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This paper outlines the composition of water soluble fluxes for the electronics industry and their methods of use when wave soldering and reflowing tinned coatings and solder pastes. Process optimisation is facilitated by the Taguchi method. Three types of cleaning machinery are evoked, with varying results. It is shown that the energy/time relationship is important to ensure adequate cleaning quality. A number of fallacious arguments are debunked. Methods of water purification and the problems of effluent treatment for all sizes of installation are addressed. Doubt is expressed as to the viability of closed‐circuit water recycling except for the largest installations or where exceptional conditions prevail. It is shown that water soluble fluxes and their subsequent aqueous removal are unlikely to make any significant contribution to the Greenhouse Effect. The overall cost of their use is substantially similar to that of rosin fluxes with CFC‐113 azeotropes at 1986 prices. Cleanliness control under production and laboratory conditions is discussed with reference to both ionic contamination testing, including its use for SMDs, and SIR analysis, especially at low voltages, including non‐destructive production SIR testing. Reliability of the assembled circuits is shown to be at least as good as that with more traditional soldering and cleaning methods, frequently better, and this is the case even for military and aerospace applications. The paper concludes that, now that quality water soluble solder pastes are available, this method is most likely to become the workhorse for the majority of electronics applications.

This paper discusses the requirements of quality assurance of electronics assemblies with respect to the surface conditions, and more particularly the problems introduced by modern assembly techniques. Ionic contamination testing and surface insulation resistance measurement are dealt with as complementary techniques. Particular emphasis is laid on the fact that standards related to both QC methods are inadequate and do not reflect modern needs. Cleaning, as a corollary to contamination, is touched upon without detail, other than a table comparing methods as a function of purchasing and operating costs, technical performance, etc.

This paper essentially describes what is believed will become the norm in contamination control over the next decade, as applied to laminate and PC manufacture, components, assembly, soldering and protection. Particular attention is paid to the special requirements imposed by the increasing use of surface mount technology, especially when trying to extrapolate current techniques towards modern applications. Test methods are mentioned and these are also likely to undergo considerable development over the next few years but, above all, more precise, scientifically‐established standards are urgently needed for both ionic contamination and surface insulation resistance testing. Cleaning technology is, of course, an essential part of contamination control and future development of both solvent and aqueous methods will lie in a better understanding of the time‐energy relationship required to break contamination‐substrate bonds at a molecular level.

In view of the uncertainty of the applicability of traditional ionic contamination measurement to surface mount assemblies, a mathematical study was made of the phenomena involved. A model was derived, showing that under‐component contamination behaves differently from ordinary surface contamination. By breaking down a curve obtained under practical conditions into its components, it is therefore possible to derive separate figures for surface and under‐component ionic contamination, ignoring the influence of spurious noise signals. A new software, using these techniques, has been written for this application. Comparative tests between non‐destructive testing, using this software, and tests on similar circuits with the components torn off, show that there is a close correlation between the results from these two techniques, even though the under‐component contamination is only partially dissolved with the former method.