Packaging Of Electronic Devices Research Articles

A novel steady-state method for measuring thermal conductivity of thermal interface materials with miniaturized thermal test chips

Thermal interface materials (TIMs) are widely used in electronic device packaging, and accurate characterization of their thermal properties is essential. However, existing TIM test platforms suffer from large size and inconsistency between copper-based test platforms and packaged silicon materials. To address these issues, this study proposes a method based on a miniaturized testing platform constructed using silicon-based thermal test chips (TTC). The thermal conductivity of several specimens was measured using steady-state heat source thermal transmission. The total thermal resistance, thermal contact resistance and thermal conductivity of several TIMs were evaluated through theoretical analysis and experimental verification. The thermal conductivity of several TIMs was tested using the proposed Back-to-Face and Back-to-Back TTC modules. The results demonstrate that this method exhibits high accuracy and can be used to characterize a wide range of TIMs.

Device packaging and integration optimization based on neural network method: Effect of microchannel structure on heat sink performance

With the continuous improvement of power density of electronic device packaging, microchannel structure based on advanced packaging integration technology has become one of the hot topics in thermal management research. In this paper, two heat sink models are numerically simulated: rectangular microchannel and microchannel-pinfin hybrid. The effects of microchannel structure, inlet/outlet arrangement and pinfin design on heat sink performance were studied. The heat sink performance is evaluated by the maximum temperature at hotspot area, the total thermal resistance and the mean absolute temperature deviation (MATD). The research results show that at the same Reynolds number, the hybrid structure with pinfin has better heat sink performance. Compared with the rectangular microchannel structure, the maximum temperature at the hotspot area is reduced by 20.45 K and the total thermal resistance is reduced by 5.9 %. Compared with the three inlet/outlet arrangements of I-type, U-type and Z-type, the I-type hybrid structure has the best heat sink performance. The average absolute temperature deviation is about 10 K at high Reynolds number, and the temperature distribution is more uniform. In addition, the heat sink performance is improved by increasing the pinfin size to expand the heat transfer area. This paper uses simulation results to build an artificial neural network model in order to quickly and accurately predict numerical results under different parameter conditions. The network model has good accuracy and robustness, with a mean absolute error of 0.376 %. The prediction model takes heat source power, Reynolds number and pinfin structural parameters as input. Rapidly predicting the performance of heat sinks with different structural parameters under different boundary conditions will effectively save experimental and computational costs. This research provides new ideas and tools for optimizing heat sink design, and helps improve the application of microchannel cooling technology in electronic devices.

Innovative Approaches to Enhance and Measure Medication Adherence in Chronic Disease Management: A Review.

Medication non-adherence is a problem that affects up to 50% of patients with chronic diseases. The result is a failure to achieve therapeutic goals and an increased burden on the healthcare system. It is, therefore, highly appropriate to develop models to assess patient adherence to prescribed therapy. To date, there are many methods for doing this. However, several tools have been developed that subjectively or objectively, directly or indirectly, assess the level of patient adherence. Electronic medication packaging devices are among the most rapidly evolving methods of measuring adherence. Other emerging technologies include the use of artificial intelligence algorithms and ingestible biosensors. The former is being used to create applications for mobile phones and laptops. The latter appears to be the least susceptible to the risk of overestimating adherence but remains very expensive. Here, we present recent developments in measuring patient adherence, and provide details of achievements in objective methods for assessing adherence, such as electronic monitoring devices, video-observed therapy, and ingestible biosensors. A dedicated section on using artificial intelligence and machine learning in adherence measurement and reviewing questionnaires and scales used in specific diseases is also included. Methods are discussed along with their advantages and potential limitations. This article aimed to review current measures and future initiatives to improve patient medication adherence.

