What is a hermetic seal in ultrasonic welding?

A hermetic seal in ultrasonic welding refers to a seal that is airtight and does not allow any air, gas or liquid to pass through. In ultrasonic welding, hermetic seals are achieved by applying high-frequency ultrasonic vibrations and pressure to the materials being welded, causing them to melt and fuse together. This type of seal is often used in applications where a barrier is required to prevent the passage of gases or liquids, such as in the medical or electronic industries. A hermetic seal can be critical in protecting the contents of a package or enclosure from moisture, air, and other environmental factors that could cause degradation or contamination.