Patent ID: 6168725
Filing Date: 2001-01-02
Classification: C23F,H05K

Abstract:
A method for chemically milling aluminum from copper-aluminum-copper tri-metal layers, the method comprising the steps of: providing a tri-metal laminate having layers of copper-aluminum-copper having copper circuit patterns present on opposing surfaces of an aluminum foil, and contacting the tri-metal laminate with an etchant comprising an aqueous solution of: (1) 60 to 500 g/l base selected from the group consisting of sodium hydroxide, potassium hydroxide, and mixtures thereof; and (2) 30 to 500 g/l of a salt selected from the group consisting of nitrite salt, borate salt, bromate salt, and mixtures thereof at a temperature of 25 to 95.degree. C. for a time sufficient to selectively remove a desired amount of the aluminum layer and form a electronic circuitry which contains multiple conductive copper circuit layers.