Life Cycle Impact Assessment of Lead-free Solder Considering the Trade-off Relationship between Toxic Impact and Other Impact Categories

摘要

Lead-free solder is a focus of increasing international attention, particularly in the wake of various EU directives (ROHS: on the restriction of the use of certain hazardous substances in electrical and electronic equipment). Lead-free solder is anticipated to reduce toxic environmental impact, but it has been pointed out that energy consumption and other related impacts like global warming caused by the production of lead-free solder may be higher than those for conventional solder. It is necessary to consider this trade-off relationship between types of environmental impact. The aim of this study is to conduct trial calculations of impact assessments of typical lead-free solders and a conventional Sn-Pb solder. Impact categories at the local level are regarded as important in the assessment of current materials, such as impacts caused by exposure to hazardous substances. For these impact categories, the resultant environmental impacts can differ greatly, depending on where emissions occur, even for the same degree of environmental burden. Therefore, LIME (Life cycle Impact assessment Method based on Endpoint modeling) was preferentially used, based on domestic background data. Using a conceptualized damage assessment and damage indicator of human health, we concluded that the avoidance of lead is effective even when the increase in other health impacts are taken into account. The reliability of this result was confirmed by the implementation of an uncertainty analysis.