Thermal Management Of Electronic Packages Research Articles

Fused Deposition Modeling of Isotactic Polypropylene/Graphene Nanoplatelets Composites: Achieving Enhanced Thermal Conductivity through Filler Orientation.

High-performance thermally conductive composites are increasingly vital due to the accelerated advancements in communication and electronics, driving the demand for efficient thermal management in electronic packaging, light-emitting diodes (LEDs), and energy storage applications. Controlling the orderly arrangement of fillers within a polymer matrix is acknowledged as an essential strategy for developing thermal conductive composites. In this study, isotactic polypropylene/GNP (iPP/GNP) composite filament tailored for fused deposition modeling (FDM) was achieved by combining ball milling with melt extrusion processing. The rheological properties of the composites were thoroughly studied. The shear field and pressure field distributions during the FDM extrusion process were simulated and examined using Polyflow, focusing on the influence of the 3D printing processing flow field on the orientation of GNP within the iPP matrix. Exploiting the unique capabilities of FDM and through strategic printing path design, thermally conductive composites with GNPs oriented in the through-plane direction were 3D printed. At a GNP content of 5 wt%, the as-printed sample demonstrated a thermal conductivity of 0.64 W/m · K, which was 1.5 times the in-plane thermal conductivity for 0.42 W/m · K and triple pure iPP for 0.22 W/m · K. Effective medium theory (EMT) model fitting results indicated a significantly reduced interface thermal resistance in the through-plane direction compared to the in-plane direction. This work shed brilliant light on developing PP-based thermal conductive composites with arbitrarily-customized structures.

Experimental research of capillary structure technologies for heat pipes

This paper presents an experimental study on three different capillary structure technologies of heat pipes for application in the thermal management of electronic packaging. The first capillary structure is that of axial grooves manufactured by wire electrical discharge machining (wire-EDM). The sintering process with copper powder produced the second heat pipe. Finally, a hybrid heat pipe was made by the combination of the two previous methods. The heat pipes were produced using copper tubes with an outer diameter of 9.45 mm and a length of 200 mm, and were tested horizontally at increasing heat loads varying from 5 to 35 W. The working fluid used was distilled water. The experimental results showed that all capillary structures for heat pipes worked successfully, so the studied manufacturing methods are suitable. Nonetheless, the hybrid heat pipe is the best, due to the lowest thermal resistance presented.

Synthesis and analysis of anodic aluminum oxide-nanopore structure on Al substrates for efficient thermal management in electronic packaging

Increased heat generated in high-density electronic devices has intensified the search for advanced thermal management solutions. This urge has prompted various studies in thermal pad, liquid thermal interface material, gap fillers, and thermal coating, etc., with enhanced thermal performance. In this article, anodic aluminum oxide-nanopore (AAO-np) structure was grown on Al5052 alloy substrate electrochemically using two-step anodization process and it is used for efficient electronic packaging applications. It is observed that AAO-np substrate shows significant impact in thermal resistance (Rth) and junction temperature (Tj) of an electronic package. At 3.5 W input power with 14, 29, and 43 psi pressure condition the experimental results of AAO-np substrate resulted 15.11%, 14.58%, and 13.89% reduction in thermal resistance (ΔRth) and 15.53%, 14.85%, and 14.26% reduction in junction temperature (ΔTj) compared to bare Al5052 substrate. This enhanced thermal performance of AAO-np layer are due to high crystallinity, honeycomb-like morphology, nanopore oxide layer, and 0.35 µm rough surface which are effectively acting towards directional heat transport.

Estimation of contact heat transfer between curvilinear contacts using inverse method and group method of data handling (GMDH)-type neural networks

