Controlling emissions stemming from the hot air solder leveling process

Abstract

The oil, flux, and solder added to a hot air solder leveling tool creates an emission of oil mist, acidic gases, and solid metal compounds. The oil tends to form into very fine droplets, resulting in exhaust opacity. Diffusion type fiber bed filters are the optimal choice for the removal of oil mist. For optimal filter efficiency the exhaust stream should be cooled. A wet scrubber upstream of the filter will cool the exhaust stream through water evaporation. Additionally, the scrubber will remove acid vapor and coarse solids from the exhaust. The characteristic quality of a coalescing fiber bed filter is its ability to continuously drain liquid. The defining parameter in the service life of a fiber bed filter is the solids in the exhaust stream. These solids can lodge in the fibers and block a portion of the void area, and hence increase the filter pressure drop. In an attempt to extend filter life, a study was conducted for the use of detergents to clean the filter. These studies show that a detergent can extend filter life in the H.A.S.L. application by removing a blocking agent from the filter. Further tests are planned at additional locations to examine the performance at sites that use other ingredient formulations in the flux, oil, and solder.