Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103141
J. Schicker, T. Arnold, C. Hirschl, A. Iravani, Martin Kraft
The deformation of large thin uncoated silicon wafers without remaining intrinsic misfit stresses resting on a ring is investigated. We use both, Finite Element simulations and THz tomography mapping. Specific attention is given the scaling of the warping for increasing slenderness of those wafers. We follow the approach of starting with a known solution for a compact wafer and increase the slenderness, i.e. increase the radius and decrease the thickness, using simulation models. Then, we measure the warping by THz mapping for some slender wafers and compare the data to simulation results. We compare the maximum warpage for given loadings and we compare the deflected shapes. Due to the geometric ratio radius/thickness of over 1000;1 and the anisotropic material behaviour, simulations can only be done effectively using shell element modelling of a spatial plate. And due to large warpages in the order of 10 times of the thickness, only incremental update Lagrange nonlinear calculations give reliable results. Simulations using the available shell elements overestimate slightly the values measured by tomography, but still yield acceptable values with errors less than 10% for very slender wafers and below for more compact ones. For invariable loading conditions, a logarithmic scaling function gives an acceptable estimate for the maximum warpage for increasing slenderness. An additional important observation was that the warpage of thin wafers is heavily affected by the size of the contact radius of a weight.
{"title":"Simulation of the deformation behaviour of large thin silicon wafers and comparison with experimental findings","authors":"J. Schicker, T. Arnold, C. Hirschl, A. Iravani, Martin Kraft","doi":"10.1109/EUROSIME.2015.7103141","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103141","url":null,"abstract":"The deformation of large thin uncoated silicon wafers without remaining intrinsic misfit stresses resting on a ring is investigated. We use both, Finite Element simulations and THz tomography mapping. Specific attention is given the scaling of the warping for increasing slenderness of those wafers. We follow the approach of starting with a known solution for a compact wafer and increase the slenderness, i.e. increase the radius and decrease the thickness, using simulation models. Then, we measure the warping by THz mapping for some slender wafers and compare the data to simulation results. We compare the maximum warpage for given loadings and we compare the deflected shapes. Due to the geometric ratio radius/thickness of over 1000;1 and the anisotropic material behaviour, simulations can only be done effectively using shell element modelling of a spatial plate. And due to large warpages in the order of 10 times of the thickness, only incremental update Lagrange nonlinear calculations give reliable results. Simulations using the available shell elements overestimate slightly the values measured by tomography, but still yield acceptable values with errors less than 10% for very slender wafers and below for more compact ones. For invariable loading conditions, a logarithmic scaling function gives an acceptable estimate for the maximum warpage for increasing slenderness. An additional important observation was that the warpage of thin wafers is heavily affected by the size of the contact radius of a weight.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"818 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127909901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103117
M. Lenczner, Bin Yang, M. Abaidi, A. Bontempi, D. Teyssieux, B. Koehler, P. Janus
We present a multi-scale model of a probe for scanning thermal microscopy. The probe is built by microfabrication techniques. In active mode, it is supplied by a source of harmonic and/or continuous current and the tip temperature is measured after a lock-in amplifier. The model distinguishes two time scales and two space scales. Simulation results show the potential of the model in terms of accuracy and computation speed and they are compared to experimental results. Finally, a temperature control law constructed from this model is stated.
{"title":"Modeling and model-based control of temperature in an SThM probe","authors":"M. Lenczner, Bin Yang, M. Abaidi, A. Bontempi, D. Teyssieux, B. Koehler, P. Janus","doi":"10.1109/EUROSIME.2015.7103117","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103117","url":null,"abstract":"We present a multi-scale model of a probe for scanning thermal microscopy. The probe is built by microfabrication techniques. In active mode, it is supplied by a source of harmonic and/or continuous current and the tip temperature is measured after a lock-in amplifier. The model distinguishes two time scales and two space scales. Simulation results show the potential of the model in terms of accuracy and computation speed and they are compared to experimental results. Finally, a temperature control law constructed from this model is stated.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121195825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103122
F. Baccar, H. Arbess, L. Théolier, S. Azzopardi, E. Woirgard
This work presents a methodology using mixed-mode simulation with TCAD Sentaurus to model, analyze, and optimize the representation of the Deep Trench Termination Diode (DT2) without increasing the number of nodes and the computation time. Moreover, several convergence problems which can be found for many kinds of simulations have been resolved.
