Composite Thermal Interface Material for Hot Spot Cooling
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Solution Overview
Problem
High-performance IC packages face challenges in efficiently dissipating heat due to the formation of hot spots, leading to reduced performance and reliability, as existing thermal interface materials (TIMs) are insufficient in managing the increased heat dissipation requirements of modern electronic assemblies.
Innovation Solution
A composite thermal interface material (TIM) is used, comprising a more thermally conductive material over hot spots and a less thermally conductive material surrounding it, which can be preformed as a single unit or multiple units, typically consisting of solder and polymer, to effectively dissipate heat from the IC die to the heat spreader.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single uniform TIM is used between die and heat spreader, then the manufacturing process is simple, but the thermal resistance is high and hot spots cannot be effectively cooled
Solution Approach 1:
The patent applies local quality by using different TIM materials with different thermal conductivities in different regions of the die. Specifically, a first TIM material with higher thermal conductivity is applied to regions with hot spots, while a second TIM material with lower thermal conductivity is applied to regions without hot spots. This localized differentiation optimizes heat dissipation where needed while maintaining overall thermal management effectiveness.
Solution Approach 2:
The patent employs composite materials by combining two different TIM materials (first TIM material and second TIM material) with different thermal conductivities in a single TIM layer. This composite approach allows the system to achieve both high thermal conductivity in critical hot spot regions and adequate thermal management in non-critical regions, resolving the contradiction between uniform simplicity and localized performance.
2Temperature
If a thinner bond line thickness is used to reduce thermal resistance, then thermal performance improves, but the risk of material cracking and reliability issues increases
Solution Approach 1:
The patent applies local quality by selecting different TIM materials with appropriate thicknesses for different regions. In hot spot regions, a thinner bond line with higher thermal conductivity material is used to minimize thermal resistance. In non-hot-spot regions, a thicker bond line with lower thermal conductivity material is used, which reduces stress concentration and cracking risk. This regional differentiation resolves the contradiction between thinning for thermal performance and maintaining reliability.
3Speed
If higher operational frequencies are used to improve performance, then clock frequency increases, but heat dissipation requirements increase leading to hot spots
Solution Approach 1:
The patent addresses the heat dissipation challenge from high-frequency operation by applying local quality through region-specific TIM materials. Hot spot regions, which generate the most heat during high-frequency operation, receive TIM material with higher thermal conductivity to efficiently conduct heat away. Non-hot-spot regions use TIM material with lower thermal conductivity, maintaining adequate thermal management without unnecessarily increasing overall heat dissipation requirements. This allows the system to operate at higher frequencies while managing localized thermal loads effectively.
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 solution reduces thermal resistance by up to 15% and improves reliability by allowing a thinner bond line thickness, effectively managing hot spots and reducing the risk of material cracking, thereby enhancing the performance and longevity of electronic assemblies.
Implementation Method 1
A more thermally conductive material may be positioned over one or more die hot spots... effectively dissipate heat from the IC die to the heat spreader
Data Source
AI summary
A composite of two or more thermal interface materials (“TIMs”) is placed between a die and a heat spreader to improve cooling of the die in an integrated circuit package. The two or more TIMs vary in heat-dissipation capability depending upon the locations of die hot spots. In an embodiment, a more thermally conductive material may be positioned over one or more die hot spots, and a less thermally conductive material may be positioned abutting and/or surrounding the more thermally conductive material. The two or more TIMs may comprise a solder and a polymer. The composite TIM may be preformed as one unit or as a plurality of units. Methods of fabrication, as well as application of the package to an electronic assembly and to an electronic system, are also described.