Low CTE Heat Spreader Lid for Flip Chip Thermal Management
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Solution Overview
Problem
Conventional heat spreaders in flip chip packaging face issues with coefficient of thermal expansion (CTE) mismatch between copper lids and ceramic substrates, leading to stress concentration and delamination, while materials with low CTE offer poor thermal performance.
Innovation Solution
A thermally enhanced heat spreader with a lid made of low CTE materials like copper tungsten or aluminum-silicon-carbide, incorporating a thermal interface material and a vapor chamber with a working fluid, and a secure attachment mechanism to mitigate delamination and improve thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper lid is used for heat spreader, then thermal conductivity is improved, but CTE mismatch with ceramic substrate causes stress concentration and delamination
Solution Approach 1:
The patent employs copper tungsten (CuW) composite material for the heat spreader lid, combining copper's high thermal conductivity with tungsten's low CTE properties. This composite approach resolves the contradiction by achieving both excellent thermal performance and CTE compatibility with the ceramic substrate, eliminating stress concentration and delamination issues while maintaining effective heat dissipation.
2Strength
If low CTE materials like CuW or AlSiC are used, then CTE mismatch is resolved, but thermal conductivity deteriorates compared to copper
Solution Approach 1:
The patent optimizes the composition parameters of the CuW composite material, specifically controlling the tungsten content within 1-30 wt% and copper content within 70-99 wt%. By precisely adjusting these compositional parameters, the heat spreader achieves both CTE compatibility with the ceramic substrate and sufficient thermal conductivity, resolving the trade-off between mechanical compatibility and thermal performance.
3Power
If higher power consumption circuits are used, then device functionality is improved, but heat generation increases causing hot spots
Solution Approach 1:
The patent incorporates a vapor chamber structure that utilizes phase transition of working fluid (liquid to vapor and back) for heat transport. The phase change process absorbs and releases latent heat efficiently, enabling the heat spreader to handle high power consumption and dissipate hot spots generated by high-power circuits, thereby resolving the temperature increase issue while maintaining device functionality.
4Quantity of substance
If more densely packaged microelectronic devices are used, then packaging density is improved, but heat dissipation capability deteriorates
Solution Approach 1:
The patent transitions from conventional two-dimensional heat spreading to three-dimensional heat management by incorporating a vapor chamber with vertical vaporization and condensation pathways. This dimensional enhancement provides additional heat transfer paths, enabling effective heat dissipation in densely packaged devices where horizontal heat spreading alone is insufficient, thus resolving the heat dissipation deterioration issue.
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 CTE mismatch and enhances thermal dissipation by using a low CTE lid and interface material, reducing the risk of delamination and improving heat spreading across a larger surface area.
Implementation Method 1
a vapor chamber with a working fluid
Implementation Method 2
a thermal interface material and a vapor chamber with a working fluid
Implementation Method 3
coefficient of thermal expansion (CTE) mismatch between the copper lid and the low CTE ceramic substrate
Data Source
AI summary
A flip chip microelectronic package having a heat spreader is provided. In one embodiment, the microelectronic package comprises a die having a first surface and a second surface, the first surface being coupled to a substrate; a thermal interface material disposed in thermal conductive contact with the second surface of the die; and a heat spreader adapted for dissipating heat from the die, the heat spreader disposed in thermal conductive contact with the thermal interface material. The heat spreader includes a lid having an inner chamber therein defined by a first wall and a second wall, the second wall securely joined to the first wall to seal the chamber, the lid being mounted to the substrate and a wick layer positioned in the chamber.