Damage of Flexible Electronic Line Under Mechanical and Electrical Stress Loading

2021 ◽  
Author(s):  
Ryota Horiuchi ◽  
Kazuhiko Sasagawa ◽  
Kazuhiro Fujisaki

Abstract Flexible printed circuits (FPCs) are widely used in electronic devices such as movable part line or wearable sensor. Inkjet printing is attracting attention because it can draw electric lines of any shape without a photo mask. The mechanical characteristics such as flexibility or durability of electric lines have been evaluated by bending and tensile tests. Moreover, the reliability characteristics of metal particle ink lines under electric current loading have been recently evaluated. However, the electronic line has not been evaluated under both the mechanical stress due to bending deformation and the electrical stress due to electric current. According to scaling down of electric devices, the current density and Joule heat in interconnect line increase and electromigration (EM) damage becomes a serious problem. EM is a transportation phenomenon of metallic atoms caused by electron wind under high-density electric current. Reducing EM damage is extremely important to enhance device reliability. In this study, high-density current loading tests of flexible electronic line were conducted under bending deformation of the substrate in order to investigate the effect of mechanical stress on the EM damage of the electronic line. As the results of current loading tests, the specimens with bending deformation became open circuits in shorter time than that without bending deformation. Therefore, it is considered that the bending deformation is affected on the electric reliability characteristic of the flexible electronic lines reflecting EM damage.

Author(s):  
Daiki Saito ◽  
Kazuhiko Sasagawa ◽  
Takeshi Moriwaki ◽  
Kazuhiro Fujisaki

Abstract Printed electronics (PEs) have attracted attention for the fabrication of microscale electronic circuits. PEs use conductive inks which include metal nanoparticles. The conductive ink can be printed on flexible substrates for wearable devices using ink-jet printers and roll-to-roll methods. With the scaling down of electric devices, the current density and Joule heating in the device lines increase, and electromigration (EM) damage becomes significant. EM is a transportation phenomenon of metallic atoms caused by the electron wind under high-density current. Reducing the EM damage is extremely important to enhance the device reliability. With the progress in miniaturization of the metal nanoparticle ink lines, EM problem needs to be solved for ensuring the reliability of these lines. We know that the formation of aggregates and cathode damages occur due to a current loading. The diffusion path of atoms due to the EM has not been identified under the high-density current loading. In this study, a high-density electric current loading was applied to an Ag nanoparticle line. The line specimens were prepared using a lift-off method. After the current loading tests, observations were conducted using a laser microscope and scanning electron microscope. A local decrease in the line thickness and scale-shaped slit-like voids were observed due to the high-density current loading. Moreover, the microstructure of the line was modified by enlarging the Ag grain. From the results, we identified that a dominant diffusion occurred at the Ag grain boundary due to the EM.


2019 ◽  
Vol 26 (1) ◽  
pp. 34-40
Author(s):  
Teng MA ◽  
Guihong GENG ◽  
Xiaosi SUN ◽  
Xi HAO ◽  
Weixin HAO

The effect of high-density electric current pulse (ECP) on the solidification of Cu-37.4 wt.%Pb monotectic alloy melt was investigated. The microstructure formation mechanisms of ECP were clarified according to liquid metal cluster theory. The results demonstrated that with ECP treatment, the microstructure of Cu-Pb monotectic alloy became finer, the distribution of Pb phase in the matrix was more even and the solute trapping was significantly apparent. Based on the metal liquid cluster theory under ECP, the solid solubility increase result might be due to the salvation clusters increase under the action of pulse current, leading to the binding force increase among solute atoms and solvent atoms. Simultaneously, the aforementioned results were verified through the Differential Scanning Calorimetry (DSC) curve analysis. The results of hardness test, anti-friction test and wear- resistance test show that the ECP can enhance the hardness, improve the properties of anti-friction and wear-resistance of the alloy.


2020 ◽  
Vol 11 (1-2) ◽  
pp. 3-14
Author(s):  
Cassiano MN Romagnolli ◽  
Gabriela P Leite ◽  
Tiago AR Rodrigues ◽  
Carolina L Morelli

Plastic packagings are widely used for several food products. Considering the relatively short service lifetime of this application, it is important to perceive in the search of eco-friendly alternatives to this market, such as polymers from renewable sources, as thermoplastic starch and “green” polyethylene. The incorporation of an antibacterial agent to the packaging can extend food shelf life. Camellia sinensis is a plant with known antibacterial properties used in the preparation of “green tea.” In the present work, green tea was incorporated to a blend of cassava thermoplastic starch and high-density polyethylene (HDPE) by melt extrusion, aiming application as active packaging. Films were obtained by thermopressing and characterized through infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and tensile tests. Their antibacterial properties were evaluated against Staphylococcus aureus and Escherichia coli. The results indicated that the material developed has potential for food packaging applications. Moreover, the methodology applied for green tea incorporation in the Starch/HDPE films can be extended for many extracts from natural components, contributing to the advancement of research in the development of active packaging for food products. To the best of our knowledge, no previous work studied the properties of starch/HDPE blend with green tea.


2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Daiki Saito ◽  
Kazuhiko Sasagawa ◽  
Takeshi Moriwaki ◽  
Kazuhiro Fujisaki

Abstract Flexible printed circuits (FPCs) are widely used in electronic equipment such as mobile devices and wearable sensors. The conductive electric lines in these circuits are printed using nanoparticle metal ink and ink-jet direct write methods. Physical characteristics such as flexibility and mechanical durability of metal nanoparticle ink lines have been evaluated by bending or tensile tests. In contrast, the electrical characteristics of these lines have not been sufficiently evaluated, and the failure mechanism under high-density current has not been clarified. When electric devices are scaled down, current density and Joule heating increase in conductive lines and electromigration (EM) damage becomes a severe problem. Therefore, reducing the EM damage is extremely important to enhance the device reliability. In this study, a failure analysis of Ag nanoparticle ink lines were assessed using current loading tests and microscopic observations to discuss the damage mechanism and evaluate electrical reliability under high-density current. Atomic transport due to EM was observed at 60 kA/cm2 current loading, and relatively large aggregates and grain growth were observed at 120 kA/cm2 current loading. The time to open circuit was longer at 120 kA/cm2 than at 60 kA/cm2. The formation of large aggregates and unstable changes in the potential drop were observed at the two values of current density. It is considered that aggregate formation and grain growth affected the atomic transport by EM.


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