Inspiration and Suggestion from Corrosion Failure of PCBA Components to Wave Soldering Lead-free Solder Bars.

     Due to the lack of post-soldering cleaning process, the use of no-clean flux in wave soldering lead-free solder bars has the risk of high surface ion content. If there are certain defects in the solder mask or green oil plug holes, under the action of a continuous electric field, the accumulated corrosive ions will gradually penetrate through the solder mask and corrode the copper layer, resulting in a series of defects in lead-free solder products. Even without the action of an electric field, high surface ion residues will cause corrosion to the solder joints on the surface of PCB components, thereby affecting the reliability of lead-free solder bars and even all lead-free solder products. To prevent such failures, the following proactive preventive measures should be taken:

(1) Ensure that the cleanliness of the PCBA, especially the ion cleanliness, meets the specified standard requirements.

(2) Strengthen the control of PCB to ensure its structural integrity.

(3) Try to use halogen-free or low-halogen fluxes. In addition to detecting ionic halogens in fluxes, you should also detect the total halogens including covalent halogens, or check the use of the board. surface halide ions.

(4) Correct use of cleaning solvents. If rosin-based flux is used, it will not be corrosive because the halogen-containing active substance is surrounded by rosin resin. However, if an improper cleaning solvent is used, it can only clean the rosin and cannot remove the halogen-containing ions, which will accelerate corrosion. It is generally recommended to use a compatible cleaning agent containing both polar solvents and non-polar or low polarity, that is, it has a good effect of removing ionic and non-ionic residues (such as resin).