Date of Award

5-5-2025

Degree Type

Capstone Project

First Advisor

Bahram Nassersharif

Abstract

Electronic systems within underwater unmanned vehicles (UUVs) face significant thermal management challenges due to their sealed, convection-limited environments. This reliance solely on conduction for heat dissipation necessitates highly efficient thermal interface materials (TIMs) to transfer heat effectively from densely populated circuit card assemblies (CCAs) to precision-machined heat sink rings. Conventional silicone-based TIMs, despite their widespread use, pose contamination risks during electronics assembly, leading to potential reliability issues. Consequently, Raytheon Technologies has identified a critical requirement for a non-silicone-based TIM that not only ensures high thermal conductivity but also maintains low thermal resistance and superior surface wetting capabilities.

This capstone project aimed to select and validate a silicone-free TIM specifically suitable for UUV applications, ensuring compatibility with stringent thermal, mechanical, and environmental specifications set by Raytheon. Through extensive patent and literature searches, coupled with a competitive evaluation of available TIMs, the project identified candidate materials across various categories, including phase-change materials, thermally conductive gels, greases, and gap pads.

A comprehensive testing regimen was developed, employing a custom-designed test rig featuring a high-temperature resin surrogate CCA, a CNC-machined aluminum heat sink, and a spray-foam-insulated enclosure. Four selected candidate TIMs underwent rigorous evaluation under controlled thermal conditions to quantify their thermal conductivity and contact resistance. These materials were assessed against criteria such as thermal performance, compatibility with additive modeling techniques, ease of application, and cost-effectiveness.

Results from the testing phase conclusively demonstrated the superiority of LAIRD TPCM 7000, a phase-change material characterized by exceptional thermal conductivity, minimal thermal resistance, and 100% silicone-free composition. This TIM effectively bridged microscopic gaps, significantly reducing localized hotspots and ensuring efficient heat dissipation. Additionally, its environmentally compliant nature aligns with global sustainability standards such as RoHS and REACH, making it an optimal choice for sensitive, high-stakes defense applications.

The final recommendation presented to Raytheon Technologies includes detailed considerations for implementation, addressing aspects such as test repeatability, component integration, and application methods. The study also identified strategic opportunities for the advancement of silicone-free TIM technologies in both military and commercial sectors, highlighting potential risks such as supply chain vulnerabilities and regulatory compliance.

Overall, this report provides a robust framework for the selection and application of non-silicone-based TIMs, significantly advancing thermal management strategies in constrained electronic systems such as those employed in advanced UUVs.

Comments

Team Name: Team 8

Company Sponsor: Raytheon

Sponsor Representative: Steven Berube and Rafael Pastrana

Document Reference: URI-MCE-402-008-2025

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