Abstract: A method of applying a paste through a hole in a printed circuit board. A mask is provided with a hole with an upper larger cross-section portion and a lower smaller cross-section portion, the junction between the portions forming a ring-shaped land. The lower hole portion has a cross-section larger than the cross-section of the hole in the printed circuit board. The printed circuit board is positioned adjacent the mask with the hole therein aligned with the hole in the mask, and paste is applied to the hole in the mask from the upper hole portion. This paste is pressed through the hole in the mask and fills the hole in the circuit board with paste and coats the surface of the circuit board which is toward the mask and/or the surface which is away from the mask in the area around and close to the hole with the paste.

Abstract: The invention relates to a novel non-corrosive rosin oil flux and a novel method of soldering which comprises the use of said flux.

Abstract: An improved printed circuit board has an electrically insulating board which is made of a base containing synthetic resin, and has at least two conductors, one conductor being on one surface of said circuit board and the other conductor being on the opposite surface of the circuit board. At least one hole extends therethrough, and a conductive layer extends through the hole and covers at least part of the surface of the conductors for connecting the conductors on both surfaces of the circuit board through said hole. A filler composed of electrically insulating resin fills the hole and covers the surface of the layer for providing a highly reliable electrical connection between the two conductors on both surfaces of the circuit board.