The Digital Image Correlation (DIC) technique is a widely used contactless method for measuring deformation and strain fields based on images obtained during an experiment. This study employs the DIC technique to measure the deformation and strain fields caused by a thermal load on non-embedded cross-sections of Fan-Out Wafer Level Packages (FO-WLP) mounted on Printed Circuit Boards (PCBs) made of different materials and solder ball alloys. The study examines PCBs with various Radio-Frequency (PJ) layers and different SAC solder alloys doped with different levels of Bismuth. Finite Element (FE) analysis (FEA) is used to gain a better understanding of the experimental results and to determine important metrics that can be correlated to the lifetime for temperature cycling of a FO-WLP on the corresponding PCB.

A methodology is presented that allows the evaluation of the thermomechanical reliability of electronic packages using “virtual prototyping.” Here, a virtual flip chip ball grid array (FC-BGA) is examined in comparison to a reference chip scale package (CSP). The comparison is performed using finite element simulation. A combined measurement-simulation technique is used to calibrate the finite element simulations on a reference object. The adjustment is based on the in-plane deformation field obtained by both simulation and optical measurement. For the latter, an optical sensor is used for in-plane deformation and strain field analysis based on the gray-scale correlation method. The findings obtained can be extrapolated to alternative package types with different but similar design to evaluate their suitability for the desired application before physical fabrication.

The thermomechanical reliability of the package and interconnections of assembled flip chip ball grid arrays (FC-BGA) is investigated in comparison to a reference chip scale package (CSP). Comparison is made using finite element (FE-) simulation. A combined measuring-simulation technique is applied to calibrate the finite element simulations on a reference object. Adjustment is made based on the in-plane deformation field evaluated by both simulation and optical measurement. For the latter an optical sensor for in-plane deformation and strain field analysis is used based on grey scale correlation method. A methodology is presented and to extrapolate the knowledge gained to alternative package types of different but similar design in order to evaluate their suitability for the desired application before the physical fabrication (virtual prototyping).

Among others, physics of failure related concepts are being developed to address the thermo-mechanical reliability challenges in automotive electronics. Limitations in particular applied for finite element (FE-) analyses are models of limited size, which rarely address the system character of failure. Also in testing a system view on fully mounted electronic control units (ECU) and loaded by environmental and active loading cannot be taken performing end-of-life tests for time limitations. Accelerated testing is done instead, however, mostly on board level. To overcome some of these limitations, a combined measuring-simulation technique is being developed, which is described in the paper. System level view on boards mounted in automotive ECUs is taken by a newly developed high-precision optical deformation measuring system. The multi-sensor measuring method combines a chromatic sensor for topography and warping analysis with an optical sensor for in-plane deformation and strain field analysis. By this combination, a high resolution can be reached for all three components of displacement vectors. Additionally, software tools allow the determination of derived quantities like strains, local curvatures and local warpage radius. The latter can be taken as input for FE-simulations. It is shown that some components, in particular QFNs, are sensitive to thermally induced cyclic warpage even if the corresponding bending deflections are in the micrometers range. Worst case in-plane stretching and cyclic warpage of a board mounted in an ECU have been measured. By corresponding simulations on QFN solder fatigue, mounted on a special test board, the critical fatigue life can be determined dependent on the interaction to the case, which differs by several hundred percent from a free-standing assembly.

During the course of the publicly funded project “HotPowCon” (HPC) a two-phase transient liquid phase soldering technology had been developed [1], with the advantage of processing conditions being close to those for conventional soldering. Further developments of this HPC solder material have been made resulting in a stable process with increased quality of the interconnection layer, i.e. better homogeneity and less voiding. The mechanical properties of the multi-phase materials are different from traditional soft solders and depend strongly on the process, in particular the phase proportions. Materials with different proportions were produced and their properties were studied both experimentally and by FE-simulations. A parametric 3x3 particles model was used for the latter. Measurements on the thermo-mechanical deformation behavior were made by a grey scale correlation method, which is behind the microDAC® system applied. Good agreement was achieved, which allows future HPC solder properties prediction and design.

