Package on package

Package on package (PoP) is an integrated circuit packaging method to combine vertically discrete logic and memory ball grid array (BGA) packages. Two or more packages are installed atop each other, i.e. stacked, with a standard interface to route signals between them. This allows higher component density in devices, such as mobile phones, personal digital assistants (PDA), and digital cameras.

Two widely used configurations exist for PoP:

During PCB Assembly, the bottom package of a PoP stack is placed directly on the PCB, and the other package(s) of the stack are stacked on top. The packages of a PoP stack become attached to each other (and to the PCB) during reflow soldering.

The package on package technique tries to combine the benefits of traditional packaging with the benefits of die-stacking techniques, while avoiding their drawbacks.

Traditional packaging places each die in its own package, a package designed for normal PCB assembly techniques that place each package directly on the PCB side-by-side. The 3D Die-Stacking system in package techniques stacks multiple die in a single package, which has several advantages and also some disadvantages compared to traditional PCB assembly.

In embedded PoP techniques, chips are embedded in a substrate on the bottom of the package. This PoP technology enables smaller packages with shorter electrical connections and is supported by companies such as Advanced Semiconductor Engineering (ASE).

The most obvious benefit is motherboard space savings. PoP uses much less PCB area, almost as little as stacked-die packages.

Electrically, PoP offers benefits by minimizing track length between different interoperating parts, such as a controller and memory. This yields better electrical performance of devices, since shorter routing of interconnections between circuits yields faster signal propagation and reduced noise and cross-talk.

There are several key differences between stacked-die and stacked-package products.

The main financial benefit of package on package is that the memory device is decoupled from the logic device. Thus: This gives PoP all the same advantages that traditional packaging has over stacked-die products:

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Wikipedia