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This paper aims to deduce a set of theory computational formula, and optimize and improve the heat conductivity of vias in printed circuit boards of electrical power apparatus.

The authors adopted numerical simulation and experimental measurement to verify the reliability of this formula.

Research result showed that 0.45 mm was the optimal bore diameter of vias; the conductivity had no obvious improvement when filling material was FR4 or Rogers, but if it was filled with texture of high thermal conductivity like soldering tine, the conductivity would improve a lot; the plating thickness of vias had a greater influence on thermal conductivity.

Through the theory computational formula, this paper studied the influence of aperture of vias, filled materials and thickness of copper plated on vias on thermal conductivity.

This study aims to deal with the numerical investigation of ferrofluid flow and heat transfer inside a right-angle triangular cavity in the presence of a magnetic field. The vertical wall is partially heated, whereas other walls are kept cold. The effects of thermal radiation are included in the analysis. The governing equations including continuity, momentum and energy equations are converted to nondimensional form using viable variables.

Finite element method (FEM)-based simulations are performed using finite element approach to investigate the effects of the volume fraction of ferroparticles (Fe₃O₄), the length of the heating element and the dimensionless numbers including Rayleigh and Hartmann numbers on the streamlines, isotherms and Nusselt number.

It is demonstrated that both horizontal and vertical velocity components increase with the length of the heating element, whereas the dimensionless temperature decreases the heating domain. It is observed that an increase of 10% in the volume fraction of ferroparticles increases Nusselt number more than 12%, and 20% increase in the volume fraction of ferroparticles increases more than 30%, depending upon the length of the heating element.

This is a new study showing the significance of the magnetic nanoparticles for the enhancement of heat transfer rate in a triangular cavity.

The study aims to assess the heater and cooler positional impacts systematically using four different quadrantal cavities filled with hybrid nanofluid, keeping the curved surface adiabatic under the orientated magnetic fields. Both heat transfer and entropy generation analyses are performed for a hybrid nanofluid flow in a quarter circular cavity considering different orientations of magnetic fields. The investigation is focused to assess the heater and cooler positional impacts systematically using four different quadrantal cavities (first to fourth quadrantal cavities), keeping the curved surface always adiabatic. The impacts of pertinent variables like Rayleigh number, Hartmann number and volumetric concentration of hybrid nanofluid on heat transfer characteristics are in consideration with the second law of thermodynamics. The analysis includes the thermal, viscous and magnetic aspects of entropy generation.

After validating against the experimental results, the present work explores numerically following the Galerkin weighted finite element technique. The solution is obtained through an iterative process satisfying the convergence limit of 10⁻⁸ and 10⁻¹⁰ for the maximum residuals and the mass defect, respectively.

It revealed that the mutual exchange of heater-cooler positions on the adjacent straight edges of the quadrant cavity does not have any impact on the flow direction. Although the magnitude of flow velocity enhances, the sidewall plays a decision-making role in the formation of a single circulation vortex. It also shows that thermal entropy production is the main cause behind thermodynamic irreversibility. The second or third quadrantal arrangement could have been opted as the best configuration of the heater-cooler position for achieving superior heat transfer. The Lorentz force plays a great role to moderate the heat transfer process. The maximum entropy generation is located, as expected, at the heating-cooling junction point.

There are plenty of prospects for extension of the present research concept numerically or experimentally, adopting three-dimensional analysis, working fluids, boundary conditions, etc. In fact, the study could be carried out for unsteady or turbulent fluid flow.

As the position of the heated source and cold sink on the enclosure geometry can significantly alter the thermo-fluid phenomena, this kind of analysis is of utmost relevance for the further development of efficient heating/cooling arrangements and proper management of the devices subjected to magnetic field applications. This original contribution could be a potentially valuable source for future research and exploration pertaining to a thermal system or device, like heat exchangers, solar collectors, thermal storage, electronic cooling, food and drying technologies and others.

In the literature, an inadequate number of works have focused on a quadrantal cavity, mostly considering the first quadrant of the circle. However, during practical applications, it is possible that the cavity can take the shape of the other three quadrants too, and the corresponding knowledge on relative performance is still missing. Furthermore, the present investigation includes the existence of magnetic fields at various orientations. The impact analysis of this field-induced Lorentz force on the nanofluid thermal performance is another major contribution from the present work that would enrich the domain knowledge and could be useful for thermal system engineers.

