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Let's Get Flexible: Expert Tips for Designing Flex PCBs
The document outlines a webinar on flexible and rigid-flex circuit technology presented by Janine Flagg from EMA Design Automation, covering design solutions, materials, and manufacturing considerations for flex circuits. It discusses the advantages and challenges of using flexible circuits in various applications, and emphasizes the importance of design considerations such as routing, placement, and communication with manufacturers. The session aims to maximize the benefits of flex in PCB designs for successful implementation.
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Let's Get Flexible: Expert Tips for Designing Flex PCBs
- 1. Let’s Get FLEXibleWebinar 7/31/2018 1 Presented By: Janine Flagg Field Applications Engineer eMail: janinef@ema-eda.com
- 2. PCB CAD ExpertsNationwide Reach Over 4,000 Customers Example Customers PCB is in our DNA EMA Design Automation • Complete PCB design solutions • Regular speakers on PCB design topics • Local support & training • Founded in 1989 • Cadence PCB reseller • Dedicated CAD software development team 7/31/2018 2
- 3. Agenda • Overview ofFlex and Rigid Flex Circuits – Terms used – Materials used – Placement Considerations – Routing Considerations – 3D & Manufacturing Considerations • Demo – Functionality needed to design flex and rigid flex – 3-D views 7/31/2018 3
- 4. Flex Circuits 7/31/2018 4 FlexibleCircuit Technology • Mounting the devices on flexible plastic substrates • Polyimide or transparent conductive polyester film Used in: • Consumer products • Computing applications • Military equipment Mechanical device as electrical Image source: MIT Technology Review
- 5. Flex Challenges &Benefits 7/31/2018 5 Reduced Space Improved Signal Quality Improved Durability Reduced Assembly Costs Benefits Challenges Design Complexity Manufacturing Complexity Higher Board Costs
- 6. Global PCB Market& Rigid-Flex 7/31/2018 6 Between 2013 and 2017 the percentage of Rigid Flex boards being designed more than doubled
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- 9. Types of FlexCircuits Single layer • Mounted on single conductor layer • Metal or conductive polymer, over a flexible dielectric film Double layer • Placed on two conductor layers Multi layer • Span three or more layers • May not be continuously laminated • May have openings 7/31/2018 10
- 10. Rigid-Flex Circuits • Flexcircuits placed on rigid substrates • Flex circuits placed on flexible substrates • Laminated together into a single structure 7/31/2018 11
- 11. Flex Circuit Terms Coverlay 7/31/201812 • Used to encapsulate and protect the external circuitry • Serves the same function as soldermask on a rigid PCB • Differences: – Flexibility – Durability • Typical coverlay thickness: – 0.001” polyimide – 0.001” adhesive
- 12. Flex Circuit Terms Stiffener 7/31/201813 Used to: – Reinforce areas of flexible circuitry – Component support, – Durability and mounting Can also be used for: – Strain relief – Heat dissipation Bonding materials include: – Pressure Sensitive Adhesive (PSA) – Temperature Sensitive Adhesive (TSA) Stiffener Materials: – Unclad FR4 / G10 – Polyimide
- 13. Flex Circuit Terms BendArea 7/31/2018 14 • An area on the board where a bend may occur • Define Areas – Width – Radius • Bend Area – Via Keepout – Package Keepout Bend Line Flex Area Bend Area
- 14. Flex Circuit Terms Materials 7/31/201815 • Wide variety of materials – Films – Foils – Adhesives – Polyester – Polyimide • Choice depends on how and where the circuit will be assembled and used • Consultation of fabricator is required
- 15. • Cross-section setupper design requirements • Not all layers exist in all zones • Care must be taken during placement and routing to ensure you are referencing the desired layers Design Considerations Layer Structures 7/31/2018 16
- 16. Design Considerations Routing inFlex Regions 7/31/2018 18 • Rigid-flex designs require curved bus lines • Routes to follow contour of flex area • Arc corners should be used whenever possible (especially in bend areas) • Flex board outlines often change during design cycle. Ability to quick adjust routes is key to efficiency
- 17. Design Considerations Placement &Routing in Bend Areas 7/31/2018 19 • Care must be taken when working in or around bend areas • Traces must cross bend areas perpendicularly to minimize material stress • Adjacent layer routing through the bend area should be offset to prevent what is called the I- BEAM effect • Pins and vias should not be allowed within or near bend areas to prevent cracking
- 18. Design Considerations Conductor andPad Design 7/31/2018 21 • Pads should have tie downs (also called anchoring spurs or rabbit ears) to prevent separation between the copper and the base material • All pads should be filleted because they reduce stress points. This helps eliminate breaking during flexing
- 19. Design Considerations Shielding 7/31/2018 22 •Required to block unwanted electronic interference • Ground areas of flex circuits should be crosshatched • Helps – Reduce weight – Improve circuit flexibility – Prevent tearing
- 20. Design Considerations MCAD Communication 7/31/201823 • Often bend areas and flex radius will be defined by mechanical requirements • It is important to maintain close communication with MCAD for any design changes • Bi-directional data sharing of flex info (bend, layer structure, etc) is critical between CAD systems
- 21. Design Considerations Fit andClearance 7/31/2018 24 • Must analyze flex for fit in 3D • Ideally this can be done by the PCB designer • Checking should be done not only at completed bend state but during bend as well
- 22. Design Considerations DFM &Manufacturer Handoff 7/31/2018 25 • Flex designs require additional checking and review • Flex regions will have specific requirements that differ from rigid sections including: – Soldermask to Stiffener – Coverlay to Soldermask – Silkscreen to bend region – Stiffener to via, outline, bend – Etc • Using a intelligent interchange format like IPC-2581 will help your manufacturer capture your design intent • Engage with your manufacturer early and often as need
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- 24. Designing for Flex 7/31/201833 Maximize the benefits of Flex with a PCB design solution built to help you overcome flex design challenges for first pass success. Rules driven placement and routing Flex aware setup and DFM checks Real-time 3D design and analysis
- 25. 7/31/2018 Why DFMMatters 34 Thank you for joining us today. Please contact us for more information on OrCAD products, training, and services. 800-813-7494 info@ema-eda.com www.ema-eda.com Up next: Designing for Power Integrity (PI) Learn how to ensure a healthy PDN and your keep products humming smoothly.