Package -on- Package ( PoP, Eng. , Literally translated as " housing to the casing") is in the construction and connection technology of microelectronics fabrication technique in which two or more specially prepared chip package, usually these are ball grid array (BGA ), are one above the other assembled and soldered in these stacked arrangements of the printed circuit board. This design allows a higher integration density as the arrangement of the individual BGA package on the PCB next to each other and is preferably used in smartphones, digital cameras and tablet computers. PoP was developed in 2007 at the company Maxim Integrated Products and the body style is defined in JEDEC standards.
With package-on - package with two single enclosures the lower BGA must have connecting pins on both sides. Go down to the motherboard, as with all BGA Balls (English for " solder balls " ) are soldered, up to the upper BGA package are appropriate solder pads for receiving the connector pins from the upper BGA package. The two BGA packages are manufactured separately and superimposed fitted immediately before the reflow soldering process using automated insertion on the PCB. Since, in the soldering process, the heat generated by the top BGA chip must pass through to the lower BGA chip to securely solder the underlying BGA connector pins to the main printed circuit board, on the other hand, no damage due to an over-temperature may occur in the semiconductor chip, are necessary for the soldering process according to accurate and balanced temperature profiles.
PoP is usually used in two areas:
- If two or more memory chips. Typically, this highly integrated DDR SDRAM memory. Applications lie in compact memory cards or memory modules.
- The combination of a main processor (CPU ) in the lower chip and the overlying for the system -on-a - chip (SoC ) required main memory, usually implemented as DDR SDRAM. Applications of this combination are in mobile computing systems and shown schematically in the following section illustration.
Package -on- Package must be distinguished from the so-called stacked die package in which two or more this, these are the unpackaged semiconductor chips are housed in a chip package and act as a single chip to the outside. Stacked die -Packed find any of these flash memory application to increase the storage capacity per chip package can.
An advantage of package-on - package with respect to stacked die package is that the individual chips can be separately tested prior to assembly. Furthermore, establishing a specific chip combination is, in principle, until shortly before the soldering process possible. So in package-on - package, the memory chip overhead can be varied before the soldering process in memory size. Another advantage of the PoP is in short conductive paths between the two chips. So that memory and the connection between the two chips with high clock frequencies may be used.
A disadvantage of the PoP comparatively poor ability to be able to dissipate waste heat to the environment during operation by means of cooling the body. In particular, the lower chip can dissipate its heat badly. Therefore PoP is primarily limited to applications where only a small power loss occurs and a comparatively low power consumption is present. This is typically the case of mobile electronic devices such as smartphones and tablet computers.