An autonomous capacitive sensor system for high accuracy and stability position measurement, such as required in high-precision industrial equipment, is presented. The system incorporates a self-alignment funcion based on a thermal stepping motor and a built-in capacitive reference, to guarantee that the relative position between the sensor electrodes is set to 10 ± 0.1µm. This is needed to achieve the performance specifications with the capacitive readout. In addition, an electronic zoom-in method is used to reach the 10 pm resolution with minimum power dissipation. Finally, periodic self-calibration of the electronic capacitance readout is realized using a very accurate and stable built-in resistive reference. The performance is evaluated experimentally and with simulations. Keywords: Capacitive Sensor System, Position Measurement, Self Alignment, Self Calibration, Thermal Actuator@en

Wafer Level Packages are one of the most advanced packaging concepts. It combines the advantages of flip chip with conventional surface mount technologies. In recent years, we have seen a tremendous growth in the application of Wafer Level Packages, both in quantities as well as in the number of products where they are implemented. The technology is, however, not without its challenges with 1st and 2nd level reliability issues. For instance, the limit on the size of Wafer Level Packages has to do with the 2nd level, or solder bump, reliability. This paper highlights our major research and development results on understanding and enhancing the 1st and 2nd level reliability of Wafer Level Packages using combined experimental and virtual prototyping (thermal, mechanical and thermo-mechanical) techniques. Typical 1st level reliability problems within Wafer Level Packages are cracking of repassivation materials, fatigue of bond over active pads, and cracks within the Under Bump Metalisation. Typical 2nd level problems concern solder fatigue and brittle fractures within the intermetallics. To investigate the physics of failure for these problems, dedicated parametric finite element models are constructed including the thin IC layers. Two structures are explored to their potential reliability benefits, being the traditionally used repassivation structure and a newly developed Bump on Active structure. This so-called BUMA structure makes use of a thick A1 buffer layer. By combining the experimental results with reliability prediction models, both structures in terms of 1st and 2ne level reliability performance are explored. Based on the results we have designed and manufactured an improved construction that significantly outperforms current solutions.@en

In this paper the temperature effects on the effective Young's modulus of [110] silicon cantilevers is analyzed and measured in the range of 25-100°C. The quasi-static pull-in instability method developed recently for ultra-thin cantilevers [H. Sadeghian, C.K. Yang, J.F.L. Goosen, E. van der Drift, A. Bossche, P.J. French, F. van Keulen, Characterizing size-dependent effective elastic modulus of silicon nanocantilevers using electrostatic pull-in instability, Appl.Phys.Lett.94(22)(2009)221903] is employed to measure the temperature sensitivity of the ultra-thin cantilevers (Dutch Patent App.,No.P6027025NL). A temperature sensitivity of 81.3°C/V is obtained. The temperature sensitivity is mostly due to the temperature dependence of the effective Young's modulus of silicon. It is shown that changes in geometrical dimensions due to the change in temperature can be neglected. The changes in the effective Young's modulus due to the changes in the temperature are extracted using a thermo-electro-mechanical coupled system. The pull-in method showed substantial advantages over other methods used for the study of the thermal effects on micron and sub-micron structures. The method is reproducible for various temperatures and cantilevers' dimensions and the results demonstrate a new concept for a temperature sensor with ultra-high sensitivity.@en

In this paper, the Copper wirebonding technology is investigated. From a numerical point of view, the wirebonding process is modelled. Experiments on specially designed bondpads are performed in order to verify the models. As such, this leads to a thorough understanding of the wirebonding process, especially the forces that take a role during this process.@en

In this paper, virtual prototyping is used to generate more accurate and efficient stress design rules for IC backend structures, in combination with packaging processes and geometry. The addressed failure mode is passivation cracks and depending on the package type or family this failure mode is easier to occur. A series of experiments are conducted to prove the effect of the package type on this IC failure mode. It is demonstrated that for successful development of IC backend structures and processes, it is essential to take into account the influence of the package in the earlier phase of IC backend development. The so-called integral design rules, accounting for all the major loading sources and history of the complete product creation process has to be used for the development of new generation semiconductors devices.@en

