Flex Circuit Material Properties

Below you will find a chart depicting the typical properties of dielectric material used in flexible printed circuit boards. You can also see our blog post on adhesive and adhesiveless polyimide flex core material types for additional information.

Typical Properties of Dielectric Material for Flexible Printed Circuitry

Property (Typical)	Units	Polymide	Polymide (Adhesiveless)	Polyester
Representative Trade Name		KAPTON	KAPTON	MYLAR
Physical
Thickness Range	mil	0.5 to 5	1-6	2-5
Tensile Strength (@25°C)	psi	25,000	50,000	20,000 to 35,000
Break Elongation	%	70	50	60 to 165
Tensile Modulus (@25°C)	100,000 psi	4.3	.7	5
Tear Initiation Strength	lb/in	1000	700-1200	1000 to 1500
Tear Propagation Strength	g/mil	8	20	12 to 25
Chemical
Resistance to:
Strong Acids		Good	Good	Good
Strong Alkalis		Poor	Good	Poor
Grease and Oil		Good	Good	Good
Organic Solvents		Good	Good	Good
Water		Good	Good	Good
Sunlight		Good	Good	Fair
Fungus		Non-nutrient	Non-nutrient	Non-nutrient
Water Absorption	% (24 hours)	2.9	0.8	<0.8
Thermal
Service Temperature (min/max)	degree C	-125/+200	-125/+200	-60/+105
Coefficient of Thermal Expansion (@22°C)	PPM/degree C	20	20	27
Change in Linear Dimensions (100°C, 30min)	%	<0.3	0.04-0.02	<0.5
Electrical
Dielectric Constant (ASTM D150) 1MHz		3.4	3.4	3
Dissipation Factor (ASTM D150) 1MHz		0.01	0.003	0.018
Dielectric Strength (ASTM D149) @ 1 mil thickness Volume Resistivity (ASTM D257)	V/mil ohm-cm	6000 1.0E+16	6000 1.0E+16	3400 1.0E+16

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Choose the Right Material for Your Flex Circuit Project

Compare tensile strength, thermal properties, and more with our comprehensive chart. Make informed decisions for optimal performance. Contact us to discuss your specific needs today.

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