PCB Terminal Width Reduction for Solder Wettability
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Solution Overview
Problem
The challenge is to achieve sufficient solder wettability for printed circuit board terminals made of metal wire rods without the need for after-plating, especially in lead-free soldering, while also reducing the pitch and maintaining structural integrity and manufacturing cost-effectiveness.
Innovation Solution
A printed circuit board terminal is created by cutting a rectangular metal wire rod to form an insertion portion with a reduced dimension in the long side direction, allowing the existing plated layer to remain on three surfaces, which enhances solder wettability without additional plating processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If both opposite side surfaces of the metal wire rod terminal are processed by cutting to narrow the insertion portion width, then the through hole diameter can be reduced, but the non-plated base material is exposed at both side surfaces causing poor solder wettability
Solution Approach 1:
The terminal is divided into different functional zones: the insertion portion has reduced width for small through holes, while the connection portion maintains full width for reliable soldering. This segmentation allows each part to optimize its dimensions for its specific function.
Solution Approach 2:
The plated layer is selectively maintained on the insertion portion surfaces that contact the through hole and solder, while cutting is applied only to specific marginal portions. This local quality approach ensures solder wettability is preserved at critical interfaces.
2Productivity
If the pitch of printed circuit board terminals is narrowed to increase density, then more terminals can be accommodated, but the interval between through holes becomes narrow making formation and soldering difficult
Solution Approach 1:
The terminal width is reduced in one dimension (the dimension corresponding to the pitch direction) while maintaining sufficient dimensions in other directions for manufacturing. This dimensional optimization allows narrow pitch accommodation without compromising through hole formation or soldering quality.
3Reliability
If after-plating is applied to improve solder wettability of the insertion portion, then solder wettability is improved, but the manufacturing process becomes complicated and cost increases
Solution Approach 1:
The plated layer is applied to the entire metal wire rod surface before cutting, ensuring that the insertion portion surfaces are pre-plated and ready for soldering. This preliminary plating action eliminates the need for subsequent selective plating operations.
Solution Approach 2:
The initial plating process automatically provides the necessary solderable surface on the insertion portion without requiring additional dedicated plating steps. The system uses the existing plating infrastructure to serve the dual purpose of connection portion and insertion portion plating.
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 configuration ensures sufficient solder wettability and reduces the size of through holes in printed circuit boards, improving space efficiency and manufacturing cost-effectiveness, even in lead-free soldering, while maintaining structural integrity.
Implementation Method 1
One end portion of the printed circuit board terminal in an longitudinal direction includes an insertion portion that is inserted into a through hole provided in a printed circuit board and is soldered
Data Source
AI summary
A printed circuit board terminal includes a rectangular metal wire rod having a substantially rectangle cross-section. One longitudinal end portion of the printed circuit board terminal includes an insertion portion that is configured to be inserted into a through hole provided in a printed circuit board and soldered. A conducting metal plated layer is provided on an entire surface of the rectangular metal wire rod. One marginal portion of the insertion portion, which faces a long side direction of the rectangle cross-section, is removed to reduce a dimension in the long side direction corresponding to a width direction.