Ultra wide bandwidth performance of high-density wiring interposer for 3D packaging

We have demonstrated a high-density wiring interposer for 10 GHz 3D packaging using a photosensitive multiblock copolymerized polyimide. This new polyimide can realize micron-sized fine patterns without the pattern shrinkage because of not requiring high-temperature thermal curing. The polyimide has good electric properties such as high breakdown voltage and low dielectric constant. Therefore, it is considered that by introducing this photosensitive polyimide as an insulator of the interposer, a high-performance interposer for LSI packaging can be realized. We confirmed experimentally that the high-density wiring interposer could be fabricated using the polyimide and the gold metal. From time domain reflectometry (TDR) measurement by using a specially prepared 20-μm-pitch microwave contact probe, it was found that the characteristic impedance of the stripline is within 55.2 Ω±11.5 % at the central 10-mm-square area of the interposer.