FPC Through-Hole Structure for Accurate PCB Solder Joint Detection
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Solution Overview
Problem
The challenge of misjudgment in welding quality and increased risk of poor welding between flexible printed circuit boards and printed circuit boards, particularly in multi-layer structures or those using liquid crystal polymer, is prevalent in conventional FPC on Board welding processes, leading to inefficiencies and potential failures.
Innovation Solution
A through hole design on the flexible printed circuit board with a recessing part and connection segment is implemented, allowing the welding piece to overflow into the recessing part, enhancing welding strength and enabling accurate detection of welding quality, while reducing the path of exposure and risk of poor welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional tin penetration hole is used in the flexible printed circuit board, then welding strength is improved and welding state can be detected, but welding quality misjudgment frequently occurs in multi-layer structures or LCP boards
Solution Approach 1:
The through hole is divided into two functional segments: a connection segment for establishing electrical connection and a recessing part for welding detection. This segmentation allows the connection segment to ensure reliable welding while the recessing part provides a dedicated detection zone, eliminating the misjudgment problem in multi-layer and LCP board structures.
Solution Approach 2:
The recessing part acts as an intermediary detection zone that facilitates accurate welding quality assessment. By providing a dedicated recessed area where welding pieces accumulate, it serves as a mediator between the connection process and quality detection, enabling clear visual or automated inspection without misjudgment.
2Difficulty of detecting and measuring
If the path of exposure for welding piece is long, then welding detection is difficult, but shortening it may compromise welding strength
Solution Approach 1:
The recessing part introduces a vertical dimension to the through hole structure, creating a stepped configuration. This dimensional change allows the welding detection to occur in a vertically recessed area rather than requiring a long horizontal exposure path, thus shortening the detection path while maintaining welding strength through the connection segment.
3Weight of moving object
If FPC on Board welding process is used to meet lightening and thinning requirements, then device weight and thickness are reduced, but welding quality misjudgment and poor welding risk increase
Solution Approach 1:
By segmenting the through hole into connection segment and recessing part, the design maintains the lightweight FPC on Board welding process while improving welding reliability. The connection segment ensures strong welding, and the recessing part enables accurate quality detection, eliminating misjudgment risks.
Solution Approach 2:
The recessing part provides a clear visual or detectable feature for welding quality assessment, replacing complex mechanical or procedural detection methods. This substitution enables reliable welding quality determination in the streamlined FPC on Board process without adding significant weight or complexity.
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 improves welding strength and accuracy of detection, reduces the risk of poor welding, and facilitates the lightening and thinning of electronic devices by ensuring reliable electrical connections.
Implementation Method 1
the welding piece in a molten state on the pad overflows into the recessing part through the connection segment, and welds the welding part to the pad
Data Source
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AI summary
Embodiments of this application provide a circuit board assembly, a manufacturing method, and an electronic device. The circuit board assembly includes a flexible printed circuit board and a printed circuit board, a pad for disposing a welding piece is provided on the printed circuit board, the flexible printed circuit board includes a main body and a welding part disposed on an inner wall of a through hole of the main body, the through hole includes a recessing part and a connection segment connected to a bottom wall of the recessing part, the recessing part is disposed on a side that is of the connection segment and that is away from the pad, and an end that is of the connection segment and that is away from the recessing part faces the pad, so that the welding piece overflows into the recessing part through the connection segment, and welds the welding part to the pad. The circuit board assembly of this application reduces welding difficulty and a risk of poor welding of the flexible printed circuit board and the printed circuit board.