Microstructural and mechanical properties investigation of electrodeposited and annealed LIGA nickel structures

Lithographic, Galvanoformung, Abformung (LIGA) component fabrication is a process in which structural material is deposited into a patterned polymethyl-methacrylate (PMMA) mold realized through deep X-ray lithography. The process permits fabrication of metal microelectrome chanical systems (MEMS) components with representative dimensions that range from a few microns to several millimeters. This investigation characterizes the microstructure and mechanical properties of LIGA-fabricated nickel (LIGA Ni), electrodeposited using Watts bath and sulfamate bath chemistries. As a prelude to studying high-temperature joining processes in LIGA Ni components, an annealing investigation was conducted on samples fabricated from both bath chemistries. Mechanical properties and microstructural analyses on as-deposited and annealed samples were conducted using a mini servohydraulic load frame and the electron backscatter diffraction (EBSD) microtexture measurement technique. The deposits were found to have fine-grain, highly textured microstructures oriented with an acicular or columnar morphology relative to the plating direction. Previously uncharacterized, anomalous, local spatial variations in the crystallographic texture of the as-deposited microstructures were identified by EBSD analyses. Microstructural evolution during annealing seemed to follow a recovery, recrystallization, rapid grain-growth microstructural-evolution mechanism in LIGA Ni deposited from the Sulfamate bath chemistry and simply a recovery and grain-growth microstructural-evolution mechanism in LIGA Ni deposited from the Watts bath chemistry. The evolution of microstructure in the annealed samples corresponded with a dramatic drop in their strength and determined the limiting diffusion-bonding temperature for LIGA Ni components.

[1]  F. Ericson,et al.  Young's Modulus, Yield Strength and Fracture Strength of Microelements Determined by Tensile Testing , 1998 .

[2]  P. McNally,et al.  A comparative study of Pd/Sn/Au, Au/Ge/Au/Ni/Au, Au-Ge/Ni and Ni/Au-Ge/Ni ohmic contacts to n-GaAs , 1998 .

[3]  A. Marder,et al.  Microstructural characterization and hardness of electrodeposited nickel coatings from a sulphamate bath , 1998 .

[4]  Mukul Kumar,et al.  Electron Backscatter Diffraction in Materials Science , 2000 .

[5]  Volker Saile,et al.  Research, development and manufacturing plans at CAMD , 1997 .

[6]  Thomas Edward Buchheit,et al.  Materials science of microelectromechanical systems (MEMS) devices IV , 2002 .

[7]  Walter Bacher,et al.  The LIGA technique and its potential for microsystems-a survey , 1995, IEEE Trans. Ind. Electron..

[8]  R. Valiev,et al.  On the grain boundary statistics in metals and alloys susceptible to annealing twinning , 1994 .

[9]  R. Valiev,et al.  Modelling of grain boundary misorientation spectrum in polycrystals with crystallographic texture , 1992 .

[10]  N. Spyrellis,et al.  Nickel plating by pulse electrolysis: textural and microstructural modifications due to adsorption/desorption phenomena , 1990 .

[11]  G. Maurin,et al.  Inhibition and nickel electrocrystallization , 1979 .

[12]  P. King,et al.  On annealing twins and CSL distributions in F.C.C. polycrystals , 1992 .

[13]  H. E. Boyer,et al.  Metals handbook; desk edition , 1985 .

[14]  R Weil,et al.  The Structures of Electrodeposits and the Properties that Depend on Them , 1989 .

[15]  C. B. Nielsen,et al.  On texture formation of nickel electrodeposits , 1997 .

[16]  W. H. Safranek.  The properties of electrodeposited metals and alloys;: A handbook , 1974 .

[17]  J. Mohr,et al.  LIGA : A technology for fabricating microstructures and microsystems , 1998 .

[18]  S. Majumdar,et al.  Creep cavitation and grain boundary structure in type 304 stainless steel , 1986 .

[19]  J. W. Dini,et al.  Electrodeposition: The Materials Science of Coatings and Substrates , 1993 .

[20]  Daniel T. Schwartz,et al.  High-rate through-mold electrodeposition of thick (>200 /spl mu/m) NiFe MEMS components with uniform composition , 1999 .

[21]  Thomas Edward Buchheit,et al.  Description of a micro-mechanical testing system , 1997 .