Assembly Of Arrays Research Articles

Comparison of the Reliability of SAC305 and Innolot-Based Solder Alloy in a Board-Level BGA Package Considering Harmonic and Random Vibration Environment

This paper presents a comparative study of the fatigue life of solder joints in a board-level Ball Grid Array (BGA) assembly. It specifically contrasts the commonly used SAC305 alloy with the advanced Innolot-based solder alloy, recognized for its superior tensile strength. Through Finite Element Analysis (FEA), we simulate and predict the reliability of these solder joints under harmonic and random vibration conditions. Following the JEDEC (Joint Electronic Device Engineering Council) standards, two different board-level BGA assemblies are used for the analysis. In both assemblies, the dimensions of the substrate, molding compound, and solder balls remain identical; only the board dimensions are changed to observe how they affect stress in the solder joints. The results indicate that using Innolot raises the volume-averaged stress levels by more than 25% on larger boards and about 5% on smaller boards compared to SAC305. This increase in stress levels is due to the Innolot alloy having a less significant stiffening effect than SAC305, which results in higher stress levels under the same excitation conditions. While the stress in the Innolot-based solder joint is greater than that in the SAC305 joint under identical excitation conditions, the fatigue life of the Innolot joint is significantly higher than that of the SAC305 joint. The results show that the Innolot-based alloy exceeds the performance of SAC305, and that it is suitable for use as a solder alloy in extreme vibration conditions.

Tipping the balance between twist and chair ligand conformers in multinuclear ethylzinc cyclophosphazenates.

Hexaanionic cyclophosphazenate ligands [(RN)6P3N3]6- provide versatile platforms for the assembly of multinuclear metal arrays due to their multiple coordination sites and highly flexible ligand core structure. This work investigates the impact of incrementally increasing the steric demand of the ligand periphery on the coordination behavior of ethylzinc arrays. It shows that the increased congestion around the ligand sites is alleviated by progressive condensation with the elimination of diethylzinc. The condensation is accompanied by a switch in ligand conformation: the phosphazene ring of the methyl derivative adopts the chair conformer in the dimeric complex (EtZn)12[(RN)6P3N3]2, while the more sterically demanding isobutyl derivative exhibits twist conformers in both the monomeric complex (EtZn)6[(iBuN)6P3N3] and the condensed dimer (EtZn)8Zn2[(iBuN)6P3N3]2. Ethyl and propyl derivatives mark a tipping point: the dimeric complex (EtZn)12[(RN)6P3N3]2 exhibits the chair conformation and is observed in solution and within the stabilising environment of a co-crystal. However, when crystallising in pure form, it transforms with the loss of one equivalent of Et2Zn into the collapsed dimer (EtZn)10Zn[(RN)6P3N3]2 which features the twist conformer.

ASSEMBLY COUPLING TECHNOLOGY OF MICROLENS ARRAY AND OPTICAL FIBER BUNDLE

Continuous improvements in high-resolution infrared remote sensing imaging technology have led to important applications in various fields; however, the low filling rate of optical fiber and degradation of the focal ratio of the image end remain problems that restrict further development. The coupling technology of the microlens array and optical fiber bundle assembly is the key to solving these problems. In this work, we studied the coupling technology of microlens array and optical fiber bundle assembly. Specifically, six degrees-of-freedom coupling assembly and infrared radiation energy measurement subsystems were built, and based on this a high-precision mechanical alignment coupling efficiency measurement system was designed. After kinematic analysis, it was found that the maximum positioning error was within the allowable error range, making the system suitable for the requirements of precision assembly. Finally, the alignment coupling efficiency of the system was tested, and the results showed that the coupling efficiency reached 92.65%, which was only 6.01% lower than the assumed theoretical value and affirmed the feasibility of the system design for improving the performance of optical fiber image transmission systems.

Guided ad infinitum assembly of mixed-metal oxide arrays from a liquid metal.

