Characterization of molding compound material and dielectric layer of RDL

Fan Out-Wafer Level Packaging (FO-WLP) is good platform for system-in-package (SIP) application in high frequencies due to its relative good electrical performance. In this paper, the molding compound material is characterized using microstrip ring resonators, which are fabricated and measured to obtain the relative dielectric constant (Er) and loss tangent (tan delta) from 24 to 36 GHz. The loss tangent is determined with conductor loss, dielectric loss and radiation loss of ring resonator taken into consideration. Through-reflect-line (TRL) calibration method is used to eliminate the testing pad parasitic effect and impedance mismatch. In addition, the dielectric layer of redistribution layers (RDL) is characterized with thin film capacitors. It is shown that both molding compound and RDL can be used in system-in-package 5G communication.