Regardless of the performance of the soldering flux, it will be more or less corrosive. The residue after soldering the circuit board can cause different problems such as corrosion, leakage, and ion migration. Therefore, removing the residue of soldering flux will certainly be regarded as an important processing task by the industry. And what is the actual effect of the processing? Appropriate methods are also needed for verification and tracking in this regard. The cleaning effect of PCB circuit board after soldering should be based on the amount of residual ion residue at the solder joints. The specification adopted by MIL is MIL-P-2880955110, which should have a resistivity of 6MQ-cm or above during testing. Calculate the resistivity of the measured metal per unit area and after quantitative cleaning. In terms of cleanliness, the resistivity should be maintained above 2MQ-cm.

　　Representative cleanliness testing methods include Ion Ogurafu and Omega Meter, which are recognized as convenient methods for measuring cleanliness in MIL specifications. The principle of any method is that the residual ionic dirt on the solder joint after cleaning treatment is extracted through a solvent to measure its conductivity change as an indicator.

　　The cleanliness measurement method of Ion Ogufafu method is to immerse the measured metal in a high resistivity solution (lsoburobiru arukoru 75% distilled water 25%), extract the ionic substances in the pollutants, and determine the cleanliness through the change in conductivity of the solution. The cleanliness index is based on the calculated equivalent of sodium chloride, which represents the ion contamination level (ug NaCI/cm2). If the residue cannot dissolve in lsoburobiru arukuru, this method cannot determine the degree of contamination.