• Manual Cleaning Method
Acetone solution is used to soak PCB boards for about 10 minutes. Then, a banister brush is used to brush off contaminants at solder connection in ethanol solution. Next, board is taken out before deionized water is used to wash for 3 minutes. After that, absolute ethyl alcohol is leveraged for dehydration. Finally, nitrogen gas gun is used to dry the board surface until no water mark won't be seen.
During the process of manual cleaning, acetone with higher solubility is leveraged to soak circuit boards, which can effectively make contaminants dissolved into the solution. Then circuit board goes over physical brushing by placing circuit boards in ethyl alcohol with detailed flux contaminants brushed off. Next, organic solvent has to go through dehydration with the help of deionized water. Finally, nitrogen gas is used to dry the board surface to complete manual cleaning after surface mount soldering. This process can be summarized into the following figure.
• Ultrasonic Cleaning Method
Acetone solvent is used in ultrasonic cleaning method. First, PCB board is soaked into acetone solvent for ten minutes. Then, it is placed into quartz container specialized for absolute ethyl alcohol in which circuit board is soaked. Next, ultrasonic cleaning is implemented after placing quartz container into ultrasonic cleaning tank. Ultrasonic cleaning lasts for five minutes with ultrasonic power of 240W, after which quartz container is taken out with a basket after turning off ultrasonic cleaning switch. Then, deionized water is used to wash for 5 minutes and absolute ethyl alcohol is used to carry out dehydration on circuit board. Finally, nitrogen gas is used to make the surface dry.
During the process of ultrasonic cleaning, circuit board is put into ethyl alcohol agent, which is different from manual cleaning. Depending on the principle of ultrasonic vibration, ultrasonic cleaning aims to wash off flux residue and dehydration is carried out by deionized water. Finally comes drying stage with the help of nitrogen gas. The whole procedure of ultrasonic cleaning is demonstrated in the following figure.
• Gas Phase Cleaning Method
Equipment condensing system is turned on first to let it run for 5 to 10 minutes. Then, equipment heating system is turned on to heat cleaning agent to boiling temperature. circuit board is placed into cleaning basket that is then placed into boiling tank. Boiling time lasts for 3 to 5 minutes. Next, basket is then placed into steam zone for steam cleaning for 3 to 5 minutes. Then, circuit board surface is sprayed with cleaning agent for 10 to 20 seconds. After that, basket is slightly placed into rinsing tank for 1 to 2 minutes. Finally, devices are dried through condensation and basket is taken out after the complete volatilization of agent.
When PCB board is placed into the steam of hot agent, hot steam will be condensed on the surface of circuit board that is relatively cold in surface, leading grease dirt on PCB component surface to be dissolved. Dissolved grease dirt is dipped into boiling agent while steam is accumulated on condensation coil that is around boiling agent. Steam will return to separation cell in a liquid state that can be recycled with water separated and impurity filtered. Agent gas phase cleaning principle is indicated by the following figure.
Comparison between All Cleaning Methods
By comparing manual cleaning, ultrasonic cleaning and gas phase cleaning methods on PCBs after surface mount soldering through observing PCB traces and surface situation, it can be concluded that flux residues can be fundamentally and completely washed off PCB board surface through organic solvent cleaning. Manual cleaning and ultrasonic cleaning, however, sometimes still maintain flux residues on some parts of PCB board. Therefore, comprehensive analysis leads to the conclusion that organic solvent cleaning equipment should be picked up due to its higher reliability, lower toxicity and higher security so that cleaning can become thorough with better cleaning effects generated.
All in all, electronics assembly capabilities are not limited within manufacturing and assembly technology range. Flux electronics, however, is also an inevitable aspect as far as board soldering and soldering PCB are concerned, which plays an essential role in determining the reliability and functionality of final electronics products.