Ceramic Multilayer Substrate Insulator Layer Sintering Control
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Solution Overview
Problem
Ceramic multilayer substrates face challenges in maintaining high insulation resistance between wiring conductors in the stacking direction when the thickness of the ceramic insulator layer is decreased, particularly due to conductor diffusion and ion migration in wet environments.
Innovation Solution
The ceramic multilayer substrate incorporates a ceramic insulator layer with a specific structure, comprising a first layer interposed between second and third layers, where the sintering shrinkage start temperatures of the second and third layers are higher than the stop temperature of the first layer, functioning as constraining and diffusion-suppressing layers to prevent conductor component diffusion and ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the thickness of the ceramic insulator layer is decreased to achieve higher density wiring arrangements, then the wiring conductors can be arranged in higher density, but the insulation resistance between wiring conductors deteriorates due to conductor diffusion and ion migration
Solution Approach 1:
The ceramic insulator layer is segmented into multiple sub-layers (first ceramic sub-layer, second ceramic sub-layer, third ceramic sub-layer) with different sintering shrinkage characteristics. The first and third sub-layers have lower sintering shrinkage start temperatures than the second sub-layer, creating a layered structure that suppresses overall shrinkage while maintaining thin thickness for high conductor density.
Solution Approach 2:
Different regions of the ceramic insulator layer are assigned different material properties and sintering characteristics. The first and third sub-layers use ceramics with lower sintering shrinkage start temperatures (500-800°C) compared to the second sub-layer (800-1000°C), creating local variations in thermal and mechanical properties to control diffusion and migration behavior in specific zones.
2Productivity
If the thickness of the ceramic insulator layer is decreased, then more wiring conductors can be packed in the stacking direction, but conductor components diffuse more easily into the insulator layer
Solution Approach 1:
The second ceramic sub-layer acts as an intermediary barrier between the first and third sub-layers. This middle layer has higher sintering shrinkage start temperature and serves as a diffusion barrier that prevents conductor components from migrating between the lower-temperature sub-layers, while still allowing the overall structure to remain thin for high conductor density.
Solution Approach 2:
The ceramic insulator layer uses a composite structure of three different ceramic materials with varying sintering characteristics. Each sub-layer is composed of ceramics with different melt viscosities and sintering temperature ranges, creating a composite material system that simultaneously enables thin thickness for high density while suppressing conductor diffusion through the higher-temperature second sub-layer.
3Reliability
If the ceramic insulator layer is fired at high temperature to ensure proper sintering, then good electrical insulation is achieved, but sintering shrinkage causes deformation and distortion in the wiring conductors
Solution Approach 1:
The sintering process is divided into periodic temperature stages corresponding to the different sintering shrinkage start temperatures of the three sub-layers. The temperature is gradually increased through distinct phases: first heating the low-temperature sub-layers (500-800°C), then heating the high-temperature second sub-layer (800-1000°C), allowing controlled, staged shrinkage that prevents sudden deformation while maintaining electrical insulation.
Solution Approach 2:
The sintering temperature parameter is dynamically changed during the firing process to match the different thermal characteristics of the three sub-layers. By adjusting the temperature profile to first reach 500-800°C for the first and third sub-layers, then increasing to 800-1000°C for the second sub-layer, the process achieves proper sintering of all layers while controlling overall shrinkage to prevent wiring conductor deformation.
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
This configuration ensures high insulation resistance between wiring conductors even when the ceramic insulator layer thickness is reduced, effectively preventing conductor diffusion and ion migration, thus maintaining high performance in dense wiring arrangements.
Implementation Method 1
the sintering shrinkage start temperatures of the second layer alone and the third layer alone in a green sheet state are higher than or equal to the sintering shrinkage stop temperature of the first layer alone in a green sheet state
Data Source
AI summary
A ceramic multilayer substrate that includes a ceramic insulator layer, which includes a first layer, a second layer, and a third layer and in which the first layer is interposed between the second layer and the third layer, an inner pattern conductor, an outer pattern conductor, and outer electrodes. The ceramic insulator layer is interposed between the inner pattern conductor and the outer pattern conductor. The sintering shrinkage start temperatures of the second layer alone and the third layer alone in a green sheet state are higher than or equal to the sintering shrinkage stop temperature of the first layer alone in a green sheet state. The thickness of the ceramic insulator layer is 5.0 μm to 55.7 μm. The ratio of the total of the thickness of the second layer and the thickness of the third layer to the thickness of the first layer is 0.25 to 1.11.