title: Packaging and modular assembly of large-area and fine-pitch 2-D ultrasonic transducer arrays.
abstract: A promising transducer architecture for largearea arrays employs 2-D capacitive micromachined ultrasound transducer (CMUT) devices with backside trench-frame pillar interconnects. Reconfigurable array (RA) application-specified integrated circuits (ASICs) can provide efficient interfacing between these high-element-count transducer arrays and standard ultrasound systems. Standard electronic assembly techniques such as flip-chip and ball grid array (BGA) attachment, along with organic laminate substrate carriers, can be leveraged to create large-area arrays composed of tiled modules of CMUT chips and interface ASICs. A large-scale, fully populated and integrated 2-D CMUT array with 32 by 192 elements was developed and demonstrates the feasibility of these techniques to yield future large-area arrays. This study demonstrates a flexible and reliable integration approach by successfully combining a simple under-bump metallization (UBM) process and a stacked CMUT/interposer/ASIC module architecture. The results show high shear strength of the UBM (26.5 g for 70-μm balls), high interconnect yield, and excellent CMUT resonance uniformity (s = 0.02 MHz). A multi-row linear array was constructed using the new CMUT/interposer/ASIC process using acoustically active trench-frame CMUT devices and mechanical/ nonfunctional Si backside ASICs. Imaging results with the completed probe assembly demonstrate a functioning device based on the modular assembly architecture.
authors.forename: Der-Song
authors.initials: DS
authors.lastname: Lin
authors.forename: Robert
authors.initials: R
authors.lastname: Wodnicki
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Zhuang
authors.forename: Charles
authors.initials: C
authors.lastname: Woychik
authors.forename: Kai E
authors.initials: KE
authors.lastname: Thomenius
authors.forename: Rayette A
authors.initials: RA
authors.lastname: Fisher
authors.forename: David M
authors.initials: DM
authors.lastname: Mills
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Byun
authors.forename: William
authors.initials: W
authors.lastname: Burdick
authors.forename: Pierre
authors.initials: P
authors.lastname: Khuri-Yakub
authors.forename: Barry
authors.initials: B
authors.lastname: Bonitz
authors.forename: Todd
authors.initials: T
authors.lastname: Davies
authors.forename: Glen
authors.initials: G
authors.lastname: Thomas
authors.forename: Bernd
authors.initials: B
authors.lastname: Otto
authors.forename: Michael
authors.initials: M
authors.lastname: Töpper
authors.forename: Thomas
authors.initials: T
authors.lastname: Fritzsch
authors.forename: Oswin
authors.initials: O
authors.lastname: Ehrmann
mesh_terms: D004867:Equipment Design; D019047:Phantoms, Imaging; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation*