Top-Side Cooling Module With TIM Containment for RF Heat Dissipation
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Solution Overview
Problem
High-power RF devices based on GaN/GaAs technology face challenges in effectively managing device heating and controlling junction temperatures due to limited heat dissipation through laminate substrates, leading to thermal resistance and reduced device lifetime, and thermal interface materials (TIM) displacement during thermal cycling.
Innovation Solution
A microelectronics module design with thermal interface material (TIM) containment, featuring a module substrate, flip-chip dies, heat spreaders, mold compound, TIM barriers, and a heat sink, where TIM barriers or notches prevent TIM displacement, ensuring efficient top-side cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If thermal interface material is used to connect heat sink to device, then heat dissipation efficiency is improved, but TIM may be squeezed out or shift away from interface during thermal cycling
Solution Approach 1:
The patent applies TIM barrier structures (such as raised features, trenches, or molded barriers) around the periphery of the TIM application area before TIM is applied. These pre-formed barriers create containment walls that prevent TIM from being squeezed out or shifting during thermal cycling, while still allowing complete TIM coverage of the heat spreader surface for optimal thermal contact.
Solution Approach 2:
The TIM barrier acts as an intermediary structural element between the TIM and the external environment. It provides a physical boundary that mediates the forces during thermal cycling, preventing TIM displacement while maintaining the TIM's thermal function. The barrier is typically integrated into the heat sink or heat spreader structure.
2Power
If gate spacing of GaN/GaAs devices is decreased, then breakdown voltage and output power are improved, but concentrated heat flux in die bodies increases
Solution Approach 1:
The patent segments the heat dissipation function by introducing heat spreaders that divide and distribute the concentrated heat flux from the die across a larger surface area. Multiple heat spreaders may be used, each serving a specific die or region, to effectively distribute the heat load and reduce peak temperatures.
Solution Approach 2:
The patent transitions from two-dimensional heat dissipation through the substrate to three-dimensional heat management by adding top-side heat spreaders and heat sinks. This creates additional thermal pathways in the vertical dimension, allowing heat to be extracted from both the bottom and top surfaces of the device stack.
3Temperature
If bottom-side cooling through laminate substrate is used, then heat dissipation is provided, but thermal resistance increases and device lifetime is reduced
Solution Approach 1:
The patent inverts the conventional cooling approach by implementing heat sinks and active cooling on the top surface of the device stack rather than relying solely on bottom-side substrate cooling. This top-side cooling strategy provides lower thermal resistance pathways and improves heat extraction efficiency, thereby extending device lifetime.
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 design maintains reliable thermal coupling and extends the lifetime of high-power RF devices by preventing TIM displacement and enhancing heat dissipation through the top-side cooling pathway.
Implementation Method 1
the at least one heat spreader resides over and is thermally coupled to the at least one flip-chip die
Implementation Method 2
The at least one TIM section covers at least the top surface of the at least one heat spreader... The heat sink is in contact with both the at least one TIM section and the at least one TIM barrier
Implementation Method 3
heat dissipation at the top side of the microelectronics module
Implementation Method 4
heat dissipation at the top side of the microelectronics module
Data Source
AI summary
The present disclosure relates to a microelectronics module featuring thermal interface material (TIM) containment for efficient and reliable top-side cooling, and a process for making the same. The microelectronics module includes a module substrate, a flip-chip die attached to the module substrate, and a heat spreader positioned above and thermally coupled to the flip-chip die. A TIM barrier, partially embedded in a mold compound, continuously surrounds the heat spreader and protrudes vertically beyond the heat spreader to define a TIM cavity over the heat spreader. A TIM section fills the TIM cavity to cover the heat spreader. A heat sink is in contact with both the TIM section and the TIM barrier, where the TIM barrier is configured to prevent the TIM section from shifting away from over the heat spreader, thereby maintaining thermal coupling between the heat sink and the heat spreader through the TIM section.