Flexible PCB With Embedded Conductive Balls for Fine-Pitch Display Bonding
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Solution Overview
Problem
As display device resolutions increase, ensuring reliable electrical connections between flexible printed circuit boards and display panels becomes challenging due to smaller pad sizes and pitches, necessitating improved connection methods without separate conductive adhesive members.
Innovation Solution
A flexible printed circuit board design featuring a base film with a wiring layer and partially embedded conductive balls, which includes a base layer and a plurality of conductive balls, which includes materials like nickel, molybdenum, chromium, and titanium, and a nonconductive film for bonding, eliminating the need for additional conductive adhesives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of display devices is increased, then the display quality is improved, but the pad size and pitch become smaller, making connection reliability difficult to ensure
Solution Approach 1:
The invention divides the bonding interface into multiple discrete conductive balls instead of using a continuous conductive adhesive layer. Each conductive ball independently establishes an electrical connection between the FPCB wiring layer and the display panel pad, ensuring reliable connections even when pad sizes and pitches are reduced due to higher resolution requirements.
Solution Approach 2:
The conductive balls serve as intermediary elements between the FPCB and the display panel. These spherical conductors are embedded in the wiring layer and protrude to contact the pad portions, mediating the electrical connection without requiring separate conductive adhesive members, thus maintaining connection reliability at smaller dimensions.
2Reliability
If separate conductive adhesive members are used for bonding, then electrical connection is achieved, but the device complexity and manufacturing steps increase
Solution Approach 1:
The invention merges the conductive connection function and the bonding function into a single integrated structure. The conductive balls are directly embedded in the wiring layer during FPCB manufacturing, combining the electrical conductor and the bonding interface element into one component, thereby eliminating the need for separate conductive adhesive members and simplifying the overall bonding structure.
Solution Approach 2:
The conductive balls perform multiple functions simultaneously: they serve as electrical conductors for signal transmission, as bonding interface elements for mechanical attachment between FPCB and display panel, and as alignment references during the bonding process. This multi-functionality reduces the need for additional separate components.
3Ease of manufacture
If conductive adhesive members are eliminated, then manufacturing complexity is reduced, but ensuring reliable electrical connection becomes more challenging
Solution Approach 1:
The conductive balls are prepared and embedded in the wiring layer during the FPCB manufacturing process before the bonding step. This preliminary action ensures that the electrical connection elements are already in place and properly positioned, making the subsequent bonding process simpler and more reliable without requiring separate conductive adhesive materials.
Data Source
AI summary
A flexible printed circuit board includes a base film, a wiring layer disposed on the base film and a plurality of conductive balls partially embedded in the upper surface of the wiring layer. A display device includes a display panel including a display area and a peripheral area, a flexible printed circuit board facing and bonded to a pad portion disposed in the peripheral area and a nonconductive film disposed between the pad portion and the flexible printed circuit board, wherein the flexible printed circuit board includes a plurality of conductive balls partially embedded on an upper surface of a wiring layer disposed on a base film, and the pad portion has a portion that comes into contact with the plurality of conductive balls.