As DRAM chips packaged in a higher performance BGA package started to be introduced, STEC developed a new type of BGA stacking that could meet the needs of DDR2 and other higher speed chips. The design challenges required developing a technology that could meet the increased thermal, power delivery, signal integrity, and mechanical strength needs of BGA stacks while still maintaining a highly manufacturable solution that could be built on a just-in-time basis in STEC's own manufacturing facilities.

The solution consists of mounting two BGA packaged DRAMs onto a stack board and connecting this to the main DIMM board using a special frame board. The frame board uses a special connection technique called castellated vias to provide a very strong and reliability connection to the main DIMM board.