Determination of Mechanical Material Properties of Joining Materials, in particular Microelectronic Solders

During fabrication of modem microelectronic components miscellaneous solder materials are used. In order to ensure high quality of the manufacturing process as well as optimal reliability of the component and, in particular, of the solder joints it is most important to know the properties of all the materials involved. Of special interest are Young´s modulus, yield stress, and hardness. Moreover, a complete stress-strain curve is most desirable during a Finite Element Analysis (FEA) when the objective is to study the state of stress developing in a product. Clearly, miniaturization of modem products is accompanied by using very small amounts of matter and the material properties of these may be very different from those of large components. For this reason miniature tests should be used for an adequate measurement of the mechanical properties of solders and other (micro-) materials. In this paper we present and discuss two such tests, namely mini-uniaxial-tension and nanoindenter experiments. In the tensile test where the axial loading is prescribed the resulting extension of the miniature specimen is recorded. This information can then directly be used to obtain stress-strain-curves characteristic of relatively small amounts of matter. These will then be further analyzed: A Ramberg-Osgood-type relation between stress and strain is assumed and the corresponding parameters are fitted to the experimental data using multi- parameter optimization techniques. Moreover, nanoindenta-tion allows examining material properties within very small regions, i.e., it is a very local examination technique. primarily a nanoindentation experiment results in load vs. indentation-depth data.