AltiumLive 2017:ANNUAL PCBDESIGN SUMMIT

Tara DunnOmni PCB

Event Location,October 3, 2017

Why would you use flexible circuits?

Enabling Technology

Flex Materials and Best Practices

Case Studies

Specialty Circuits

Why Use Flexible Circuits

Cost Considerations

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Agenda

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Real World Advice from Industry Experts

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Why would you use flexible circuits?

Solve Product Packaging Problems

Why would you use flexible circuits?

Reduce Assembly Costs

Why would you use flexible circuits?

Reduces Both Weight and Volume

Why would you use flexible circuits?

They Facilitate Dynamic Flexing

Why would you use flexible circuits?

Thermal Management

Why would you use flexible circuits?

Improve Product Aesthetics & Bio-compatibility

Why would you use flexible circuits?

Intrinsically More Reliable & Reduce The Opportunity For Operator Error

Flex Materials and Best Practices

Case Studies

Specialty Circuits

Why Use Flexible Circuits

Cost Considerations

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3

Agenda

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4

Real World Advice from Industry Experts

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Base material types and design tips

Base Materials

Base material types and design tips

Common miscommunication

Base material types and design tips

Conductor Routing Practices

Maintain smooth transitions, avoid sharp edges

Key: Communicate operational requirements to your fabricator, especially with dynamically flexing applications

Base material types and design tips

Conductor Routing Practices

Base material types and design tips

Conductor Routing Practices

Use large fillets at the trace to pad interface

Base material types and design tips

Conductor Routing Practices

Consider Tear Strips for added

support

Base material types and design tips

Conductor Routing Practices

Keep transitions at least .030” from fold line

Coverlay types and design tips

Coverlay Options and Selection Criteria

Shielding types and design tips

Shielding Options

Cross hatch for greater flexibility. When using solid copper, be aware of quickly increasing thickness and rigidity for bending and folding.

Shielding options and design tips

Stiffener Types

.030” overlap to reduce stress point

Flexing and Bending

Bending Recommendations

Single Metal Layer: 3-6 times material thickness

Two Metal Layers: 7-10 times material thickness

Multilayer Flex: 15-20 times material thickness

Dynamic Flexing: 20-40 times material thickness.

Thru holes should be placed at least .050” away from any bend areas

Flexing and Bending

Tips and Tricks To Improve Flexibility

Route traces to second side and remove copper in flexing area

Cross hatch copper

Un-bonded layers

Consider Button-Plating to eliminate ED copper on panel when creating the PTH

Remove Material

Rigid Flex

Rigid Flex

Key Points:

• Adhesiveless Materials

• Bikini Cut the coverlay(.050” into the rigid areas)

• PTH should be .050” from edgeof flex / rigid interface

Bonded or un-bonded flex layers

Rigid Flex

Strain Relief

Flex Materials and Best Practices

Case Studies

Specialty Circuits

Why Use Flexible Circuits

Cost Considerations

2

3

Agenda

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4

Real World Advice from Industry Experts

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6

Cost Considerations

Panel Utilization

Cost Considerations

Material

• What are the most commonly stocked materials?

• Most Common Coverlay and cost trade-off’s

• Stiffeners – cost trade off’s

Cost Considerations

Technology

Low Cost Impact:• Complex routing/scoring• Greater than .093” or less than .030” rigid flex• Via Plug

Medium Cost Impact:• Aspect ration > 10:1• Drill hole count > 30K• Non-FR4 materials• Drilled holes < .10”• Line and Space < .005”• Button plating• Controlled Impedance

High Cost Factors• Advanced Technologies• Buried Vias• Layer Count• Material Utilization• Selective Plating• Dual Surface Finish• Line and Space < .004”

Cost Considerations

TechnologyInvolve your Fabricator early with complex designs.

Experience is a great educator. Take advantage of theirs!

Cost Considerations

Our best recommendation for the most cost effective design

Work with your

Fabricator!

Flex Materials and Best Practices

Case Studies

Specialty Circuits

Why Use Flexible Circuits

Cost Considerations

2

3

Agenda

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4

Real World Advice from Industry Experts

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6

Cost Considerations

Case Study

Medical Application:

Two part numbers designed as 3 layer rigid flex using flex as an outer-layer.• Requires button plating to maintain flexibility in the flex

regions• Required laser cutting of coverlay for surface mount pads• Tight registration required smaller manufacturing panel for

processing

After working with the supplier:• Converted to 4 layer rigid flex• Eliminated the need for button plating the flex layers• Eliminated the need for laser cut coverlay

Even though an additional layer was used and material costs are higher, this redesign resulted in a 20% cost savings.

