Double-Layered Glass Ceramic Substrate Stress Management
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Solution Overview
Problem
Ceramic substrates face stress concentration and cracking issues during heat-cycle tests due to thermal expansion coefficient differences with mounting boards, and existing glass layer solutions suffer from degraded plating resistance and erosion from plating solutions.
Innovation Solution
A ceramic substrate with a double-layered glass structure, where the first glass sublayer has superior adhesion to the ceramic substrate and the second glass sublayer has enhanced plating resistance, is used to overlay the conductor, preventing stress concentration and erosion during heat-cycle tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a glass layer is formed to overlay the periphery of the land electrode to relax stress concentration, then adhesion between the glass layer and ceramic substrate is improved, but plating resistance is degraded and erosion from plating solution occurs
Solution Approach 1:
The glass layer is divided into two distinct sublayers: a first glass sublayer in contact with the ceramic substrate providing adhesion, and a second glass sublayer overlaying the first glass sublayer providing plating resistance. This segmentation allows each sublayer to be optimized for its specific function, resolving the contradiction between adhesion and plating resistance.
Solution Approach 2:
Different glass materials are used at different locations within the glass layer structure. The first glass sublayer uses a glass material optimized for adhesion to the ceramic substrate, while the second glass sublayer uses a glass material optimized for plating resistance. This local differentiation of material properties resolves the contradiction by providing the right material quality at the right location.
2Reliability
If the land electrode has a dimension substantially equal to that of the mounting land, then connection reliability is improved, but stress concentration occurs at the edge of the land electrode during heat-cycle test
Solution Approach 1:
The glass layer is formed beforehand to overlay the periphery of the land electrode, creating a cushioning effect that prevents stress concentration at the edges during subsequent heat-cycle testing. This prior protective measure resolves the contradiction by preventing the harmful stress concentration before it occurs.
Solution Approach 2:
The glass layer acts as an intermediary substance between the land electrode and the external environment, mediating the stress distribution during thermal cycling. This intermediary layer protects the land electrode edge from direct stress concentration while maintaining connection reliability.
3Reliability
If glass material incorporated in ceramic layer is selected for the glass layer to enhance adhesion, then adhesion is improved, but plating resistance is degraded
Solution Approach 1:
The glass layer is segmented into two sublayers with different material compositions. The first glass sublayer uses glass material incorporated in the ceramic layer for enhanced adhesion, while the second glass sublayer uses glass material with superior plating resistance. This segmentation resolves the contradiction by separating the adhesion function from the plating resistance function into different material layers.
Solution Approach 2:
The glass layer is constructed as a composite structure with two different glass materials. The first glass sublayer comprises glass material incorporated in the ceramic layer for adhesion, and the second glass sublayer comprises glass material with plating resistance. This composite material approach allows the system to simultaneously achieve both adhesion and plating resistance properties that cannot be obtained with a single material.
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 double-layered glass structure effectively suppresses stress concentration and prevents cracking, while maintaining superior adhesion and plating resistance, resulting in a high-reliability ceramic substrate that withstands heat-cycle conditions and plating processes.
Implementation Method 1
the first glass sublayer made of a first glass material and extending from a portion of the conductor to the first main surface of the main body of the ceramic substrate... the first glass material having a greater adhesion to the main body of the ceramic substrate
Implementation Method 2
the glass layer partially overlaying the conductor has a superior adhesion to the main body of the ceramic substrate and a superior plating resistance... effectively suppresses stress concentration and prevents cracking
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3~4
AI summary
A high-reliability ceramic substrate that does not cause a heat-cycle-induced stress concentration on a conductor and that include a glass layer partially overlaying the conductor, the glass layer having satisfactory adhesion to the main body of the ceramic substrate and having satisfactory plating resistance is provided. An electronic apparatus and a method for producing the ceramic substrate are provided. The glass layer is a glass layer 13 which is arranged to extend from part of the conductor formed on a first main surface of the main body of the ceramic substrate to the first main surface of the main body of the ceramic substrate and which has a double-layered structure including a first glass sublayer 11 composed of a first glass material; and a second glass sublayer 12 formed on the first glass sublayer and composed of a second glass material different from the second glass material constituting the first glass sublayer, the first glass material having more satisfactory adhesion to the main body of the ceramic substrate than the second glass material, and the first glass material having more satisfactory plating resistance than the first glass material.