Influence of Materials and Packaging Solutions on Thermal Behaviour of Power Modules

Nowadays, designing ever more efficient power modules requires complex materials and more innovative methodologies. To significantly reduce the lead time of the devices and decrease the costs, especially during the prototyping and the testing phases, a Finite Element Analysis (FEA) can be the simplest way to deal with a matrix of parameters to be studied on a single setup. In this work, a thermal characterization is addressed to a stationary simulation using the COMSOL Multiphysics® software, coupling the Heat Transfer Module and the CFD Module. The study is applied to two types of power modules with different technologies, one with Direct Bonded Copper (DBC) substrate and the other one with Insulated Metal Substrate (IMS). An experimental phase follows in order to test the most performing module. A DBC module is composed by (bottom-up) a substrate (copper base, an alumina insulating layer, copper top layer with a specific electrical layout), soldering layers, the dice, the metallic pins, a covering insulating gel and an external protective box. The IMS modules are equal, except for the substrate made up by (bottom-up) a metal base (copper or aluminium), a polymer with ceramic fillers as insulating layer and a copper top layer with the same electrical layout of DBC. The experimental setup used to test real devices is composed by an aluminium water heatsink with a macroscopical copper plate on the top, separated by a thermal grease layer. The device is then mounted on the copper plate with a defined thermal grease layer in between. The geometry considered in the simulation reproduces accurately this experimental setup. The Heat Transfer Module is set to dissipate about 110 W per die. Air natural convection is neglected since it contributes only marginally to the exchange process. This has been assessed with a specific simulation that allows to fix the total insulating condition on the external boundaries, so that only conductive phenomena are considered at this point. The CFD Module is responsible of the water flux entering the heatsink, while the Multiphysics captures the non-isothermal behaviour of the fluid as it flows inside the heatsink. The mesh incorporates different element sizes, depending on the layers thickness. As a result, the FEA solution, provided by COMSOL Multiphysics®, is mostly in accordance with the experimental data. For DBC module, also the packaging is investigated. Different solutions, such as Vacuum Potting Gel (VPG), are applied to the standard module, analysing thermal resistance and heat dissipation. As an example, the VPG solution consists in filling a protective plastic case with a silicone dielectric gel. The layers disposition is precisely the one described in the DBC section above. The modules are imported in the software and placed upon the testing setup already in use for the previous part. The simulations return interesting insight in the thermal behaviour of the modules

Static and thermal FE analysis of a Flexible Electronic BOard (FEBO) prototype and the characterization of its innovative materials

An FE model of an experimental flexible electronic board was built to determine its performance in terms of mechanical and thermal distortions, heat and transient thermal flow, thereby detecting critical issues and identifying opportunities for improvement. Commercial sensors were connected to the flexible board (100x40x2mm), which was based on a commercial thermoplastic polyurethane (TPU), with a PEDOT-based conductive resin trapped in a PEGDA network, a biocompatible polymer. Three thermal loads (ΔT=175°C, ΔT=100°C, ΔT=50°C) were applied which revealed critical stresses for high ΔTs but at ΔT=50°C only the connectors had a critical σvm, while for ΔT=50°C + 1mm displacement a critical strain value occurred in one area of the substrate. Heat transient analysis and overheating simulations were performed to determine the heat flow behavior for the photodiode and accelerometer. FE analyses allow more studies to be undertaken to improve material properties and suggest redesign activities for similar concept demonstrators. The funds of the European Union and the Piedmont Region, and agreements with the most important players in SBE (Simulation Based Engineering) software sales and services, allowed the authors (ITACAe srl, Proplast, and Politecnico di Torino) to conduct industrial research and experimental development together with manufacturers and users of innovative technologies to identify, study and optimize the design parameters of the board while simultaneously contributing to its technological development

Silicon and Silicon Carbide Recrystallization by Laser Annealing: A Review

Modifying material properties within a specific spatial region is a pivotal stage in the fabrication of microelectronic devices. Laser annealing emerges as a compelling technology, offering precise control over the crystalline structure of semiconductor materials and facilitating the activation of doping ions in localized regions. This obviates the necessity for annealing the entire wafer or device. The objective of this review is to comprehensively investigate laser annealing processes specifically targeting the crystallization of amorphous silicon (Si) and silicon carbide (SiC) samples. Silicon finds extensive use in diverse applications, including microelectronics and solar cells, while SiC serves as a crucial material for developing components designed to operate in challenging environments or high-power integrated devices. The review commences with an exploration of the underlying theory and fundamentals of laser annealing techniques. It then delves into an analysis of the most pertinent studies focused on the crystallization of these two semiconductor materials

Organic Electrochemical Transistor Immuno-Sensors for Spike Protein Early Detection

