The aim of this work is the thermal modeling of a crate hosting boards with Associative Memories ... more The aim of this work is the thermal modeling of a crate hosting boards with Associative Memories (AMs) designed for the Fast Tracker Trigger (FTK) system of the ATLAS detector at the CERN Large Hadron Collider (LHC). The crate is located in a rack where the cooling can be done with forced air, then the heat transfer is coupled to a non-isothermal fluid flow. Here COMSOL Multiphysics® has been used to investigate if a simplified geometry can give enough accurate results to well design the cooling system of the crate. This will enable the use of COMSOL also to well size the coolers of the rack.
Switched Reluctance Machines (SRM) are considered promising rare-earth free candidates for the ne... more Switched Reluctance Machines (SRM) are considered promising rare-earth free candidates for the next generation electrified vehicles. One of the main drawback of this technology is the need of a large DC-link capacitor to balance the energy transferred back and forth between the DC source and the SRM. There are interesting novel modulations to reduce the current of the DC bus, focused on the capacitor size and cost reduction but leaving aside the thermal analysis and lifetime improvements. Carrying out the required dynamic multi-physics simulations for that purpose becomes highly time consuming and complex, especially when standardized or real driving conditions are needed to be taken into account. This article proposes a simulation methodology, simple to implement and with a relatively low computational cost, to estimate the lifetime of an automotive DC-link capacitor, with the current load it delivers as the starting point. The presented methodology has also been used to validate a...
Optical Methods for Inspection, Characterization, and Imaging of Biomaterials V
Additive manufacturing technologies support the realization of surgical training devices using, t... more Additive manufacturing technologies support the realization of surgical training devices using, typically, photopolymersbased materials. Unfortunately, the material jetting family, able to print a large range of soft and hard polymers, requires expensive machines and materials, which are not always available. On the other hand, vat polymerization fails in the resolution/volume ratio and in the mechanical properties reconstruction. Stereolithographic 3D printers, mostly used in dental surgery, make possible to realize cheap and sustainable models for training activity using only one material, reducing the possibility to obtain different mechanical characteristics. Moreover, the printed objects have to be treated (i.e. curing post-processing) in order to obtain the required performances, that could be preserved for long term storing. The aim of the proposed approach is to assure the surgeons’ skills improvement through bionic-based surgical 3D printed models and smart devices, able to reproduce the same perception of a real surgical activity. We demonstrated how it is possible develop smart devices capable to take into account the same characteristics of different materials (i.e. bone and spongy bone) even if stored for a long time.
In the power electronics market the keywords for an evaluation of fluid heat sinks are "pres... more In the power electronics market the keywords for an evaluation of fluid heat sinks are "pressure drop" and "thermal resistance". Nevertheless the devices that have to be cooled, especially the chips contained in the presspack IGBTs, require a uniform distribution of the surface temperatures in order to withstand a large number of thermal cycles. For this reason the commonplace concept of "thermal resistance" that does not take into consideration the non-uniformities cannot be satisfactory. In this work, because of its complexity, we don't present any new project solutions nor any new prototypes. On the contrary our aim is to show the importance of a complete 3D modeling as a support in the modern designing of fluid heat sinks in order to produce really efficient products.
While still expanding in the microwave arena, GaNbased HEMTs are increasingly making their way in... more While still expanding in the microwave arena, GaNbased HEMTs are increasingly making their way into the field of high-power switching thanks to the material’s advantages in terms of power handling and switching frequency capabilities [1]-[6]. Since high-power applications demand particularly strenuous attention to thermal considerations, thermal modeling of GaN-HEMTs has attracted more and more attention over the last few years, with implications on device design and manufacturing [7], [8], electrical performance [9]-[11], reliability [12], packaging and cooling strategies [13], etc., but mostly in the field of microwave applications and MMICs. However, power converters are complex, hybrid systems, and thermal modeling cannot be confined to the device domain: on the contrary, it has to cover all domains, from the device to the package, the heat sink, and finally the board or boards on which the switches are assembled with passive components, freewheeling diodes, etc. This global app...
In this work, the development of a physics based reliability prediction model for thermo-mechanic... more In this work, the development of a physics based reliability prediction model for thermo-mechanical fatigue of chip solder joints in power converters is illustrated. By this model, the thermo-mechanical stress-strain distribution in the structure is studied by means of Finite Element (FE) method using COMSOL Multiphysics, and the operational life of the solder joints is calculated according to the Coffin-Manson law. As a case study, the estimation of the fatigue life of solder joints in SO8-packaged power MOSFETs is investigated. A stress bench is under design to tune the developed FE model by experimental results.
