PACKAGING HIGH DENSITY CAPACITIVE MICRO-MACHINED ULTRASONIC TRANSDUCERS (CMUT) SENSOR ARRAYS USING HYPERBGA® TECHNOLOGY – PART II
Authors: Robert Wodnicki, Charles G. Woychik, Kai Thomenius; Glen Thomas, Irv Memis, Ulises Penaherrera, Barry Bonitz, Todd Davies Company: GE Global Research; Endicott Interconnect Technologies, Inc. Date Published: 10/24/2010
Abstract: Piezoelectric transducers have long dominated ultrasonic transducer technology, but capacitive micro-machined ultrasound transducers (cMUTs) have emerged as an alternative. Features of cMUT devices are wide bandwidth, ability to use silicon MEMS fabrication methods to produce large arrays and potential for integration with supporting electronic circuits. cMUT technology can potentially produce the type of integrated sensor array to enable advanced 3-D imaging. A major challenge to achieve this goal is the packaging of a large array of cMUT die. To accomplish this we use a high density Teflon interposer called HyperBGA® technology, produced by Endicott Interconnect (EI) to design a modular package in which the sensor cMUT array is on the topside and the supporting electronics on the backside. A trenched cMUT device having a pillar is flip chip attached to the HyperBGA substrate with a die-to-die spacing less than 100 um. Each cMUT device has 256 I/O pads with a pitch of 185 um. The packaging challenges to design and build this type of advanced sensor array will be presented.