Signal integrity and reliability of a new Multi-Stack Package using a Pressure Conductive Rubber

A proposed Pressure Conductive Rubber (PCR) is used instead of conventional interconnections such as wire and solder bondings for a Multi-Stack Package (MSP). A PCR for a three-dimensional (3-D) high-density interconnection has a major advantage in that it can replace defective dies with known good dies (KGD). In the structure of the PCR in this study working through external pressure, conductive particles are arranged between insulating rubber. To compare the RF electrical performance of the PCR and the solder interconnection, a test-jig with coplanar waveguide (CPW) was assembled. S-parameters and reliability tests of MSP formations using the PCR and solder interconnection were separately measured in a frequency range from 300 KHz to 8 GHz. The measured results show the insertion loss of 1.72 dB and the return loss of 12.7 dB on a single-layer structure at 8 GHz. Additionally, reliability tests of the PCR show stable electrical performance. These results indicate that the RF electrical performance of the PCR is acceptable for use in DDR3 SDRAM (Double Data Rate 3 Synchronous Dynamic Random Access Memory) applications.