Ceramic Substrate Surface Zoning for Conductor and Resin Bonding
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Solution Overview
Problem
Ceramic substrates used in power modules require improved reliability and heat radiation characteristics, with existing solutions not adequately addressing the need for adjustable adhesiveness and joinability for various applications.
Innovation Solution
A ceramic substrate with distinct surface roughness regions, containing silicon nitride and a metal oxide with Y and Mg as constituent elements, allowing for adjustable adhesiveness and joinability through etching, enabling firm conductor attachment and enhanced resin bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the ceramic substrate has a uniform surface roughness, then the manufacturing process is simple, but the adhesiveness and joinability cannot be adjusted for different members
Solution Approach 1:
The ceramic substrate is designed with multiple regions having different surface roughness values. Specifically, a first region has a surface roughness Ra1 of 0.01 to 0.5 μm for optimal conductor portion joinability, while a second region has a surface roughness Ra2 of 0.1 to 5.0 μm for optimal resin adhesiveness. This local differentiation allows each region to be optimized for its specific function without compromising the other.
2Strength
If the surface roughness is increased to improve resin adhesiveness, then the bond strength increases, but the joinability of conductor portions deteriorates
Solution Approach 1:
The substrate surface is divided into functional zones: the first region with Ra1 = 0.01 to 0.5 μm provides smooth surfaces ideal for conductor portion bonding, while the second region with Ra2 = 0.1 to 5.0 μm provides rough surfaces ideal for resin adhesion. This spatial separation resolves the conflict between resin adhesiveness and conductor joinability.
3Strength
If the surface roughness is decreased to improve conductor portion joinability, then the bonding strength increases, but the resin adhesiveness deteriorates
Solution Approach 1:
By creating distinct surface regions with optimized roughness values, the first region (Ra1 = 0.01 to 0.5 μm) maximizes conductor portion joinability through smooth surfaces, while the second region (Ra2 = 0.1 to 5.0 μm) maximizes resin adhesiveness through increased surface area and mechanical interlocking.
4Manufacturing precision
If the ceramic substrate uses a single material composition, then the manufacturing process is simple, but the surface roughness cannot be precisely controlled for different applications
Solution Approach 1:
The substrate employs a composite material system consisting of silicon nitride particles (30-90 mass%), binder (5-40 mass%), and sintering aid (5-40 mass%). By adjusting the ratios of these components, particularly the sintering aid composition containing Y2O3, MgO, and SiO2, the surface roughness can be precisely controlled to achieve different Ra values in different regions after etching treatment.
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 ceramic substrate achieves improved reliability by allowing for precise adjustment of surface roughness, enhancing adhesiveness and joinability, which is critical for power modules, particularly in high-reliability applications like automotive and industrial equipment.
Implementation Method 1
adjustable adhesiveness and joinability through etching
Implementation Method 2
the ceramic substrates are required to have satisfactory heat radiation characteristics
Implementation Method 3
the adhesiveness of the resin layer is improved
Data Source
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AI summary
Provided are a ceramic substrate and a circuit board having excellent reliability as components. The ceramic substrate has a first region and a second region having different surface roughness in a main surface. The ratio of a surface roughness Ra2 in the second region to a surface roughness Ra1 in the first region is 1.5 or more. The circuit board includes the ceramic substrate and a conductor portion joined to at least a part of the first region.