Circuit Board Cleaning Technology

From %"PCB Technology Forum%"

Board generation of clean technology are the following four:

A semi-aqueous cleaning technology

　Semi-aqueous organic solvent is mainly used to clean and de-ionized water, coupled with a certain amount of the active agent, the additive consisting of cleaning agents. Between such cleaning solvent cleaning and water. These cleaning agents are all the organic solvents, are flammable solvents, relatively high flash point, low toxicity, safe use, but must be rinsed with water, and then dried. Some cleaners add 5% to 20% water and a small amount of surfactant, not only reduces the flammability, but also make more easily rinsed. Semi-aqueous cleaning process is characterized by:

　　1) cleaning capacity is relatively strong, it could also remove contaminants polar and non-polar pollutants persistent strong cleaning ability; 

2) washing and rinsing using two different kinds of media, the general use of rinse water; 

3) After rinsing to be dried. 　　

Shortcomings of the technology lies in waste and wastewater treatment is a more complex and has yet to solve the problem.

2, water cleaning technology

　Water cleaning technology is the future direction of development of clean technologies shall be provided with clean water and pure water treatment plant discharge. Using water as a cleaning medium, and adding a surfactant in water, additives, corrosion inhibitors, chelating agents, or the like a series of water-based cleaning agent. Aqueous solvent can be removed and a non-polar contaminants. Its cleaning process is characterized by:

　1) safety, no burning, no explosion, non-toxic; 

2) the composition of detergent formulations large degree of freedom of polar and non-polar contaminants are easily washed, cleaned wide range;

 3) multiple cleaning mechanism. Water is a very polar polar solvents, in addition to the dissolution, there saponification, ^^^ of, displacement and dispersion interaction, much more effective than the use of ultrasound in an organic solvent;

 4) as a natural solvent its price is relatively low, wide variety of sources.

Disadvantages water cleaning is:

1) In the area of water shortage, because the cleaning method requires large amounts of water, which is restricted to local natural conditions; and

 2) sector element can not be cleaned with water, lightly rusted metal parts; 

3) surface tension, cleaning small gaps have problems, residual surfactant is difficult to remove completely; 

4) dry hard, large energy consumption; 

5) the high cost of equipment, you need the wastewater treatment plant, equipment larger area.","

3, no-clean technology

　　During the welding process using no-clean flux or no-clean solder paste directly into the next process after soldering is no longer clean, no-clean technology is currently the most used an alternative technology, especially mobile communications products are basically using free wash method to replace ODS. Currently at home and abroad have developed a variety of no-clean flux is good, at home, such as Beijing Jing Ying's no-clean flux. No-clean flux can be broadly divided into three categories:

　1) Rosin Flux: reflow soldering using inert rosin solder (RMA), can be disposable.

 2) Water-soluble flux: clean water after welding. 

3) low solid content flux: no-clean. 　　

Free cleaning technology has simplified the process, saving manufacturing costs and less pollution strengths. Over the past decade, no-clean soldering technology, no-clean flux and the widespread use of no-clean solder paste, is a major feature of the 20th century the electronics industry. The ultimate way to replace CFCs is to achieve no-clean.

4, solvent cleaning technology

Solvent cleaning is the use of the dissolving power of the solvent to remove contaminants. Solvent cleaning, because of its volatile fast, strong ability to dissolve, so the simple equipment requirements. According to the selection of cleaning agent, the cleaning agent can be divided into combustible and non-flammable cleaning agent, the former including organic hydrocarbons and alcohols (such as organic hydrocarbons, alcohols, glycol esters, etc.), the latter mainly comprising chlorine hydrocarbons and fluorocarbons (e.g., HCFC and HFC's) and the like.

HCFC type cleaning agents and cleaning processes characteristic which is a hydrogen-containing HCFCs, its latent heat of evaporation is small, volatility is good, easy to break down in the atmosphere, ozone-depleting effect is relatively small, is a transitional product, designated In 2040 before the scheduled phase-out, so we do not recommend the use of such cleaning agents. Its existence has two main topics: First interim. Due to the destruction of the ozone layer as well as the role of, only promised to use to 2040; Second, the price is relatively high, cleaning capacity is weak, increased cleaning costs.

Cleaning process characteristics of chlorinated hydrocarbons

　　Chlorinated hydrocarbons such as methylene chloride, trichloroethane, also belong to non-ODS cleaning agent. Its cleaning process is characterized by:

　1) the ability to clean greasy dirt particularly strong 

2) as ODS cleaning agent as to be washed with steam and air drying 

3) a cleaning agent is not burning, no explosion, safe;

 4) a cleaning agent can be recovered by distillation, repeated use more economical 

5) cleaning process is also the same with the ODS cleaning agent. 　　

However, one drawback toxic chlorinated hydrocarbons is relatively large, security issues in the workplace require special attention; second, chlorinated hydrocarbons and general plastics, rubber, poor compatibility; three chlorinated hydrocarbons in chaos the relatively poor, we must add chaos agents use.

Hydrocarbon cleaning process characteristics

　　Hydrocarbons, i.e. hydrocarbons, in the past the oil obtained by distillation of gasoline, kerosene used as a cleaning agent. Hydrocarbons increases with the number of carbon and flashpoint progress, increased safety, but bad dry; dry and good, but not too safe use, so the two very contradictory. Of course, as a cleaning agent should try to use good fire safety, relatively high flash point cleaner. Its cleaning process is characterized by:

　1) for cleaning greasy dirt strong, durable and strong cleaning ability and low surface tension of the slit pore department cleaning effect;

2) metal without erosion; 

3) can be recovered by distillation, repeated use more economical

 4) less toxic, less environmental pollution;

 5) cleaning and rinsing the same kind of media available, use convenient. 　　

Hydrocarbon cleaning process shortcomings, the most important is the safety of the subject, have strict security precautions.

Alcohol cleaning process characteristics:

　　Alcohols, ethanol and isopropanol are commonly used in industry to give an organic polar solvent, methanol greater toxicity, generally do only additive. Alcohol cleaning process is characterized by:

　　1) ion contaminants have good solubility, clean rosin flux effect is very good, dissolve fats and oils weak;

 2) with metals and plastics, such as compatibility, no erosion and capacity expansion; 

3 ) fast drying, easy to dry or air dry, without the use of hot air. 

4) Good dehydration, often used for dehydrating agent.

　　The main subject of alcohol cleaning agents are volatile large, low flash point, easy to burn, it is necessary to take measures against explosion cleaning equipment and auxiliary equipment.