Bottom-up nano- to micro-fabrication is crucial in modern electronics and optics. Conventional multi-scale array fabrication techniques, however, are facing challenges in reconciling the contradiction between the pursuit of better device performance and lowering the fabrication cost and/or energy consumption. Here, we introduce a facile mixed-metal array fabrication method based on guided self-assembly of polymerizing organometallic adducts derived from the passivating oxides of a ternary liquid metal to create mixed metal wires. Driven by capillary action and evaporation-driven Marangoni convection, large-area, high-quality organometallic nano- to micro-wire arrays were fabricated. Calcination converts the organometallics into oxides (semiconductors) without compromising wire continuity or array periodicity. Exploiting capillary bridges on a preceding layer, hierarchical arrays were made. Similarly, exploiting the conformity of the liquid to the mold, arrays with complex geometries were made. Given the periodicity and high refractive index of these arrays, we observe guided mode resonance while their complex band structures enable fabrication of diodes or gates. This work demonstrates a simple, affordable approach to opto-electronics based on self-assembling arrays.

Are stellar embryos in Perseus radio-synchrotron emitters? Statistical data analysis with Herschel and LOFAR paving the way for the SKA

Cosmic rays (CRs) are crucial to the chemistry and physics of star-forming regions. By controlling the ionization rate of molecular gas, they mediate the interaction between matter flows and interstellar magnetic fields, thereby regulating the entire star formation process, from the diffuse interstellar medium to the formation of stellar embryos, or cores. The electronic GeV component of CRs is expected to generate nonthermal synchrotron radiation, which should be detectable at radio frequencies across multiple physical scales. However, synchrotron emission from star-forming regions in the Milky Way has barely been observed to date. In this work, we present the first attempt to statistically detect synchrotron emission with the LOw Frequency ARray (LOFAR) at 144 MHz from the nearby Perseus molecular cloud (at a distance of ∼300 pc). We perform median stacking over 353 prestellar and 132 protostellar cores derived from the Herschel Gould Belt Survey. Using data from the LOFAR two meter sky survey (LoTSS) with an angular resolution of 20arcsec, we identify 18 potential protostellar candidates and 5 prestellar ones. However, we interpret these as extragalactic contamination in the Herschel catalog. Our statistical analysis of the remaining cores does not reveal any significant radio counterpart of prestellar and protostellar cores at levels of $5, μJy beam^-1 and 8, μ$Jy beam^-1 in the stacked maps, respectively. We discuss our non-detections in two ways. For protostellar cores, we believe that strong extinction mechanisms of radio emission, such as free-free absorption and the Razin-Tsytovich effect, may be at play. For prestellar cores, using analytical models of magnetostatic-isothermal cores, the lack of detection with LOFAR helps us constrain the maximum ordered magnetic-field strength statistically attainable by these objects, on the order of 100 μG. We predict that the statistical emission of the prestellar-core sample in Perseus seen by LoTSS should be detectable in only 9 hours and 4 hours with the Square Kilometre Array-Low (SKA-Low) array assemblies AA* and AA4, respectively.

Design, Testing, and Validation of a Soft Robotic Sensor Array Integrated with Flexible Electronics for Mapping Cardiac Arrhythmias.

Cardiac mapping is a crucial procedure for diagnosing and treating cardiac arrhythmias. Still, current clinical techniques face limitations including insufficient electrode coverage, poor conformability to complex heart chamber geometries, and high costs. This study explores the design, testing, and validation of a 64-electrode soft robotic catheter that addresses these challenges in cardiac mapping. A dual-layer flexible printed circuit board (PCB) was designed and integrated with sensors into a soft robotic sensor array (SRSA) assembly. Design considerations included flex PCB layout, routing, integration, conformity to heart chambers, sensor placement, and catheter durability. Rigorous SRSA in vitro testing evaluated the burst/leakage pressure, block force for electrode contact, mechanical integrity, and environmental resilience. For in vivo validation, a porcine model was used to demonstrate the successful deployment, conformability, and acquisition of electrograms in both the ventricles and atria. This catheter-deployable SRSA represents a meaningful step towards translating the integration of soft robotic actuators and stretchable electronics for clinical use, showcasing the unique mechanical and electrical performance that these designs enable. The high-density electrode array enabled rapid 2 s data acquisition with detailed spatial and temporal resolution, as illustrated by the clear and consistent cardiac signals recorded across all electrodes. The future of this work will lie in enabling high-density, anatomically conformable devices for detailed cardiac mapping to guide ablation therapy and other interventions.

