Thermal Performance Analysis for Multiple Heat Source Power Devices

The existing iris recognition module is realized by assembly, which has large volume, high power consumption. The iris recognition module does not conform to the light and thin development trend of integrated circuits. Therefore, the industry is considering building a new iris recognition module from the bare chip and micro interconnect technology. The new module integrates a number of bare chips and passive devices in a limited space, and its thermal performance becomes more complex. It is necessary to study its performance systematically. In this paper, the thermal performance of the iris recognition module is systematically studied by the finite element method, and the influence of the thermal power of the chip, the thermal conductivity of the material and the area of PCB on the temperature and thermal resistance of the package are discussed. The results show that the thermal conductivity of chip material, the thermal power consumption of chip and the area of PCB have significant influence on packaging junction and thermal resistance of package. Package junction temperature and thermal resistance first decrease rapidly with the heat transfer coefficient of the package material, and then gradually tends to be horizontal, The effect of PCB area on the thermal performance of packaging is similar to that of the loading material, and the thermal dissipation power of the package is linearly increasing with the junction temperature of the package, and it has a horizontal linear relationship with the thermal resistance of the package.

This paper presents the results of thermal performance and mechanical reliability co-design of flip chip devices by a comprehensive evaluation of package structure and material effects. The study provided valuable insights that can assist to identify potential package solutions and enhancement options by considering process, materials, thermal performance and mechanical reliability. With concurrent thermal and mechanical analysis, the thermal trends obtained from this study can be used to enhance the selection of thermal options and the reliability insights gained allowed further mechanical optimizations to identified solutions. The study evaluates both the larger sized FC-BGA and smaller sized FC-CSP using selected production, development and potential devices. A total of 6 FC-BGA and 5 FC-CSP test vehicles were selected for the study. The UTAC-patented XP (eXtra Performance) embedded heat spreader was also assessed and benchmarked against the other test vehicles. Thermal performance analysis, detailed package level stress and warpage analysis were conducted for all the identified test vehicles. For both FC-BGA and FC-CSP devices, analysis results showed that the bare die structure has the highest warpage and highest junction-to-ambient thermal resistance. The addition of mold compound is able to improve warpage for small die FC-BGA packages. However, mold compound results in insignificant warpage improvements when die-topackage ratio is large, such as in the FC-CSP. Concurrent thermal analysis shows that mold compound slightly enhances the thermal performance of both FC-BGA and FC-CSP devices under no/low wind velocities. Heat spreaders or heat sinks are comparatively more effective thermal enhancement solutions. The effects of heat spreaders were analyzed using several different package structures. Other than the thermal benefits reaped, heat spreaders brought about significant warpage control. Especially in the case of XP, the combined effect of the mold compound and the embedded heat spreader remarkably reduced warpage even in package with large dieto-package ratio. However, stress analysis showed a 10-25% increase in die stress for both small and large die packages when the heat spreader is used. With the recent interest and migration to the use of moldable underfill material (MUF), its performance was also benchmarked against the conventional capillary underfill (CUF) and mold compound. Thermal analysis results shows that MUF results in minor thermal enhancements compared to the capillary underfill (CUF). Mechanical analysis results showed that the MUF improves package coplanarity when the package exhibited smiling warpage behaviour at room temperature. The shift in critical die and underfill stresses was also observed with the change in material set. The thermal performance and mechanical reliability costudy adopted a holistic approach that obtained the trends and insights learnt that enabled informed choices to be made in materials selection and identification of potential packages. The approach and the insights obtained are thus presented in this paper.

Design and the transient thermal control performance analysis of a novel PCM-based active-passive cooling heat sink

Evolving system needs require wide bandgap (WBG) materials for specific power and voltages SiC and GaN for high-power switching applications Higher efficiency, thermal performance, breakdown voltage, switching speeds, lower conduction losses, and improved reliability WBG materials enable novel device applications EVs -longer driving ranges and faster charging Renewable energy -higher efficiency for solar inverters and wind turbine converters Telecommunications -faster speeds enhance RF amplifiers and 5G 2 Increasing performance