The global COVID-19 pandemic has had severe consequences from the social and economic perspectives, compelling the scientific community to focus on the development of effective diagnostics that can combine a fast response and accurate sensitivity/specificity performance. Presently available commercial antigen-detecting rapid diagnostic tests (Ag-RDTs) are very fast, but still face significant criticisms, mainly related to their inability to amplify the protein signal. This translates to a limited sensitive outcome and, hence, a reduced ability to hamper the spread of SARS-CoV-2 infection. To answer the urgent need for novel platforms for the early, specific and highly sensitive detection of the virus, this paper deals with the use of organic electrochemical transistors (OECTs) as very efficient ion-electron converters and amplifiers for the detection of spike proteins and their femtomolar concentration. The electrical response of the investigated OECTs was carefully analyzed, and the changes in the parameters associated with the transconductance (i.e., the slope of the transfer curves) in the gate voltage range between 0 and 0.3 V were found to be more clearly correlated with the spike protein concentration. Moreover, the functionalization of OECT-based biosensors with anti-spike and anti-nucleocapside proteins, the major proteins involved in the disease, demonstrated the specificity of these devices, whose potentialities should also be considered in light of the recent upsurge of the so-called "long COVID" syndrome

3D-Printable Dielectric Transmitarray With Enhanced Bandwidth at Millimeter-Waves

In this paper, a three-layer dielectric structure is presented as innovative unit-cell element for transmitarray (TA) antennas with enhanced bandwidth. It consists of a central layer, with a varying size square hole, used to compensate the phase of the incident field and located between two other identical layers with linearly tapered square holes, acting as matching circuits. The effectiveness of this unit-cell is demonstrated by the numerical and the experimental results here presented. As a first step, three different TAs with increasing size are designed and simulated: their 1-dB gain bandwidth, centered at 30 GHz, varies from the 30.9% of the smallest configuration, having size of $10\lambda _{0}\times 10\lambda _{0}$ , to the 17.5% of the $20\lambda _{0}\times 20\lambda _{0}$ TA. A slightly modified unit-cell is then designed, with the aim of realizing a prototype with an additive manufacturing (AM) technique. A 3D-printed dielectric TA with a size of $15.6\lambda _{0}\times 15.6\lambda _{0}$ has been manufactured and experimentally characterized. The measured prototype shows excellent performances, achieving a 1-dB gain bandwidth of 21.5%: these results prove the enhanced features of the introduced unit-cell and demonstrate the TA feasibility with AM techniques

Single‐Step 3D Printing of Silver‐Patterned Polymeric Devices for Bacteria Proliferation Control

This work describes the fabrication of silver-patterned polymeric devices via light-based 3D printing methods from a tailored resin. An acrylate resin containing silver nitrate (AgNO3) as a silver precursor is employed to generate silver nanoparticles (AgNPs) through the in situ reduction of the metallic salt. The silver-based resin is processed through a customized stereolithography SL-3D printing to fabricate structures with silver-patterned surfaces. This customized SL-printer (emitting at 405 nm) offers the possibility of adjusting the machine settings during the printing process allowing for AgNPs to be selectively generated by modifying the laser settings during the 3D printing step. Thus, the resin photopolymerization and the photoinduced formation of AgNPs-based strands can be sequentially achieved during the same printing process with the same light source and using the same printable resin. The fabricated silver-patterned devices exhibit different surface features that might be exploited in systems working in a marine environment to control biofilm proliferation. As a proof-of-concept, the antimicrobial behavior of the silver-based 3D printed device is tested against environmental bacterial mixed communities via UV–vis spectroscopy and evaluating the absorbance change. Further tests, however, would be needed to reinforce the evidence of the bacteria behavior on the silver-patterned 3D printed devices

Rapid prototyping of 3D Organic Electrochemical Transistors by composite photocurable resin

Rapid Prototyping (RP) promises to induce a revolutionary impact on how the objects can be produced and used in industrial manufacturing as well as in everyday life. Over the time a standard technique as the 3D Stereolithography (SL) has become a fundamental technology for RP and Additive Manufacturing (AM), since it enables the fabrication of the 3D objects from a cost-efective photocurable resin. Eforts to obtain devices more complex than just a mere aesthetic simulacre, have been spent with uncertain results. The multidisciplinary nature of such manufacturing technique furtherly hinders the route to the fabrication of complex devices. A good knowledge of the bases of material science and engineering is required to deal with SL technological, characterization and testing aspects. In this framework, our study aims to reveal a new approach to obtain RP of complex devices, namely Organic Electro-Chemical Transistors (OECTs), by SL technique exploiting a resin composite based on the conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and the photo curable Poly(ethylene glycol) diacrylate (PEGDA). A comprehensive study is presented, starting from the optimization of composite resin and characterization of its electrochemical properties, up to the 3D OECTs printing and testing. Relevant performances in biosensing for dopamine (DA) detection using the 3D OECTs are reported and discussed too

Effect of Volatile Organic Compounds Adsorption on 3D-Printed {PEGDA}:{PEDOT} for Long-Term Monitoring Devices

We report on the preparation and stereolithographic 3D printing of a resin based on the composite between a poly(ethylene glycol) diacrylate (PEGDA) host matrix and a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) filler, and the related cumulative volatile organic compounds' (VOCs) adsorbent properties. The control of all the steps for resin preparation and printing through morphological (SEM), structural (Raman spectroscopy) and functional (I/V measurements) characterizations allowed us to obtain conductive 3D objects of complex and reproducible geometry. These systems can interact with chemical vapors in the long term by providing a consistent and detectable variation of their structural and conductive characteristics. The materials and the manufacture protocol here reported thus propose an innovative and versatile technology for VOCs monitoring systems based on cumulative adsorption effects

Additive Manufacturing for printed electronics and integrated systems

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