Flexible printed circuits and methods of fabricating and forming plated thru-holes therein

A method of making multilayer flexible printed circuits comprising the steps of

• (1) forming a plurality of printed circuit elements, each being formed by the steps of
• (a) providing a sheet of metal,
• (b) covering at least a first area of the metal sheet with a sheet of flexible material,
• (c) covering a second area of the metal sheet at least in part coterminous with the first area with a rigid printed circuit board material,
• (d) bonding the flexible material and the rigid material to the metal sheet,
• (e) etching the metal sheet to form a circuit pattern and
• (f) bonding additional flexible material and rigid printed circuit board material to the flexible material and rigid printed circuit board material, respectively, of steps (b) and (c) to sandwich the circuit pattern formed in step (e) therebetween
• (2) bonding the plurality of circuit elements together in a stack through the rigid printed circuit board substrates,
• whereby at least one portion of the multilayer flexible printed circuit does not include any layers of the flexible material therein.

A method of making a flexible printed circuit comprising the steps of:

• providing an electrically conductive layer of material having two sides, a first sheet of flexible electrically insulative material having a first edge, and a first sheet of rigid printed circuit board substrate having an edge;
• positioning said flexible sheet and said rigid sheet on a first side of said electrically conductive layer of material with said edges of said flexible and rigid sheets in abutting relation;
• bonding said sheets to said electrically conductive layer of material while maintaining the edges of said sheets in abutting relation;
• and
• forming a circuit pattern in said layer of electrically conductive material such that said circuit pattern extends between said flexible and rigid sheets.

A method of making multilayer flexible printed circuits comprising the steps of:

• (1) forming a plurality of printed circuit elements, each being formed by the steps of:
• (a) providing an electrically conductive layer of material having two sides, first and second sheets of flexible electrically insulative material each having an edge, and first and second sheets of rigid printed circuit board substrate each having edges;
• (b) positioning said first flexible sheet and said first rigid sheet on a first side of said electrically conductive layer of material with said edge of said first flexible and rigid sheets in abutting relation;
• (c) bonding said first sheets to said electrically conductive layer of material while maintaining the edges of said first sheet in abutting relation;
• (d) forming circuit pattern in said layer of electrically conductive material such that said circuit pattern extends between said first flexible and rigid shets;
• (e) positioning said second flexible and rigid sheets on a second side of said pattern conductive layer such that said second flexible and rigid sheets overlay said first flexible and rigid sheets and such that the edges of said second flexible and rigid sheets are in abutting relation;
• and
• (f) bonding said second flexible and rigid sheets to said patterned conductive layer and said first flexible and rigid sheets;
• whereby said patterned conductive layer is sandwiched between said first flexible and rigid layers and said second flexible and rigid layers;
• (2) arranging said plurality of circuit elements in a multilayer stack such that at 1east one portion of said multilayer stack does not include any layers of the flexible material therein;
• and
• (3) bonding said plurality of circuit elements together through said portion of said stack that does not includes any of the flexible material.