A packaged semiconductor device has bottom surface leads having portions of the package adjacent the lead edges excised. The outer leads may take the form of inverted-J leads, short stub leads, vertically bent leads-in-grooves, or may be entirely eliminated. Lead connections are on the bottom package...http://www.google.ca/patents/US6265660?utm_source=gb-gplus-sharePatent US6265660 - Package stack via bottom leaded plastic (BLP) packaging
