Geometry Analysis in Screen-Printed Stretchable Interconnects

Mosallaei, Mahmoud; Jokinen, Jarno; Honkanen, Mari; Iso-Ketola, Pekka; Vippola, Minnamari; Vanhala, Jukka; Kanerva, Mikko; Mäntysalo, Matti

doi:10.1109/tcpmt.2018.2854635

Cited by 13 publications

(24 citation statements)

References 29 publications

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“…Scientific RepoRtS | (2020) 10:12037 | https://doi.org/10.1038/s41598-020-68871-w www.nature.com/scientificreports/ stretch tensor, U 49 . The same kind of potential, with N = 2 , was used in a previous publication to successfully describe the behaviour of this TPU material 23 . However, Ogden's model with N = 3 is generally acknowledged as one of the most widely used for characterization of material behaviour under large deformations 50 .…”

Section: Methodsmentioning

confidence: 99%

“…The parameters used to describe the substrate behaviour were set equal to the values in Supplementary Table S3 , while the terms , and are defined as principal stretches, defined as the eigenvalues of the right stretch tensor, 49 . The same kind of potential, with , was used in a previous publication to successfully describe the behaviour of this TPU material 23 . However, Ogden’s model with is generally acknowledged as one of the most widely used for characterization of material behaviour under large deformations 50 .…”

Section: Methodsmentioning

confidence: 99%

“…As seen in previous publications regarding the presence of interconnects on stretchable electronic systems, it is possible to influence local strain through encapsulation and by modifying the geometry of the conductive ink interconnect 8,23 . In addition, vulnerable regions in the substrate, such as areas with rigid-to-soft connections can be reinforced by local enhancement of the stiffness 45,46 .…”

Section: Mechanically Driven Strategies To Improve Electromechanical mentioning

confidence: 99%

“…These classes of conductive composites offer high flexibility of properties and many advantages over the thin metallic films that are generally used in this field. Moreover, they can be printed on top of the desired substrate, which can range from thermoplastic polyurethanes (TPUs) 8,23 and polydimethylsiloxanes (PDMS) 24,25 to textiles 26,27 . However, conduction in these materials is based on deformation mechanisms that are radically different from the ones available for thin metallic films: in fact, for these materials conduction is carried through the filler particles, that are in contact with each other and act as rigid inclusions, while the polymeric binder typically carries the deformation transferred from the substrate.…”

Section: Mechanically Driven Strategies To Improve Electromechanical mentioning

confidence: 99%

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Mechanically driven strategies to improve electromechanical behaviour of printed stretchable electronic systems

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Mosallaei

Khorramdel

et al. 2020

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Stretchable electronics promise to extend the application range of conventional electronics by enabling them to keep their electrical functionalities under system deformation. Within this framework, development of printable silver-polymer composite inks is making possible to realize several of the expected applications for stretchable electronics, which range from seamless sensors for human body measurement (e.g. health patches) to conformable injection moulded structural electronics. However, small rigid electric components are often incorporated in these devices to ensure functionality. Under mechanical loading, these rigid elements cause strain concentrations and a general deterioration of the system’s electrical performance. This work focuses on different strategies to improve electromechanical performance by investigating the deformation behaviour of soft electronic systems comprising rigid devices through Finite Element analyses. Based on the deformation behaviour of a simple stretchable device under tensile loading, three general strategies were proposed: local component encapsulation, direct component shielding, and strain dispersion. The FE behaviour achieved using these strategies was then compared with the experimental results obtained for each design, highlighting the reasons for their different resistance build-up. Furthermore, crack formation in the conductive tracks was analysed under loading to highlight its link with the evolution of the system electrical performance.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Mechanically Driven Strategies To Improve Electromechanical mentioning

confidence: 99%

Section: Mechanically Driven Strategies To Improve Electromechanical mentioning

confidence: 99%

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Mechanically driven strategies to improve electromechanical behaviour of printed stretchable electronic systems

