Diffusion Bonding for Substrate Thermal Conductance
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Solution Overview
Problem
Conventional methods for forming high-performance chip scale thermal conductance interfaces during substrate assembly are inadequate in achieving efficient thermal conductivity from chips to cooling systems, often requiring multiple layers and materials that increase complexity and cost.
Innovation Solution
A method involving the deposition of alternating metal layers on substrates, where copper is used to form an interlayer that diffuses under bonding conditions, eliminating the need for conventional thermal interface materials and allowing for bonding at low temperatures and pressures, resulting in enhanced thermal conductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional thermal interface materials (TIM) are used to bond substrates, then thermal conductance is achieved, but the bond line thickness increases and thermal resistance increases
Solution Approach 1:
The patent removes conventional thermal interface materials (TIM) from the bonding structure entirely. Instead of using separate TIM layers between substrates, the invention uses direct metal-to-metal diffusion bonding to achieve thermal conductance, thereby eliminating the additional thickness and thermal resistance that TIM layers would introduce.
Solution Approach 2:
The patent employs a composite metal layer structure where a first metal layer and a second metal layer with different compositions are used together. The first metal layer (e.g., copper) provides high thermal and electrical conductivity, while the second metal layer (e.g., palladium or platinum) forms a diffusion barrier, creating a composite structure that achieves both thermal conductance and controlled diffusion.
2Temperature
If multiple layers of thermal interface materials are used to improve thermal conductivity, then thermal dissipation capability is enhanced, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple thermal interface materials into a single diffusion bonding interface. Instead of stacking multiple TIM layers to achieve thermal dissipation, the invention combines thermal conduction and bonding functions into one direct metal-to-metal contact, reducing the number of layers from multiple TIM layers to just the essential metal diffusion bond.
3Strength
If conventional bonding methods are used to bond substrates, then structural integrity is achieved, but bonding temperature and pressure must be high
Solution Approach 1:
The patent changes the bonding parameters by using a two-layer metal structure that enables diffusion bonding at lower temperatures and pressures compared to conventional single-layer bonding. The presence of the diffusion barrier layer (second metal) allows controlled atomic diffusion that creates strong bonds without requiring the high temperatures and pressures needed for conventional direct metal bonding.
4Temperature
If conventional thermal interface materials are used, then thermal conductance is achieved, but junction-to-case resistance increases
Solution Approach 1:
The patent removes conventional thermal interface materials that inherently possess thermal resistance. By using direct metal-to-metal diffusion bonding without intermediate TIM layers, the invention eliminates the additional thermal resistance that would be introduced by multiple material interfaces, thereby reducing junction-to-case resistance.
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 approach significantly improves thermal conductance by up to ten times compared to conventional methods, reduces junction-to-case resistance, and enables a thin bond line with a small footprint, while being performed at low temperatures and pressures in a short time.
Implementation Method 1
portions of the first layer of metal diffusing through the second layer of metal and portions of the third layer of metal diffusing through the fourth layer of metal
Data Source
AI summary
Methods and apparatus for processing a substrate are provided herein. For example, the method can include depositing a first layer of metal on a first substrate; depositing a second layer of metal atop the first layer of metal; depositing a third layer of metal on a second substrate; depositing a fourth layer of metal atop the third layer of metal; and bringing the second layer of material into contact with the fourth layer of material under conditions sufficient to cause the first substrate to be bonded to the second substrate by a diffusion layer formed by portions of the first layer of metal diffusing through the second layer of metal and portions of the third layer of metal diffusing through the fourth layer of metal.