Inkjet printing technology for increasing the I/O density of 3D TSV interposers
Journal article, 2017

Interposers with through-silicon vias (TSVs) play a key role in the three-dimensional integration and packaging of integrated circuits and microelectromechanical systems. In the current practice of fabricating interposers, solder balls are placed next to the vias; however, this approach requires a large foot print for the input/output (I/O) connections. Therefore, in this study, we investigate the possibility of placing the solder balls directly on top of the vias, thereby enabling a smaller pitch between the solder balls and an increased density of the I/O connections. To reach this goal, inkjet printing (that is, piezo and super inkjet) was used to successfully fill and planarize hollow metal TSVs with a dielectric polymer. The under bump metallization (UBM) pads were also successfully printed with inkjet technology on top of the polymer-filled vias, using either Ag or Au inks. The reliability of the TSV interposers was investigated by a temperature cycling stress test (-40 degrees C to + 125 degrees C). The stress test showed no impact on DC resistance of the TSVs; however, shrinkage and delamination of the polymer was observed, along with some micro-cracks in the UBM pads. For proof of concept, SnAgCu-based solder balls were jetted on the UBM pads.

Author

Behnam Khorramdel

Tampere University of Technology

Jessica Liljeholm

Silex Microsystems AB

Royal Institute of Technology (KTH)

Mika-Matti Laurila

Tampere University of Technology

Toni Lammi

Tampere University of Technology

Gustaf Mårtensson

Mycronic AB

Chalmers, Microtechnology and Nanoscience (MC2), Electronics Material and Systems Laboratory

Thorbjoern Ebefors

Silex Microsystems AB

Frank Niklaus

Royal Institute of Technology (KTH)

Matti Maentysalo

Tampere University of Technology

MICROSYSTEMS & NANOENGINEERING

2055-7434 (ISSN)

Vol. 3 Article no. UNSP 17002 -

Subject Categories

Nano Technology

DOI

10.1038/micronano.2017.2

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1/8/2019 8