Abstract: A method for bending back a rigid printed wiring board with a flexible portion includes: forming a preparation substrate on a surface of a prepreg made of thermosetting resin, the preparation substrate including a conducting layer made of a conductive material; laminating the plurality of preparation substrates; thermally hardening the thermosetting resin so as to integrate the plurality of laminated preparation substrates as an intermediate substrate while heating and pressing together the plurality of preparation substrates; cutting an insulating layer formed by thermally hardening the thermosetting resin in a lamination direction of the preparation substrate so as to form a flexible portion, the flexible portion being thinly formed across opposed both edges of the intermediate substrate to form a complete substrate; bending the flexible portion; bending-back the flexible portion; and dehydrating by raising a temperature of the bent flexible portion before bending-back the flexible portion.

Abstract: A printed wiring board has a first wiring layer formed at least on one surface of an insulative substrate, an insulating layer formed as covering the first wiring layer, and a second wiring layer formed on the insulating layer. The insulating layer is formed of a cured insulative sheet made of a high-stiff sheet-type reinforcing material containing resin. The first and second wiring layers are electrically connected to each other through at least one hole having a bottom. The second wiring layer is united with the insulating layer at an interface thereof with a conductive material of the second wiring layer injected into concave sections provided on the interface. Another printed wiring board has an insulative substrate having a first surface and a second surface, a first insulating layer and a second insulating layer formed on the first surface and the second surface, respectively, and a first wiring layer formed on the first insulating layer and a second wiring layer formed on the second insulating layer.

Abstract: A printed wiring board has a first wiring layer formed at least on one surface of an insulative substrate, an insulating layer formed as covering the first wiring layer, and a second wiring layer formed on the insulating layer. The insulating layer is formed of a cured insulative sheet made of a high-stiff sheet-type reinforcing material containing resin. The first and second wiring layers are electrically connected to each other through at least one hole having a bottom. The second wiring layer is united with the insulating layer at an interface thereof with a conductive material of the second wiring layer injected into concave sections provided on the interface. Another printed wiring board has an insulative substrate having a first surface and a second surface, a first insulating layer and a second insulating layer formed on the first surface and the second surface, respectively, and a first wiring layer formed on the first insulating layer and a second wiring layer formed on the second insulating layer.

Abstract: A disclosed magnetic recording medium is provided with a single magnetic layer coated on one surface of a non-magnetic substrate. The magnetic layer has a thickness of not less than 2 .mu.m, protrusions on a plane of a height of 10 nm from a center plane in measurement of surface roughness of the magnetic layer with a density of 5000 to 9000 protrusions/mm.sup.2 and protrusions on a plane of a height of 30 nm from the center plane with a density of 500 to 2000 protrusions/mm.sup.2.