Low Transmission Loss Film Material for High-Speed High-Frequency Devices

The demand for low transmission loss materials applicable for printed circuit boards (PCBs) used in high-speed high-frequency devices has been increasing. Transmission loss consists of dielectric loss and conductor loss, and the reduction of both losses is necessary to achieve the demand of PCB materials. From our simulation results, the higher the frequency, the higher the ratio of dielectric loss in transmission loss. The impact of dielectric loss increases in higher frequency. Under such a situation, we developed the new thermosetting resin with low dielectric constant (Dk of 2.4 at 10 GHz), dissipation factor (Df of 0.0016 at 10 GHz) resin. Then we developed the new low loss film by applying this new resin to smooth surface roughness copper foil. Transmission loss of the new low loss film (-0.58 dB/cm at 76 GHz) is 23 % lower than the current Ultra-Low-Loss (ULL) grade material (-0.75 dB/cm at 76 GHz). This material has good processability which can make laser IVH and electroplating without special treatment such as plasma desmear. The connection resistance value of laser IVH did not decrease after 3,000 cycles of thermal test at 65 °C (15 min) ? 125 °C (15 min). The insulation reliability is also good with no insulation deterioration after thermal test of 2000 h at 85 oC /85 %RH. In addition, this material is applicable for multi-layer construction without other adhesive sheets. Therefore, we can propose new PCBs design as multi-layer antenna for ultra-wide band, contributing to increase the latitude of the design of PCBs.