Printed circuit board having holes with multiple conductors

Claim 2

A printed circuit board according to claim 1, characterised in that, in at least some of the holes, each electrical conductor extends as an arcuate layer around the surface of its associated hole.

Claim 3

A printed circuit board according to claim 1 or 2 characterised in that, in at least some of the holes, the space within each hole unoccupied by electrical conductors is at least partially blocked by a plug of dielectric material, and the electrical conductors electrically connect an individual circuit line at one level of the board with another individual circuit line at another level of the board.

Claim 4

A printed circuit board according to claim 1, 2 or 3 characterised in that, in respect of each hole, each electrical conductor has a conductive underlayer formed by an electrolessly deposited conductor and a further layer of electroplated conductor covering the layer.

Claim 5

A printed circuit board according to claim 4, characterised in that an individual electrical conductor within at least one hole is electrically connected to an individual circuit line carried upon one side of the substrate, the circuit line comprising a conductor underlayer laminated to the substrate, a second layer or conductor overlaying the underlayer, the second layer formed by electrolesa deposition, and a third layer overlying the second layer, the third layer formed by electroplating.

Claim 6

A printed circuit board according to claim 1 characterised in that each hole is defined by a main hole portion and a plurality of secondary hole portions disposed in spaced positions around the main hole portion, the periphery of the main hole portion intersecting the peripheries of the secondary hole portions so that the main hole portion is interconnected with the secondary hole portions, and that an electrical conductor is disposed upon the surface of each secondary hole portion, the electrical conductor extending arcuately around the secondary hole portion and having ends at the positions of intersections of the secondary hole portion and the main hole portion, said ends exposed at the circumference of the main hole portion.

Claim 8

A method according to claim 7 comprising forming the electrical conductors for each hole by:- fitting a masking plug into each hole, the plug formed with axially extending recesses to leave desired exposed spaced circumferentially extending surface regions of the hole; and providing conductor material on the spaced exposed circumferentially extending surface regions, the conductor material providing an electrical conductor upon each exposed surface region.

Claim 9

A method according to claim 7 comprising:- applying conductive material to cover the whole surface of each hole; inserting a masking plug into each hole to leave desired exposed spaced circumferential extending regions of the conductive material while masking other circumferentially extending regions of the conductive material; coating the exposed regions of the conductor material with an etch resistant electrically conductive substance; removing the plug; and by etching, removing the uncoated conductor material at the previously masked regions whereby the desired regions of conductive material together with their coated substance provide the circumferentially extending electrical conductors.

Claim 10

A method according to claim 7 comprising:- by an electroless plating method, providing a first layer of a conductive material to cover the surface of each hole; inserting the masking plug into each hole to leave desired exposed and spaced circumferentially extending regions of the first layer of the conductive material while masking other circumferentially extending regions of the first layer; by an electroplating method, applying a second layer of the conductive material to the exposed regions of the first layer of the conductive material so as to provide thicker exposed regions of the conductive material; coating the thicker exposed regions of the conductive material with an etch resistant electrically conductive substance; removing the plug; and etching the uncoated first layer of conductive material at the previously masked regions so as to remove those regions whereby the thicker regions of the conductive layer together with their coating substance provide the circumferentially extending electrical conductors.

Claim 11

A method according to claim 7 comprising:- providing an electroless plated layer of a conductive material upon the substrate which has been previously provided on at least one surface with a conductive layer, the electroless plated layer covering the surface of each hole and the previously provided conductive layer; screening surface areas of the electroless plated layer on the previously provided conductive layer to result in desired unscreened areas of the electroless plated layer in which conductor is required on the surface of the completed circuit board; inserting a masking plug into each hole to leave desired exposed and spaced circumferentially extending regions of the electroless plated layer within the hole while masking other circumferentially extending regions of the electroless plated layer within the hole; providing an electroplated layer to the exposed regions of the electroless plated layer within the hole thereby providing thicker exposed regions of the conductive material within each hole, the electroplated layer also covering the unscreened areas of the electroless plated layer on the surface of the substrate to provide thicker unscreened areas; coating the thicker exposed regions and thicker unscreened areas of the conductive material with an etch resistant electrically conductive substance; removing the plug and the screen; and etching away the conductive material and the previously provided conductive layer unprotected by the coating of etch resistant substance whereby thicker regions and thicker areas of conductive material together with their coating substance provide the circumferentially extending electrical conductors within the holes and the desired areas of conductor on the surface of the board.

Claim 12

A method according to claim 7 comprising completely covering the surface of each hole with a layer of conductor material and then selectively removing the conductive material at spaced circumferential positions to provide at least two circumferentially extending electrically isolated terminal layers which are spaced apart around the hole.

Claim 13

A method according to claim 12 comprising:- by an electroless plating method, providing a first layer of a conductive material to cover the surface of each hole; removing arcuate circumferentially extending regions of the conductive material to leave desired spaced circumferentially extending regions of the conductive material in each hole; and by an electroplating method, applying the second layer of the conductive material to the first layer in the desired spaced regions.

Claim 14

A method according to claim 7 comprising:- providing an electroless plated layer of a conductive material upon the substrate which has been previously provided on at least one surface with a conductive layer, the electroless plated layer covering the surface of each hole and the previously provided conductive layer; removing arcuate circumferentially extending regions of the conductive material to leave desired spaced circumferentially extending regions of conductive material in each hole; screening surface areas of the electroless plated layer on the previously provided conductive layer to result in desired unscreened areas of the electroleas plated layer in which conductor is required on the surface of the completed circuit board; providing an electroplated layer to the desired spaced regions within each hole thereby providing thicker desired exposed regions of conductive material within each hole, the electroplated layer also covering the unscreened areas of the electroless plated layer on the surface of the substrate to provide thicker unscreened areas; coating the thicker exposed regions and unscreened areas of the electroplated layer with an etch resistant electrically conductive substance; removing the screen; and etching away the conductive material and the previously provided conductive layer unprotected by the coating of etch resistant substance whereby the thicker regions and areas together with their coating substance provide the circumferentially extending electrical conductors within the holes and the desired areas of conductors on the surface of the board.

Claim 15

A method according to claim 7 comprising forming each hole and providing its conductors by:- forming a plurality of secondary holes in spaced positions around a desired axis for the hole which is to be completed; providing a layer of conductor material upon the surface of each secondary hole; and then forming a main portion of the hole along the desired axis, the main portion of the hole intersecting the peripheries of the secondary holes and removing a circumferentially extending section of the layer of conductive material in each secondary hole so as to form the completed hole with the main hole portion interconnected with secondary hole portions spaced circumferentially around the main hole portion and with each layer of conductive material providing a terminal layer which has ends at positions of intersection with the main hole portion, said ends exposed at the circumference of the main hole portion.

Claim 16

An assembly of a printed circuit board and a plurality of pins wherein the circuit board defines a plurality of holes and at least two electrical conductors are provided upon the surface of each hole, the conductors being spaced apart from one another circumferentially of each hole so as to be electrically isolated from one another with each conductor extending to an individual circuit path of the board which extends towards the hole, and each circuit board pin has a plurality of electrical conductor lines which extend longitudinally of the pin and are electrically isolated from one another, the pins inserted into individual holes with the circuit lines in electrical contact with individual electrical conductors within the holes.