The low thermal conductivity of PCM limits the thermal performance of heat storage devices, hindering their widespread application in engineering. To address this challenge, this paper focused on the fin design of a horizontal triplex-tube latent heat storage device. A novel V-shaped fin with a secondary arrangement is proposed. Numerical simulation is employed to investigate the effects of fin angle, fin length, and heat transfer fluid temperature on the thermal performance of the storage system. Moreover, the fin parameter is optimized by the response surface method. The results demonstrate that, compared to traditional rectangular fins, both the primary and secondary V-shaped fins can significantly enhance the thermal performance. The secondary V-shaped fin has the most significant effects, reducing the melting time of the PCM by 48.5%, and increasing the average heat storage rate by 83.46%. Additionally, the thermal performance of the heat storage unit exhibits a trend of initially increasing and then decreasing with the increase of fin angle and length, suggesting the existence of optimal structural parameters. Consequently, the optimized secondary V-shaped fin reduces the melting time by 52.9% and increases the average heat storage rate of phase change materials by 104.48%.

Gallium nitride (GaN) power devices are employed in an increasing number of applications thanks to their excellent performance. Nevertheless, their potential for cryogenic applications, such as space, aviation, and superconducting systems, has not yet been fully explored. In particular, little is known on the device performance below liquid nitrogen temperature (77 K) and the behavior of popular GaN architectures such as gate injection transistor and Cascode below room temperature has not yet been reported. Most importantly, it is still unclear how the different device loss contributions, i.e., conduction, soft- and hard-switching losses, change at cryogenic temperatures. In this letter, we investigate and compare the performance of four GaN commercial power devices in a wide temperature range between 400 and 4.2 K. All of the tested devices can successfully operate at cryogenic temperatures with an overall performance improvement. However, different GaN HEMT technologies lead to significant variations in device gate control and loss mechanisms, which are discussed based on the device structure. The presented results prove the promising potential of the GaN technology for low-temperature applications and provide precious insights to properly design power systems operating under cryogenic temperatures and maximize their efficiency.

Superjunction (SJ) is one of the most innovative concepts in the field of power semiconductor devices and is often referred to as a "milestone" in power MOS. Its balanced charge field modulation mechanism breaks through the strong dependency between the doping concentration in the drift region and the breakdown voltage V B in conventional devices. This results in a reduction of the trade-off relationship between specific on-resistance R on,sp and V B from the conventional R on,sp∝V B 2.5 to R on,sp∝W∙V B 1.32, and even to R on,sp∝W·V B 1.03. As the exponential term coefficient decreases, R on,sp decreases with the cell width W, exhibiting a development pattern reminiscent of "Moore’s Law". This paper provides an overview of the latest research developments in SJ power semiconductor devices. Firstly, it introduces the minimum specific on-resistance R on,min theory of SJ devices, along with its combination with special effects like 3-D depletion and tunneling, discussing the development of R on,min theory in the wide bandgap SJ field. Subsequently, it discusses the latest advancements in silicon-based and wide bandgap SJ power devices. Finally, it introduces the homogenization field (HOF) and high-K voltage-sustaining layers derived from the concept of SJ charge balance. SJ has made significant progress in device performance, reliability, and integration, and in the future, it will continue to evolve through deeper integration with different materials, processes, and packaging technologies, enhancing the overall performance of semiconductor power devices.

Premium power park (PPP) provides corresponding power supply for different levels of load using multiple PQDs, which is an effective measures to solve power quality problem. Existing international and regional or national power quality standards was given firstly. Then according to Premium Power Park user's feature, from the power supply capacity, load-sensitive, power quality level requirements etc, designed real-time monitoring systems for power quality, custom power and energy storage device's distribution program, function and performance indicators. To study energy saving of PPP operating with power supply scheme adding PQDs, and satisfy limits of power quality, proposed a an energy saving quantization to meet the Premium Power Park and various user needs. The calculation model show that under the new power supply scheme, energy loss of line and transformer have decreased and supply efficiency of system has been greatly improved.

Optimization of underfloor air distribution systems for data centers based on orthogonal test method: A case study

Due to the performance and cost limitations of commercial power devices, the conventional two-level and three-level dual-active-bridges (DAB), which are subjected to higher device voltage stress, face the challenges of a significant increase in cost and power loss under medium-voltage DC (MVDC) applications. Thus, a four-level nested neutral point-clamped (4L-NNPC) DAB is proposed in this article, where the voltage stress on each power device is reduced to 1/3 DC-link voltage. Compared with the existing three-level and four-level DAB, the proposed converter exhibits a cost and efficiency advantage in MVDC owing to its uniform voltage stress and reduced number of power devices. Subsequently, a capacitor voltage balancing (CVB) method based on modified redundant switching states (MRSS) is designed for the 4L-NNPC-DAB. Due to the independence of the MRSS in each leg, the complexity of the proposed CVB method is reduced compared with the other four-level DAB. Finally, the simulation and experimental results verified that the 4L-NNPC-DAB operates stably and controllably under the proposed modulation. In addition, the effectiveness of the proposed CVB method is verified in steady and dynamic output cases, disturbances of nonideal factors, and reverse operation.

