The performance of the PCB circuit board is directly related to the amount of visible and invisible residues between the pad and the hole in all areas of the active circuit. In a wet environment, ion pollution can cause many problems, such as the short circuit between the conductors caused by the growth of the crystal, or the direct corrosion of the conductor to reduce the surface impedance of the product. For PCB circuit board, to ensure the reliability of the product, monitoring the degree of ion pollution is particularly important.

The main pollutants that may be exposed to the production of integrated circuits are: particulate impurities, inorganic ions, organic matter, microorganisms and gas impurities. In a broad sense, the inappropriate temperature, humidity, illumination, over the limits of electrostatic electromagnetic noise, air noise and micro vibration, are also special pollutants. Among them, particulate impurities, inorganic ions, organic matter, microbe and quantity of gaseous impurities exceeds a certain limit, it will make integrated circuit products surface scratches, graphic break, short circuit, pinhole, peeling and other phenomena, resulting in leakage, the electrical characteristics of abnormal circuit. The light affects the performance and service life of the circuit. The processing precision of temperature, humidity, illumination and overrun of inappropriate static, vibration and noise not only affects the process and service life of equipment, but also affect the operator's mood, thereby affecting the integrated circuit product quality, production efficiency and yield, because of the pollution problems caused by the product failure rate could be as high as more than 60%. Therefore, the production of PCB circuit board must use a dedicated PCB circuit board cleaning agent for effective cleaning, so as to ensure the performance of the PCB circuit board.

For circuit board cleanliness test, including several methods:
Visual inspection: visual inspection is a relatively simple method of detection by the use of direct eye with a magnifying glass or microscope to observe the surface of the parts or the surface of the cavity can be checked. To identify whether the contaminated particles are metal, nonmetal or fiber, and its size. Visual inspection method is mainly used to check the residues on the surface of parts is relatively large and distinct particles, spots, rust and other pollution, the main drawback of this method is to check the result is easily affected by man-made interference.
Fluorescent method: the main use of ultraviolet light to detect the cleanliness of parts surface. Under UV irradiation, the surface of the pollutant particles will emit fluorescence. According to the fluorescence can be seen on the surface of the dirt on the surface of the parts, the fluorescence intensity can also be tested using a signal detector to indicate the degree of surface contamination. But if we want to identify the characteristics of pollutants, we must use other methods.
Contact angle: the so-called contact angle is the angle of the liquid in the thermodynamic equilibrium of the solid surface. The measurement of formation between solid and liquid contact angle, in adhesion, surface treatment and polymer surface analysis and many other similar fields for analysis of technology knowledge, is also very sensitive to changes in the surface layer of multiple units of analysis technology. The contact angle method is mainly used for surface cleanliness analyzer, it through the analysis of the surface contact by oil pollution, glass chip, PCB board and other materials (water contact angle) and the angle difference between glass and chip angles, methods to evaluate the cleanliness of glass, PCB chip, board.
Weighing method: weighing method is a kind of industrial production and test commonly used in the cleanliness of the test method. It is also the most commonly used testing method in our laboratory. The principle of the test is to use the selected cleaning liquid to clean a certain number of samples under certain conditions. After cleaning the liquid through a certain pore size of the membrane filter (commonly used membrane pore diameter of 5 m, 10 m, 20 m, 30 m, etc.), the dirt is collected on the surface of the membrane. The filter membrane before and after filtration was weighed, the difference between the two weighing, that is, the weight of pollutants.
Particle size method: a new method for measuring the cleanliness of parts. The basic principle is to have different light absorption or scattering rate according to the detected surface and pollutant particles. The testing method is: processing method and gravimetric method, to filter paper after drying, using a microscope (the best equipment is image recognition and analysis device camera) detection in the light irradiation, get solid particles results in parts of the grain size and the area can be. The utility model is suitable for the quantitative cleaning method for cleaning precision, and is especially suitable for the detection of small particles and colored impurity particles. However, if the filter is white, then the identification of white dirt and bubbles may cause miscarriage of justice.
NaCl equivalent method: the amount of conductive ions in the solution can be expressed simply by the conductivity of the solution. According to the known amount of NaCl in the extraction solution, the conductivity of the ion can be given simply. The specific operation is as follows: every 250mm2 of the printed board with 100ml solution in a small amount of flushing, until the solution is collected in the beaker (the process requires at least 1min). Measurement of resistivity of solution by conductivity tester. As a result, the output is expressed as a NaCl equivalent per square centimeter area.
Ion chromatography: according to the different ions in the mobile phase and the stationary phase of the adsorption and desorption of different degrees, the adsorption time of ions through the adsorption column is different, so as to achieve ion separation. Then, according to the ion peak area, the concentration of the detected ions was calculated. Isopropanol was used as extractant to extract the ions to be tested on PCB and then detected by ion chromatography.