Toroidal Ferrite Transformers With Conformal Laser Direct Structured Windings

Many applications in communications and power electronics demand inductive components that operate at high frequency or a broad range of frequencies. For applications requiring miniature devices with large inductance values, most often the components are manufactured imprecisely in the traditional method where magnetic cores are wound with a fine gauge wire. To achieve the best high-frequency performance, there is a desire to use a practical manufacturing method that removes the imprecision of wire winding. In this article, a unique 3-D laser exposure system is used to direct-write conformal winding patterns on the surface of MnZn ferrite toroids. The toroidal helix windings were fabricated by both an additive laser direct structuring (LDS) process and a subtractive laser-written mask-and-etch process. Both methods were performed on both enamel-coated ferrites and bare ferrites. The performance and equivalent circuit model parameters of the transformers were measured up to 1.5 GHz and will be presented. The transformers fabricated on the enamel-coated cores were found to have comparable or better inductances and broadband coupling than wire-wound transformers of matching construction.