A system-in-a-package or system in package (SiP), also known as a Chip Stack MCM, is a number of integrated circuits enclosed in a single package or module. The SiP performs all or most of the functions of an electronic system, and are typically used inside a mobile phone, digital music player, etc. Dies containing integrated circuits, may be stacked vertically on a substrate. They are internally connected by fine wires that are bonded to the package. Alternatively, with a flip chip technology, solder bumps are used to join stacked chips together.
SiP dies are stacked vertically, unlike slightly less dense multi-chip modules, which place dies horizontally alongside one another. SiP connects the dies with standard off-chip wire bonds or solder bumps, unlike slightly denser three-dimensional integrated circuits which connect stacked silicon dies with conductors running through the die.
An example SiP can contain several chips—such as a specialized processor, DRAM, flash memory—combined with passive components—resistors and capacitors—all mounted on the same substrate. This means that a complete functional unit can be built in a multi-chip package, so that few external components need to be added to make it work. This is particularly valuable in space constrained environments like MP3 players and mobile phones as it reduces the complexity of the printed circuit board and overall design. Despite its benefits, this technique decreases the yield of fabrication since any defective chip in the package will result in a non-functional packaged integrated circuit, even if all other modules in that same package are functional.