A stackable ball grid array (BGA) or fine ball grid array (FBGA) semiconductor package particularly suitable for board-on-chip or chip-on-board applications in which a low profile BGA or FBGA semiconductor package is needed....http://www.google.com.au/patents/US6740984?utm_source=gb-gplus-sharePatent US6740984 - Ball grid array chip packages having improved testing and stacking characteristics
