Chamfered Corners in Component-Built Wiring Boards
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Solution Overview
Problem
Conventional component-built-in wiring boards face challenges in reducing stress concentration at corners, leading to defects like cracks and air bubbles in the resin filler, which impairs reliability and yield due to insufficient stress dispersion.
Innovation Solution
The component-built-in wiring board design features a core material with a housing portion and a component, where the inner and outer chamfered portions at the corners are strategically aligned to separate stress concentration points, ensuring the chamfer length of the outer portion is greater than the gap width, effectively dispersing stress and preventing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If corners of the housing portion and capacitor are rounded in an arc-like form to disperse stress concentration, then stress concentration is reduced to some extent, but the radius of curvature must be increased excessively which reduces the capacitance value of the capacitor
Solution Approach 1:
The patent applies curvature by forming arc-like rounded portions at the corners of the housing portion and capacitor, but optimizes the radius of curvature to be 0.05 to 0.2 times the gap width, achieving stress dispersion without excessive chamfering that would reduce capacitance value
Solution Approach 2:
The patent changes the geometric parameters by specifying precise dimensional relationships: the radius of curvature is set as a proportion (0.05 to 0.2 times) of the gap width, and the chamfer length is set as a proportion (0.5 to 2.0 times) of the gap width, optimizing both stress reduction and capacitance preservation
2Reliability
If conventional corner rounding is applied to reduce stress concentration, then some stress dispersion is achieved, but crack and air bubble defects still occur due to insufficient stress reduction
Solution Approach 1:
The patent uses arc-like rounded portions at corners to eliminate stress concentration points, achieving sufficient stress dispersion that prevents crack and air bubble defects in the resin filler
Solution Approach 2:
The patent segments the corner region into multiple zones by combining rounded portions with chamfered portions, creating a progressive stress transition zone that effectively prevents defect formation
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 design effectively minimizes stress concentration, preventing cracks and air bubbles, thereby enhancing the quality and reliability of the component-built-in wiring board without compromising the component's properties.
Implementation Method 1
stress resulting from difference in the coefficient of thermal expansion between the core material and the capacitor occurs
Implementation Method 2
the resin filler disposed therebetween can absorb such deformation
Data Source
AI summary
Embodiments of the present invention provide a component-built-in wiring board capable of preventing a defect, such as a crack, resulting from stress concentration at a corner, when a component is accommodated in a housing portion of a core material with resin filler filled therebetween. The component-built-in wiring board can include a component accommodated in the housing portion of a core material, and a laminate portion in which insulating layers and conductor layers are laminated alternately on the core material. A gap between the housing portion of the core material and the component can be filled with a resin filler. In an inner circumferential portion of the housing portion of the core material a first straight chamfered portion is formed at each corner of a rectangle, and in an outer circumferential portion of the component a second straight chamfered portion is formed at each corner of a rectangle.