This work describes a way to apply 3D Finite Element (FE) analysis to the thermal design of power... more This work describes a way to apply 3D Finite Element (FE) analysis to the thermal design of power electronic modules using simplified geometry models of the system components. The method here presented can overcome the problem of solving equation systems with a very high number of Degrees Of Freedom (DOF) due to complex geometry of a power module.
The reliability of solder joints [1,2] is one of the key factors in the determination of the reli... more The reliability of solder joints [1,2] is one of the key factors in the determination of the reliability of the high power density electronic converters, being the solder joints both the mechanical, the electrical, and often the thermal connections between the electronic component and the board in which the component is placed. The main mechanism by which solder joints are damaged is thermal cycling and, in particular, thermo-mechanical stress-strain distribution, which arises from the different thermal expansion coefficients of adjacent materials [3]. The damaging process of solder joints, which falls in the mechanical fatigue behavior of materials, is a Low-Cycle-Fatigue (LCF) process [4] in which the soldering alloy is stressed up into the plasticization area. The simplest law which accounts for LCF-induced degradation is the Coffin-Manson law, or the extended BasquinCoffin-Manson law which accounts for High-Cycle-Fatigue (HCF) as well [5]. Creep [6] is another important factor t...
The aim of this work is to develop a thermal-fluid dynamic FE model, accurate enough to be used f... more The aim of this work is to develop a thermal-fluid dynamic FE model, accurate enough to be used for liquid heatsink design. Power electronic converters such as those for High Energy Physics Experiments (HEPEs) or offshore renewable energy systems, must operate in hostile environment with tight thermal constraints. Due to the high power density, the presence of closed environments and the requirement of non-thermal interaction with other subsystems, a liquid cooling system is mandatory. 3D FEM simulation can be used to analyze thermal fluid dynamic behaviour of those systems and can be a useful support for designing heat sinks optimized for specific applications. The paper ends with a comparison between two different water cold plates conceived on purpose for a particular power electronic converter.
Abstract In this paper, a simple method to describe the effect of Printed Circuit Board (PCB) and... more Abstract In this paper, a simple method to describe the effect of Printed Circuit Board (PCB) and environment on the thermal behavior of packaged devices is addressed. This approach aims at exploiting the benefit of compact thermal models, which are necessarily one-dimensional, together with the advantage of Finite Element (FE) modeling, which retains all the three-dimensional geometrical details, only in the regions of the model that must be accurately described. The main focus is on correct modeling of long power pulses for subsequent electro-thermal and thermo-mechanical analysis at chip level.
Abstract We show results of temperature-dependent reverse-bias step-stressing of normally-off hig... more Abstract We show results of temperature-dependent reverse-bias step-stressing of normally-off high-power GaN FETs. In the range 250–350 K, the stress voltage at which the FETs fail catastrophically does not show a clear temperature dependence, while some correlation is observed with the initial leakage current value. Our results, consistent with other published reports, point to the activation of a deep gate-to-drain leakage path as the responsible for fatal device degradation at large values of the drain–gate reverse bias.
A study is presented aimed at describing phenomena involved in Single Event Burnout induced by he... more A study is presented aimed at describing phenomena involved in Single Event Burnout induced by heavy ion irradiation in SiC Schottky diodes. On the basis of experimental data obtained for irradiation at different energies, electro-thermal FEM is used to demonstrate that the failure is caused by a strong local increase of the semiconductor temperature. With respect to previous studies the temperature dependent thermal material properties were added. The critical ion energy calculated by this model is in agreement with literature experimental results. The substrate doping dependence of the SEE robustness was analyzed, proving the effectiveness of the developed model for device technological improvements.
ABSTRACT The aim of this paper is to show and discuss results of 3D finite-element simulations fo... more ABSTRACT The aim of this paper is to show and discuss results of 3D finite-element simulations for thermal management design with tight constraints taking care of reliability aspects of hybrid power converters. A procedure to obtain simplified but accurate device models has been shown together with experimental validation. The simplified models have been used for converter module modeling. The same procedure has been applied to analyze the thermo-fluid dynamic problem of a whole converter comprising of three modules, inner air and enclosure.
An amendment to this paper has been published and can be accessed via a link at the top of the pa... more An amendment to this paper has been published and can be accessed via a link at the top of the paper.
