Deformation of trenches due to residual stresses in TiN may result in Cu voids forming especially at shrinking feature sizes of trenches and vias and introducing low-k dielectrics between Cu interconnects. The influence of residual stress therefore has been investigated in a parametric study using Finite Element analyses (FEA) to discover the correlation between the TiN stresses and failure occurrence at various geometric representations. FEA has been shown to allow effective BEoL (Back end of line) stress engineering leading to improved yield and reliability of next generation interconnect systems in minimum development time.

Increasing functionality in vehicles especially with respect to electromobility is demanding a decrease of energy consumption of numerous board systems. Clustering and miniaturization of sensor applications on the one hand are enabling new features and on the other they are minimizing energy needs for their operation. For modern vehicle driving stability or navigation systems e.g., the SCoM (stacked chip on MEMS) approach will provide the technology enabling shrinking of the sensors size on a high integration level by bringing intelligence directly to the sensor. To cope with the reliability requirements, restrictive qualification and zero defect strategies have been established by the automotive industry. Hence, introduction of innovative technologies in automotive applications must be accompanied by the demonstration of their reliability and safety. It is the goal of the RESTLES [1] project to eliminate parasitic sensor effects caused by process tolerances, intrinsic material stress, thermal mismatch, temperature and aging phenomena by transferring dedicated compensation models into the sensor and circuit design. To evaluate influences of thermo-mechanical stresses and strains, extensive simulations of the package behavior and non-destructive evaluation have been performed.

This paper investigates the thermo-mechanical reliability of inter-chip-vias (ICV) for 3D chip stacking after processing and under external thermal loads relevant for the envisaged field of application (mobile, automotive) by Finite Element simulation. First the materials are characterised by nano-indentation to determine elasto-plastic data. Finite Element simulations are used to reproduce these data and to extract local material properties like E-modulus and yield stress. Accumulated plastic strain is used as failure indicator under periodic thermal loading of an ICV. Geometrical, material and process-related parameters are varied to obtain first design guidelines for this new technology. The locations of stress and strain accumulation are given.

Knowledge of dynamical load behaviour is a basic requirement for life time optimised design of different products. This fact is especially relevant for smart electronic structures.Different non-contact working laser vibrometers (single-point and scanning) are used for vibration investigations and experimental modal analyses of such small structures. The results of this analyses show natural frequencies, vibration amplitudes and in case of scanning vibrometer also mode shapes. Based on this, structural modifications concerning a vibration optimisation can be derived.The measured results serve also as basis for numerical simulations and for FE-model validation.

A modular and parametric approach to FE-modelling is presented which allows rapid virtual prototyping for MEMS and other microelectronics packages with respect to some topical reliability issues: Thermal management and thermo-mechanical fatigue. Thereby the method of automatic model generation by modular parametric modelling is outlined and some examples featuring the required solution techniques are given. This simulation procedure forms part of a comprehensive design optimisation process in the field of predictive engineering.

The quality of mechanical modeling is of essential influence on the success of finite element analysis (FEA) and of subsequent studies of failure mechanisms. Missing knowledge about time and temperature dependent material behavior often leads to uncertainties in constitutive material description of rather complex structures like filled underfills or organic substrates. Micro deformation measurement methods help to overcome the problem by supplying displacement and strain fields comparable with FEA results. MicroDAC is an established versatile measurement tool for local and global deformation analyzes on thermally or mechanically stressed specimens. The paper presents the basics of the microDAC concept and different kinds of measurements on chip scale packages (CSP) and on flip chip assemblies to illustrate the application to integrated circuit (IC) packaging. A modified microDAC algorithm has been used to determine coefficients of thermal expansion (CTE) at small sized material samples and materials of anisotropic CTEs.

Lifetime and reliability of high-power diode laser bars are sensitively related to operating temperature, mounting stress, and solder electromigration. These three factors have been taken into account for the development of a new packaging technology for 1 cm laser bars of gallium arsenide. We examine the use of chemical-vapor-deposited (CVD) diamond as heatspreaders in order to reduce thermal resistance of a microchannel cooler for liquid cooling. We show that it is possible to perform hard soldering on a CVD-diamond with a new technique. Additionally, we present a controlled water cooling system fit to the flow characteristics of the cooler. It permits one to adjust the emission wavelength of the diode lasers by changing the water flux.

