Filled Elastomer Thermal Interface for Electronic Assemblies
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Solution Overview
Problem
Current thermal interface adhesives for electronic assemblies are rigid, lack rework capability, and have poor thermal conductivity due to the absence of thermally conductive fillers in thermoplastic films, failing to accommodate materials with mismatched coefficients of thermal expansion and allowing excessive flow during curing.
Innovation Solution
A flexible, fully cured elastomer coated with a partially cured filled adhesive, formed through tape-casting from a solvent-borne slurry, which allows for controlled flow and adhesion, accommodating thermal and electrical conductivity, and enabling rework by varying elastomer and adhesive combinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a thermoplastic film is used as the base material, then the adhesive system is easy to handle and apply, but the thermal conductivity is poor because the thermoplastic does not include a thermally conductive filler
Solution Approach 1:
The patent uses a composite structure consisting of a thermoplastic film base material combined with a thermally conductive adhesive layer containing fillers such as aluminum oxide, silver, or diamond particles. This composite approach allows the system to benefit from both the ease of handling provided by the thermoplastic film and the high thermal conductivity provided by the filled adhesive layer, thereby resolving the contradiction between ease of operation and thermal conductivity performance.
2Strength
If the adhesive is fully cured to achieve good adhesion and heat transfer, then the bond strength is high, but the material becomes rigid and cannot accommodate materials with mismatched coefficients of thermal expansion
Solution Approach 1:
The patent creates different zones with different properties within the adhesive system. The thermoplastic film base provides a compliant, flexible substrate that can accommodate CTE mismatches, while the cured adhesive layer provides strong bonding and heat transfer. This local differentiation of properties allows the system to simultaneously achieve both compliance and strong adhesion, resolving the contradiction between bond strength and adaptability.
3Manufacturing precision
If the adhesive is applied in a low viscosity state during heating, then it can flow to cover the bonding area, but excessive flow into undesired areas and separation of conductive filler from resin phase occurs
Solution Approach 1:
The patent applies the adhesive in a controlled, partially cured state before final heating. This preliminary application allows the adhesive to be positioned accurately on the bonding area while maintaining enough viscosity to prevent excessive flow. The partial curing stabilizes the conductive filler within the resin phase before the final cure cycle, preventing filler separation while still allowing adequate coverage, thus resolving the contradiction between coverage uniformity and preventing harmful flow effects.
4Stability of the object's composition
If a rigid cured adhesive is used to ensure structural stability, then the bond strength is high, but rework capability is lost and the system cannot accommodate thermal expansion differences
Solution Approach 1:
The patent creates a dynamic adhesive system where the thermoplastic film base remains flexible and reversible, while the adhesive layer can be cured to different degrees depending on the application requirements. The thermoplastic component can be reheated and reformed, enabling rework capability, while the adhesive provides structural stability when cured. This dynamic combination allows the system to transition between rigid and flexible states, resolving the contradiction between structural stability and rework capability.
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 flexible adhesion, effective heat transfer, and rework capability while accommodating thermal expansion mismatches, with controlled flow and cost-effective large-area fabrication, maintaining performance across a wide temperature range.
Implementation Method 1
tape-casting is accomplished from a solvent-borne slurry
Implementation Method 2
Their main function is to bond the components together, and allow good heat transfer between the parts that are bonded
Data Source
AI summary
Thermal interface materials are essential for proper operation of electronic assemblies. They are used between surface mount components and printed wiring boards and between printed wiring boards and metal heat sinks. Their function is to bond the components together and allow good heat transfer between the parts being bonded. The approach disclosed in this invention is a fully-cured, flexible, filled elastomer that is coated on both sides with a partially cured, filled adhesive, which can be conveniently made by a low cost tape casting process. This unique approach offers a combination of good adhesion to both bonding surfaces, good heat transfer, compliance to accommodate mismatched coefficient of thermal expansion, rework capability, control of flow of the adhesive during cure, and easy handling of uncured material.