Mechanical property evaluation and failure analysis of cantilevered LIGA nickel microposts

Lyndon S. Stephens, Kevin W. Kelly, Seshu Simhadri, Andy B. McCandless, E. I. Meletis

Research output: Contribution to journalArticlepeer-review

62 Scopus citations

Abstract

An experimental apparatus has been built to measure the elastic modulus and bending strength (modulus of rupture) of LIGA nickel posts. The apparatus uses the static cantilever beam bending approach to measure mechanical properties in a direction parallel to the growth direction. Experimental results are presented for two sets of largely identical posts constructed using an overplating method. One set was electroplated using a Watts bath, and the other set was electroplated using a sulfamate bath. For the Watts bath, the measured modulus of elasticity was slightly lower than that of bulk nickel (182 GPa), while, for the sulfamate bath, it was approximately half (93 GPa). The strength properties of the two sets of posts also differ dramatically. Microhardness measurements, Focused Ion Beam images of grain structure, and scanning electron microscopy (SEM) micrographs of failure regions are used to further characterize and explain the differences in the results. This integrated testing approach yields a consistent set of data regarding material properties, grain size/structure and failure mechanisms. Potential sources of experimental error are also identified and improvements in experiment design are suggested to reduce these errors.

Original languageEnglish
Pages (from-to)347-359
Number of pages13
JournalJournal of Microelectromechanical Systems
Volume10
Issue number3
DOIs
StatePublished - Sep 2001

Bibliographical note

Funding Information:
Manuscript received July 26, 2000; revised January 26, 2001. This work was supported by the Defense Advanced Research Project Agency (DARPA), the State of Louisiana through the Board of Regents (Industrial Ties Program) and indirectly through the Center for Advanced Microstructures and Devices (CAMD), Baton Rouge, and Exxon Chemical Americas. Subject Editor E. Obermeier.

Keywords

  • Failure analysis
  • High-aspect ratio microstructures (HARMs)
  • LIGA
  • Materials testing
  • Strength

ASJC Scopus subject areas

  • Mechanical Engineering
  • Electrical and Electronic Engineering

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