High Frequency Characteristics of Fine Copper Lines on High Rigidity Dielectrics

The test vehicles for high-frequency performance evaluation are successfully formed on a smooth surface prepreg by semi-additive process (SAP) assisted by ultraviolet (UV) irradiation. The designs of fine strip line are determined by simulation calculation with consideration of the process margin. The test vehicles are fabricated using substrates made of prepreg with glass cloth or insulation film without glass cloth. As a result of measuring impedance and S parameters, the sample with prepreg shows better high-frequency performance than the sample with insulation film even though they has similar dielectric constant (Dk) and dielectric loss tangent (Df) values. The reason would be the smooth interface between the signal line and the prepreg due to the SAP assisted by UV irradiation. The SAP technology assisted by UV irradiation would be a solution for high-frequency application due to the smooth surface of the package composed of prepreg.