Mechanical and electrical properties of ultra-thin chips and flexible electronics assemblies during bending

Ende, D. A. van den; Wiel, H. J. van de; Kusters, Roel; Sridhar, Ashok; Schram, Jeroen; Cauwe, Maarten; Brand, Jeroen van den

doi:10.1016/j.microrel.2014.07.125

Cited by 35 publications

(24 citation statements)

References 15 publications

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“…The strength of UTCs varies with the methods adopted to obtain them. 30,43 For example, the 15-20 lm thick plasma treated UTCs have the highest strength of 2.34 GPa and can bend to R min ¼ 2.5 mm. On the other hand, the UTCs obtained by grinding and polishing can be deformed up to R min ¼ 33 mm.…”

Section: Ultra-thin Chips and Mechanical Bendingmentioning

confidence: 99%

“…4(b)] tests have revealed that the blank (i.e., without active electronics) UTCs are mechanically stronger than those with CMOS circuitry. 43,53,55,56 UTCs can experience different types of deformations such as tension (the body is subjected to pull), compressive (the body is under compression), shearing (when the external load tends to make a part of the body to slide on the other one), and torsional (when the external load tends to twist the body around an axis). 68 These deformation can be quantified in terms of stresses and strains having components such as uniaxial, biaxial, and torsional, as shown in Fig.…”

Section: Ultra-thin Chips and Mechanical Bendingmentioning

confidence: 99%

“…[72][73][74] A comparison of Young's modulus E and the Poisson's ratio 68 of several materials frequently used in flexible electronics [e.g., singlecrystal Si, hydrogenated amorphous (a-Si:H), hydrogenated nanocrystalline Si (nc-Si:H), polycrystalline Si, Kapton V R , and polyethylene naphthalate (PEN)] is given in Table I. [75][76][77][78][79][80][81][82] The experimental techniques that have been used to study mechanical aspects of UTCs include (i) direct methods 83,84 such as xray diffraction 85,86 and micro-Raman spectroscopy 87,88 and (ii) indirect methods based on measuring the curvature 89 (e.g., optical interferometry, 90 laser scanning, 91,92 and microscope image monitoring in real time 43 ). The subsection below presents the uniaxial and biaxial bending in UTCs.…”

Section: Ultra-thin Chips and Mechanical Bendingmentioning

confidence: 99%

“…The parameters are measured experimentally 43 or determined theoretically from FEM simulations 102 and x 3 is the coordinate along the out-of-plane direction.…”

Section: A Uniaxial Bending Of Utcsmentioning

confidence: 99%

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Bending induced electrical response variations in ultra-thin flexible chips and device modeling

Heidari

Wacker

Dahiya

2017

Applied Physics Reviews

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Electronics that conform to 3D surfaces are attracting wider attention from both academia and industry. The research in the field has, thus far, focused primarily on showcasing the efficacy of various materials and fabrication methods for electronic/sensing devices on flexible substrates. As the device response changes are bound to change with stresses induced by bending, the next step will be to develop the capacity to predict the response of flexible systems under various bending conditions. This paper comprehensively reviews the effects of bending on the response of devices on ultra-thin chips in terms of variations in electrical parameters such as mobility, threshold voltage, and device performance (static and dynamic). The discussion also includes variations in the device response due to crystal orientation, applied mechanics, band structure, and fabrication processes. Further, strategies for compensating or minimizing these bending-induced variations have been presented. Following the in-depth analysis, this paper proposes new mathematical relations to simulate and predict the device response under various bending conditions. These mathematical relations have also been used to develop new compact models that have been verified by comparing simulation results with the experimental values reported in the recent literature. These advances will enable next generation computer-aided-design tools to meet the future design needs in flexible electronics.

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Section: Ultra-thin Chips and Mechanical Bendingmentioning

confidence: 99%

Section: Ultra-thin Chips and Mechanical Bendingmentioning

confidence: 99%

Section: Ultra-thin Chips and Mechanical Bendingmentioning

confidence: 99%

“…The parameters are measured experimentally 43 or determined theoretically from FEM simulations 102 and x 3 is the coordinate along the out-of-plane direction.…”

Section: A Uniaxial Bending Of Utcsmentioning

confidence: 99%

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Bending induced electrical response variations in ultra-thin flexible chips and device modeling

Heidari

Wacker

Dahiya

2017

Applied Physics Reviews

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“…A majority of the aforementioned applications require devices that are anticipated to bend repeatedly during the device usage, for, e.g., sensors and actuators placed in smart plasters and electronic skin. However, FHE is a relatively younger field of research that is still in its nascent stages of development and hence, information available regarding the static [27][28][29][30][31][32] as well as dynamic bending reliability [33][34][35][36] of FHE components is rather very limited. Several studies have shown that the failure of chip-foil packages during repeated bending occur mainly because of the cracking of interconnects rather than the delamination of the chip from foil or chip fracture [34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Influence of Flexibility of the Interconnects on the Dynamic Bending Reliability of Flexible Hybrid Electronics

et al. 2020

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The growing interest towards thinner and conformable electronic systems has attracted significant attention towards flexible hybrid electronics (FHE). Thin chip-foil packages fabricated by integrating ultra-thin monocrystalline silicon integrated circuits (ICs) on/in flexible foils have the potential to deliver high performance electrical functionalities at very low power requirements while being mechanically flexible. However, only very limited information is available regarding the fatigue or dynamic bending reliability of such chip-foil packages. This paper reports a series of experiments where the influence of the type of metal constituting the interconnects on the foil substrates on their dynamic bending reliability has been analyzed. The test results show that chip-foil packages with interconnects fabricated from a highly flexible metal like gold endure the repeated bending tests better than chip-foil packages with stiffer interconnects fabricated from copper or aluminum. We conclude that further analysis work in this field will lead to new technical concepts and designs for reliable foil based electronics.

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Ultra‐Thin Chips with Printed Interconnects on Flexible Foils

Kumaresan

Dahiya

et al. 2021

Adv Elect Materials

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“Heterogeneous Integration” is a promising approach for high‐performance hybrid flexible electronics that combine printed electronics and silicon technology. Despite significant progresses made by integrating rigid silicon chips on flexible substrates, the integration of flexible ultra‐thin chips (UTCs) on flexible foils remains a challenge as they are too fragile for conventional bonding methods. Reliable interconnects (low‐resistivity and mechanical robustness) and bonding of UTCs are critical to the realization of hybrid flexible systems. Herein, using a non‐contact printing approach, an easy and cost‐effective method for accessing UTCs on flexible foils is demonstrated. The high‐viscosity conductive paste, extruded from a high‐resolution printer (1–10 µm line width), is used here to connect the metal oxide semiconductor field effect transistors (MOSFETs) on UTCs with the extended pads on flexible printed circuit boards (PCBs). The electrical characterization of MOSFETs, before and after printing the interconnects, reveals an acceptable level of variation in device mobility (change from 780 to 630 cm2 V−1s−1). This is due to the drop in effective drain bias voltage as a marginally small electrical resistance (≈30 Ω) is added by the printed interconnects. The bonded UTCs show robust device performance under bending conditions, indicating high reliability of both the chip thinning and bonding methods.

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Mechanical and electrical properties of ultra-thin chips and flexible electronics assemblies during bending

Cited by 35 publications

References 15 publications

Bending induced electrical response variations in ultra-thin flexible chips and device modeling

Bending induced electrical response variations in ultra-thin flexible chips and device modeling

Influence of Flexibility of the Interconnects on the Dynamic Bending Reliability of Flexible Hybrid Electronics

Ultra‐Thin Chips with Printed Interconnects on Flexible Foils

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