{"title":"New simulation method for Deep Trench Termination diode (DT2) using mixed-mode TCAD sentaurus","authors":"F. Baccar, H. Arbess, L. Théolier, S. Azzopardi, E. Woirgard","doi":"10.1109/EUROSIME.2015.7103122","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103122","url":null,"abstract":"This work presents a methodology using mixed-mode simulation with TCAD Sentaurus to model, analyze, and optimize the representation of the Deep Trench Termination Diode (DT2) without increasing the number of nodes and the computation time. Moreover, several convergence problems which can be found for many kinds of simulations have been resolved.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130827484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103103
N. Vollert, J. Schicker, C. Hirschl, Martin Kraft, J. Pilz
A common challenge in modern multi-physics simulations like FEM is that the more complex the underlying problems become, the more the simulation depends on a range of not or just poorly understood parameters. At the same time, the increase of FEM computing time with the complexity of the underlying problem makes it impossible to explore the whole parameter space with FE simulations. Gaining as much information as possible from a manageable number of runs clearly requires involving some form of Design of Experiments (DOE), referred to as Design of Computer Experiments (DOCE) for simulation studies. In addition to the decision for which parameter sets simulations should be performed, the results of these simulations are used as data for constructing a statistical “metamodel”. By enabling the calculation of any variable of interest from arbitrary parameter sets without having to run new simulations, these metamodels facilitate an efficient exploration of the entire parameter space with optimal effort. Hence, the DOCE approach is indeed capable of expanding and optimizing the possibilities already achievable by simulation studies alone. For demonstrating the method on a relatively simple example, this work is focused on designing and validating a metamodel for calculating linear, one-directional stresses in rectangular monocrystalline (100) samples. It will be shown that the differences between FEM and the metamodel are always smaller than ≈ 4 MPa for different stress states up to a maximum stress of 215 MPa.
{"title":"Designing efficient computer experiments - The step beyond finite element modelling","authors":"N. Vollert, J. Schicker, C. Hirschl, Martin Kraft, J. Pilz","doi":"10.1109/EUROSIME.2015.7103103","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103103","url":null,"abstract":"A common challenge in modern multi-physics simulations like FEM is that the more complex the underlying problems become, the more the simulation depends on a range of not or just poorly understood parameters. At the same time, the increase of FEM computing time with the complexity of the underlying problem makes it impossible to explore the whole parameter space with FE simulations. Gaining as much information as possible from a manageable number of runs clearly requires involving some form of Design of Experiments (DOE), referred to as Design of Computer Experiments (DOCE) for simulation studies. In addition to the decision for which parameter sets simulations should be performed, the results of these simulations are used as data for constructing a statistical “metamodel”. By enabling the calculation of any variable of interest from arbitrary parameter sets without having to run new simulations, these metamodels facilitate an efficient exploration of the entire parameter space with optimal effort. Hence, the DOCE approach is indeed capable of expanding and optimizing the possibilities already achievable by simulation studies alone. For demonstrating the method on a relatively simple example, this work is focused on designing and validating a metamodel for calculating linear, one-directional stresses in rectangular monocrystalline (100) samples. It will be shown that the differences between FEM and the metamodel are always smaller than ≈ 4 MPa for different stress states up to a maximum stress of 215 MPa.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"148 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128443314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103125
A. Yuile, S. Wiese
This paper presents the main observations and results, which have been collected from wave soldering simulations for a lead-free SnAgCu (SAC) solder, in terms of solder shape, penetration and electrical continuity. The simulation models comprise of steady state transitional shear stress transport (SST) melting/solidification models of a single pin-through hole (PTH) configuration on a printed circuit board (PCB). The simulations make use of the commercially available ANSYS Fluent Computational Fluid Dynamics (CFD) solver. The simulation models have been developed to the extent that they are capable of capturing and investigating some of the physically salient features, which dominate wave soldering processes, such that improvements in efficiency/efficacy can potentially be pursued. The simulations also account for the influence of variations in solder material properties, such as viscosity, surface tension and density with respect to temperature. Furthermore, within this paper, areas are highlighted as to how to improve upon and extend the applicability of the models through future development.
