Multilayer Ceramic Substrate with Glass Softening Point Control
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Solution Overview
Problem
Existing multilayer ceramic substrates with surface layers having lower thermal expansion coefficients than the inner layers suffer from uneven sintering, leading to strain and crack formation, which compromises insulation reliability due to water penetration and reduced flexural strength, especially in thinner designs.
Innovation Solution
A multilayer ceramic substrate with a laminated structure featuring surface and inner layers where the first layer has a lower thermal expansion coefficient than the second layer, with both layers containing glasses that have 40% or more by weight of MO (Ca, Mg, Sr, or Ba) and a softening point difference of 60°C or lower, generating compressive stress for enhanced flexural strength while inhibiting crack formation and water penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface layer portions with lower thermal expansion coefficients than the inner layer portion are disposed to improve flexural strength, then the multilayer ceramic substrate can have smaller thickness, but the surface layer portions have uneven sintered state to generate strain and form cracks
Solution Approach 1:
The invention changes the chemical composition parameters of the glass materials in the surface and inner layers. Specifically, the glass in the surface layer contains 30-70 wt% SiO2, 5-40 wt% Al2O3, and 5-30 wt% B2O3, while the glass in the inner layer contains 20-60 wt% SiO2, 10-40 wt% Al2O3, and 5-20 wt% B2O3. These parameter adjustments ensure that the softening point difference between layers is 50°C or less, preventing uneven sintering and crack formation while maintaining the thermal expansion coefficient difference needed for flexural strength.
Solution Approach 2:
The invention uses composite glass materials with specific compositions in both surface and inner layers. The glass compounds are combined with ceramic powders (such as Al2O3, SiO2, B2O3) to create composite ceramic-glass layers. This composite structure allows simultaneous optimization of thermal expansion coefficients, sintering characteristics, and mechanical strength, resolving the contradiction between flexural strength enhancement and crack prevention.
2Ease of manufacture
If the difference in softening points between glasses in surface and inner layers is large, then sintering can proceed, but strain stress forms cracks in the surface layer
Solution Approach 1:
The invention precisely controls the chemical composition parameters of the glass materials to regulate their softening points. The glass in the surface layer is designed with 30-70 wt% SiO2, 5-40 wt% Al2O3, and 5-30 wt% B2O3, while the inner layer glass contains 20-60 wt% SiO2, 10-40 wt% Al2O3, and 5-20 wt% B2O3. This parameter optimization ensures the softening point difference is 50°C or less, allowing smooth sintering without excessive strain stress that would cause cracking.
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 solution effectively inhibits crack formation in the surface layers, enhances flexural strength, and improves insulation reliability by reducing strain stress and preventing water penetration, while maintaining sufficient thermal expansion coefficient differences to prevent delamination and electrode diffusion.
Implementation Method 1
the thermal expansion coefficient of the first layer is lower than the thermal expansion coefficient of the second layer... the difference in the thermal expansion coefficients between the surface layer portions and the inner layer portion is 1.0 ppmK−1 or more... generates compressive stress in both outermost layers in a cooling process after firing
Implementation Method 2
the difference in softening points between the first glass contained in the first layer and the second glass contained in the second layer is 60° C. or lower... the use of the surface layer portions each having a lower thermal expansion coefficient than the inner layer portion generates compressive stress in both outermost layers in a cooling process after firing
Data Source
AI summary
A multilayer ceramic substrate that includes a laminated structure including a surface layer portion located on a surface of the laminated structure and an inner layer portion located on the inner side of the laminated structure, the surface layer portion including a first layer adjacent to the inner layer portion, the inner layer portion including a second layer adjacent to the first layer. The thermal expansion coefficient of the first layer is lower than the thermal expansion coefficient of the second layer, a first glass contained in the first layer and a second glass contained in the second layer each contain 40% or more by weight MO (where M represents at least one selected from the group consisting of Ca, Mg, Sr, and Ba), and the difference in softening points between the first glass and the second glass is 60° C. or lower.