Abstract: A method for the preparation a photo-mask used for photo-imaging selected areas on the surfaces of a three-dimensional printed circuit board substrate. The photo-mask comprises an opaque layer, opaque and degradation resistant to UV light, having at least one side with a contoured shape conforming to the surface irregularities on the surfaces of the three-dimensional substrate being photo-imaged. A membrane transparent and degradation resistant to UV light, having at least one side cemented to the side of the opaque layer not in contact with the surfaces of the three-dimensional substrate being photo-imaged. A pattern of grooves positioned on the opaque layer allow transmission of UV light during the photo-imaging of the surfaces of the three-dimensiional substrate. The pattern of grooves is in accordance with a conductive metal trace pattern desired on the surfaces of the three-dimensional printed circuit board substrate.