Photo-Induced Three-Component Reaction for the Construction Of α-Tertiary Amino Acid Derivatives.

The synthesis of α-tertiary amino acids (ATAAs), which are pivotal components in natural metabolism and pharmaceutical innovation, continues to attract significant research interest. Despite substantial advancements, the pursuit of a facile, versatile, and resource-efficient methodology remains an area of active development. In this work, we introduce a visible light-triggered three-component reaction involving readily available nitrosoarenes, N-acyl pyrazoles, and allyl or (bromomethyl)benzenes under mild conditions. This approach enables the straightforward assembly of a wide array of ATAA derivatives (42 examples) in commendably high yields (up to 89 %). Mechanistic investigations elucidate that the reaction proceeds through a dehydration condensation between nitrosoarenes and N-acyl pyrazoles to generate ketimine intermediates. This is followed by a light-driven halogen atom transfer (XAT) process and a radical addition, culminating in the formation of the desired products. The approach showcases excellent functional group compatibility and late-stage derivatization potential, offering new insights and avenues for the synthesis of ATAA analogs.

A radar array expansion design method based on modular subarray layout

Abstract This paper introduces a design method for expandable subarray structures used in phased array radar arrays. Based on the structural characteristics of modular subarray layout for large radar arrays, this paper analyzes the assembly dimension chain tolerance based on subarray expansion. One third of the allowable deviation of the radar array is used as the subarray design tolerance, and the size tolerance of each installation surface of the subarray is designed according to the design tolerance. Finally, the subarray array is assembled into any size of radar array, and the probability of the radar array assembly accuracy meeting the allowable deviation is 99.73%. For large radar arrays, adopting this design method can significantly reduce the tolerance span between the sub array and the area array, greatly reducing the difficulty of design and processing. This paper provides a fundamental design method for the expansion design of radar arrays with similar systems, which has universal applicability.

Palladium-Catalyzed Cross-Electrophile Couplings of Aryl Thianthrenium Salts with Aryl Bromides via C-S Bond Activation.

We report here a step-economic and cost-effective cross-electrophile coupling of aryl thianthrenium salts with widely available aryl bromides, which proceeded effectively via C-S bond activation at ambient temperature in THF in the presence of a palladium catalyst, magnesium turnings, and lithium chloride to enable the facile assembly of a wide array of structurally diverse biaryls in modest to good yields with good functional group compatibility. In addition, the gram-scale reaction could also be realized.

Plasmonic array at liquid-liquid interface for trace microplastics detection

Microplastics (MPs) pollution has become a focal point of global concern, as the widespread distribution of MPs in the environment poses a potential threat to ecosystems and human health. Despite surface-enhanced Raman scattering (SERS) being one of the most promising detection techniques, the “coffee ring effect” of MPs and their unique size scale make effective contact with SERS substrates challenging. Here, we propose a novel strategy for MPs detection by constructing a plasmonic metasurface at the liquid-liquid interface (LLI). The fluidic properties of LLI provide more flexibility for the uniform dispersion of MPs and the assembly of plasmonic arrays. MPs are captured and assembled on an atomic-level metasurface in a core-shell structure (AuNPs@MPs), providing abundant “hot spots” and additional volume-enhanced Raman effects. This results in enhanced electromagnetic field around MPs and increased enhancement factors, demonstrating high SERS sensitivity and uniformity. This sensing platform provides a new approach for trace detection of MPs and has been validated in practical matrix.

Facile and Rapid Microcontact Printing of Additive-Free Polydimethylsiloxane for Biological Patterning Diversity.