The authors developed and made use of the microDAC deformation measurement technique to determine strain fields on thermally stressed, cross sectioned FC and CSP specimens. The method allows one to resolve strain fields inside tiny structures like e.g. solder interconnects or conductive adhesive layers. It is based on comparison of digitized micrographs obtained from different object load states. Optical, SEM and laser scanning microscopy are applied for image capture. The paper presents results of strain analysis in interconnects of different flip chip configurations and chip scale package types e.g., global shear of outward bumps is almost completely suppressed in most flip chip cases by underfilling. Furthermore, bump deformation can be strongly influenced by the local appearance of glass fabrics in organic laminates used as board materials. A main demand on chip scale package reliability is the avoidance of too large thermal solder ball strains, which lead to material fatigue. Different packages with rigid and flex interposers tackle the stress compensation problem in a different way. A first attempt is made to compare some of them based on experimental strain and warpage measurements

The entire strain in experiments to determine the creep behavior of solder joint materials is a combination of elastic, inelastic, plastic and creep deformation. Most of the fatigue tests currently are performed using strain control. The separation of the creep fraction of the whole deformation, which is essential for life time prediction, is difficult in strain controlled experiments. Using load control instead it is relatively easy to extract the accumulated deformations relevant for solder joint damage /1, 2, 3/, Cyclic tests have to be used to determine the amount of creep deformation causing damage of the solder joint. The enveloping strain curve, which is showing primary, secondary and tertiary sections, respectively, like creep curves in static experiments are used for determination of irreversible strains during loading and dwell periods. Because the secondary time period is dominating in comparison to the primary and tertiary ones, the strain rate during secondary creep is used for material characterization under certain load and temperature conditions /4/. The relation between the accumulated creep strain per cycle calculated from the average secondary strain rate multiplied by the cycle duration and the performed cycles to failure usually is expressed in Coffin-Manson-type equations for solder materials.The characterization of the mechanical properties of solder materials, especially of stress-strain relations and fatigue resistance is performed using shear test equipment, because tile major loading of solder joints is consisting of shear straining. To evaluate quantitative relations a homogeneous distribution of shear stresses is necessary. To compare different shear tester geometries the stress distributions have been determined using Finite-Element models of Single-Lap-, Douhle-Lap-, Ring-and-Plug- and losipescu-Test and different solder compositions.

Summary form only given. For thermal management one has to distinguish between two categories: the heating of electronic components by their environment and heating due to power dissipation in the electronics. In the first case thermal insulation is essential for component protection. The authors show the limits of cooling mechanisms using liquids (liquid coolers and heat pipes) as well as electrothermal cooling. Furthermore, possibilities of passive cooling (heat spreading) are discussed. From the viewpoint of thermomechanical aspects, high temperature applications are complicated, because large temperature intervals drastically increase thermal mismatch in comparison to normal conditions. Effective cooling and equalizing temperature distributions are suitable to lower thermal mismatch by avoiding excessive temperature gradients. Thermomechanical principles like CTE matching or applying ductile intermediate layers, well known from low temperature packaging, become extremely more important. Some aspects of mechanical stresses on the acceleration of diffusion processes are discussed.

Much progress has been made in the simulation and verification of the thermo-mechanical behavior of plastic packages. On the other hand, until now there is a lack in the consideration of the scatter or uncertainty, respectively, of certain characteristics. A comparatively large scatter of local material properties or random geometrical imperfections can often be observed within the material compounds of electronic packages. The partial randomness of certain input parameters creates uncertainties in the finite element determination of mechanical quantities which are provided for thermo-mechanical reliability optimization and life time prediction. In the following the STOFEM stochastic finite element approach based on perturbation theory is applied as a part of the finite element simulation. It is used to find out some additional effects arising from uncertainties in the modeling, slightly varying parameters or probabilistic influences, respectively. In a second part of the paper, another approach to the consideration of random variations is discussed. It is based on the randomization of initially deterministic relations.

