This second part of Würth Elektronik PCB webinar on RIGID.flex technology is intended as an introduction to the production of rigid-flex PCBs and covers constructions with internal flex layers.
This video continues WE series and “PCB Production: RIGID.flex”.
The second part on RIGID.flex technology is intended as an introduction to the production of rigid-flex PCBs and covers constructions with internal flex layers.
And of course, a rigid-flex printed circuit board is also a very complex construct, produced by a large number of sequential processes from a wide variety of materials, which must also be suitable for further processing and the planned application. Understanding this helps in PCB design to be able to successfully implement the requirements from the functional specification in the design and the knowledge equally helps in communicating with the PCB manufacturer.
This webinar series teaches the basics of PCB production and is aimed at PCB designers, buyers, electronics developers and students.
In this webinar you will learn more about
- The difference in RIGID.flex between buildups with inner and outer flex layers
- The manufacturing and production processes for rigid-flex with internal flex layers
- WE advantageous standard stackups
- Application examples
Advanced Production Processes of Asymmetrical Rigid-Flex PCBs
Introduction
Welcome to the third part of our PCB production series, focusing on asymmetrical Rigid-Flex PCBs. I am Guido Bernard, with over 30 years of experience in the PCB industry. Since September 2020, I have been involved in technical product management at Hotel Electronic. This article serves as a continuation of the previous webinar, “PCB Production Part 2: Rigid-Flex,” and delves deeper into asymmetrical stack-ups and their production processes.
Review of PCB Production Part 2
The previous webinar covered the distinctions between flexible and rigid-flex circuit boards, detailing the base materials and manufacturing processes for rigid-flex PCBs, specifically the 1F7RI configuration (one flex layer on the top side and seven rigid layers). These webinars are archived on our homepage for further reference.
Application Examples
1. Industrial Handheld Electronics
- Stack-Up: 3RI-2F-3RI (Three rigid layers, two flex layers)
- Motivation: Miniaturization, reliability, and system efficiency
- Key Features: Enhanced durability and compact design
2. Industrial Camera
- Stack-Up: 3RI-2F-3RI
- Features:
- Defined flex layer thickness
- Mesh design on reference layers
- USB connectors with separated rigid sections for optimized space
3. High-Resolution, High-Speed Camera
- Application Areas: Astronomy, Spectroscopy, Area Scanning
- Stack-Up: 4RI-4F-4RI (12-layer board)
- Technical Details:
- Impedance-defined signals
- FR4 standard with TG 150°C
- All flex layers bonded within the flex area
Standard Stack-Ups
1. Four-Layer PCB (1RI-2F-1RI)
- Configuration: One rigid layer, two flex layers
- Thickness Options: 1 mm to 1.5 mm
2. Six-Layer Board (2RI-2F-2RI)
- Configuration: Two rigid layers, two flex layers
- Thickness: 1 mm to 1.55 mm
3. Advanced Construction (3RI-4F-3RI)
- Configuration: Three rigid layers, four flex layers
- Bonding: Flex layers bonded with ball players in the flex area
Non-Standard Stack-Ups
2RI-2F+2F-3RI
- Key Difference: Air gaps between flex cores
- Gap Specifications:
- 5 mil to 8 mil for 2F+2F stack-up
- 100 microns for 4F constructions
Production Processes
The production of asymmetrical rigid-flex PCBs involves both standard and specialized processes:
Standard Processes (Highlighted in Blue)
- Includes: Exposure, development, etching, optical inspection
Specialized Rigid-Flex Processes (Highlighted in Yellow)
- Flex Layer Production:
- Pre-treatment, resist laminating, exposure, etching, cleaning
- Use of specialized materials like PTFE foil
- Cover Layer Processing:
- Cutting, lamination, and pressing with composite materials
- Deep Milling Process:
- Removal of PTFE films
- Ensuring mechanical integrity in flex areas
Final Production Steps
- Carrier Milling and Contour Cleaning
- Optical Final Inspection
- Shipping of Finished PCBs
Summary
This article has provided insights into the production of asymmetrical rigid-flex PCBs, focusing on stack-up configurations, application examples, and specialized manufacturing processes. For in-depth design guidelines, please visit our website.