Materials Reference

Material
Specifications

Base materials, conductors, surface finishes, and coverlayer options — from KAPTON polyimide to adhesiveless LCP constructions.

Materials Reference

Flexible Circuit Material Specifications

Material selection is critical to circuit performance — our engineers recommend the optimal stack for your application.

Base Dielectric Materials
Material	Type	Key Properties	Best For
KAPTON® Polyimide	Adhesive-based	Exceptional thermal stability, chemical resistance, 500M+ flex cycles	General flex, dynamic flexing — most common
Adhesiveless Polyimide	Direct bonded	Thinner, better thermal, finer trace capability	High-density, medical, aerospace — thin profile
LCP	Specialty	Excellent HF performance, low moisture absorption	High-frequency RF/microwave, precision circuits
Polyester (PET)	Low cost	Lower thermal rating than polyimide	Non-demanding static applications, cost-sensitive
FR-4	Rigid zones	Glass epoxy, rigid	Rigid zones in rigid-flex, stiffeners

Conductor Materials
Material	Form	Properties	Best For
Rolled Annealed Copper (RA)	Standard	Best flexibility, high ductility	Dynamic applications, maximum flex life
Electrodeposited Copper (ED)	Standard	Fine grain, excellent for fine-line etching	Fine trace/space, high-density circuits
Beryllium Copper	Specialty	High strength, spring properties	Contact springs, medical, aerospace
Stainless Steel	Specialty	High strength, corrosion resistance	Structural function, corrosive environments
Cupronickel	Specialty	Corrosion resistance, thermal EMF	Thermocouple sensing, corrosion-resistant apps

Surface Finishes
Finish	Type	Properties	Best For
ENIG (Electroless Nickel/Immersion Gold)	Standard	Flat, solderable, wire bondable	SMT assembly, wire bonding, general
Selective Gold Plating	Premium	Hard gold at contacts, other finish at pads	ZIF contacts, edge fingers, high-wear
Immersion Silver	RoHS	Flat, excellent solderability	RoHS programs, fine-pitch SMT
Tin-Lead (63/37)	Standard	Excellent solderability, low cost	Standard solder, non-RoHS programs
Multiple Finishes	Specialty	Gold + ENIG on same circuit	Medical, aerospace — mixed termination

Coverlayer Options
Type	Material	Properties	Application
Bonded Polyimide Coverlayer	Polyimide + adhesive	Most common, robust	General flex protection, dynamic zones
Photoimageable Covercoat	Liquid photopolymer	Fine opening definition, tight registration	Fine-pitch SMT, small opening geometries
LPI Solder Mask	Photo-imageable polymer	Industry standard for rigid zones	Rigid portions of rigid-flex circuits
No Coverlayer	—	Bare copper exposed	Specific impedance or contact requirements

30+ years of flex circuit expertise. Quick turnarounds. ISO 9001 certified. ITAR registered.

30+ years manufacturing precision flexible circuits.
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