Precise knowledge of thermal contact conductance (TCC) across fixed solid contacts of flat-flat and curvilinear surfaces is becoming a crucial topic in advanced industrial applications such as thermal management of electronic packaging and nuclear energy production. In this study, at first, TCC across fixed solid contacts of flat-flat and cylinder-cylinder contacts has been calculated by inverse solution method. Furthermore, the accuracy of inverse method for estimation of TCC between flat-flat and cylinder-cylinder contacts has been evaluated based on the error analysis. Then, the GMDH (group method of data handling) algorithm has been used for heat transfer function estimation between contact surfaces based on input–output data which has been achieved from the experimental investigation and the inverse method using the Conjugate Gradient Method (CGM) with Adjoint problem. Different models of GMDH algorithm are applied and the optimal model is selected based on the common error criteria of RMSE (root mean square error). According to the results, the inverse method is accurate enough to predict TCC between flat-flat and cylinder-cylinder contacts with the root mean square error of 0.167 and 0.205, respectively. Also, it has shown that among the different models of GMDH algorithm, Genetic algorithm obtained by SVD method, make the best algorithm for TTC identification in fixed flat-flat and cylinder-cylinder contacting surfaces. Meanwhile, the attained Root Mean Square Error (RMSE) of the Genetic algorithm obtained by SVD method compared with the experimental results for flat-flat and cylinder-cylinder are 0.1459 and 0.1758, respectively.

Polysiloxane-graphite composites as thermal interface material for light emitting diode application: a study on impact of graphite nanopowder on thermal and surface properties

ABSTRACTThe thermal and surface properties of pure polysiloxane and graphite nanopowder (10% to 50%) reinforced polysiloxane composite films were studied. Polysiloxane/Graphite (50%-50%) Composite exhibit improved thermal conductivity (k – 0.35 W/mK) and decreased Junction temperature (ΔTj = 31.29 °C @ 700 mA) and thermal resistance (∆Rth-tot = 14.96 K/W @ 700 mA) compared to pure polysiloxane film. Overall, the prepared composites can be used as an alternate elastomer thermal pad or Thermal Interface Material for efficient thermal management in electronic packaging especially for LED applications.

Investigations on effect of evaporator length on heat transport of axially grooved ammonia heat pipe

Axially grooved ammonia heat pipes are widely used in spacecraft for thermal management of electronic packages, which are of various dimensions and heat dissipation levels. In order to study the effect of evaporator length on the maximum heat transport of heat pipes, two nominally charged dual channel axially grooved heat pipes (one for operating at a nominal temperature of 20 °C and the other for operating at a nominal temperature of 60 °C) were fabricated and tested using heaters of various lengths. In order to avoid flooding of the grooves/impact of puddle on the heat transport capability due to uncertainty in the charge quantity, all the tests were carried out at some adverse tilt. Experimental results reveal that at a given operating temperature, with decrease in the evaporator length, the evaporator heat flux increases and the maximum heat transport decreases. Analysis of the test results shows that decrease in the maximum heat transport with decrease in the evaporator length is mainly due to decrease in the available capillary pressure. Decrease in the capillary pressure with increase in the heat flux is postulated to be due to increase in the apparent contact angle between the working fluid and the wick surface.

Thermal performance evaluation of different passive devices for electronics cooling

The advent of modern electronic technology lead to miniaturization and high power density of electronic devices, then the existing electronic cooling techniques cannot be used, directly affecting the performance, cost, and reliability of electronic devices. Thus, the thermal management of electronic packaging has become a key technique in many products. Passive heat transfer devices can be a good alternative to the stabilization of electronic devices temperature. In this re-search, an experimental evaluation of the thermal performance of four different passive devices was accomplished. The considered devices were a rod, a thermosyphon, a heat pipe with a metal screen as the capillary structure, and a heat pipe with microgrooves. The heat pipe is a highly efficient device that carries large amounts of power with a small temperature difference. The heat pipe consists of the involucre, the working fluid, and the capillary structure. The thermosyphon is a kind of heat pipe assisted by gravity. In other words, it has no wick structure to return the working fluid. The devices were made of copper with a total length of 200 mm and an outer diameter of 9.45 mm. The thermosyphon and the heat pipes used deionized water as working fluid with a filling ratio of 60% of the evaporator volume. The devices were tested in vertical and horizontal positions under thermal loads between 5 W and 45 W. All the devices have operated satisfactorily when tested in accordance with the behavior of the thermal resistance. The heat pipes were the best among the tested devices and the best position was vertical.