The development and application of micropatterning technology play a promising role in the manipulation of biological substances and the exploration of life sciences at the microscale. However, the universally adaptable micropatterning method with user-friendly properties for acceptance in routine laboratories remains scarce. Herein, a green, facile, and rapid microcontact printing method is reported for upgrading popularization and diversification of biological patterning. The three-step printing can achieve high simplicity and fidelity of additive-free polydimethylsiloxane (PDMS) micropatterning and chip fabrication within 8 min as well as keep their high stability and diversity. A detailed experimental report is provided to support the advanced microcontact printing method. Furthermore, the applications of easy-to-operate PDMS-patterned chips are extensively validated to complete microdroplet array assembly with spatial control, cell pattern formation with high efficiency and geometry customization, and microtissue assembly and biomimetic tumor construction on a large scale. This straightforward method promotes diverse micropatternings with minimal time, effort, and expertise and maximal biocompatibility, which might broaden its applications in interdisciplinary scientific communities. This work also offers an insight into the establishment of popularized and market-oriented microtools for biomedical purposes such as biosensing, organs on a chip, cancer research, and bioscreening.

Optical assembly of multi-particle arrays by opto-hydrodynamic binding of microparticles close to a one-dimensional chain of magnetic microparticles.

Two-dimensional materials possess a large number of interesting and important properties. Various methods have been developed to assemble two-dimensional aggregates. Assembly of colloidal particles can be achieved with laser-heating-induced thermal convective flow. In this paper, an opto-hydrodynamic binding method is proposed to assemble colloidal particles dispersed in a solution into multilayer structures. First, we use polystyrene (PS) microspheres to study the feasibility and characteristics of the assembly method. PS microspheres and monodispersed magnetic silica microspheres (SLEs) are dispersed in a solution to form a binary mixture system. Under the action of an external uniform magnetic field, SLEs in the solution form chains. An SLE chain is heated by a laser beam. Due to the photothermal effect, the SLE chain is heated to produce a thermal gradient, resulting in thermal convection. The thermal convection drives the PS beads to move toward the heated SLE chain and finally stably assemble into multilayer aggregates on both sides of the SLE chain. The laser power affects the speed and result of the assembly. When the laser power is constant, the degree of constraint of the PS microbeads in different layers is also different. At the same time, this method can also assemble the biological cells, and the spacing of different layers of cells can be changed by changing the electrolyte concentration of the solution. Our work provides an approach to assembling colloidal particles and cells, which has a potential application in the analysis of the collective dynamics of microparticles and microbes.

Assembly and Alignment of High Packing Density Carbon Nanotube Arrays Using Lithographically Defined Microscopic Water Features.

High packing density aligned arrays of semiconducting carbon nanotubes (CNTs) are required for many electronics applications. Past work has shown that the accumulation of CNTs at a water-solvent interface can drive array self-assembly. Previously, the confining interface was a large-area, macroscopic feature. Here, we report on the CNT assembly on microscopic water features. Water microdroplets are formed on 10-100 μm wide hydrophilic stripes patterned on a substrate. Exposure to CNTs dispersed in solvent accumulates CNTs at the microdroplet-solvent interface, driving their alignment and deposition at the microdroplet-solvent-substrate contact line. Compared with macroscopic methods in which the contact line uncontrollably moves across the substrate as it is pulled out of the liquids, the hydrophilic patterns and microdroplets allow pinning of the contact line. As CNTs deposit, the contact line self-translates, allowing for dense CNT packing. We realize monolayer CNT arrays aligned within ±3.9° at density of 250 μm-1 and field effect transistors with a high current density of 1.9 mA μm-1 and transconductance of 1.2 mS μm-1 at -0.6 V drain bias and 60 nm channel length.

Performance-Enhanced Flexible Self-Powered Tactile Sensor Arrays Based on Lotus Root-Derived Porous Carbon for Real-Time Human-Machine Interaction of the Robotic Snake.

