Substrate Grinding Inertial Correction via Motor Load
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Solution Overview
Problem
The existing substrate grinding methods face challenges in achieving uniform substrate thickness due to variations in inertial grinding caused by residual stress, which leads to inconsistencies in substrate thickness despite fixed grinding conditions.
Innovation Solution
A grinding method and device that monitor the motor load current to correlate with the amount of inertial grinding, allowing for real-time adjustment of the spark-out start position to account for residual stress, ensuring the substrate thickness is accurately reduced to the desired value by incorporating the calculated inertial grinding amount into the desired thickness measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed correction value for inertial grinding is used during spark-out, then the grinding process is simple to operate, but the substrate thickness varies due to changes in inertial grinding amount
Solution Approach 1:
The patent changes the parameter used for correction from a fixed value to a dynamically variable value based on motor load current. The correction value is adjusted according to the actual inertial grinding amount, which varies with motor load current during spark-out. This allows the system to adapt to changing conditions while maintaining operational simplicity through automated measurement and adjustment.
Solution Approach 2:
The patent introduces feedback by measuring the actual substrate thickness after spark-out and using this information to adjust the correction value for subsequent operations. The system continuously monitors the relationship between motor load current and inertial grinding amount, creating a closed-loop control that improves thickness uniformity while keeping the process easy to operate.
2Manufacturing precision
If the spark-out start position is set higher to compensate for inertial grinding, then the desired thickness is achieved on average, but excessive grinding occurs when inertial grinding is greater than expected
Solution Approach 1:
The patent makes the spark-out start position dynamic rather than fixed. The position is adjusted in real-time based on the measured motor load current and the corresponding inertial grinding amount. This dynamic adjustment allows the system to precisely control the spark-out start position for each substrate, achieving desired thickness accuracy without causing excessive grinding that could damage the substrate.
3Productivity
If the grinding tool feed is stopped at the desired thickness position, then the grinding process is efficient, but residual stress causes inertial grinding that reduces substrate thickness below the desired value
Solution Approach 1:
The patent applies preliminary action by calculating and compensating for the inertial grinding amount before spark-out occurs. The system determines the correction value based on motor load current measurements taken during the grinding process, and uses this information to adjust the spark-out start position in advance. This preliminary compensation prevents the substrate thickness from dropping below the desired value due to inertial grinding, maintaining both efficiency and precision.
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 ensures consistent and accurate substrate thickness by dynamically adjusting the spark-out start position based on the motor load current, thereby minimizing variations in substrate thickness across multiple grinding operations.
Implementation Method 1
motor load current monitoring means for monitoring a load current in the motor
Implementation Method 2
substrate thickness measuring means for measuring the thickness of the substrate held by the holding means during grinding
Implementation Method 3
grinding means opposed to the holding surface and having a rotation axis extending substantially parallel to a rotation axis of the holding means
Data Source
AI summary
A grinding method wherein the correlation between the amount of inertial grinding occurring in performing spark-out by a grinding unit and the maximum load current in a motor of the grinding unit is grasped, and a correction value for the amount of inertial grinding corresponding to the maximum load current is preliminarily obtained. When the wafer thickness measured by a thickness measuring gauge has reached the sum of a desired value and the correction value (=the amount of inertial grinding) corresponding to the maximum load current, the spark-out is started. Accordingly, the wafer thickness becomes the desired value after the inertial grinding in performing the spark-out.