Chuck Table Height Offset Prevents Double Grinding
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Solution Overview
Problem
In creep-feed grinding processes, the workpiece located at the rear end may be ground twice, leading to thickness variations and potential damage such as saw marks, scratches, or cracks on the workpiece.
Innovation Solution
A chuck table with multiple holding surfaces of the same shape, disposed in increasing height order, is used to prevent double grinding by positioning the grinding unit at different heights for each workpiece, ensuring that each workpiece is ground only once.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If creep-feed grinding is executed on multiple workpieces held by multiple holding surfaces, then productivity is improved, but the rear end workpiece may be ground twice causing thickness variation and potential damage
Solution Approach 1:
The patent introduces a height dimension (Z-axis) to the grinding system by providing holding surfaces at different heights. The first holding surface is positioned at a first height and the second holding surface at a second height different from the first height. This vertical dimensional differentiation allows the grinding unit to process workpieces at different elevation levels, preventing the rear end workpiece from being ground twice while maintaining high productivity through parallel processing of multiple workpieces.
2Productivity
If creep-feed grinding is executed on multiple workpieces held by multiple holding surfaces, then productivity is improved, but the rear end workpiece may suffer damage such as saw marks, scratches, or cracks
Solution Approach 1:
By positioning holding surfaces at different heights along the Z-axis, the patent creates a vertical separation between workpiece processing zones. The grinding unit can selectively engage workpieces at specific heights, ensuring that the rear end workpiece held by the second holding surface is not inadvertently ground again by abrasive stones that have passed through the first holding surface zone. This dimensional separation eliminates harmful double-grinding effects such as saw marks, scratches, or cracks.
Solution Approach 2:
The patent introduces the height difference as an intermediary mechanism between the grinding unit and the workpieces. By positioning the second holding surface at a different height than the first holding surface, this vertical offset acts as a protective intermediary that prevents the grinding abrasive stones from contacting the rear end workpiece a second time, thereby preventing damage while allowing continuous high-speed processing of multiple workpieces.
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 solution effectively prevents double grinding of specific workpieces, reducing thickness variations and minimizing the risk of damage such as saw marks, scratches, or cracks, thereby improving the consistency and quality of the grinding process.
Implementation Method 1
multiple grinding abrasive stones located on the front side of the rotating grinding wheel are brought into contact with the side of the upper surface (back surface) of the wafer held by the chuck table from the rear side thereof. As a result, the side of the upper surface (back surface) of the wafer is ground from the rear end to the front end by the multiple grinding abrasive stones.
Data Source
AI summary
Multiple holding surfaces of a chuck table are disposed in such a manner that the heights thereof from a reference surface are in increasing order along a first direction parallel to each of them. Thus, in a case of using this chuck table, creep-feed grinding for workpieces each held by a respective one of the multiple holding surfaces can be executed in states in which a grinding unit is positioned at different heights. In this case, the workpiece for which the creep-feed grinding has been executed is located on the lower side as viewed from the grinding unit when another workpiece is ground. Due to this, in this creep-feed grinding, a specific workpiece can be prevented from being ground twice.