Cleaning technology of printed circuit board and copy board

Cleaning technology of printed circuit board and copy board
As we all know, P printed circuit board cleaning technology plays a very important role in PCB reproduction Because it is necessary to ensure the cleanliness of the circuit board itself to accurately scan and generate file maps, the cleaning technology of the circuit board has also become an important "scientific and technological activity" Wang Gaogong, an engineer of Jieduobang, mainly summarized the current technology Four methods of new generation circuit board cleaning technology are introduced
1 Water cleaning technology for PCB copy board
Water cleaning technology is the development direction of cleaning technology in the future It uses water as cleaning medium and adds surfactants, additives, corrosion inhibitors, chelating agents, etc A series of water-based cleaning agents are formed based on water It can remove water solvent and non-polar pollutants Its cleaning process features are:
(1) Good safety, nonflammable, non explosive, basically non toxic;
(2) The formulation of the cleaning agent has a large degree of freedom, and the cleaning range is wide;
(3.) Multiple cleaning mechanisms.  Water is a polar solvent with strong polarity In addition to dissolution, it also has the combined action of saponification, emulsification, substitution, 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 it is widely used
PCB board

The disadvantages of water cleaning are:
(1) In areas where water resources are scale, 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, and it is difficult to completely remove the residual surface;
(4) It is difficult to dry and consumes a lot of energy;
(5) The equipment cost is high, which requires wastewater treatment equipment and covers a large area
2. Semi-water cleaning technology of PCB copy board
Semi aqueous cleaning mainly uses organic solvents and deionized water This cleaning is between solvent cleaning and water cleaning These cleaners are organic solvents, which are flammable solvents with high flash point and low toxicity. They are relatively safe to use, but they must be washed with water and then dried Some cleaning agents add 5% - 20% water and a small amount of surfactant, which not only reduces the flammability, but also makes flushing easier The characteristics of the semi-aqueous cleaning process are:
(1) The cleaning ability is relatively strong, which can simultaneously remove polar pollutants and non-polar pollutants, and the cleaning ability is dual;
(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 problem that has not been completely solved
3. No-clean technology for PCB copy board
No-clean flux or no-clean solder paste is used in the soldering process.  After welding, directly enter the next process without cleaning No clean technology is an alternative technology, which is now used more frequently, especially for mobile communication products Alternative ODS cleaning method At present, many kinds of non cleaning fluxes have been developed at home and abroad, such as those of Beijing Jingying Company No-clean fluxes can be roughly divided into three categories:
(1) Rosin type flux: use liner rosin solver (RMA) for reflow solver, which can be exempted
(2) Water-soluble flux: wash with water after welding.
(3) Low solid content flux: no cleaning.  No clean technology has the advantages of simplifying process flow, saving manufacturing cost and reducing pollution Non clean soldering technology is widely used. In the past decade, non clean flux and non clean solder paste are the main features of the electronic industry at the end of the 20th century The ultimate way to replace CFCs is to achieve no cleaning
4. Solvent cleaning technology for PCB copy board
Solvent cleaning mainly uses the solvency of the solvent to remove contaminants.  Use solvent for cleaning. Because of its fast volatilization and strong solubility, the equipment requirements are very simple According to the selected cleaning agent, it can be divided into flammable cleaning agent and nonflammable cleaning agent The former mainly includes organic hydrocarbons and alcohols (such as organic hydrocarbons, alcohols, ethylene glycol esters, etc.), and the latter mainly includes chlorine Substituted hydrocarbons and fluorohydrocarbons (such as HCFC and HFC), etc
Fluorochlorocarbon cleaning agent and its cleaning process characteristics: it is a hydrochlorofluorocarbon with low latent heat of evaporation, good volatility, easy to decompose in the atmosphere, and relatively little damage to the ozone layer This is a transitional product It is stipulated that the detergent will be phased out before 2040. In retrospect, we do not recommend using this detergent There are two main problems: First, transition Because of its destructive effect on the ozone layer, it is only allowed to be used until 2040 Second, the price is relatively high and the cleaning capacity is weak, which increases the cleaning cost
Chlorinated hydrocarbons, such as dichloromethane, 3-chloroethane, etc It is also a non ODS cleaner 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. In conclusion, special attention should be paid to the safety of the workplace; Second, chlorinated hydrocarbons have poor compatibility with general plastics and rubber; Third, chlorinated hydrocarbons are stable in terms of stability Relatively poor, stabilizer must be added when using
Hydrocarbon cleaning process features: hydrocarbons are hydrocarbons. In the past, gasoline and kerosene obtained from crude oil distillation were used as cleaning agents The flash point of hydrocarbons increases with the increase of carbon number, which increases the safety, but the drying is not good; It is dry, but it is not safe to use, so the two are very conflicting Of course, as a cleaner, you should try to choose a cleaner with good fire resistance and high flash point Its cleaning process features are:
(1) It has strong cleaning ability for oil dirt, powerful cleaning ability and durability, and has good cleaning effect on fine slits and points;
(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 ringing The main disadvantage of hydrocarbon cleaning process is safety, which requires strict safety measures
In alcohol, ethanol and isopropanol are organic polar solvents commonly used in industry Methanol is more toxic and is usually used only as an additive The characteristics of alcohol cleaning process are:
(1) It has good removing ability to ionic polymers, but the removing ability to grease is weak;
(2) Good compatibility with metal materials and plastics, no corrosion and expansion;
(3) Fast 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 Exploration proof measures must be taken for PCB cleaning equipment and auxiliary equipment