Novel High Reliability and Low Dk/Df Dielectric RDL Material for High Frequency 5G Applications

We believe there is a need to reduce the transmission loss in the packaging substrate of 5G mm wave terminals, including smartphones and high-performance computing (HPC) systems. Since wafer-level chip scale packaging (WLCSP) is used for packaging advanced chips, one needs to improve the dielectric properties of the materials of the package. We have developed a newly non-photosensitive dielectric material for the redistribution layer using modified poly phenylene ether. This material can be placed by spin coating, patterned by laser direct drilling, and shows a very low dielectric constant
$(\text{Dk}\leq 2.5)$
and low loss tangent
$(\text{Df}\leq 0.0025)$
. We found that low water absorption of 0.04%, ensured long-term reliability. It also offers low warpage, superior micro vias processability, and reduction of bump crack. These properties achieved here are suitable for the advanced applications that support high frequency.