Water Soluble Fluxes for PCB Soldering and Contamination Control

After an introduction briefly describing the historical background of flux selection for soldering in the electronics industry, a logical development is presented showing that water soluble fluxes offer many advantages not available with the more traditional resin types. Brief details of water soluble fluxes are presented with the emphasis on their practical use, including cleaning methods and equipment. Emphasis is placed on the use of proprietary neutralisers. The second half of the paper is devoted to the cleanliness testing after flux removal, and a description of a new measuring instrument is given. Cleanliness standards, backed by practical experience, are stated, with figures replaced by an arbitrary scale to emphasise the variability of the results according to the nature of the contamination. It is recommended that routine contamination control be carried out in all plants where quality of the finished product is a preoccupation. The combination of the use of water soluble fluxes with contamination control gives by far the most efficient, reliable and cost‐effective soldering possible with today's technology, and this will be used increasingly over the next decade.