Testing and qualification of HFE cleaning agents in vapor degreasing applications

There is no satisfactory replacement for vapor degreasing in many metal and, precision parts manufacturing and cleaning tasks, including a variety of electronics printed wiring assembly, printed wiring board and component applications. This paper describes a new, environmentally friendly: second-generation vapor degreasing process that uses a hydrofluoroether (HFE). The new process can permanently replace both 1,1,1-trichloroethane and CFC-113 in a wide variety of cleaning applications vital to the industry, as well as chlorinated solvents such as methylene chloride, trichloroethylene (TCE), perchloroethylene and HCFC-141b. Importantly, this new fluorochemical-based process operates very satisfactorily in unmodified, modern vapor degreasing equipment, or in slightly modified older but well-maintained equipment. Thus, this alternative may offer the possibility of an eleventh-hour rescue for many organizations that delayed converting or couldn't afford the equipment necessary to use other alternatives to ozone-depleting solvents. It also is extremely attractive for those whose first alternative choice has not fully met their expectations, or whose circumstances, designs and requirements have changed. From the equipment operator's perspective, HFE processes are run identically to a conventional vapor degreasing process in which the parts are immersed in the boil sump, rinsed in the next sump and then quickly dried in the vapor. HFE process results to date can be summarized as follows: HFE processes have been satisfactorily implemented in several completely unmodified pieces of conventional vapor degreasing equipment. HFE cleaned routine production parts at least as well as HCFC-141b, TCE or aqueous cleaning does in current operations. No compatibility problems were encountered with the HFE process. HFE process cycle times were equal to or less than those used in production with HCFC-141b or TCE, and far shorter than those for aqueous cleaning. HFE solvent emissions were much lower than those from HCFC-141b or TCE. Preliminary economic analysis suggests that cleaning costs for the new process are competitive with or lower than those of other cleaning processes. These conditions are thought to be typical of other, similar manufacturing operations.