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D2W simulation

Wed, 04 Nov 2026 08:12:11 +0000

Hello!

I am currently trying to modify the official COMSOL die-to-wafer (D2W) bonding example. In my modified model, I have increased the thickness of the upper die to match the thickness of the lower wafer, while keeping all other physics settings unchanged.

So far, I have performed parametric sweeps of the initial warpage, bonding time, and downward displacement. However, the bonded area remains very small in all cases.

My question is: How can I modify the model to ensure that the upper die, after increasing its thickness, can undergo the same bonding process as in the original model with the thinner upper die? Are there any additional adjustments needed to the physical settings, boundary conditions, contact definitions, or solver configurations to account for the increased thickness and bending stiffness?

I would greatly appreciate any suggestions or guidance. Thank you very much for your time and help!

Request a Trial

Sun, 01 Nov 2026 17:19:19 +0000

Can you provide me with a trial code so I can test it out and see if it's suitable for my project?

Finding Quality factor for a Photonic crystal cavity

Thu, 29 Oct 2026 15:20:27 +0000

I have to find the Quality factor for a GaAs Photonic crystal cavity...Please give steps...Also give some techniques to improve quality factor in the range of 45,0000...

Using Heat Release Rate (HRR) vs. Temperature-Time Curve as Input

Mon, 26 Oct 2026 21:01:51 +0000

Hello,

I am modeling a fire scenario in COMSOL and have the fire defined by a Heat Release Rate (HRR, kW) versus time curve. Is it possible to use an HRR-time curve directly as an input in COMSOL? Can a tabulated HRR-time function be imported and used directly as a time-dependent heat source? My objective is to model the thermal response of a structure subjected to a fire characterized by a measured/design HRR-time history. Any guidance or example models would be greatly appreciated. Thank you.

How can I better represent the weld spots of a pillow plate heat exchanger in a 2D CFD model

Wed, 21 Oct 2026 08:46:12 +0000

Hey all,

I am currently working on a fluid flow simulation of a pillow plate heat exchanger, see link. I have a 3D model of a segment of the pillow plate to study the flow pattern inside the channel. Since the 3D geometry is quite complex and has a long simulation time, I decided to develop a simplified 2D model. I understand that a 2D model cannot capture all the three-dimensional flow effects, but I have managed to get reasonably far with the simplification.

However, I am still struggling to reproduce the flow pattern around the weld spots. When I compare the velocity fields in the xy-plane of my 3D model with those of my 2D model, I notice that the flow in the 3D model is considerably more constricted around the weld spots. I suspect this is caused by the interaction between the weld spot geometry and the wavy channel walls.

So my question is, is there a way to represent the effect of the weld spots more accurately in a 2D model? Maybe a COMSOL setting or a modification in the model?

Thank you in advance!

Adding Sheet Resistance in COMSOL

Mon, 19 Oct 2026 04:26:55 +0000

Hi, I want to add Sheet Resistance (600 ohm) for A FSS Layer (Microwave region) in COMSOL to replicate the simulated & Experimental Result of a particular Paper. I have searched in Google about the provision to add Sheet resistance. It suggests me to use transition boundary condition(using conductivity and approximate thickness) or surface current density for the FSS layer, However it is not replicating the experimental and the simulated result of the paper. Am i doing something wrong. Is there any other boundary condition i must use to replicate the result ?. The paper uses CST for simulation.

Potential Error in the Electrostatic Force Expressions – Taylor Cone Model

Sun, 11 Oct 2026 07:00:26 +0000

Dear COMSOL Support Team, dear Forum,

I identified a potential error in the “Taylor Cone” application model (Application ID: 3828), which couples Electrostatics, Laminar Flow, and Level Set.

In this model, the volumetric electrostatic force components are defined as follows:

Radial component:

Fes_r = 0.5(es.Er^2+es.Ez^2)epsilon0_const(1+(er_liq-1)philsr)

Axial component:

Fes_z = 0.5(es.Er^2+es.Ez^2)epsilon0_const(1+(er_liq-1)philsz)

However, phils represents the dimensionless Level Set function, while philsr and philsz correspond to its spatial derivatives with respect to r and z, respectively. These derivatives therefore have units of m⁻¹.

