Development of non-planar interconnects for double-sided flexible copper substrates using laser assisted maskless microdeposition processes

Non-planar (3D) interconnects have an important role in the electronic packaging industry today. They allow manufacturers to save materials and space when connecting circuit components on flexible and non-planar substrates. Nowadays, double-sided flexible substrates have attracted the electronic industry to develop miniaturized flexible devices, such as sensors-on-chips, effectively and compactly. This study reports on our preliminary results for the creation of non-planar silver interconnects on the edge of double-sided copper substrates separated by a layer of polyethylene terephthalate (PET) using laser-assisted maskless microdeposition (LAMM). In the LAMM process, which is a laser-based direct write technology, suspensions of silver nano-particles are used in a layer-by-layer deposition followed by laser post sintering. This study includes the characterization of the LAMM process to achieve desired conductivity in the produced interconnects, which is the main indicator of performance for the electronic packages. Several parameters, including the deposition and laser processing parameters, are optimized to achieve interconnects free of pores, cracks and delamination with reasonable bonding. For investigating the topography and microstructure of the interconnects, an optical microscope and scanning electron microscope (SEM) are used.