Selectively Anodised Aluminium Foils as an Insulating Layer for Embedding Electronic Circuitry in a Metal Matrix via Ultrasonic Additive Manufacturing

Ultrasonic Additive Manufacturing (UAM) is a hybrid Additive Manufacturing (AM) process that involves layer-by-layer ultrasonic welding of metal foils and periodic machining to achieve the desired shape. Prior investigative research has demonstrated the potential of UAM for the embedding of electronic circuits inside a metal matrix. In this paper, a new approach for the fabrication of an insulating layer between an aluminium (Al) matrix and embedded electronic interconnections is presented. First, an Anodic Aluminium Oxide (AAO) layer is selectively grown onto the surface of Al foils prior to bonding. The pre-treated foils are then welded onto a UAM fabricated aluminium substrate. The bonding step can be repeated for the full encapsulation of the electronic interconnections or components. This ceramic AAO insulating layer provides several advantages over the alternative organic materials used in previous works.