Method for forming metallized patterns on the top surface of a printed circuit board

A method for forming a high density multilayer printed circuit board having a plurality of through-holes opening on the top surface, comprising the steps of:

• a) forming a plurality of pads in a predetermined pattern on a carrier layer so that each of said pads have a copper layer proximate to said carrier sheet and a joining metal layer formed on top of said copper layer;
• b) aligning a plurality of preformed core circuit boards having a predefined through-hole pattern, said plurality of boards including a top board having a top surface having externally-opening through-holes;
• c) positioning the plurality of pads on the carrier layer so that they are aligned with the through-hole pattern on the top surface;
• d) bonding the pads to the through-holes on the top surface using the joining metal layer and simultaneously laminating the plurality of boards to provide a multilayer structure;
• e) separating the carrier layer from the plurality of pads that are joined to the through-holes, so that the copper layer is exposed.

A method for attaching pads to a high density multilayer printed circuit board having a plurality of through-holes opening on the top surface, comprising the steps of:

• a) forming a plurality of pads on a carrier layer, including the substeps of
• a.i) depositing a copper surface layer on the carrier layer to provide a copper-surfaced carrier layer,
• a.ii) applying photoresist to the copper-surfaced carrier layer,
• a.iii) exposing said photoresist on the copper-surfaced carrier layer to light with a predetermined pad pattern,
• a.iv) developing and washing the exposed photoresist from step a.iii to provide a plurality of exposed copper layer areas having the predetermined pad pattern;
• a.v) depositing copper pads on the plurality of exposed copper layer areas,
• a.vi) depositing a joining metal layer on each copper pad deposited in the previous step, and
• a.vii) stripping the resist layer and the copper layer, except copper layer portions under the pads, from the carrier layer;
• b) positioning the plurality of pads on the carrier layer so that they are aligned with the through-hole pattern on the top surface of the multilayer circuit board;
• c) bonding the pads to the through-holes on the top surface using the joining metal layer;
• and
• d) separating the carrier layer from the plurality of pads that are joined to the through-holes.

A method of forming a multilayer printed circuit board comprising the steps of:

• forming a plurality of core printed circuit boards (PCBs) including a top core having a top surface that has a plurality of exposed through-holes;
• forming a plurality of pads in a predetermined pad pattern on a peelable carrier layer;
• aligning said core PCBs with respect to each other in interconnectable formation;
• aligning said predetermined pad pattern in alignment with said top surface;
• heating and compressing said core PCBs and plurality of pads;
• and
• peeling away the carrier layer to provide a multilayer PCB board having pads over the through holes in the top surface.

A method for attaching pads to a circuit board having a plurality of conductive sites arranged in a predetermined pattern at a top surface of the circuit board, comprising the steps of:

• forming a plurality of pads on a top surface of a carrier layer so that first ends of the pads are releasable from the carrier layer when the carrier layer is pulled from the first ends of the pads and so that second ends of the pads are in a pattern that match at least a portion of said plurality of conductive sites at the top surface of the circuit board;
• positioning the carrier layer so that said second ends of the pads engage said at least a portion of the plurality of conductive sites;
• bonding the second ends of the pads to said at least a portion of the conductive sites;
• and
• pulling the carrier layer from the first ends of the pads leaving the second ends of the pads bonded to the conductive sites and the first ends of the pads exposed and extending from said at least a portion of the conductive sites.