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Through Hole Plating of Printed Circuits with Aluminum Internal Planes

IP.com Disclosure Number: IPCOM000092332D
Original Publication Date: 1967-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Krawczyk, RJ: AUTHOR

Abstract

Printed circuit boards having aluminum internal planes are prepared as follows. Aluminum foil is bonded to an insulated material by conventional methods. A photoresist is applied to the aluminum surface in a predetermined pattern. The exposed aluminum is etched with an alkaline etchant, after which the resist is removed by conventional methods.

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Through Hole Plating of Printed Circuits with Aluminum Internal Planes

Printed circuit boards having aluminum internal planes are prepared as follows. Aluminum foil is bonded to an insulated material by conventional methods. A photoresist is applied to the aluminum surface in a predetermined pattern. The exposed aluminum is etched with an alkaline etchant, after which the resist is removed by conventional methods.

The insulating materials are now laminated. The external surfaces of the laminate are covered with copper foil. Through-holes are inserted in the laminated panels by conventional methods, for example, drilling, punching, and chemically etching.

The through-holes are treated in an alkaline solution containing sodium carbonate and trisodium phosphate at a temperature of 150 degrees F for about 1 to 5 minutes. Rinsing of the treated laminates is followed by an acid treatment in a solution of 15% by volume of sulfuric acid at a temperature of 180 degrees F for 1 to 5 minutes.

The laminates are again rinsed and followed by immersion in a chemical reduction nickel bath at a temperature of 190 to 210 degrees F for 5 minutes. This step applies a diffusion barrier of nickel to any exposed aluminum and protects the aluminum from corrosive effects of subsequent processing solutions. After rinsing, the through-holes are sensitized by a solution containing SnSO(4), 15 to 40 grams per liter, and concentrated H(2)SO(4),5 to 40 cc per liter.

Sensitization of the throug...