Phase Change Material for Thermal Management in 3D Integrated Circuits Packaging

Effective thermal control and management in three-dimensional electronic packaging are desirable to ensure the heat generated in integrated circuits can be dissipated. Conventional base materials in electronics from substrate to protective layers, due to low coefficient of thermal conductivity, cannot help to cool down the circuits, while such elevated temperature could highly impact the performance of the chips. In this study, phase change material (PCM) is selected for potential applications in thermal management of electronic packaging due to its isothermal nature and high thermal storage capability. PCM based composite is developed through the impregnation technology using highly porous expanded graphite. Heat transfer test results reveal that the PCM based composite displays superior heat storage capacity, while maintaining the favorable feature of thermal and chemical stabilization for electronic applications. Toward the end, the concept of implementation of PCM based composite is proposed in thermal control of 3D integrated circuits. It is expected the proposed composite will improve heat dissipation, and ultimately enhance the performance of the chips.

Development of a Copper Heat Pipe with Axial Grooves Manufactured Using Wire Electrical Discharge Machining (Wire-EDM)

In this research, a heat pipe with grooves was experimentally analyzed for the application in thermal management of electronic packaging. The heat pipe was produced by a copper tube with an outer diameter of 9.45 mm, length of 205 mm, and capillary structure composed by axial grooves with average diameter of 220 μm. The grooves were manufactured using wire electrical discharge machining (wire-EDM). The working fluid used was de-ionized water. The condenser was cooled by air forced convection and the evaporator was heated using an electrical resistor. This heat pipe was tested horizontally to increasing heat loads varying from 5 to 15 W. The experimental results showed that the heat pipe worked successfully.

Thermal cycling reliability of Al/50Sip composite for thermal management in electronic packaging

Excellent thermal fatigue resistance with long-term reliability is one of the key requirements for thermal management materials. The effect of thermal cycling on mechanical properties and degradation mechanism of Al/50 wt% Sip composite are investigated. The composite is fabricated by hot pressing of pre-alloyed powder, and thermally cycled between room temperature and various temperatures (200, 250, and 300 °C) for up to 800 cycles. The results show that mechanical properties of the composite are quite stable under the maximum heating temperature of 200 °C regardless of the number of thermal cycle. However, they decrease gradually under 250 and 300 °C with a greater number of thermal cycle. Microscopic observations indicate that the property degradation is mainly resulted from the fragmentation of Si particles owing to the thermal stress because of the coefficient of thermal expansion mismatch.

Improved Thermal Conductivity in Carbon Nanotubes-Reinforced Syntactic Foam Achieved by a New Dispersing Technique

Syntactic foams are composite materials in which the matrix phase is reinforced with hollow micro-particles. Traditionally, syntactic foams are used for many high strength applications and as insulating materials. However, for applications demanding better heat dissipation, such as thermal management of electronic packaging, conductive fillers need to be added to syntactic foam. Carbon nanotubes (CNTs), although extremely conductive, have issues of agglomeration in the matrix. In this research, CNT-reinforced syntactic foam was developed based on our approach through which CNTs were dispersed throughout the matrix by growing them on the surface of glass microballoons. The thermal conductivity of nanotube-grown syntactic foam was tested with a Flashline® thermal analyzer. For comparison purposes, plain and nanotube-mixed syntactic foams were also fabricated and tested. Nanotube-grown microballoons improved the thermal conductivity of syntactic foam by 86% and 92% (at 50°C) compared to plain and nanotube-mixed syntactic foams, respectively. The improved thermal conductivity as well as the microstructural analysis proved the effectiveness of this approach for dispersing the carbon nanotubes in syntactic foams.

Microstructural and Thermal Characterization of Copper Based Composites for Thermal Management in Electronic Packaging

Copper based composites with 30, 40, 50 and 60 vol.% Al2O3 were fabricated by powder metallurgy and consolidated by pulsed electric current sintering (PECS). For the purpose of determining the advantage of using coated fillers, composite alumina particles with 18 vol.% copper were prepared by electroless copper plating. Coatings were continuous and homogeneous through alumina surface. Thus, composites consolidated by the modified process increased contact between the matrix and filler, which resulted in superior thermo-physical properties. Thermal conductivities of 210-99 and 227-114 W/mK were obtained for Cu/Al2O3 made by the admixture and the coated filler method, respectively. Such superiority is mainly attributed to the continuity in the matrix phase; the thermal conductivity values observed are similar to those shown by the traditional materials used in electronic packaging. The coefficient of thermal expansion was slight lower in composites fabricated by the coated filler method; values in the ranges of 14-11 and 13-10.5 μm/m°C were obtained for the admixture and the coated filler method, respectively.

