PCB Flow Guiding Groove for Adhesive Overflow Control
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Solution Overview
Problem
Current flexible printed circuit boards (FPCs) face challenges in compact design due to adhesive overflow issues, which can lead to incomplete bonding and structural imperfections, such as short circuits and open circuits, especially in display modules requiring full-screen, long endurance, and 5G communication capabilities.
Innovation Solution
A printed circuit board design featuring a hard-board region with a flow guiding groove on the covering film to direct adhesive overflow to the periphery, reducing the need for additional adhesive space and allowing for a more compact structure by minimizing adhesive overflow into the soft-board region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive film is used to bond layers in FPC design, then bonding strength is improved, but adhesive overflow may flow to golden-finger region causing bonding failure or soft-board hardening
Solution Approach 1:
A flow guiding groove is introduced as an intermediary structure between the adhesive film and the golden-finger region. This groove acts as a mediator that intercepts and redirects adhesive overflow away from the bonding area, preventing direct contact between excess adhesive and the golden-finger region, thus maintaining both bonding strength and reliability
Solution Approach 2:
The harmful component (adhesive overflow) is extracted and redirected through the flow guiding groove to a safe disposal location. By separating the adhesive flow path from the bonding area, the design eliminates the harmful effect of adhesive overflow while preserving the beneficial bonding function
2Reliability
If additional room is reserved for adhesive overflowing, then adhesive overflow is prevented from flowing to golden-finger region, but FPC size increases reducing compactness
Solution Approach 1:
Instead of increasing the planar area to accommodate adhesive overflow, the design utilizes the vertical dimension by creating a flow guiding groove that directs adhesive overflow downward along the layer interface. This dimensional transition allows adhesive management without increasing FPC footprint, maintaining compactness while preventing harmful overflow
3Reliability
If soft-board region is made harder to prevent adhesive overflow, then adhesive overflow is blocked, but bending capability is lost
Solution Approach 1:
The FPC is segmented into distinct functional regions: a hard-board region for structural support and adhesive containment, and a soft-board region for flexible bending. The flow guiding groove is positioned at the interface between these regions, allowing the soft-board region to maintain its bending capability while the hard-board region manages adhesive overflow through the groove structure
Data Source
AI summary
A printed circuit board and a fabricating method thereof, and a displaying device. The printed circuit board includes a hard-board region (30) and a soft-board region (31), the soft-board region (31) is located at the periphery of the first edge (30a) of the hard-board region (30), the printed circuit board within the hard-board region (30) includes a base plate (301), and an adhesive film (302), a covering film (303) and a first metal layer (304) that are arranged in layer configuration on one side of the base plate (301), the adhesive film (302) is closest to the base plate (301), a flow guiding groove (3030) is disposed on the surface of the side of the covering film (303) that is closer to the adhesive film (302), and the flow guiding groove (3030) extends to a second edge (30b) of the hard-board region (30).