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What is PoP Memory?

December 19, 2009

Package-on-Package or (PoP) memory was created as a way to reduce the physical size of the memory sub-system on a single board computer. The basic idea is to stack two BGA devices one on top of the other as shown above.

PoP Memory has Several Advantages Including:

  • More reliable manufacture because the memory sub-system can be assembled separately from the final system.
  • Higher memory cycle speeds due to shorter connection lengths.
  • Small size

This type of memory is used in handsets and other types of portable devices and is also making it’s way into mid-level products as well.

Disadvantages Include:

BGA assemble issues, can only re-ball the part a limited number of times then it must be scrapped. So, for example, if the RAM portion fails, the FLASH could be de-soldered and re-soldered to a working RAM module, but only a limited number of times.

Test issues – BGA packages do not allow access to device pins once the device is soldered down. In the case of a PoP module, since the top module is soldered to the bottom, there is no way to access the pins. Typically JTAG boundary-Scan tools can be used to test in this configuration.

Examples of Boards with PoP Memory:

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