Graphite Sheet With Concave Portions For Heat Transfer

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Solution Overview

Problem

Conventional heat radiation sheets with pyrolytic graphite suffer from reduced thermal conductivity due to the inability to effectively contain thermal conductive fillers within their concavities, leading to increased thermal resistance when pressurized.

Innovation Solution

A graphite sheet with anisotropic thermal conductivity featuring first and second concave portions and a connecting hole, filled with a fluid heat radiating member, which enhances heat transfer by preventing filler leakage and improving contact thermal resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a pyrolytic graphite sheet is used as a heat radiation sheet, then flexibility and high thermal conductivity are achieved, but the concavity and convexity on the surface are not large enough to contain thermal conductive fillers, causing them to move and be pushed out during pressurization

Engineering Contradiction:

Improvethermal conductivityVSAvoidsurface structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The graphite sheet is designed with concave portions that create porous spaces capable of containing thermal conductive fillers. These concave portions have sufficient depth and volume to prevent filler movement during pressurization, while maintaining the flexibility and high thermal conductivity characteristics of pyrolytic graphite.

Inventive Principle:

Principle #31Porous materials

2Reliability

If thermal conductive filler is added to fluid heat radiating member to enhance thermal conductivity, then heat transfer performance is improved, but the filler leaks from the surface of the graphite sheet when pressurized, increasing thermal resistance

Engineering Contradiction:

Improvethermal conductivityVSAvoidfiller leakage

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The problematic thermal conductive fillers are extracted from the fluid heat radiating member and relocated into the concave portions of the graphite sheet. This separation prevents filler leakage during pressurization while maintaining enhanced thermal conductivity, as the fillers are contained within the structured concave spaces rather than being part of the fluid that can leak.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The thermal conductive fillers are nested within the concave portions of the graphite sheet structure. This nesting arrangement allows the fillers to be contained securely within the graphite sheet's inherent geometry, preventing leakage while maintaining thermal contact with both the heat generator and heat radiator surfaces.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Strength

If the graphite sheet is pressurized to improve contact between surfaces, then adhesion is enhanced, but thermal conductive fillers are pushed out to the outer periphery, increasing thermal resistance

Engineering Contradiction:

Improvecontact adhesionVSAvoidthermal resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The concave portions are pre-formed in the graphite sheet before pressurization occurs. This preliminary structural preparation creates designated spaces that capture and retain thermal conductive fillers during the subsequent pressurization process, preventing filler ejection to the outer periphery while still achieving strong contact adhesion between surfaces.

Inventive Principle:

Principle #10Preliminary action

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

The graphite sheet effectively maintains the fluid heat radiating member and enhances heat radiation performance by reducing thermal resistance and preventing filler leakage, thereby improving the thermal connection between heat generators and radiators.

Implementation Method 1

a graphite sheet which has a large anisotropic thermal conductivity in a main surface direction

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a heat radiating member of fluid resin such as silicone grease and silicone oil is applied to the surface of pyrolytic graphite sheet 44. Thus, the heat radiating member enters the concavity and convexity on the surfaces

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS8720537B2Graphite sheet and heat transfer structure using same

Publication Date: 2014.05.13 PANASONIC HOLDINGS CORP

AI summary

A graphite sheet preventing leakage of a heat radiating member when a fluid heat radiating member such as grease is used and improving heat radiation performance is provided. A graphite sheet includes a first main surface and a second main surface opposite to the first main surface and has a large anisotropic thermal conductivity in a main surface direction. The graphite sheet includes a first concave portion provided on the first main surface and having a first bottom surface, a second concave portion provided on the second main surface and having a second bottom surface, a thin film portion formed in a region in which the first bottom surface and the second bottom surface are overlapped with each other, and a connecting hole penetrating the thin film portion and allowing the first concave portion and the second concave portion to communicate with each other.