Power switching devices made from wide bandgap (WBG) semiconductors such as Silicon Carbide (SiC) and Gallium Nitride (GaN) have the potential to make transformative impact on electricity infrastructure. However, limited availability, high cost, unproven application-level field-reliability, inaccurate and incomplete datasheets from the manufacturers, and most importantly - lack of trust and true collaboration among the WBG supply chain industries - are severely hindering the large-scale commercialization of WBG power conversion technology. Although SiC power diodes and power MOSFETs are commercially available for voltage ratings up to 1,700 volts from a couple of manufacturers, a careful review of the published literature and commercial product datasheets suggests that performance and reliability of these devices may be severely compromised compared to silicon power devices. For example, limited reported data available for dv/dt, avalanche, and safe-operating area (SOA) parameters of SiC power diodes and MOSFETs are inferior to silicon power devices with identical ratings. This paper presents a simple physics-based analysis of power-handling capability of WBG power devices, and explains the possible causes of limited performance and reliability of SiC power devices.

Multi-objective optimization of cost and thermal performance of double walled carbon nanotubes/water nanofluids by NSGA-II using response surface method

Optimization Investigation of Bionic Fin Structure by Experimental and Numerical Modelling

Most of the existing power chips are connected by wire bonding or copper sheet welding. With the development of high performance, small size, modularity and high power density of power devices, the packaging method starts to develop towards FO(Fan-out)-based packaging technology. This scheme can be designed with complex line layout and flexible metal shape linkage method. And it is a high efficiency package method with low parasitic capacitance, inductance, very low <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${\mathrm{R}_{\text{dson}}}$</tex> and excellent heat dissipation at high frequency. The thermal stress problem in reflow soldering is a key research object in device development, and this paper mainly focuses on the research of DFN3030 product structure based on FO package thermal stress. Using finite element software to establish a three-dimensional model, the main factors affecting the metal shape of the chip surface, copper thickness, and plastic sealing material thickness are simulated and analyzed. The simulation is used to determine the relationship between different factors affecting thermal stress, and two different structural solutions are selected for sample verification to confirm whether the simulation structure matches the actual product result trend. Through the actual product reliability verification, it is confirmed that the thermal stress trend of the actual product matches with the theoretical results. And through the sample verification, the product with FO package DFN3030 meets the reliability requirements of MSL3, TC 500cycles@(-55~125 °C), PCT 96H@(120 °C, 100%RH), HTSL 1000H@150°C, THB 1000H@(85 °C, 85%RH).

To ensure safe and reliable operation, ignition performance in propulsion and power devices needs to be thoroughly assessed. Reduced order models (ROMs) for ignition have gained increasing attention, given that first-principles models are restricted by immense computational costs that preclude rapid assessment for the design purpose. Currently, flame self-propagation is generally neglected in the ROM descriptions of ignition process and the impact on the flame front dynamics as well as the ignition probability map is not clear for low swirl or jet flames which are of interest for industrial applications. In this study, an empirical model for flame self-propagation is proposed to augment the capability of Lagrangian flame particle tracking method, a ROM model to predict ignition probability based on nonreacting flow field. The model adopts the classic scaling law of turbulent flame speed together with fuel gradient correction and flame self-propagation to mimic the edge flame dynamics during the ignition process. The model performances in terms of flame front dynamics and ignition probability map are quantified in a turbulent nonpremixed methane-air jet flame. Results reveal that only with flame self-propagation, the flame particle tracking can well capture the transient evolution of the leading flame front as observed in experiments. It is found that the predicted ignition probability map agrees well with experimental data with high ignition probability around the vicinity of the stoichiometric region at the downstream axial distance of 6 to 40 times the jet diameter. This study illustrates the importance to account for flame self-propagation to correctly predict ignition probability in jet dominant nonpremixed flames.