An appreciation of the material from which modern printed circuit board drills are fabricated and an understanding of the salient geometric design features incorporated in such tooling will help those involved with the drilling process in determining optimum operating procedures and in identifying the underlying causes of hole deficiencies.

This study aims to investigate the influence of wall curvature in a semicircular thermal annular system on magneto-nanofluidic flow, heat transfer and entropy generation. The analysis is conducted under constant cooling surface and fluid volume constraints.

The mathematical equations describing the thermo-fluid flow in the semicircular system are solved using the finite element technique. Four different heating wall configurations are considered, varying the undulation numbers of the heated wall. Parametric variations of bottom wall undulation (f), buoyancy force characterized by the Rayleigh number (Ra), magnetic field strength represented by the Hartmann number (Ha) and inclination of the magnetic field (γ) on the overall thermal performance are studied extensively.

This study reveals that the fluid circulation strength is maximum in the case of a flat bottom wall. The analysis shows that the bottom wall contour and other control parameters significantly influence fluid flow, entropy production and heat transfer. The modified heated wall with a single undulation exhibits the highest entropy production and thermal convection, leading to a heat transfer enhancement of up to 21.85% compared to a flat bottom. The magnetic field intensity and orientation have a significant effect on heat transfer and irreversibility production.

Further research can explore a wider range of parameter values, alternative heating wall profiles and boundary conditions to expand the understanding of magneto-nanofluidic flow in semicircular thermal systems.

This study introduces a constraint-based analysis of magneto-nanofluidic thermal behavior in a complex semicircular thermal system, providing insights into the impact of wall curvature on heat transfer performance. The findings contribute to the design and optimization of thermal systems in various applications.

Because many cutting fluids contain hazardous chemical constituents, industries and researchers are looking for alternative methods to reduce the consumption of cutting fluids in machining operations due to growing awareness of ecological and health issues, government strict environmental regulations and economic pressures. Therefore, the purpose of this study is to raise awareness of the minimum quantity lubrication (MQL) technique as a potential substitute for environmental restricted wet (flooded) machining situations.

The methodology adopted for conducting a review in this study includes four sections: establishment of MQL technique and review of MQL machining performance comparison with dry and wet (flooded) environments; analysis of the past literature to examine MQL turning performance under mono nanofluids (M-NF); MQL turning performance evaluation under hybrid nanofluids (H-NF); and MQL milling, drilling and grinding performance assessment under M-NF and H-NF.

From the extensive review, it has been found that MQL results in lower cutting zone temperature, reduction in cutting forces, enhanced tool life and better machined surface quality compared to dry and wet cutting conditions. Also, MQL under H-NF discloses notably improved tribo-performance due to the synergistic effect caused by the physical encapsulation of spherical nanoparticles between the nanosheets of lamellar structured nanoparticles when compared with M-NF. The findings of this study recommend that MQL with nanofluids can replace dry and flood lubrication conditions for superior machining performance.

Machining under the MQL regime provides a dry, clean, healthy and pollution-free working area, thereby resulting the machining of materials green and environmentally friendly.

This paper describes the suitability of MQL for different machining operations using M-NF and H-NF.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2023-0131/

Vertical-cavity surface-emitting laser (VCSEL) is a high-performance semiconductor device made of unique epitaxial layers grown on n-type GaAs or InP substrates. The VCSEL’s thermal resistance, Rth, is an essential metric that reflects its thermal properties and dependability. The purpose of this paper is to develop packaging for 1 mm² VCSEL chips made of a variety of materials, such as ceramic, lead frame and printed circuit board (PCB)-based packaging, as well as provide an idea or design that can withstand and perform well in terms of Rth and heat dissipation during operation. SolidWorks 2017 and AutoCAD Mechanical 2017 software were used to publish all thoughts and ideas, including the size dimensions (x, y and z) and material choices for each package.

Following the modelling and material selection, the next step is to use the Ansys Mechanical Structural FEA Analysis software to simulate all packaging for Rth and determine which packaging produced the best result, therefore, determining the heat dissipation for each packing. All parameters were used based on the standard cleanroom requirement for the industrial manufacturing backend process, where the cleanroom classification is 10,000 particles (ISO 7). The results demonstrated that the ceramic and lead frame provided good Rth values of 7.3 and 7.0 K/W, respectively, when compared to the PCB, which provided more than 80 K/W; thus, the heat dissipation for PCB packaging also increased.

