Silicon Nitride Substrate Nitriding to Limit Surface Color Unevenness
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Solution Overview
Problem
The existing methods for manufacturing silicon nitride substrates face challenges in achieving high thermal conductivity and accuracy in appearance tests due to color unevenness on the substrate's surface, which can lead to erroneous detection of foreign objects and dusts.
Innovation Solution
The method involves forming a silicon nitride substrate by nitriding silicon in a sheet-shaped green body, with a controlled heating process to maintain a temperature difference of 20°C or less between the green body and the furnace, ensuring a gradual temperature rise to prevent thermal runaway and reduce color unevenness, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rapid heating process is used to increase productivity, then the manufacturing efficiency is improved, but color unevenness occurs on the substrate surface leading to detection errors
Solution Approach 1:
The heating process is divided into multiple stages with different heating rates. A first heating stage uses a first heating rate, followed by a second heating stage with a second heating rate, creating a periodic or sequential action pattern that balances speed and quality control
2Loss of time
If the heating rate is increased to reduce manufacturing time, then productivity is improved, but thermal runaway occurs causing color unevenness
Solution Approach 1:
The heating process employs periodic action by implementing distinct heating stages with different rates, preventing thermal runaway while maintaining efficient production timing
Solution Approach 2:
The heating rate parameter is changed between stages - using a first heating rate in the initial stage and a second heating rate in the subsequent stage, optimizing both time efficiency and process stability
3Measurement precision
If appearance test criteria are eased to avoid false detection of color unevenness, then measurement accuracy is improved, but foreign objects and dusts may be missed
Solution Approach 1:
The color unevenness is prevented during the manufacturing process itself through controlled heating stages, eliminating the need for complex detection adjustments and maintaining high detection reliability with standard criteria
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 results in a silicon nitride substrate with reduced color unevenness, enhancing the accuracy of foreign object and dust detection and maintaining high thermal conductivity, suitable for applications like power modules in electric vehicles and industrial motors.
Implementation Method 1
sintering the green body in a furnace
Implementation Method 2
nitriding the green body by heating it at a predetermined heating temperature
Implementation Method 3
temperature difference between the heating temperature and a temperature of the green body in the furnace is equal to or lower than 20°C
Data Source
Figure 1~2
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Figure 7~9
AI summary
Color unevenness generated on a surface of a silicon nitride substrate is reduced. A silicon nitride substrate formed by nitriding silicon containing in a sheet-shaped green body includes a first surface and a second surface opposite to the first surface. In this case, when color difference between a center and an edge of at least one surface of the first surface and the second surface is expressed to be "ΔE*ab", a relation "ΔE*ab ≤ 1.5" is established.