Developments directed towards autonomous driving require complex smart functionalities at reasonable cost, e.g., combined sensing and high volume data processing. Reliability remains a key issue in that process. However, in various cases dedicated automotive grade components are lacking. Therefore, thermo-mechanical reliability issues are one focus of the European project TRACE, which studies the issues for transfer of consumer electronics (CE) into automotive electronics (AE). Gaps between these use scenarios are figured out and measures to be taken are searched [1].Besides the well-known harsh environmental AE requirements, mounting induced effects on components loadings need to be considered. These mounting conditions superimpose stresses driven by the component-board induced CTE mismatch and are in particular critical for leadless components like QFNs, LGAs; WLPs, characteristic of CE use. For evaluation of this loading scenario, a combined measuring-simulation technique has been developed. It uses an optical multi-sensor metrology system for the thermo-mechanical deformation measurement of electronic components and systems for different size and resolution ranges. An application to critical components in an electronic control unit (ECU) is depicted.The combined experimental-numerical method is applied to test-setups, to figure out effects from board mounting on component reliability and characteristic limits due to mounting. Test-boards with systems in QFNs are analyzed. It is shown, that system effects can have major impact on components stress and solder fatigue life.

The development of automotive electronics (AE) towards autonomous driving applications generates various challenges, in particular also on the reliable functionality. In various cases dedicated automotive grade components are lacking and consumer components have to be used instead, which hardly fulfil automotive standards. Some of the reliability challenges are therefore thermo-mechanical in nature. Some example issues, which are related to consumer electronics (CE) packaging, in particular MEMS-packaging, are given in the paper. Main focus is laid on the development of FE-simulation based evaluation methodologies accompanied by experimental characterization methods, in particular with regard to solder fatigue. It is shown that secondary effects such as, for example, intrinsic warpage of the component and of the circuit board, that are system related effects, can play an important role in AE application. A newly developed optical multi-sensor metrology method is presented for the thermo-mechanical deformation measurement of electronic components and systems for different size and resolution ranges. Thermally induced intrinsic warpage of circuit boards and components were analyzed both by means of the method. It was found that significant intrinsic deformations and warpages can occur and should be considered directly in AE system design and indirectly when evaluation stress risks, e.g. for solder fatigue.

For high temperature interconnection sintered silver can be used, however, it induces new demands on the thermo-mechanical design. That issue requires knowledge on the thermo-mechanical reliability of silver sintered devices, the subject of this paper. Material characteristics of the sinter layers are needed for simulation, which are addressed in the first part of the paper. Based on material properties of pure silver, for sintered silver with different porosities effective material characteristics have been derived by use of a micromechanical cell model. Shear loadings with in-situ deformation analyses have also been made to investigate sintered silver behavior. A complicated dependence on processing, temperature, and deformation rate is seen. Based on different effective constitutive models for the sintered interconnects, stress loadings are studied for a power module, an IGBT on DCB substrate, for passive and active thermal cycling. For the passive cycle complex interactions of the different layers of the stack are observed, which are not seen in a module with soft solder bonding. This result can be attributed to the missing decoupling by the soft soldering layer. Failure risks are evaluated by both conventional FEA and cohesive zone modeling. A quite different stress situation is depicted for active power cycling. The situation is even more complex and it is obvious from the simulations, that active power cycling can induce failure modes different from passive cycling.

Ensuring reliability of interfaces of dissimilar materials is one of the most critical design aspects of electronic assemblies. A study on the interface delamination phenomenon of different power packages was undertaken. Thermally induced stresses caused by the thermal mismatch between molding compound (MC), Si-die, and Cu- heatsink act as combined shear and normal loadings on the respective interfaces. Interface fracture- or damage mechanics was implemented to avoid the difficulties linked with the singular stress field at bi-material interface edges and to allow for inclusion of different interface adhesion parameter as well as damage progress. The cohesive zone approach was adopted for these purposes. A parametric study with different adhesion properties was performed to determine the critical interface energies causing delamination of different power packages. It turned out that delamination failure is not an issue for good adhesion properties, but depends on the package type. For lower critical fracture energies, delamination sensitive areas were found at the sawing edge of the die and at the MC-heatsink interface. Delamination onset was calculated based on a scalar damage metrics based on the critical interface energies. Delamination progress was followed and the delaminated areas were compared with experimental analyses. It turned out that at the critical interfaces MC-heatsink different types of delamination growth can occur which are stable and unstable delamination growth.

Simple adhesion tests like the pull-out test or the button shear tests have been used in industry for decades. They offer a great potential for comparison of different molding compounds, encapsulants, or adhesives on different types of substrates with or without surface treatment. However, for theoretical prediction purposes, interface fracture mechanics parameters are needed. Quantitative evaluations of the test applied to molding compound (MC)-button on Cu-leadframe by different fracture- and damage mechanical approaches are the subjects of the paper. Defect tolerant methodologies like the "virtual crack closure technique" (VCCT) and the J-inter-action integral approach, which consider the interface initially delaminated, are compared to the damage methodology “cohesive zone modelling (CZM)”, which needs no initial crack and can track the delamination progress. Calculated fracture parameters, in particular the energy release rates and mode mixity are compared. Effects on these parameters are discussed for different button shapes. In-situ tracking of dela-mination progress for a cubic button is shown using the optical correlation technique microDAC.

