Title :
Mechanical property evaluation and failure analysis of cantilevered LIGA nickel microposts
Author :
Stephens, Lyndon S. ; Kelly, Kevin W. ; Simhadri, Seshu ; McCandless, Andy B. ; Meletis, E.I.
Author_Institution :
Dept. of Mech. Eng., Kentucky Univ., Lexington, KY, USA
fDate :
9/1/2001 12:00:00 AM
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 (FIB) 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
Keywords :
LIGA; bending strength; elastic moduli measurement; electroplated coatings; failure (mechanical); failure analysis; focused ion beam technology; grain size; materials testing; microhardness; micromechanical devices; nickel; scanning electron microscopy; yield strength; FIB images; HARMs; MEMS; Ni; SEM micrographs; Watts bath; bending strength; cantilevered LIGA nickel microposts; elastic modulus; electroplating; experimental error sources; failure analysis; failure mechanisms; failure regions; focused ion beam images; grain size; grain structure; high-aspect ratio microstructures; integrated testing approach; material properties; mechanical property evaluation; microhardness measurements; modulus of rupture; overplating method; scanning electron microscopy; static cantilever beam bending approach; strength properties; sulfamate bath; Elasticity; Electron beams; Failure analysis; Focusing; Ion beams; Mechanical factors; Mechanical variables measurement; Nickel; Scanning electron microscopy; Structural beams;
Journal_Title :
Microelectromechanical Systems, Journal of
