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J. Villain*, Ch. Weippert* G. Simons **, J. Dual**

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**. Aim of the work. Thermo mechanical simulations are necessary to understand the

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J. Villain*, Ch. Weippert* G. Simons **, J. Dual**

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  1. 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**

  2. 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.

  3. Size-effects known in the literature The smaller the specimens the higher the strength and the lower the ductility, no size effect for Young`s modulus. >>>> 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

  4. 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)

  5. 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

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