How Many Solutions To Use In Your PCB Cleaning ?
In the process of PCB copy board, We need to scan the pcb accurately .so we must make sure that it is clean enough and no dust.therefore, the circuit board cleaning techniques to master is also very important.
For now, the new generation of cleaning technology circuit board has the following four ways:
- Water cleaning technology
- Half-water (water-based) cleaning technology
- No-cleaning technology
- Solvent cleaning technology
NO.1 Water cleaning technology
Water cleaning technology is the future direction of development.It shall be provided workshop that used to store and discharge water. Washing it with water as a medium, and adding a surfactant in water, additives, corrosion inhibitors, chelating agents, such as forming a series of water-based cleaning agent. To remove non-polar solvent and water contamination.
The cleaning process is characterized by:
- Safe,No burning, No exploding,Non-toxic;
- Detergent formulation can mix freedom, the polar and nonpolar pollutants are easy to wash, Cleaning range is extensive;
- Multiple cleaning mechanism. Water is a very strong polar solvent polarity, in addition to the solution, saponification, emulsifying, replacement, dispersion, such as interaction, using ultrasound is more effective than in the organic solvent;
- As a natural solvent, its price is cheap and easy to get.
The disadvantage of water cleaning:
- In the area of water shortage ,because the cleaning method requires large amounts of water, which is restricted to local natural conditions;
- Some components can not be washed by water,and the metal parts is so easy to rust .
- It is difficult to clean a small gap and can not remove the residual surfactant completely;
- Drying difficult, large energy consumption;
- The cost of equipment is too high, you need to waste water tretment plants and the equipment need a big floor area.
NO.2 Semi-aqueous (water-based) cleaning technology
Semi-aqueous is a cleaning agent which use mainly organic solvent and deionized water and adding a quantity of the active agent, addition agent. This cleaning way is between solvent cleaning and cleaning water.
Semi-aqueous is belong to flammable solvents. Relatively high flash point. Toxicity is relatively low. So it is safe. but you must be rinsed with water and then dried.Some cleaning agent added 5% to 20% water and a small amount of a surfactant, which lowered the flammability, but also make rinsing easier.
Semi-aqueous cleaning process is characterized by:
- strong cleaning ability, it can simultaneously remove contaminants polar and non-polar contaminants, cleaning ability persistent strong;
- Cleaning and rinsing are using two different types of media ,commonly used rinsing water;
- To be rinsed and dried.
The lack of this technology is the waste and waste water treatment Which is a more complex problem and not yet completely solved.
NO.3 NO-clean flux
During the welding process using no-clean flux or no-clean solder paste. It is direct into the next process after welding and no longer clean. Free cleaning technology is an alternative to using the most current technology, especially mobile communications products are basically using disposable alternatives to ODS. So far,it has developed a variety of no-clean flux at home and abroad.
Clean flux can be broadly divided into three categories:
- Rosin Flux: As a main component in a mixture of rosin (RMA) and no cleaning.
- water-soluble flux: It need to clean after welding.
- low solid content Flux: No cleaning.
No cleaning technology has simplified the process, saving manufacturing costs and less pollution advantages. Over the past decade, no-clean soldering technique, no-clean flux and no-clean solder paste is commonly used in the late 20th century and is a major feature of the electronics industry. The ultimate way to replace CFCs is to achieve no cleaning.
NO.4 Solvent cleaning
Solvent cleaning is the use of a solvent dissolving power to remove contaminants. Using solvent cleaning, due to its volatile fast dissolving ability, so the equipment requirements simple. According to an optional cleaning agent, the cleaning agent into combustible and non-flammable cleaning agents, the former including organic hydrocarbons and alcohols (such as organic hydrocarbons, alcohols, glycol esters, etc.), which include chloro hydrocarbons and fluorocarbons (such as HCFC and HFC’s).
HCFC cleaning agent and cleaning process characteristics:
This is a hydrogen-containing HCFCs, its latent heat of vaporization of small, volatile good, easy to decompose in the atmosphere, damaging the ozone layer is relatively small, belongs to a transitional product, defined in 2040 before the elimination, so we not recommend the use of such cleaning agents, which have two main problems: First, transitional. Because there are damaging effects on the ozone layer, allowing only the use of the 2040; Second, the price is relatively high, the cleaning capacity is weak, increased cleaning costs.
Cleaning process characteristics chlorinated hydrocarbons:
Chlorinated hydrocarbons such as dichloromethane, trichloroethane ,etc. And belong to non-ODS cleaning agent. Its cleaning process characterized as below:
- The ability to clean greasy and dirt is so strong;
- The same as the ODS cleaning agent ,It also can be washed with steam and dried wiht air;
- This cleaning agent is no burning, no explosion and very safe;
- The cleaning agent can be recycled by distillation and used repeatedly, that is very economical;
- Cleaning process is also the same with the ODS cleaning agent.
However, the drawback is :First,Chlorinated hydrocarbon toxicity is relatively large adn the workplace safety issues need to be required special attention; Second, chlorinated hydrocarbons is poor compatibility with general plastics, rubber, ; Third, the stability of the chlorinated hydrocarbons is relative poor, we must add stabilizers use.
Hydrocarbon cleaning process characteristics:
They obtained the gasoline ,kerosene by distillation from the oil used as a cleaning agent. Hydrocarbons increases with the number of carbon and improved flash point, increase security, but not dry; drying and good, but not too safe use, so the two are very contradictory. Of course, as a cleaning agent should try to use good fire safety, relatively high flash point of the cleaning agent.