The aim of this work is the thermal modeling of a crate hosting boards with Associative Memories ... more The aim of this work is the thermal modeling of a crate hosting boards with Associative Memories (AMs) designed for the Fast Tracker Trigger (FTK) system of the ATLAS detector at the CERN Large Hadron Collider (LHC). The crate is located in a rack where the cooling can be done with forced air, then the heat transfer is coupled to a non-isothermal fluid flow. Here COMSOL Multiphysics® has been used to investigate if a simplified geometry can give enough accurate results to well design the cooling system of the crate. This will enable the use of COMSOL also to well size the coolers of the rack.
Switched Reluctance Machines (SRM) are considered promising rare-earth free candidates for the ne... more Switched Reluctance Machines (SRM) are considered promising rare-earth free candidates for the next generation electrified vehicles. One of the main drawback of this technology is the need of a large DC-link capacitor to balance the energy transferred back and forth between the DC source and the SRM. There are interesting novel modulations to reduce the current of the DC bus, focused on the capacitor size and cost reduction but leaving aside the thermal analysis and lifetime improvements. Carrying out the required dynamic multi-physics simulations for that purpose becomes highly time consuming and complex, especially when standardized or real driving conditions are needed to be taken into account. This article proposes a simulation methodology, simple to implement and with a relatively low computational cost, to estimate the lifetime of an automotive DC-link capacitor, with the current load it delivers as the starting point. The presented methodology has also been used to validate a...
Optical Methods for Inspection, Characterization, and Imaging of Biomaterials V
Additive manufacturing technologies support the realization of surgical training devices using, t... more Additive manufacturing technologies support the realization of surgical training devices using, typically, photopolymersbased materials. Unfortunately, the material jetting family, able to print a large range of soft and hard polymers, requires expensive machines and materials, which are not always available. On the other hand, vat polymerization fails in the resolution/volume ratio and in the mechanical properties reconstruction. Stereolithographic 3D printers, mostly used in dental surgery, make possible to realize cheap and sustainable models for training activity using only one material, reducing the possibility to obtain different mechanical characteristics. Moreover, the printed objects have to be treated (i.e. curing post-processing) in order to obtain the required performances, that could be preserved for long term storing. The aim of the proposed approach is to assure the surgeons’ skills improvement through bionic-based surgical 3D printed models and smart devices, able to reproduce the same perception of a real surgical activity. We demonstrated how it is possible develop smart devices capable to take into account the same characteristics of different materials (i.e. bone and spongy bone) even if stored for a long time.
In the power electronics market the keywords for an evaluation of fluid heat sinks are "pres... more In the power electronics market the keywords for an evaluation of fluid heat sinks are "pressure drop" and "thermal resistance". Nevertheless the devices that have to be cooled, especially the chips contained in the presspack IGBTs, require a uniform distribution of the surface temperatures in order to withstand a large number of thermal cycles. For this reason the commonplace concept of "thermal resistance" that does not take into consideration the non-uniformities cannot be satisfactory. In this work, because of its complexity, we don't present any new project solutions nor any new prototypes. On the contrary our aim is to show the importance of a complete 3D modeling as a support in the modern designing of fluid heat sinks in order to produce really efficient products.
While still expanding in the microwave arena, GaNbased HEMTs are increasingly making their way in... more While still expanding in the microwave arena, GaNbased HEMTs are increasingly making their way into the field of high-power switching thanks to the material’s advantages in terms of power handling and switching frequency capabilities [1]-[6]. Since high-power applications demand particularly strenuous attention to thermal considerations, thermal modeling of GaN-HEMTs has attracted more and more attention over the last few years, with implications on device design and manufacturing [7], [8], electrical performance [9]-[11], reliability [12], packaging and cooling strategies [13], etc., but mostly in the field of microwave applications and MMICs. However, power converters are complex, hybrid systems, and thermal modeling cannot be confined to the device domain: on the contrary, it has to cover all domains, from the device to the package, the heat sink, and finally the board or boards on which the switches are assembled with passive components, freewheeling diodes, etc. This global app...
In this work, the development of a physics based reliability prediction model for thermo-mechanic... more In this work, the development of a physics based reliability prediction model for thermo-mechanical fatigue of chip solder joints in power converters is illustrated. By this model, the thermo-mechanical stress-strain distribution in the structure is studied by means of Finite Element (FE) method using COMSOL Multiphysics, and the operational life of the solder joints is calculated according to the Coffin-Manson law. As a case study, the estimation of the fatigue life of solder joints in SO8-packaged power MOSFETs is investigated. A stress bench is under design to tune the developed FE model by experimental results.