{"title":"CFD simulations of wave soldering on through-hole printed circuit assemblies","authors":"A. Yuile, S. Wiese","doi":"10.1109/EUROSIME.2015.7103125","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103125","url":null,"abstract":"This paper presents the main observations and results, which have been collected from wave soldering simulations for a lead-free SnAgCu (SAC) solder, in terms of solder shape, penetration and electrical continuity. The simulation models comprise of steady state transitional shear stress transport (SST) melting/solidification models of a single pin-through hole (PTH) configuration on a printed circuit board (PCB). The simulations make use of the commercially available ANSYS Fluent Computational Fluid Dynamics (CFD) solver. The simulation models have been developed to the extent that they are capable of capturing and investigating some of the physically salient features, which dominate wave soldering processes, such that improvements in efficiency/efficacy can potentially be pursued. The simulations also account for the influence of variations in solder material properties, such as viscosity, surface tension and density with respect to temperature. Furthermore, within this paper, areas are highlighted as to how to improve upon and extend the applicability of the models through future development.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114807826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103138
T. Youssef, E. Woirgard, S. Azzopardi, D. Martineau, R. Meuret
This paper focuses on the thin Nickel layer thicknesses. Thermal and mechanical behaviors of these thin layers in a power module are investigated. An approach is shown in order to present an improved modeling by considering the effect of these thin layers and by reducing time computation.
{"title":"Multi-physics modelling of thin films: Optimization for finite elements simulations tools","authors":"T. Youssef, E. Woirgard, S. Azzopardi, D. Martineau, R. Meuret","doi":"10.1109/EUROSIME.2015.7103138","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103138","url":null,"abstract":"This paper focuses on the thin Nickel layer thicknesses. Thermal and mechanical behaviors of these thin layers in a power module are investigated. An approach is shown in order to present an improved modeling by considering the effect of these thin layers and by reducing time computation.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123472649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103157
A. Wright, S. Koffel, S. Kraft, P. Pichler, J. Cambieri, R. Minixhofer, E. Wachmann
A ball bonding process was simulated over a high-voltage isolation structure. The removal of an inter-dielectric metal crack-stop layer was investigated through 3D simulation. Material properties for the bonded gold ball were obtained using nanoindentation and atomic force microscopy with a methodology from the work of Ma et al. This yielded both elastic and plastic material parameters. The methodology was then evaluated by using the parameters in a nanoindentation simulation. Although the topography simulated only roughly agreed with measurement, the simulated and measured indenter curves closely overlapped. The parameters were then used in the bonding simulation. The deformation of the bond ball was also measured so that the equivalent deformation could be simulated. This was achieved following the incorporation of both ultrasonic motion and softening in the simulation. Two bonding process geometries were then set up: one with the crack-stop layer present and the other without. Both were simulated and the output was applied within a failure theory to evaluate the risk to the isolation oxide.
