In this work, we report the customized design and development of a fully automated measurement system to characterize the temperature-dependent properties of microscale thermoelectric devices. The featured system can characterize the devices up to a dimension of 8.79 × 8.79 mm 2 in an atmospheric environment. Commercially available bismuth telluride-based thermoelectric modules (both thermoelectric generator and thermoelectric cooler) are used to validate the feasibility and accuracy of the developed system. Their performance data is analysed and compared with the available manufacturer datasheet. The measured data from these devices are found to be in good agreement with the anticipated values and showed an acceptable deviation of less than 4% in the output performances. The developed setup is simple to operate and suitable for performance evaluation of both macro and micro-thermoelectric devices. The system accurately reproduces application conditions the module may be subjected to in a real-world environment.

Data associated with the following publication: "A fully automated measurement system for the characterization of micro thermoelectric devices near room temperature" (DOI: 10.1016/j.applthermaleng.2023.120111).

In order to dissipate large amount of heat, two-phase (2-Φ) mechanical pumping loops (MPLs) are often required. Compared to their passive counterparts, such as heat pipes, 2- ΦMPLs are also suitable for distributed payloads and can improve the uniformity of surface temperature. One of the main issues, however, with both single-phase and 2- Φ MPLs is the reliability of the pump as its failure directly results in a failure of the whole cooling system, leading to overheating of the electronic components. Moreover, the micropump is required to withstand the high working pressures (above 6 MPa) necessary in 2- Φ MPL working with refrigerant such as CO 2 or ammonia. The size and weight of the pump is often an issue in electronic cooling of small space satellites, drones or servers that affects the widespread implementation of MPL technologies. To overcome issues with reliability, high working pressures and compact form factors, a novel micropump based on a patented counter-wound solenoid coil technology and a fast response flow meter were developed by the authors. In this paper, the integration of the micropump and flow meter in a flow control unit for 2- Φ MPL system using Novec 7100 as working fluid will be presented. Two different tests were carried out to evaluate the heat dissipation capability of the unit in different working conditions: Test 1 studied the effect of input pump power on heat dissipation, while Test 2 investigated the effects of different condenser coolant temperatures. It was shown that when the input pump power was 0.5 W, up to 325 W (15.3 W/cm 3 ) of heat power could be dissipated by the loop.

Microfluidic technology witnessed a fast growth in recent years thanks to its diverse nature that allows its use in a wide range of industries including microelectronics, aerospace, telecommunications, biomed-ical and pharmaceutical. One of the limiting issues for the implementation of microfluidics in high end electronics or biomedical devices is that pumps are not able to develop the required flow rates and pressures. A novel magnetic shuttle pump (MSP) technology that can achieve class-leading pressure and flow rate and a numerical model are presented in this paper. The MSP technology consists of an oscillating neodymium ring shuttle magnet housed in a solenoid driver. Two counter-wound copper coils are used to oscillate the shuttle magnet. The numerical model couples the electromagnetic and fluidic properties of the MSP by taking into account the forces acting on the shuttle magnet. The model is used to predict the pump characteris-tics of two MSPs with different size: the MSP1.7 with overall volume 1.7 cm(3) and MSP3.3 with overall volume 3.3 cm(3). Simulations and experimental characterisation were carried out considering an electric driving power of 1W. Experimentally, a maximum pressure P-max = 43.53 kPa and a maximum flow rate Q = 46.69 ml/min were achieved by the MSP1.7, while a maximum pressure P-max= 21.74 kPa and a max-imum flow rate Q = 205.99 ml/min were achieved by the MSP3.3. Due to the close agreement between the experimental and simulated data, the model can be used in the future to modify the design of the MSP to achieve the required Pressure/Flow characteristics. (C) 2021 The Author(s). Published by Elsevier B.V.

The establishment of near-eutectic Sn–Ag–Cu (SAC) alloys as replacements for eutectic Sn–Pb marked as the beginning for the development of lead-free solder alloy in electronic packaging industry. Second-generation lead-free alloys with lower Ag content were introduced to address the shortcomings such as poor mechanical shock performance and higher cost. Yet, the evolution has not stopped. In response to higher reliability requirements, third generation lead-free alloys are being developed to serve the applications operated in increasingly aggressive environments. In this chapter, case studies on thermal fatigue performance of various SAC-based lead-free solders and Sn–Zn-based low temperature solders have been made. The effect of solder size, solder composition, Sn grain morphology, printed circuit board surface finish, and thermal cycling profile on solder joint microstructure and reliability is evaluated. The relationship between microstructural evolution and thermal fatigue failure mechanism is discussed.

