PCBA Tech - What are the main pollution produced in PCBA processing?

PCBA pollution will have an adverse effect on the reliability and stability of the circuit board. In order to improve the reliability and quality of the product in PCBA processing, Wanlong Lean will strictly control the production process and technology, and clean up the PCBA pollution in time to ensure the product. Quality and reliability.

What are the main pollution produced in PCBA processing-PCBA pollutants

The main hazards of PCBA pollution are: it may directly or indirectly cause potential risks of PCBA, such as the organic acid in the residue may cause corrosion to PCBA; the electric ions in the residue may be caused by the potential difference between the two pads during the electrification process. It will cause the movement of electrons, which may form a short circuit and cause the product to fail; the residue will affect the coating effect, and cause problems such as inability to coat or poor coating; it may also be temporarily undetectable, elapsed time and environmental temperature changes, Coating cracks and peeling occur, causing reliability problems.

Pollutants are defined as any surface deposits, impurities, slag inclusions and adsorbed substances that reduce the chemical, physical or electrical properties of PCBA to unacceptable levels. There are mainly the following aspects:

1, the components that make up the PCBA, the pollution or oxidation of the PCB itself, etc. will bring the PCBA board surface pollution;

2. In the PCBA manufacturing process, solder paste, solder, solder wire, etc. need to be used for soldering. The flux will produce residues on the PCBA board surface during the soldering process to form pollution, which is the main pollutant;

3. Hand marks will be produced during the manual soldering process. The wave soldering process will produce some wave soldering claw footprints and soldering tray (fixture) marks. There may also be other types of contaminants on the PCBA surface of different degrees, such as blockages. Hole glue, residual glue of high temperature tape, handwriting and flying dust, etc.;

4. Pollution caused by dust, water and solvent vapors, smoke, tiny particles of organic matter, and charged particles attached to PCBA caused by static electricity in the workplace.

The above shows that the pollutants mainly come from the assembly process, especially the welding process.

During the welding process, a thin oxide film will be produced when the metal is heated, which will hinder the infiltration of the solder and affect the formation of the solder joint alloy, which is prone to false soldering and false soldering. The flux has the function of deoxidation, it can remove the oxide film of the pads and components to ensure the smooth progress of the soldering process. Therefore, flux is needed in the soldering process, and the flux plays a vital role in the formation of good solder joints during the soldering process, and sufficient plated through-hole filling rate plays a vital role.

The role of flux in soldering is to remove oxides on the soldering surface of the PCB board to make the metal surface reach the necessary cleanliness, destroy the surface tension of the molten tin, prevent the solder and soldering surface from re-oxidizing during soldering, increase its diffusion force, and help heat Pass to the welding zone.

The main components of flux are organic acids, resins and other components. The high temperature and complex chemical reaction process changed the structure of the flux residue.

Residues are often polymers, halides, and metal salts produced by the reaction with tin-lead. They have strong adsorption properties, but have very poor solubility and are more difficult to clean.