Thermal Fatigue Failure of Micro-Solder Joints in Electronic Packaging Devices: A Review

In electronic packaging products in the service process, the solder joints experience thermal fatigue due to temperature cycles, which have a significant influence on the performance of electronic products and the reliability of solder joints. In this paper, the thermal fatigue failure mechanism of solder joints in microelectronic packages, the microstructure changes of the thermal fatigue process, the influence factors on the joint fatigue life, and the simulation analysis and forecasting of thermal fatigue life are reviewed. The results show that the solder joints are heterogeneously coarsened, and this leads to fatigue cracks occurring under the elevated high-temperature phase of alternating temperature cycles. However, the thickness of the solder and the hold time in the high-temperature phase do not significantly influence the thermal fatigue. The coarsened region and the IMC layer thicken with the number of cycles, and the cracks initiate and propagate along the interface between the intermetallic compound (IMC) layer and coarsened region, eventually leading to solder joint failure. For lead-containing and lead-free solders, the lead-containing solder shows a faster fatigue crack growth rate and propagates by transgranular mode. Temperature and frequency affect the thermal fatigue life of solder joints to different degrees, and the fatigue lifetime of solder joints can be predicted through a variety of methods and simulated crack trajectories, but also through the use of a unified constitutive model and finite element analysis for prediction.

Construction of 3D BN network with high-density thermal conductive paths

Efficient heat dissipation is essential to further improve the integration of high-power electronic packaging devices. Three-dimensional BN networks with high-density thermal conductive paths were designed as the heat transfer skeleton of thermal interface materials. 3D networks with high-density thermal conductive paths inlaid between oriented BN paths were constructed using precursor self-assembly and freeze-drying to improve the thermal conductivity of polymeric materials. The results show that high-density thermally conductive paths have stronger polymer-enhanced thermal conductivity than directional thermal paths and compared with pure TPU, the thermal conductivity of TPU/BN-2 under low BN filling content (10%wt) is increased by 250 % and 286.5 % in the through surface and flat surface respectively. This work provides new ideas for the preparation of polymer composites for thermal interface materials in electronic packaging and integrated circuits with excellent thermal management properties.

Engineering lightweight Poly(lactic acid) graphene nanoribbon nanocomposites for sustainable and stretchable electronics: Achieving exceptional electrical conductivity and electromagnetic interference shielding with enhanced thermal conductivity

The challenge of creating flexible and sustainable electronics with properties such as lightweight, electrical and thermal conductivity, and electromagnetic interference (EMI) shielding is addressed in this study. Carbon nanotubes and graphene are commonly used in flexible electronic devices, but gaps exist in their conductivity and flexibility. A novel and scalable fabrication method is introduced, involving the creation of bio-based nanocomposites by integrating flexible and high aspect-ratio graphene nanoribbons (GNRs) into a poly (lactic acid) (PLA) matrix. The nanocomposites were drawn above the glass transition temperature (Tg) of PLA, resulting in the formation of extended shish structures, as observed in scanning electron microscope (SEM) images. These structures significantly enhanced thermal and electrical conductivities, as well as EMI shielding features. The combination of flexible GNR nanofillers with uniaxial stretching led to a substantial increase in Young's modulus, tensile strength, and toughness by approximately 550 %, 440 %, and 600 %, respectively, most likely due to the increased network connection despite the higher flexibility of GNRs. Moreover, in-plane thermal conductivity registered a notable enhancement of approximately 110 %. The EMI shielding reached 26 dB, with an absorption contribution to EMI shielding of around 45 %. Additional improvement was achieved through foaming of the stretched samples, resulting in multilayer structures with alternative extended shish and foam structures. Furthermore, a significant augmentation of approximately 33 dB in total EMI shielding of the foamed samples, accompanied by an 85 % increase in SEA was documented. These promising findings underscore potential applications across diverse domains, including thermal interface materials, electronic packaging, capacitors, and energy storage devices, with a specific emphasis on the realm of sustainable and stretchable electronics.

Electronic Interaction of Epoxy Resin with Copper at the Adhered Interface.

