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52 SMT Magazine • April 2014 SummarY: as the proliferation of modern-day elec- tronics continues to drive miniaturization and func- tionality, electronic designers and assemblers face the issue of environmental exposure and uncom- mon applications never previously contemplated. This reality, coupled with the goal of reduc- ing the environmental and health implications of the production and disposal of these devices, has forced manufacturers to reconsider the ma- terials used in production. Furthermore, the need to increase package density and reduce costs has led to the rapid de- ployment of leadless packages such as the QFN, POP, LGA, and micro-BGA. In many cases, the manufacturers of these devices will recommend the use of no-clean fluxes due to concerns over the ability to consistently remove flux residues from under and around these devices. These concerns, along with the need to im- plement a tin whisker mitigation strategy and/ or increase environmental tolerance, have led to the conundrum of applying conformal coat- ing over no-clean residues. The AIM R&D team has united with OEM electronics and conformal coating manufac- turers in an attempt to characterize the differ- ent coating technologies currently available. In this study, various coating materials were tested with different chemistries of no-clean fluxes. Results demonstrate possible combinations meeting the mission profile of the assembly with consideration for the assemblers' capabili- ties and cost objectives. Conformal coating of PCBs has garnered se- rious attention in all phases of PCB design and manufacturing. Manufacturers and engineers industry-wide are exploring the capabilities, costs, and limitations of this technique. The driving factor is the deployment of electronics into more diverse and harsh environments as demand for functionality and interoperability fEATurE by Karl Seelig and Timothy O'Neill AIM Conformal Coating over No-Clean Flux

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