Development of cost-effective and increasingly efficient sustainable materials for energy-storage devices, such Li-ion batteries, is of crucial future importance. Herein, the preparation of carbon nanofibres from biopolymer blends of lignin (byproduct from the paper and pulp industry) and polylactic acid (PLA) or a thermoplastic elastomeric polyurethane (TPU) is described. SEM analysis shows the evolving microstructural morphology after each processing step (electrospinning, stabilisation and carbonisation). Importantly, it is possible to tailor the nanofibre porosity by utilising miscibility/immiscibility rules between lignin and the polymer additive (PLA/TPU). PLA blends (immiscible) generate porous structures whereas miscible lignin/TPU blends are solid when carbonised. Electrodes produced from 50% PLA blends have capacity values of 611 mAhg(-1) after 500 charge/discharge cycles, the highest reported to date for sustainable electrodes for Li-ion batteries. Thus, this work will promote the development of lignocellulose waste materials as high-performance energy-storage materials.

Contemporary Photonic Integrated Circuit (PIC) packages within the communications network infrastructure have reached a thermal limit. Integrated packages involving microfluidic channels are an appealing development to improve the thermal design of future PIC packages, to significantly improve the removal of heat fluxes in order to sustain the expected enhanced data traffic growth. The Thermally Integrated Smart Photonics Systems (TIPS) project aims to develop and demonstrate a thermally enabled integrated platform that is scalable, to meet the predicted data traffic demands. Full system integration requires an integrated pumping solution, therefore a primary heat exchanger that can deliver the required thermal performance with a low pressure drop (Delta P) is needed. A channel containing a single array of cylindrical posts offers a low pressure drop, similar to a large hydraulic diameter minichannel. Local destabilization of the flow would provide heat transfer enhancement. In particular, non-Newtonian fluids have been shown to exhibit significant mixing in such configurations. Micro Particle-Image Velocimetry (mu PIV) measurements were taken for Newtonian and viscoelastic fluids within this channel. Instabilities associated with the viscoelastic fluid were recorded immediately upstream of the post array. This flow exhibited almost a four-fold increase in mixing at comparable flow rates to the Newtonian fluid tested. This suggests that the Nusselt number enhancement associated with such flows could increase the heat transfer rates quite significantly in microchannels containing obstructions.

In severe operation environments where extreme thermal cycles and long dwells are common, such as the engine compartment of motor vehicles, solder alloys resistant to fatigue under thermomechanical stimuli are required. With this in mind, new third generation lead free alloys are being designed to enhance the toughness of interfacial intermetallic layer (IML), and solid solution strengthening is introduced to compensate for the strength loss due to Ag3Sn particle coarsening. In this paper, the reliability of ceramic Ball Grid Array (BGA) assemblies using third generation lead-free alloys under various strain levels and Accelerated Temperature Cycling (ATC) profiles, 0/100 degrees C and -40/125 degrees C, are presented. Failure analysis was conducted and cracking along the IML at the solder/package interface was determined to be the root failure mechanism. The ATC test results indicate that the induced fatigue strain on each ring of the BGAs is a function of maximum dwell temperature, alloy choice and temperature change (Delta T) within the thermal cycle, and this is noted to have a significant influence on characteristic lifetimes. Results correlate well with the Coffin-Manson model, and activation energies (E-A) were determined to predict the reliability of the electronic on the premise of the same predominant failure mechanism. (C) 2018 Elsevier Ltd. All rights reserved.

Packaging electronic devices is a growing challenge as device performance and power levels escalate. As device feature sizes decrease, ensuring reliable operation becomes a challenge. Ensuring effective heat transfer from an integrated circuit and its heat spreader to a heat sink is a vital step in meeting this challenge. The projected power density and junction-to-ambient thermal resistance for high-performance chips at the 14 nm generation are >100 Wcm(-2) and <0.2 degrees CW-1, respectively. The main bottleneck in reducing the net thermal resistance are the thermal resistances of the thermal interface material (TIM). This review evaluates the current state of the art of TIMs. Here, the theory of thermal surface interaction will be addressed and the practicalities of the measurement techniques and the reliability of TIMs will be discussed. Furthermore, the next generation of TIMs will be discussed in terms of potential thermal solutions in the realisation of Internet of Things.

