Bonded Diamond Assembly Void Reduction
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Solution Overview
Problem
The challenge lies in bonding large areas of polycrystalline diamond to a substrate while minimizing voids and thermal/barrier resistance, as existing methods face issues with delamination, stress, and reduced power density due to thermal mismatch and uneven bonding.
Innovation Solution
A bonded diamond assembly with a polycrystalline diamond wafer and a substrate bonded using a controlled bonding layer, where ultrasound inspection ensures minimal voids and particulate impurities, and elevated pressure and temperature are applied to enhance bonding, allowing for higher current densities and mechanical load resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If large area polycrystalline diamond is bonded to a substrate, then the working surface area is maximized, but voids and defects increase degrading electrode performance
Solution Approach 1:
The patent changes the physical state and parameters of the bonding material by heating it to its melting point and above, transforming it from a viscous paste into a fluid that can flow and fill voids. This parameter change allows the bonding material to adapt to surface irregularities and eliminate defects while bonding large areas.
Solution Approach 2:
The bonding material undergoes phase transition from solid/viscous state to liquid/molten state during the bonding process. By heating the bonding material above its melting point, it transitions to a fluid phase that can flow into voids and ensure complete contact between diamond and substrate, then solidifies to form a strong bond.
2Reliability
If viscous electrically conducting epoxy paste is used for bonding, then electrical connection is achieved, but uneven application and poor adhesive flow cause voids
Solution Approach 1:
The patent changes the temperature parameter of the bonding material from room temperature to above its melting point during bonding. This parameter change transforms the material from a viscous state with poor flow characteristics into a fluid state that exhibits excellent flow and wetting properties, eliminating voids and ensuring uniform bonding.
Solution Approach 2:
The bonding material acts as an intermediary substance that facilitates the connection between diamond and substrate. By controlling its temperature and phase, it mediates the bonding process to achieve both electrical conductivity and void-free bonding uniformity.
3Reliability
If diamond layer thickness is limited to reduce stress, then delamination is reduced, but the process becomes commercially less attractive
Solution Approach 1:
The bonding material undergoes phase transition to a molten state during bonding, creating a fluid that can flow and fill all interfacial voids and irregularities. This ensures complete wetting and adhesion between diamond and substrate, preventing delamination even in thicker layers without compromising commercial viability.
Solution Approach 2:
By changing the temperature parameter during bonding to above the melting point of the bonding material, the patent achieves superior adhesion that allows thicker diamond layers to be bonded without delamination, maintaining both reliability and commercial attractiveness.
4Quantity of substance
If thicker diamond layers are produced, then more material is available for application, but production cost increases proportionally
Solution Approach 1:
The bonding material transitions to a molten state during bonding, creating a fluid that flows and fills all interfacial voids and irregularities. This ensures complete wetting and adhesion between diamond and substrate, preventing delamination even in thicker layers without compromising commercial viability.
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 bonds larger diamond areas with low thermal and electrical resistivity, reducing void-related issues and maintaining performance across varying temperatures, enabling higher current densities and mechanical stability.
Implementation Method 1
a bonding layer located between the diamond and the substrate and bonding them together
Implementation Method 2
The bonding layer, when inspected using ultrasound using a resolution of 50 μm, a focal length selected to inspect the bonding layer, and frequencies of 100 MHz and 30 MHz
Implementation Method 3
elevated pressure and temperature are applied to enhance bonding
Implementation Method 4
elevated pressure and temperature are applied to enhance bonding
Implementation Method 5
low electrical resistivity while retaining an acceptable amount of voids and particulate impurities in the bonding layer
Implementation Method 6
low thermal barrier resistance
Data Source
AI summary
A bonded diamond assembly and a method of forming the assembly. The assembly comprises a polycrystalline diamond wafer having a largest linear dimension of between 25 mm and 200 mm, a substrate and a bonding layer located between the diamond and the substrate and bonding them together. The bonding layer, when inspected using ultrasound using a resolution of 50 μm, a focal length selected to inspect the bonding layer, and frequencies of 100 MHz and 30 MHz, comprises low numbers of voids extending either across the thickness of the bonding layer and low numbers of voids that do not extend across the thickness of the bonding layer.