INTERLAYER CONNECTION CONDUCTOR AND MANUFACTURING METHOD THEREOF
An interlayer connection conductor 1 is formed of a substantially spherical interlayer connector that is formed by forced in through holes 108 , in a thickness direction, on a flexible printed circuit board having wiring layers 106, 107 on at leas one surface of an insulating layer The interlayer connection conductor includes a small cylindrical piece of metal core 102 formed by cutting a metal fine wire and a solder metal 103 coated around the surface of the metal core.
1 . An interlayer connection conductor, which is formed in a substantially spherical shape and is press-fitted in a through hole formed in a printed circuit board in a thickness direction so as to serve an interlayer connector, the printed circuit board having a wiring layer that is formed on at least one side of an insulating layer, the interlayer connection conductor comprising:
a metal core that is a small piece formed by cutting a metal wire; and
a solder metal that covers the surface of the metal core.
2 . The interlayer connection conductor according to claim 1 , wherein the metal core is a cylindrical small piece formed by cutting the metal wire.
3 . The interlayer connection conductor according to claim 2 , wherein the metal core is formed such that a diameter of the cylindrical small piece is equal to or larger than a height of the metal core.
4 . The interlayer connection conductor according to claim 1 , wherein the metal core is formed by cutting the metal wire formed of one or more kinds of soft metal.
5 . The interlayer connection conductor according to claim 1 , wherein the metal core is formed by cutting the metal wire including at least copper or copper alloy.
6 . The interlayer connection conductor according to claim 1 , wherein the solder metal is a solder alloy.
7 . The interlayer connection conductor according to claim 1 , wherein the printed circuit board is a flexible printed circuit board.
8 . A method of manufacturing an interlayer connection conductor comprising:
cutting a metal wire by a predetermined length to form a metal core;
disposing the metal core in a recess of a heat resistant substrate;
coating a solder metal to cover the metal core disposed in the recess; and
covering the metal core with the solder metal in a substantially spherical shape by heating and melting the solder metal.
9 . The method of manufacturing an interlayer connection conductor according to claim 8 , wherein the solder metal is a cream soldering paste.
10 . The method of manufacturing an interlayer connection conductor according to claim 8 , wherein the solder metal is a solder ball.
11 . The method of manufacturing an interlayer connection conductor according to claim 8 , wherein the solder-covered metal core having a solder metal covered on its outer peripheral surface is formed by cutting a solder-covered metal wire in a predetermined length, the surface of the solder-covered metal wire being covered with a solder metal layer at a predetermined thickness.
12 . A flexible printed circuit board comprising:
a wiring layer that is formed on at least one side of an insulating layer, a metal core that is a small piece formed by cutting a metal wire; and
an interlayer connection conductor that is formed of a solder metal covering the surface of the metal core,
wherein the interlayer connection conductor is press-fitted in a through hole formed in the flexible printed circuit board in a thickness direction.