Silicon Nitride Ceramic Substrate with Rare Earth Silicate Grain Boundaries
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Solution Overview
Problem
Ceramic substrates used in electronic devices face challenges in achieving high thermal conductivity and mechanical strength while maintaining a thin profile, which is essential for efficient heat dissipation and mechanical integrity.
Innovation Solution
A ceramic substrate comprising a silicon nitride crystal phase with magnesium silicate and rare earth silicate phases in the grain boundaries, enhancing thermal conductivity and mechanical strength through improved sintering properties and heat transfer pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a silicon nitride sintered body is used as an insulating substrate, then mechanical strength and thermal conductivity are improved, but achieving high thermal conductivity while maintaining a thin profile is difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the grain boundary phase by introducing specific rare-earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, or Lu) in controlled amounts (0.01-5 wt% of rare-earth oxide). This compositional parameter change modifies the thermal transport properties of the grain boundary phase, enabling high thermal conductivity even in thin substrate configurations.
Solution Approach 2:
The patent creates a composite microstructure consisting of silicon nitride crystal grains surrounded by a grain boundary phase containing rare-earth silicates and magnesium silicate. This composite structure at the micro-scale allows the material to achieve superior thermal conductivity and mechanical strength properties that neither component could achieve alone, resolving the contradiction between thin profile and high thermal conductivity.
2Ease of manufacture
If conventional sintering aids are used in silicon nitride, then sintering is facilitated, but thermal conductivity and mechanical strength are limited
Solution Approach 1:
The patent fundamentally changes the sintering aid composition by replacing conventional oxides with rare-earth silicates and magnesium silicate in specific proportions. This parameter change in the grain boundary phase composition enables both easy sintering processability and high thermal conductivity, as the rare-earth silicates facilitate grain boundary bonding while maintaining low thermal resistance.
Solution Approach 2:
The patent develops a composite grain boundary phase combining rare-earth silicates and magnesium silicate, which creates a synergistic effect where the rare-earth components enhance sintering activity and the magnesium silicate provides structural stability. This composite approach overcomes the limitations of conventional single-component sintering aids.
3Length of moving object
If the substrate is made thinner for compact devices, then device size is reduced, but mechanical strength and thermal conductivity decrease
Solution Approach 1:
The patent changes the chemical composition of the grain boundary phase to include specific rare-earth elements and magnesium silicate in optimized ratios. This compositional parameter change enhances the bonding strength at grain boundaries, providing the mechanical strength necessary to maintain structural integrity even when the substrate thickness is reduced for compact device applications.
4Ease of manufacture
If conventional grain boundary phases are used, then sintering is achieved, but thermal resistance at grain boundaries is high
Solution Approach 1:
The patent changes the chemical composition of the grain boundary phase by introducing rare-earth silicates and magnesium silicate in specific proportions. This parameter change reduces thermal resistance at grain boundaries by creating a more thermally conductive pathway between silicon nitride grains, while still maintaining adequate sintering capability through the rare-earth components.
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 achieves thermal conductivity of 70 W/(m-K) or more and bending strength of 700 MPa or more, effectively reducing thermal resistance and enhancing heat dissipation properties in electronic devices.
Implementation Method 1
The silicon nitride sintered body has a relatively large mechanical strength and thermal conductivity and hence is used as the insulating substrate... the electronic components mounted on the insulating substrate are thermally connected to a heat dissipator formed of a metal through the insulating substrate and the like so as to dissipate heat from the electronic components through the heat dissipator to the outside
Implementation Method 2
a ceramic substrate comprising a silicon nitride crystal phase and grain boundaries between the silicon nitride crystals, the grain boundaries having a rare earth silicate phase and a magnesium silicate phase... a high thermal conductive silicon nitride sintered body is known containing: 2.0 to 17.5% by weight of a rare earth element in terms of the amount of an oxide thereof; 0.3 to 3.0% by weight of Mg in terms of the amount of an oxide thereof, comprising a silicon nitride crystal and a grain boundary phase
Data Source
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AI summary
There are provided a ceramic substrate and so on including: a silicon nitride crystal phase containing a plurality of silicon nitride crystals, and grain boundaries between the silicon nitride crystals; and a silicate phase containing magnesium silicate crystals and rare earth silicate crystals, respective maximum particle sizes of the magnesium silicate crystals and the rare earth silicate crystals being smaller than that of the silicon nitride crystals, the silicate phase being positioned in the grain boundaries.