Immersion cooling is highly efficient thermal management technique and can potentially be used for thermal management of high-density data. However, to use this as a viable cooling technique, the effect of dielectric coolants on the reliability of server components needs to be evaluated. Previous work reported contradicting findings for Young’s modulus of PCBs, providing motivation for this work. This study focuses on effect of immersion cooling on the mechanical properties of printed circuit board (PCB) and its impact on reliability of electronic packages. Changes in thermo-mechanical properties like Young’s modulus (E), Glass transition temperature (Tg), of PCB and its layers due to aging in dielectric coolant are studied. Two types of PCBs using different material namely 370HR and 185HR are studied. To characterize Young’s modulus and Tg dynamic mechanical analyzer (DMA) is used. Major finding is Young’s modulus is decreasing for PCBs after immersion in dielectric coolant which is likely to increase reliability of electronics package.