機械学会における電子実装の信頼性と熱制御に関する研究分科会活動について

機械学会における電子実装の信頼性と熱制御に関する研究分科会活動について

CFD Analysis for Optimum Thermal Design of Carbon Nanotube Based Micro-Channel Heatsink

Carbon nanotube (CNT) is considered as an ideal material for thermal management in electronic packaging because of its extraordinary high thermal conductivity. Fabricated onto a silicon substrate to form micro-channels, the CNT based cooling fins show high heat dissipation efficiency. A series of 2D and 3D CFD simulations have been carried out for CNT based micro-channel cooling architectures based on one and two dimensional fin array in this paper using COMSOL 4.0a software. Micro-channels are generally regarded as an effective method for the heat transfer in electronic products. The influence of various fluids, micro-fin structures, fluid velocity and heating powers on cooling effects have been simulated and compared in this study. Steady-state thermal stress analyses for the forced convection heat transfer are also performed to determine maximum allowable stress and deflections for the different types of cooling assembly.

Interface thermal characteristics of flip chip packages – A numerical study

Flip chip ball grid array (FC-BGA) packages are commonly used for high inputs/outputs (I/O) ICs; they have been proven to provide good solutions for a variety of applications to maximize thermal and electrical performance. A fundamental limitation to such devices is the thermal resistance at the top of the package, which is characterized θ JC parameter. The die-to-lid interface thermal resistance is identified as a critical issue for the thermal management of electronic packages. This paper focuses on the effect of the interface material property changes on the interface thermal resistance. The effect of package’s junction to case (Theta-JC or θ JC) thermal performance is investigated for bare die, flat lid and cup lid packages using a validated thermal model. Thermal performance of a cup or flat lid attached and bare die packages were investigated for different interface materials. Improved Theta-JC performance was observed for the large die as compared to the smaller die. Several parametric studies were carried out to understand the effects of interface bond line thickness (BLT), different die sizes, the average void size during assembly and thermal conductivity of interface materials on package thermal resistance.

A numerical investigation and parametric study of cooling an array of multiple protruding heat sources by a laminar slot air jet

The present article reports on the fluid flow and heat transfer characteristics associated with cooling an in-line array of discrete protruding heated blocks in a channel by using a single laminar slot air jet. Numerical experiments have been carried out for different values of jet Reynolds number, channel height, slot width, spacing between blocks, block height, and block thermal conductivity. The effects of variation of these parameters are detailed to illustrate important fundamental and practical results that are relevant to the thermal management of electronic packages. In general, the effective cooling of blocks has been observed to increase with the increase of Reynolds number and the decrease of channel height. Heat transfer rates are enhanced for shorter and widely spaced heated blocks. Circulation cells that may appear on the top surface of the downstream blocks have been shown to decrease the value of Nusselt number for these blocks. The values of surface averaged Nusselt number attain their maximum at the block just underneath the impinging air jet, decrease for the downstream blocks, and approximately reach a constant value after the third block. Useful design correlations have been obtained for the mean Nusselt number for the heated blocks underneath and downstream the impinging jet.

Micron and Submicron-Scale Characterization of Interfaces in Thermal Interface Material Systems

