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18 The PCB Magazine • September 2014 by Joseph Fjelstad Verdant eleCtroniCs f e a t u r e Abstract Aluminum is an attractive material for use in the manufacturing of electronic assemblies, owing to its low cost, good thermal properties, dimensional stability, environmental friendli- ness and ubiquity. Unfortunately, due to its in- nate thermal spreading ability, it is not easily used when solder is required to make intercon- nections to components. This article describes ways to manufacture electronic assemblies us- ing aluminum as a base and eschewing the use of solder. Introduction RoHS restrictions on the materials used in electronics manufacture have imparted sig- nificant challenges on the electronics industry since their introduction in 2006. The greatest impacts have been felt by the mandated elimi- nation of lead from electronic solder, followed by the demand for the elimination of haloids from flame retardants used in traditional PCB laminates. Since 2006, the electronics industry has been beset with a host of new challenges in its effort to comply. Failure mechanisms, both new and old, have surfaced which demand so- lution and the industry suppliers and manufac- turing technologists have worked diligently to remedy those vexing faults through the devel- opment of a wide range of new materials and equipment for both board manufacture and assembly, along with modifications to the pro- cesses used in the manufacture and assembly of printed circuit boards. Most of the problems which have con- fronted the electronics manufacturing indus- try have related to the solder assembly process. Lead-free solders were advertised early on as a drop-in replacement for traditional tin lead sol- ders; however, field experience proved it not to be the case. The tin-rich alloys, along with the higher temperatures required for assembly, cause the industry to scramble for solutions to such problems as champagne voids, poorer wet- ting, brittle solder joints, copper dissolution, tin whiskers, head-in-pillow, greater vulnerabil- ity to damage caused by explosive outgassing of absorb moisture in packages among others

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