Patent ID: 8536459

Claim:
A substrate for use in a PC board comprising: a) a flexible thermoplastic dielectric having two major surfaces; b) a first and a second metal layer attached to each of said major surfaces, respectively; c) at least two coreless, partially-filled thermoset resin-coated Cu-based buildup layers disposed respectively on said first and said second metal layers; d) a third and a fourth metal layer disposed on said at least two coreless buildup layers, respectively; and e) an electrical connection between said first and said second metal layers, and said first and said third metal layers, and said first and said fourth metal layers, and said second and said third metal layers, and said second and said fourth metal layers, and said third and said fourth metal layers; wherein said thermoplastic dielectric has dimensions greater than the dimensions of said coreless, partially-filled thermoset resin-coated Cu-based buildup layers, resulting in an extended flexible thermoplastic layer; and whereby a high density, thin substrate is produced.