Hermetic packages

Materials used for substrates can be broadly classified into ceramics and metals. Gommonly used ceramics, ie, alumina, aluminum nitride, and beryUia, can be easily incorporated into a hermetic package, ie, a package permanently sealed by fusion or soldering to prevent the transmission of moisture, air, and other gases. 

A case provides mechanical support and protection for the devices, interconnects, and substrate mounted in it it also helps to dissipate heat during component operation and offers protection to the contents of the package from environmental stresses, contaminants, and, in the case of hermetic packages, moisture. 

The DLC active part is made in most of the case of two identical electrodes. There is a spacer between the electrodes, called separator, whose function is to provide the electronic insulation between the electrodes, while ensuring the ionic conduction by allowing the ions to move through thanks to its porosity. The active part is impregnated with an electrolyte made of a solvent containing a disassociated salt and the unit s seated in a hermetic package [2],... 

Multiple butter fat products, including butter oils, anhydrous butter fat, butter fat-vegetable oil blends, and fractionated butter fats, are manufactured around the world today. In the past, butter fat in the form of butter was the primary preservation technique. Today, the preferred preservation method involves the processing of butter fat to the anhydrous butter oil state, then hermetically packaging under nitrogen to substantially increase the shelf life and reduce the incidence of degradation. 

Electronic components of neural prostheses must survive and function under challenging conditions. They are exposed not only to the corrosive effects of saline fluids but also to natural foreign-body reactions. Hermetic packaging can delay the attack but it is not practical to seal the whole unit. The key to survival and reliable performance of neural implants is the selection of insulating materials that will neither harm the body nor be harmed by it. 

In a non-hermetic package, the primary moisture barrier is typically a thin, (<0.1 micron) inorganic passivation layer of silicon dioxide or silicon nitride. However, passivation layers cannot withstand physical handling and they are not resistant to saline exposure. Additional protection is needed in the form of organic polymer coatings. 

All have stimulated interest In the properties and performance of silicone gels. In addition, in 1986 the IEEE Computer Packaging Committee set up a special task force chaired by Jack W. Balde to investigate the possibility of gaining military approval to use gels for protecting non-hermetic packages. 

The comparison between the reliability of hermetic and plastic packaging is perhaps not as clear cut as suggested above, the hermetic package cavities are not always as clean and dry as required and often of dubious hermeticity, also plastic packaging materials of low water permeability and high purity have been developed. In addition, plastic packages offer improved performance against other forms of reliability hazard, e.g. mechanical shock, because of their monolithic construction. 

Hermetic packages are expensive, but the total costs associated with passivation of sensitive microsystems within nonhermetic packages may be even more expensive. The same applies to EMI problems, which are prevented by hermetic metal packages. 

Chemical Requirements. The pottant must be stable that is, chemically resistant to oxidation and hydrolysis unless protected in a hermetic package, to reduction by metals, and to outgassing of dissolved gases or liquids or decomposition products under normal operating conditions of -itO°C to +90°C for 20 years. The need for chemical stability is especially stringent when a lower cost non-hermetic design is used. Even when a hermetic package is... 

Dietz RL, Winder L. New die attach material for hermetic packaging, Proc. Mfg. Eng. EMTAS Conf. Phoenix, AZ EE83-145 1983. 

Iwami C, Licari JJ, Nakagawa C. New Adhesive requirements for multichip modules, Proc. 5th Inti. SAMPE Electronic Materials and Processes Conf. Los Angeles Jun 1991. Harper PR. Thermoplastic die attach for hermetic packaging. Inti. J. Microelectronics and Electronic Packaging. 4th Quarter 1994 17(4). 

In dry-heat sterilization, the parts are exposed for 2-3 hours at 165°C-170 °C. Dry-heat exposure is the least effective sterilization method and most likely to degrade materials and electronic devices. Although adhesives may have been cured at 165 °C prior to hermetic packaging, the additional temperature exposure within the sealed package can result in further outgassing of moisture and corrosive volatiles causing electrical failures. Outgassing is worse if the adhesive had been cured at a temperature below 165 °C. 

Dietz, R. L., and Winder, L.,New Die Attach MaterialFor Hermetic Packaging, Proc. Mfg. EngEMTASConf., EE83-145, Phoenix, AZ(1983)... 

Harper, P. R., Thermoplastic Die Attach for Hermetic Packaging, Inti J. Microelectronics and Electronic Packaging, 17(4) (4 Quarter 1994)... 

Chiao M, Lin L (2006) Device-level hermetic packaging of microiesonators by RTF aluminum-to-nitride bonding. J Microelectromech Syst 15(3) 515-522... 

W H. Liederbach and H. Stetson, Laminates, New Approach to Ceramic Metal Manufacture Part II Hermetic Package for Quartz Crystal Oscillators, Am. Ceram. Soc. Bull., 40 [9] 584 (1961). 

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