Search

Thermal interface materials (TIMs) used between the chip and the heat spreader play an indispensable role in effective heat removal to ensure the chip's performance and reliability. As they suffer from stresses in practical applications, TIMs need to have high toughness to resist fracture. The notch sensitivity of TIMs is considered an important parameter to evaluate its toughness. However, the notch sensitivity of TIMs is seldom mentioned, and the mechanism to enhance the toughness is still unclear. Here, using polymer-based TIMs consisting of polydimethylsiloxane/aluminum as a model, we specifically investigate notch sensitivity of TIMs and analyze the mechanical mechanism in detail from the macroscopic and microscopic scales. It was found that a transition from notch insensitive to notch sensitive will happen with a notch length of 2.0 mm, which is much higher than typical soft materials, such as hydrogels. We interpret the notch sensitivity of the TIM by finite element analysis at macroscopic scales and the Lake–Thomas theory at microcosmic scales. The relationship between the area of the strain concentration region to the notch length in finite element analysis is in good agreement with the fracture stretch ratio with different notch lengths measured in a uniaxial tensile experiment. This investigation gives an insight into designing notch-insensitivity TIM and understanding their fracture behavior. [ABSTRACT FROM AUTHOR]

Soft gels with high toughness have drawn tremendous attention recently due to their potential applications in flexible electronic fields. The miniaturization and high‐power density of electronic devices require soft gels with both high toughness and low thermal resistance; however, it is difficult to achieve these properties simultaneously. Herein, a simple design strategy is reported for constructing soft (high stretchability of 6.91 and low Young's modulus of 340 kPa), tough (4741.48 J m−2) and thermal conductive (low thermal resistance of 0.14 cm2 K W−1, under 10 psi pressure) polydimethylsiloxane/aluminum composite gel. This is realized by precisely lengthening polymer strands between the chemical cross‐linked points and controlling the aluminum content in the composite gels. The symbiosis of this combination involves: lengthening the polymer strands facilitates its unfolding to increase the softness and intrinsic toughness; the thermally conductive spherical aluminum enables low thermal resistance and increases the intrinsic toughness and stress dissipation. By utilizing this gel as a thermal interface material, effective heat dissipation is demonstrated in electronic devices operating under high‐power conditions over numerous cycles. These results demonstrate the application potential of composite gels in meeting the performance maintenance and heat dissipation, which are needed for modern electronic devices. [ABSTRACT FROM AUTHOR]

The emerging applications of thermally conductive elastomer composites in modern electronic devices for heat dissipation require them to maintain both high toughness and resilience under thermomechanical stresses. However, such a combination of thermal conductivity and desired mechanical characteristics is extremely challenging to achieve in elastomer composites. Here this long-standing mismatch is resolved via regulating interfacial structure and dynamics response. This regulation is realized both by tuning the molecular weight of the dangling chains in the polymer networks and by silane grafting of the fillers, thereby creating a broad dynamic-gradient interfacial region comprising of entanglements. These entanglements can provide the slipping topological constraint that allows for tension equalization between and along the chains, while also tightening into rigid knots to prevent chain disentanglement upon stretching. Combined with ultrahigh loading of aluminum-fillers (90 wt%), this design provides a low Young's modulus (350.0 kPa), high fracture toughness (831.5 J m -2 ), excellent resilience (79%) and enhanced thermal conductivity (3.20 W m -1 k -1 ). This work presents a generalizable preparation strategy toward engineering soft, tough, and resilient high-filled elastomer composites, suitable for complex environments, such as automotive electronics, and wearable devices., (© 2024 Wiley‐VCH GmbH.)