A method for manufacturing a flexible circuit board is provided. The method for manufacturing a flexible circuit board includes the following steps: providing a carrier substrate, forming a flexible substrate on the carrier substrate, and forming a plurality of circuit strings on the flexible substrate. A flexible circuit board manufactured by the above method is also provided.

A method of manufacturing a circuit board includes: forming a plurality of metal electrodes so as to be separated from each other on a holding sheet by cutting a metal foil held on the holding sheet to remove a portion of the metal foil; forming adhesive layers on surfaces of the plurality of metal electrodes; adhering the adhesive layers to a base material by closely contacting the adhesive layers with the base material; and transcribing the adhesive layers and the plurality of metal electrodes onto the base material by detaching the holding sheet from the plurality of metal electrodes.

A method of producing an electrical through connection. A cut extending from a first surface to a second surface and separating the area into a first part and a second part is provided on an area of the flexible substrate. At least one of the first and second part is raised from a first plane of the first surface. A first wet conductive layer is printed on the first surface on and around the cut. The first wet layer is solidified into a first dried conductive layer. At least one of the first part and the second part is raised from a second plane of the second surface. A second wet conductive layer is printed on the second surface on and around the cut. The second wet conductive layer is solidified into a second dried conductive layer, which creates an electrical through connection with the first dried conductive layer.

A crimp terminal-equipped flexible printed circuit board includes: a first flexible printed circuit board having a base film and a circuit provided on a surface of the base film and made of metal foil; multiple crimp terminals including crimp pieces crimped to penetrate the first flexible printed circuit board and bent to bite into part of the circuit; and an insulating reinforcing film partially integrally provided on an area of the base film where the multiple crimp pieces penetrate.

Provided is a stretchable circuit board including: a stretchable base material having stretchability and including a stretchable wiring line on one main surface; an electrode formed on at least the main surface of the stretchable base material and connected to the stretchable wiring line; an adhesive layer directly or indirectly bonded to the main surface on which the electrode is formed and formed in a region of the main surface other than an electrode region including the electrode; and an adhesive layer separator detachably bonded to the adhesive layer and having an opening formed at a position corresponding to at least part of the electrode region.

A method of manufacturing a circuit board includes: forming a plurality of metal electrodes so as to be separated from each other on a holding sheet by cutting a metal foil held on the holding sheet to remove a portion of the metal foil; forming adhesive layers on surfaces of the plurality of metal electrodes; adhering the adhesive layers to a base material by closely contacting the adhesive layers with the base material; and transcribing the adhesive layers and the plurality of metal electrodes onto the base material by detaching the holding sheet from the plurality of metal electrodes.

Provided is a stretchable circuit board including: a stretchable base material having stretchability and including a stretchable wiring line on one main surface; an electrode formed on at least the main surface of the stretchable base material and connected to the stretchable wiring line; an adhesive layer directly or indirectly bonded to the main surface on which the electrode is formed and formed in a region of the main surface other than an electrode region including the electrode; and an adhesive layer separator detachably bonded to the adhesive layer and having an opening formed at a position corresponding to at least part of the electrode region.

A glass substrate having a plurality of holes includes a first surface and a second surface, which are opposite to each other. Each of the holes is arranged so as to have an aperture on the first surface. The plurality of holes includes a first hole group including a plurality of first holes having a first aperture diameter including a first variation, and a second hole group including a second hole or a plurality of second holes having a second aperture diameter including a second variation. Each of the first holes has an aspect ratio of greater than 1, and a surface roughness on an inner wall (arithmetic average roughness Ra) of less than 0.1 m. The second aperture diameter is greater than the first aperture diameter by 15% or more, or less than the first aperture diameter by 15% or more.

Provided is a technique that can achieve an insulating layer with small surface undulations and can suppress a haloing phenomenon in manufacturing a printed wiring board even when using a thin resin composition layer. Specifically, provided is a method for manufacturing a printed wiring board that includes the steps of: (A) preparing a resin sheet with an inorganic layer including (i) a support with an inorganic layer including an inorganic layer, a support in contact with the inorganic layer, and a release layer and (ii) a resin composition layer in contact with the release layer of the support with an inorganic layer; (B) laminating the resin sheet with an inorganic layer onto an internal layer substrate so that the resin composition layer of the resin sheet with an inorganic layer is in contact with the internal layer substrate; (C) curing the resin composition layer to form an insulating layer; and (D) perforating the insulating layer.

A method of manufacturing an intermediate product for an interposer including a glass substrate having a plurality of through holes is provided. The method includes a step of forming a resin layer on a support substrate, and a step of forming a laminated body by adhering the glass substrate having the plurality of through holes on the resin layer. The glass substrate having the plurality of through holes has a thickness within a range of 0.05 mm to 0.3 mm.