Isotropic Housing Material for Wearable Device Thermal Management
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Solution Overview
Problem
Wearable devices with integrated components face challenges in managing heat dissipation and maintaining component positioning and orientation due to anisotropic thermal expansion and conductivity properties of materials, leading to potential damage and premature failure.
Innovation Solution
Using a housing material with a substantially isotropic coefficient of thermal expansion and thermal conductivity, and integrating components as a cluster with embedded conductive traces to reduce the number of structural elements and improve heat dissipation, while maintaining component positioning and orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If components are packed tightly together within the device, then device functionality is improved, but heat dissipation becomes more difficult and temperature control worsens
Solution Approach 1:
A thermal pad is introduced as an intermediary component between the electronic component and the housing. This thermal pad serves as a heat transfer medium that conducts heat away from the component while accommodating thermal expansion differences between materials with different coefficients of thermal expansion, thereby enabling tight component packing without compromising heat dissipation.
Solution Approach 2:
The patent utilizes materials with different coefficients of thermal expansion (CTE) for the housing and component substrate. By carefully selecting materials with matched CTE values, the thermal pad compensates for dimensional changes during thermal cycling, maintaining stable electrical connections and preventing stress-induced failures while allowing compact device design.
2Strength
If housing material is selected for durability and shock resistance, then structural strength is improved, but thermal conductivity may be reduced leading to poor heat dissipation
Solution Approach 1:
The thermal pad acts as a mediator between the structurally strong but thermally insulating housing and the heat-generating electronic component. It provides a dedicated thermal conduction path that does not compromise the structural integrity of the housing, allowing the housing to maintain its durability while the thermal pad handles heat dissipation.
Solution Approach 2:
Instead of requiring the entire housing to be thermally conductive (which would compromise structural strength), the thermal solution is localized to the specific area where heat dissipation is needed. The thermal pad provides high thermal conductivity only at the component mounting interface, while the housing maintains its structurally optimized properties elsewhere.
3Stability of the object's composition
If different materials are used for housing and component substrate due to CTE differences, then component stability is improved, but the number of structural elements increases and manufacturing complexity worsens
Solution Approach 1:
The thermal pad serves multiple functions simultaneously: it provides thermal conduction, accommodates CTE differences between materials, and acts as a mounting interface. By merging these functions into a single component rather than requiring separate elements for each function, the patent reduces overall device complexity while maintaining component stability.
Solution Approach 2:
The patent addresses CTE mismatches by selecting materials with compatible thermal expansion coefficients and using the thermal pad's viscoelastic properties to accommodate dimensional changes. This approach maintains component stability through material parameter optimization rather than requiring complex mechanical compensation structures.
4Ease of manufacture
If individual components are mounted separately to the housing, then manufacturing flexibility is improved, but position and orientation accuracy deteriorates over time due to thermal expansion differences
Solution Approach 1:
Multiple electronic components are mounted on a single component substrate that is then mounted as one unit to the housing via the thermal pad. This merging of components onto a common substrate maintains their relative positions and orientations accurately while still allowing flexible manufacturing, as the entire substrate assembly can be installed as one component.
Solution Approach 2:
The thermal pad serves as a stable intermediary mounting interface that provides consistent mechanical support and electrical isolation. By mounting the substrate to the housing through this stable thermal pad interface rather than direct mechanical attachment, the system maintains position and orientation accuracy over thermal cycling while preserving manufacturing flexibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the durability and stability of wearable devices by minimizing thermal stress, reducing hotspots, and extending the lifespan of components by ensuring consistent heat dissipation and maintaining precise component alignment.
Implementation Method 1
Materials used for the housing bodies of devices exhibit a particular coefficient of thermal expansion (CTE) indicating how the material physically expands under increasing temperature. In the scenarios presented herein, devices are occasionally manufactured with materials that exhibit different coefficients of thermal expansion in different dimensions... Differences in CTE may cause the position and/or orientation of components integrated with the surface of the device to shift over time
Implementation Method 2
Many materials exhibit differences in thermal conductivity along different dimensions, such as greater thermal conductivity orthogonal to the surface of the material than within the plane of the material. These differences may reduce heat dissipation and/or create hot-spots within the device surface... aluminum exhibits a substantially similar CTE both in-plane and out-of-plane, as well as substantially similar thermal conductivity in the in-plane and out-of-plane dimensions
Data Source
AI summary
Devices with components mounted to a surface interior often encounter problems with generated heat, which is difficult to dissipate from a tightly packed and sealed device interior. Excessive heat may also distort the surface substrate material, which may become brittle from accumulated thermal stress and/or warp in a manner that displaces the position and/or orientation of the components. Presented herein are device manufacturing techniques in view of temperature considerations. Devices may comprise a device housing of a housing material that exhibits a substantially isotropic coefficient of thermal expansion (CTE) and/or thermal conductivity in various dimensions. Devices may also comprise a housing mount for a component cluster that is mountable on the interior surface of the device housing, with electrically conductive traces integrated with the device housing that conductively interconnect the housing mount with the component cluster, optionally generated via laser-activation of a conductive additives or deposition of conductive material.