A better understanding of the aggregation states of adhesive molecules in the interfacial region with an adherend is crucial for controlling the adhesion strength and is of great inherent academic interest. The adhesion mechanism has been described through four theories: adsorption, mechanical, diffusion, and electronic. While interfacial characterization techniques have been developed to validate the aforementioned theories, that related to the electronic theory has not yet been thoroughly studied. We here directly detected the electronic interaction between a commonly used thermosetting adhesive, cured epoxy of diglycidyl ether of bisphenol A (DGEBA) and 4,4'-diaminodiphenylmethane (DDM), and copper (Cu). This study used a combination of density functional theory (DFT) calculations and femtosecond transient absorption spectroscopic (TAS) measurements as this epoxy adhesive-Cu pairing is extensively used in electronic device packaging. The DFT calculations predicted that π electrons in a DDM molecule adsorbed onto the Cu surface flowed out onto the Cu surface, resulting in a positive charge on the DDM. TAS measurements for the Cu/epoxy multilayer film, a model sample containing many metal/adhesive interfaces, revealed that the electronic states of excited DDM moieties at the Cu interface were different from those in the bulk region. These results were in good accordance with the prediction by DFT calculations. Thus, it can be concluded that TAS is applicable to characterize the electronic interaction of adhesives with metal adherends in a nondestructive manner.

Design and fabrication of bilayer polylactic acid @ secondary alkyl sulfonate/cellulose fabrics with asymmetric wettability for the electronic device packaging

Design and fabrication of bilayer polylactic acid @ secondary alkyl sulfonate/cellulose fabrics with asymmetric wettability for the electronic device packaging

A Study of Electroplated Nanoporous Copper Using Aberration-Corrected Transmission Electron Microscopy.

Nanoporous Cu foam is widely applied in many fields such as the packaging of electronic power devices. In this study, a sandwich-structured Cu-Zn eutectic alloy precursor composed of Cu0.53Zn0.47/Cu5Zn8/Cu0.53Zn0.47 is prepared through electroplating. The surface layer of the precursor, Cu0.53Zn0.47, has a flat surface with numerous grain boundaries, which effectively promotes its dealloying behavior. By contrast, Cu5Zn8 has a porous structure, which promotes the dealloying behavior at the center of the precursor. The dealloying of Cu0.53Zn0.47 is dominated by the coherent surface diffusion of Cu atoms, and the crystal lattice and orientation show no changes before and after dealloying. By contrast, the dealloying behavior of Cu5Zn8 requires the renucleation of Cu crystals; in this process, Cu atoms are transported to the surface of the layer by capillary forces to form clusters, which nucleate and grow.

The preparation of permanent antistatic additive based on poly(ether-b-amide) copolymers and its modification effect on polyamide 6

Abstract Conventional polymers have typically been used in the packaging of various electronic devices; however, due to the inherent electrically insulating properties these materials fail to dissipate static charges. To address this issue, novel poly(ether-b-amide) (PEBA) segmented copolymers consisting of uniform rigid oxalamide and flexible polyethylene glycol (PEG) were synthesized via melt polycondensation. The influence of PEG molecular weight and the spacer length separating two oxalamide units on the condensed structure, mechanical performance, and antistatic properties was systematically investigated. Fourier-transform infrared (FTIR) demonstrated strongly hydrogen bonded and highly ordered oxalamide hard segments with the degree of ordering between 71 and 85 % even at low levels. Mechanical behavior results showed that segmented copolymers have an obvious yield point, an elastic modulus between 20 and 30 MPa, and strain at break exceeding 2000 %. Meanwhile, such copolymers possessed low surface resistivity, as low as 107 Ω, which is significantly less than that of commercial antistatic additives. The antistatic effect of PEBA on polyamide 6 (PA6) was also investigated, revealing that when the content reached 30 wt%, the surface resistivity of the alloys decreased from 1013 Ω to 1011 Ω and remained stable after 40 days, even after water washing treatment. Overall, these findings illustrate that the newly synthesized PEBA copolymers demonstrate outstanding long-term antistatic properties and provide valuable insights for the development of polyether-based multiblock copolymer antistatic agents.

