The process challenges of lead-free wave soldering often require the use of new flux chemistries when compared with the relatively tolerant tin-lead wave soldering process. In some cases, the fluxes used in tin-lead soldering work well in lead-free assembly. In other cases, however, the complexity of the assemblies dictate more active, heat-sustainable products formulated specifically for lead-free applications. This paper reviews the J-STD-004 and how it is used in flux categorization and selection. It also discusses the major types of flux formulations available, and the design, process and reliability implications of using each type. The purpose of the paper is to help the reader make an informed choice when selecting wave solder fluxes for lead-free processing.
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