Solderable Thermal Interface Structures for Warpage-Resistant IC Packages
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Solution Overview
Problem
Warpage in thin integrated circuit (IC) device packages due to differences in temperature coefficients of thermal expansion between device and package materials, leading to thermal performance decline and potential pump-out of thermal interface material (TIM), which affects the compute system's performance and lifetime.
Innovation Solution
Fabrication of solderable thermal interface structures on IC dies and heat spreaders with varying thicknesses to accommodate different IC die thicknesses, using techniques like patterning metal layers and additive deposition to create discrete thermal interconnects, allowing for minimal z-height and reduced thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If thin IC device packages are used, then device size is reduced, but warpage occurs due to CTE differences between materials
Solution Approach 1:
The patent applies local quality by implementing a non-uniform thickness profile for the heat spreader, specifically making the central region thicker than the peripheral regions. This localized thickness variation compensates for the differential thermal expansion between the IC die and package materials, thereby reducing warpage while maintaining thin package overall dimensions.
Solution Approach 2:
The patent changes the geometric parameter of the heat spreader from uniform thickness to variable thickness. By adjusting the thickness distribution (making center thicker than edges), the thermal expansion characteristics are modified to match CTE differences, preventing warpage in thin packages.
2Volume of moving object
If integrated heat spreader is omitted to reduce size, then package size is reduced, but TIM pump-out occurs due to die surface curvature changes
Solution Approach 1:
The patent implements local quality through a heat spreader with non-uniform thickness, where the central region has greater thickness than the peripheral regions. This localized thickness variation provides enhanced thermal coupling and mechanical stability at the critical center area, preventing TIM pump-out while allowing thin package overall dimensions.
Solution Approach 2:
The patent employs composite material structure by combining the heat spreader with the IC die and package substrate in a multi-layer assembly. The heat spreader acts as an intermediate component that compensates for thermal expansion differences and maintains uniform thermal coupling, preventing TIM pump-out without requiring additional size.
3Stability of the object's composition
If TIM thickness is increased to accommodate die thickness variation, then thermal coupling is improved, but thermal resistance increases
Solution Approach 1:
The patent applies local quality by creating a heat spreader with varying thickness - thicker in the center and thinner at the periphery. This localized thickness variation compensates for die thickness differences, ensuring uniform thermal coupling across all die regions while minimizing overall TIM thickness and associated thermal resistance.
Solution Approach 2:
The heat spreader serves as an intermediary component between the IC die and the external environment. It mediates the thermal coupling by providing a compliant interface that adapts to die thickness variations, ensuring uniform thermal contact without requiring excessive TIM thickness that would increase thermal resistance.
4Ease of manufacture
If uniform heat spreader thickness is used, then manufacturing is simplified, but step height variation between neighboring die cannot be accommodated
Solution Approach 1:
The patent implements local quality by manufacturing the heat spreader with non-uniform thickness, where the central region is made thicker than the peripheral regions. This localized variation accommodates step height differences between neighboring die of varying thicknesses, ensuring uniform thermal interfaces while remaining manufacturable through techniques like selective removal or deposition.
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 solution effectively addresses warpage issues and maintains thermal performance by ensuring uniform thermal coupling across IC dies of varying thicknesses, reducing thermal resistance and preventing TIM pump-out, thereby enhancing the longevity and efficiency of compute systems.
Implementation Method 1
solderable thermal interface structures for assemblies including solder array thermal interconnects
Implementation Method 2
Temperature coefficients of thermal expansion (CTE) may differ between a device and package materials, which may contribute to the problem of warpage
Data Source
AI summary
Thermal heat spreaders and/or an IC die with solderable thermal structures may be assembled together with a solder array thermal interconnects. A thermal heat spreader may include a non-metallic material and one or more metallized surfaces suitable for bonding to a solder alloy employed as thermal interface material between the heat spreader and an IC die. An IC die may include a metallized back-side surface similarly suitable for bonding to a thermal interconnect comprising a solder alloy. Metallization on the IC die and/or heat spreader may comprise a plurality of solderable structures. A multi-chip package may include multiple IC die having different die thickness that are accommodated by a z-height thickness variation in the thermal interconnects and/or the solderable structures of the IC die or heat spreader.