Room temperature wafer bonding through conversion of polysilazane into SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document}

Room temperature wafer bonding is a desirable approach for the packaging and assembly of diverse electronic devices. The formation of SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document} layer at the bonding interface is crucial for a reliable wafer bonding as represented by conventional bonding techniques such as hydrophilic bonding and glass frit bonding. This paper reports a novel concept of room temperature wafer bonding based on the conversion of polysilazane to SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document} at the bonding interface. As polysilazane is converted to SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document} by hydrolysis, in this work, adsorbed water is introduced to the bonding interface by plasma treatment, thereby facilitating the formation of SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document} at the wafer bonding interface. The experimental results indicate that the adsorbed water from the plasma treatment diffuses into the polysilazane layer and facilitates its hydrolysis and conversion. The proposed method demonstrates the successful wafer bonding at room temperature with high bond strength without interfacial voids. This technique will provide a new approach of bonding wafers at room temperature for electronics packaging.

Cu TSV Filling with Cetyltrimethyl Ammonium Cations (CTA+) and Br-

Through silicon via (TSV) technology is essential for the three-dimensional packaging of electronic devices. After creating high-aspect-ratio vias, Cu electrodeposition is performed to achieve defect-free Cu interconnection. The most important purpose of electrodeposition process is to fill the features without any defects, and this process is called superfilling, superconformal deposition, or bottom-up filling. Since TSV is a key component for the packaging of semiconductor devices, various research on the electrodeposition process for TSV filling have been studied. Defect-free TSV filling can be achieved by introducing appropriate organic/inorganic additives into the electrolyte and the filling performance can be promoted by pulse reverse electrodeposition.1-3 Generally, it has been reported that Cu bottom-up filling at TSVs can be obtained by three-additive combinations (suppressor, accelerator, and leveler) or by using a single suppressor. Tetronic 701 is the most representative suppressor in a single-additive filling method, which was based on S-shaped negative differential resistance (S-NDR) behavior.4-6 In the case of three-additive systems, various levelers that contained ammonium functional groups, a polymeric suppressor, and an accelerator have been researched.7,8 Furthermore, it has been reported that halide ions (Br- and I-) can act as levelers for inducing Cu bottom-up filling at TSVs.9,10 This study investigated the effects of cetyltrimethyl ammonium cation (CTA+) and halide ion on TSV filling in the presence of an accelerator and polymeric suppressor. The influences of two halide ions, Cl- and Br-, on the adsorption of CTA+ and their convection dependency were studied. This presentation will introduce the electrochemical behaviors of halide ions and CTA+ and defect-free filling using the optimum combination of these additives. References M. Hayase, and K. Otsubo. "Copper deep via filling with selective accelerator deactivation by a reverse pulse" J. Electrochem. Soc.,157, D628 (2010).Q.S. Zhu, X. Zhang, C.Z. Liu, and H.Y. Liu. "Effect of reverse pulse on additives adsorption and copper filling for through silicon via" J. Electrochem. Soc.,166, D3006 (2019)Q.S. Zhu, A. Toda, Y. Zhang, T. Itoh, and R. Maeda. "Void-free copper filling of through silicon via by periodic pulse reverse electrodeposition" J. Electrochem. Soc.,161, D263 (2014)T. P. Moffat, and D. Josell. "Extreme bottom-up superfilling of through-silicon-vias by damascene processing: suppressor disruption, positive feedback and turing patterns" J. Electrochem. Soc.,159, D208 (2012)D. Joell, and T. P. Moffat. "Superconformal copper deposition in through silicon vias by suppression-breakdown." J. Electrochem. Soc.,165, D23 (2018)M. Dong, Y. Zhang, T. Hang, and M. Li. "Structural effect of inhibitors on adsorption and desorption behaviors during copper electroplating for through-silicon vias." Electrochim Acta372 (2021)M. J. Kim, Y. Seo, J. H. Oh, Y. Lee, H. C. Kim, Y. G. Kim, and J. J. Kim. "Communication—halide ions in teg-based levelers affecting TSV filling performance." J. Electrochem. Soc.,163, D185 (2016)V. Q. Dinh, K. Kondo, V. H. Hoang, and T. Hirato. "Communication—Bottom-up TSV filling using sulfonated diallyl dimethyl ammonium bromide copolymer as a leveler." J. Electrochem. Soc.,166, D505 (2019)M. J. Kim, H. C. Kim, and J. J. Kim. "The influences of iodide ion on Cu electrodeposition and TSV filling." J. Electrochem. Soc.,163, D434 (2016)M. Sung, Y. Yoon, J. Hong, M. J. Kim, and J. J. Kim. "Bromide ion as a leveler for high-speed TSV filling." J. Electrochem. Soc., 166, D546 (2019) Figure 1

