Home/Technical Glossary/Cap Welding Cap Welding Cap welding is the common term used for the projection spot welding of the caps (or lids) on electronic packages. The process seems to be fairly straightforward: place components in a metal package and seal. It is very important, however, to prevent moisture and oxygen ingress to the package during sealing, which, over time, will damage the sensitive electronic components housed within. For more information on cap welding and the equipment and processes used, read our blog post Electronic Package Sealing? Projection Cap Welding Technique Saves $$$.