Densified Polyimide Foam Thermal Insulation for Mobile Electronics

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Solution Overview

Problem

Current heat spreaders in electronic devices are inadequate in effectively managing heat distribution and shielding sensitive components from hot spots, as they fail to provide sufficient thermal insulation and mechanical protection, especially in small form factor devices where traditional cooling methods are impractical.

Innovation Solution

Combining a densified polyimide-based foam layer with a traditional thin film heat spreader to enhance in-plane thermal conductivity, providing improved thermal insulation and mechanical shock resistance, while preventing through-plane heat flow and offering electrical insulation for safe integration between electronic components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional thin film heat spreader is used, then the device footprint is covered and heat is conducted across the surface, but the heat spreader fails to provide sufficient thermal insulation and mechanical protection

Engineering Contradiction:

Improvethermal insulation performanceVSAvoidheat spreader structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines polyimide foam material with a thin film heat spreader to create a composite structure. The polyimide foam provides thermal insulation and mechanical protection, while the thin film heat spreader conducts heat across its surface. This composite approach resolves the contradiction by integrating multiple functions (insulation, protection, and heat conduction) into a single multi-layer structure, improving reliability without proportionally increasing device complexity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent merges the heat spreader function with thermal insulation and mechanical protection functions by bonding a polyimide foam layer to the heat spreader. This combining of previously separate components (insulation layer and heat spreader) into a single integrated assembly improves overall thermal management performance while reducing the number of separate parts needed in the device.

Inventive Principle:

Principle #5Merging (Combining)

2Temperature

If the polyimide foam layer is added to block through-plane heat flow, then in-plane thermal conductivity is improved, but the device thickness increases

Engineering Contradiction:

Improvein-plane thermal conductivityVSAvoiddevice thickness

Core Design Contradiction:

TemperatureVSLength of stationary object

Solution Approach 1:

The patent applies local quality by using densified polyimide foam with specific density and thermal resistance properties tailored for the insulation function. The foam is densified to achieve optimal balance between thermal insulation performance and thickness, allowing effective heat blocking without excessive device thickness increase.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If traditional convection cooling is used, then heat is removed from the device, but it is not practical for small form factor or sealed devices

Engineering Contradiction:

Improvecooling method applicabilityVSAvoidheat management effectiveness

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The patent replaces mechanical convection cooling systems with a passive thermal management approach using polyimide foam insulation combined with heat spreader conduction. This substitution eliminates the need for moving parts, fans, or complex cooling mechanisms, making the solution adaptable to small form factor and sealed devices where traditional convection cooling is impractical.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 combination significantly enhances heat shielding and spreading performance, effectively reducing temperatures in sensitive components by up to 8.5°C compared to traditional heat spreaders, while maintaining electrical safety and mechanical robustness, suitable for compact electronic devices.

Implementation Method 1

utilizing the excellent thermal resistance of the polyimide foam material to block the through-plane heat flow

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 2

conducts (spreads) it across its surface area, reducing 'hot spots'

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

Combining the polyimide layer with the heat spreader also provides electrical insulation

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS10842046B2Densified foam for thermal insulation in electronic devices

Publication Date: 2020.11.17 A B BOYD CO

AI summary

A heat spreading and insulating material using densified foam is provided that has a heat spreading layer that is adhered to an insulating layer. The material is designed to be used with mobile devices that generate heat adjacent to heat sensitive components. The insulating layer is formed from a compressed layer of polyimide foam to increase its density. The polyimide foam retains a significant amount of insulating properties through the densification process. In some embodiments, an EMI shielding layer is added to improve electrical properties of the device. The heat spreading layer may be a graphite material with heat conducting properties that preferentially conduct heat in-plane but can also be metal foil or other isotropic heat conducting material. The material may also include pressure sensitive layers to permanently apply the material to the mobile device.