Silicon Nitride Substrate Warpage Control
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Solution Overview
Problem
Existing silicon nitride substrates for power semiconductor modules face issues with warpage and surface roughness, leading to degraded adhesion properties and susceptibility to cracks or exfoliation under thermal stress, which existing techniques fail to adequately address.
Innovation Solution
A silicon nitride substrate with a degree of orientation on the surface and inside adjusted to specific ranges, containing magnesium and yttrium oxides, is manufactured using a process involving sintering and heat treatment to control warpage and surface roughness, ensuring strong adhesion with metal plates and resistance to thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sintering methods are used to manufacture silicon nitride substrates, then the substrate can be produced with basic structural integrity, but the warpage and surface roughness cannot be appropriately adjusted, leading to degraded adhesion properties
Solution Approach 1:
The patent applies parameter changes by precisely controlling the degree of orientation (fa) within 0.15≤fa<0.35 and substrate thickness within 0.05≤thickness<1.0mm. These parameter adjustments directly control warpage and surface roughness, enabling appropriate adhesion properties when bonded with metal circuit plates and heat sink plates.
Solution Approach 2:
The patent performs preliminary action by pre-adjusting the degree of orientation and thickness parameters during the manufacturing process. This preliminary control of structural parameters ensures that warpage and surface roughness are appropriately adjusted before bonding, preventing adhesion degradation that would occur with conventional methods.
2Strength
If the degree of orientation is increased to improve bending strength and fracture toughness, then mechanical strength is improved, but surface roughness may increase, degrading surface adhesion property
Solution Approach 1:
The patent resolves this contradiction by precisely controlling the degree of orientation parameter within the range 0.15≤fa<0.35. This optimized parameter range simultaneously achieves improved bending strength and fracture toughness while maintaining appropriate surface roughness for good adhesion properties, eliminating the need to choose between strength and surface quality.
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 substrate exhibits improved bending strength, fracture toughness, and reduced surface roughness, preventing cracks and exfoliation, thus enhancing the reliability of power semiconductor modules under thermal cycling.
Implementation Method 1
a sintered silicon nitride substrate
Implementation Method 2
a process involving sintering and heat treatment to control warpage and surface roughness
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A silicon nitride substrate having appropriately adjusted warpage and surface roughness can be obtained by mixing magnesium oxide of 3 to 4 wt% and at least one kind of rare-earth element oxide of 2 to 5 wt% with silicon nitride source material powder to form a sheet-molded body, sintering the sheet-molded body, and performing a heat treatment at a temperature of 1,550 to 1,700 degree C with a pressure of 0.5 to 6.0 kPa with a plurality of substrates being stacked. Also, a silicon nitride circuit board and a semiconductor module using the same are provided.