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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - A cost-effective and high performance assembly technology for interconnecting the Cu/Al bilayer electrode and lead wire of ZnO varistor using a low Ag-containing solder paste
摘要： In this paper, the spreading ability of solder pastes with different Ag contents on Ag and Cu/Al bilayer electrodes was investigated in detail. The mechanical performance (i.e., stripping force) and microstructure of 'lead-wire/solder/electrode/ZnO' joints were characterized. The electrical property of ZnO varistors soldered by various solder pastes was also analysed. Results show that the low Ag-containing solder paste with the assistance of the flux having appropriate activity exhibits similar spreading ability on Ag and Cu/Al bilayer electrodes with the high Ag-containing solder paste. Moreover, the difference in Ag content of solder pastes has little influence on the stripping force of the solder joints and the surge performance of ZnO varistors. High activity of the solder paste may lead to severe corrosion of Ag electrode and decrease in the stripping force of the joints, and low activity of the solder paste brings the problem of inadequate removal of oxide films on the Cu/Al bilayer electrode, which leads to poor soldering quality and lower stripping force of the joints. ZnO varistors with Cu/Al bilayer electrodes have superior surge performance over those with Ag electrodes.
关键词： Cu/Al bilayer electrode,ZnO varistor,mechanical performance,spreading ability,low Ag-containing solder paste
更新于2025-09-23 15:22:29
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Generation of graded porous structures by control of process parameters in the selective laser melting of a fixed ratio salt-metal feedstock
摘要： The demonstration of salt dissolution incorporated within laser powder-bed fusion fabrication processes has allowed the creation of complex porous structures without the need for sophisticated design algorithms. This serves to simplify the process, for porous structure creation in powder-bed fabrication techniques, creating a new opportunity for the realisation of optimised structures. A new methodology is presented here in which modulation of the energy density while using a single feedstock material enables three-dimensional control of porosity, ranging from 20 % to 49 %. Through structured experimentation, the response of the material to varying the process parameters in selective laser melting is evaluated and nested structures of distinct densities and morphologies are created. Correlation of the process parameters with modulus and ultimate compressive stress are established. A simple-assembly algorithm was used to generate complex parts consisting of locally assigned porosities having characteristic properties.
关键词： Selective laser melting,Graded materials,Mechanical performance,Controlled-porosity,Additive manufacturing,Cellular structures,Porous
更新于2025-09-23 15:19:57
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Alginate-graphene oxide hydrogels with enhanced ionic tunability and chemomechanical stability for light-directed 3D printing
摘要： Nanocomposite hydrogels that incorporate 2D carbon nanomaterials could enable augmented and responsive behaviors not observed with polymeric matrices alone. In particular, non-covalent interactions could facilitate enhanced mechanical performance that can be self-recovered with external stimuli. Here, we demonstrate alginate-graphene oxide (GO) hydrogels using a non-covalent, ionic crosslinking mechanism compatible with light-directed 3D printing. We show that alginate-GO hydrogels exhibit improved mechanical performance in shear, compression, and tension, including a two-fold increase in shear modulus, a three-fold decrease in inelastic deformation, and a nine-fold increase in fracture energy relative to alginate-only hydrogels. Moreover, alginate-GO hydrogels are stabilized by hydrogen bonding between nanosheets and remain intact after removal of ionic crosslinkers by chelation. As a consequence, the shear modulus of these nanocomposite hydrogels can be tuned by over 500-fold via external ion concentration. We demonstrate that alginate-GO can be stereolithographically printed into robust, freestanding and overhanging 3D structures. These designer material architectures exhibit outstanding stability and superoleophobicity in high salt solution, which can be used to repel and manipulate a variety of oils. Overall, such nanocomposite hydrogels with engineered non-covalent interactions could enable “smart” multiresponsive and multifunctional devices for aqueous and marine environments.
关键词： Superoleophobicity,Ionic crosslinking,Chemomechanical stability,Graphene oxide,3D printing,Alginate,Nanocomposite hydrogels,Mechanical performance
更新于2025-09-10 09:29:36
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Preparation of ZnO nanoparticle-reinforced polyamide 6 composite by <i>in situ</i> -coproduced method and their properties
摘要： Polyamide 6/ZnO nanocomposites (noted as PA6/ZnO) were prepared by an in situ co-producing method, during which Zn2(OH)2CO3 decomposed into nano-ZnO in the process of the opening-ring polymerization of caprolactam at high temperature. Transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were used to analyze the size and dispersive properties of nano-ZnO, the crystallization and melting properties, the thermal properties, and crystal structure of PA6/ZnO composite, respectively. The results showed that the nano-ZnO derived from Zn2(OH)2CO3 via in situ polymerization of PA6-ZnO was uniformly dispersed in PA6 matrix. However, the overall nano-ZnO crystallization rate and crystal size in the PA6 matrix were hindered by the bulky PA6 molecular chains. The mechanical properties were evaluated using universal tensile and impact testing instruments. The results revealed that PA6/ZnO composite with 0.2% nano-ZnO content possessed excellent tensile strength, enhanced by 75% in comparison with the pure PA6. The nano-ZnO had little influence on the impact strength of PA6.
关键词： friction property,mechanical performance,nanocomposites,polyamide 6,nano-ZnO,polyamides,composite
更新于2025-09-09 09:28:46
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Advanced Materials for Electromagnetic Shielding (Fundamentals, Properties, and Applications) || Mechanical Performance Characterization of EMI Shielding Materials Using Optical Experimental Techniques
摘要： In this chapter, the full field optical experimental methods for characterizing the mechanical performance of EMI shielding materials have been discussed. Interest in this type of physical problem is motivated by its importance in many practical applications. One major disadvantage of the use of optical techniques in characterizing the mechanical performance of EMI shielding materials is their full field and noncontact with the materials. The information outlined in this chapter may help researchers and engineers in their study of the unknown features of related complex systems for technological applications in characterizing EMI shielding materials.
关键词： EMI shielding materials,photoelastic method,digital gradient sensing,mechanical performance,moiré interferometry,digital image correlation,coherent gradient sensing,optical experimental techniques
更新于2025-09-04 15:30:14