Workpiece Grinding Method Using Segmented Spindle and Chuck Control
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Solution Overview
Problem
The existing wafer grinding methods face processing failures due to premature shedding of abrasive grits from grinding stones, especially when a hard oxide film is present, leading to a prolonged period of reduced grinding capability.
Innovation Solution
A method involving a groove formation step where an arcuate groove is created without rotating the chuck table, followed by a groove removal step where the groove is ground at the side walls with the spindle rotating, and a full surface grinding step where the workpiece is ground in its entirety with the spindle and chuck table rotating, primarily using the bottom surfaces of the grinding stones to maintain their condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous full surface grinding is performed with both chuck table and spindle rotating, then grinding efficiency is improved, but abrasive grits shed prematurely due to hard oxide film, reducing grinding capability
Solution Approach 1:
The grinding process is segmented into three distinct stages: groove formation (spindle only), groove removal (chuck table rotation), and full surface grinding (both rotating). This segmentation allows different grinding surfaces of the stones to be utilized sequentially, preventing premature shedding while maintaining efficiency
Solution Approach 2:
The rotational states of the chuck table and spindle are dynamically adjusted across different grinding stages. The chuck table rotates only during groove removal and full surface grinding, while the spindle rotates throughout. This dynamic control optimizes contact patterns between grinding stones and workpiece, preventing abrasive grit shedding
2Reliability
If grinding is continued after abrasive grits fall off, then self-sharpening occurs to restore grinding capability, but processing time increases and processing failures occur
Solution Approach 1:
The three-stage grinding method preliminarily prepares the workpiece by forming grooves and removing them before final full surface grinding. This preliminary action reduces the overall grinding load and duration required in the final stage, minimizing the period when grinding capability is reduced and preventing processing failures
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 approach reduces the deterioration of grinding stone surfaces, maintaining their grinding capability and preventing processing failures even with a hard oxide film, by alternating the use of different surfaces of the grinding stones throughout the process.
Implementation Method 1
a chuck table that holds the workpiece under suction
Implementation Method 2
Abrasive grits that project from the binder of the grinding stones come into contact with the wafer, whereby the wafer is ground
Data Source
AI summary
A workpiece grinding method includes a groove formation step, a groove removal step, and a full surface grinding step. In the groove formation step, the workpiece is ground by performing grinding feed of a grinding unit while rotating a spindle without rotation of a chuck table, so that an arcuate groove is formed with a depth not reaching a finish thickness on a side of a back surface of the workpiece. In the groove removal step, rotation of the chuck table is started with the spindle kept rotating, so that the groove is ground at side walls thereof and is removed from the workpiece. In the full surface grinding step, grinding feed of the grinding unit is performed while the spindle and chuck table are rotated, so that the workpiece is ground in an entirety thereof on the side of the back surface until the workpiece has the finish thickness.