Hello Alain,

MicroBGA and uBGA
are actually registered trademarks of Tessera.

The generic term many folks use is "Area Array CSP"

There are several definitions floating about

The original definition was:

A packaged IC with a footprint not greater than 1.2x the size of the die

To that have been added...

A packaged IC chip not greater than 1.5 X the volume of the die

A minimally packaged IC chip with a lead pitch of 1.0mm and a size not greater than the die by 1.0mm on each edge

A minimally packaged IC

IPC/ ANSI J-STD- 012 “Implementation of Flip Chip and Chip Scale Technology”
is a good general reference.

Hope this helps.

Kind regards,
Joe