Flexible Circuit Board Dummy Layers for Hot Press Spring Back
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Solution Overview
Problem
Existing display devices face challenges in preventing connection defects between flexible and printed circuit boards due to spring back effects during the coupling process, which can lead to lifting defects and compromised electrical connections.
Innovation Solution
The implementation of a flexible circuit board with dummy layers and solder resist layers on an insulation film, arranged in a zigzag or offset configuration, to minimize deformation and pressure distribution during hot pressing, ensuring that only the pad columns are pressed, thereby preventing spring back effects and lifting defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot press equipment is used to couple the PCB and flexible circuit board, then electrical connections are established through conductive balls in ACF, but spring back effects cause lifting defects and connection reliability deteriorates
Solution Approach 1:
The patent applies preliminary action by forming dummy layers on the flexible circuit board before the hot pressing process. These dummy layers are positioned to receive pressing force during coupling, pre-compensating for the spring back effect that would otherwise cause lifting defects. The dummy layers are removed after coupling, having already performed their function of maintaining contact pressure on the pad parts during the critical connection phase.
Solution Approach 2:
The dummy layers serve as an intermediary element during the coupling process. They mediate between the hot press equipment and the pad parts by absorbing and distributing the pressing force uniformly. This intermediary structure prevents direct localized pressure that would cause spring back and lifting, ensuring reliable electrical connections through the ACF conductive balls without positioning precision degradation.
2Productivity
If uniform pressing force is applied during hot pressing, then coupling efficiency is improved, but spring back effects cause non-uniform deformation and connection defects
Solution Approach 1:
The patent applies local quality by creating non-uniform pressing force distribution through the dummy layers. The dummy layers are strategically positioned to concentrate pressing force on specific pad column areas while leaving other regions with different pressure characteristics. This localized pressure distribution matches the actual coupling requirements, improving deformation uniformity and preventing spring back effects that would cause connection defects, while maintaining high coupling efficiency.
3Ease of operation
If the flexible circuit board is made more flexible for mounting, then ease of mounting is improved, but susceptibility to spring back effects and lifting defects increases
Solution Approach 1:
The dummy layers are formed on the flexible circuit board before mounting operations, serving as preliminary protective structures. These layers are positioned to receive and distribute pressing force during the coupling process, pre-compensating for the spring back effect that flexible materials are prone to. This preliminary action maintains connection stability despite the inherent flexibility of the circuit board material.
Solution Approach 2:
The dummy layers act as an intermediary between the flexible circuit board material and the hot press equipment. They mediate the interaction by providing a controlled interface for force application, preventing the flexible board from undergoing uncontrolled spring back deformation. This intermediary structure enables the flexible board to maintain both its mounting flexibility and connection stability during the coupling process.
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 effectively suppresses the spring back effect, preventing lifting defects and ensuring reliable connections between the printed circuit board and the flexible circuit board, enhancing the stability and reliability of the display device.
Implementation Method 1
pressing the input pad part of the flexible circuit board by hot press equipment
Implementation Method 2
conductive balls included in the ACF contact the pad part of the PCB and the input pad of the flexible circuit board to conduct the pad part of the PCB and the input pad of the flexible circuit board
Data Source
AI summary
A display device including a flexible circuit board including an insulation film, the insulation film including an input pad part and an output pad part on a first side thereof; a printed circuit board including a first pad part, the first pad part being connected to the input pad part; and a display panel including a second pad part, the second pad part being connected to the output pad part, wherein the input pad part includes a plurality of input pads that are arranged in at least two pad columns, and the flexible circuit board includes a plurality of dummy layers aligned with the plurality of input pads on a second side of the insulation film, the second side being an opposite side to the first side.