다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

A strain sensor has been fabricated from a polymer nanocomposite with multiwalled carbon nanotube (MWNT) fillers. The piezoresistivity
of this nanocomposite strain sensor has been investigated based on an improved three-dimensional (3D) statistical resistor network
model incorporating the tunneling effect between the neighboring carbon nanotubes (CNTs), and a fiber reorientation model. The
numerical results agree very well with the experimental measurements. As compared with traditional strain gauges, much higher sensitivity
can be obtained in the nanocomposite sensors when the volume fraction of CNT is close to the percolation threshold. For a small
CNT volume fraction, weak nonlinear piezoresistivity is observed both experimentally and from numerical simulation. The tunneling
effect is considered to be the principal mechanism of the sensor under small strains.

Tunneling effect in a polymer/carbon nanotube nanocompositestrain sensor

A review : On the development of low melting temperature Pb-free solders

Composite lead-free solders, containing micro and nano particles, have been widely studied. Due to grain boundary drag or Zener drag, these particles can refrain the solder microstructure from coarsening in services, especially for Cu6Sn5, Ag3Sn intermetallic compounds and the β-Sn phases. Due to dispersion hardening or dislocation drag, the mechanical properties of the composite solder alloys were enhanced significantly. Moreover, these particles can influence the rate of interfacial reactions, and some particles can transform into a layer of intermetallic compound. Wettability, creep resistance, and hardness properties were affected by these particles. A systematic review of the development of these lead-free composite solders is given here, which hopefully may find applications in microbumps to be used in the future 3D IC technology.

Structure and properties of lead-free solders bearing micro and nano particles

The implementation of additive manufacturing technology (e.g., digital printing) to the electronic packaging segment has recently received increasing attention. In almost all types of Fan-out wafer level packaging (FOWLP), redistribution layers (RDLs) are formed by a combination of photolithography, sputtering and plating process. Alternatively, in this study, inkjet-printed RDLs were introduced for FOWLP. In contrast to a subtractive method (e.g., photolithography), additive manufacturing techniques allow depositing the material only where it is desired. In the current study, RDL structures for different embedded modules were realized by inkjet printing and further characterized by electrical examinations. It was proposed that a digital printing process can be a more efficient and lower-cost solution especially for rapid prototyping of RDLs, since several production steps will be skipped, less material will be wasted and the supply chain will be shortened.

https://www.mdpi.com/2504-3900/2/13/703/pdf

The Realization of Redistribution Layers for FOWLP by Inkjet Printing

In this study, the effects of CeO2 nanoparticle addition on tensile strength and formation of interfacial intermetallic compound layer for lead-free Sn-3.5Ag-0.7Cu solder joint were investigated. The results showed that the thickness of intermetallic layer was decreased with increasing weight percentages of CeO2 reinforcements, and the growth of the intermetallic layer was remarkably suppressed during isothermal aging at 150 °C. It was also found that the tensile strength of the solder joint gradually increased with the addition of CeO2 particles, reached to the maximum value at 0.5 wt% CeO2 and then decreased drastically with further increase in CeO2 content. Microstructural investigation of 1 wt% CeO2 reinforced solder joint revealed that due to particle pushing under the influence of interfacial tension between the particles and the matrix, the brittle cluster-like regions with high concentration of CeO2 particles were formed inside the joint. These brittle clusters act as preferential site for crack initiation during tensile test which would degrade the tensile strength. Hence, based on the results obtained in this study, addition of CeO2 particles up to 0.5 wt% provide an optimized solder joint with improved strength together with suppressed intermetallic growth and long-term reliability.

Formation of intermetallic reaction layer and joining strength in nano-composite solder joint

In this research, the welding characteristics of a new UHSLA steel, 35NiCrMoV123, have been studied in two general conditions (annealed and quench-tempered). Carbon equivalent value of 35NiCrMoV123 steel is near 0.9 which classifies it as a “very difficult to weld” steel. The effects of welding heat treatment cycle (preheat, interpass, and postheat) on metallurgical and mechanical properties of weldments have been investigated by tensile, impact toughness, and hardness tests, as well as optical microscopy observations. It has been observed that by employing high-temperature stress relief (600 °C), welding could be performed in annealed condition successfully. Also, the results indicate that by applying precise welding heat treating cycle (preheat, interpass, and postheat temperature at 310 °C) in order to obtain lower bainitic microstructure in HAZ, also employing high-temperature stress relief (600 °C), welding in quench-tempered condition could be successfully performed.

Welding Characteristics of Ultrahigh Strength Steel in Annealed and Quench-Tempered Conditions

Although considerable research has been dedicated to the synthesis and characterization of lead-free nanoparticle solder alloys, only very little has been reported on the reliability of the respective joints. In fact, the merit of nanoparticle solders with depressed melting temperatures close to the Sn-Pb eutectic temperature has always been challenged when compared with conventional solder joints, especially in terms of inferior solderability due to the oxide shell commonly present on the nanoparticles, as well as due to compatibility problems with common fluxing agents. Correspondingly, in the current study, Sn-Ag-Cu (SAC) nanoparticle alloys were combined with a proper fluxing vehicle to produce prototype nanosolder pastes. The reliability of the solder joints was successively investigated by means of electron microscopy and mechanical tests. As a result, the optimized condition for employing nanoparticles as a competent nanopaste and a novel procedure for surface treatment of the SAC nanoparticles to diminish the oxide shell prior to soldering are being proposed.

/pdf/sn-ag-cu-nanosolders-solder-joints-integrity-and-strength-29k4xfpgtg.pdf

Sn-Ag-Cu Nanosolders: Solder Joints Integrity and Strength

In light of the necessity to introduce reliable interconnection technologies for the development of disposable diagnostic kits, fine-pitch flip-chip integration of bare silicon dies on the paper and polyethylene terephthalate (PET)-based substrates have gained increasing importance. As the key-enabler of a hybrid electronic system, the interconnection technology should provide reliable electrical and mechanical properties. Paper and PET are temperature- and pressure-sensitive, and are not compatible with the conventional flip-chip bonding technologies, i.e., soldering and thermo-compression bonding. In this study, the feasibility of implementing Anisotropic Conductive Films (ACF) in hybrid integration was assessed, in which bare silicon dies with the thicknesses of 30 µm and 730 µm were bonded to screen-printed paper and PET substrates. As an alternative to direct bare die bonding, the integration of PET- and paper-based interposers to printed substrates was also addressed here. Correspondingly, the long-term reliability of the ACF-bonded samples was assessed via dynamic bend cycling tests. It was shown that ACF provides robust and reliable interconnects on both substrates with a failure cycle of more than 45,000 cycles.

Ali Roshanghias

Papers

The Realization of Redistribution Layers for FOWLP by Inkjet Printing

Formation of intermetallic reaction layer and joining strength in nano-composite solder joint

Welding Characteristics of Ultrahigh Strength Steel in Annealed and Quench-Tempered Conditions

Sn-Ag-Cu Nanosolders: Solder Joints Integrity and Strength

ACF bonding technology for paper- and PET-based disposable flexible hybrid electronics