Solder Preforms: Increasing Automated Placement Efficiency

摘要

Solder preforms are precise shapes of metal, produced by the high-speed stamping or forming of solder wire or ribbon.rnPreforms provide a highly repeatable volume of solder, with 100% metal content by volume. They are commonly used inrnconjunction with solder paste to incrementally increase the volume of solder joints, which increases reliability in connectionsrnsubject to mechanical fatigue, and increases signal-to-noise ratios in interconnections delivering high frequency signals.rnDozens of OEM and contract assembly houses have realized that the use of solder preforms can solve issues related torninadequate solder volume in SMT processes. As with the adaptation of any new technology, issues arise and are resolved asrnthe technology evolves into mainstream, high-volume production. Over the past two years of process evolution, the mostrncommon issues related to the implementation of perform assembly have been associated with high speed placement.rnAlthough the preforms are placed in a similar fashion to chip components, they have suffered higher pick error rates than chiprncomponents.rnA series of studies were undertaken to understand the factors that influence pick error rates. This paper reviews thernexperiments that studied standard shapes, unique "super flat" geometries, component orientations, and machine feeder andrnnozzle selection. It also discusses the effect of preform shape and size tolerances, and compares the geometric specificationsrnto those of chip components.