AIN LGAs for High Performance Packaging Applications

Because they offer many properties favourable for IC package construction, ceramics have been in widespread use as an electronic package material since the early 1960s. In recent years, with trends towards higher speed semiconductors generating up to 30‐40 watts power, packaging materials must possess excellent thermal, electrical and mechanical properties. Aluminium nitride, with a thermal conductivity of 170 W/m.K., high fracture strength and a thermal coefficient of expansion match with silicon, has been used to manufacture multilayer LGA (land grid array)packages for high performance applications. A 725 AIN LGA has been manufactured and its performance characteristics have been compared with those of an alumina(with copper/tungsten slug) packaging alternative. Because of the high thermal conductivity of aluminium nitride, all designs can be made in a cavity‐up configuration, resulting in significant package body size reduction. The area under the cavity can be used for increasing I/O number and a ground plane can be inserted under the cavity,reducing simultaneous switching noise. Aluminium nitride is particularly beneficial for flip‐chip interconnection. Its close TCE match to silicon eliminates the stress reduction requirement for die underfill.