Rare earth oxides (REOs) are attracting attention for use as cost-effective, high-performance dropwise condensers because of their favorable thermal properties and robust nature. However, to engineer a suitable surface for industrial applications, the mechanism governing wetting must be first fully elucidated. Recent studies exploring the water-wetting state of REOs have suggested that these oxides are intrinsically hydrophobic owing to the unique electronic structure of the lanthanide series. These claims have been countered with evidence that they are inherently hydrophilic and that adsorption of contaminants from the environment is responsible for the apparent hydrophobic nature of these surfaces. Here, using X-ray photoelectron spectroscopy and dynamic water contact angle measurements, we provide further evidence to show that REOs are intrinsically hydrophilic, with ceria demonstrating advancing water contact angles of ≈6° in a clean surface state and similar surface energies to two transition metal oxides (≳72 mJ/m2). Using two model volatile species, it is shown that an adsorption mechanism is responsible for the apparent hydrophobic property observed in REOs as well as in transition metal oxides and silica. This is correlated with the screening of the polar surface energy contribution of the underlying oxide with apparent surface energies reduced to <40 mJ/m2 for the case of nonane adsorption. Moreover, we show that the degree of surface hydroxylation plays an important role in the observed contact angle hysteresis with the receding contact angle of ceria increasing from ∼10° to 45° following thermal annealing in an inert atmosphere. Our findings suggest that high atomic number metal oxides capable of strongly adsorbing volatile species may represent a viable paradigm toward realizing robust surface coating for industrial condensers if certain challenges can be overcome.

The Thermally Integrated Smart Photonics Systems (TIPS) H2020 project aims to develop a solution to meet the significant demands of data traffic growth, by designing a scalable, thermally-enabled, 3D integrated optoelectronic platform. Micro-thermoelectric coolers (TECs) and microfluidics will be integrated with optoelectronic devices to precisely control device temperature, and thus device wavelength. To understand the thermal-hydraulic behaviour of micro-scale heat exchangers, a range of exchanger geometries will be characterised hydraulically (via manometry and velocimetry) and thermally (via infra-red imaging). This paper will discuss the optical and thermal characterisation of existing active laser devices using infra-red imaging in order to obtain a baseline thermal resistance for the development of the heat exchangers. Thermographs of existing active devices were recorded to determine the thermal characteristics of the laser structure and the spatial temperature variation across the laser surface. The increase in temperature of an active laser as a function of dissipated power was found to be linear at 45°C/W. Repeatability and laser-to-laser variation tests showed good agreement. The spatial temperature variations in the x- and y- directions were ±8°C and ±3°C of the mean temperature, respectively. An understanding of the thermal characteristics of existing laser devices will allow for appropriate testing of the viability of microfluidic heat exchangers as coolers for micro-TECs.

Molecular self-assembling block copolymers (BCPs) have shown promise as a next generation bottom-up lithography technology. However, a critical step in advancing this approach is the elimination of polymer dewetting due to bulk solvent nucleation and thermodynamically driven film rupture that can occur during the solvent vapor annealing process. We report on the pattern formation via phase segregation of spin coated diblock copolymer films through the investigation of annealing parameters in the limit of high solvent vapor saturation conditions that results in wafer-scale patterning without observing polymer dewetting defects. Specifically, the work addresses polymer dewetting in diblock copolymer nanodot templates through the use of a "neutral" functionalization layer and the development of a custom-built solvent vapor annealing chamber to precisely control saturation conditions. Furthermore, the long anneal times (4 h) using a standard static solvent vapor annealing procedure were reduced to ∼15-30 minutes with our dynamic solvent vapor annealing system for the high χ, cylindrical forming poly(styrene)-block-poly(4-vinyl-pyridine) [PS-b-P4VP] diblock copolymer system. We discuss the kinetic mechanism governing the phase segregation process that highlights the small processing window bounded by long phase segregation timescales (≳1 min) on one side and the initiation of polymer film dewetting on the other. These results demonstrate a key step towards realizing a high fidelity, low cost BCP patterning technique for large-scale "bottom-up" feature definition at nanometer length scales.

