects of saponification, emulsification, displacement, dispersion, etc. The use of ultrasound is much more effective than in organic solvents;
(4) As a natural solvent, its price is relatively low and widely used.

The disadvantages of water cleaning are:
(1) In areas where water resources are scarce, because this cleaning method needs to consume a lot of water resources, it is limited by local natural conditions;
(2) Some components cannot be cleaned with water, and metal parts are easy to rust;
(3) The surface tension is large, it is difficult to clean small gaps, and it is difficult to completely remove the residual surfactant;
(4) It is difficult to dry and consumes a lot of energy;
(5) The equipment cost is high, a wastewater treatment device is required, and the equipment occupies a large area.

2. Semi-water cleaning technology of PCB copy board
Semi-aqueous cleaning mainly uses organic solvents and deionized water, plus a certain amount of active agents and additives. This type of cleaning is between solvent cleaning and water cleaning. These cleaning agents are all organic solvents, which are flammable solvents, with relatively high flash point and low toxicity, and are relatively safe to use, but they must be rinsed with water and then dried. Some cleaning agents add 5% to 20% water and a small amount of surfactant, which not only reduces flammability, but also makes rinsing easier. The characteristics of the semi-aqueous cleaning process are:
(1) The cleaning ability is relatively strong, it can remove polar pollutants and non-polar pollutants at the same time, and the cleaning ability is durable;
(2) Two different media are used for cleaning and rinsing, and pure water is generally used for rinsing;
(3) Dry after rinsing. The disadvantage of this technology is that the treatment of waste liquid and wastewater is a relatively complex and yet to be completely solved problem.

3. No-clean technology for PCB copy board
No-clean flux or no-clean solder paste is used in the soldering process. After soldering, it goes directly to the next process without cleaning. No-clean technology is an alternative technology that is currently used more often, especially for mobile communication products. Washing method to replace ODS. At present, many kinds of no-clean flux have been developed at home and abroad, such as Beijing Jingying company's no-clean flux. No-clean fluxes can be roughly divided into three categories:
(1) Rosin-type flux: use inert rosin solder (RMA) for reflow soldering, which can be dispensed with.
(2) Water-soluble flux: wash with water after welding.
(3) Low solid content flux: no cleaning. No-clean technology has the advantages of simplifying the process flow, saving manufacturing costs and less pollution. The widespread use of no-clean soldering technology, no-clean fluxes and no-clean solder pastes has been a major feature of the electronics industry at the end of the 20th century in the past decade. The ultimate way to replace CFCs is to achieve no-clean.

4. Solvent cleaning technology for PCB copy board
Solvent cleaning mainly uses the solvency of the solvent to remove contaminants. Using solvent cleaning, because of its fast volatilization and strong dissolving ability, 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 Substituted hydrocarbons and fluorohydrocarbons (such as HCFC and HFC), etc.

HCFC cleaning agent and its cleaning process characteristics: This is a kind of hydrogen-containing chlorofluorocarbons with low latent heat of evaporation, good volatility, easy decomposition in the atmosphere, and relatively little effect on destroying the ozone layer. It is a transitional product. It is stipulated that it will be phased out before 2040, so we do not recommend the use of this type of cleaning agent. There are two main problems: one is transition. Because it has a damaging effect on the ozone layer, it is only allowed to be used until 2040. Second, the price is relatively high, and the cleaning ability is weak, which increases the cleaning cost.

Chlorinated hydrocarbons such as dichloromethane, trichloroethane, etc. are also non-ODS cleaning agents. Its cleaning process features are:
(1) The ability to clean oily dirt is particularly strong;
(2) Like ODS cleaning agent, it can also be washed with steam and dried in vapor phase;
(3) The cleaning agent is non-flammable, non-explosive and safe to use;
(4) The cleaning agent can be recovered by distillation and used repeatedly, which is more economical;
(5) The cleaning process is also the same as that of ODS cleaning agent. However, its disadvantages are: First, the toxicity of chlorinated hydrocarbons is relatively high, so special attention should be paid to safety issues in the workplace; second, the compatibility of chlorinated hydrocarbons with general plastics and rubber is poor; third, chlorinated hydrocarbons are stable in terms of stability. Relatively poor, must add stabilizer when using.

Hydrocarbon cleaning process features: Hydrocarbons are hydrocarbons, gasoline and kerosene obtained by distillation of crude oil were used as cleaning agents in the past. The flash point of hydrocarbons increases with the increase of carbon number, which increases the safety, but the drying is not good; the drying is good, but it is not safe to use, so the two are very contradictory. Of course, as a cleaning agent, you should try to choose a cleaning agent with good fire safety and high flash point. Its cleaning process features are:
(1) It has strong cleaning ability for oily dirt, strong cleaning ability and durability, and low surface tension, and has good cleaning effect on fine slits and pores;
(2) No corrosion to metals;
(3) It can be recovered by distillation and used repeatedly, which is more 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 disadvantage of the hydrocarbon cleaning process is mainly the safety issue, which requires strict safety measures.

Among the alcohols, ethanol and isopropanol are commonly used organic polar solvents in the industry. Methanol is more toxic and is generally only used as an additive. The characteristics of alcohol cleaning process are:
(1) It has good dissolving ability to ionic pollutants, and the cleaning effect of rosin flux is very good, but the dissolving ability to grease is weak;
(2) Good compatibility with metal materials and plastics, no corrosion and expansion;
(3) Fast drying, easy to dry or air drying, no need to use hot air;
(4) Good dehydration, commonly used as dehydrating agent. The main problems of alcohol-based cleaning agents are high volatility, low flash point, and easy combustion. Explosion-proof measures must be taken for printed circuit boards cleaning equipment and auxiliary equipment.