Workpiece Grinding Method for Thin Device Chips
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Solution Overview
Problem
The existing grinding methods for forming a ring-shaped reinforcement part on the back surface of a workpiece, used to thin device chips for electronic apparatuses, often result in grinding faults due to the reduced grinding capability of the grinding wheel, particularly when a hard oxide film is present, leading to issues like dulling, shedding, and clogging.
Innovation Solution
A grinding method that uses a grinding apparatus with a chuck table and a spindle-mounted grinding wheel with segment-shaped grindstones, where the workpiece is held stationary during the initial groove formation and then rotated during the groove removal and recess formation steps, allowing the side surfaces of the grindstones to reduce the load on the bottom surfaces and minimize grinding faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a grinding wheel with smaller diameter and fewer grindstones is used to form a ring-shaped reinforcement part, then the workpiece strength is enhanced and warp is reduced, but the grinding capability of the grindstone is lowered leading to dulling, shedding, and clogging
Solution Approach 1:
The invention applies dynamics by rotating the chuck table during the groove removing step, transforming the grinding process from a stationary workpiece to a dynamic rotating workpiece. This allows the grindstones to contact different portions of the groove sequentially, distributing the grinding load and reducing wear on individual grindstones, thereby preventing dulling, shedding, and clogging while maintaining the ring-shaped reinforcement part formation
Solution Approach 2:
The invention employs periodic action by alternating between different grinding phases: groove forming step (stationary chuck table) and groove removing step (rotating chuck table). This periodic alternation allows the grindstones to periodically engage and disengage from different workpiece surfaces, reducing continuous contact stress and preventing grindstone degradation while effectively removing the groove and forming the reinforcement part
2Shape
If the peripheral speed of the grinding wheel is reduced, then the ring-shaped reinforcement part can be formed, but the work amount per grindstone is increased causing grinding faults
Solution Approach 1:
The invention applies segmentation by dividing the groove removing step into multiple discrete grinding operations as the chuck table rotates. Each grindstone processes a specific angular segment of the groove, and the rotation distributes the total work amount across multiple grindstones and multiple rotational cycles. This segmentation reduces the cumulative work burden on each individual grindstone, preventing grinding faults while maintaining the required ring-shaped reinforcement structure
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 method effectively reduces the worsening of grindstone condition, preventing grinding faults even when a hard oxide film is present, by alternating the grinding surfaces used, thereby enhancing the grinding capability and preventing warping and cracking of the workpiece.
Implementation Method 1
a grinding unit that includes a spindle and, in a state in which a grinding wheel having a plurality of grindstones disposed in an annular pattern is mounted to the spindle and is rotated around the spindle, grinds the workpiece held on the chuck table
Data Source
AI summary
A workpiece has a device area and a peripheral area surrounding the device area on a front surface side thereof. A workpiece grinding method includes a groove forming step of performing grinding feed of a grinding unit while a spindle is rotated, and grinding a predetermined area on a back surface side of the workpiece, the predetermined area corresponding to the device area, in a state in which a chuck table holding the workpiece is not rotated, thereby forming a groove on the back surface side, a groove removing step of starting rotation of the chuck table while the spindle is kept rotating, thereby grinding side walls of the groove and removing the groove, and a recess forming step of performing grinding feed of the grinding unit while the spindle and the chuck table are rotated, thereby grinding the predetermined area and forming a recess and a ring-shaped reinforcement part.