Printed circuit board, method of making same, and photomask for use in the method
AssigneeInternational Business Machines Corporation
InventorsShinji Yamada, Yutaka Tsukada
Life of this patent
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Abstract
A printed circuit board comprises a base substrate including a conductive circuit pattern on a top surface thereof, and at least one photosensitive resin layer positioned on the base substrate. The resin layer exposure is performed through a photomask having light-shielding and exposure amount adjusting portions as part thereof to accommodate for varying resin layer thicknesses.
Claims8
A printed circuit board comprising:
- a base substrate including a conductive circuit pattern on a surface thereof;
- and
- at least one photosensitive resin layer provided on said base substrate and positioned substantially over said conductive circuit pattern, said printed circuit board being formed by exposing said photosensitive resin layer on said conductive circuit pattern with an exposure amount in accordance with a predetermined area of said conductive circuit pattern, said area of said conductive circuit pattern is performed by the use of a photomask in which a light shielding portion of a fine pattern is formed in a portion corresponding to a portion of said conductive circuit pattern, and a film thickness difference of said photosensitive resin layer from the surface of the base substrate after the exposure is set to be 5 micrometers or less.
A photomask for exposing a photosensitive resin coated on a base substrate including a conductive circuit pattern on a surface thereof, and wherein said resin is located substantially atop said circuit pattern, said photomask comprising:
- light shielding portion corresponding to a portion of said photosensitive resin under which said conductive circuit pattern is not formed;
- an exposure amount adjusting portion formed of a fine pattern in accordance with the area of said conductive circuit pattern on said surface of said base substrate and located over said conductive circuit pattern;
- and
- light shielding portions positioned over selected parts of said conductive circuit pattern for exposing via holes in said photosensitive resin down to said circuit pattern, and a film thickness difference of said photosensitive resin layer from the surface of the base substrate after exposure is set to be 5 micrometers of less.
A manufacturing method for making a printed circuit board, said method comprising the steps of:
- coating a photosensitive resin on a base substrate including a conductive circuit pattern on a surface thereof;
- exposing light on a position of said conductive circuit pattern with an exposure amount in accordance with a predetermined area of said conductive circuit pattern;
- and
- developing said exposed photosensitive resin to remove a portion of said photosensitive resin on said conductive circuit pattern in accordance with the area of said conductive circuit pattern, thus setting a film thickness difference of the layer of said photosensitive resin from the surface of the base substrate to 5 micrometers or less.
Dependencies are inferred from the claim text.