James J. Casto

Molded carrier rings for fine pitch surface mount packages

A molded carrier ring concept intended to reduce the incidence of bent leads and coplanarity rejects while providing increased output-to-mix potential and easy standardization for customers and equipment manufacturers is presented. The methodologies used to design a family of molded carrier rings around various quad-flat-pack and plastic quad-flat-pack package types are described. The algorithms and assumptions used to optimize the ring size and shape are discussed. Test contact design and performance, electrical characteristics, and thermal/mechanical modeling are also discussed.<<ETX>>

Low profile plastic quad flat package: LPPQFP

The effects of stress on the mechanical integrity of the high pin-count surface-mount PQFP packages and on very large (500 mil) IC dies have been studied experimentally. Passivation cracks, metal movement, and crack propagation in the package are examined. Changes in package design that improve the resistance to thermal excursions of surface-mounted devices are described. A factorial experiment is reviewed that used package thickness, lead-frame materials, and adhesion promoters as the variables. The latest ultra-low-stress molding compounds and passivations were studied. The affect of adding stress buffers to mold compounds, particularly crack passivation, is emphasized. Also included are experimental data using a package-development test die to electrically characterize the effects of the various package design and material changes as well as the system performance during various stress tests such as temperature cycle, thermal shock, moisture preconditioning/crack resistance and moisture resistance.<<ETX>>