Stacked Semiconductor Die Thermal Transfer Structure
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Solution Overview
Problem
Vertically-stacked semiconductor die packages face challenges in dissipating heat efficiently, leading to increased operating temperatures due to additive heat generation, which limits the maximum operating temperature of the device and is exacerbated by die density and mixed die types.
Innovation Solution
The implementation of a stacked semiconductor die assembly with a thermal transfer structure (TTS) that includes a thermally conductive casing and underfill material to enhance heat dissipation, where the TTS covers a significant percentage of the peripheral region of the first die and encases the stack of second dies, providing efficient thermal paths for heat removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple semiconductor dies are vertically stacked to increase processing power without increasing package footprint, then the functional capacity of the package is improved, but the heat dissipation capability deteriorates due to additive heat generation
Solution Approach 1:
The patent divides the thermal management system into multiple independent thermal paths: (1) a first thermal path through the substrate, (2) a second thermal path through lateral thermal transfer features on the peripheral portion, and (3) a third thermal path through the underfill material. This segmentation allows heat to be dissipated through multiple parallel routes simultaneously, preventing heat accumulation in the stacked die configuration.
Solution Approach 2:
The patent introduces lateral thermal transfer features on the peripheral portion that extend horizontally outward beyond the stacked dies, creating a new lateral dimension for heat dissipation. This complements the traditional vertical thermal path through the substrate, effectively adding another dimension (horizontal vs. vertical) for thermal management in the stacked die package.
2Productivity
If the density of dies in the package is increased to meet operating parameters, then the functional capacity is improved, but the heat dissipation capability deteriorates
Solution Approach 1:
The thermal management system is segmented into multiple independent thermal paths that can simultaneously handle heat from multiple dies. The first thermal path through the substrate, the second thermal path through lateral thermal transfer features, and the third thermal path through underfill material work in parallel, allowing the system to manage heat from high-density die configurations without temperature escalation.
Solution Approach 2:
The underfill material acts as an intermediary thermal conduction medium between the stacked dies and the substrate. It fills the gaps and provides a thermal bridge that facilitates heat transfer from the die interfaces to the substrate, enabling efficient heat dissipation in high-density configurations where direct thermal contact is limited.
3Adaptability or versatility
If different types of dies are stacked in the package to increase functional capacity, then the versatility is improved, but the maximum operating temperature is limited by the die with the lowest maximum operating temperature
Solution Approach 1:
The patent implements multiple independent thermal paths that can be selectively utilized based on the thermal requirements of different die types in the stack. Each thermal path (through substrate, through lateral features, through underfill) provides an independent route for heat removal, allowing the system to manage the thermal constraints of mixed die types more effectively than a single thermal path would allow.
4Temperature
If a thermal transfer structure is added to provide additional thermal paths for heat dissipation, then the heat dissipation capability is improved, but the device complexity increases
Solution Approach 1:
The substrate serves multiple functions: it provides mechanical support for the stacked dies, electrical interconnection through TSVs, and thermal conduction through the first thermal path. The underfill material simultaneously provides mechanical bonding between dies and substrate, gap filling, and thermal conduction through the third thermal path. This multi-functionality reduces the need for separate dedicated thermal management components, thereby limiting the increase in device complexity.
Solution Approach 2:
The underfill material serves as an intermediary that performs multiple roles: mechanical bonding between the stacked dies and substrate, gap filling for structural integrity, and thermal conduction through the third thermal path. By combining these functions in a single material layer, the patent avoids the complexity that would arise from adding separate dedicated components for each function.
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 configuration effectively lowers the operating temperatures of individual dies, ensuring they remain below their maximum temperatures, even in hybrid memory cube configurations with varying power levels, by efficiently transferring heat away from the logic die and memory dies.
Implementation Method 1
The implementation of a stacked semiconductor die assembly with a thermal transfer structure (TTS) that includes a thermally conductive casing and underfill material to enhance heat dissipation
Data Source
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Figure 2B
AI summary
Semiconductor die assemblies having high efficiency thermal paths. In one embodiment, a semiconductor die assembly comprises a package support substrate, a first semiconductor die electrically mounted to the package support substrate, and a plurality of second semiconductor dies. The first die has a stacking site and a peripheral region extending laterally from the stacking site, and the bottom second semiconductor die is attached to the stacking site of the first die. The assembly further includes (a) a thermal transfer structure attached to the peripheral region of the first die that has a cavity in which the second dies are positioned and an inlet, and (b) an underfill material in the cavity. The underfill material has a fillet between the second semiconductor dies caused by injecting the underfill material into the cavity through the inlet port of the casing.