Cleaning Guidelines
The use of more aggressive solder flux, coupled with the higher soldering temperatures, results in making the cleaning process more difficult. The difficulty in removing Lead Free soldering residues is dependent upon:
- Alloy selection
- Peak soldering temperatures reached
- Exposure time at the peak soldering temperature
- Type of flux and flux residues
- Soldering atmosphere
For example, a Tin Lead (SnPb) cleaning process, which utilized only DI water to clean the hardware, may require semi-aqueous or aqueous cleaning materials, to remove residues which could not be removed with only DI water.
When using Lead Free solders, with Water Soluble Fluxes, DI water may not be sufficient to remove residues. The user may be forces to use a cleaning solution – a mild saponifier or surfactant - to completely remove solder residues.
For high reliability applications, RMA and RA Fluxes are still being used. This is especially found in the military and aerospace electronics manufacturing community. Therefore, these fluxes will be more difficult to clean due to higher soldering temperatures. To counter this, the cleaning agents used – a saponifier or surfactant – may have to used at a higher concentration levels and / or higher temperatures. This will be dependent on the cleaning agent used.
No Clean / Low Residue Fluxes will be the most difficult to remove. This makes sense since these residues were not designed to be removed. While these fluxes may leave a minimum amount of flux residues on the hardware, when compared to Water Soluble and Rosin Fluxes, No Clean / Low Residue Fluxes are not as active as Water Soluble and Rosin Fluxes. Depending upon the soldering process used, these fluxes may not support Lead Free soldering as efficiently as Water Soluble and Rosin Fluxes.