The image based displacement analysis called Digital Image Correlation (DIC) can be used as an alternative to classical TMA and other bulk methods to measure CTE-values of electronic packaging materials. By combining the operation of the thermally optimized commercial equipment EQUINOX from the company OMI and the correlation software VEDDAC of CWM GmbH Chemnitz, it was possible to develop a method to acquire anisotropic CTE values of specimens locally and with an accuracy of +/- 0.5*10 -6 /K over the entire value scale.

The liquid crystal display (LCD) technology is confronted with the task to substitute rigid glass plates enclosing the electro-optically active liquid crystal (LC) material by plastic substrates. In particular, the commercialization of flexible displays requires a sufficient stabilization against external mechanical distortions. To achieve LC layer stabilization, several procedures have been suggested. In this work, the thermal-induced phase separation (TIPS) technique has been applied to generate composite films consisting of LC compartments which are encased by coherent polymer walls after binodal phase separation. Composite films were prepared from a series of poly(methacrylates) and various commercial nematic LC mixtures. Furthermore, the use of copolymers as well as binary blends from “hard” and “soft” poly(methacrylates) broadens the possibilities to control the film morphology. To compare different polymer/LC composite films regarding their stability under compression load, the samples were investigated by indentation tests using an inverse reflected-light microscope combined with a digital image acquisition technique. The deformation of the composite layers was evaluated by the uniDAC image analysis which relies on the more general method of Digital Image Correlation (DIC). Some of the fabricated composites show a remarkably high indentation resistance, especially such prepared from poly(1-tetralyl methacrylate) and poly(4-tert-butylcyclohexyl methacrylate). The results facilitate the selection of suitable composite systems for the fabrication of mechanically stabilized flexible LC displays. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

More and more dense packaging is one of the most important challenges in advanced electronics and micro technology. One way to achieve this is to bury active as well as passive components into the printed circuit boards. In addition, very short interconnects can be realised which is advantageous especially for RF applications.Besides the pure functionality, the designers of new products have to meet reliability requirements. This is not only related to the electrical properties but also to the thermal as well as the thermo-mechanical design. As most as possible of the imaginable loading conditions have to be investigated which are expected during manufacturing, testing, storing, and operation. This can be done efficiently by numerical studies based on finite element analyses (FEA), accompanied by deformation measurements at suitable test structures. The resulting methodology is outlined here, can be generalised, and applied to many design procedures before any real parts are available [1]. It is helpful to reduce cost and time-to-market for future products by minimising real tests and an expensive redesign.

More and more dense packaging is one of the most important challenges in advanced electronics and micro technology, driven by requirements like low cost and high reliability. One way to meet these demands is to follow the so-called ldquochip in duromerrdquo approach, which allows an extremely dense integration and very short interconnects. Already in the very first design phase of advanced products, numerical studies by means of finite element analyses (FEA) are very efficient to check the desired properties regarding functionality as well as reliability aspects. This has been carried out with a new generation of active distance control (ADC) devices for automobiles, based on a radar principle. In order to obtain sufficiently flat modules for subsequent manufacturing steps, thermally induced deformations were measured at suitable specimens by means of the microDAC technique, developed by CWM GmbH Chemnitz and Fraunhofer IZM. Combining FE analyses and measured deformations, a methodology was developed which can be generalised and applied to many design procedures before any real parts are available [1]. It is helpful to reduce cost and time-to-market for future products by minimising real tests and an expensive redesign.

The reliability of MEMS is influenced strongly by thermomechanical aging and failure mechanisms, acting as the main reason for defects in real applications. The stability of the materials and interface properties in the structured compounds is essential for the behaviour in very long lifetime applications of MEMS. By coupling of experimental deformation analysis by means of high resolution optical methods with thermal, mechanical or thermomechanical loading and numerical simulation it is possible to evaluate material properties and parameters and to analyze the physical nature of failure and degradation mechanisms. A thermal loading unit designed for such applications is presented.