Packaging-induced strain is studied in high-power semiconductor lasers by a noninvasive optical technique. Fourier-transform photocurrent measurements with intentionally strained laser array devices for 808 nm emission reveal spectral shifts of optical transitions within the active region. These shifts by up to 10 meV serve as a measure for the strain status within the active layer of the devices and are compared with model calculations. For different packaging architectures we quantify the strain portion which is transmitted to the optically active region of the semiconductor device.

The design process of advanced electronic components and assemblies includes not only electrical aspects but also thermal and mechanical influences due to loadings which may occur throughout the whole lifetime. It is the aim of this paper to indicate the advantages of a combined numerical and experimental approach in order to determine the deformation behaviour and stress distributions as a base for reliability assessment in plastic packaging. The paper discusses how stress and deformation concentrations depend on special geometry and on material properties. Using the finite element method, it is often possible to investigate the thermal and thermo-mechanical behaviour of electronic assemblies using the same discretization. Computational series can be carried out by varying selected parameters, loading or boundary conditions. It is possible to determine sensitivities due to special inputs and to decide whether a modeled detail is essential or negligible. In addition, a special methodology also allows modification of the geometry without any topology changes. Wherever possible, computations should be combined with corresponding measurements. The authors prefer laser optical methods combined with careful metallographic preparation of objects in the micro region. The method is less time consuming as it takes advantage of current image processing techniques combined with numerical simulation tools which provide advanced reliability assessment.

Due to the demand for short signal running times the HF-technology requires high integration densities of active components. This results in considerable thermal problems additionally enlarged by the steady rising tact frequencies (up to 80 Gbits/s). Thus usual layouts for telecommunication purposes show hot spots with high temperature gradients. A consequence of local temperature elevations is a drastically reduced component life time. Thermally induced stresses caused by the high temperature gradients are a further failure source. In combination with more thermal cycles per time unit these mechanical strains and stresses cause a considerable reduction of life time, too. Numerical parameter studies of various board materials have shown, that a properly heat conducting and efficiently cooled board is a promising measure to reduce the component stresses by decreasing and equalizing the component temperatures. Using aluminium as the board material under the same conditions a lower operation temperature can be achieved with the effect of increasing the life time. Otherwise, the integration density can be increased to get better HF-properties. The dielectric is an anodic oxide (Eloxal). The thickness ratio between it and the aluminium substrate has been optimized numerically. The presentation deals with the choice of the new board material from thermal, thermomechanical and environmental viewpoints. A first demonstrator for the interconnection technology on anodically oxidized aluminium already exists and is presented

We introduce a new packaging concept for high power laser bars using Au(80)Sn(20)-solder on different heatsinks e.g. CVD-diamond and CuW. First the optimal thermal concept and design with the lowest possible thermal resistance is described. The thermal simulations were done by an inhouse made computer program based on FFT (Fast-Fourier-Transformation). The results of the 3D- and 2D-FEM-simulations for the thermomechanical design show a solution with low bonding stress. Design rules based on the discussion of these results including the technological limitations are described, which were used to define different alternative packaging concepts. The technological realization of these concepts is described and presented. The electro-optical characterization of such bonded laser bars gave first indications about maximum power, thermal resistance, bonding stress and reliability

The integration of electronic, acoustic, mechanical, thermal, optical and magnetic functions within one product is one of the great challenges for future microelectromechanical systems (MEMS) today. The development of advanced materials plays a key role for the design and development of new MEMS. Application fields and examples as well as future visions of microsystem technology are highlighted in this article. Additionally, some of the borders and requirements of today's MEMS design are also pointed out

Lifetime and reliability of high power diode laser bars (HPDLBs) are sensitively related to operating temperature, mounting stress and solder electromigration. These three factors have been taken into account for the development of a new packaging technology for 1 cm laser bars of gallium arsenide. We examine the use of chemical vapour deposited (CVD) diamond as heatspreaders in order to reduce thermal resistance of a microchannel cooler for liquid cooling. We show that it's possible to perform hard soldering on CVD-diamond with a new technique. Additionally, we present a controlled water cooling system fit to the flow characteristics of the cooler. It permits to adjust the emission wavelength of the diode lasers by changing the water flux