{"title":"Thermo-mechanical ball bonding simulation with elasto-plastic parameters obtained from nanoindentation and atomic force measurements","authors":"A. Wright, S. Koffel, S. Kraft, P. Pichler, J. Cambieri, R. Minixhofer, E. Wachmann","doi":"10.1109/EUROSIME.2015.7103157","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103157","url":null,"abstract":"A ball bonding process was simulated over a high-voltage isolation structure. The removal of an inter-dielectric metal crack-stop layer was investigated through 3D simulation. Material properties for the bonded gold ball were obtained using nanoindentation and atomic force microscopy with a methodology from the work of Ma et al. This yielded both elastic and plastic material parameters. The methodology was then evaluated by using the parameters in a nanoindentation simulation. Although the topography simulated only roughly agreed with measurement, the simulated and measured indenter curves closely overlapped. The parameters were then used in the bonding simulation. The deformation of the bond ball was also measured so that the equivalent deformation could be simulated. This was achieved following the incorporation of both ultrasonic motion and softening in the simulation. Two bonding process geometries were then set up: one with the crack-stop layer present and the other without. Both were simulated and the output was applied within a failure theory to evaluate the risk to the isolation oxide.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122715178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103156
B. Rivlin, S. Shmulevich, A. Joffe, D. Elata
We show that nonlinear elastic springs can be used to counteract the nonlinearity of electrostatic forces in gap-closing electrostatic actuators. We demonstrate this in two types of devices. In the first, we use a nonlinear spring to extend the stable range of the parallel-plates actuator, and to ensure that the response in this extended range is linear by design. In the second device, we use a nonlinear spring to ensure that beyond what would have been the pull-in point, voltage remains constant and independent of charge. In effect, this second device is a rechargeable mechanical battery.
{"title":"Nonlinear mechanical springs for counteracting nonlinearities in gap-closing electrostatic actuators","authors":"B. Rivlin, S. Shmulevich, A. Joffe, D. Elata","doi":"10.1109/EUROSIME.2015.7103156","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103156","url":null,"abstract":"We show that nonlinear elastic springs can be used to counteract the nonlinearity of electrostatic forces in gap-closing electrostatic actuators. We demonstrate this in two types of devices. In the first, we use a nonlinear spring to extend the stable range of the parallel-plates actuator, and to ensure that the response in this extended range is linear by design. In the second device, we use a nonlinear spring to ensure that beyond what would have been the pull-in point, voltage remains constant and independent of charge. In effect, this second device is a rechargeable mechanical battery.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122839977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103136
K. Brinkfeldt, Michael Edwards, Jonas Ottosson, K. Neumaier, Olaf Zschieschang, A. Otto, E. Kaulfersch, D. Andersson
Effectively removing dissipated heat from the switching devices enables a higher current carrying capability per chip area ratio, thus leading to smaller or fewer devices for a given power requirement specification. Further, the use of SiC based devices has proven to increase the efficiency of the system thereby reducing the dissipated heat. Thermal models have been used to compare SiC power modules. Single and double sided cooling have been simulated. The simulated maximum temperatures were 141 °C for the single sided version and 119.7 °C for the double sided version. In addition, the reliability of a single sided module and thermally induced plastic strains of a double sided module have been investigated. A local model of the wire bond interface to the transistor metallization shows a 30/00 maximum increase in plastic strain during the power cycle. Simulations of the creep strain rates in the die attach solder layer for a power cycling loads also shows a 30/00 increase in creep strain per cycle.
