Expandable Sheet Shrinkage Prevention via Minute Projections
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Solution Overview
Problem
The existing method for dividing a workpiece, such as a wafer, into individual chips using an expandable sheet faces challenges in maintaining the spacing between adjacent chips, leading to potential damage during handling due to shrinkage of the expandable sheet, which can cause vacuum leakage and unreliable suction holding.
Innovation Solution
An expanding method and apparatus that includes a holding unit for the annular frame, a pushing unit to expand the annular area of the expandable sheet perpendicular to the holding surface, and a suction holding table with minute projections to prevent shrinkage, ensuring reliable suction holding and maintaining chip spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the expandable sheet is expanded to maintain spacing between chips, then chip spacing is maintained, but the sheet may shrink when push force is removed causing vacuum leakage
Solution Approach 1:
The patent applies preliminary anti-action by forming minute projections on the holding table surface before the expandable sheet is placed. These projections pre-establish a mechanical constraint that prevents the sheet from shrinking inward when push force is removed, counteracting the natural tendency of the elastic sheet to return to its original state and causing vacuum leakage.
Solution Approach 2:
The minute projections act as an intermediary element between the holding table and the expandable sheet. They provide a mechanical interface that transfers the preventive constraint to the sheet, mediating between the vacuum holding requirement and the sheet's elastic shrinkage tendency without requiring direct modification of the sheet itself.
2Reliability
If the expandable sheet is held under suction, then the workpiece can be held securely, but shrinkage of the sheet causes vacuum leakage and unreliable holding
Solution Approach 1:
The minute projections pre-establish a mechanical barrier that prevents the expandable sheet from shrinking inward. This preliminary constraint counteracts the sheet's elastic recovery tendency before it can cause vacuum leakage, ensuring continuous reliable vacuum holding throughout the process.
Solution Approach 2:
The projections provide beforehand cushioning by creating a mechanical stop that prevents excessive shrinkage of the expandable sheet. This preparatory constraint protects the vacuum system from leakage caused by sheet contraction, cushioning against the potential harmful effect before it occurs.
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 prevents shrinkage of the expandable sheet, maintaining the spacing between adjacent chips and ensuring reliable suction holding, thereby preventing chip damage during handling.
Implementation Method 1
holding the workpiece through the expandable sheet on a holding table under suction
Data Source
AI summary
An expanding method for expanding an expandable sheet is provided. A wafer is attached to a central portion of the expandable sheet and an annular frame is attached to a peripheral portion of the expandable sheet. The expanding method includes an annular frame holding step of holding the annular frame by using a holding unit, an expanding step of pushing the expandable sheet by using a pushing unit, thereby expanding the expandable sheet, a suction holding step of holding the wafer through the expandable sheet on a holding table under suction, and a push force removing step of removing a push force applied from the pushing unit to the expandable sheet. A minute projection for preventing the shrinkage of the expandable sheet is formed on the holding table along the outer circumference thereof.