Large Silicon Nitride Substrate Density Uniformity
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Solution Overview
Problem
Existing technologies face challenges in producing large-sized silicon nitride sintered substrates with high mechanical strength, low dielectric constant, high air tightness, and high productivity, while maintaining uniformity in density and void fraction across the substrate.
Innovation Solution
A silicon nitride sintered substrate with a main surface larger than a square with a side length of 120 mm, featuring a density ratio of 0.98 or higher between the central and end areas, void fractions of 1.80% or lower in the central area and 1.00% or lower in the end area, and a partial discharge inception voltage of 4.0 kV or higher, produced using a method involving the mixing of Si3N4 powder, Mg compound powder, and rare earth element compound powder, followed by forming greensheets, stacking with boron nitride powder layers, and sintering in a nitrogen atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large-sized silicon nitride sintered substrate is produced, then productivity increases and more electronic circuits can be mounted, but maintaining uniform density and low void fraction across the entire substrate becomes difficult
Solution Approach 1:
The patent applies local quality by specifying different void fraction requirements for different regions of the substrate: the central area is allowed to have a void fraction of 1.80% or lower, while the end area requires a stricter void fraction of 1.00% or lower. This regional differentiation allows the entire large substrate to meet quality standards despite size-related manufacturing challenges.
Solution Approach 2:
The patent changes the parameter specifications based on location within the substrate. By setting different density ratios (dc/de ≥ 0.98) and void fraction thresholds for central versus end areas, the invention accommodates the natural variations that occur in large substrates while maintaining overall quality through controlled parameter gradients.
2Productivity
If the substrate size is increased to produce more electronic circuits, then the number of circuits per substrate increases, but the mechanical strength and insulation reliability may be compromised
Solution Approach 1:
The patent ensures insulation reliability by implementing location-specific quality control: the end area, which is more prone to defects in large substrates, is required to have a void fraction of 1.00% or lower, while the central area allows up to 1.80%. This targeted approach maintains high reliability across the entire large substrate.
Solution Approach 2:
The substrate is made from silicon nitride sintered material with specific compositional control, achieving a balance between size, mechanical strength, and insulation reliability through material science rather than simple geometric scaling.
3Productivity
If the substrate size is increased, then more electronic circuits can be produced on one substrate, but the density uniformity between central and end areas becomes harder to maintain
Solution Approach 1:
The patent addresses density uniformity by implementing local quality standards: the central area density (dc) and end area density (de) must satisfy dc/de ≥ 0.98, meaning the end area density must be at least 98% of the central area density. Combined with location-specific void fraction controls, this ensures compositional stability across the large substrate.
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 solution provides a large-sized silicon nitride sintered substrate with high insulation reliability, high breakdown voltage, and uniform density and void fraction distribution, enhancing productivity and reducing production costs.
Implementation Method 1
step (d) of locating the stacked assembly in a sintering furnace and sintering the stacked assembly. In the step (c), the boron nitride powder layer has a thickness of 3 μm or greater and 20 μm or less. The step (d) includes step (d1) of removing carbon from the greensheets while maintaining an atmosphere temperature of 900°C or higher and 1300°C or lower in a vacuum atmosphere of 80 Pa of lower; and step (d2) of, after the step (d1), sintering the greensheets at an atmosphere temperature of 1600°C or higher and 2000°C or lower in a nitrogen atmosphere.
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3~5A
AI summary
Provided is a large-sized silicon nitride sintered substrate and a method for producing the same. The silicon nitride sintered substrate has a main surface 101a of a shape larger than a square having a side of a length of 120 mm. A ratio dc/de of the density dc of the central area and the density de of the end area of the main surface 101a is 0.98 or higher. The void fraction vc of the central area of the main surface 101a is 1.80% or lower, and the void fraction ve of the end area is 1.00% or lower. It is preferred that the density dc of the central area is 3.120 g/cm3 or higher, the density de of the end area is 3.160 g/cm3 or higher, and a ratio ve/vc of the void fraction vc of the central area and the void fraction ve of the end area is 0.50 or higher.