Wiring board and method for producing the same

A wiring board comprising:

• an insulating substrate;
• first and second feeding electrodes provided along both sides in a longitudinal direction of the insulating substrate;
• a plurality of feeding bus lines extending in a traverse direction of the insulating substrate and connected to at least one of the first and second feeding electrodes;
• a plurality of conductor wirings provided in each unit region defined by the feeding bus lines, one side terminals thereof forming inner leads and the other side terminals thereof being connected to the feeding bus lines;
• and
• a protruding electrode formed on each of the inner leads of the conductor wirings,
• wherein the inner leads belonging to each unit region form a first group and a second group arranged in two lines extending in the traverse direction of the insulating substrate, with tips of the inner leads of the first group and tips of the inner leads of the second group facing each other, and
• the inner leads of the first group are arranged with a dense wiring pitch, and the inner leads of the second group include a dense pitch region in which a wiring pitch thereof is the same as that of the inner leads of the first group and a sparse pitch region in which a wiring pitch thereof is longer than that of the inner leads of the first group,
• the feeding bus lines include first feeding bus lines connected to the first feeding electrode and second feeding bus lines connected to the second feeding electrode, the first feeding bus lines and the second feeding bus lines being arranged alternately,
• the conductor wirings forming the inner leads of the first group and the inner leads in the dense pitch region of the second group are connected to the first feeding bus line, and
• the conductor wirings forming the inner leads in the sparse pitch region of the second group are connected to the second feeding bus line.

A method for producing a wiring board, comprising the steps of:

• forming first and second feeding electrodes provided along both sides in a longitudinal direction of an insulating substrate, a plurality of feeding bus lines extending in a traverse direction of the insulating substrate and connected to at least one of the first and second feeding electrodes, and a plurality of conductor wirings provided in each unit region defined by the feeding bus lines, wherein inner leads are formed with one side terminals of the conductor wirings and the other side terminals thereof are connected to the feeding bus lines so that the inner leads belonging to each unit region form a first group and a second group arranged in two lines extending in the traverse direction of the insulating substrate, with tips of the inner leads of the first group and tips of the inner leads of the second group facing each other, and the inner leads of the first group are arranged with a dense wiring pitch, and the inner leads of the second group include a dense pitch region in which a wiring pitch thereof is the same as that of the inner leads of the first group and a sparse pitch region in which a wiring pitch thereof is longer than that of the inner leads of the first group;
• forming a photoresist on the surface on which the conductor wirings are provided;
• forming an opening in the photoresist, the opening extending across the inner leads and spreading over both side areas of the inner leads, to expose a portion of the inner leads in the opening;
• and
• feeding a plating current to the inner leads via the feeding bus lines from the first and second feeding electrodes, to subject the exposed portion of the inner leads to electrolytic metal plating, to form protruding electrodes,
• wherein the conductor wirings forming the inner leads of the first group and the inner leads in the dense pitch region of the second group are connected to the feeding bus line on one side of each unit region, and the conductor wirings forming the inner leads in the sparse pitch region of the second group are connected to the feeding bus line on the other side of each unit region;
• and
• the plating current is supplied to the feeding bus lines through the first and second feeding electrodes from positions thereof on both sides with respect to the feeding bus lines in the longitudinal direction of the feeding electrodes.

A method for producing a wiring board, comprising the steps of:

• forming first and second feeding electrodes provided along both sides in a longitudinal direction of an insulating substrate, a plurality of feeding bus lines extending in a traverse direction of the insulating substrate and connected to at least one of the first and second feeding electrodes, and a plurality of conductor wirings provided in each unit region defined by the feeding bus lines, wherein inner leads are formed with one side terminals of the conductor wirings and the other side terminals thereof are connected to the feeding bus lines so that the inner leads belonging to each unit region form a first group and a second group arranged in two lines extending in the traverse direction of the insulating substrate, with tips of the inner leads of the first group and tips of the inner leads of the second group facing each other, and the inner leads of the first group are arranged with a dense wiring pitch, and the inner leads of the second group include a dense pitch region in which a wiring pitch thereof is the same as that of the inner leads of the first group and a sparse pitch region in which a wiring pitch thereof is longer than that of the inner leads of the first group;
• forming a photoresist on a surface on which the conductor wirings are provided;
• forming an opening in the photoresist, the opening extending across the inner leads and spreading over both side areas of the inner leads, to expose a portion of the inner leads in the opening;
• and
• feeding a plating current to the inner leads via the feeding bus lines from the first and second feeding electrodes, to subject the exposed portion of the inner leads to electrolytic metal plating, to form protruding electrodes,
• wherein the feeding bus lines include first feeding bus lines extending in the traverse direction of the insulating substrate and connected to the first feeding electrode, and second feeding bus lines extending in the traverse direction of the insulating substrate and connected to the second feeding electrode, the first feeding bus lines and the second feeding bus lines being alternately arranged,
• the conductor wirings forming the inner leads of the first group and the inner leads in the dense pitch region of the second group are connected to the first feeding bus line, and the conductor wirings forming the inner leads in the sparse pitch region of the second group are connected to the second feeding bus line, and
• the first feeding electrode and the second feeding electrode are supplied with plating currents separately.