Flexible Printed Circuit Wiring Layout for COF Short-Circuit Prevention
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Solution Overview
Problem
The existing chip on film (COF) method for mounting semiconductor chips on flexible printed circuit boards is prone to short-circuits due to conductive adhesive balls connecting adjacent wiring electrodes, necessitating a new structure to enhance reliability and reduce size.
Innovation Solution
A flexible printed circuit board design with specific spacing and length configurations for wiring regions, including a protective layer on some bonding regions and dummy patterns to prevent short-circuits, allowing for increased wiring density and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive adhesive is used to connect wiring electrodes, then electrical connection is achieved, but short-circuits occur between adjacent wiring electrodes
Solution Approach 1:
The patent divides the bonding region into multiple discrete bonding pads rather than using continuous conductive adhesive coverage. This segmentation isolates adjacent wiring electrodes, preventing conductive adhesive from creating short-circuits between them while maintaining reliable electrical connections at each pad location.
Solution Approach 2:
The patent applies conductive adhesive only at specific localized bonding pad regions rather than uniformly across the entire bonding area. This local quality approach ensures electrical connection reliability at connection points while eliminating the harmful effect of conductive paths between adjacent wiring electrodes in non-bonding regions.
2Area of stationary object
If wiring density is increased to reduce device size, then compactness is improved, but short-circuit risk increases due to reduced spacing
Solution Approach 1:
By segmenting the bonding region into discrete pads with non-conductive spacing, the patent enables higher wiring density without proportionally increasing short-circuit risk. The segmented structure maintains adequate effective spacing between conductive elements even when overall device size is reduced.
Solution Approach 2:
The patent introduces a non-conductive intermediary layer or structure between adjacent wiring electrodes in the bonding region. This intermediary prevents direct conductive paths while allowing the wiring density to be increased for compactness, effectively mediating between the competing requirements of size reduction and short-circuit prevention.
Data Source
AI summary
A flexible printed circuit board according to an embodiment includes a substrate, a circuit pattern disposed on the substrate, and a protective layer on the circuit pattern, wherein the substrate includes a chip mounting region, the circuit pattern includes a first circuit pattern and a second circuit pattern connected to a chip of the chip mounting region, the second circuit pattern includes a plurality of second wiring portions and a third pad portion and a fourth pad portion connected to the second wiring portion, the second wiring portion includes a first wiring region connected to the fourth pad portion and a second wiring region bent in the first wiring region, a first space of the first wiring region is greater than a second space of the second wiring region, and a length of the first wiring region is 100 μm or more.