Rigid-Flex PCB Layout to Prevent Via Cracks While Reducing Thickness
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Solution Overview
Problem
Rigid flexible printed circuit boards (RFPCBs) in electronic devices are prone to via cracks due to bending stresses, leading to signal loss and reduced reliability, and they often have a thick design that is not optimal for modern electronic devices.
Innovation Solution
A RFPCB design featuring a flexible portion with a first dielectric and a rigid portion with a second dielectric, multiple conductive patterns, and conductive vias that connect these layers, reducing thickness and preventing via cracks by using a specific dielectric material configuration and bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the rigid flexible printed circuit board is bent to achieve flexibility and portability, then the adaptability and portability are improved, but the conductive vias may crack due to bending stresses, leading to reduced reliability
Solution Approach 1:
The circuit board is divided into a flexible portion and a rigid portion, with conductive vias strategically positioned only in the rigid portion. This segmentation allows the board to be bent in the flexible area without subjecting the conductive vias to bending stresses, thereby maintaining both flexibility and via crack resistance.
2Reliability
If multiple insulation layers are used to ensure electrical isolation and reliability, then the reliability is improved, but the thickness of the circuit board increases, reducing productivity and increasing device size
Solution Approach 1:
The patent applies different dielectric constants to different portions of the circuit board: a first dielectric constant in the flexible portion and a second dielectric constant in the rigid portion. This local differentiation allows for optimized electrical isolation in each region while reducing the overall thickness compared to uniform multi-layer designs.
Data Source
AI summary
An electronic device is provided. The electronic device includes a first electrical element, a second electrical element, and a rigid flexible printed circuit board electrically connecting the first electrical element and the second electrical element, wherein the rigid flexible printed circuit board includes at least one flexible portion including a first dielectric which has a first dielectric constant and is flexible, at least one rigid portion which extends from the flexible portion and includes a second dielectric which has a second dielectric constant and is less flexible than the first dielectric, a plurality of conductive patterns formed inside the first dielectric and the second dielectric, a plurality of conductive layers formed on the first dielectric and the second dielectric, and a plurality of conductive vias which are formed in the rigid portion and electrically connect the plurality of conductive layers or the plurality of conductive patterns.