Patent ID: 8692640

Claim:
An apparatus comprising a printed circuit board and a magnetic ring, said printed circuit board comprising a stack, along a vertical direction, of several metallization layers separated mechanically from one another by electrically insulating layers, a first coil that extends along a first vertical winding axis, said first coil having turns formed by conductive tracks made in respective metallization layers and electrically connected to one another by pads going through at least one of said electrically insulating layers, first and second vertical holes crossing said printed circuit board from a first side thereof to a second side thereof, said first vertical hole extending along said first vertical winding axis, and said magnetic ring being formed by an upper U-shaped part and a lower U-shaped part, each of said upper U-shaped part and said lower U-shaped part comprising two vertical arms each introduced into a respective hole of said printed circuit board, each arm of said upper U-shaped part being superimposed, within said respective hole, and in a horizontal direction, on a corresponding arm of said lower U-shaped part to establish magnetic continuity between said upper U-shaped part and said lower U-shaped part of said magnetic ring, wherein transverse dimensions of a superimposition of said vertical arms are smaller, by at least 5 μm, than corresponding transverse dimensions of said holes, and thereby establishing a clearance between vertical walls of said holes and facing vertical faces of said magnetic ring, wherein said transverse dimensions are dimensions parallel to a plane defined by said metallization layers.