Hermeticity, gas permeation, surface desorption and hydrogen diffusion must all be considered as well. To achieve hermeticity, it is important to achieve a void-free solder bond. One source of voids comes from trapped gas that occurs during the fabrication process of the package and components. Pressure variation helps reduce and practically eliminate voids caused by trapped gas. Having the ability to reach both extremely high pressures and low pressures throughout the thermal processing of a package sealing process is vital to achieving a good hermetic seal.