Consequently, the terms (1+(er_liq-1)philsr) and (1+(er_liq-1)philsz) are dimensionally inconsistent, since they involve the addition of a dimensionless constant and a quantity expressed in m⁻¹.

Furthermore, assuming a perfect dielectric system without free electric charges, the volumetric electrostatic force derived from the divergence of the Maxwell stress tensor should be:

Fes = −0.5 E² ∇ε

With the relative permittivity interpolated using the Level Set function as:

εr = er_liq + (1-er_liq) phils

With phils = 0 in the liquid and phils = 1 in air (as proposed in the Taylor Cone Model). Thus, the corresponding force components should therefore be:

Fes_r = 0.5(es.Er^2+es.Ez^2)epsilon0_const(er_liq-1)philsr

Fes_z = 0.5(es.Er^2+es.Ez^2)epsilon0_const(er_liq-1)philsz

These expressions are dimensionally consistent and correspond to volumetric forces expressed in N/m³.

Could you please confirm whether the original expressions contain an error or whether a specific formulation or assumption justifies their use?

Since these forces directly influence the deformation of the liquid–air interface and the resulting Taylor cone geometry, such an error could potentially affect the simulation results.

Thank you in advance for your clarification.

Best regards,

EMAT webinar example reproduction

Fri, 09 Oct 2026 19:44:57 +0000

Hi everyone,

I am trying to reproduce the electromagnetic acoustic transducer example presented in this webinar : https://www.comsol.com/video/modeling-nondestructive-testing-methods-in-comsol-multiphysics I do not have access to the comsol file so I have reproduced the file from the video. The results are not adequate and I do not really know what is causing that : the solid mechanics quantities such as displacement are 0 everywhere. I am not used to multiphysics problems in comsol.

I have attached my file if needed.

Sarah

Using material properties for parameters, variables, functions

Fri, 09 Oct 2026 09:11:23 +0000

Hello,

I use a 2D model with AC/DC module and Magnetic Field interface. I would like to use some material properties to define the geometry, clearly I wish to use the skin depth to define the dimensions of a coil. What I usually do is copy the material property (here copper) in the parameters of Global Definition so I can also define delta = 1/sqrt(pi * f * mu * sigma). Is there a way to get mu and sigma directly from the material without having to create some fixed parameters ? I am open to any solutions that allow using delta in the geometry.

Thank you :)

Sarah

Same transitional flow model runs fine in COMSOL 6.1 but crashes in COMSOL 6.3

Thu, 08 Oct 2026 02:16:46 +0000

Hi everyone, I’m running into a version-related issue with COMSOL. A transitional flow model that simulates successfully in COMSOL 6.1 crashes when simulated in COMSOL 6.3. The geometry, mesh, physics settings, and solver configuration are essentially the same; the main difference is the software version. The computer configuration is as follows： CPU: Intel(R) Xeon(R) Gold 6246R CPU @3.4GHz GPU: NVIDIA RTX A6000

How understand flux vs time plot when it shows negative values

Wed, 07 Oct 2026 14:51:07 +0000

The study involving TDS using 5.5 and 6.4 showed oppisite pattern of diffusion plot. and the plot chnaged from negative to positive. I need suggestions in understanding the both the plots.

How can you manage save of 2D/3D solutions independently of the probes?

Mon, 05 Oct 2026 14:57:32 +0000

Hello,

In 6.4 release, when solving a time-dependent problem, I simply want to save a few 2D/3D solutions (for example, range(0, (t3-0)/3, t3)), but for the probes, I want to get multiple time points to achieve much greater accuracy (for example: range(t1, 0.01, t3)). I’m not sure what to enter in the “Time Dependent Study” section and the “Time-Dependent Solver” section.

