Hello Roger,

Hitachi is a licensee of the Tessera microBGA (tm) package and is developing
their capability for volume manufacture at this time. One unique ability of
the Tessera technology is to decouple the mismatch in coeffiecients of
thermal exapansion between the silicon and the FR-4 by means of a patented
compliant interposer. Recently completed finite element modelling performed
by Tessera shows a near 20x reduction in stress in the solder ball joints
using this technology. Should you desire more information please feel free to
contact me and I will provide you with contacts in Japan working the project.

Regards,
J. Fjelstad