Fabrication method for a winding assembly with a large number of planar layers

Z-folding of flex circuits is presented as a method to fabricate a winding assembly having a large number of conductive and insulating layers. The process starts with a flexible sheet which contains a copper laminate bonded to an insulating laminate. Conductor patterns are then etched on the laminates and are interleaved and folded to realize the winding assembly. A large number of thin, wide turns can be connected in series or in parallel automatically during the patterning and etching processes, thus eliminating external soldering or conductive vias. Equations relating winding resistance to geometrical parameters are derived for design purposes. A product of the z-folding technique is shown, which is a transformer with a primary winding and one-turn center-tapped secondary windings