Search results

The dramatic expansion in the use and capability of electronic devices in recent years has been facilitated by the substantial development of production techniques. Modern electronic circuits as used in the computer, defence, aerospace, vehicle and domestic appliance industries contain a great many joints and these have to be made reliably and economically without degrading sensitive circuit components. This article describes the major microjoining developments currently of interest to the microelectronics industry, with emphasis on the work conducted by the microjoining section of The Welding Institute, much of which has been directly sponsored by the UK Ministry of Defence (DCVD).

The purpose of this paper is to describe how a traditional metal base plate is replaced with a vapour chamber, a two‐phase flow heat transfer module with high heat transfer efficiency, to effectively reduce the temperature of heat sources as graphic processing unit (GPU) of smaller area and higher power.

As a first step, the nature of flow field of a vapour chamber‐based thermal module with heat sink is simulated and analysed through computational numerical method. Second, a sample is prepared according to the theoretical results and the performance of thermal modules is tested together with thermal performance experiment.

The results show that when the fin height from vapour chamber top to fan bottom area is more than 3 mm and not more than 8 mm, the vapour chamber‐based thermal module can achieve the optimum heat dissipation and the maximum heat flux may exceed 90 W/cm². Also, when copper fins are 3 mm in height, 0.2 mm in thickness, 53 in number and spaced out 1.0 mm apart, the optimum total thermal resistance of a vapour chamber‐based thermal module is 0.28 ^○C/W.

The Sapphire Atomic HD3870 of Video Graphics Array module for AMD RV670XT using MicroLoops vapour chamber has greater thermal performance than the AMD reference dual slot thermal module. So, AMD latest GPU is considered to be the vapour chamber thermal cooler to solve the higher power consumption.

Latest Computational Fluid Dynamics (CFDs) tools allow modeling more finely the conjugate thermo-fluidic behavior of a single electronic component mounted on a Printed Wiring Board (PWB). A realistic three-dimensional representation of a large set of electric copper traces of its composite structure is henceforth achievable. The purpose of this study is to confront the predictions of the fully detailed numerical model of an electronic board to a set of experiment results to assess their relevance.

The present study focuses on the case of a Ball Grid Array (BGA) package of 208 solder balls that connect the component electronic chip to the Printed Wiring Board. Its complete geometrical definition has to be coupled with a realistic board layers layout and a fine description of their numerous copper traces to appropriately predict the way the heat is spread throughout that multi-layer composite structure. The numerical model computations were conducted on four CFD software then compare to experiment results. The component thermal metrics for single-chip packages are based on the standard promoted by the Joint Electron Device Engineering Council (JEDEC), named JESD-51. The agreement of the numerical predictions and measurements has been done for free and forced convection.

The present work shows that the numerical model error is lower than 2 per cent for various convective boundary conditions. Moreover, the establishment of realistic numerical models of electronic components permits to properly apprehend multi-physics design issues, such as joule heating effect in copper traces. Moreover, the practical modeling assumptions, such as effective thermal conductivity calculation, used since decades, for characterizing the thermal performances of an electronic component were tested and appeared to be tricky. A new approach based on an effective thermal conductivity matrix is investigated to reduce computation time. The obtained numerical results highlight a good agreement with experimental data.

The study highlights that the board three-dimensional modeling is mandatory to properly match the set of experiment results. The conventional approach based on a single homogenous layer using effective thermal conductivity calculation has to be banned.

The thermal design of complex electronic components is henceforth under increasing control. For instance, the impact of gold wire-bonds can now be investigated. The three-dimensional geometry of sophisticated packages, such as in BGA family, can be imported with all its internal details as well as those of its associated test board to build a realistic numerical model. The establishment of behavioral models such as DELPHI Compact Thermal Models can be performed on a consistent three-dimensional representation with the aim to minimize computation time.

The study highlights that multi-layer copper trace plane discretization could be used to strongly reduce computation time while conserving a high accuracy level.

High performance aluminium nitride water cooled heat sinks were fabricated and characterized. A variety of fabrication processes were employed to meet different cooling requirements. They include laser cut microchannel coolers for chip and multichip heat sinks as well as dry pressed pin fin heat sinks for power electronics. Thermal simulation was used to optimize the heat sink design.

