Flexible Foil Thermal Bridge for Microprocessor Cooling
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Solution Overview
Problem
Microprocessors face heat dissipation challenges due to increasing heat output from smaller contact points, leading to potential damage from thermal cycling-induced stress when constrained by hard attached heat exchangers.
Innovation Solution
A flexible heat transfer device comprising stacked foils, fused at the heat exchanger and die regions but flexible in between, which provides a thermal bridge without mechanically loading the die, allowing natural convection cooling while accommodating thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a hard attached heat exchanger is used to cool the microprocessor die, then heat dissipation is effective, but the die is subjected to mechanical stress during thermal cycling which can cause fracture
Solution Approach 1:
The patent employs a flexible heat transfer device composed of multiple thin foil layers that can bend and deform elastically during thermal cycling. This flexibility allows the heat transfer device to accommodate height changes of the BGA chip carrier without transmitting excessive mechanical stress to the fragile microprocessor die, while still maintaining effective thermal contact for heat dissipation.
Solution Approach 2:
The heat transfer device transitions from a rigid structure to a dynamic, flexible structure that can adapt its shape during operation. The flexible foils allow the system to dynamically adjust to thermal expansion and contraction of the BGA chip carrier, maintaining thermal contact while avoiding die fracture.
2Temperature
If forced convection cooling is used to increase heat dissipation capacity, then cooling effectiveness is improved, but power consumption and system complexity increase due to fan requirements
Solution Approach 1:
The heat exchanger is designed to operate passively using natural convection principles. Hot air rising from the heat exchanger surface creates a natural airflow that continuously removes heat from the microprocessor die without requiring external power sources, fans, or active control systems. The system serves itself by utilizing the natural physical phenomenon of convection.
Solution Approach 2:
The patent replaces the mechanical forced convection system (fans, motors, controllers) with a passive thermal convection system. Instead of using mechanical force to move air for cooling, the system relies on natural buoyancy-driven airflow, eliminating the need for powered mechanical components.
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
Effectively dissipates heat from microprocessors without fracturing the die during thermal cycling, maintaining safe operating temperatures and preventing stress-induced damage.
Implementation Method 1
The heat transfer device is formed of a plurality of stacked foils that are fused at a heat exchanger region abutting the heat exchanger, and are fused at a die region abutting the integrated circuit die, but are flexible between the heat exchanger region and the die region
Implementation Method 2
Microprocessor cooling systems must be made capable of dissipating larger amounts of heat from smaller contact points. A variety of systems exist to provide cooling for microprocessors, including forced convention cooling.
Data Source
AI summary
A cooling system for an integrated circuit die comprises a heat exchanger and a heat transfer device. The heat transfer device is formed of a plurality of stacked foils. The stacked foils are fused at a heat exchanger region abutting the heat exchanger, and are fused at a die region abutting the integrated circuit die, but are flexible between the heat exchanger region and the die region.