Cleaning No-Clean Flux and Related Reliability Issues
Author: Eric Camden Company: Foresite, Inc. Date Published: 10/14/2012
Abstract: There is a well-known problem in the electronics industry with no-clean flux residues, and the after-effects they can have on reliability are significant. If fluxes are not fully complexed after reflow, or completely removed after the wash process, a number of failure mechanisms directly attributed to the flux can occur. There is a tendency for the no-clean flux to become entrapped under low standoff parts and parts with very tight spacing such as BGA’s, QFN’s and other similar type components. This paper will explore the potential issues associated with no-clean flux residues including partially activated flux residues, localized cleaning that has created a trapped surface residue and other unseen issues. We will then look at the specific types of failure modes directly related to improperly processed flux residues. Lastly, proven cleaning methods for no-clean flux will be discussed with a focus on both cleaning at the time of original manufacturing as well as recovery cleaning for hardware that was improperly processed during the original build.