Method of plating solder onto printed circuit boards

Claim 1

A method of providing a through-connection between the conductors of two circuits on opposite faces of a double-sided printed circuit board, which method comprises in sequence the steps of: providing a board which has printed circuit conductors preformed opposite each other on opposite faces of the board and an aperture preformed in the board and extending through said board and through the printed circuit conductors on said opposite faces of said board; plating an electrically conductive material simultaneously on the whole of said faces and on the wall of the aperture and thereby continuously plating from on one face of the board through the aperture onto the opposite face of the board, wherein said electrically conductive material is applied directly onto the conductors of the printed circuit and onto the surfaces of said board between said printed circuit conductors; forming an electrically insulating mask on said faces while leaving exposed the conductive surface on the wall of the aperture and selected areas of the printed circuits, the said selected areas including a margin surrounding each mouth of the aperture, said mask-forming step including preparing a negative of the desired mask and thereby applying electrically insulating material over portions of said board including portions of said printed circuit conductors thereon except for selected areas including said margins immediately surrounding each end of said aperture; electro-plating solder on the wall of the aperture and the said selected areas using said electrically conductive material as one electrode, said step of electro-plating solder including applying of a solder layer over the initial electrically conductive material plated on said aperture wall and faces of said board in said initial plating step preceding said masking step; removing the mask; and removing the electrically conductive material, whereby a double-sided, printed-circuit board with a selectively solderplated through-connection is obtained.

Claim 2

A method of providing a through-connection between the conductors of two circuits on opposite faces of a double-sided printed circuit board, which method comprises in sequence the steps of: providing a board which has printed circuit conductors preformed opposite each other on opposite faces of the board and an aperture preformed in the board and extending through said board and through the printed circuit conductors on said opposite faces of said board; plating an electrically conductive material simultaneously on the whole of said faces and on the wall of the aperture and thereby continuously plating from on one face of the board through the aperture onto the opposite face of the board, wherein said electrically conductive material is applied directly onto the conductors of the printed circuit and onto the surfaces of said board between said printed circuit conductors; forming an electrically insulating mask on said faces while leaving exposed the conductive surface on the wall of the aperture and selected areas of the printed circuits, the said selected areas including a margin surrounding each mouth of the aperture, said mask-forming step including preparing a negative of the desired mask and thereby applying electrically insulating material over portions of said board including portions of said printed circuit conductors thereon except for selected areas including said margins immediately surrounding each end of said aperture; electro-plating solder on the wall of the aperture and the said selected areas using said electrically conductive material as one electrode, said step of electro-plating solder including applying of a solder layer over the initial electrically conductive material plated on said aperture wall and faces of said board in said initial plating step preceding said masking step; removing the mask; and removing the electrically conductive material, whereby a double-sided, printed-circuit board with a selectively solderplated through-connection is obtained.