There are two methods of lid-seal, depending on the build-standard of the hybrid

For metal packs, a metal lid is seam-welded to the package in a dry-nitrogen atmosphere. The picture shows the process taking place in a glove box where two copper rollers deliver high current pulses, welding the lid in place.

For ceramic packs, a ceramic cavity lid is affixed to the substrate using an epoxy mat. Again the sealing process takes place in a dry-nitrogen atmosphere. Chip-on-board designs are protected by localised application of a silicone bond protection, usually with an overall epoxy coating.

Packages

Some examples include…
Mil spec chip and wire Seam-sealed metal packs
MIL spec chip and wire Epoxy-sealed ceramic packs
Industrial spec chip and wire Silicone bond protected, epoxy coated
Industrial and commercial Epoxy coated
Surface mounted Epoxy coated
Format Dual-in-line
Single-in-line
Double-sided, mixed build customised format to suit the application