An entire set of silicon-based microtechnologies is developed for a high-performance H $ _2/$ air self-breathing microproton-exchange-membrane fuel-cell ( $mu$ PEMFC) pack. For improving the performance of the silicon-based $mu$ PEMFC, microflow-fields together with the electrodes at the cathode and the anode are optimally designed. For simplifying the microfabrication, a bulk-micromachining process is developed for fabricating both the cathode and the anode. Besides that the optimally designed flow-fields and electrodes are accurate fabricated, both the cathodes and the anodes can be fabricated in a same wafer with identical process. Optimized packaging conditions, such as the compression ratio and the current-collecting layer for the membrane electrode assembly (MEA), are experimentally obtained for both high fuel-cell performance and reliable silicon micropackaging. Attributed to the optimized design and the precise microfabrication, the peak power-density of the self-breathing $mu$ PEMFC is measured as high as 141.0–147.2 mW/cm $^-2$ . For adapting the output voltage to handheld electronic systems, a thin-pad planar configuration is designed for the $mu$ PEMFC pack that consists of six single cells connected in series. The planar-configured self-breathing $mu$ PEMFC pack is micropackaged on a silicon-micromachined base-chip, with the specific power as high as 271 mW/cm $^3$ measured. Experimental results demonstrate that the fuel cells can reliably work under normal environmental temperature and humidity. 1200-h continuing power supply of the $mu$ PEMFC pack is performed, resulting in stable output of about 3 V.1643