Multilayer Ceramic Substrate Fresnoite Grain Boundaries
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Solution Overview
Problem
Multilayer ceramic substrates with Ba-Al-Si based oxide ceramic as the base material layer and alumina powder as the constrained layer face challenges in achieving desirable substrate strength due to the constrained layer being thinner than the base material layer, leading to lower abundance of celsian in the base material layer.
Innovation Solution
Incorporating a Ti component into the base material layer to deposit fresnoite, a fine crystal phase, which increases crystal grain boundaries and enhances substrate strength, and also including fresnoite in the constrained layer to further improve strength, fracture toughness, and electrode peel strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the constrained layer is made thinner to enable material flow for densification, then densification is improved, but the constraint force to prevent shrinkage becomes insufficient
Solution Approach 1:
The patent changes the material composition parameters of the constrained layer by incorporating a glass component that undergoes phase transition at specific temperatures. The glass softens at a temperature higher than the shrinkage onset temperature but lower than the completion sintering temperature, enabling the constrained layer to transition from a rigid constraint structure to a flowable densification medium at the appropriate stage of sintering.
Solution Approach 2:
The patent utilizes the phase transition of the glass component in the constrained layer. The glass remains rigid at lower temperatures to provide constraint force during shrinkage, then softens at elevated temperatures to enable material flow and densification, effectively using thermal phase transition to resolve the contradiction between maintaining constraint and enabling densification.
2Ease of manufacture
If a non-glass based low-temperature sintering ceramic material is used to reduce cost, then manufacturing cost is reduced, but substrate strength becomes insufficient
Solution Approach 1:
The patent creates a composite material system combining non-glass based low-temperature sintering ceramic material (Ba-Al-Si based oxide ceramic) with a specifically formulated glass component in the constrained layer. This composite approach allows the base material layer to maintain low cost while the glass-containing constrained layer provides the necessary structural support and strength, resolving the contradiction between cost reduction and strength maintenance.
Solution Approach 2:
The glass component in the constrained layer acts as an intermediary that transfers and distributes mechanical stress, enhancing the overall substrate strength. The glass phase serves as a mediator between the non-glass based ceramic materials, providing toughness and strength to the composite structure while allowing the base material to remain cost-effective.
3Manufacturing precision
If the constrained layer is made thinner than the base material layer, then material flow for densification is enabled, but substrate strength becomes insufficient
Solution Approach 1:
The patent changes the thermal and mechanical parameters of the constrained layer by incorporating glass with specific softening characteristics. The glass content and composition are optimized so that the constrained layer maintains adequate thickness for strength while still allowing sufficient material flow for densification through the glass softening mechanism at elevated temperatures.
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 addition of fresnoite in both the base and constrained layers increases the substrate's strength, fracture toughness, and electrode peel strength by enhancing crystal grain boundaries and sinterability, addressing the limitations of previous technologies.
Implementation Method 1
Incorporating a Ti component into the base material layer to deposit fresnoite, a fine crystal phase, which increases crystal grain boundaries and enhances substrate strength
Implementation Method 2
a powder is used which fails to soften or flow substantially at the shrinkage onset temperature of a ceramic raw material powder (the first powder) in a base material layer (the first sheet layer), but can soften or flow for the densification of the constrained layer at the completion of sintering
Implementation Method 3
in a firing step, the first powder is sintered
Data Source
AI summary
In order to enable non-shrinkage firing, the strength of a multilayer ceramic substrate is increased which is obtained by a method in which alternately stacking a base material layer and a constrained layer which is not sintered at the sintering temperature for the base material layer, and in a firing step, allowing the material of the base material layer to flow into the constrained layer while subjecting the base material layer to sintering, thereby achieving the densification of the constrained layer. The base material layer and the constrained layer each include celsian (BaAl2Si2O8), and the abundance of celsian is lower in the base material layer than in the constrained layer. In order to increase the strength of the base material layer, the addition of a Ti component, rather than an increased content of Al component which interferes with sintering of the base material layer, causes fresnoite (Ba2TiSi2O8) to be deposited in the base material layers. The presence of fresnoite in the base material layers increases crystal grain boundaries in the base material layers, and thus allows the development of cracking to be prevented, thereby allowing the strength of the multilayer ceramic substrate to be improved.