This webinar is an introduction to Flex and Rigid–Flex Gerber layout design methods and requirements that differ from standard rigid board technology. Prepare to review some of the unique elements of Flex and Rigid–Flex Gerber layout to ensure functionality and mechanically reliability that meets or exceeds the design requirements.

1.  DELIVERING QUALITY SINCE 1952.
Rigid – Flex Circuit
Gerber Layout Guidelines
05.30.14

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 Rigid – Flex circuits introduce additional design
requirements which need to be accommodated at the
Geber Layout phase:
– Rigid to Flex Transition Lines
– Layer Stack ups
– Trace Layout in Flex Areas
Introduction

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Introduction
 Guidelines based on IPC 2223C recommended Rigid – Flex
Construction(s):
– Ensures the highest degree of reliability and performance
– Key Elements
• Adhesiveless Flex Core
• Selective Flex Area Coverlay
• No Flow Prepreg (rigid area layer lamination)

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 Definition: Line at which flex layers exit from Rigid area(s)
– Special requirements due to:
• IPC 2223C Selective Coverlay and Material Guidelines
• Manufacturing Methods:
– Rigid Materials (FR4 & Prepreg) are removed from flex areas
prior to the layer lamination process
Rigid to Flex Transition Lines

5. 5
Rigid to Flex Transition Lines:
PTH Hole Spacing
 0.050” Min. Requirement:
– As measured from edge of drilled hole to “Rigid to Flex” transition line(s)
– Prevents PTH holes from being drilled through Selective Coverlay
adhesives
– Accounts for manufacturing and material tolerances

6. 6
Rigid to Flex Transition Lines:
Copper Feature Spacing
 0.025” Min. Clearance (External Layers only)
– Allows for manufacturing methods and tolerances during outer layer
imaging processes
– Accounts for prior removal of rigid materials in flex areas

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Rigid – Flex Layer Stack Up Guidelines
 Flex Layer Core Thickness(s):
– 0.001” recommended
• Improved flexibility, mechanical reliability and bend radius capability
– 0.002” to 0.003” required for impedance controlled designs
 Balanced Construction with centrally located Flex Layers Recommended:
– Minimizes potential warp and twist in assembly arrays
– Avoids potential cost adders
– Unbalanced builds possible but should be reviewed with supplier in advance
Balanced Construction Unbalanced Construction

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Rigid – Flex Layer Stack Up
Guidelines
 Same Finished Thickness in all Rigid Areas:
– Avoids sequential lamination processes and significant added costs
– Consult with supplier to determine viability
 Odd Layer Counts Allowed:
– E.G.: 5 Layer Rigid with 1 or 3 layers flex etc.
 Flex Area Layer Count:
– Minimize for thinnest possible construction
• Improved flexibility, reliability and bend radius
 Flex Layer Copper Weight:
– ½ OZ Copper recommended
• Improved flexibility and mechanical reliability
• Allows for impedance controlled circuits
– 1 OZ Copper available for higher current carrying requirements

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Rigid – Flex Layer Stack Up
Guidelines
 Paired Flex Layers Structure Recommended:
– Eliminates flex adhesives from rigid areas for PTH reliability
– Improves flex area flexibility and mechanical reliability
8 Layer Rigid – 2 Layer Flex 8 Layer Rigid – 4 Layer Flex (Air Gap)

10. 10
Rigid – Flex Layer Stack Up
Guidelines
 Impedance Controlled / Shielded Designs:
– May require 3 or more flex layers bonded together
– Use of flex adhesives to be minimized to best conform to IPC 2223C
– Potential negative impact on flexibility and bend requirements
– Consult with supplier for best configuration
7 Layer with 3 Flex Layers 8Layer with 4 Flex Layers

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Flex Area Trace Layout Guidelines
 Offset Traces from Layer to Layer in Flex Area (if possible)
– Improves mechanical flexibility by minimizing “I-Beam” effect
– Impedance Controlled and Shielded Designs will not fully allow due to
reference plane requirement
Preferred Not Recommended
Impedance Controlled Design

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Flex Area Trace Layout Guidelines
 Straight / Parallel Trace layout is preferred:
– Eliminates potential mechanical stress concentrators in bend areas
– If direction change is required then rounded trace corners are
recommended
• Up to 45 degree corners are allowed
• 90 degree corners are not recommended

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Our Products
Battery Packs Flex & Rigid-Flex PCB’s User Interfaces
Fans & Motors Cable Assemblies Printed Circuit Boards

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Design Centers & Technical Support
 Battery Pack & Power Management – Denver, CO
 User Interfaces – Largo, FL
 Fans & Motors – Wales, UK
 PCB’s – New Bedford, MA & Shenzhen, China
 Flex & Rigid Flex – Toronto, Canada
 Cable Assemblies – New Bedford, MA
 Our Engineering and Design teams are ready to help
our customers create world class and cost effective
product solutions.

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Q&A
 Questions?
– Enter any questions you may have
in the Control Panel.
– If we don’t have time to get to it, we
will reply via email.

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Thank You
Check out our previous webinars at www.epectec.com.
For more information email sales@epectec.com.
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