This work describes a way to apply 3D Finite Element (FE) analysis to the thermal design of power... more This work describes a way to apply 3D Finite Element (FE) analysis to the thermal design of power electronic modules using simplified geometry models of the system components. The method here presented can overcome the problem of solving equation systems with a very high number of Degrees Of Freedom (DOF) due to complex geometry of a power module.
The reliability of solder joints [1,2] is one of the key factors in the determination of the reli... more The reliability of solder joints [1,2] is one of the key factors in the determination of the reliability of the high power density electronic converters, being the solder joints both the mechanical, the electrical, and often the thermal connections between the electronic component and the board in which the component is placed. The main mechanism by which solder joints are damaged is thermal cycling and, in particular, thermo-mechanical stress-strain distribution, which arises from the different thermal expansion coefficients of adjacent materials [3]. The damaging process of solder joints, which falls in the mechanical fatigue behavior of materials, is a Low-Cycle-Fatigue (LCF) process [4] in which the soldering alloy is stressed up into the plasticization area. The simplest law which accounts for LCF-induced degradation is the Coffin-Manson law, or the extended BasquinCoffin-Manson law which accounts for High-Cycle-Fatigue (HCF) as well [5]. Creep [6] is another important factor t...
The aim of this work is to develop a thermal-fluid dynamic FE model, accurate enough to be used f... more The aim of this work is to develop a thermal-fluid dynamic FE model, accurate enough to be used for liquid heatsink design. Power electronic converters such as those for High Energy Physics Experiments (HEPEs) or offshore renewable energy systems, must operate in hostile environment with tight thermal constraints. Due to the high power density, the presence of closed environments and the requirement of non-thermal interaction with other subsystems, a liquid cooling system is mandatory. 3D FEM simulation can be used to analyze thermal fluid dynamic behaviour of those systems and can be a useful support for designing heat sinks optimized for specific applications. The paper ends with a comparison between two different water cold plates conceived on purpose for a particular power electronic converter.
Abstract In this paper, a simple method to describe the effect of Printed Circuit Board (PCB) and... more Abstract In this paper, a simple method to describe the effect of Printed Circuit Board (PCB) and environment on the thermal behavior of packaged devices is addressed. This approach aims at exploiting the benefit of compact thermal models, which are necessarily one-dimensional, together with the advantage of Finite Element (FE) modeling, which retains all the three-dimensional geometrical details, only in the regions of the model that must be accurately described. The main focus is on correct modeling of long power pulses for subsequent electro-thermal and thermo-mechanical analysis at chip level.
Abstract We show results of temperature-dependent reverse-bias step-stressing of normally-off hig... more Abstract We show results of temperature-dependent reverse-bias step-stressing of normally-off high-power GaN FETs. In the range 250–350 K, the stress voltage at which the FETs fail catastrophically does not show a clear temperature dependence, while some correlation is observed with the initial leakage current value. Our results, consistent with other published reports, point to the activation of a deep gate-to-drain leakage path as the responsible for fatal device degradation at large values of the drain–gate reverse bias.
A study is presented aimed at describing phenomena involved in Single Event Burnout induced by he... more A study is presented aimed at describing phenomena involved in Single Event Burnout induced by heavy ion irradiation in SiC Schottky diodes. On the basis of experimental data obtained for irradiation at different energies, electro-thermal FEM is used to demonstrate that the failure is caused by a strong local increase of the semiconductor temperature. With respect to previous studies the temperature dependent thermal material properties were added. The critical ion energy calculated by this model is in agreement with literature experimental results. The substrate doping dependence of the SEE robustness was analyzed, proving the effectiveness of the developed model for device technological improvements.
ABSTRACT The aim of this paper is to show and discuss results of 3D finite-element simulations fo... more ABSTRACT The aim of this paper is to show and discuss results of 3D finite-element simulations for thermal management design with tight constraints taking care of reliability aspects of hybrid power converters. A procedure to obtain simplified but accurate device models has been shown together with experimental validation. The simplified models have been used for converter module modeling. The same procedure has been applied to analyze the thermo-fluid dynamic problem of a whole converter comprising of three modules, inner air and enclosure.
An amendment to this paper has been published and can be accessed via a link at the top of the pa... more An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Uploads
Papers by Nicola Delmonte