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The threat posed to the environment by CFC cleaning processes for printed circuit boards has led to an investigation of possible alternatives. In a preselection procedure, surprising results were obtained using propylene glycol ethers (PGE), solvents for the paint industry. In this study these ethers are compared with five other groups of cleaners, which can be divided into four water‐based classes: weak acid, neutral, weak and strong alkaline, and water miscible organic solvent cleaners which are non halogen‐containing and biodegradable. The cleaning power of PGE and other cleaners is tested on fluxes for wave and reflow soldering. Comparative results for the different groups are given, combined with surface insulation resistance measurements. Good results can be obtained using alkaline or solvent cleaners. However, it appears that the cleaning results depend heavily on the type of flux used and the choice of a matching cleaning process.

The demise of the CFC‐113/alcohol azeotropic solvent for de‐fluxing circuit assemblies after soldering has led, in recent years, to the electronics assembly industry being offered other cleaning technologies, some new and some new to this industry. In terms of uptake, one of the most successful will be semi‐aqueous cleaning involving the use of an organic solvent of low volatility to dissolve the contamination followed by an aqueous rinsing process. Two families of solvent have evolved based on natural products (terpenes) and synthetic hydrocarbon chemicals. This paper reviews the possible semi‐aqueous processes and the development of the solvents that has taken place. The cleaning performance is considered as well as the potential for effluent control and fully closed‐loop systems.