Ceramic Substrate Convex Portions for Flatness
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Solution Overview
Problem
There is a growing demand for circuit substrates with improved flatness to reduce residual thermal strain or stress, which existing methods have not adequately addressed.
Innovation Solution
A ceramic substrate with convex portions formed at specific locations, where the maximum projection amount is controlled relative to the diagonal length, is used in conjunction with metal layers on both surfaces, and a manufacturing method involving rapid cooling and precise cutting techniques to achieve reduced thermal strain and enhanced flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sintering methods are used, then the sintering process is simple, but residual thermal strain and stress remain high resulting in poor flatness
Solution Approach 1:
The sintering process is segmented into multiple distinct stages: heating stage, holding stage, and cooling stage, each with specific temperature ranges and time durations. This segmentation allows precise control over thermal history to minimize residual stress while maintaining manufacturing feasibility
Solution Approach 2:
Specific sintering parameters are optimized including heating rate (10-100°C/hour), holding temperature (1600-1800°C), holding time (1-24 hours), and cooling rate (10-100°C/hour). These parameter changes enable control over thermal strain accumulation to achieve flatness within 10μm while keeping the process industrially viable
2Manufacturing precision
If rapid cooling is applied to reduce thermal strain, then flatness improves, but the risk of thermal shock increases
Solution Approach 1:
The cooling rate is made dynamic rather than constant, starting faster at high temperatures and gradually slowing down as temperature decreases. This dynamic adjustment allows rapid removal of thermal strain initially while preventing thermal shock at lower temperatures where the material becomes more brittle
Solution Approach 2:
The cooling process is divided into periodic stages with different cooling rates: rapid cooling phase (10-100°C/hour) followed by slower cooling phase (1-10°C/hour). This periodic action enables controlled stress relief while maintaining structural integrity throughout the cooling cycle
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 approach results in circuit substrates with significantly reduced residual thermal strain and stress, improving flatness and joining properties, while maintaining high thermal conductivity and insulating properties.
Implementation Method 1
a sintering step of disposing the individual green sheet in a firing chamber, heating an inside of the firing chamber until a temperature in the firing chamber reaches at least equal to or higher than 1600°C, then, cooling the inside of the firing chamber, and sintering the individual green sheet
Data Source
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AI summary
A ceramic substrate of the present invention is a ceramic substrate having a rectangular shape in a plan view, in which, at a location deviating from an intersection formed by a pair of diagonal lines of the ceramic substrate, at least one convex portion that is convex toward one side or the other side in a sheet thickness direction is formed, and a value obtained by dividing a maximum projection amount of the at least one convex portion by a length of the diagonal line of the ceramic substrate is equal to or less than 2 µm/mm.