Skin Effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases exponentially with greater depths in the conductor. The electric current flows mainly at the “skin” of the conductor, between the outer surface and a level called the skin depth. Skin depth depends on the frequency of the alternating current; as frequency increases, current flow moves to the surface, resulting in less skin depth. Skin effect reduces the effective cross-section of the conductor and thus increases its effective resistance.
When the skin effect occurs, the effective resistance of the copper traces on your board will increase due to a reduction in the available cross-sectional area for current flow. To understand how this phenomenon impacts the design and manufacturing of your circuit boards requires that we quantify it.
Impacts of Skin Effect on PCB Development
- Material Selection: When selecting materials for high-speed or high-frequency applications, it is important to consider properties such as dielectric strength and copper roughness as these impact impedance and current flow.
- Trace Layout and EMI: Width, copper thickness, length of routes and clearances are all factors that determine the layout of your traces. At higher frequencies, to ensure that your design and board manufacturing meets your operational objectives, you have to consider layout restrictions. Specifically, EMI sources; such as stray capacitance, as more current flows near the surface of a conductor.
The skin effect can be a significant issue that affects how you design your PCB and how it is manufactured. Understanding the many issues that impact designing and manufacturing high-speed boards is critical to producing PCBs that will meet their operational requirements, reliably. At MADPCB, we lead the industry in building high-quality boards quickly that successfully address the many issues that affect high-speed applications.