Carbon Nanotube Thermal Interface for Semiconductor Heat Transfer
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Solution Overview
Problem
Conventional thermal interface materials, such as solder materials, face challenges with adhesion to silicon substrates and package lids, leading to delamination due to mismatched thermal expansion coefficients, resulting in reduced thermal conduction and potential hot spots during thermal cycling.
Innovation Solution
A thermal interface structure incorporating plural carbon nanotubes with solderable metal layers is used, which are grown on the lid and coated with compliant materials to enhance adhesion and resistance to shear stresses, facilitating a strong bond between the semiconductor chip, thermal interface material, and lid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solder thermal interface material is used, then thermal conduction is achieved, but adhesion to silicon and package lid deteriorates due to mismatched thermal expansion coefficients, leading to delamination
Solution Approach 1:
The patent introduces an intermediary compliant layer between the rigid solder thermal interface material and the package lid. This compliant layer acts as a mediator that absorbs thermal expansion mismatches and shear stresses, preventing delamination while maintaining thermal conduction. The compliant layer is specifically positioned between the solder material and the lid to decouple the thermal expansion differences between silicon, solder, and lid materials.
Solution Approach 2:
The patent changes the mechanical properties parameter of the thermal interface structure by introducing a compliant layer with specific elasticity characteristics. This parameter change allows the structure to accommodate thermal cycling stresses while maintaining strong adhesion. The compliant layer's elastic modulus is specifically selected to match the thermal expansion characteristics of the underlying materials.
2Reliability
If rigid solder material is used for thermal interface, then thermal conduction is improved, but resistance to shear stresses from thermal expansion mismatch deteriorates
Solution Approach 1:
The patent employs a flexible compliant layer as a thin film between the rigid solder material and the package lid. This thin film is specifically designed to be flexible and compliant, allowing it to absorb shear stresses generated by thermal expansion mismatches during thermal cycling, while the rigid solder material above it maintains effective thermal conduction to the silicon die.
Solution Approach 2:
The compliant layer serves as an intermediary element that decouples the rigid solder thermal interface material from the package lid. This intermediary absorbs and dissipates shear stresses, protecting the solder-material interface from delamination while preserving the thermal conduction pathway established by the solder material.
3Reliability
If metallization stack is added to silicon backside, then adhesion to solder is improved, but device complexity increases
Solution Approach 1:
The patent extracts the adhesion function from the complex metallization stack and relocates it to the compliant layer interface with the silicon die. By taking out the adhesion requirement from the solder-silicon interface, the metallization stack on the silicon backside can be simplified or eliminated, reducing device complexity while maintaining reliable solder adhesion through the compliant layer's adhesive properties.
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 carbon nanotube-based thermal interface structure provides improved thermal conductivity and resistance to shear stresses, preventing delamination and maintaining effective heat transfer across thermal cycles.
Implementation Method 1
Some conventional integrated circuits, such as microprocessors, generate sizeable quantities of heat that must be transferred away to avoid device shutdown or damage. The lid serves as both a protective cover and a heat transfer pathway.
Implementation Method 2
A solder thermal interface material like indium has favorable thermal properties that work well for high power-high temperature die.
Implementation Method 3
The metallurgical bond between a conventional solder interface material and a semiconductor chip package lid can be subjected to considerable shear stresses.
Implementation Method 4
the metallurgical bond between a conventional solder interface material and a semiconductor chip package lid can be subjected to considerable shear stresses. As the system of those three components goes through thermal cycling during testing or actual operation, the thermal interface material to lid bond undergoes cyclic shear stresses.
Data Source
AI summary
Various thermal interface structures and methods are disclosed. In one aspect, a method of manufacturing is provided. The method includes providing plural carbon nanotubes in a thermal interface structure. The thermal interface structure is soldered to a side of a semiconductor chip. In another aspect, an apparatus is provided. The apparatus includes a thermal interface structure that has plural carbon nanotubes. A semiconductor chip is soldered to the thermal interface structure.