Thermal Management Using MEMS Bimorph Cantilever Beams

Abstract

This paper examines a passive cooling technique using microelectromechanical systems (MEMS) for localized thermal management of electronic devices. The prototype was designed using analytic equations, simulated using finite element methods (FEM), and fabricated using the commercial PolyMUMPs™ process. The system consisted of an electronic device simulator (EDS) and MEMS bimorph cantilever beams (MBCB) array with beams lengths of 200, 250, and 300 μm that were tested to characterize deflection and thermal behavior. The specific beam lengths were chosen to actuate in response to heating associated with the EDS (i.e. the longest beams actuated first corresponding to the hottest portion of the EDS). The results show that the beams deflected as designed when thermally actuated and effectively transferred heat away via thermal conduction. The temperature when the beams reached Bnet-zero^deflection (i.e. uncurled and flat) was related to the initial deflection distance while the contact deflection temperature and rate of actuation was related to beam length. Initial beam deflections, after release, and contact temperatures, when fully actuated, were approximately 5.05, 9.45, 14.05 μm, and 231, 222, 216°C, respectively with the longer beams making contact first. This innovative passive thermal management system enables selective device cooling without requiring active control or forced convection to maintain steady-state operating temperatures for sensitive microelectronic devices.

Analytical, Numerical and Experimental Study of a Horizontal Electrothermal MEMS Microgripper for the Deformability Characterisation of Human Red Blood Cells

“…The metal layer can be selectively deposited on the structure to enhance thermal expansion. However, this might also result in an increase in the beam’s out-of-plane displacement due to the creation of a bimorph structure [ 25 ]. The structure is finally released by immersing the chip in a standard hydrofluoric (HF) solution designed to fully remove the sacrificial PSG layers from the fabricated structure.…”

“…Additionally, the amount of thermal radiation emitted by a structure is given by , where is the Stefan-Boltzmann constant, A is the surface area, and T is the temperature. Since this actuator is not designed for routine operation at high operational power (thus temperatures are relatively low), and since the area of the actuator is extremely small, the influence of thermal radiation on the deflection of the thermal actuator is also not significant and thus can reasonably be assumed negligible in this work [ 25 ]. The principal sources of heat losses for thermal actuators operated close to room temperature in still air are thus conduction through the polysilicon beam’s anchor pads, and through the air gap and nitride layer, to the substrate.…”

The Effects of Structure Thickness, Air Gap Thickness and Silicon Type on the Performance of a Horizontal Electrothermal MEMS Microgripper

“…On the other hand, due to the absence of a small air gap beneath the overhanging SOIMUMPs TM structure (Figure 2b), there is no dominant convective heat loss from the bottom surface compared to the other beam surfaces and thus, in this case, a convective heat transfer coefficient was equally applied to all the beam surfaces in the numerical model for Design Variant 4 to simulate heat losses by natural convection in air. Moreover, heat losses by radiation can be reasonably ignored for thermal actuators operated at low operational power [44,45] and were thus excluded from all the models in this work.…”

Thermal buckling analysis of nano composite laminated and sandwich beams based on a refined nonlocal zigzag model

“…MEMS devices often require structures and materials that are lightweight, strong, and can be tailored to specific mechanical and thermal properties. Composite laminated and sandwich structures, with their high stiffness and low weight properties, have found various applications in MEMS, such as lightweight but highstrength designs, thermal management, customized mechanical properties, and miniaturization and integration [6][7][8][9]. By now, the use of composite materials is likely to play an increasingly important role in optimizing the performance of these micro-scale devices.…”