D2CSP (double density CSP): a new solution for high-density packaging

LG Semicon has developed the D2CSP, a stack package for 128 Mb SDRAM with two 64 Mb SDRAMs. LG Semicon´s unique lead frame type CSP, the BLP package was the starting point for D2CSP. Thanks to the flat bottom of the BLP package design, a high reliability and low-cost stack process is made available. Employing the stencil printing process, a process with a well-established infrastructure for stacking, D2CSP can overcome the limitations of the stack packaging technology, such as known good die, manufacturability for mass production, testability, and rework. In addition, the D2CSP is more preferable in that the on-board reliability has been enhanced by adopting compliant leads. Such features of the D2CSP can be utilized by high-end systems, e.g. servers and work stations. Finally, the concept of the D2CSP is so flexible that a much higher density module with low cost is feasible