Al Electrodeposition to make plated through holes in printed circuit boards using ionic liquids

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Omni Circuit Boards is a Printed Circuit Board manufacturer located in Richmond, BC which began development of a fine-line aluminum trace printed circuit board (PCB) in 2008 for its superconductive capabilities at low (cryogenic) temperature. Multi-layer versions are of interest to many customers. This requires electrical connectivity between layers of the PCB. The current product is limited to single layer applications which limits its market. Al will be electrodeposited on the sides of the through holes (PTHs) which will provide the interlayer electrical connectivity. The all-aluminum electrical path is required which would demand the plated through hole be constructed entirely of aluminum. Many methods were attempted, but none were successful. This research proposal will develop a new method using room temperature molten salts (also called ionic liquids-ILs). The electrolyte and methods developed will be easily transferred to industry. The optimum conditions will be determined based on systematic studies of the many operating parameters: current density, temperature, electrolyte composition and use of additives etc. The morphology and characteristics of the deposited layer will be investigated using scanning electron microscopy (SEM/EDS), X-Ray Diffraction (XRD) and optical microscopy (OM) so as to determine the optimum process conditions. The ultimate goal is to electrodeposit dense, bright and adherent Al layers on the sides of of PTHs, so as to ensure electrical connections between the electric and dielectric layers of PCBs.