Characterisation of mechanical properties of metal-coated polymer spheres for anisotropic conductive adhesive

Packaging and interconnection of integrated circuits have been a steadily increasing bottleneck, as the pattern dimensions on the silicon die continues to shrinks much more rapidly than the pattern on a typical printed circuit board. The search for more dense as well as cheaper interconnect, without compromise the reliability, is therefore of high priority. A program to characterise the mechanical properties of metal-coated plastic spheres has been going on at Chalmers, sponsored by Dyno Specialty Polymers AS as well as Hitachi Chemical. Mechanical properties have been obtained by measuring the stress-strain relationship for a number of different particles, both made by Dyno Specialty Polymers as well as other vendors. The properties have been tested both at room-temperature as well as 150/spl deg/C, to see the effect of elevated temperature. The results show clearly that the deformation of particles shows a significant hysteresis behaviour.