There are many different factors that can influence PCB impedance control, including the dialectic constant value, copper thickness, trace width/spacing and dielectric thickness, now Shenzhen KEYOU PCB manufacturer tells you a clear understanding to these different factors.
If the dielectric constant increases, the impedance declines, on the other hand, the impedance increase.The dielectric constant is related to the resin contain of lamination:the dielectric constant is 3.9-4.8 of FR4 material, the impedance will decline as the using frequency is increased.
The copper thickness is controlled according to the pattern copper plating and different base copper.The impedance is reduced when the copper thickness is increased, while the impedance is increase when the copper thickness is reduced.To prevent the influence of asymmetric copper thickness to the impedance control, the dummy copper is designed on isolated trace or the independent to balance the electrical current and ensure the copper thickness on CS and SS is symmetrical during the copper plating.
The impedance is increased when the trace width is declined, otherwise, the impedance is declined. During the impedance design, the trace width/spacing should be controlled in +/- 10%. It is only to adjust the trace width/spacing to control the impedance when the dielectric thickness and constant is confirmed. At the same time, the copper area is design on the corresponding layer to ensure the stability of impedance signal.
When the dielectric thickness goes up and the impedance performance value increases otherwise declines. To design the impedance, the dielectric is conducted by prepreg and lamination, the resin content is different in prepreg and lamination that with same thickness. And the dielectric thickness is related to the pressing machine smoothness, program and the pattern distribution.
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