{"title":"Thermo-mechanical simulations of SiC power modules with single and double sided cooling","authors":"K. Brinkfeldt, Michael Edwards, Jonas Ottosson, K. Neumaier, Olaf Zschieschang, A. Otto, E. Kaulfersch, D. Andersson","doi":"10.1109/EUROSIME.2015.7103136","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103136","url":null,"abstract":"Effectively removing dissipated heat from the switching devices enables a higher current carrying capability per chip area ratio, thus leading to smaller or fewer devices for a given power requirement specification. Further, the use of SiC based devices has proven to increase the efficiency of the system thereby reducing the dissipated heat. Thermal models have been used to compare SiC power modules. Single and double sided cooling have been simulated. The simulated maximum temperatures were 141 °C for the single sided version and 119.7 °C for the double sided version. In addition, the reliability of a single sided module and thermally induced plastic strains of a double sided module have been investigated. A local model of the wire bond interface to the transistor metallization shows a 30/00 maximum increase in plastic strain during the power cycle. Simulations of the creep strain rates in the die attach solder layer for a power cycling loads also shows a 30/00 increase in creep strain per cycle.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123342136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-19DOI: 10.1109/EUROSIME.2015.7103113
Jeremy J. Adams, Liangbiao Chen, Xuejun Fan
Moisture plays a critical role in the reliability of electronic devices, especially in the desorption process at reflow temperatures (around 270° C) when severe damages may occur due to high-pressure vapor concerted from condensed moisture. Such pressure-driven vapor flow, however, could not be described by conventional Fick's Law. Furthermore, using conventional Fick's Law for multi-materials always encounters interface discontinuity issues. Therefore, this paper adopts a Convection-Diffusion Model that is able to describe complex desorption behavior in a multi-material media without the discontinuity issue. Both pressure gradient-driven (convection) and concentration-gradient driven (diffusion) moisture transports are considered in the model. To achieve this, absorbed moisture is partitioned into vapor phase and liquid phase (condensed water), with the vapor flux governed by Darcy's Law and the water flux by Fick's Law. Henry's Law is also implemented so that the Fickian term is converted to pressure, resulting in a unified vapor pressure model. The model is applied to analyze a stacked-chip package by two numerical cases: desorption under 2 typical reflow temperature profiles. Numerical validations are also performed to show that the Convection-Diffusion Model can be reduced to traditional Fickian Model and Convection-Only Model as special cases. The numerical results show that the concentration desorption rate is much faster than that of the traditional Fickian diffusion, and somewhat faster than the Convection Model, this results in a much lower pressure in the material. However, the desorption profile with time and the pressures at low temperatures of the different models- the Convection-Only, Diffusion-only and the Convection-Diffusion Model are indistinguishable which can be seen in both reflow profiles. The sensitivity of the CD Model to the gas permeability k and the reflow temperature profiles governs the maximum pressure that is predicted as well as the concentration content.
{"title":"Vapor pressure prediction for stacked-chip packages in reflow by convection-diffusion model","authors":"Jeremy J. Adams, Liangbiao Chen, Xuejun Fan","doi":"10.1109/EUROSIME.2015.7103113","DOIUrl":"https://doi.org/10.1109/EUROSIME.2015.7103113","url":null,"abstract":"Moisture plays a critical role in the reliability of electronic devices, especially in the desorption process at reflow temperatures (around 270° C) when severe damages may occur due to high-pressure vapor concerted from condensed moisture. Such pressure-driven vapor flow, however, could not be described by conventional Fick's Law. Furthermore, using conventional Fick's Law for multi-materials always encounters interface discontinuity issues. Therefore, this paper adopts a Convection-Diffusion Model that is able to describe complex desorption behavior in a multi-material media without the discontinuity issue. Both pressure gradient-driven (convection) and concentration-gradient driven (diffusion) moisture transports are considered in the model. To achieve this, absorbed moisture is partitioned into vapor phase and liquid phase (condensed water), with the vapor flux governed by Darcy's Law and the water flux by Fick's Law. Henry's Law is also implemented so that the Fickian term is converted to pressure, resulting in a unified vapor pressure model. The model is applied to analyze a stacked-chip package by two numerical cases: desorption under 2 typical reflow temperature profiles. Numerical validations are also performed to show that the Convection-Diffusion Model can be reduced to traditional Fickian Model and Convection-Only Model as special cases. The numerical results show that the concentration desorption rate is much faster than that of the traditional Fickian diffusion, and somewhat faster than the Convection Model, this results in a much lower pressure in the material. However, the desorption profile with time and the pressures at low temperatures of the different models- the Convection-Only, Diffusion-only and the Convection-Diffusion Model are indistinguishable which can be seen in both reflow profiles. The sensitivity of the CD Model to the gas permeability k and the reflow temperature profiles governs the maximum pressure that is predicted as well as the concentration content.","PeriodicalId":250897,"journal":{"name":"2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127632343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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