Method for electroless copper plating

Claim 1

A PROCESS FOR MAKING PRINTED CIRCUITS WHICH COMPRISES PROVIDING APERTURES IN A METAL PLATE AT POINTS DEFINING CROSS-OVERS BETWEEN THE TOP AND BOTTOM SURFACES OF THE PLATE; ANODIZING THE PLATE OF RENDER IT NON-CONDUCTING; COATING THE SURFACES OF THE ANODIZED METAL PLATE AND THE WALLS SURROUNDING THE APERTURES WITH A COMPOSITION COMPRISING AN ADHESIVE RESIN HAVING DISPERSED THROUGHOUT FINELY DIVIDED SOLID PARCLES OF AN AGENT CATALYTIC TO THE RECEPTION TO ELECTROLESS COPPER BY HEATIING THE PLATE AND IMMERSING IT IN A FLUIDIZED BED OF FINELY DIVIDED SOLID PARTICLES OF THE ADHESIVE RESIN COMPOSITION; MASKING SELECTED PORTIONS OF THE SURFACES OF THE RESULTING RESIN COATED PANEL TO LEAVE EXPOSED A CONDUCTOR PATTERN; AND IMMERSING THE RESULTING PANEL IN AN AQUEOUS ALKALINE ELECTROLESS DEPOSITING BATH COMPRISING WATER, WATER SOLUBLE CUPRIC SALT, AN ALKALI METAL HYDROXIDE, A COMPLEXING AGENT FOR CUPRIC ION, FORMALDEHYDE, AND A COMPLEXING AGENT FOR CUPROUS ION, TO THEREBY BUILD UP AN ADHERENT LAYER OF ELLECTROLESSLY DEPOSITED COPPER AT THE SITES WHERE THE CATALYTIC AGENT IS EXPOSED TO THE BATH.