High impedance design and investigation using TDR for fine lines on high density organic substrate

This paper presents the electrical characterization for fine lines on organic substrate using TDR. Micro-strip line (MSL) and grounded coplanar waveguide (GCPW) two structures are studied and fabricated. Impedance between 1GHz and lossless is about 10 ohms gap for both structures. This changes the impedance matching design concept because conduction loss of fine lines can't be ignored as conventional substrate. Also from TDR result, no flat area can be seen to identify the impedance of the trace. As a result, S-parameter is then analyzed and different spaces are compared. From the result, standing wave is seen in MSL but not in GCPW because the reflection wave of GCPW is attenuated by higher copper loss. Moreover, higher impedance with larger space results in better performance due to proximity effect.