Tham khảo tài liệu 'an introduction to mems engineering - nadim maluf and kirt williams part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 240 Packaging and Reliability Considerations for MEMS Packaging solutions for harsh environments namely those found in heavy industries and aerospace can be complex and costly. The custom requirements of the application coupled with the lack of high-volume market demand have turned packaging for harsh environments into a niche art. One particularly interesting design is the metal packaging of media-isolated pressure sensors for operation in heavy-industrial environments. The design immerses the silicon pressure sensor within an oil-filled stainless steel cavity that is sealed with a thin stainless steel diaphragm. The silicon pressure sensor measures pressure transmitted via the steel diaphragm and through the oil. The robust steel package offers hermetic protection of the sensing die and the wire bonds against adverse environmental conditions see Figure . Each stainless steel package is individually machined to produce a cavity. The die is attached to a standard header with glass-fired pins and wire bonded. This header is resistance welded to the stainless-steel package. Arc welding of a stainless-steel diaphragm seals the top side of the assembly. Oil filling of the cavity occurs through a small port at the bottom that is later plugged and sealed by welding a ball. Molded Plastic Packaging Unlike metal or ceramic packages molded plastic packages are not hermetic. Yet they dominate in the packaging of integrated circuits because they are cost-effective solutions costing on average a few pennies or less per electrical pin . Advances in plastic packaging have further improved reliability to high levels. Today s failure rates in plastic-packaged logic and linear integrated circuits are less than one failure in every ten billion hours of operation 23 . There are two general approaches to plastic packaging post molding and premolding see Figure . In the first approach the plastic housing is molded after the die is attached to a lead frame a supporting metal .
