PCB with inlaid outerlayer circuits and production methods thereof

A method for fabricating printed circuit boards comprising:

• (a) forming a thin first layer of conductive metal to transfer plate;
• (b) applying a photoresist layer over said first metal layer;
• (c) imaging the photoresist by exposure to light or radiation source thereby curing selective portions of the photoresist according to predetermined pattern;
• (d) developing by removing the uncured portions of photoresist layer to form trenches that define a pattern of circuitry layout;
• (e) forming a second layer of conductive metal on the exposed metal inside the trenches to form the circuits;
• (f) removing the cured photoresist layer, leaving the circuit pattern on said transfer plate;
• (g) laminating the transfer plate to a layer of prepreg (semi-cured dielectric substrate) with circuits facing to said prepreg;
• (h) removing said transfer plates and etch away the covering first conductive metal layers, leaving the circuits inlaid in the surface of the dielectric substrate;
• (i) drill holes through the board selectively and metallize the walls of the holes, if necessary, to interconnect circuit lines on both sides of said substrate.

A method for fabricating printed circuit boards comprising:

• (a) forming a first layer of conductive metal to transfer plate;
• (b) applying a layer of tin or eutectic tin alloy over said first metal layer;
• (c) removing selective portions of tin layer by laser ablation thereby exposing corresponding portion of the underneath metal layer;
• (d) removing portions of the conductive metal layer that not covered by tin layer;
• (e) removing remained tin layer chemically, leaving the circuit pattern on said transfer plate;
• (f) forming a thin layer of conductive metal on the surface of transfer plate and circuit;
• (g) laminating the transfer plate to a layer of prepreg (semi-cured dielectric substrate) with circuits facing to said prepreg;
• (h) removing said transfer plate and etch away the covering thin conductive metal layers, leaving circuits inlaid in the surface of the dielectric substrate;
• (j) drill holes through the board selectively and metallize the walls of the holes, if necessary, to interconnect circuit lines on both sides of said substrate.