Flexible tactile sensors play an important role in the development of wearable electronics and human-machine interaction (HMI) systems. However, poor sensing abilities, an indispensable external energy supply, and limited material selection have significantly constrained their advancement. Herein, a self-powered flexible triboelectric sensor (TES) is proposed by integrating lotus-root-derived porous carbon (PC) into polydimethylsiloxane (PDMS). Owing to the superior charge capturing capability of PC, the PDMS/PC (PPC)-based TES exhibits an open-circuit voltage (Voc) of 22.8 V when it is periodically patted by skin at the pressure of 2 N and the frequency of 1 Hz, which is 5 times higher than that of a pristine PDMS-based TES. Furthermore, the as-prepared self-powered TES exhibits a high sensitivity of 3.24 V kPa-1 below 15 kPa for detecting human motion signals, such as finger clicks, joint bends, etc. Last but not the least, after the assembly of a PPC-based TES array and construction of an HMI system, the robotic snake can be controlled remotely by recognizing finger touching signals. This work shows broad potential applications for the self-powered TES in the fields of intelligent robotics, flexible electronics, disaster relief, and intelligence spying.

Recent Advances in Cyclization Reactions of 1,6‐Enynes

AbstractElaborated molecular architectures, specifically those bearing one or more carbon stereocenters, stand as an important class of carbocyclic and heterocyclic frameworks because they are frequently occurring core structures in numerous natural products and biologically active pharmaceutical molecules. Over the past few decades, the development of versatile synthetic approaches via cascade cyclization reactions of 1,6‐enynes for the construction of a series of fused and spiro compounds has been the focus of a great deal of research initiatives. These synthesis strategies are peculiarly fascinating in the context of the assembly of a wide array of pharmaceutical molecules, natural products, agrochemicals, and functional materials. In this review, recent developments in the transformations of 1,6‐enynes with diverse coupling reagents are summarized since 2018, which could be divided into five categories: 1) Introduction; 2) Transition metal catalyzed cyclization of 1,6‐enynes; 3) Metal‐free cyclization of 1,6‐enynes; 4) Visible‐light‐induced cyclization of 1,6‐enynes; 5) Electrocatalytic cyclization of 1,6‐enynes.

Standardized Iterative Genome Editing Method for Escherichia coli Based on CRISPR-Cas9.

The introduction of complex biosynthetic pathways into the hosts' chromosomes is gaining attention with the development of synthetic biology. While CRISPR-Cas9 has been widely employed for gene knock-in, the process of multigene insertion remains cumbersome due to laborious and empirical gene cloning procedures. To address this, we devised a standardized iterative genome editing system for Escherichia coli, harnessing the power of CRISPR-Cas9 and MetClo assembly. This comprehensive toolkit comprises two fundamental elements based on the Golden Gate standard for modular assembly of sgRNA or CRISPR arrays and donor DNAs. We achieved a gene insertion efficiency of up to 100%, targeting a single locus. Expression of tracrRNA using a strong promoter enhances multiplex genomic insertion efficiency to 7.3%, compared with 0.76% when a native promoter is used. To demonstrate the robust capabilities of this genome editing toolbox, we successfully integrated 5-10 genes from the coenzyme B12 biosynthetic pathway ranging from 5.3 to 8 Kb in length into the chromosome of E. coli chassis cells, resulting in 14 antibiotic-free, plasmid-free producers. Following an extensive screening process involving genes from diverse sources, cistronic design modifications, and chromosome repositioning, we obtained a recombinant strain yielding 1.49 mg L-1 coenzyme B12, the highest known titer achieved by using E. coli as the producer. Illuminating its user-friendliness, this genome editing system is an exceedingly versatile tool for expediently integrating complex biosynthetic pathway genes into hosts' genomes, thus facilitating pathway optimization for chemical production.

Molecular-level periodic arrays of long-chain poly(3-hexylthiophene-2,5-diyl) driven by an electric field.

Two-dimensional (2D) periodic arrays of conductive polymers represent attractive platforms for wiring functional molecules into the integrated circuits of molecular electronics. However, the large-scale assembly of polymer periodic arrays at the molecular level faces challenges such as curling, twisting, and aggregation. Here, we assembled the periodic arrays of long-chain poly(3-hexylthiophene-2,5-diyl) (P3HT, Mw = 65 k) at the solid-liquid interface by applying an electric field, within which the charged chain segments were aligned. Atomic force microscopy (AFM) imaging revealed that individual P3HT chains assemble into monolayers featuring face-on orientation, extended chain conformation and isolated packing, which is thermodynamically more stable than folded chains in 2D polycrystals. The assembly process is initiated with the formation of disordered clusters and progresses through voltage-dependent nucleation and growth of extended-chain arrays, wherein continuous conformational adjustments along the nucleation pathway exhibit dependence on the cluster size.

