SiC Composite Substrate Interface Structure Against Machining Cracks
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Solution Overview
Problem
Conventional SiC composite substrates experience delamination, breaking, and cracking due to residual stress during machining processes like grinding and polishing, which limits their reliability and durability.
Innovation Solution
A SiC composite substrate is designed with a biaxially-oriented SiC layer oriented in both the c-axis and a-axis directions, combined with a SiC polycrystalline layer, featuring a joint interface with a predetermined uneven shape of 1 to 200 μm, enhancing joint strength and reducing the likelihood of delamination and cracking during machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional SiC composite substrate is used with a flat joint interface, then the manufacturing process is simple, but the substrate experiences delamination, breaking, and cracking during machining due to residual stress
Solution Approach 1:
The joint interface is designed with an uneven shape featuring protrusions and recesses, deviating from the conventional flat symmetric interface. This asymmetric geometry creates mechanical interlocking between the first and second SiC layers, preventing delamination and cracking during machining while managing residual stress.
Solution Approach 2:
The joint interface incorporates curved surfaces and rounded transitions between protrusions and recesses, eliminating sharp corners that would concentrate stress. The curved geometry distributes mechanical stresses evenly across the interface, preventing crack initiation and propagation during machining operations.
2Strength
If the joint interface has a large amount of unevenness to prevent delamination, then joint strength improves, but machining difficulty increases and processing time extends
Solution Approach 1:
The unevenness amount is optimized within a specific range (1-200 μm) to balance joint strength and machinability. This parameter optimization ensures sufficient mechanical interlocking and stress distribution while avoiding excessive complexity that would hinder machining efficiency.
Solution Approach 2:
The uneven shape is concentrated at the joint interface region specifically, while other areas of the substrate maintain smooth surfaces. This localized complexity provides the necessary interlocking strength at the critical joint area without unnecessarily complicating the overall substrate geometry or machining operations.
3Reliability
If the unevenness amount is too small (less than 1 μm), then machining is easier, but the joint interface cannot effectively prevent delamination and cracking under residual stress
Solution Approach 1:
The uneven shape is pre-formed at the joint interface before final machining operations. This preliminary structural preparation ensures that the mechanical interlocking and stress distribution features are already in place, preventing delamination and cracking during subsequent machining while maintaining overall manufacturing precision.
Data Source
AI summary
Provided is a SiC composite substrate including a biaxially-oriented SiC layer in which SiC is oriented in both a c-axis direction and an a-axis direction, and a SiC polycrystalline layer provided on one surface of the biaxially-oriented SiC layer. A joint interface of the biaxially-oriented SiC layer and the SiC polycrystalline layer has an uneven shape, which has an amount of unevenness of 1 to 200 μm.