Process for producing a collapsed filled via hole

A process for producing a collapsed filled via hole comprising

• placing an insulating resin sheet with or without a conductive material sheet on at least one surface of the resin sheet having a through hole, and a conductive metal sheet having a thickness larger than the resin sheet in this order on a die hole provided in a metal mold;
• punching the conductive metal sheet with a punch of substantially the same size as the through hole and set over the position corresponding to the hole thereby producing a chip of the conductive metal, the chip of conductive metal is pressed into the resin sheet by the punch to form a filled via hole with a first end and second end, whereby the chip is inserted and remains in the through hole, wherein the punch does not reach the resin sheet;
• and
• collapsing the first end and the second end of the filled via hole to externally spread like an umbrella thereby producing the collapsed filled via hole,
• wherein the chip of conductive metal protrudes from both surfaces of the resin sheet by 10 to 500 μm.

A process for producing a collapsed filled via hole comprising:

• (A) placing an insulating resin sheet, optionally including a conductive material sheet on at least one surface of the resin sheet, in a die hole provided in a metal mold;
• (B) placing a conductive metal sheet having a thickness larger than the resin sheet in the die hole;
• (C) punching the resin sheet in (A) and the metal sheet in (B) with a punch that does not reach the resin sheet thereby producing a chip of the metal sheet in (B), the chip of the metal sheet in (B) is pressed into the resin sheet in (A) by the punch, whereby a through hole is formed in the resin sheet in (A) and the chip is inserted and remains in the through hole to form a filled via hole with a first end and a second end;
• and
• (D) collapsing the first end and the second end of the filled via hole to externally spread like an umbrella thereby producing the collapsed filled via hole,
• wherein the chip of conductive metal protrudes from both surfaces of the resin sheet by 10 to 500 μm.