Heterogeneous Thermal Interface Material for Multi-Chip Heat and Strain
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Solution Overview
Problem
Thermal interface materials (TIMs) face challenges such as delamination and pump-out, leading to reduced thermal conductivity and increased operating temperatures in electronic devices with varying mechanical stresses due to differing heat generation among integrated components.
Innovation Solution
A heterogeneous thermal interface material (HTIM) comprising two distinct TIMs with different properties, including a high thermal conductivity metal-based TIM for high-power chips and a polymer-based TIM for low-power chips, to minimize strain, delamination, and warping by optimizing heat transfer and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single TIM is used for all chips, then device complexity is reduced, but thermal management performance deteriorates due to inability to address varying heat generation and mechanical stress requirements
Solution Approach 1:
The TIM is divided into multiple discrete TIM elements, each positioned between specific chips and the heat spreader. High-power chips receive TIMs with higher thermal conductivity, while low-power chips receive TIMs with lower thermal conductivity, allowing optimized thermal management for each chip's specific heat generation characteristics.
Solution Approach 2:
Different TIM elements are assigned different material properties (thermal conductivity, modulus of elasticity) based on the local requirements of each chip. This creates a heterogeneous TIM system where each region has properties optimized for its specific thermal and mechanical needs, rather than using a uniform TIM across all chips.
2Temperature
If high thermal conductivity TIM is used for all chips, then heat transfer from high-power chips is improved, but mechanical stability deteriorates due to reflow and short circuits affecting low-power chips
Solution Approach 1:
The system applies different TIM material properties to different chips based on their power consumption and thermal requirements. High-power chips receive high thermal conductivity TIMs for efficient heat transfer, while low-power chips receive TIMs with properties that prevent reflow and maintain mechanical stability, avoiding the harmful effects of overly aggressive thermal conduction materials.
Solution Approach 2:
The TIM material parameters (thermal conductivity, modulus of elasticity, melting point) are changed and optimized for each specific chip-TIM pairing. This allows the system to achieve high heat transfer efficiency where needed while maintaining mechanical stability and preventing reflow issues in other regions.
3Reliability
If heterogeneous TIMs with different properties are used for different chips, then thermal management and mechanical stability are optimized, but device complexity increases
Solution Approach 1:
The TIM system is segmented into multiple independent TIM elements that can be individually selected and positioned. This segmentation allows the system to achieve optimized thermal and mechanical performance for each chip while maintaining the flexibility to manage complexity through modular design and selective application.
Solution Approach 2:
The heat spreader serves as a universal component that interfaces with multiple different TIM elements and chip types. This multi-functional approach allows a single heat spreader design to work with heterogeneous TIM configurations, reducing overall system complexity despite the diversity of TIM materials used.
4Strength
If TIM with high modulus of elasticity is used, then mechanical stability is improved, but heat transfer capability deteriorates
Solution Approach 1:
The system applies different TIM material properties to different chips based on their specific requirements. Chips that benefit from high mechanical stability receive TIMs with high modulus of elasticity, while chips that prioritize heat transfer receive TIMs with high thermal conductivity. This local optimization resolves the contradiction by allowing both properties to be maximized in their respective applications.
Solution Approach 2:
The system uses different TIM materials with complementary properties for different chips. By selecting appropriate materials for each application, the system achieves both high mechanical stability and high thermal conductivity where needed, rather than being constrained by a single material's inherent trade-offs.
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 HTIM effectively transfers heat from high-power chips to cooling devices while preventing reflow and short circuits, enhancing mechanical stability and minimizing warping and delamination in integrated circuit chip packages.
Implementation Method 1
The first TIM comprises a material having a first thermal conductivity... The HTIM bonds the first and second IC chips to the thermal cooling device
Implementation Method 2
The first TIM reflows when the first TIM reaches a first TIM reflow temperature
Data Source
AI summary
A chip package assembly includes a first high-power chip, a second low-power chip, a thermal cooling device and a heterogeneous thermal interface material (“HTIM”). The thermal cooling device may overlie the first chip and the second chip. The HTIM includes a first thermal interface material (“TIM”) and a second TIM. The first TIM overlies the first chip, and the second TIM overlies the second chip. The first TIM includes a material that has a first thermal conductivity and a first modulus of elasticity. The first TIM can reflow when the first die reaches a first TIM reflow temperature. The second TIM comprises at least a polymer material. The second TIM has a second modulus of elasticity that is greater than the first modulus of elasticity and a second thermal conductivity that is less than the first thermal conductivity.