3-Sigma Research (United States)

ABSTRACT Functionality of many types of microelectronic, optoelectronic, medical, and micro- and nanomachine devices depends on protection afforded by a hermetically sealed enclosure. But certain volatiles in enclosure headspace can create a unique, harsh mini-environment for sealed devices. External thermal, mechanical, or chemically harsh environments of post-seal testing or field service can induce, or aggravate, already harsh internal mini-environments. Depending on type of device, vapors, adsorbates, or condensates of moisture, hydrogen, oxygen, hydrocarbons, ammonia, and other volatiles can deteriorate or destroy device function. Devices can be susceptible to failure mechanisms such as corrosion, electrical leakage or instability, dendritic growth, fogging, stiction, jammed moving parts, etc. caused by these species. In vacuum-sealed enclosures minuscule amounts of any volatile deteriorate vacuum quality and degrade devices that depend on ultralow headspace gas pressure. Undesired volatiles can be impurities in blanket gas used during seal. They can volatilize from materials within the enclosure during post-seal thermal excursions. They can enter through leak paths caused by poor sealing processes or post-seal thermal or mechanical stresses of harsh environments that compromise seal integrity. This paper identifies the types and sources of volatiles that threaten device function, summarizes failure mechanisms that volatiles can cause, reviews data from mass spectrometric analysis of headspace gas composition, and discusses material and process considerations for controlling headspace gas composition.