Planar transformer layer, assembly of layers for planar transformer, and planar transformer

A planar transformer comprising at least one assembly of layers including:

• plurality of primary planar transformer layer turns of windings, each of the primary planar transformer layer turns of windings comprising distinct electrical connections and thermal connections having a hole in primary layers, the hole with an extension towards an interior of the layer based on a top view to locally maximize the heat flux towards a heat sink, wherein the extension is narrower than the hole;
• and
• a plurality of secondary planar transformer layers without distinct electrical and thermal connections,
• wherein the secondary planar transformer layers are separated from the primary planar transform layer turns and covered by a dielectric material, except for the thermal connection or connections of the plurality primary planar transformer layers.