The chemical performance requirements of PCB manufacturers mainly include board surface cleanliness, solvent resistance and flux resistance.

(1) Surface cleanliness of PCB processing manufacturers The surface cleanliness of PCB is also called ion pollution. Cleanliness directly affects the surface insulation resistance of the board and the service life of the circuit board. Poor cleanliness and serious ion pollution will reduce the solderability and surface insulation resistance of the printed circuit board, and lead to the corrosion of the conductor in the humid environment, which will affect the life of the printed circuit board. Especially for high-density wiring boards with thin wires and small spacing, the impact is more obvious. Therefore, the pcb processing board must be strictly cleaned before and after coating solder mask to meet the specified cleanliness requirements.

Cleanliness is to clean the surface of PCB without solder mask by chemical extraction solution (isopropanol water extraction solution with resistivity greater than 6M Ω· cm is usually used). The resistivity of the extracted solution should be greater than 2M Ω· cm, or equivalent to 1.56 μ G/cm2 sodium chloride equivalent. During measurement, attention shall be paid to the environmental cleaning and operation methods to prevent secondary pollution from affecting the measurement results.

(2) Solvent resistance and flux resistance The solvent resistance and flux resistance of PCB manufacturers' circuit boards refer to the ability of insulating coatings (including solder mask, characters, marks, etc.), flux resistance and cleaning solvent of printed boards. Generally, the printed boards with insulation coating shall be cleaned according to the solvents and methods specified in the contract or standard test methods. The marks, characters and solder mask after the test shall meet the following requirements: no damage to the marks; If the mark is not clear but can be recognized, similar letters will not be confused (such as D-P - B, E - F, C - G - O); The solder mask shall be free of bubble and delamination; No printing material falls off.