Heat Diffusion Sheet Adhesive Layering for Reworkability
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Solution Overview
Problem
Existing heat diffusion sheets face challenges in efficiently transmitting heat while maintaining high thermal conductivity and adhesion reliability, particularly when reworking is required, as they often suffer from cohesive failure and reduced adhesion due to the inclusion of thermally conductive materials in adhesive layers.
Innovation Solution
A heat diffusion sheet comprising a graphite sheet with a composite adhesive film, where the adhesive layers do not contain thermally conductive materials, featuring an acrylic adhesive layer, a polyester film, and a silicone adhesive layer, which are sequentially layered to ensure strong adhesion and reworkability without cohesive failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If a thermally conductive material is added to the adhesive layer to maintain thermal conductivity during reworking, then the reworkability is improved, but the initial adhesion is reduced due to surface roughness
Solution Approach 1:
The adhesive system is segmented into two distinct layers: a first adhesive layer in direct contact with the graphite sheet that prioritizes thermal conductivity and strong initial adhesion, and a second adhesive layer on the outer surface that prioritizes reworkability. This segmentation allows each layer to optimize its function without compromising the other, resolving the contradiction between initial adhesion strength and reworkability.
2Ease of repair
If the adhesive layer is made thick to improve reworkability and peeling, then the reworkability is improved, but the thermal conductivity is reduced
Solution Approach 1:
Different regions of the adhesive structure are assigned different qualities and thicknesses: the first adhesive layer near the heat source is kept thin to maintain thermal conductivity, while the second adhesive layer on the outer surface is made thicker to facilitate reworkability and peeling operations. This local differentiation of quality resolves the contradiction between thermal performance and ease of repair.
3Loss of energy
If a thermally conductive adhesive layer is used to maintain heat diffusion, then the thermal conductivity is improved, but the adhesion reliability is reduced due to cohesive failure
Solution Approach 1:
The adhesive system is divided into two functional layers: the first adhesive layer contains thermally conductive material to ensure heat diffusion and strong bonding to the graphite sheet, while the second adhesive layer is made of non-thermally conductive material that provides reliable adhesion without cohesive failure during peeling. This segmentation resolves the contradiction between thermal conductivity and adhesion reliability.
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 solution provides excellent thermal conductivity in the spreading direction, allows for uniform temperature distribution, and enables the silicone adhesive layer to be peeled without residue, enhancing reworkability and adhesion reliability.
Implementation Method 1
a third embodiment of Patent Literature 2 (paragraph 0048) discloses a technique in which a double-sided tape in which an adhesive layer is formed on both faces of a base material such as a PET film is bonded to a surface of the graphite sheet
Implementation Method 2
an acrylic adhesive layer that has a thickness of 5 μm or more and 15 μm or less and does not contain a thermally conductive material
Implementation Method 3
a silicone adhesive layer that has a thickness of 2 μm or more and 25 μm or less, does not contain a thermally conductive material, and has a peel strength of 0.005 N/cm or more and 1.0 N/cm or less
Data Source
AI summary
A heat diffusion sheet 2 has a configuration in which a composite adhesive film is formed on a surface of a graphite sheet 10 having a thickness of 300 μm or more and 2,000 μm or less. This composite adhesive film has a configuration in which (A) an acrylic adhesive layer that has a thickness of 5 μm or more and 15 μm or less and does not contain a thermally conductive material, (B) a polyester film having a thickness of 20 μm or more and 60 μm or less, and (C) a silicone adhesive layer that has a thickness of 2 μm or more and 25 μm or less, does not contain a thermally conductive material, and has a peel strength of 0.005 N/cm or more and 1.0 N/cm or less are sequentially layered on the graphite sheet 10.