Effects of the Manufacturing Process on the Reliability of the Multilayer Structure in MetalMUMPs Actuators: Residual Stresses and Variation of Design Parameters

Abstract

Potential problems induced by the multilayered manufacturing process pose a serious threat to the long-term reliability of MEMSCAP® actuators under in-service thermal cycling. Damage would initiate and propagate in different material layers because of a large mismatch of their thermal expansions. In this research, residual stresses and variations of design parameters induced by metal multi-user micro electromechanical system processes (MetalMUMPs) were examined to evaluate their effects on the thermal fatigue lifetime of the multilayer structure and, thus, to improve MEMSCAP® design. Since testing in such micro internal structure is difficult to conduct and traditional testing schemes are destructive, a numerical subdomain method based on a finite element technique was employed. Thermomechanical deformation from metal to insulator layers under in-service temperature cycling (obtained from the multiphysics model of the entire actuator, which was validated by experimental and specified analytical solutions) was accurately estimated to define failures with a significant efficiency and feasibility. Simulation results showed that critical failure modes included interface delamination, plastic deformation, micro cracking, and thermal fatigue, similarly to what was concluded in the MEMSCAP® technical report.

Description of the Resin Curing Process—Formulation and Optimization

“…Residual stresses and their influence on the structure of the composite material can be considered at various levels [8,12,63,64,65,66,67,68,69], i.e., the microscale (fiber/matrix), at the scale of the individual layer (laminate) or at the macroscale (structure)—Figure 2. At the level of the microstructure, the influence of residual stresses is usually taken into account by introducing a safety coefficient in the values determining allowable stresses and strength for composite materials.…”

“…The final products can be created simultaneously with the creation of the material, which is generally the case of thermosetting resin matrix composites. In thermoplastic resin composites, it is more common to fabricate the composite first and form or mold the shape in the second operation [6,7,8,9].…”

A study on the surface correction of large format infrared detectors

“…In particular, when a device becomes larger in size, its structural stability becomes relatively worse [15,16]. Increasing the size of the focal plane array increases the complexity of experiments, and even worse, it results in higher costs, longer periods and more serious thermal stress effects [17][18][19][20]. Therefore, a surface correction structure is proposed to adjust the monolithic large format hybrid infrared focal plane array detectors to enhance the stability of the structure.…”

Micro-structured medium with large isotropic negative thermal expansion

“…Dental fillings in biomedical applications need to have their expansion coefficients matched to those of teeth [5] and negative thermal expansion (NTE) can be used to lower the overall expansion coefficient of a composite to obtain a predetermined value. By contrast, materials with extremely large expansion are employed as thermal actuators [6], while NTE and Poisson's ratio can also be implemented in MEMS to reduce fatigue problems under in-service thermal cycling [7]. It is then clear that a medium that can be easily designed to have a predetermined CTE in a broad range of temperature working conditions is extremely attractive in different technological applications.…”