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Mosallaei

Khorramdel

et al. 2020

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“…Based on the type and functionality of the device, the conductivity should be maintained either during stretching, or when they return to the initial state. A number of parameters can affect the robustness of interconnects; these include the material, adhesion between the substrate and the conductive coating, and the geometry of the conductive material [12].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Encapsulation Geometry on the Performance of Stretchable Interconnects

et al. 2018

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The stretchability of electronic devices is typically obtained by tailoring the stretchable interconnects that link the functional units together. The durability of the interconnects against environmental conditions, such as deformation and chemicals, is therefore important to take into account. Different approaches, including encapsulation, are commonly used to improve the endurance of stretchable interconnects. In this paper, the geometry of encapsulation layer is initially investigated using finite element analysis. Then, the stretchable interconnects with a narrow-to-wide layout are screen-printed using silver flake ink as a conductor on a thermoplastic polyurethane (TPU) substrate. Printed ultraviolet (UV)-curable screen-printed dielectric ink and heat-laminated TPU film are used for the encapsulation of the samples. The electromechanical tests reveal a noticeable improvement in performance of encapsulated samples compared to non-protected counterparts in the case of TPU encapsulation. The improvement is even greater with partial coverage of the encapsulation layer. A device with a modified encapsulation layer can survive for 10,000 repetitive cycles at 20% strain, while maintaining the electrical and mechanical performance.

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Failure Mechanisms in Flip‐Chip Bonding on Stretchable Printed Electronics

et al. 2021

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Growing advances in printed flexible electronics enable novel design and manufacturing processes of electrical circuits and components in aircraft and automotive industries, [1][2][3] as well as in consumer electronics for fabrication of printed passive components, semiconductor devices, and sensing elements. [4][5][6][7][8][9][10][11][12][13][14][15] In the healthcare domain, the impact of printed electronics becomes more profound and offers a wide range of applications from printed RF coils for medical imaging, [16] biochemical sensing, [17,18] vital sign monitoring [19][20][21][22][23][24][25] to assistive wearable devices. [26,27] At the industrial level, its low cost and high-throughput manufacturing process are the key motivators for transition from conventional solutions to printed technologies. In wearable applications, its capability to realize soft wearable sensors, which can comply with the dynamic deformations of human skin, is attractive.Despite the promising opportunities of printed electronics in different domains, there are concerns regarding the reliability of printed materials (i.e., conductive inks, isolators, and adhesives) and their interconnections to electronic components for longterm use in real-life applications. Over the past decade, there has been an increasing number of studies on the reliability of printed conductors, interconnections, and chip-on-flex assembly. As a fundamental test, the cyclic bending endurance of printed conductors was investigated to analyze the characteristics of conductive tracks on a flexible substrate. [28][29][30] In more complicated test protocols, the influence of environmental parameters (e.g., temperature, humidity, etc.) was included in the test procedure. [31] More advanced test setups and protocols were developed to evaluate the reliability of complex hybrid integration of chip-on-flex, flexto-flex assemblies, and roll-to-roll (R2R) printed circuits. [32][33][34] This work presents a comprehensive study on the reliability of hybrid integration of thinned bare die chip on soft and stretchable substrate. More specifically, the findings of this study are expected to provide fundamental insights on the failure mechanisms, their corresponding contributors, and ways to minimize them. This study is divided into three phases as shown in Figure 1A. In the screening phase, the electromechanical performance of five different ink variants is evaluated and the most suitable ink variants are selected to be used in combination with three different types of conductive adhesive for fabrication and assembly of the test device. In the last phase of the study, the fabricated test devices are tested through a cyclic strain test and a comprehensive analysis of failure mechanisms is performed. The importance of the failure analysis is recognized in refining of the design steps, material selection, and processing parameters for improved reliability.

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Geometry Analysis in Screen-Printed Stretchable Interconnects

Cited by 13 publications

References 29 publications

Mechanically driven strategies to improve electromechanical behaviour of printed stretchable electronic systems

Mechanically driven strategies to improve electromechanical behaviour of printed stretchable electronic systems

The Effect of Encapsulation Geometry on the Performance of Stretchable Interconnects

Failure Mechanisms in Flip‐Chip Bonding on Stretchable Printed Electronics

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