ABSTRACT Packaging electronic devices is a growing challenge as device performance and power levels escalate. As device feature sizes decrease, ensuring reliable operation becomes a challenge. Ensuring effective heat transfer from an integrated circuit and its heat spreader to a heat sink is a vital step in meeting this challenge. The projected power density and junction-to-ambient thermal resistance for high-performance chips at the 14 nm generation are >100 Wcm−2 and <0.2 °CW−1, respectively. The main bottleneck in reducing the net thermal resistance are the thermal resistances of the thermal interface material (TIM). This review evaluates the current state of the art of TIMs. Here, the theory of thermal surface interaction will be addressed and the practicalities of the measurement techniques and the reliability of TIMs will be discussed. Furthermore, the next generation of TIMs will be discussed in terms of potential thermal solutions in the realisation of Internet of Things.

We demonstrate the fIrst steps towards realizing a highly effective hardmask fabrication technique for producing cheap low defect nanoporous membranes, which can be incorporated as fluidic wicking structures for use in evaporative cooling solutions integrated at device level. Next-generation cooling solutions are becoming necessary to dissipate increasing heat fluxes and maintain acceptable junction temperatures in high-speed electronics. The proposed pumpless two-phase evaporation-based heat sink device relies on a supported nanoporous membrane (SNM) as the driving mechanism for generating the requisite capillarity for pumping low surface tension refrigerants. Molecular self-assembling block copolymers (BCPs), specifIcally cylindrical forming poly(styrene)-block-poly(4vinyl-pyridine) (PS-b-P4VP) are ideal as a cost effective hardmask fabrication route for patterning sub 80 nm pores when compared to the high cost of ownership of state of the art immersion photolithography.We report on the pattern formation of the phase segregated BCP with optimization of the annealing parameters. The work addresses defect elimination in the BCP template by developing a custom solvothermal annealing chamber which achieves excellent phase segregation of the BCP, limits processing defects and prevents polymer dewetting on a microscale level. The chamber is capable of processing up to 4 inch wafers and allows for in-situ monitoring of a solvent annealing cycle by monitoring fIlm swelling via optical reflectometry.

New third generation lead free alloys are being targeted for use in harsh environments requiring resistance to both thermal and mechanical loading. In applications such as the engine compartment of motor vehicles where extreme thermal cycles and long dwell are common, it has been necessary to look for strengthening mechanisms that better survive extremes of temperature and strain. Alloys are being designed to improve toughness of interfacial intermetallic layers and provide solid solution strengthening to compensate for the loss of strength once the Ag3Sn particles coarsen. Results show that while solid solution-strengthening by additions of Sb is effective, it is not sufficient, and other strengthening options through the introduction of additional precipitates and solid solution strengthening using Bi is most desirable. The role of Ni is difficult to discern but it is most concentrated in the Cu6Sn5 intermetallic phase located at the interface between the solder and the copper substrate. This presumably has a toughening effect on the intermetallic thereby inhibiting crack formation and growth.

The flow of shear-thinning viscoelastic fluids is investigated experimentally in a serpentine microchannel at very large Weissenberg numbers (Wi > 104) undergoing elastic instability. The effects of geometric curvature on local flow instability and the consequent heat transfer enhancement are reported. Unlike previous studies where fluids with large zero-shear viscosities (up to 300 mPa.s) were used, we employ a working fluid with a lower viscosity (η0 = 9 mPa.s) more suited to microfluidic heat transfer applications while exhibiting viscoelastic characteristics. This results in Elasticity number (EI = Wi/Re) flows an order of magnitude larger than previously reported in the literature with apparent viscosities close to the solvent viscosity under flow conditions. Detailed Micro Particle Image Velocimetry (μPIV) measurements reveal the local enhancements due to instantaneous flow structures which result in vigorous local mixing at sub-critical Reynolds numbers. In addition the pressure drop increase is moderate as mixing occurs locally and the flow is maintained undisturbed elsewhere throughout the flow path.

