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Signal Transmission Loss Due to Surface Roughness

Signal Transmission Loss Due to Surface Roughness
In this research, parameters of various types of transmission line structures on an evaluation board were measured and analyzed in detail.
Materials Tech


Authored By:

Elaine Liew, Mitsui Copper Foil Malaysia, Shah Alam Malaysia
Taka-aki Okubo, Toshio Sudo, Shibaura Institute of Technology, Tokyo Japan
Toshihiro Hosoi, Hiroaki Tsuyoshi, Fujio Kuwako, Mitsui Kinzoku Co., Ltd, Japan


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.


In this research, parameters of various types of transmission line structures on an evaluation board were measured and analyzed in detail.

It was confirmed that reduction of signal loss for differential transmission line was greater than that for single-ended transmission line. From this, it was shown that differential transmission line is useful for the reduction of losses in high-speed signal transmission.

Signal loss has been greatly reduced by adopting low dielectric constant material. It has been confirmed that the signal loss of dielectric G1 was reduced by about 68% compared with the signal loss of FR-4.

When using the low dielectric constant materials instead of FR-4, the ratio of the conductor loss against the entire loss increases. The ratio of conductor loss for FR-4 was 13% of the total signal loss, but the conductor loss in dielectric G1 will increase to 30% among the overall loss.

If low dielectric material is used as dielectric, low roughness copper foil is effective in reducing the overall loss. Low roughness copper foil was found to reduce by 73% of the scattering loss compared with commonly used surface roughness of copper foil.

The chemical treatment on very low profile and the thin resin coating on no nodule copper foil are both very effective to improve bond strength of laminates.

Initially Published in the IPC Proceedings


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