Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis, air damping effect, reliability, numerical modeling method, and application of electrostatic-driven MEMS devices.

This study investigated the impact of material properties of epoxy molding compounds on wafer warpage in fan-out wafer-level packaging. As there is currently a lack of comprehensive discussion on the various material property parameters of EMC materials, it is essential to identify the critical influencing factors and quantify the effects of each parameter on wafer warpage. The material properties include Young’s modulus of the epoxy molding compound before and after the glass transition temperature (Tg) range of 25–35 °C (E_L) and 235–260 °C (E_H), coefficient of thermal expansion (α1, α2), and the temperature change (∆T) between E_L and E_H. Results show that, within the range of extreme values of material properties, E_L and α1 are the critical factors that affect wafer warpage during the decarrier process in fan-out packaging. α1 has a more significant impact on wafer warpage compared with E_L. E_H, α2, Tg, and ∆T have little influence on wafer warpage. Additionally, the study identified the optimized material property of the epoxy molding compound that can reduce the maximum wafer warpage in the X and Y directions from initial values of 7.34 mm and 7.189 mm to 0.545 mm and 0.45 mm, respectively, resulting in a reduction of wafer warpage of 92.58% (X direction) and 93.74% (Y direction). Thus, this study proposes an approach for evaluating the impact of material properties of epoxy molding compounds on wafer warpage in fan-out wafer-level packaging. The approach aims to address the issue of excessive wafer warpage due to material variation and to provide criteria for selecting appropriate epoxy molding compounds to enhance process yield in packaging production lines.

This study successfully established a strip warpage simulation model of the flip-chip process and investigated the effects of structural design and process (molding, post-mold curing, pretreatment, and ball mounting) on strip warpage. The errors between simulated and experimental values were found to be less than 8%. Taguchi analysis was employed to identify the key factors affecting strip warpage, which were discovered to be die thickness and substrate thickness, followed by mold compound thickness and molding temperature. Although a greater die thickness and mold compound thickness reduce the strip warpage, they also substantially increase the overall strip thickness. To overcome this problem, design criteria are proposed, with the neutral axis of the strip structure located on the bump. The results obtained using the criteria revealed that the strip warpage and overall strip thickness are effectively reduced. In summary, the proposed model can be used to evaluate the effect of structural design and process parameters on strip warpage and can provide strip design guidelines for reducing the amount of strip warpage and meeting the requirements for light, thin, and short chips on the production line. In addition, the proposed guidelines can accelerate the product development cycle and improve product quality with reduced development costs.

We propose an approximate analytical solution to the pull-in voltage of a microcurled cantilever beam. The analytical model considers the realistic situations, which include stress gradient, nonideal boundary conditions, and fringing field capacitance. The proposed analytical model can be used at wafer level for extracting the Young’s modulus of the thin film of which the cantilever beam is made. The approximate analytical solution is obtained based on the Euler’s beam model and the minimum energy method. The accuracy of the proposed model is verified to be more accurate than the other published models. The model presented in this work can be used for wafer-level evaluation of the material properties through simple electrical testing and is also expected to find use in the design of microelectromechanical devices.