Semi-flexible PCB with exposed prepreg via dummy core
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Solution Overview
Problem
Existing printed circuit boards (PCBs) lack the ability to integrate semi-flexible circuitry layers that can be bent without compromising structural integrity or electrical connectivity, limiting their application in flexible electronic devices.
Innovation Solution
A printed circuit board design featuring a laminated stack with a core structure that includes both rigid and semi-flexible portions, where select sections are made semi-flexible by removing plugs to expose inner core circuitry protected by a prepreg layer and a dummy core, allowing for bendable PCB portions while maintaining structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional rigid PCB structure is used, then structural integrity is maintained, but flexibility and bendability are lost
Solution Approach 1:
The PCB is divided into two distinct portions: a rigid portion with full laminated stack structure and a semi-flexible portion with removed plugs. This segmentation allows different mechanical properties in different regions of the same PCB, enabling both structural integrity and flexibility to coexist in appropriate locations.
Solution Approach 2:
The rigid and semi-flexible portions are differentiated by local structural modifications. The semi-flexible portion has plugs removed to expose inner core circuitry, creating a localized change in mechanical properties while the rest of the PCB maintains its rigid structure. This allows the PCB to have rigid areas for stability and flexible areas for adaptability.
2Adaptability or versatility
If plugs are removed to create semi-flexible portions, then flexibility is improved, but manufacturing complexity increases
Solution Approach 1:
The plugs are removed during the manufacturing process at a stage when the laminated stack is still accessible and can be easily modified. By performing the plug removal as a preliminary action during fabrication rather than requiring post-manufacturing modification, the process is simplified and integrated into the existing manufacturing workflow.
Solution Approach 2:
The dummy core serves as an intermediary structure that facilitates the plug removal process. The dummy core is temporarily positioned to protect the inner core circuitry during manufacturing and then removed along with the plugs, leaving the semi-flexible portion with exposed circuitry while maintaining the integrity of the remaining structure.
3Adaptability or versatility
If inner core circuitry is exposed by removing plugs, then semi-flexible functionality is achieved, but protection of circuitry during manufacturing becomes more difficult
Solution Approach 1:
The dummy core is positioned to cover and protect the inner core circuitry before the plug removal process begins. This preliminary protective action ensures that the exposed circuitry is shielded during subsequent manufacturing steps, preventing damage while allowing the semi-flexible functionality to be achieved.
Solution Approach 2:
The dummy core acts as a cushioning protective layer placed beforehand to absorb or prevent potential damage to the inner core circuitry during the plug removal and subsequent manufacturing processes. This prior protection ensures the reliability of the circuitry even after it becomes exposed in the final semi-flexible portion.
Data Source
AI summary
A printed circuit board (PCB) has multiple layers, where select portions of one or more conductive layers, referred to as core circuitry, form a semi-flexible PCB portion that is protected by an exposed prepreg layer. The semi-flexible PCB portion having an exposed prepreg layer is formed using a dummy core process that leaves the exposed prepreg layer smooth and undamaged. The core circuitry is part of a core structure. The semi-flexible PCB portion is an extension of the remaining adjacent multiple layer PCB. The remaining portion of the multiple layer PCB is rigid. The core structure is common to both the semi-flexible PCB portion and the remaining rigid PCB portion.