Thermo-mechanical analysis of flexible and stretchable systems

Abstract

This paper presents a summary of the modeling and technology developed for flexible and stretchable electronics. The integration of ultra thin dies at package level, with thickness in the range of 20 to 30 µm, into flexible and/or stretchable materials are demonstrated as well as the design and reliability test of stretchable metal interconnections at board level are analyzed by both experiments and finite element modeling. These technologies can achieve mechanically bendable and stretchable subsystems.The base substrate used for the fabrication of flexible circuits is a uniform polyimide layer, while silicones materials are preferred for the stretchable circuits. The method developed for chip embedding and interconnections is named Ultra Thin Chip Package (UTCP). Extensions of this technology can be achieved by stacking and embedding thin dies in polyimide, providing large benefits in electrical performance and still allowing some mechanical flexibility. These flexible circuits can be converted into stretchable circuits by replacing the relatively rigid polyimide by a soft and elastic silicone material. We have shown through finite element modeling and experimental validation that an appropriate thermo mechanical design is necessary to achieve mechanically reliable circuits and thermally optimized packages.

Influence of the Thermomechanical Characteristics of Low-Density Polyethylene Substrates on the Thermoresistive Properties of Graphite Nanoplatelet Coatings

“…It is known that the thermomechanical stability of the substrate is an important technological issue in the application of microelectronics, micro-electromechanical systems, and flexible electronics [28,29]. Therefore, to establish the proper operating temperature ranges of the samples, extensive characterizations of the LDPE were carried out by means of differential scanning calorimetry and dynamic-mechanical-thermal analysis over wide temperature ranges.…”

Multi-layer embedded carbon fibres as highly compliant and stretchable interconnects

“…However, some authors have pointed out how silicon, and other conductors traditionally used in microfabrication, might not be the most suitable for the realisation of stretchable interconnects due to their inherent brittleness [5]. Other possible approaches, based on planar thin-film technologies, consist in patterning metal lines in coplanar horseshoe-shaped meanders [6][7][8] or exploiting the spontaneous out of plane buckling of metal films deposited on an elastomeric substrate [9][10][11][12][13][14]. For these devices, the maximum elongation at break is limited by the ultimate strain of the metal tracks and by the plastic strains induced locally in the metal conductor by the deformation of its spring shaped structure [6,15].…”

Variation of Elastic Stiffness of Polydimethylsiloxane (PDMS) Stretchable Substrates for Wearable Packaging Applications

“…polydimethylsiloxane(PDMS)이 사용되고 있다 3,[14][15][16]. PDMS 는 backbone이 Si-O 결합으로 이루어져 있는데, Si-O 결합 에너지는 -622 kJ/mole로 일반적인 고분자의 C-C backbone 결합에너지인 -100 kJ/mole에 비해 매우 낮기 때문에 일 반 고분자에 비해 열과 화학반응에 대해 안정적인 특성 을 나타낸다.…”