Segmented Metal Post for PCB Stress Distribution
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Solution Overview
Problem
The challenge is to distribute stress effectively on printed circuit boards with fine pitch metal posts while reducing manufacturing costs, particularly in electronic component packages where stress concentration can occur at connection points between metal posts and soldered pads, leading to potential damage and increased costs due to material usage.
Innovation Solution
The solution involves designing metal posts with specific geometric configurations, including a first elongated portion, a narrower second portion, and a third portion of equal width, which extend from the substrate, allowing for increased solder contact points and stress distribution through grooves, thereby enhancing bonding stability and reducing metal material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If metal posts with fine pitch are used to implement electronic component packages, then the pitch of connection pads can be reduced, but stress concentration occurs at the connection points between metal posts and soldered pads
Solution Approach 1:
The metal post is divided into multiple segments with different widths along its length. The post includes a first post portion with a first width, a second post portion with a second width narrower than the first width, and a third post portion with a third width equal to or greater than the first width. This segmentation allows stress to be distributed across different sections rather than concentrated at a single point, resolving the stress concentration problem while maintaining fine pitch capability
Solution Approach 2:
Different portions of the metal post are given different local geometries (widths) to optimize specific functions at different locations. The narrower second post portion reduces stress concentration at the solder joint, while the wider first and third portions provide sufficient mechanical strength and soldering area. This local quality variation allows the post to simultaneously achieve fine pitch compatibility and stress distribution
2Ease of manufacture
If metal posts with constant width are used, then manufacturing is simpler, but soldering area is limited and stress distribution is insufficient
Solution Approach 1:
The metal post is segmented into portions with different widths (first post portion, second post portion, third post portion) to simultaneously increase soldering area and improve stress distribution. The segmentation is achieved through standard manufacturing processes like electroplating with varying thickness or multi-layer construction, maintaining ease of manufacture while enhancing reliability
Solution Approach 2:
The width parameter of the metal post is varied along its length to optimize both soldering area and stress distribution. The first post portion has a first width, the second post portion has a narrower second width, and the third post portion has a third width equal to or greater than the first width. This parameter change is implemented through controlled manufacturing processes, achieving enhanced reliability without significantly complicating manufacturing
3Reliability
If more metal material is used to increase soldering area, then bonding stability improves, but manufacturing cost increases
Solution Approach 1:
Metal material is concentrated where it is most needed - at the first post portion and third post portion where wide soldering surfaces are required for strong bonding. The second post portion uses less metal material (narrower width) where the primary function is stress distribution rather than soldering. This local quality optimization improves bonding stability while reducing overall metal material usage and manufacturing cost
Solution Approach 2:
The width parameter of the metal post is strategically varied to optimize material distribution. The first post portion has a first width providing sufficient soldering area, the second post portion has a reduced second width to minimize material usage while maintaining stress distribution function, and the third post portion has a third width equal to or greater than the first width for reliable bonding. This parameter optimization achieves cost reduction without sacrificing bonding stability
Data Source
AI summary
A printed circuit board includes a substrate including an external connection pad; and a metal post extending to the outside of the substrate in a thickness direction of the substrate from the external connection pad. The metal post may include a first post portion, elongated while having a substantially constant width, a second post portion extending to the outside of the substrate in the thickness direction of the substrate while having a narrow width, and a third post portion extending to the outside of the substrate in the thickness direction of the substrate from the second post portion while having substantially the same width as the first post portion. The third post portion may forma lower end portion of the metal post.