Method for producing printed circuit board using photocurable resin laminate

Claim 1

A method for producing a printed circuit board, which comprises the steps of: (1) providing a metal-clad insulating base board having on both surfaces thereof a metallic conductive layer and having a plurality of through-holes with their respective entire inner walls covered with a metallic conductive layer, said through-holes containing at least one through-hole having a diameter of not greater than 0.5 mm; (2) applying to both surfaces of said metal-clad insulating base board a photocurable resin laminate comprising a support and a photocurable resin layer disposed on one surface of said support, so that both surfaces of said metal-clad insulating base board, which are inclusive of both terminal openings of each through-hole, are each covered with one surface of the photocurable resin layer remote from said support, said photocurable resin layer having: (a) a viscosity of from 10 4 to 5×10 5 poises as measured at 90° C.; (b) a thickness of from 30 to 150 μm; and (c) an ultraviolet ray transmittance of from 40 to 95% with respect to ultraviolet rays having a wave-length of 365 nm, wherein the application of said photocurable resin laminate to both surfaces of the metal-clad insulating base board is conducted under pressure so that a portion of said photocurable resin layer remote from said support intrudes locally in the inner side of each of the inner circumferential edges of both terminal openings of each through-hole and extends from said inner circumferential edge of each terminal opening along and on the inner wall of said through-hole to a depth which is not smaller than 0.3 in terms of an index n, which is defined as a ratio of said depth to the thickness of the metallic conductive layer on each surface of the metal-clad insulating base board; (3) exposing the photocurable resin layer on each surface of the metal-clad insulating base board to ultraviolet radiation through a predetermined transmitting pattern to form an exposed resin layer containing a photocured resin latent image covering both terminal openings of each through-hole; (4) subjecting the exposed resin layer on each surface of the metal-clad insulating base board to development with a developer to form an image of the photocured resin corresponding to said photocured resin latent image; and (5) etching the metallic conductive layer on each surface of the metal-clad insulating base board in areas other than the image of the photocured resin as an etching resist.

Claim 2

A method for producing a printed circuit board, which comprises the steps of: (1) providing a metal-clad insulating base board having on both surfaces thereof a metallic conductive layer and having a plurality of through-holes with their respective entire inner walls covered with a metallic conductive layer, said through-holes containing at least one through-hole having a diameter of not greater than 0.5 mm; (2) applying to both surfaces of said metal-clad insulating base board a photocurable resin laminate comprising a support and a photocurable resin layer disposed on one surface of said support, so that both surfaces of said metal-clad insulating base board, which are inclusive of both terminal openings of each through-hole, are each covered with one surface of the photocurable resin layer remote from said support, said photocurable resin layer having: (a) a viscosity of from 10 4 to 5×10 5 poises as measured at 90° C.; (b) a thickness of from 30 to 150 μm; and (c) an ultraviolet ray transmittance of from 40 to 95% with respect to ultraviolet rays having a wave-length of 365 nm, wherein the application of said photocurable resin laminate to both surfaces of the metal-clad insulating base board is conducted under pressure so that a portion of said photocurable resin layer remote from said support intrudes locally in the inner side of each of the inner circumferential edges of both terminal openings of each through-hole and extends from said inner circumferential edge of each terminal opening along and on the inner wall of said through-hole to a depth which is not smaller than 0.3 in terms of an index n, which is defined as a ratio of said depth to the thickness of the metallic conductive layer on each surface of the metal-clad insulating base board; (3) exposing the photocurable resin layer on each surface of the metal-clad insulating base board to ultraviolet radiation through a predetermined transmitting pattern to form an exposed resin layer containing a photocured resin latent image covering both terminal openings of each through-hole; (4) subjecting the exposed resin layer on each surface of the metal-clad insulating base board to development with a developer to form an image of the photocured resin corresponding to said photocured resin latent image; and (5) etching the metallic conductive layer on each surface of the metal-clad insulating base board in areas other than the image of the photocured resin as an etching resist.