SMT Magazine

SMT-Apr2017

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48 SMT Magazine • April 2017 by Venesia Hurtubise, Elizabeth Norwood, Wells Cunningham, and Laura LaPlante MICROCARE CORP. Abstract Advancements in the electronics industry are continuously leading to more sophisticated, more intricate and more miniaturized circuitry. In conjunction with increasing regulations on electronics manufacturing, many changes have been made to the electronics world, and thus the circuit board manufacturing process. Lead- free, no-clean and halide-free flux formulations have introduced new cleaning obstacles, espe- cially on ever-shrinking component sizes. In or- der to maintain high cleanliness standards for modern circuitry, new sophisticated cleaning chemistries are required. The purpose of this paper is to present a cleaning process for difficult no-clean, lead-free and high temperature flux residues on reflowed PCBs. The proposed cleaning solvents are drop- in replacements for outdated solvent technolo- gy, or alternatives for elaborate aqueous systems. These cleaning technologies are used in tradi- tional vapor degreaser systems, which allow for fast cleaning times and spot-free results without the need for additional rinsing or drying equip- ment. The improved formulas have low surface tensions (less than 20 dynes/cm), which allow access to low stand-off components and high solvency to combat the most difficult flux for- mulations and white residues. Visual and quan- titative data are presented to assess the overall cleaning efficiency of the solvent system. Cost analysis is investigated to assess the efficacy of solvent vapor cleaning for PCB industry. INTRODUCTION Background The beginning of the electronics manufactur- ing industry was, for lack of a better word, messy. Circuit boards were slathered with thick layers of fluxes, primarily foam flux agents, which would coat the entire underside of a circuit board. Aside from the inefficiency and visual untidiness, ex- cessive flux can also lead to electro-chemical mi- gration within the circuit and cause uninten- tional failures during use. Figure 1 shows an ex- ample of dendritic growth between two con- tacts. This migration can occur due to changes VAPOR DEGREASING CHEMISTRIES to Remove Difficult Lead-Free and No-Clean Fluxes from PCBs FEATURE

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