The purpose of this paper is to present the development of printed wiring board (PWB)‐based microfluidic building blocks and their integration into systems for DNA amplification and electronic detection.

Technologies from embedded passives (EP) and photolithographic high‐density interconnect are integrated into a traditional PWB platform to enable multifunctional electrochemical sensors for on‐chip detection of biological assays.

PWB materials and processes can be applied to develop microelectromechanical systems (MEMS) and microfluidic systems. On‐chip heaters using EP have been demonstrated with excellent accuracy. The on‐chip heaters can be used for localized temperature control as well as heat air pumps. The integration of EP and microchannels is a promising approach to add functionalities to the PWB‐based microsystems.

Further integration of microchannels with the embedded heaters and electrochemical sensors will increase the compactness, functionality, and value of the PWB‐based microfluidic systems.

The paper describes the development and integration of PWB‐based building‐blocks such as EP and microchannels for MEMS and microfluidic applications. These elements will enable new applications and enhanced functionalities of PWB.

We first provide an overview of some predominant theoretical methods currently used for predicting thermal conductivity of thin dielectric films: the equation of radiative transfer, the temperature‐dependent thermal conductivity theories based on the Callaway model, and the molecular dynamics simulation. This overview also highlights temporal and spatial scale issues by looking at a unified theory that bridges physical issues presented in the Fourier and Cattaneo models. This newly developed unified theory is the so‐called C‐ and F‐processes constitutive model. This model introduces the notion of a new dimensionless heat conduction model number, which is the ratio of the thermal conductivity of the fast heat carrier F‐processes to the total thermal conductivity comprised of both the fast heat carriers F‐processes and the slow heat carriers C‐processes. Illustrative numerical examples for prediction of thermal conductivity in thin films are primarily presented.

This paper presents the thermal analyses carried out to predict the temperature distribution of the silicon chip with non‐uniform power dissipation patterns and to determine the optimal locations of power generating sources in silicon chip design layout that leads to the desired junction temperature, T_j. Key thermal parameters investigated are the heat source placement distance, level of heat dissipation, and magnitude of convection heat transfer coefficient. Finite element method (FEM) is used to investigate the effect of the key parameters. From the FEM results, a multiple linear regression model employing the least‐square method is developed that relates all three parameters into a single correlation which would predict the maximum junction temperature, T_j,max.

The purpose of this paper is to develop a dynamic compact thermal model (DCTM) of electronic packages. This model is a necessary tool for rapid thermal analysis of the systems which we exposed to boundary condition variation and/or power switching mode such as mobile systems and battery powered systems.

The methodology of compact model generation used was based on generating the transient dynamic detailed finite element thermal model of a package, designing a resistor/capacitor network topology representative of the dynamic detailed model, calculating the resistors'/capacitors' value by optimization method and validation efforts. The method is demonstrated for a ball grid array (BGA) package, a commonly used modern electronic package.

Based on the obtained results, it can be concluded that the dynamic thermal behavior of a BGA package can be accurately described by a generated dynamic compact model in terms of predicted junction temperature response and heat flux of the desired locations of the package.

This model is capable of calculating the temperatures and heat fluxes at desired locations which can help the designer to perform the thermal analysis much faster and easier with the required accuracy.

Water cooling of hybrid modules allows a power dissipation much higher than that of conventional methods. This paper describes the design and construction of a copper‐clad Invar water‐cooled hybrid power circuit intended for use in a medical hand‐held tool which is a 25 mm diameter cylinder. The thermal study demonstrates the interest of a copper‐clad Invar heat exchanger: water flowing at a rate lower than 15 Ih−1 allows the dissipation of more than 50 W in the module while keeping the external temperature of the tool below 35°C.

Power modules including the insulated gate bipolar transistor (IGBT) are widely used in the applications of motor drivers. The thermal behavior of these modules makes it important to choose the optimum design of cooling system. The purpose of this paper is to propose an RC thermal model of the dynamic electro‐thermal behavior of IGBT pulse width modulation inverter modules.

The electrothermal model has been implemented and simulated with a MATLAB simulator and takes into account the thermal influence between the different module chips based on the technique of superposition.

This study has led to a correction of the junction temperature values estimated from the transient thermal impedance of each component operating alone.

In this paper, an experimental technique of a thermal influence evaluation is presented.