Wiring Substrate Cutout Protrusion Brazing Strength
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Solution Overview
Problem
The reduction in size of external electrode portions on wiring substrates has led to decreased joining strength and mounting reliability of electronic devices when brazed to mount boards, due to reduced brazing material effectiveness.
Innovation Solution
A wiring substrate design featuring an insulating substrate with a cutout that extends to the lower surface and includes a protrusion on its inner surface, allowing the brazing material to easily stay inside the cutout and form a larger meniscus, enhancing the joining strength between the substrate and the mount board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the external electrode portion is reduced, then the wiring substrate can be downsized, but the joining strength to the mount board decreases
Solution Approach 1:
The invention transitions from a two-dimensional planar electrode structure to a three-dimensional structure by forming a protrusion that extends upward from the substrate surface. This vertical dimension allows the brazing material to pool and form a larger meniscus around the protrusion, significantly increasing the effective bonding area and joining strength without increasing the horizontal footprint of the external electrode portion.
Solution Approach 2:
The protrusion creates a localized region with enhanced properties for brazing material accumulation. The upper surface of the protrusion serves as a specific localized area where brazing material preferentially collects, forming a larger meniscus that improves joining strength. This local structural modification concentrates the bonding function in a specific region without requiring overall enlargement of the electrode.
2Volume of moving object
If the size of the external electrode portion is reduced, then the wiring substrate can be downsized, but the mounting reliability decreases
Solution Approach 1:
By adding the vertical dimension through the protrusion structure, the invention creates additional bonding interface area for the brazing material. The brazing material can flow around and adhere to the protrusion surface, creating multiple bonding zones that enhance the reliability of the mounting connection despite the reduced overall electrode size.
Solution Approach 2:
The protrusion structure provides a curved upper surface that facilitates the formation of a larger meniscus by the brazing material. This curved geometry allows the brazing material to pool and adhere more effectively, creating a more reliable bonding interface compared to a flat surface of the same footprint.
3Strength
If the brazing material forms a larger meniscus, then the joining strength increases, but the complexity of the substrate structure increases
Solution Approach 1:
The protrusion can be formed as a separate structural element that is integrated with the substrate. This segmentation allows the protrusion to be independently optimized for its brazing function while remaining part of the overall substrate assembly. The modular nature of the protrusion structure makes it easier to manufacture and integrate without significantly complicating the overall device fabrication process.
Data Source
AI summary
A wiring substrate comprises an insulating substrate and an external electrode on the insulating substrate. The insulating substrate comprises a lateral surface comprising a cutout. The cutout extends to a lower surface of the insulating substrate. The external electrode extends from an inner surface of the cutout to the lower surface of the insulating substrate. The insulating substrate comprises a protrusion at a lower end portion of the inner surface of the cutout. The protrusion protrudes from the inner surface of the cutout toward the lateral surface of the insulating substrate.