Flex Cable Design Best Practices Part 2

Tips to Minimize Avoidable Errors and Premature Circuit Failure 

Following best practices for flex cable design will help you avoid costly errors.  By balancing mechanical and electrical requirements at the circuit design stage, we help our manufacturing partners achieve optimal performance. From medical devices to aerospace applications, telecommunications, industrial engineering equipment, semiconductor testing and manufacturing equipment, our turnkey solutions lower your time and cost of production.

How Can Flex Cable Design Best Practices Reduce Costly Errors?

Follow These 4 Recommendations

1. Balance circuitry to reduce mechanical stress: This is a rule of thumb for all types of flex circuit constructions. Where weight is not a factor, we recommend using a balanced geometry of copper and adjusting width of flex areas to avoid large void areas that are typically susceptible to high stress.
2. Use ground plane design for mechanical and electrical stability: Solid copper planes are easy to make and provide more controlled signals. Our flex circuit engineering experts suggest using a cross-hatched design and silver inks for less weight and improved flexibility. Always avoid placement of vias within the bend area.
3. Design symmetry lowers risk of stress build up: In our experience, even the smallest imperfections in the flex area are likely to cause premature circuit failure. Here are some precautions you can take to reduce this risk:
   • Use straight conductors (or rounded corners) and avoid surface plating in the dynamic flex area
   • Ensure that conductors run perpendicular to the direction of the bend
   • Select 1 ounce rolled annealed copper and thin, adhesiveless dielectric materials for better performance
   • Opt for a loose leaf construction with a symmetrical stack up
4. Important drawing considerations:

• Manufacturing specification including PCB Class, Type and Use
• Raw materials specifications (optional but recommended)
• Metal finish definition and (if applicable) specifications
• Drilling information that includes number of drilled holes per each diameter and finished hole size requirements (data to define hole locations should be digital)
• Dimensional information: Identify all critical dimensions to a datum point.
• Define the rigid to flex interfaces. Typical outline tolerances are +/- .005” for rigid edges, +/- .003” for flex laser routed edges.
• Stiffener location, side, thickness and bonding requirements
• Board markings: location, format and (if applicable) specifications
• If an assembly pallet or break-away array are defined, a dimensional drawing is required
• Stackup or a board construction and layer order chart, this should show which layers are rigid and which layers are flex, include copper weights and dielectric thicknesses
• ITAR requirements or other IP control restrictions

We are happy to provide a manufacturing feasibility assessment of your flex cable design along with a customized circuit assembly solution.

Flex Cable Design Best Practices in our ITAR-Certified Facility

Rely on our turnkey solutions to speed up manufacturing and help you reach your customers before the competition. Our new 13,000-sq. ft. ESD-controlled facility is equipped with the latest PCB assembly equipment to double the volume of our output and reduce your prototype development time by 50%. We provide complete flex circuit assembly services from layout review to material procurement, assembly, testing, warehousing and shipping—and all of this is fully managed in-house to maintain strict quality control and timely delivery.