Signal transmission loss due to copper surface roughness in high-frequency region

Higher-speed signal transmission is increasingly required on a printed circuit board to handle massive data in electronic systems. So, signal transmission loss of copper wiring on a printed circuit board has been studied. First, total signal loss was divided into dielectric loss and conductor loss quantitatively based on electromagnetic theory. In particular, the scattering loss due to surface roughness of copper foil has been examined in detail. And the usefulness of the copper foil with low surface roughness has been demonstrated. Introduction Higher performance IT electronic systems are strongly required to handle huge amount of data in a shorter time in recent years. Transmission speed of the signals propagating inside the equipment has been increasing. Signal loss becomes remarkable on a printed circuit board in the GHz frequency range. It causes many problems, such as rising edge degradation of signals, or resulting higher bit error rate, and so on. Then, reducing the signal loss on a printed circuit board has become more important. Therefore, in this study, measurement of S21 has been carried out by fabricating various evaluation boards combining different copper foils with low roughness and low dielectric materials. And they were compared with the transmission loss of the commonly used material, FR-4. In particular, the reduction effect of signal loss has been demonstrated quantitatively by using copper foil with smooth surface roughness along with low dielectric loss material. Signal transmission loss Signal transmission loss on printed circuit boards can be classified into conductor loss due to the conductor and dielectric loss due to the dielectric. Then, total signal transmission loss can be expressed by two loss factors.