the rigid support 18 as shown in fig6 this lamination is typically done by placing the compensator core 17 over the second polymer layer 21 such as a polyimide coating and heating up to 150 degrees c at 2 3 degrees c min ramp rate while applying 50 psi pressure the via openings 13 in the compensator core 17 are then filled with a polymer this is illustrated in fig8 which shows the thin metal foil 11 having openings or via patterns 13 filled with a polymer 25 such as a polyimide in order to obtain a good bond the polymer 25 should be of the same material as the partially cured second polymer layer 21 as shown in fig8 or it could be of a different material as long as it is compatible with the partially cured second polymer 21 that was applied on the surface of the rigid support 18 as shown in fig8 the polymer 25 is the same as polymer 21 and therefore they diffuse and form a single polymer 25 the via fill process according to this invention is such that it provides void free polyimide filled vias after the via openings 13 are filled with the polymer 25 and the upper surface of the compensator core 17 has had a sufficient deposition of polymer 25 the structure is then cured to 350 400 degrees c the top surface of the cured structure preferably is planarized fig9 illustrates the structure after planarization with the polyimide having a planarized surface 27 after the structure has been planarized openings or etched via holes 33 and.