Plastic Hermetic Packages for MEMS?

The sealed hermetic package is over 100 years old if we include cathode ray and vacuum tubes. While the package has changed, the idea of making a near-perfect gas-tight enclosure has remained constant. The metal and ceramic full hermetic package may be required for applications that cannot use the non-hermetic plastic package, but is there an intermediate package choice? During the last few years, the electronic packaging industry has sought to develop the Near-Hermetic Package (NHP), a design that is “good enough” and “cheap enough” to satisfy some special devices like MEMS. This paper will describe work with Liquid Crystal Polymer (LCP) injection-molded enclosures that are targeting MEMS and some optical device applications. The work involves sealing lids and chip carriers with laser energy. The package design creates a cavity type enclosure that can provide the “free space” necessary for mechanical motion found in some MEMS devices. We will also briefly describe getters (contaminant scavengers) and fluorinated parylene coatings also useful for MEMS. But the work has had a surprising result. The plastic package has repeatedly passed hermeticity; helium leak test. Author contact: K Gilleo, e-mail: [email protected].