Alternate safe solvents in hybrid circuit processing

Abstract

Hybrid circuit processing utilizes a number of types of materials in process and in end product manufacture. Our focus of concern is with the in-process materials. Here, we consider the fluxes used in soldering, solder paste, and adhesives and conductive epoxies. Defluxing remains an important aspect even when considering the usage of no-clean and water soluble flux. In most cases, flux removal is required to produce a trouble-free circuit and may also be required for aesthetics. Complete removal of flux remains the goal. Paste clean-up includes thick film and solder pastes. As fine lines and accurate paste deposition are mandated, complete paste removal from screens and stencils becomes critical where paste residues reduce print definition. Practice has produced a wide range of solvent chemicals for this cleaning process. This has been done without suppliers' specific recommendation or support, since the bulk of these chemicals are commodity materials. In this paper, it is shown that many of these chemicals are toxic and/or health hazards. The objective here is to offer specific types of chemical solvents for the application that also provide an improvement upon and an alternative to the hazardous materials.