A Guide to Designing Copper-Foil Inductors

Jul 1, 2007 12:00 PM
By Patrick Scoggins Senior Design Applications Engineer, Datatronics, Romoland, Calif.

Click here for the enhanced PDF version of this article including diagrams and/or equations.

The basic principles of magnetic design and the techniques used to build magnetic components have not changed for many years. The general approach combines standard round magnet wire with various types of core materials and shapes. There have been breakthroughs with different core materials that operate at higher frequencies and extended temperature ranges. Nevertheless, magnet wire has remained relatively unchanged with only minor variations to accommodate different operating temperatures.

Currently, the majority of inductors are designed with standard round magnet wire. However, in some designs, an alternative to round magnet wire — copper foil — may be the better option for the winding.

Copper foil offers several advantages. One is size reduction since components wound with copper foil tend to use the winding space more efficiently. Better heat dissipation is another benefit because the mass of the solid conductor can withdraw heat from the center of the coil more effectively than magnet wire. Yet another advantage is the reduction in voltage stresses between turns of a foil winding.^[1] In addition, a foil-wound component has greater mechanical strength than a wire-wound component, which makes the copper-foil component far more robust.

Different types of copper foil are available for use in magnetic designs. Depending on the application, the choice of copper can be certified oxygen-free high-conductivity copper (CDA 10100), oxygen-free high-conductivity copper (CDA 10200) or Electrolytic Tough-Pitch (ETP) copper (CDA 11000).

The CDA 10100 and CDA 10200 are the best choices for optimized applications where cost may not be an issue. These types of copper alloys have the highest purity compared to the ETP type.^[2] For commercial applications where cost is an issue, the ETP is the best choice.

Want to use this article? Click here for options!
© 2007 Penton Media, Inc.