Cost Considerations

Case Study

Telecommunications Application:

Issue:Customer had 50% failure during installationCopper in the flex area was cracking after being bent several times

Solution:Stack up was redesignedConverted stack up to adhesiveless materialsDecreased flex thickness from 11.8 mils to 8.4 mils (29% decrease)The extra thickness was adding rigidity to the flex area and causing cracking

Over 300 parts have been installed with no failures

Flex Materials and Best Practices

Case Studies

Specialty Circuits

Why Use Flexible Circuits

Cost Considerations

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3

Agenda

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4

Real World Advice from Industry Experts

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6

Specialty Circuits

Book Binder

Specialty Circuits

Additive Process

Benefits:

Finer Line and Space: 5 micron to 250 micron -critical to higher resolution devices and smaller packages

Fully Bio-Compatible Materials: Copper or gold traces can be applied directly to polyimide with no chrome or nickel tie coat

Ability to plate on a curved surface: Eliminates an interconnection

RF Advantage: Eliminate the trapezoidal effect of traditional copper etching

Processed on a variety of materials: flex, rigid, ceramic, plastics, fabric

Flex Materials and Best Practices

Case Studies

Specialty Circuits

Why Use Flexible Circuits

Cost Considerations

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3

Agenda

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Real World Advice from Industry Experts

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Real World Advice from Industry Experts

“Unlike rigid designs, capabilities are not universal across most fabricators. Work with the fabricator early in the process to agree on materials, stack-up line/space and fab tolerances.”

“Pay special attention to bend radius limitations and strain reliefs on inside cut and fold regions.”

David Bocchi, Boston Scientific

Real World Advice from Industry Experts

• Avoid abrupt changes in conductor size and direction

• Route conductors uniformly and perpendicular to fold lines

• Radius all cut-lines, NEVER have a sharp inside corner

• Use 3D modeling when laying out your flex

• Get your vendor involved as early in the design process as possible

Real World Advice from Industry Experts

“If PCB Designers want a reasonable amount of success than they need to make sure there documentation matches the Design.”

“Most Important, “The material call out needs to be perfect. As for the actual layout traces should be perpendicular to the trace bend, this is key.”

“For Rigid boards I really don’t need a Drawing and can get the fabrication vendor where he’s going based on material and a starting point. But Flex is different, often called Black Magic in the business.”

Bob Parent, BAE Systems

Real World Advice from Industry Experts

Is it Dynamic Flex or Flex for Install – Be sure to select best suited materials

Book-Bind-Flex - If you require a high layer talk to your fabricator about Book-Bind Flexes.

Anchors - Be sure to add anchor tie points (similar to a thermal relief) from any solder pad to reduce opportunity for pad lift during assembly.

How Flexible is the flex - Be careful to not overspec the copper weight of a flex.

Reduce Adhesives - Reduce coverlay and adhesives in bend radius areas if possible. Reducing the amount of adhesive and or coverlay in a bend radius will keep the material more flexible in that area.

Cut-outs - Use cut-outs to keep the flex more pliable. (Think of a net or chain-link fence)

Consider The Assembly Process - Consider the use of solder pallet to support any SMT reflow that may be needed.

Inside Corners – add a radius to all inside corners (.030” min) to reduce tearing of flex

Modeling: - model or “paper doll” to test proper alignment, orientation and bend areas

Real World Advice from Industry Experts

· Know the construction and the fab process

· Make sure fab. note call-outs are good, based on preliminary review

· Know your manufacturers capabilities matrix.

· Have a mfg/eng review early in the design to ensure it’s buildable with in-stock material &process.

· Mechanically reduce all stress and tear points.

· Via locations are critical avoid placing them close to fold, stress or tear point

· Avoid layer to layer cross talk by offsetting traces on adjacent layers

· Add stiffeners when required make them larger to avoid cracks or stress points

· Learn how a book binder fold works

· Route with smoothing or curved lines avoid sharp bends

· Know how it will bend and if a fold could become a crease which can break the trace

· Make pad patterns bigger to add stress relief

· Add a tear stop piece of dead metal for mechanical rigidity Mike Creeden, San Diego PCB

Thank You

Thank you!

Please contact me for additional information!

Tara DunnOmni PCB, LLCtarad@omnipcb.com507-332-9932www.omnipcb.comwww.pcbadvisor.com

Thank You!

Thanks for your Attention!

Questions?