M. Carmona

Design of a modular micropump based on anodic bonding

A simple and reliable technology for the fabrication of micromachined micropumps is presented. The assembling of different wafers to produce valves and cavities is usually the critical step regarding final yield. Our technology uses exclusively the well known anodic bonding technique for this purpose. The prospective performance of the devices has been evaluated by finite element methods and system level simulations.

A time-domain method for the analysis of thermal impedance response preserving the convolution form

The study of the thermal behavior of complex packages such as multichip modules (MCMs) is usually carried out by measuring the so-called thermal impedance response, that is: the transient temperature after a power step. From the analysis of this signal, the thermal frequency response can be estimated, and consequently, compact thermal models may be extracted. We present a method to obtain an estimate of the time constant distribution underlying the observed transient. The method is based on an iterative deconvolution that produces an approximation to the time constant spectrum while preserving a convenient convolution form. This method is applied to the obtained thermal response of a microstructure as analyzed by finite element method as well as to the measured thermal response of a transistor array integrated circuit (IC) in a SMD package.

Dynamic simulations of micropumps

The dynamic simulation of micropumps puts strong requirements on the simulator. Instead of developing a new computer code for coping with these simulation problems, this work emphasizes the harmonic integration of existing finite-element and electrical simulators to effectively predict the actuator performance with minimum software developing effort. This approach is applied to a thermo-pneumatic micropump.

Modelling of microsystems with analog hardware description languages

A methodology for the modelling of microsystems with analog hardware description languages is presented. This procedure implies several steps with emphasis in model complexity reduction, model adaptation, identification of critical parameters and partial validation of the system sub-components followed by full verification of the complete model. This procedure will be applied to the modelling of piezoresistive sensors, capacitive accelerometers and thermo-pneumatic micropumps.

Issues in the Use of Thermal Transients to Achieve Accurate Time-Constant Spectrums and Differential Structure Functions

An analysis of accuracy of time-constant spectrum extraction from thermal transients has been performed. Numerical calculations based on analytical models and finite element method simulations have been used in order to obtain the thermal transients. Simple geometries have been used such that analytical expressions for their time-constant spectrums are known. Results show that a large error in the time-constant spectrum is obtained for very small rms error (<;1 mK) in the thermal transient. The estimation problem is ill-conditioned. Moreover, the differential structure function shows a low accuracy identifying stacked structures. The initial part of the differential structure function shows numerical oscillations and the final part has an asymptotic behavior to infinity that has been identified as an artifact related to errors in the time-constant spectrum estimation. Peak identification from the differential structure function heavily depends on an accurate determination of the time-constant spectrum. The limited spectral resolution and dynamic range of the differential structure function are a direct consequence of the time-constant spectrum imprecision.

Optimization of voltage-controlled thin-film microstructures

Some criteria and design rules useful for the elaboration of sensors based on force-balanced capacitors are shown. To achieve this goal we have interrelated the mechanical and geometrical properties of the system with the final working features, such as sensitivity, bandwidth, full-scale range and maximum controlling voltage. To derive these relations we have also applied stability criteria. Moreover, as the optimization of the electronic feedback control of micromechanical structures can be improved by an accurate knowledge of mechanical parameters such as resonance frequency and damping ratio, we have also included a finite-element method (FEM) to determine the pressure distribution and damping ratio of any mechanical configuration immersed in a viscous fluid.

Simulation and Modelling of Thermo-Pneumatic Micropumps with HDLA

Abstract The simulation and modelling of silicon microsystems requires the use of tools at different levels of abstraction. The complexity of such systems does not permit the s imulation of the complete microsystem at the physical level because of the coupled phenomena between signals of different nature (electrical, thermal, fluidic, etc.). We report how analog hardware description languages permit the modellization and simulation of thermo-pneumatic micropumps. The similarity of the mathematical descriptions of electrical and fluidic networks makes it possible to simulate them in a single package. The data for behavioural description of subcomponents have been extracted from finite element simulations and analytical formulae.

Test structures for CMOS-compatible silicon pressure sensor reliability characterization

Pressure sensors structures have been fabricated in a commercial CMOS foundry technology using a post-processing for back-side wafer micro machining. In order to predict the sensor response to an externally applied differential pressure, the structure behavior has been simulated by Finite Element Methods. The design and fabrication of test structures for these sensor devices is described. Experimental results obtained using these structures are presented.