Increasing use under harsh environmental conditions - extreme temperatures, in particular often lead to fatigue and failure of advanced electronic packages and related systems. As a result, its thermo-mechanical reliability becomes more and more one of the most important preconditions for adopting it in industrial applications.

Fatigue and failure of advanced electronic packages and related systems is often caused by their increasing use under harsh environmental conditions - extreme temperatures, in particular. As a result, its thermomechanical reliability becomes more and more one of the most important preconditions for adopting it in industrial applications. Residual stresses from several steps of the manufacturing process, thermal and static and dynamic mechanical loading conditions along with the fact that microelectronic packages are basically compounds of materials with quite different Young's modules and thermal expansion coefficients contribute to interface delamination, chip cracking and fatigue of interconnects. Consequently, numerical investigations by means of nonlinear parameterized FEA, fracture mechanics concepts are frequently used for design optimizations using sensitivity analyses (Auersperg et al., 2001). So, numerical design studies can help to optimize designs of electronics applications at the earlier phase of the product development processes. Unfortunately, this methodology typically accounts for classical stress/strain evaluation or life-time estimations of solder interconnects using modified Coffin-Manson approaches. Delamination or bulk fracture mechanisms usually remain unconsidered. This contribution intends to figure out and discuss ways of using fracture mechanics numerical approaches in connection with parameterized FEA based DOE/RSM. For improving such methods, the evaluation of mixed mode interface delamination phenomena of several ceramics/encapsulant-specimens under bending has been combined with experimental deformation measurements. Measured force vs. deflection curves, deformation fields as results of optical inspection and deformation analysis as well as crack tip vs. deflection curves determined using constitute the input for the delamination modeling by means of FEM. Major goal of the study is to make such a way determined interface toughness parameters applicable within DOE/RSM-approaches.

The CIME (Computational Intelligence Mill Expert) expert system is used for qualitative and quantitative optimization of cement grinding in a ball mill. The aim of the system is to achieve a high level of continuity of the mill operation so that an increase in throughput with simultaneous reduction of power consumption is achieved through optimum plant utilization. In the past the fineness of the finished product was determined exclusively by automatic laboratory evaluation, which entailed a delay of 30 min. A neural network is now used to reduce the delay time for a process variable which is required as the input variable for the fineness controller in the expert system.

Es wird eine Methode zur Untersuchung von Grenzflächenfestigkeit und Delaminationsprozessen sowie zur Beschreibung von Rissentstehung und Rissfortschritt in Verbundmaterialien vorgestellt. Mit dem optischen Messverfahren UNIDAC (Universal Deformation Analysis by Correlation) können lokale Verformungen und Verformungsfelder erfasst und beschrieben werden. Die bei mechanischer Belastung der Proben auftretenden Veränderungen werden mit einer optischen Technik erfasst und die bei unterschiedlichen Laststufen aufgenommenen digitalisierten Bilder mittels eines geeigneten Korrelationsalgorithmus „verglichen”. Damit kann sowohl das Deformationsverhalten des Materials als Ganzes sowie einzelner Bereiche des Verbundes und seiner Komponenten beschrieben und Aussagen über das Verhalten der Grenzschichten bei Belastung abgeleitet werden. Die lokalen Verschiebungsfelder innerhalb einzelner Komponenten werden getrennt erfasst und der Rissfortschritt kann direkt verfolgt werden. Die vorgestellten Ergebnisse beruhen auf der Kombination zwischen dem UNIDAC-Verfahren und dem Dreipunktbiegetest. Aus den Messwerten können weitere Werkstoffkenngrößen abgeleitet werden.

Cracking in various interfaces is a significant concern for yield loss and reliability of advanced packages. There are many reasons for interface damage, for example, low adhesion due to incompatible interfaces or due to contamination. Delamination at the encapsulant-substrate or chip-substrate interfaces can lead to cracking of the electrical interconnents.To assess the integrity of the interface, the following information is necessary: the interfacial adhesion, a pertinent simulation model, and an estimate of the maximum length of a permissible initial crack.In this paper a method is discribed to investigate the interface strength and the process of delamination and to pursue crack initiation and crack propagation. The 3-point-bending-test is combined with the optical measuring procedure DAC (Deformation Analysis by Correlation), a method of digital image processing. Digitized images of the specimen under different bending load steps are compared by a correlation algorithm. This allows to determine and to evaluate the local displacements and displacement Welds.The investigations of local displacements and displacement fields by optical methods in combination with a Finite Element Analysis lead to a better understanding of crack intiation and crack propagation and consequently to detailed knowledge about package stability.