Solderable Thermal Interface Structures for Warpage-Tolerant IC Dies
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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
1Length of moving object
If thin form-factor packages are used without an integrated heat spreader, then device thickness is reduced, but thermal interface material is pumped out due to die surface curvature changes, causing thermal performance to decline
Solution Approach 1:
The patent introduces an integrated heat spreader (IHS) as an intermediary component between the IC die and external heat sinks. The IHS provides a large thermal mass and conductive pathway that stabilizes thermal interface material (TIM) retention during thermal cycling, preventing pump-out while maintaining thin form-factor packaging. The IHS acts as a mediator that absorbs thermal expansion stresses and maintains consistent thermal coupling.
2Manufacturing precision
If variation in die thickness and first level interconnect height is accommodated by increasing TIM thickness, then step height variation between neighboring die is reduced, but thermal resistance increases
Solution Approach 1:
The patent employs compliant thermal interface structures including solder bumps and underfill materials that dynamically adapt to thickness variations between neighboring IC dies. These dynamic interface structures flex and deform to accommodate step height variations without requiring excessive TIM thickness, thereby maintaining low thermal resistance while ensuring complete thermal coupling across the IHS interface.
3Reliability
If solderable thermal interface structures with varying thicknesses are fabricated, then thermal coupling consistency across different IC die thicknesses is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes parameter changes in the IHS design, specifically varying the thickness of the IHS at different locations to match the thickness variations of different IC dies. This allows consistent thermal coupling across all dies in a multi-chip package. The manufacturing process achieves this through selective removal or addition of material during IHS fabrication, balancing the increased manufacturing complexity with improved thermal performance.
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 consistent thermal coupling across IC dies of varying thicknesses, reducing thermal resistance and extending the system's lifespan.
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
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.