Cathodic Arc Coater Disk Cathode Segmentation
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Solution Overview
Problem
Current cathodic arc vapor deposition methods are limited by slow deposition rates, making it impractical to apply thick coatings within a commercially viable time frame, and increasing current can lead to cathode melting and undesirable particle formation.
Innovation Solution
A cathodic arc coater with a disk-shaped cathode and a magnetic field generator to control the arc spot, allowing for a higher electrical current without melting the cathode, by maintaining a maximum acceptable power density and heat transfer flux, thereby increasing deposition rates up to 4.0 mils per hour.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the current applied to the cathode is increased to increase the deposition rate, then the deposition rate is improved, but the cathode may melt or produce undesirable macroscopic particles
Solution Approach 1:
The cathode is segmented into multiple arc spots distributed across its surface. Instead of concentrating the entire current through a single arc spot, the current is divided into multiple parallel arc paths. This segmentation allows the total current to be increased for higher deposition rate while each individual arc spot receives a controlled current density that prevents cathode melting and particle formation.
2Quantity of substance
If a thick coating is applied to meet commercial requirements, then the coating thickness is improved, but the time required for deposition becomes excessively long
Solution Approach 1:
The cathode surface is divided into multiple arc spots that operate simultaneously. This segmentation of the deposition process into parallel zones allows thick coatings to be deposited in a fraction of the time it would take a single arc spot, making thick coating applications commercially viable.
3Productivity
If the arc energy density is increased to accelerate material vaporization, then the deposition rate is improved, but the cathode material may be damaged or particles may be liberated
Solution Approach 1:
The total arc energy is segmented into multiple lower-density arc spots. Each arc spot operates at a safe energy density that prevents cathode damage and particle liberation, while the cumulative effect of multiple arc spots achieves the desired high deposition rate.
Solution Approach 2:
The deposition process is transitioned from a one-dimensional single-arc-spot model to a two-dimensional multi-arc-spot distribution across the cathode surface. This dimensional expansion allows the system to achieve high total deposition rates while maintaining safe local energy densities at each arc spot.
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
Enables the application of thick coatings (10-200 mils) within a practical time frame while maintaining cathode integrity, doubling the deposition rate and reducing macroscopic particle formation.
Implementation Method 1
A cathodic arc coater with a disk-shaped cathode and a magnetic field generator to control the arc spot
Implementation Method 2
Cathodic arc vapor deposition involves a source material and a substrate to be coated placed in an evacuated deposition chamber
Implementation Method 3
The energy deposited by the arc at an arc spot is intense; on the order of 10^5 to 10^7 amperes per square centimeter with a duration of a few to several microseconds. The intensity of the energy raises the local temperature of the arc spot to approximately equal that of the boiling point of the cathode material
Implementation Method 4
The negative lead of a direct current (DC) power supply is attached to the source material (hereinafter referred to as the 'cathode') and the positive lead is attached to an anodic member
Data Source
AI summary
A method for applying a coating by a cathodic is provided. The method includes the steps of: a) providing a cathodic arc coater that includes a power source and utilizes a disk-shaped cathode, the cathode having an evaporative surface extending between a first end surface and a second end surface, wherein the evaporative surface has an area; b) determining a maximum acceptable power density for the evaporative surface; and c) applying a magnitude of electrical current from the power source to the cathode, wherein the electrical current magnitude divided by the area is equal to or less than the maximum acceptable power density for the evaporative surface.