It is well known that residues on printed board assemblies can lead to serious reliability problems. Over the past several years, the migration from the use of lead-bearing materials to lead-free materials has resulted in many changes in electronics manufacturing operations.
Some of the residual materials that remain on the circuit card assembly are becoming increasingly more problematic to clean. Component densities and component under-clearances are creating new cleaning challenges. To help the process engineering community deal with these difficulties, IPC has released the B revision of IPC-CH-65 ‘Guidelines for Cleaning of Printed Boards & Assemblies’.
With guidance from industry experts, the cleaning guidelines have been completely rewritten and address all facets of cleaning, including material selection, process considerations, equipment selection as well as the environmental impact of cleaning. The 200-page document not only brings cleaning requirements up to date, it also combines multiple documents into a single, comprehensive guideline. IPC-CH-65B explains the interactions between materials and processes and outlines the sources and types of contamination found on today’s circuit card assemblies.
The cleaning of printed boards and assemblies has undergone a significant transformation in two decades, due in large part to environmental regulations which are cross-referenced in the document. No-clean fluxes and lead-free solder are among the technical mainstays. “Years ago a large portion of the electronics industry moved from solvent-based cleaning to water-based cleaning. Over the past few years we have seen another shift to the use of lead-free materials and processes. The combination of these events led to the development of the new guideline,” explains Dave Torp, vice president of standards and technology at IPC. He adds that, with the shift to lead-free solder, “reflow temperatures increased, which has impacted the character of residues that remain on the assemblies.”
For more information contact Nkoka Training, +27 (0)12 653 2629, [email protected], www.nkoka.co.za
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