PURPOSE: To reduce the thermal expansion coefficient of a printed wiring board in the thickness direction and to reduce the generation of various defects due to the thermal expansion of the board in the thickness direction, such as the disconnection of a through-hole plating and the like under a high-temperature environment, by a method wherein a fiber reinforced plastic made of a three-dimensional structure fabric is used for the insulating layer of the printed wiring board.
CONSTITUTION: An insulating resin 5 is impregnated in a three-dimensional structure fabric 9 and is hardened to form the fabric 9 as an insulating layer 6 and when this layer 6 is a double-sided plate, circuit conductors 7 are respectively formed on both sides of the layer 6 and when the layer 6 is a multilayer plate, a circuit conductor 7 is formed also in the middle of the layer 6. When the resin 5 inclines to expand thermally under a high-temperature environment, fibers 2, 3 and 4 in the longitudinal, lateral and thickness directions of the fabric 9 of a thermal expansion coefficient smaller than that of the resin 5 work so as to inhibit the thermal expansion of the layer 6. Thereby, the thermal expansion coefficient of a printed wiring board can be reduced also in the thickness direction in addition to conventional thermal expansion coefficients in the longitudinal and lateral directions.
SUGANO TOSHIYUKI
HATTA HIROSHI
SUZUKI MORIHIDE
HIROSHIMA NOBORU
