Cooling of cell phones and other hand-held electronics is of great importance due to the increasing power density of mobile processors in recent years. This investigation studies not only the properties of favorable phase change materials (PCMs), but also the packaging of the PCMs in order to be an effective passive thermal management technique. Various PCMs, all with differing melting points and latent heats, are investigated in this work, along with multiple enclosures designs. This study seeks to optimize the PCM-based passive thermal management systems to maintain a safe operating temperature in cell phone processors.