The low leakage inductance of planar transformers; fact or myth?

Planar transformers have been touted to have a low leakage inductance, although an analysis of several alternatives show that the planar transformer is actually among the worst of the low profile designs from a geometric standpoint. Other `equivalent´ geometries can actually have a leakage inductance which is 10 to 50 times lower than the planar construction. The only benefit of the planar transformer in this regard is the relative ease with which primary and secondary windings can be heavily interleaved, lowering leakage inductance dramatically at the expense of high capacitance coupling between the primary and secondary windings