Silicon Nitride Substrate Lamination for Stronger Interlayer Bonding
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Solution Overview
Problem
In the production of silicon nitride substrates, poor adhesion between laminated green sheets leads to reduced thermal conductivity and bending strength due to defects such as pores and delamination, which are exacerbated by oxidation during sintering.
Innovation Solution
A silicon nitride substrate production method involving the alternately arranged major and intermediate layers with controlled color differences, achieved through precise lamination and sintering conditions, ensures adequate adhesion and minimizes defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple green sheets are laminated to produce a thick silicon nitride substrate, then the substrate thickness and heat dissipation capability are improved, but the adhesion between layers deteriorates leading to pores and delamination
Solution Approach 1:
The invention changes the chemical composition parameters of the green sheet by controlling the organic additive content (0.1-5 mass%) and its distribution. This parameter control ensures proper adhesion between laminated layers while maintaining the desired substrate thickness. The organic additive decomposes during sintering to create bonding between layers without excessive porosity.
Solution Approach 2:
The invention creates a composite structure by laminating multiple green sheets with controlled organic additive content. Each layer acts as a composite material where the inorganic powder matrix is reinforced by the organic additive network, which after decomposition creates a controlled pore structure that facilitates interlayer bonding while maintaining overall structural integrity.
2Strength
If green sheets are closely laminated to improve adhesion, then the bending strength is improved, but the manufacturing complexity increases
Solution Approach 1:
The invention simplifies manufacturing by controlling the organic additive concentration parameter within a specific range (0.1-5 mass%). This single parameter control achieves both good adhesion and high bending strength without requiring complex lamination procedures, pressure control, or multiple processing steps.
3Reliability
If the organic additive content in green sheets is increased to improve adhesion, then the bonding between layers is improved, but the porosity and oxidation resistance deteriorate
Solution Approach 1:
The invention optimizes the organic additive content parameter to a specific range (0.1-5 mass%) that balances adhesion and oxidation resistance. This precise parameter control ensures sufficient organic material for interlayer bonding while limiting excessive decomposition that would create pores and reduce oxidation resistance.
Solution Approach 2:
The invention applies local quality by having the organic additive concentrated at the interfaces between laminated layers where it is needed for bonding, rather than uniformly distributed throughout the bulk material. This localized presence provides adhesion where required while minimizing overall porosity and oxidation susceptibility.
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
The method enhances thermal conductivity and bending strength by suppressing defects, maintaining optimal adhesion and reducing oxidation, thereby improving the mechanical and thermal properties of the silicon nitride substrate.
Implementation Method 1
overlaying the multiple green sheets at a temperature of not less than 60 °C under a pressure of not less than 0.1 MPa
Implementation Method 2
overlaying the multiple green sheets at a temperature of not less than 60 °C under a pressure of not less than 0.1 MPa
Implementation Method 3
heat-treating the laminated body at a temperature of not more than 1,000 °C
Implementation Method 4
heat-treating the laminated body at a temperature of not more than 1,000 °C
Implementation Method 5
heating the dewaxed body at a temperature of not less than 1,600 °C and not more than 2,000 °C
Implementation Method 6
A silicon nitride substrate production method involving the alternately arranged major and intermediate layers with controlled color differences, achieved through precise lamination and sintering conditions, ensures adequate adhesion and minimizes defects
Data Source
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AI summary
There are provided a silicon nitride substrate and a method for producing a silicon nitride substrate produced by favorably laminating green sheets. A silicon nitride substrate according to an embodiment includes a major layer and an intermediate layer as observed in dark-field with an optical microscope in a cross section, in which the intermediate layer is darker than the major layer. A color difference between the major layer and the intermediate layer is not less than 0.1. m+1 of the major layers and m of the intermediate layers are alternately arranged in a thickness direction. A color difference between an nth major layer and an nth intermediate layer from one surface (n being an integer) is taken as CDna. A color difference between a (n+1)th major layer and the nth intermediate layer is taken as CDnb. In such a case, a first condition and a second condition are satisfied for all values of n from 1 to m. The first condition is when there is a continuous region having a length of not less than 100 µm in a first direction in which 0.1 ≤ CDna ≤ 1.4; and the first direction is parallel to the cross section and perpendicular to the thickness direction. The second condition is when there is a continuous region having a length of not less than 100 µm in the first direction in which 0.1 ≤ CDnb ≤ 1.4.