Thermally Conductive Sheet via Volatile Liquid Evaporation
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Solution Overview
Problem
The increasing heat generation in miniaturized electronic appliances requires thermally conductive sheets with higher thermal conductivity to efficiently dissipate heat, which existing methods fail to achieve effectively.
Innovation Solution
A method for producing a thermally conductive sheet involving a reactive liquid resin, a volatile liquid with a boiling point higher than the curing temperature, and thermally conductive fillers like carbon fibers, where the resin is crosslinked and cured before evaporating the volatile liquid, promoting filler contact and orientation, and the sheet is sliced to increase surface area for rapid evaporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If carbon fibers are loaded and oriented in thermally conductive sheets, then thermal conductivity is improved, but the amount of heat generated by electronic appliances continues to increase requiring higher thermal conductivity
Solution Approach 1:
The patent uses a composite material system consisting of carbon fibers (graphitic carbon) dispersed in a silicone rubber matrix. The carbon fibers provide high thermal conductivity pathways while the silicone rubber provides mechanical flexibility and thermal stability. This composite structure enables the sheet to achieve high thermal conductivity (λ≥3.0 W/m·K) to handle increasing heat generation from miniaturized electronic appliances.
2Temperature
If a volatile liquid is added to the thermally conductive composition, then filler contact is promoted and thermal conductivity is enhanced, but foaming may occur during heating
Solution Approach 1:
The patent carefully controls the boiling point parameter of the volatile liquid to be higher than the curing temperature of the silicone rubber. This parameter selection ensures that the volatile liquid remains in liquid form during the curing process, preventing foaming, while still being able to evaporate after curing to create voids that promote filler contact and enhance thermal conductivity.
Solution Approach 2:
The volatile liquid is added to the thermally conductive composition before the curing process. During curing, the volatile liquid remains trapped in the matrix, and its presence influences the packing and contact of thermally conductive fillers. After curing is complete, the volatile liquid is then evaporated, creating voids that improve filler contact pathways.
3Temperature
If the reactive liquid resin is crosslinked and cured before evaporating the volatile liquid, then filler contact is promoted, but the process complexity increases
Solution Approach 1:
The patent implements a continuous two-stage heating process where the first stage cures the silicone rubber at a temperature below the volatile liquid's boiling point, and the second stage evaporates the volatile liquid at a higher temperature. This continuous process, without intermediate interruptions or separate operations, efficiently achieves both curing and volatile liquid removal while promoting filler contact, thereby managing process complexity.
4Productivity
If the sheet is sliced to increase surface area, then evaporation of volatile liquid is accelerated, but manufacturing complexity increases
Solution Approach 1:
The patent divides the molded body into multiple thinner sheets through slicing. This segmentation increases the total surface area of the sheets, which accelerates the evaporation of the volatile liquid in the subsequent heating process. The slicing operation is a simple mechanical process that can be easily integrated into existing manufacturing lines, thereby improving productivity without significantly increasing manufacturing complexity.
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 method results in a thermally conductive sheet with enhanced thermal conductivity, as evidenced by a weight increase of 0.1 to 1% in isopropyl alcohol immersion, and improved thermal conductivity compared to traditional sheets, while preventing foaming and maintaining flexibility.
Implementation Method 1
a step of obtaining a thermally conductive composition by mixing a reactive liquid resin, which forms a rubbery or gelatinous matrix when crosslinked
Implementation Method 2
a step of forming a molded body by crosslinking and curing the reactive liquid resin at a temperature 10° C. or more lower than the boiling point of the volatile liquid
Implementation Method 3
a step of evaporating the volatile liquid by heating the molded body
Implementation Method 4
contraction caused by evaporation of the volatile liquid promotes the contact between the thermally conductive fillers
Implementation Method 5
thermally conductive sheets are sometimes placed between the heat-generating elements and the heat-dissipating elements to enhance the efficiency of transferring heat
Data Source
AI summary
A method for producing a thermally conductive sheet S includes a step of obtaining a thermally conductive composition by mixing a reactive liquid resin, which forms a rubbery or gelatinous matrix when crosslinked, a volatile liquid having a boiling point 10° C. or more higher than a curing temperature of the reactive liquid resin, and a thermally conductive filler; a step of forming a molded body by crosslinking and curing the reactive liquid resin at a temperature 10° C. or more lower than the boiling point of the volatile liquid; and a step of evaporating the volatile liquid by heating the molded body, in which these steps are performed sequentially.