One of the key challenges in the thermal management of electronic packages are interfaces, such as those between the chip and heat spreader and the interface between a heat spreader and heat sink or cold plate. Typically, thermal interfaces are filled with materials such as thermal adhesives and greases. Interface materials reduce the contact resistance between the mating heat generating and heat sinking units by filling voids and grooves created by the nonsmooth surface topography of the mating surfaces, thus improving surface contact and the conduction of heat across the interface. However, micron and submicron voids and delaminations still exist at the interface between the interface material and the surfaces of the heat spreader and semiconductor device. In addition, a thermal interface material (TIM) may form a filler-depleted and resin-rich region at the interfaces. These defects, though at a small length scale, can significantly deteriorate the heat dissipation ability of a system consisting of a TIM between a heat generating surface and a heat dissipating surface. The characterization of a freestanding sample of TIM does not provide a complete understanding of its heat transfer, mechanical, and interfacial behavior. However, system-level characterization of a TIM system, which includes its freestanding behavior and its interfacial behavior, provides a more accurate understanding. While, measurement of system-level thermal resistance provides an accurate representation of the system performance of a TIM, it does not provide information regarding the physical behavior of the TIM at the interfaces. This knowledge is valuable in engineering interface materials and in developing assembly process parameters for enhanced system-level thermal performance. Characterization of an interface material between a silicon device and a metal heat spreader can be accomplished via several techniques. In this research, high-magnification radiography with computed tomography, acoustic microscopy, and scanning electron microscopy were used to characterize various TIM systems. The results of these characterization studies are presented in this paper. System-level thermal performance results are compared to physical characterization results.

Advances in composite materials for thermal management in electronic packaging

A variety of new advanced composite materials are now available that provide great advantages over conventional materials for electronic packaging thermal control, including extremely high thermal conductivities (more than twice that of copper); low tailorable coefficients of thermal expansion; weight savings up to 80 percent; extremely high strength and stiffness; low-cost, net-shape fabrication processes; and cost reductions as high as 65 percent. In addition, composites are in a state of continual development that will provide even greater benefits. This article provides an overview of advanced composites used in thermal management, including properties, applications, and future trends. The focus is on materials having thermal conductivities at least as high as those of aluminum alloys. Future trends and the potential for composites in other aspects of the electronics industry, such as high-speed assembly machine materials of construction, are also examined.

THERMAL DISSIPATION CHARACTERISTICS OF A TAPE AUTOMATED BONDING ELECTRONIC PACKAGE

Thermal measurements play a very important role in the successful design and thermal management of electronic packages. Accurate measurements of temperature distribution under different conditions are necessary to characterize the thermal resistance of electronic packages from the chip junction to the cooling sink. This paper deals with the effects of power dissipation, air velocity and ambient temperature on the thermal performance of a tape automated bonding (TAB) package. In this study, the characteristics of junction temperature (TJ), junction to ambient thermal resistance (θJ-A), junction to case thermal resistance (θJ-C), and case to ambient thermal resistance (θC-A) are investigated in detail. The package was placed in a custom-designed low speed wind tunnel which allows the air velocity to be varied between 0.5 m/s and 5 m/s. Package surface temperatures were measured using infrared thermography, while chip junction temperatures were indirectly obtained using the Electrical Test Method (ETM) in accordance to Military Standard 883. The experimental results show that for the TAB package, air velocity significantly affects θC-A and θJ-A but has negligible effect on θJ-C· In contrast, θJ-C was found to be dependent on power dissipation. In addition, the ambient temperature was found to have a strong effect on the thermal performance of the TAB package. For the tested TAB package, it was noted that the inner lead temperatures are higher than that of the chip epoxy surface.

Improved hollow cathode magnetron deposition for producing high thermal conductivity graphite-copper composite

High thermal conductivity heat sinks for thermal management in electronic packaging is enabling to a variety of advanced electronic applications. State-of-the-art heat sinks have thermal conductivities, K, generally less than 180 W mK −1, and frequently have large expansion mismatch with chips such as silicon and gallium arsenide. A unique technology for producing graphite fiberreinforced copper (C f/Cu) composite has been developed that produces thermal conductivities up to 454 W mK −1 utilizing a K= 640 W mK −1 fiber reinforcement (with a potential for 800 W mK −1 when utilizing a K=1100 W mK −1 P130 fiber) and thermal expansion that can be matched to chip materials. The process consists of utilizing a hollow cathode sputtering process to deposit a bonding layer followed by copper on spread graphite fibers, which are then consolidated into composites with architectures to achieve desired thermal conductivity and thermal expansion. The copper thickness determines graphite fiber loading up to 80%. In heat sink applications, where the electrical conductivity of the graphite fiber-reinforced copper composite is a problem, processing has been developed for applying electrically insulating diamond film, which has high thermal conductivity (ca. 1100 W mK −1) and acts as a heat spreader.