A circuit assembly (200) is disclosed comprising a substrate (210) and conducting layers (250) on opposing sides of the substrate (210), there being at least one via (220) through the substrate (210), which via (220) forms a conductive path between the conducting layers, wherein the substrate (210) is a foam substrate, and wherein the via (220) is provided with a solid dielectric lining (270) plated with a conducting material (250).

A conductive network fabrication process is provided and includes filling a hole formed in a substrate with dielectric material, laminating films of the dielectric material on either side of the substrate, opening a through-hole through the dielectric material at the hole, depositing a conformal coating of dielectric material onto an interior surface of the through-hole and executing seed layer metallization onto the conformal coating in the through-hole to form a seed layer extending continuously along an entire length of the through-hole.

A wiring board includes: an insulating layer; and a connection terminal formed on the insulating layer. The connection terminal includes a first metal layer laminated on the insulating layer, a second metal layer laminated on the first metal layer, a metal pad laminated on the second metal layer, and a surface treatment layer that covers an upper surface and a side surface of the pad and that is in contact with the upper surface of the insulating layer. An end portion of the second metal layer is in contact with the surface treatment layer, and an end portion of the first metal layer is positioned closer to a center side of the pad than the end portion of the second metal layer is to form a gap between the end portion of the first metal layer and the surface treatment layer.

A wiring board includes an insulation substrate, a through-conductor, and a wiring conductor. The insulation substrate includes a first surface, a second surface opposite to the first surface, and a through-hole extending from the first surface to the second surface. The through-conductor is located in the through-hole and on an opening of the through-hole on a first surface side. The wiring conductor is located on the first surface and connected to the through-conductor. The through-conductor and the wiring conductor contain copper as a main component. The average size of Cu crystal grains in the through-conductor is larger than the average size of Cu crystal grains in the wiring conductor.

A component carrier with an electrically insulating layer having a front side and a back side, a first and a second electrically conductive layer covering the front side and the back side of the electrically insulating layer, respectively. A through hole extends through both electrically conductive layers and the electrically insulating layer. An overhang is formed along one of the electrically conductive layers and sidewalls of the electrically insulating layer structure delimiting the through hole. An annular plating layer covers the sidewalls and fills part of the overhang such that a horizontal extension of the overhang after plating is less than 20 μm and/or such that a ratio between a horizontal extension of the overhang after plating and a width of a first window through the first electrically conductive layer and/or a width of a second window through the second electrically conductive layer is smaller than 20%.

A component carrier with an electrically insulating layer having a front side and a back side, a first and a second electrically conductive layer covering the front side and the back side of the electrically insulating layer, respectively. A through hole extends through both electrically conductive layers and the electrically insulating layer. An overhang is formed along one of the electrically conductive layers and sidewalls of the electrically insulating layer structure delimiting the through hole. An annular plating layer covers the sidewalls and fills part of the overhang such that a horizontal extension of the overhang after plating is less than 20 μm and/or such that a ratio between a horizontal extension of the overhang after plating and a width of a first window through the first electrically conductive layer and/or a width of a second window through the second electrically conductive layer is smaller than 20%.

A printed wiring board includes a resin insulating layer, via conductors formed in the resin insulating layer, metal posts formed on the via conductors, respectively, and a solder resist layer formed on the resin insulating layer such that the metal posts have lower portions embedded in the solder resist layer and upper portions exposed from the solder resist layer, respectively. The metal posts are formed such that each of the metal posts has a top portion having a diameter in a range of 0.8 to 0.9 times a diameter of a respective one of the lower portions of the metal posts.

A single-layer circuit board, multi-layer circuit board, and manufacturing methods therefor. The method for manufacturing the single-layer circuit board comprises the following steps: drilling a hole on a substrate, the hole comprising a blind hole and/or a through hole; on a surface of the substrate, forming a photoresist layer having a circuit negative image; forming a conductive seed layer on the surface of the substrate and a hole wall of the hole; removing the photoresist layer, and forming a circuit pattern on the surface of the substrate, wherein forming a conductive seed layer comprises implanting a conductive material below the surface of the substrate and below the hole wall of the hole via ion implantation, and forming an ion implantation layer as at least part of the conductive seed layer.

A component carrier includes an electrically insulating layer structure having a first main surface and a second main surface with a through hole extending through the electrically insulating layer structure between the first main surface and the second main surface. An electrically conductive bridge structure connects opposing sidewalls of the electrically insulating layer structure delimiting the through hole. A vertical thickness of the electrically insulating layer structure is not more than 200 μm and a narrowest vertical thickness of the bridge structure is at least 20 μm.

Disclosed is a method for manufacturing a flexible printed circuit board and a flexible printed circuit board manufactured thereby, which minimizes a dielectric loss due to a high frequency signal and preventing a loss of the high frequency signal. The disclosed method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure includes preparing a base sheet; preparing a bonding sheet having a melting temperature lower than a melting temperature of the base sheet; forming a laminate by stacking the base sheet and the bonding sheet; and bonding by heating and pressurizing the laminate.