Silicon Nitride Ceramic Substrate Processing for Net-Size Thermal Conduction
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Solution Overview
Problem
Existing methods for preparing silicon nitride ceramic substrates face challenges such as blistering, cracking, deformation, and uneven thickness, making it difficult to achieve uniformity and high thermal conductivity, especially for thin substrates required in high-end semiconductor devices.
Innovation Solution
A method involving vacuum degassing, tape casting under a nitrogen atmosphere, cold isostatic pressing, and gas pressure sintering in a nitrogen atmosphere to control thickness, flatness, and surface quality, using additives like rare earth oxides and alkaline earth metal oxides to enhance mechanical and thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tape casting is used to prepare thin silicon nitride ceramic substrates, then production efficiency is improved and cost is reduced, but the prepared cast films are prone to blistering, cracking, deformation, and uneven thickness
Solution Approach 1:
The patent applies preliminary action by conducting vacuum degassing (−0.1 to −10 kPa for 6-24 h) before tape casting to remove air bubbles from the slurry, and by optimizing the slurry composition with specific additives (dispersant 0.1-1.0 wt%, defoamer 0.1-0.5 wt%) to prevent blistering and cracking during the subsequent casting process. This preliminary treatment ensures the cast film achieves uniform thickness without defects.
2Ease of manufacture
If dry pressing is used to prepare ceramic substrates with thickness less than 0.5 mm, then it is difficult to achieve uniform thickness, but subsequent machining is required which increases complexity
Solution Approach 1:
The patent applies parameter changes by optimizing the slurry viscosity through controlled addition of dispersants (0.1-1.0 wt%) and defoamers (0.1-0.5 wt%), and by adjusting the vacuum degassing parameters (−0.1 to −10 kPa for 6-24 h). These parameter optimizations enable the tape casting process to directly produce substrates with uniform thickness of 0.2-0.8 mm, eliminating the need for subsequent machining.
3Manufacturing precision
If roll forming is used to eliminate uneven thickness, then the process becomes complicated and requires repetition, but the prepared substrate is still prone to blisters and uneven surfaces
Solution Approach 1:
The patent applies preliminary action by conducting thorough vacuum degassing (−0.1 to −10 kPa for 6-24 h) and optimizing slurry composition with dispersants and defoamers before tape casting. This preliminary treatment prevents the formation of blisters and surface unevenness during casting, eliminating the need for repeated roll forming processes and subsequent machining to achieve uniform thickness and smooth surfaces.
4Reliability
If conventional sintering is used, then thermal conductivity is improved, but deformation occurs during sintering and surface roughness increases
Solution Approach 1:
The patent applies pneumatic principles by conducting gas pressure sintering in a nitrogen atmosphere at controlled pressure (0.1-10 MPa) at temperatures of 1800-2000°C. The nitrogen pressure prevents deformation during sintering by counteracting internal stresses, while the controlled atmosphere prevents oxidation. This results in substrates with high thermal conductivity (>80 W·m⁻¹·K⁻¹) and smooth surfaces that meet copper cladding requirements without subsequent machining.
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 achieves high-thermal-conductivity silicon nitride ceramic substrates with uniform thickness, flatness, and smooth surfaces, eliminating the need for subsequent machining and ensuring high thermal conductivity for direct use in copper cladding.
Implementation Method 1
vacuum degassing at a vacuum degree of −0.1 kPa to −10 kPa
Implementation Method 2
subjecting the third green body to gas pressure sintering in a nitrogen atmosphere at 1,800° C. to 2,000° C.
Implementation Method 3
gas pressure sintering in a nitrogen atmosphere at 1,800° C. to 2,000° C.
Data Source
AI summary
A preparation method of a high-thermal-conductivity and net-size silicon nitride ceramic substrate includes the following steps: (1) mixing an original powder, a sintering aid, a dispersant, a defoamer, a binder, and a plasticizer in a protective atmosphere to allow vacuum degassing to obtain a mixed slurry; (2) subjecting the mixed slurry to tape casting and drying in a nitrogen atmosphere to obtain a first green body; (3) subjecting the first green body to shaping pretreatment to obtain a second green body; (4) subjecting the second green body to debonding at 500° C. to 900° C. to obtain a third green body; and (5) subjecting the third green body to gas pressure sintering in a nitrogen atmosphere at 1,800° C. to 2,000° C. to obtain the high-thermal-conductivity and net-size silicon nitride ceramic substrate.