As a result of the research, it was determined that ceramic and lead frame packaging are appropriate and capable of delivering good Rth and heat dissipation values when compared to PCB. In comparison to PCB, which requires numerous modifications, such as adding via holes and a thermal bar in an attempt to lower the Rth value, neither packaging requires improvement. Ceramic was chosen for development based on Rth's highest performance, with the actual device consisting of a lead frame and PCB. The Zth measurement test was carried out on a ceramic package, and the Rth result was comparable to the simulation result of 7.6 K/W, indicating that simulation was already proved for research and development.

The purpose of this study is to determine which proposed packaging design would give the highest Rth performance of a 1 mm² chip as well as the best heat dissipation. In comparison to other studies, VCSEL packaging used the header and window cap as package components with a wavelength of 850 nm, and other VCSEL packaging developments used the sub mount on ceramic package with an output power ranging from 500 mW to 2 W, whereas this study used a huge wavelength and an output power of 4 W.

The purpose of this paper is to investigate the effects of magnetic field and viscous dissipation on mixed convection heat transfer, fluid flow and entropy generation in a porous media filled square enclosure heated with corner isothermal heater.

Finite volume method has been used to solve governing equations. A code is developed by FORTRAN and entropy generation is calculated from the obtained results of velocities and temperature. Results are presented via streamlines, isotherms, local and mean Nusselt number for different values of Richardson number (0.001=Ri=100), Hartmann number (0.001=Ha=100), Darcy number (0.001=Da=0.1), length of heaters (0.25=hx=hy=0.75) and viscous dissipation factors (10−4=ε=10−6).

It is observed that entropy is generated mostly due to lid-driven wall and right side of the heater. Entropy generation decreases with increasing of Hartmann number and heat transfer increases with decreasing of viscous parameter.

The originality of this work is to application of magnetic field and viscous dissipation on entropy generation in a lid-driven cavity with corner heater. Here, both corner heater and the external forces are original parameters.

Thermal management under high heat flux is crucial to developing high‐power light‐emitting diode (LED) applications. The purpose of this paper is to propose an efficient thermal dissipation technique for an LED back light unit (BLU) system.

A typical BLU system includes an LED package (GaN on sapphire, cathode/anode, silicone encapsulant, resin plus phosphor) on a printed circuit board (PCB), a light guide panel, and an aluminum cover frame. The temperature distribution of this system has been simulated and the thermal behavior within a 3D model has been investigated using a commercial computational fluid dynamic code (FLUENT 6.3).

The authors examined the heat‐spreading effect of cover lengths ranging from 6 to 300 mm and also observed the effect of back cover thickness on the junction temperature and cover frame temperature and investigated the influence of the air gap between the package and the cover frame. Removing the air gap lowers the maximum temperature by about 6 percent. It was found that the addition of a copper layer covering the external surfaces of the LED chip enhanced the cooling efficiency. Finally, the maximum junction temperature can be decreased by more than 21 percent in the range of parameters considered by removing the air gap, adding a heat spreader, and using a thick cover frame.

In this paper, thermal management for efficient heat spreading through a typical BLU system without using any additional devices is investigated. Several parameters that increase the system's temperature are examined, and a combination of design features that attenuate the junction temperature is proposed.

The purpose of this paper is to quantify the effects of thermal conductivity (TC), dielectric constant and dissipation factor (DF) of circuit laminates on the temperature rise with active components and RF trace heating.

Temperature rise measurements were made on surface mounted chip resistors (to simulate active components) at various dissipated power levels, with and without “via farms”. The RF heating temperature rise of 50 ohm microstrip transmission lines on 0.5 mm laminates was also measured by the same method.

The chip resistor temperature rise correlated with the independently measured TC of the laminate materials. The use of a “via farm” substantially reduced the temperature rise in all materials, but the higher TC laminates still conferred a measurable advantage. The trace temperature rise due to RF heating correlated with both TC and DF.

It was shown that the one‐dimensional heat transfer model does not accurately calculate the temperature rise due to significant in‐plane heat spreading, particularly with lower TC materials.

This paper details how temperature rise of both active components and 50 ohm transmission lines is affected by the thermal and electrical properties of the circuit laminate.