Abstract: A circuit board including a desired number of electrically insulating layers and wiring layers laminated alternately, and an inner via hole for securing an electrical connection between the wiring layers by compressing and hardening a conductive paste including a conductive particle and a resin. In the electrically insulating layer, a porous sheet is provided a resin sheet at least one surface, and the porous sheet is not impregnated with a resin at least at a central portion. A through hole penetrating the electrically insulating layer in the direction of the thickness of the electrically insulating layer is filled with a conductive paste including a conductive particle and a resin, and pores that are present inside the porous sheet are filled with laminated resin. The average hole diameter of the pores inside the porous sheet may be smaller than the average particle size of the conductive particle.

Abstract: A circuit board is configured so as to include not less than two wiring layers, an insulator layer for electric insulation between the wiring layers, and an inner-via-hole conductive member provided in the insulator layer in a thickness direction of the insulator layer, for electric connection between the wiring layers. The insulator layer is made of a composite material containing an organic resin and a material having a smaller thermal expansion coefficient than that of the organic resin, and includes a surface part, a core part, and a surface part laminated in the stated order, the surface part having a high content of the organic resin, the core part having a low content of the organic resin. The wiring layers have a land portion that is connected with the inner-via-hole conductive member, the land portion being embedded so as to be substantially in contact with the core part, and the inner-via-hole conductive member has a thickness substantially equal to a thickness of the core part.

Abstract: A compression function layer 60 is provided on at least one board surface. The compression function layer 60 adds a function of being compressed by receiving pressure in the direction of the board thickness to the resin board 10 which includes this layer. Thereby a sufficient pressure is applied to conductors 14.

Abstract: Removable mask films 303 are formed on the both sides of the substrate having the adhesive layer 302 by applying and drying a resin varnish 304 including a ultraviolet-absorbing agent, and fine through holes 306 are formed by using a third harmonics YAG solid-state laser light with a relatively short wavelength not longer than that in the ultraviolet range in such a way that the effects of such a residual strain as the conventional embodiment forming a removable mask film by a laminating process may be decreased as well as the more fine hole drilling compared with conventional embodiment using the carbon dioxide gas laser with a relatively long wavelength may be performed.

Abstract: A printed circuit board of the present invention is formed of an electrical insulating base material with through holes that are formed in a thickness direction of the electrical insulating base material and are filled with an electrical conductor; the electrical insulating base material including a core layer formed by impregnating a holder with a resin and resin layers formed on both sides of the core layer; and wiring layers that are formed on both surfaces of the electrical insulating base material into a predetermined pattern and are electrically connected to each other by the electrical conductor. The wiring layer is embedded in at least one of the resin layers. The resin layers on the both sides have different thicknesses from each other, and a thinner layer out of the resin layers has a thickness equal to or smaller than a mean particle diameter of an electrically conductive filler contained in the electrical conductor.

Abstract: The present invention provides a printed circuit board, which includes a dielectric substrate having via holes formed in the thickness direction, and a conductor including a conductive filler is filled in the via holes. The dielectric substrate has patterned wiring layers on both surfaces, and the wiring layers are connected electrically with each other by the conductor. The dielectric substrate is made of a glass cloth or a glass nonwoven fabric impregnated with a thermosetting epoxy resin mixed with fine particles, and the conductive filler in the conductor has an average particle diameter larger than that of the fine particles. Accordingly, the printed circuit board has an improved moisture resistance as a whole and also excellent connection reliability and repair resistance. In addition, the dielectric substrate of the printed circuit board has an improved mechanical strength such as flexural rigidity. The present invention also provides a method of manufacturing such a printed circuit board.

Abstract: The present invention provides a thin multilayer magnetic recording medium having improved electromagnetic conversion property and durability, comprising coating layers of a lower non-magnetic layer and an upper magnetic layer. The non-magnetic layer of this magnetic recording medium comprises a non-magnetic needle body having an average major axis length of 0.25 to 1.0 .mu.m and an average minor axis length of 0.005 to 0.0151 .mu.m, a first binding resin having a glass transition temperature (Tg.sub.1) of 30 to 50.degree. C., and fatty acid ester. The content of the first binding resin is 15 to 30 wt % with respect to the non-magnetic needle body. The content of the fatty acid ester is 2 to 15 wt % with respect to the first binding resin. The magnetic layer having a dry thickness of 0.5 .mu.m or less comprises ferromagnetic powder and a second binding resin having a glass transition temperature (Tg.sub.2) of 40 to 70.degree. C. Tg.sub.1 is at least 5.degree. C. lower than Tg.sub.

Abstract: Of disk-shaped or tape-shaped magnetic recording media composed of non-magnetic supports and magnetic layers which, formed on the supports, contain a magnetic powder and a binder for it, the magnetic recording medium having superior electro-magnetic conversion characteristics, high durability, and high reliability has been obtained as a result of improving the abrasion resistance of the magnetic layer without impairing the surface smoothness thereof, by incorporating a non-magnetic inorganic powder of at least 5 Mohs hardness which has a dendrite or chain structure.

Abstract: A magnetic recording medium which comprises a support and a magnetic layer formed on opposite sides of the support and comprised of a ferromagnetic fine powder and an non-magnetic powder of an abrasive both dispersed in a resin binder. The non-magnetic powder consists essentially of a first non-magnetic inorganic powder having an average particle size of from 0.01 to 1.0 .mu.m and a second non-magnetic inorganic powder having an arborescent or chain-like structure and an average particle size of from 0.03 to 2.0 .mu.m. The first and second powders is present at a mixing ratio by weight of 8:2 to 2:8.