Enhanced thermal conductivity and electrical insulation by patterned self-assembly of electrospun nanofibers

Low intrinsic thermal conductivity (TC) of polymer materials has severely limited their further applicability in electronic and electrical products. To enhance the TC, a strategy for constructing nanofiller-based thermal conductive networks by patterned self-assembly of electrospun nanofibers was first proposed in this paper. By selecting a regular metal mesh as the collector, the electrostatic field-induced directional deposition of nanofibers was achieved, thereby constructing interconnected heat transfer paths aligned in at least four directions. The in-plane TC of heat-pressed electrospun polyvinylidene fluoride (PVDF) nanofibers with 20 wt% loading of boron nitride nanosheets (BNNSs) can reach 7.27 W/(m·K). Electrical insulation of the PVDF/BNNS composites has also been confirmed, showing high volume resistivity and breakdown strength, which have increased by 460.0 % and 26.6 %, respectively, compared to pure PVDF. Finally, a double-layer composite film with waterproof and easy-cleaning characteristics was prepared for electronic device packaging. This simple and efficient preparation strategy for thermal conductive networks may bring new perspectives to thermal management applications.

Thermal Characterization of Metal-Diamond Composite Heat Spreaders Using Low-Frequency-Domain Thermoreflectance.

High thermal conductivity and an appropriate coefficient of thermal expansion are the key features of a perfect heat spreader for electronic device packaging, especially for applications with increased power density and the increasing demand for higher reliability and semiconductor device performance. For the past decade, metal-diamond composites have been thoroughly studied as a heat spreader, thanks to their high thermal conductivities and tailored coefficients of thermal expansion. While existing thermal characterization methods are good for quality control purposes, a more accurate method is needed to determine detailed thermal properties of these composite materials, especially if clad with metal. Low-frequency-range-domain thermoreflectance has been adopted to measure the thermal conductivity of a metal-diamond composite sandwiched between metal cladding layers. Due to this technique's low modulation frequencies, from 10 Hz to 10 kHz, multiple layers can be probed and measured at depths ranging from tens of micrometers to a few millimeters.

Electrodeposition of Multi-Segment Nanowires and Site-Selective Solder Deposition for Magnetic Assembly and Nanoscale Joining

Electronic device packaging involves complex wiring assemblies for transport of electrical and thermal energy, enabling increasingly sophisticated circuit designs in an industry favoring aggressive device miniaturization. Nanoscale miniaturization of the wire morphology has become increasingly sophisticated in recent years with regards to synthesis; however, the ability to arrange and manufacture these small-scale materials to fully exploit their novel properties has been quickly outpaced. The purpose of this investigation is the establishment of a synthesis technique for a core/shell nanowire structure with tunable compositional templating via electrodeposition which can pass through this bottleneck via directed matrix assembly. A gold-nickel-gold nanowire structure was utilized as the core, synthesized via electrochemical deposition into an anodic aluminum oxide (AAO) template; the nickel segment was chosen to act as a magnetic vehicle for directed assembly, while the bordering gold tips were coated with a solder shell. Gold-selective deposition of this tin solder shell was achieved by establishing a chemisorbed nickel-protective monolayer via immersion in azelaic acid solution. Next, the protected nanowires were dispersed in an aqueous reaction vessel with excess sodium borohydride reducing agent. Controlled addition of tin sulfate and sodium dodecyl sulfate solution to the vessel resulted in the formation of tin seeds which deposited along the gold tips of the nanowires, growing into a “dumbbell” shape nanowire with tin deposited on both gold tips. Composition and confirmation of the solder deposition was performed with scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopic (EDS) analysis. Crystal structure of the core/shell nanowires was performed with x-ray diffraction (XRD) to identify intermetallic formation between the tin and gold. The core/shell nanowires were arranged magnetically across a conductive interdigitated electrode and melted by an infrared-driven reflow procedure under flux atmosphere, establishing ohmic contact tip-to-tip between nanowires and in wire-to-pad morphologies. This work establishes an effective and scalable method for site-specific nanowire functionalization while simultaneously addressing miniaturization-associated assembly issues in its desired applications.

