Generally, these different types of pollutants can be divided into polar pollutants, non-polar pollutants and particulate pollutants.
(1) polar pollutants.A substance that can be ionized into ions under certain conditions and whose molecules have eccentric electron distribution.Halides, acids and salts are polar contaminants and are primarily activators in flux.Positive or negative ions are produced when molecular ions of polar pollutants are present.This ion is a good conductor and can cause circuit failure.Under certain voltages, such ions migrate to conductors of opposite polarity, and because of the hygroscopicity of polar pollutants, they absorb water and accelerate their dissolution under the action of carbon dioxide in the air.The chain reaction of these ionic carriers will produce a conductive effect, resulting in corrosion of PCB wires.
(2) non-polar pollutants.These are compounds that have no eccentric electron distribution, do not separate into ions, and do not carry an electric current. They are mainly residues of organic compounds left in the flux, anti-oxidation oils used in wave solder tanks, residual tape, and oil slicks.In general, non-polar pollutants are insulators that do not cause corrosion and electrical failure.However, due to its high viscosity, it will absorb dust, so it will affect the solderability. If it is covered on the solder joint, it may hinder the electrical test of the solder joint.
It should be noted that most residual pollutants are mixtures of nonpolar substances and polar substances.
(3) particulate pollutants.Mainly from the air in the material, organic residues and so on.Dust, smoke, electrostatic particles and other particulate pollution, they will also damage the performance of printed circuit board components.
The above is the information provided by China PCB board factory. I hope it is helpful to you.