Filler-induced failure mechanism in plastic-encapsulated microelectronic packages

Based on empirical data, the present work provides a model to prevent filler-induced reliability degradation in plastic-encapsulated LOC (lead-on-chip) packages. According to the model, the maximum size of the silica fillers included in the plastic package body should be smaller than one half of the inter-distance between the device and its overlying lead-frame. In particular, it is shown in the model that the spherical silica particles, which are sometimes trapped in the space between the top surface of the device and the bottom of the lead-frame during the encapsulating process, can induce huge compressive stress on a specific site of the integrated circuit pattern due to the thermal shrinkage of the plastic package body. Further, the present model suggests that tiny fillers squeezed beneath a large trapping filler might directly attack the brittle layer of the device pattern because the compressive force from the large filler particle can develop into huge compressive stress due to the reduced load-carrying area.