I haved tried :

In "Time Dependent Study" -> "Study Settings" -> "Output times" set to range(0, (t3-0)/3, t3) -> "Results while solving" -> "Update" set to Time steps taken by solver for Probes

In "Time-Dependent Solver" -> "General" -> "Defined by study step" set to "User defined" -> "General" -> "Output times" set to range(t1, 0.01, t3)

But with this, 2D/3D solutions times & probes come from range(t1, 0.01, t3) (while I was hoping that 2D/3D solutions times come from range(0, (t3-0)/3, t3))

Thank you for your help

Best regards,

Inverted mesh elements during snap-back of a snap-through structure with stiff shutters

Sat, 03 Oct 2026 17:23:12 +0000

Hello, I am modeling a 2D plane-strain transient thermo-mechanical snap-through structure in COMSOL Multiphysics 6.3. The structure consists of a curved soft beam with a thermally contracting active layer. Heating causes the beam to snap through. Two long and relatively stiff shutters are attached to small soft silicone pads/protrusions on the beam. After snap-through, the shutters block the incident light, the structure cools, and eventually snaps back. The main problem occurs during snap-back. The computation becomes extremely slow, the time step decreases dramatically, and COMSOL reports inverted mesh elements. The inverted elements are consistently located near the connection between the stiff shutter base and the soft pad underneath it. The soft beam and pads are modeled as silicone with a Young's modulus of approximately 2 MPa. The shutter is much stiffer and relatively thin. Geometric nonlinearity is enabled and a time-dependent solver with Generalized-alpha time stepping is used. I have tried several approaches: 1. Assembly + identity pair + compliant thin layer between the pad and shutter. I also reduced the shutter Young's modulus to approximately 0.5 GPa. This improved convergence and prevented immediate mesh inversion, but the computation became extremely slow. About two snap-through/snap-back cycles required approximately 21 hours. 2. Different geometries, including attaching the shutter directly to the beam and attaching it through a small protrusion/pad. The problem still occurs near the shutter root. 3. Local mesh refinement and different mesh configurations near the shutter/pad interface. 4. Reducing the maximum time step around the snap-through and snap-back events. 5. Rigid/stiff shutter modeling and rigid-flexible connections. Large local deformation still develops in the soft material near the shutter root during snap-back. My main questions are: - Is this inverted-element problem more likely caused by the geometry/interface design, the mesh, or the nonlinear solver/time stepping? - What is the recommended way in COMSOL to connect a very stiff and thin shutter to a very soft silicone substrate undergoing large deformation? - Would a rigid domain with a compliant connection/thin elastic layer be more appropriate? - Would automatic remeshing or an ALE approach be suitable for this type of snap-through/snap-back problem? - Are quadrilateral elements or another local meshing strategy preferable to triangular elements in the highly deformed shutter-root region? - Are there solver settings that can handle this instability more efficiently without forcing the time step to become extremely small? I have attached figures showing the overall structure and the location of the inverted elements during snap-back. Any suggestions on the geometry, interface modeling, mesh, or nonlinear solver settings would be greatly appreciated. Thank you.

Piezoelectric Ultrasonic Cleaning Tank

Sat, 03 Oct 2026 09:27:16 +0000

I am currently studying a piezoelectric ultrasonic cleaning tank operating at approximately 100 kHz. I would like to use COMSOL Multiphysics to establish a fully coupled piezoelectric-structural-acoustic model. However, I have encountered some difficulties in setting up the model. So far, I have only found examples involving ultrasonic wave propagation in air, and I have not been able to find a case that closely matches my application. I would be very grateful for any help or suggestions. If anyone could share a similar COMSOL .mph example model, relevant paper, tutorial, or modeling recommendation, I would greatly appreciate it. The model mainly consists of the following components: （1）A circular PZT-4 piezoelectric ceramic disk with a diameter of 38 mm; （2）The PZT thickness is the design variable, and the current optimized value is approximately 4.130 mm; （3）The PZT disk is bonded to the outer surface of the bottom of a cylindrical 316L stainless-steel tank; （4）The thickness of the 316L stainless-steel tank bottom is approximately 0.5 mm; （5）The medium inside the tank is water; （6）The PZT is polarized through its thickness, and a harmonic voltage is applied across its top and bottom electrodes; （7）The target operating frequency is approximately 100 kHz.