Patent ID: 7135119
Filing Date: 2006-11-14
Classification: H05K

Abstract:
1. A process for fabricating a high-density printed-circuit multilayer module, characterized in that it comprises the following steps of: preparing a substrate with printed circuits on both sides and with metallized through-holes, this substrate being prepared by using conventional printed-circuit fabrication techniques; intimately bonding, on one side of the abovementioned substrate, by means of a curable two-stage liquid epoxy adhesive, an additional layer formed from a polyimide resin film, one face of which is coated with a metal coating, said layer being bonded via the non-metallized face of the resin film; selectively etching said metal coating of the additional layer in order to remove the metal at predetermined locations intended for the microholes facing subjacent metallized regions of the substrate; anisotropic chemical drilling of the through-microholes through said film by immersing said film in a static bath of an aqueous ethylenediamine solution to which potassium hydroxide has been added in an amount proportional to the thickness of the polyimide resin film and to the transverse dimension of the microholes, at a temperature of at least 25° C., and then by rinsing with a detergent; removing the adhesive layer appearing at the bottom of the microholes passing through the film by spraying a solvent thereon so that the microholes emerge at the subjacent metallized regions of the substrate; metallizing said microholes so that their metallization is in conducting contact with the abovementioned subjacent metallized regions and with the external metal coating of said layer; and selectively etching said metal coating in order to form printed circuits thereon which are in conducting contact with said metallized microholes.