Thermomechanical Degradation of Thermal Interface Materials: Accelerated Test Development and Reliability Analysis

Abstract

Due to the inherently low adhesive strength and structural integrity of polymer thermal interface materials (TIMs), they present a likely point of failure when succumbed to thermomechanical stresses in electronics packaging. Herein, we present a methodology to quantify TIM degradation through an accelerated and repeatable mechanical cycling technique. The testing apparatus incorporated a steady-state thermal conductivity measurement system, consistent with ASTM 5470-06, with added displacement actuation and force sensing to provide controlled cyclic loading between −20 N and 20 N. Additionally, a novel optical technique was utilized to observe void formation, pump-out, and dry-out behavior during cycling, in order to correlate the thermal performance with physical behaviors of different TIMs under cyclic stress. Of the two different pastes analyzed, cyclic testing was found to degrade the thermal performance of the less viscous TIM by increasing its interfacial resistance. Optical qualitative measurements revealed the breakdown of the TIM structure at the interface, which indicated the formation of voids due to TIM degradation. Applying this testing method for future TIM development could help in optimizing TIM structure for particular package applications.

Vertically Aligned Boron Nitride Nanosheets Films for Superior Electronic Cooling

“…Meanwhile, the temperature-driven breakdown of polymer cross-linking results in cracks inside TIM. TIM dry-out and cracks deteriorate heat transfer performance and may lead to severe equipment failure. , Thus, it is necessary to verify the high temperature reliability of the VBNF/PDMS TIMs. A temperature cycling test based on a modified ASTM-D5470 test method has been carried out to determine TIM’s reliability (Figure S11).…”

Scalable microfluidic fabrication of vertically aligned two-dimensional nanosheets for superior thermal management

“…57,58 Another failure mechanism occurs at high temperature when the filler materials are separated from the polymer matrix, which is typically known as TIM ‘dry-out’. 57…”

“…As a device undergoes power cycling throughout typical on/off cycles, the mismatch of the thermal expansion between the device and heat sink induces warpage and thermomechanical stress, causing the TIM to be squeezed out between the device and heat sink, which is intuitively referred to as TIM 'pump-out'. 57,58 Another failure mechanism occurs at high temperature when the filler materials are separated from the polymer matrix, which is typically known as TIM 'dry-out'. 57 To simulate the temperature fluctuations that accompany power cycles in real-world applications, a temperature cycling test was carried out to determine the reliability of the TIM.…”

“…57,58 Another failure mechanism occurs at high temperature when the filler materials are separated from the polymer matrix, which is typically known as TIM 'dry-out'. 57 To simulate the temperature fluctuations that accompany power cycles in real-world applications, a temperature cycling test was carried out to determine the reliability of the TIM. As seen in the setup based on a modified ASTM D5470 method (Fig.…”

Factoring Interacting Stress Mechanisms in Design for Reliability of Extreme Environment Power Modules

“…Prior works have demonstrated that the development of novel accelerated testing methods for addressing specific failure mechanisms can decrease testing times while still delivering lifetime prediction accuracy [13][14][15][16]. Therefore, well-designed accelerated testing processes and results can be leveraged for reliability estimation.…”