Lidless Flip Chip Package Thermal Management
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Solution Overview
Problem
Lidded flip chip packages face issues with heat transfer and stress distribution due to non-coplanarity between the heat sink and the silicon die, leading to reduced thermal conductivity and potential durability problems, especially as silicon power increases.
Innovation Solution
The implementation of a lid-less flip chip package with support structures and tracks on the silicon die and heat sink surfaces to enhance thermal interface areas, using thermally conductive materials and seed metal coatings to improve heat transfer and distribute compression loads effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lid is added to cover the silicon die, then protection and structural completeness are improved, but heat transfer efficiency deteriorates due to non-coplanarity between heat sink and die
Solution Approach 1:
The patent removes the lid from the package structure, transitioning from a lidded to a lid-less design. This extraction eliminates the thermal barrier that the lid created, allowing direct thermal contact between the heat sink and silicon die, thereby resolving the heat transfer efficiency issue while maintaining protection through alternative means
Solution Approach 2:
The patent introduces support structures that extend vertically from the substrate to support the heat sink, creating a three-dimensional configuration. This dimensional change allows the heat sink to be positioned in close proximity to the silicon die without requiring a lid, maintaining both protection and optimal thermal contact
2Temperature
If compression load is applied to improve thermal contact, then heat transfer is improved, but stress concentration on solder joints worsens
Solution Approach 1:
The patent divides the load-bearing function into multiple support structures distributed around the periphery of the silicon die. These segmented support points distribute the compression load across multiple locations rather than concentrating it at single points, reducing stress on solder joints while maintaining thermal contact
Solution Approach 2:
The support structures are strategically positioned at specific locations around the die perimeter where they provide localized support and thermal contact. This local quality approach ensures compression is applied where most beneficial for thermal contact while avoiding areas where it would concentrate stress on solder joints
3Stress or pressure
If support structures are added to distribute load, then stress distribution is improved, but device complexity worsens
Solution Approach 1:
The support structures serve multiple functions simultaneously: they provide mechanical support for the heat sink, distribute compression loads to reduce stress concentration, and enhance thermal contact between the heat sink and silicon die. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity
Solution Approach 2:
The patent merges the support function and thermal contact function into a single integrated support structure system. Rather than having separate support elements and separate thermal interface components, the support structures perform both roles, simplifying the overall device architecture while achieving stress distribution
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 enhances heat transfer efficiency and reduces stress concentrations, ensuring better thermal conductivity and durability by maintaining even contact between the heat sink and silicon die, even when components are non-coplanar, and supports precise dimensional control during manufacturing.
Implementation Method 1
The thermal interface material may be a cooling liquid. At least one of the die, first lid, second lid and sink surfaces has tracks formed therein configured to receive a thermal interface material
Implementation Method 2
The thermal interface material may be a cooling liquid
Data Source
AI summary
A flip chip package includes a substrate, a silicon die supported on and electrically connected with the substrate, and a lid attached with the substrate and covering the silicon die. The silicon die has a die surface including a first set of tracks formed therein, and the lid may have a lid surface including a second set of tracks formed therein. A thermal interface material may be disposed between the die surface and lid surface and at least partially fill the first and second sets of tracks.