COMSOL MULTIPHYSICS TUTORIALS HOW TO

So, this is that vacuum cavity between the silicon membrane and the grounded body of the sensor. This is useful when we assign materials to the model.Īn Explicit selection has been used to select the cavity domain. All the domains, which make up the steel base, have been selected. These will be used when specifying the symmetry boundary conditions in the physics interface. We’ve also created a collection of boundaries, which make up the YZ -Symmetry Plane and a collection of boundaries, which make up the XZ -Symmetry Plane. It’s right in the center of the underside of the membrane. This point is the point where we expect the maximum deflection. And an Integration operator, which integrates one point. You can see, highlighted in blue, the underside of the silicon membrane. So, here we have the silicon membrane, the cavity, and the silicon die. Boundary 12 corresponds to the underside of the silicon membrane. An Average operator, which operates on boundary 12. To simply the configuration of the physics interface and to aid with postprocessing of the results, it is convenient to now define some coupling components and some geometry selections. Here, you can see we’ve imported a pre-made geometry, which is one quarter of the device we are modeling. To do this from the Home tab, select “Import” and choose the desired file. For convenience, the geometry is imported from an external file. This is the ambient pressure at which the device is operating and we have two temperatures: “T0”, the ambient temperature at which the device operates, and a reference temperature, “Tref”, which is the temperature at which the device is bonded to its package. Here, you can see there are three imported parameters: “p0” is a pressure. Click “Parameters” and then select the desired file. The first step is to import some model parameters, which we’ll use to specify variables within the model. From the Preset Studies list, we choose a Stationary study. Next, we add the Electromechanics physics interface. To begin, we select the Model Wizard and then choose a 3D Space Dimension. In both cases, the deflections are detected by measuring a change in the capacitance between the membrane and ground. We will investigate the deflections of the membrane due to both ambient pressure changes and thermal stresses resulting from a poor choice of package. It is separated from the ambient air by a thin membrane, which is electrically isolated from the grounded body of the sensor. The sensor consists of a thin chamber, sealed under high vacuum, acting as the dielectric in a capacitor. The geometry of the sensor is symmetric, so only a single quadrant is modeled. Today, we will be simulating a capacitive pressure sensor, both with and without stresses induced by the packaging. Shown in the video: Capacitive Pressure Sensor.

The video demonstrates the importance of considering multiphysics effects when designing electromechanical devices. In this example, we examine the performance of the pressure sensor both with and without the thermal stresses induced by the packaging. This results in mechanical stresses at the interface between the two materials, which can cause additional temperature-dependent deflections of the membrane. Since silicon and steel have different coefficients of thermal expansion, the capacitor and the base plate contract at different rates as the device cools back down to its operating temperature. The silicon capacitor is packaged onto a steel base plate using a thermal bonding technique that requires a temperature that is much higher than that at which the sensor is intended to operate. The capacitance of the device is thus dependent on the ambient pressure and, when connected to suitable circuitry, can be used as the basis for a pressure sensor. Changes in the ambient air pressure induce deflections in the membrane, which alter the distance between the capacitor plates. The cavity is sandwiched between a silicon die and a thin silicon membrane, which is exposed to the ambient atmosphere. In this model, a vacuum cavity serves as the dielectric in a miniature parallel plate capacitor. Video: Modeling Electromechanics in COMSOL MultiphysicsĪ capacitive pressure sensor is achieved by engineering a circuit such that its capacitance is dependent on the ambient pressure in which it is operating. COMSOL Multiphysics version 4.4 and the MEMS Module are used to simulate the electrostatic, structural, and thermal physics that occur.

COMSOL MULTIPHYSICS TUTORIALS HOW TO

We have just published an updated version of our video tutorial on how to simulate a capacitive pressure sensor. If you are searching for a tutorial on how to model a miniaturized 3D electromechanics problem, then look no further.

Comsol multiphysics tutorials