Tension-tension fatigue of copper thin films*1

Read, David T.

doi:10.1016/s0142-1123(97)00080-7

Cited by 150 publications

(53 citation statements)

References 13 publications

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“…The strength of this material is much higher than values of yield and ultimate strength for pure Cu in bulk. This finding is typical for fine grain size specimens and is consisting with prior studies for copper thin films (Read 1998;Sanders et al 1997;Legros et al 2000;Huang et al 2000). The experimentally modulus values of 103 GPa in loading and 107 GPa in unloading of 300 nm copper films were calculated from Fig.…”

Section: Sputtering Coppersupporting

confidence: 75%

Monotonic and fatigue testing of freestanding submicron thin beams application for MEMS

2007

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A freestanding submicron thin film specimen is designed and fabricated here to carry out a series of monotonic and fatigue testing. This freestanding beam was loaded by performing monotonic loading/unloading or closed-loop load controlled tension-tension fatigue experiments on it. Loading was applied using a piezoelectric actuator with 0.1 mu m resolution connected to the test specimen. Loads were measured by connected a capacitor load cell with a resolution of less than 0.1 mN. The modulus, yield stress and maximum stress of tested submicron thin films at room temperature were found from monotonic loading/unloading tests. The results of 300 nm copper thin films fatigue experiments demonstrated a trend of decreasing cycles to failure with increasing loading amplitude and increasing mean stress

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Section: Sputtering Coppersupporting

confidence: 75%

Monotonic and fatigue testing of freestanding submicron thin beams application for MEMS

2007

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“…Smaller specimens cannot be handled manually for gripping, and would require more elaborate specimen designs and test procedures, such as the silicon-framed tensile specimen [4] or use of other rigid support substrates [5].…”

Section: Figurementioning

confidence: 99%

US Army ARDEC Joint Fuze Technology Program (JFTP) task 2 report: quasi-static tensile tests of microfabricated electrodeposited (LIGA) Ni alloys

Liew¹,

Read²,

White³

et al. 2018

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The LIGA process (Lithographie, Galvanoformung, Abformung, or lithography, electrodeposition, shaping) offers the possibility of mass producing strong mesoscale (order of a few mm or less) metal components of nearly any planar shape. Multilayer deposition has been developed to create three-dimensional shapes. The overall objective of this multi-year project is to enable the use of the Johnson-Cook flow and fracture models for evaluation of structural elements made from two LIGA alloys of interest, by providing the material property data at the microscale needed to carry out structural analyses utilizing these models. This report documents the first milestone in the project, which is the measurement of the room-temperature tensile properties of two LIGA alloys of one commercial vendor's proprietary materials -one optimized for strength and the other for ductility, with nominal thicknesses 190 µm and 170 µm respectively -at strain rates 0.001/s and 1/s, utilizing four specimen geometries with gauge widths ranging from 75 µm to 700 µm. Test methods adapted to the scale of these materials were applied. Results, measurement uncertainties, and statistical variations for the ultimate tensile strength and apparent Young's modulus are quantified for all combinations of these material/geometry/rate variations. In addition, preliminary studies were conducted into the effects of low-temperature annealing on the materials' strength, and use of electron back scatter diffraction to observe the microstructure. Keywords Executive SummaryThis report presents the results of room-temperature tensile tests on microfabricated specimens of two LIGA Ni alloys of interest to the project sponsor and supplied by a commercial vendor. Microtensile specimens of the vendor's proprietary materials -"Alpha" and "C" -were supplied with nominal thicknesses of 190 µm and 170 µm, respectively, and of four different sizes with gauge widths ranging from 0.075 mm to 0.7 mm. The Alpha material is very strong, with consistent strength around 1900 MPa over several fabrication runs of the material. The C material has lower strength -around 600 MPa -and is more ductile. Both materials were tested at strain rates 0.001/s and 1 /s; Figure 1 shows typical engineering stress-strain curves. Small size-and rate effects were found in both materials in the ranges tested. Pin-loaded tensile specimens were used with general purpose tensile test apparatus consistent with the scale of the specimens. This approach succeeded in measurements of the strength and ductility. However, attempts to measure the Young's modulus were not fully successful because of large experimental uncertainties and a microplasticity phenomenon similar to that reported as material instability in the previous literature on LIGA Ni materials. Figure 1. shows stressstrain curves for 2 nominal specimens, one of each material, tested at the two strain rates. The Alpha material clearly exhibits much higher strength and lower ductility than the C material.(a) (b) Figure 1. Engineering stress-...

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“…For instance, copper (Cu) thin films exhibited a lower Young's modulus but higher yield and ultimate tensile strengths than their bulk counterparts under cyclic tensile loading. 19) Similarly, persistent slip bands (PSBs) were prevalent in bulk Cu and gold (Au) samples upon deformation whereas they were absent in Cu and Au thin wires. Specifically, the existence of PSBs and the extrusions on these PSBs lead to local increases in the stress field, and thereby formation of several crack initiation sites.…”

Section: )mentioning

confidence: 99%