Rapid formation, grain refinement and shear property of high-temperature-stable full IMC joints

Solid liquid interdiffusion (SLID) bonding that can fabricate high-melting point full IMC joints is playing an increasing key role in 3rd-generation semiconductor power electronic device packaging for high temperature applications. In this study, rapid formation of Cu/intermetallic compounds (IMCs)/Cu–8Ni joints with fine (Cu,Ni)6Sn5 and (Cu,Ni)3Sn grains was achieved by SLID bonding Cu/Sn/Cu–8Ni structure. The formation and evolution of the IMCs and the elemental distribution and shear property of the full IMC joints during bonding and subsequent aging were systematically investigated. Due to the Ni doping, the growth of the (Cu,Ni)6Sn5 IMC was significantly accelerated during bonding while that of the Cu3Sn phase was strongly suppressed during both bonding and aging. The total IMC growth rate in the Cu/Sn/Cu–8Ni solder joints was approximately 44 times faster than that in the Cu/Sn/Cu solder joints under the same bonding condition. After aging at 260 °C for up to 400 h, the full IMC joints showed good thermostability composing of fine IMC grains and no Kirkendall voids were observed. The shear strength of the full IMC joints slightly dropped from 63.17 MPa after bonding to 54.35 MPa after aging. The proposed SLID bonding using Cu/Sn/Cu–8Ni structure was proved to be a promising method for forming high-temperature-stable full IMC joints for 3rd-generation semiconductor power device packaging or 3D packaging applications.

Coating dense silicon carbide layer on artificial graphites to achieve synergistically enhanced thermal conductivity and electronic insulation of polymer composites

AbstractAs a potential thermal conductive filler, spherical graphite (SG) has high thermal conductivity, low density, and a good spherical shape structure. However, the poor electrical insulation of SG will seriously limit its application in highly integrated electronic device packaging. Herein, through a simple liquid–solid chemical reaction, the surface of the SG particle is firmly covered by a uniform silicon carbide (SiC) ceramic coating. Subsequently, a polycarbosilane precursor is immersed into the pore channels of the SiC layer and pyrolyzed at a high temperature to densify the coating. As compared to the original SG thermal pad, the SiC‐coated SG‐derived pad exhibits significantly enhanced electrical insulation and even higher thermal conductivity. As a result, the SiC‐coated SG‐based composite displays a high thermal conductivity of 3.36 W m−1 K−1, a satisfactory resistivity of 7.10 × 1010 Ω cm accompanied with a low density of 1.65 g/cm3. This work could provide the instructional designing protocol of the highly thermal conductive carbon‐based particles by coating ceramic layers for potential application in electronic packaging.

Transparent, Stretchable, and Self‐Healable Gas Barrier Films with 2D Nanoplatelets for Flexible Electronic Device Packaging Applications

AbstractSelf‐healable elastomeric materials (PUAxPU10–x‐PDMS, x = 4, 6, or 8) have been synthesized and utilized as substrates or encapsulation films on the top of barrier films (deposited on polyethylene terephthalate (PET) substrates) to improve their gas barrier properties for packaging applications. Hexa‐layer (HL) assembly consisting of two inorganic 2D nanoplatelets, including Mg‐Al layered double hydroxide (LDH) and hexagonal boron nitride (hBN), and two oppositely charged polyelectrolytes, that is, polyethyleneimine (PEI) and poly(sodium styrene‐4‐sulfonate) (PSS), have been developed by alternative depositions of HL (i.e., PSS/LDH/PSS/PEI/hBN/PEI) sequentially. Then, a layer‐by‐layer technique is applied to produce multiple assemblies of hexa‐layer (HL)n and reduce water vapor transmission rate (WVTR) values of elastomeric PUA8PU2‐PDMS and PET substrates. The optimum WVTR values of 7.1 × 10−3 and 8.0 × 10−3 g m−2 day−1 are achieved using barrier PET/(HL)8/PUA8PU2‐PDMS (125/3/1 µm) and PUA8PU2‐PDMS/(HL)8 (125/3 µm) films, respectively. The self‐healable barrier PUA8PU2‐PDMS and PUA8PU2‐PDMS/(HL)8 films recover their initial WVTR values after self‐healing of mechanically damaged films. Organic light‐emitting diodes (OLEDs) encapsulated with PET/(HL)8/PUA8PU2‐PDMS and PUA8PU2‐PDMS/(HL)8 have 9–10 times longer half‐lifetime values than bare OLEDs. Accordingly, this report develops transparent, stretchable, and self‐healable gas barrier films for next‐generation flexible electronic device packaging applications.

