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Flex PCB Materials: PI, PET, LCP, Copper & Coverlay

Choose a material system, not just a film

A substrate name alone does not define a circuit's thermal or mechanical performance. Record the film grade, copper type, adhesive system and protective layers. Review operating conditions separately from soldering and assembly exposure.

Compare PI, PET and LCP

Polyimide is a common starting point for flexible circuit construction. PET can be considered for suitable cost-sensitive processes, but its assembly and temperature limits need grade-specific review. LCP and low-loss PI systems are candidates for some RF designs; compare frequency-dependent data, process availability and the complete stackup.

Copper and repeated bending

Rolled-annealed and electrodeposited copper have different material structures and processing histories. For repeated motion, use the foil supplier's data and a qualified bend-life test. Copper thickness, plating, grain direction and strain in the actual bend also matter.

Coverlay and reinforcement

A film coverlay bonds a dielectric film over the circuit. Flexible solder mask is a different protective system. A PI or FR-4 stiffener supports selected regions such as a connector termination; keep its transition out of the moving bend region.

Make the requirements reviewable.

Define	Include in the review	Why it matters
Mechanical duty	Installed shape, bend location, motion and cycle target	Distinguishes installation bending from service fatigue
Construction	Layer order, copper, film, adhesive and coverlay	Establishes finished thickness and material compatibility
Interfaces	Connector thickness, pad finish and local reinforcement	Controls fit, assembly support and contact reliability
Acceptance	Dimensions, electrical test and applicable standard revision	Creates an agreed basis for inspection and quotation

CONTINUE THE DESIGN REVIEW

Connect the decisions.

Discuss your build requirements →

YOUR NEXT STEP

Bring the requirements.
Start the conversation.

Tell us what the circuit needs to do, how it will bend and when you need it. A complete build brief makes a quote easier to evaluate.

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Preparing files?

Include Gerber and drill data, a fabrication drawing and stackup notes. Put related files in one ZIP. Add a BOM and placement file when assembly is required.