Floating Workpiece Carrier Head for High-Speed Sapphire Lapping
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Solution Overview
Problem
Conventional abrasive lapping and polishing systems are limited by slow speeds and inefficiencies, particularly in achieving high rotational speeds necessary for high-speed lapping and polishing of ultra-hard materials like sapphire and tungsten carbide, leading to increased production time and costs.
Innovation Solution
A high-speed abrasive lapping or polishing workpiece head system utilizing a translatable workpiece carrier head with a precision-flat platen and fixed-abrasive coated island discs, allowing for high rotational speeds and uniform material removal across the surface of workpieces, including semiconductor wafers and sapphire wafers, using diamond or other abrasive particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional liquid abrasive slurry systems are used, then subsurface damage is minimized, but material removal rate is slow (40 times slower than fixed abrasive systems)
Solution Approach 1:
The patent replaces the conventional liquid slurry mechanical abrasion system with a fixed abrasive disc system that uses mechanical contact and friction. The fixed abrasive particles are bonded to the disc surface, creating a more efficient material removal mechanism through direct mechanical action rather than liquid slurry transport, achieving 40x faster material removal rates.
Solution Approach 2:
The invention changes the physical state and delivery mechanism of the abrasive from liquid slurry to fixed bonded particles on a rotating disc. This parameter change in abrasive delivery enables higher material removal rates while maintaining surface quality, directly resolving the productivity-time contradiction.
2Productivity
If high rotational speeds are used for high-speed lapping and polishing, then production speed increases, but achieving and maintaining precise flatness becomes more difficult
Solution Approach 1:
The patent employs a spherical bearing mechanism that allows the workpiece carrier head to self-adjust and float, maintaining precise flatness during high-speed rotation. The spherical action accommodates rotational forces while keeping the abrasive surface parallel to the workpiece, enabling both high speed and precision.
Solution Approach 2:
The workpiece carrier head is designed with floating and rigid modes that can dynamically adjust during operation. This dynamic capability allows the system to maintain manufacturing precision at high rotational speeds by automatically compensating for forces generated during high-speed lapping and polishing.
3Manufacturing precision
If a rigid workpiece carrier is used, then manufacturing precision is maintained, but adaptability to surface variations is reduced
Solution Approach 1:
The workpiece carrier head switches between rigid and floating modes dynamically. In floating mode, it adapts to surface variations for better conformability; in rigid mode, it maintains manufacturing precision. This dynamic switching resolves the contradiction between precision and adaptability.
Solution Approach 2:
The carrier head incorporates floating elements that provide flexibility and adaptability while maintaining overall structural rigidity. This combination allows the system to conform to surface variations when needed while preserving manufacturing precision during stable operation.
4Adaptability or versatility
If floating workpiece carrier head is used, then adaptability to surface variations improves, but structural stability decreases
Solution Approach 1:
The system dynamically switches between floating and rigid modes. The floating mode provides adaptability and conformability to surface variations, while the rigid mode ensures structural stability. This dynamic transition resolves the contradiction between adaptability and stability.
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 system significantly increases production speeds and reduces costs by enabling high-speed lapping and polishing of ultra-hard materials, achieving material removal rates 40 times faster than conventional liquid abrasive slurry systems while minimizing subsurface damage and maintaining precise flatness.
Implementation Method 1
a translatable workpiece carrier head (132) having a spherical bearing (104, 108) that allows a rotating workpiece (170) attached to a workpiece carrier plate (102) to assume conformal contact with a moving flat-surfaced abrasive (100)
Implementation Method 2
The spherical center of rotation (166) of the spherical bearing (104, 108) is located at a distance (169) from the workpiece (170) mounting surface (101) that prevents tilting of the workpiece carrier plate (102) and attached workpiece (170) by lateral frictional abrading forces
Implementation Method 3
uniform material removal across the surface of workpieces, including semiconductor wafers and sapphire wafers, using diamond or other abrasive particles
Data Source
AI summary
Embodiments of a high-speed rotatable workpiece abrasive polishing head are disclosed that allow flat surfaced hard material workpieces or sapphire or semiconductor wafers to be polished at high abrading speeds that can use water-mist cooled quick-change fixed abrasive island-type discs. Workpieces can be quickly attached with vacuum to a rotatable workpiece plate having a curved (e.g., spherical) bearing with an offset spherical center of rotation located at the workpiece abraded surface. Abrading contact there prevents lateral abrading friction forces from tilting workpieces and causing non-flat workpiece surfaces. The workpiece carrier plate can be rotationally driven by a floating drive shaft having a spherical spline head that contacts the workpiece carrier plate at a position close to the workpiece abraded surface to avoid tilting of the workpiece due to the shaft-applied workpiece rotation forces. The workpiece head can allow the workpieces to either float in contact with the abrasive or be held in rigid contact with the abrasive.