PCB Radial Pad Layout with Edge-Cut Through Holes for Solder Bridge Prevention
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Solution Overview
Problem
In printed wiring boards with narrow pitch between leads, solder bridges are prone to form due to the narrow pitch between soldered pads, leading to soldering defects.
Innovation Solution
The design includes pads aligned along a circular circumference with through holes that partially cut away one side edge, creating a larger inner region for solder fillet formation and preventing solder bridges by ensuring adequate space for solder distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pitch between pads is reduced to accommodate narrow lead pitch, then the productivity and compactness are improved, but solder bridges are more prone to form between pads
Solution Approach 1:
The pad structure is segmented into multiple functional regions: a mounting location for the component, a soldering land group formed along the edges, and solder-drawing lands at the corners. This segmentation creates distinct zones that control solder flow and prevent bridges while maintaining compact pad spacing.
Solution Approach 2:
Solder-drawing lands with solder-attracting material are introduced as intermediary elements at the corners where edges intersect. These intermediary regions actively attract and contain solder, preventing it from bridging to adjacent pads while ensuring reliable solder joints on the mounting location.
2Reliability
If solder-drawing lands with solder-attracting material are added to prevent solder bridges, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The solder-drawing lands are merged with the corner regions where the edges of the mounting location intersect. This combining of functions (corner structure + solder attraction) into a single integrated feature adds reliability without proportionally increasing complexity, as the solder-attracting material is placed at natural geometric features of the pad layout.
3Reliability
If the number of wiring patterns is delimited to prevent solder bridges, then the reliability is improved, but the manufacturing flexibility is reduced
Solution Approach 1:
The pattern design applies local quality by creating solder-drawing lands specifically at corner regions where solder bridges are most likely to occur, while leaving other areas with standard wiring patterns. This localized approach prevents solder bridges without requiring delimitation of the entire wiring pattern system, thereby maintaining manufacturing flexibility.
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 configuration effectively suppresses solder bridges and ensures proper solder fillet formation, maintaining integrity during heat cycles without cracks or excessive swelling.
Implementation Method 1
providing a material that attracts the solder in a hole of each of the solder-drawing lands
Data Source
AI summary
A printed wiring board includes a plurality of pads aligned along a circular circumference, and a plurality of through holes formed in the respective pads so as to overlap therewith. The pads each extend along the radial direction of the circular circumference, and have a shape that becomes wider in a direction away from a center of the circular circumference. The through holes are each located close to one side edge of the corresponding pad extending along the radial direction of the circular circumference, and spaced from the other side edge, and the one side edge is partially cut away by the through hole. The through hole partially cutting away the one side of the pad, and the other side edge of another pad adjacent to the pad are opposed to each other with a clearance therebetween.