Thermal properties of nanocomposites have been an area of intensive research for the past decade due to its potential application in electrical interconnection, heat transfer and electronics cooling. Considerable progress has been made in fabricating nanocomposite materials using different filler materials and polymer. Nanocomposites made from nanowires and nanotubes are the subject of recent interest due to the elongated one dimensional shape of the filler materials which shows unique properties e.g. lower percolation threshold, anisotropy, and other one dimensional properties. Most of the reported works used different forms of carbon allotropes (single wall, multiwall, fiber, etc.) or oxide and metallic nanowires as filler materials and mixing with polymer. Early work on carbon nanotube (CNT) based fillers focused on mechanical mixing of nanotubes with polymer and thereby achieving higher thermal conductivity as compared to polymer. Vertically aligned carbon nanotube and fiber is also investigated as thermal interface material [1]. However, the possibility of inadvertently incorporating contaminating impurities, the existence of voids between CNTs, and the growth conditions of CNT arrays greatly affect the effective thermal conductivity of CNTs, typically resulting in a thermal interface material (TIM) with a large performance uncertainty [2, 3]. Thermal properties of graphene-metal-polymer composite was thoroughly investigated in recent years [4]. Similarly, metallic nanowires both dispersed and vertically aligned were also proposed as filler materials in the metal-polymer nanocomposites [5, 6]. Recently, we have demonstrated that the elongated metallic nanowires and nanowire based composites can act as thermal conduit between two surfaces and thereby able to transfer heat more efficiently as compared to carbon nanotube based composite materials [5]. However, it has been observed that heat transport through these one dimensional filler materials is a complex subject of intensive research, which includes different thermal transport mechanism depending on constituent material (whether it is an electrical conductor, semiconductor or insulator) as well its size, shape and the crystallinity [7]. This heat transfer mechanism was explained with a modified effective medium formulation based on Nan’s model [8]. Furthermore, it has been observed that modulus of the nanocomposite plays a vital role in the transferring heat when pressed between two surfaces and lower modulus composite conforms easily to the roughnesses of the mating surface [5]. In this work we investigate the thermal properties of metal (Cu and Sn) nanowire-polymer composites. The thermal diffusivity of the composites was measured using a Xenon flash thermal constant analyzer. A thermal impedance system is employed according to the modified ASTM D5470 standard to measure the thermal impedance of the composites. A thermal impedance of 9±1 °Cmm 2 W -1 is achieved at a pressure of 100 kPa, which is 50% lower thermal impedance compared to the commercial TIM. Acknowledgements This work is financially supported by Enterprise Ireland under commercialization fund technology development program.Grant No. CFTD/2008/322. References 1. B. A. Cola, X. Xu and T. S. Fisher, Applied Physics Letters , 90 (2007). 2. D. Srivastava, K. Cho and C. Wei, Applied Mechanics Reviews , 56 , 215 (2003). 3. P. K. Schelling, L. Shi and K. E. Goodson, Materials Today , 8 , 30 (2005). 4. V. Goyal and A. A. Balandin, Applied Physics Letters , 100 (2012). 5. J. Xu, A. Munari, E. Dalton, A. Mathewson and K. M. Razeeb, Journal of Applied Physics , 106 (2009). 6. A. Munari, J. Xu, E. Dalton, A. Mathewson and K. M. Razeeb, in Electronic Components and Technology Conference, 2009. ECTC 2009. 59th , p. 448 (2009). 7. K. M. Razeeb and S. Roy, Journal of Applied Physics , 103 (2008). 8. C.-W. Nan, R. Birringer, D. R. Clarke and H. Gleiter, Journal of Applied Physics , 81 , 6692 (1997).

Polyethylenes with various morphologies were analysed, as a function of strain and radiation doses, using a novel lamella alignment ratio (LAR) technique on data obtained from small-angle X-ray scattering (SAXS) measurements at the Diamond Light Source synchrotron. The authors have used this technique previously to describe the influence of irradiation dose on crystal morphologies of orthopaedic grade polyethylenes. The aim of the current work is to highlight and explain the effectiveness of the LAR technique as an analysis tool for macromolecular crystal reorganization, crystallographic structural changes and crystal deformation during simultaneous strain measurements. Using new data for polyethylenes with varying morphology and irradiation dosage, the effectiveness of the technique is detailed. These findings are particularly useful for polymeric materials used in property critical applications and present a facile method for SAXS analysis. It is proposed that this method could potentially be used as a convenient route for the analysis of conditioning and crosslinking mechanisms on crystallographic relationships in more complex monomeric structures.

Cover: Backscattered scanning electron microscopy cross sectional image of a Ni/NiPd/Au electronic connector after 10 days exposure to a Class III mixed flowing gas (MFG) corrosive atmosphere. This work was carried out at the Stokes Research Institute Laboratories, University of Limerick, Ireland with collaborators in Det Norske Veritas (U.S.A.), Inc and Southwest Research Institute, San Antonio, TX, USA.Further details on the performance of various connector coatings can be found in: M. N. Collins, M. Reid, E. Dalton, K. Shannon, L. F. Garfias‐Mesias, Mixed flowing gas (MFG) corrosion of various connector coatings, Materials and Corrosion 2013, 64, 7.