PURPOSE: To make a high-density wiring possible by a method wherein two sheets of flexible substrates are formed in such a way that the total of the heights of projections or pads on the substrate on one side of the substrates, which, are butted to each other at the time of a laminating of the substrates, is longer than the total of the heights of wiring patterned conductors formed on the laminated surfaces of the two substrates.
CONSTITUTION: Two sheets of flexible substrates are formed in such a way that the total of the heights of projections or pads on the substrate on one side of the substrates, which are butted to each other at the time of a laminating of the substrates, is longer than the total of the heights of wiring patterned conductors formed on the laminated surfaces of the two substrates which are laminated together. The two sheets of the obtained flexible substrates are shown in diagrams (k) and (0). An anisotropic conductive film 11 is superposed on the flexible substrate on one side of these flexible substrates, the film 11 is temporarily pressure bonded to the substrate by a bonding tool, then, a protective film on the film 11 is peeled off. The projections or the pads, which correspond to each other, of the two sheets of the flexible substrates are aligned with each other and the film 11 is finally pressure bonded to the flexible substrate on one side by the bonding tool to obtain a multilayer flexible board having four layers of wirings.
INOUE YOSHINORI
ENOMOTO YUTAKA
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