Flexible, stretchable and lightweight polyurethane and graphene nanoplatelets nanocomposite for high performance EMI shielding application

The incessant growth of technology has extensively increased the usage of electronics and telecommunication devices, leading to critical electromagnetic (EM) pollution and affecting the performance of intensely sensitive electronic devices. Herein, graphene nanoplatelets (GNP) were synthesized from the microwave intercalation method, followed by water-bath sonication. The different dosing of synthesized GNP (2, 4, 6, and 8 weight%) is further encapsulated in polyurethane (PU) matrix via solution casting technique to obtain enhanced electromagnetic interference (EMI) shielding performance. It was found that the 6 weight % of GNP (GNP6) having a density of 0.74 g/cc shows excellent stretching mechanical properties (> 400%), mechanical strength (1.4 times PU), electrical conductivity (2.75 S/m) and microwave properties. The maximum EMI shielding efficiency (SE) of 40.9 dB and 70.5 dB is noticed for GNP6 at 1 mm and 2 mm thickness, respectively. The SE is also measured for GNP6 2 mm thick sample after mechanically bending for 500 cycles and observed average variation <3 dB. The EMI SE is measured after placing the GNP6 inside the waveguide at different bending radii varying from 3 to 9 mm, and 75 dB of SE is observed for a bending radius of 3 mm. The fabricated GNP6 nanocomposite can show stable EMI shielding performance even after immersion in pure water, followed by sonication treatment for 2 hours and confirming the capability of the nanocomposite to handle the complex environment. The EMI shielding mechanism for GNP/PU is extensively explained concerning the microstructure and microwave properties. The computational analysis is done by simulating the GNP6 in the CST microwave studio tool over the broad frequency range (1-18 GHz). Thus, the highly stretchable, flexible, and lightweight GNP6 is a favourable nanocomposite providing a high EMI shielding value for next-generation electronic packaging of flexible electronic devices and coating of conformal devices used in aerospace industries.

Phytic acid as a biomass flame retardant for polyrotaxane based phase change materials

Petrochemical resources are facing depletion and human long-term survival needs sustainable development. In this era, it is very important to develop new sustainable phase change materials (PCMs), because it has shown great application value in the effective utilization of industrial waste heat, solar energy harvesting, and electronic heat treatment. In this work, we reported a biomass phytic acid (PA) modified polyrotaxane (PLR) as PCMs for thermal management. The tensile performances, fire safety, phase transition performances of the PCMs were investigated. It is found that all the tensile properties, char residual, and fire-safety of PLR can be enhanced remarkably by introduce of PA. Typically, the Young's modulus, yielding strength and tensile strength of the PLR were 826.7 MPa, 14.2 MPa and 14.2 MPa, respectively, and significantly increased to 1527.4 MPa, 22.1 MPa, and 24.0 MPa respectively, with the addition of 10 wt% of PA. Elongation (>783 %) for all modified PCMs was gradually increased with the increase of PA contents. Thermal analysis shows that the fire safety of PLR is significantly improved. Specifically, for the best sample PLR-PA30, the pHRR could decrease by 54.2 %, THR decreased by 34.0 %; and the LOI increased from 20.8 % to 28.2 %. The PCMs showed the perfect form stability and leakage-proof performance, enhanced thermal conductivity and outstanding cycle properties. Notably, its biomass source, and high flexibility, enhanced fire safety and completely green pathway may provide a practical way for the highly flexible and sustainable packaging of electronic devices for heat treatment.