In a recent blog, we mentioned using projections as “energy directors” to achieve weld joints at specific, pre-defined locations. Ring projections - also known as annular projections - are commonly utilized in the electronic packaging industry to achieve hermetically sealed electronic packages, for transistor outline (TO) packages and, more recently, rectangular packages. Following are some tips for successful design of these ring projections and possible solutions to help you overcome less-than-perfect designs.
If you read my recent blog on heat balance, you know that there are five different techniques that can be used to balance weld heat that don’t involve making changes to materials or part design. And at the end of the blog I mentioned that if you’re still having difficulty after trying all five of the techniques, you may want to consider adding projections to one of the parts.
Electronic package sealing is a tricky process. It may seem straightforward: place components in a metal package and seal, generally using projection spot welding (aka cap welding). 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. This zero-moisture requirement is most commonly achieved by heating the package in an oven and then moving it into a glove box backfilled with nitrogen, removing both moisture and oxygen. With increasing frequency, however, manufacturers are starting to use xenon to backfill the packages. Why? Xenon is a large molecule with good thermal properties, and, because the outer valence shell contains eight electrons, producing a stable, minimum energy configuration in which the outer electrons are tightly bound, it is inert to most common chemical reactions, including combustion.