Optimal Design of Thermal Cycling Reliability for Plastic Ball Grid Array Assembly Via Finite Element Method and Taguchi Method

Abstract A finite element simulation analysis model was developed for a plastic ball grid array (PBGA) assembly to analyze its behavior under thermal cyclic loading conditions. The stress distribution in the SAC305 solder joints at different locations within the array was investigated by using ANAND constitutive equations. Subsequently, the thermal fatigue life of the key solder joints was quantified. The study also examined the influence of the solder joint diameter, substrate thickness, solder joint height, printed circuit board (PCB) thickness, and mold compound height on solder joint stress. Optimization of assembly parameters was achieved through the application of the Taguchi method. An extensive analysis was conducted using different assembly parameter combinations, employing the L9(34) orthogonal array design to explore the thermal cycling effects. The computed average Von Mises stress Δσ for the critical thin-layer elements of solder joints located in hazardous positions within the assembly was notably affected by variations in the solder joint height, substrate thickness, solder joint diameter, and mold compound height. This impact ranked in descending order of significance as solder joint height, substrate thickness, solder joint diameter, and mold compound height. The optimal parameter combination determined was a solder joint height of 0.70 mm, a solder joint diameter of 0.85 mm, a substrate thickness of 0.51 mm, and a mold compound height of 1.12 mm. Implementing this optimized configuration led to a significant 4.07% reduction in average stress Δσ for the critical thin-layer elements within hazardous solder joints. Moreover, the extension of the thermal fatigue life was notably improved, achieving an impressive 51.72% increase.

Solder Flux Evolution for Heterogeneous Integration

Advanced packaging techniques continue to evolve within the semiconductor industry. Within advanced packaging, heterogeneous integration has become a solution for those wishing to integrate distinct and complex dies into smaller packages. Many application trends are emerging to meet the challenges of heterogeneous integration which are causing the assembly process to become more intricate, with these trends requiring soldering material technology, especially that of solder flux, to be up to date and cutting-edge. In this paper, three assembly processes that necessitate advanced solder flux will be discussed: flip-chip assembly, BGA ball-attach assembly, and assemblies which have advanced to necessitate fluxless component attach. First, flip-chip assembly methods will be discussed and how different assembly technologies, such as standard mass reflow, thermocompression bonding (TCB), and laser assisted bonding (LAB), require differently formulated fluxes. This paper will then discuss the ball grid array assembly process, first outlining common process steps which negatively affect the solderability of ball-grid array pads, such as flip-chip reflow and molding compound applications, then discuss advancements in ball-attach fluxes which help eliminate these extra process steps, or ‘prefluxing’ steps. Finally, this paper will then discuss assembly trends which have led to fluxless component attach, and will discuss materials designed for fluxless processes, such as formic acid reflow, and how these fluxless processes tie into flip-chip assembly.

Shape-Anisotropic Assembly of Protein Nanocages with Identical Building Blocks by Designed Intermolecular π-π Interactions.

Protein lattices that shift the structure and shape anisotropy in response to environmental cues are closely coupled to potential functionality. However, to design and construct shape-anisotropic protein arrays from the same building blocks in response to different external stimuli remains challenging. Here, by a combination of the multiple, symmetric interaction sites on the outer surface of protein nanocages and the tunable features of phenylalanine-phenylalanine interactions, a protein engineering approach is reported to construct a variety of superstructures with shape anisotropy, including 3D cubic, 2D hexagonal layered, and 1D rod-like crystalline protein nanocage arrays by using one single protein building block. Notably, the assembly of these crystalline protein arrays is reversible, which can be tuned by external stimuli (pH and ionic strength). The anisotropic morphologies of the fabricated macroscopic crystals can be correlated with the Å-to-nm scale protein arrangement details by crystallographic elucidation. These results enhance the understanding of the freedom offered by an object's symmetry and inter-object π-π stacking interactions for protein building blocks to assemble into direction- and shape-anisotropic biomaterials.