In order to introduce new bonding methods in the area of electronic packaging a theoretical analysis was conducted, which should give substantial information about the potential of reactive multilayer systems (rms) to create sufficient local heat for joining processes between silicon chips and ceramic substrates. For this purpose, thermal CFD (computational fluid dynamics) simulations have been carried out to simulate the temperature profile of the bonding zone during and after the reaction of the rms. This thermal analysis considers two different configurations. The first configuration consists of a silicon chip that is bonded to an LTCC-substrate (Low Temperature Co-fired Ceramics) using a bonding layer that contains an rms and a solder preform. The reaction propagation speed of the reactive multilayer was set to a value of 1 m/s, in order to partially melt a solder preform underneath a silicon chip. The second configuration, which consists only of the LTCC-substrate and the rms, was chosen to study the differences between the thermal outputs of the two arrangements. The analysis of the CFD simulations was particularly focused on interpretations of the temperature and liquid fraction contours. The CFD thermal simulation analysis conducted contains a melting/solidification model which can track the molten/solid state of the solder in addition to modelling the influence of latent heat. To provide information for the design of a test-substrate for experimental investigations, the real behaviour of Pt-100 temperature probes on the LTCC-substrate was simulated, in order to monitor an actual bonding in the experiment. All simulations were carried out using the ANSYS Fluent software.

The time-independent behaviour of SnPb37, SnAg3.5 and SnAg4Cu0.5 has been investigated on flip chip solder joints. The test specimen consisted of two silicon chips (3.3 mm in square) bonded by 4 flip chip joints (one at each corner). The Dresden University Micro Shear Tester has been used for the experiments with this type of specimen. In contrast to similar set-ups, it is actively compensated for its finite stiffness. Therefore, it is able to record force displacement hysteresis with a resolution of better than 1 mN and 20 nm, respectively. Based on these measurements, the parameters of the constitutive equations have been evaluated by FEM analysis. This way, the complex stress state within the sample during the test has been considered precisely providing for high accuracy of the parameter extracted. As a typical application, a three point bending experiment has been simulated by FEM applying different constitutive models for the solder material. Comparing the results, it becomes clear: All the three ingredients, i.e., the elastic, the creep, and the time-independent plastic data, are required in the model. Otherwise it would be incomplete and hence insufficient for assisting in the design of today's electronics packages even with respect to the most frequent load cases.

The paper describes the strategies of characterizing the creep behaviour of SnAg-and SnAgCu-solders through experiments on bulk specimens and on very tiny solder joints. The characteristic behaviour of these different volumes will be explained and rationalized by metallurgical considerations about the specifics of solidification in very small volumes.

A modern approach to determine material data of solder alloys such as SnAg and SnAgCu is to measure the mechanical behaviour direct on a CSP/BGA solder connection. Advantages of that technique of measurement on industrial manufactured solder bumps are the considerations of miniaturized volumes and the material diffusion from connection pad into the alloy during reflow soldering process. Compared to the tensile test the shear experiment differs in the way of initiation the force load into the solder alloy. The shear force load inducts a multiaxial state of stress. This is the reason for the confrontation with a higher effort into the conversion procedure to determine specific coefficients for the material law. In several publications creep data were published based on shear force load measurements and applied cylinder model to convert primary data into equivalent values. In practice, the specimen bumps may have been different in their shape, depending on pad geometry, solder volume and weight of electronic component. How does the shape of solder joints influence the creep behaviour? A form parameter has been introduced to be able to describe a wide range of solder bump shapes. Every bump shape from barrel to hyperbolic can now be regarded. The form parameter also takes place in the conversion of experimental data into equivalent data. The determined creep material laws, based on the improved analytic model, describe the deformation behaviour of solder joints more accurately, than the commonly assigned creep laws using the pure cylinder model. The shape effect is shown on a FEM analysis of the experimental setup of creep measurements on shape varied Sn96.5Ag3.5 solder bumps. In general, during FEM based material modelling the coefficients of the material laws need to be stepwise changed until the right behaviour occurs. These iterations can stretch over a long time. The improved analytical model shows the potential to shorten the coefficient determination of material laws

The paper presents extended creep properties of eutectic SnAg3.8Cu0.7 solder using dog bone shaped tensile specimen to extend the data for the Alpha-Omega Model. The tensile test machine was carefully modified with respect of solder material requirements in terms of stress free specimen mounting and assurances of high stable stress conditions. Furthermore the tensile tester is able to measure the deformation of the specimen directly on the specimen, which allows more precise tests and more independence from temperature and stress dependent tester parts like the clamping and the rods. The tests were performed in three temperatures: 25degC, 75degC and 125degC and three different stresses at each temperature.

This paper discusses the requirements for achieving adequate modelling of the mechanical behaviour of copper interconnect structures in electronic assemblies. In this context it focuses on an experimental approach to characterise the mechanical behaviour of representative copper specimens. For this purpose the general constitutive behaviour of pure copper will be discussed, in doing so covering the specifics of elastic response, the onset of plastic flow with respect to microstructure, as well as load history, and the resulting cyclic elastic-plastic behaviour. The discussion regarding an appropriate experimental methodology starts with considerations about specific deformations of representative thin stripe specimens during a standard tensile test. In the second part this discussion is developed into design ideas for appropriate experimental instrumentation, which enables one to determine the required properties of the representative specimens.