June 24, 2011 - Elpida Memory has come up with what it says is the thinnest available DRAM device, a new 0.8mm four-layer package of 2GB DDR2 mobile RAM chips, assembled using package-on-package. The four-layer PoP DRAM combines Elpida's small Mobile RAM technology with Akita Elpida's thin-chip processing and molding technology. Volume production ramp is slated for 3Q11.
Customers had been opting for two-layer 0.8mm packages, rather than the thicker 1.0mm four-layer PoP, so systems that needed 8GB of DRAM needed two layers of 4GB product, noted Yoshitaka Kinoshita, Elpida COO and head of its DRAM business unit, in a statement. Now they have more choices with four layers of 2GB in one package; yields and cost are the same as for existing 1.0mm products, he adds. (Next step is to upgrade the layers to 4GB in the same four-layer 0.8mm size.)
Advantages of PoP, particularly for mobile devices: mounting space is reduced, individual packages can be tested, there's less wire used (minimizes reflection and noise), and density can be more easily increased.
PoP package cross-section. (Source: Elpida)