| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 106 === Electroless (ELS) copper plating process has been commonly used in the PCB metallization, because the sidewalls of the through holes (THs) and microvias of PCBs are composited of resin and glass fiber, which are not conductive materials. Therefore, before copper electroplating of these THs and microvias, their sidewalls have to be metallized by the ELS copper process. The ELS copper process is not environment-friendly because it contains precious metal (i.e., Pd catalyst), formaldehyde and chelating agents. Also ELS copper plating process gives rise to several problems in the metallization of THs and microvias. For microvia filling by copper electroplating, it may cause a distinct crack between the electroplating copper layer and the copper pad at the via bottom, causing a high electrical resistance and thermal reliability problem. On the other hand, the copper plated-through-holes (PTHs) using ELS copper as seed layer easily lead to the conductive anodic filament (CAF) failure resulting in electrical insulation failure between two PTHs.
In this work, ELS copper deposition process was replaced by a reduced graphene oxide (rGO) process to form a conducting layer on the sidewalls of THs of PCBs for copper electroplating. rGO has an excellent conductivity and metal barrier capability. Also, the rGO process has more advantages such as environment-friendly, short process steps, no toxic chemicals and organic solvent. A high copper throwing power (> 90 %) in the THs with a high aspect ratio can be obtained and, also, it can pass thermal shock at 288℃ using rGO as conducting layer instead of ELS copper.
And then, the rGO grafting performance on the sidewall of the THs and the microvias was evaluated by using Raman spectroscopy. The reduction performance and chemical modification of the grafted GO were characterized by using X-ray photoelectron spectroscopy (XPS) and Grazing Incidence X-ray Diffractometer (XRD). The thickness and size of GO and the continuity and uniformity of rGO conductivity using atomic force microscope (AFM) and conductive atomic force microscope (C-AFM) will be measured, respectively. The morphology of GO before and after reduction was compared using field emission transmission electron microscope (FE-TEM). Finally, the rGO adsorbed on the sidewalls of the THs was characterized by using field emission-scanning electron microscope (FE-SEM).
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