  Within the mass range of $10^{16}-5\times 10^{18}$ g, primordial black holes
(PBHs) persist as plausible candidates for dark matter. Our study involves a
reassessment of the constraints on PBHs through a comparative analysis of the
cosmic X-ray background (CXB) and the emissions arising from their Hawking
evaporation. We identify previously overlooked radiation processes across the
relevant energy bands, potentially refining the bounds on PBHs. These processes
encompass the direct emission from Hawking radiation, in-flight annihilation,
the final state of radiation, and positronium annihilation. Thorough
consideration is given to all these processes and their respective emission
fractions, followed by a precise calculation of the $\mathcal{D}$ factor for
observations directed towards the high-latitude Galactic contribution.
Furthermore, we integrate the flux originating from extragalactic sources, both
of which contribute to the measured isotropic flux. Through a comparative
analysis of data derived from previous CXB observations utilizing an Active
Galactic Nuclei (AGN) double power-law model, we establish the most stringent
constraints for PBHs, thereby excluding the possibility of PBHs constituting
the entire dark matter mass within the range of $2.5\times 10^{17}-3 \times
10^{17} $g.
