Flexible board

摘要

A flexible board comprises metal foil 1 and provided thereon a laminated polyimide-based resin layer 2 of a three-layer structure comprising a first polyimide-based resin layer 2a, a second polyimide-based resin layer 2b, and a third polyimide-based resin layer 2c, wherein the following equation is satisfied. $where\; k1\; is\; the\; coefficient\; of\; linear\; thermal\; expansion\; of\; the\; first\; polyimide-based\; resin\; layer\; 2a\; on\; the\; side\; of\; the\; metal\; foil\; 1,\; k2\; is\; the\; coefficient\; of\; linear\; thermal\; expansion\; of\; the\; second\; polyimide-based\; resin\; layer\; 2b,\; and\; k3\; is\; the\; coefficient\; of\; linear\; thermal\; expansion\; of\; the\; third\; polyimide-based\; resin\; layer\; 2c.\mathop{\mathrm{image}}$