Transferring molding process is widely used in the plastic IC packaging. Die cracking failures due to transfer molding process may occur. In this paper, an investigation on the die fracture and its failure probability is conducted. The approaches and results of die strength characterization, FE modeling on the laminate-based packages, and simulation-based prediction of the die fracture probability rate are presented. Weibull statistics model was used to describe the probability distribution. Model parameters were obtained by fitting to the test results. 3D parametric FE models were established to conduct numerical simulations to predict the stress field and die fracture probability caused during the tranfer molding process. For a BGA package, the influence of the solder mask opening under the die on the fracture probability was investigated. For the capped MEMS, high stress levels are induced in the cap and the MEMS die during the molding process. The cavity size, cap thickness, the molding pressure, and the wafer surface finishing process have significant influcences on the fracture failure probability. It shows that improvement of die fracture probability can be achieved by changing the designs of the die surface finishing process to meet the reliability requirements.@en

This paper presents our effort to predict reliability problems for MEMS packages. MEMS devices are vulnerable to the external loads subjected to it. As such, MEMS devices need to be protected. Capping the device can generate protections: a piece of silicon is placed on top of it to create a cavity above it. Parametric Finite Element models are combined with dedicated verification experiments to address the reliability of four different capping concepts. The results gain a better understanding of MEMS capping issues, with failure modes as cavity deflection, cap fractures, and moisture penetration.@en

This paper presents our effort to predict reliability problems for MEMS packages. MEMS devices are vulnerable to the external loads subjected to it. As such, MEMS devices need to be protected. Protections can be generated by capping the device: a piece of silicon is placed on top of it to create a cavity above it. Parametric finite element models are combined with dedicated verification experiments to address the reliability of four different capping concepts. The results gain a better understandig of MEMS capping issues, with failure modes as cavity deflection, cap fractures, and moisture penetration.@en

In the electronics industry epoxy molding compounds, underfills and adhesives are used for the packaging of electronic components. These materials are applied in liquid form, cured at elevated temperatures and then cooled down to room temperature. During these processing steps residual stresses are built up resulting from both cure and thermal shrinkage. In order to minimize these stresses inorganic fillers are added. These fillers have several opposing effects on the residual stresses because they decrease the cure shrinkage and thermal contraction but increase the modulus below and above the glass transition temperature. In this paper an extensive study on the cure-dependent rubbery moduli of a series of silica spheres filled epoxy resins is carried out both experimentally and theoretically. Low frequency dynamic mechanical analysis (DMA) was used to measure the rubbery modulus build-up during cure. A model based on scaling analysis was applied to describe the evolution of the rubbery shear modulus. The effect of the filler percentage on the rubbery shear and bulk moduli as well as the coefficients of thermal expansion were measured and compared with models from the theory of particulate-filled composites.@en

Warpage is a critical issue for QFN array molding process. In this paper, a cure-dependent viscoelastic constitutive model is established to model the cure-induced warpage in array molding process. For the relaxation modulus functions of the packaging polymer , the equilibrium moduli are modeled with a model based on scaling analysis and the relaxation behavior of the transient part is described by the cure-dependent relaxation amplitude and reduced relaxation times which are based on the time-conversion superposition principle. The cure-dependent parameters are characterized by using an integrated approach of dynamical mechanical analysis (DMA) and differential scanning calorimetry (DSC) measurements. Finite element modeling is carried out for three configurations of a carrier package during the curing process has significant contribution on the toal warpage of the map.@en

Package warpage, interface delamination and thermal fatigue are the major reliability concerns for micro-electronic packages, caused by mismatch in thermal expansion together with residual stress originating from the curing process of the packaging polymers. To investigate the influence of the residual stress- and strain fields on the failure predictions and to optimise the product for reliability, cure-dependent viscoelastic constitutive relations for the applied polymers are required. The present paper gives an overview of recent progress in establishing such relations. A model moulding compound is used for cure dependent characterization and is subsequently used for QFN package moulding. The modelled and the experimentally obtained warpage have been compared.@en