Silicon Nitride Substrate Crack Prevention via Slurry Control
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Solution Overview
Problem
Conventional methods for manufacturing silicon nitride substrates face challenges in achieving high density and high thermal conductivity while avoiding molding cracks and degreasing cracks, particularly when using silicon nitride powders with small specific surface areas or those that are difficult to sinter.
Innovation Solution
A silicon nitride substrate manufacturing method is developed, where the oxygen content of the silicon nitride powder is set to 2.0 mass% or less, the specific surface area is between 3 to 11 m²/g, and the additive ratio of sintering additives is 4 to 15 mol%, with a water content ratio of 0.03 to 3 mass% in the organic solvent, optimizing the sintering process to prevent cracks and enhance thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If doctor blade molding is used for high mass productivity, then manufacturing efficiency is improved, but molding cracks and degreasing cracks are easily generated due to shrinkage stress during drying
Solution Approach 1:
The invention changes the chemical composition parameters of the slurry by adding specific additives (organic acid, alcohol, and water in controlled ratios) to modify the drying characteristics and reduce shrinkage stress, enabling crack-free formation bodies to be produced via doctor blade molding with high productivity
2Reliability
If a large number of binders are added to suppress molding cracks, then molding integrity is improved, but degreasing becomes difficult and degreasing cracks occur
Solution Approach 1:
The invention introduces organic acid and alcohol as intermediary substances that facilitate the removal of binders during degreasing, acting as mediators between the binder and the degreasing process to enable easy removal while maintaining molding integrity
Solution Approach 2:
The invention changes the chemical parameters by controlling the ratio of organic acid, alcohol, and water in the slurry to optimize binder removal characteristics, making degreasing easier while preventing degreasing cracks
3Reliability
If silicon nitride powder with small specific surface area is used to prevent molding cracks, then molding reliability is improved, but sintering performance is degraded and high density cannot be achieved
Solution Approach 1:
The invention changes the chemical composition parameters of the slurry by adding organic acid, alcohol, and water to improve the sintering performance of fine silicon nitride powder, enabling high density sintered bodies to be obtained while using powder with small specific surface area for reliable molding
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 enables the production of high-density, high-thermal-conductivity silicon nitride substrates without molding or degreasing cracks, improving sintering performance and thermal radiation capabilities.
Implementation Method 1
the water content ratio of the organic solvent is set to 0.03 to 3 mass%, so that the surface of the silicon nitride powder is oxidized at the time of mixing to increase the amount of oxygen in the silicon nitride powder
Implementation Method 2
followed by sintering to obtain a silicon nitride substrate
Data Source
Figure 1
AI summary
Provided is a manufacturing method with which a high thermal conductivity silicon nitride substrate having excellent sintering performance can be manufactured without the occurrence of a molding crack or degreasing crack, as well as to provide a silicon nitride substrate, and a silicon nitride circuit board and a semiconductor module using said silicon nitride substrate. In this silicon nitride substrate manufacturing method, in which a slurry is produced by mixing a silicon nitride powder, a sintering additive powder, and a binder in an organic solvent which is a dispersion medium, and the slurry is formed into a sheet, followed by degreasing and sintering, the oxygen content of the silicon nitride powder is 2.0 mass% or less and the specific surface area of the same is 3 to 11 m2/g, the additive ratio of the sintering additive powder is 4 to 15 mol%, and the water content ratio of the organic solvent is 0.03 to 3 mass%.