Umut Tosun, Jigar Patel, Kalyan Nukula, Fernando Gazcon
Manassas, VA USA
With regard to precision cleaning applications within electronics manufacturing, pH neutral product development was a major breakthrough in recent years. The impetus for this development resulted from changes with regard to solder paste formulations and resulting assembly processes.
The greater use of lead-free solder paste and the required higher reflow profiles have resulted in even more difficult to remove burnt-in flux residues. Coupled with increases in component density, larger component packages, higher lead counts, finer lead spacing, and lower standoff distances, effective cleaning is greatly challenged. The aqueous alkaline based cleaning agents can effectively remove these flux residues, however, the process often requires an increase in wash temperature and exposure time, chemical concentration, and mechanical energy. Although an efficient and effective cleaning process can be developed, oftentimes, the required operating parameters present a new set of challenges with regard to material compatibility.
Since their introduction, the newly developed pH neutral formulations have proven to be capable not only of removing these difficult post reflow residues from complex board geometries, but do so without affecting material compatibility of sensitive components. Additionally, they perform at low concentration levels. This study reviews the performance of pH neutral cleaning agents as compared to alkaline cleaning agent alternatives and includes field data demonstrating their effectiveness with regard to material compatibility and cleaning performance.
As reviewed in the background and introduction of this study, pH neutral cleaning agents held the promise of offering superior material compatibility and excellent cleaning results as compared to the inhibited alkaline cleaning agents currently available for various paste and flux residues. In this study, three case studies were presented, each with a different paste/flux vehicle and material compatibility constraints whereby a pH neutral process cleaning solution was identified.
In summary, pH neutral cleaning agents can in fact meet the stringent cleaning requirements expected, even with burnt-in flux residues from multiple heat cycles, while exhibiting excellent material compatibility and with lower wash concentrations as compared to alkaline alternatives. Additionally, it is environmentally friendly eliminating the need for waste water neutralization.
Initially Published in the IPC Proceedings