Kein Folientitel

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Size Effects and Mechanical Properties of Thin
Copper Foils
University of Applied Sciences Augsburg,
Germany ETH Zürich, Switzerland
J. Villain, Ch. Weippert G. Simons , J. Dual
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Aim of the work

• Thermo mechanical simulations are necessary to
  understand the
• reliability of micro-electronic devices or
  micro-electromechanical systems.
• For this investigations the material parameters
  as ultimate tensile strength,
• elongation at rupture have to be determined for
  tests specimens which have
• the same geometry as parts inside the devices.
  The preparation and the
• measurement of very small test specimens is
  expensive.
• Question Could we use material parameters which
  were determined
• with macro specimens - dimensions mm or cm?
• Answer
• The first step is to analyse a size-effect.
• If no size-effect could be seen, low cost large
  specimens could be used.
• If a size-effect occurs, micro tests have to be
  developed or mathematical models have to be
  built up to characterise the size-effect.

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Size-effects known in the literature The smaller
the specimens the higher the strength and the
lower the ductility, no size effect for Youngs
modulus. gtgtgtgt This tendency could be observed for
several materials as nickel and polysilicon. We
are testing copper-foils at room temperature
under same conditions (thickness 10µm, 20 µm, 34
µm, 50 µm, 100 µm, 250 mm same relation of
thickness, width and gauge length texture
hardness strain velocity).
Tensile Module
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Stress-Strain Diagram (10 µm, 34 µm)
Surface of a 20 µm Specimen near
Fracture (Source S.I.S., Rastersonden- und
Sensor-messtechnik GmbH, Herzogenrath)
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Results of the Tensile Tests
A strong decrese of the elongation at rupture and
a smooth increase of the ultimate tensile
strength with lower thickness of the copper foils