Interfacial adhesion between silver ink and thermoplastic polyurethane and electromechanical reliability of flexible printed circuit

Flexible printed circuit (FPC) is one of the promising components in the electronic industries. The advantages of FPC are that its fabrication process is environmentally friendly, low cost, and efficient, which makes it a favourable choice for applications in industrial and medical. The conductive ink and substrate are the main components of FPC and they need to perform with good flexibility as that indicates that it is able to withstand a degree of deformation before occurring loss in conductivity. Nonetheless, issues that arise are interfacial adhesion strength between conductive ink and substrate, and reliability of conductive ink upon exposure to a stretchable type of deformation. Therefore, this study aims to investigate two different adhesion-enhancing techniques, which are thermal control and self-assembled monolayer of adhesion promoter. In addition, reliability of the conductive ink when exposed to stretchable type of deformation is also investigated. The silver conductive ink and thermoplastic polyurethane (TPU) were used in this study. The thermal control technique involved curing printed silver conductive ink at selected temperatures: room temperature, 60oC, 80oC, 100oC, 120oC, 130oC, and 140oC. The TPU underwent thermal analysis by using Differential Scanning Calorimetry (DSC) to study thermal properties of TPU. Meanwhile, self-assembled monolayer technique involved the construction of adhesion promoter layer onto the surface of TPU by dipping it in the adhesion promoter solution. Adhesion promoter used in this study was 3-aminopropyltrimethoxy silane (APTS). The success of the APTS construction was evaluated through Fourier Transform Infrared Spectroscopy (FTIR) and water contact angle (WCA) analysis. The evaluation of adhesion performance was assessed according to the cross-cut test (ASTM D3359) and 180o peel-test. The changes in electrical, mechanical, and surface energy characteristics were carried out within this research to investigate whether these techniques would cause changes in the mentioned properties. The experimental results showed an improvement in adhesion when both methods were executed. The thermal control has 4B/0.22 N/mm to 5B/0.55 N/mm rating when curing started at 100oC to 140oC. APTS-treated TPU showed adhesion was improved to 3B/0.17 N/mm. An increase in conductivity of printed silver with lower hardness was observed when the temperature was elevated. However, insignificant changes in conductivity and hardness were observed for APTS-treated TPU. The surface energy of TPU changed when it was exposed to thermal, showing an insignificant effect in promoting the adhesion. The improvement of adhesion was described as influenced by the changes in thermal properties of TPU. Meanwhile, surface energy of APTS-treated TPU showed polar properties due to the presence of polar head functional groups that allowed affinity bond with the silver particles. Reliability of silver ink was tested by printing with different geometrical patterns (straight, square, sinusoidal, and zig-zag), and different widths (1 mm, 2 mm, and 3 mm). The electromechanical measurement was carried out by manually stretching the pattern until it lost its conductivity. Zig-zag with 3 mm width showed excellent electromechanical performance with 7.78% maximum strain

The Influence Of Geometrical Dimensions On Electromechanical Performance In Stretchable Circuit

Stretchable conductive ink (SCI) had been extensively studied for fabricating stretchable electronic devices. In this study, silver conductive ink and thermoplastic polyurethane (TPU) were used as substrate. The ink was printed on the substrate using screen printing with different shaped patterns varied by the widths of 1 mm, 2 mm and 3 mm: (a) straight, (b) zig-zag, (c) square and (d) sinusoidal. The measurement of resistance was performed using four-point measurement during unloaded and loaded conditions of the shape pattern. This study revealed that width had influenced the resistivity in all shape patterns, where the narrow the width, the higher the resistance is. Comparative studies of electromechanical analysis of the shaped patterns had showed that a 3 mm width of zig-zag pattern had a better electromechanical performance by having stretchability to maximum of 7.78%. Straight and square shape patterns, however, exhibited the poor tolerate deformation as both failed to conduct electricity upon straining at the minimum elongation of 1.11%

Temperature Dependence On Silver Conductivity And Adhesion Performance Between Silver And Flexible Substrate

Printed circuit board (PCB) is the main component in almost all electronic devices. The increase in the demand for PCB cause dramatically increases of E-waste. The improper discard practice of printed circuit board (PCB) leads to human health and environmental problems. Although the study had been done to improve the recycling process of E-waste, awareness from various parties needs more effort for this improved recycling process to successfully implement. Therefore, an alternative way by substitute the conventional PCB with the new flexible PCB can help eliminate these issues. The basic design of a flexible PCB consists of a flexible base and conductor. However, a key point during the developing of this new technology is the adhesion between the flexible base and conductor, which thermoplastic polyurethane (TPU) as the base, while silver as the conductor was used throughout this study. This paper presents the effect of temperature in improving adhesion between substrate and silver, and concurrently influence the electrical conductivity of silver conductor. In this study, the characterization of silver and substrate respected to temperature individually analysed, followed by the qualitative adhesion observation between silver and substrate was carried out through cross-cut test according to ASTM D3359-09. The silver was exposed to different curing temperatures exhibit lower sheet resistance when temperature increase. Meanwhile, the substrate exposed to a temperature higher than glass transition (Tg) increases improve the adhesion between silver and substrat

The Effect Of Temperature On The Electrical Conductivity And Microstructure Behaviour Of Silver Particles

Silver conductive ink has been used in the electronics industry due to their potential advantages such as high electrical conductivity and thermal conductivity. However, silver needs to undergo a curing process to reduce the porosity between particles as well as to have a smooth conductive track to ensure maximum conductivity. Therefore, the effect of temperature on the electrical conductivity and microstructure were explored. The printing of silver conductive paste was executed on a polymer substrate through screen printing before analysis. Next, an electrical analysis was done to measure the conductivity by using a 4-point probes instrument, followed with microstructure and mechanical analysis which were carried out to observe the structure behaviour and hardness of silver respectively with respect to temperature. The study found that the electrical conductivity of silver increases when temperature elevated. Besides that, the microstructure of silver has a larger size with the increase in temperature, correspondingly cause the silver to have less hardness. In conclusion, temperature plays significant roles in increasing the electrical conductivity of silver

TCGA-My: A Systematic Repository for Systems Biology of Malaysian Colorectal Cancer

Colorectal cancer (CRC) ranks second among the most commonly occurring cancers in Malaysia, and unfortunately, its pathobiology remains unknown. CRC pathobiology can be understood in detail with the implementation of omics technology that is able to generate vast amounts of molecular data. The generation of omics data has introduced a new challenge for data organization. Therefore, a knowledge-based repository, namely TCGA-My, was developed to systematically store and organize CRC omics data for Malaysian patients. TCGA-My stores the genome and metabolome of Malaysian CRC patients. The genome and metabolome datasets were organized using a Python module, pandas. The variants and metabolites were first annotated with their biological information using gene ontologies (GOs) vocabulary. The TCGA-My relational database was then built using HeidiSQL PorTable 9.4.0.512, and Laravel was used to design the web interface. Currently, TCGA-My stores 1,517,841 variants, 23,695 genes, and 167,451 metabolites from the samples of 50 CRC patients. Data entries can be accessed via search and browse menus. TCGA-My aims to offer effective and systematic omics data management, allowing it to become the main resource for Malaysian CRC research, particularly in the context of biomarker identification for precision medicine