No-Flo® and Lo-Flo® Specialty Prepreg

Isola offers a FR406N family of no-flow and low-flow prepregs consisting of proprietary resin systems specifically formulated for optimal performance in bonding applications requiring minimal resin flow and consistency in lamination.

Thermal Performance

Tg: 170°C
Td: 300°C

Electrical Performance

Dk: 4.3
Df: 0.025

Industry Approvals

IPC-4101 /21 /24 /26
UL - File Number E41625

FR406 No-Flo and FR406 Lo-Flo® products bring the fabricator specific thermal characteristics appropriate for use in multilayer rigid-flex applications.



Product Features

  • Industry Recognition
    • UL File Number: E41625
    • RoHS Compliant
  • Processing Advantages
    • Machinable by steel rule die or punch
    • Consistent dielectric spacing
    • Complete encapsulation of non-planar surfaces
    • Cure and form bond at low temperatures
    • Allows for lamination at non-uniform pressures
  • No-flow Prepreg
    • Adhesion to wide range of materials
    • Flex films – (Mylar®, Kapton®, etc.)
    • Treated or untreated copper
    • Plated metals (tin, solder, nickel, etc.)
    • Conventional laminate surfaces

Production & Manufacturing

Currently manufactured in Asia, North America, Europe

Product Availability

  • Standard Material Offering: Prepreg
    • Roll or panel form
    • Tooling of prepreg panels
  • Glass Fabric Availability
    • E-glass
Property Typical Value Units Test Method
Metric (English) IPC-TM-650 (or as noted)
Pressed Thickness
A. 106
B. 1080
0.043 ±0.0008 (1.7 ±0.3)
0.069 ±0.0008 (2.7 ±0.3)
mm (mil)
Resin Content
A. 106
B. 1080
65 ±1.5 %
Resin Flow Testing
A. 106
B. 1080
Modified Circle Flow
A. 106
B. 1080
Glass Transition Temperature (Tg) by DSC 170 °C 2.4.25C
Cure Temperature Recommended for Full Cure 185 °C
Min. for Functional Bonding 165 °C
Z-Axis CTE Pre-Tg 75 ppm/°C 2.4.24C
X/Y-Axis CTE Pre-Tg 17/20 ppm/°C 2.4.24C
Thermal Conductivity .30 W/m·K ASTM E1952
Thermal Stress 10 sec @ 288ºC (550.4ºF)
A. Unetched
B. Etched
Pass Pass Visual
Electric Strength (Laminate & laminated prepreg) 70 (1750) kV/mm (V/mil)
Peel Strength Standard profile copper >>> After thermal stress 1.75 (10.0) N/mm (lb/inch) 2.4.8C
Flammability (Laminate & laminated prepreg) V-0 Rating UL 94
The data, while believed to be accurate and based on analytical methods considered to be reliable, is for information purposes only. Any sales of these products will be governed by the terms and conditions of the agreement under which they are sold.


A: Initial release - 4/17
B: Added SI units to Electrical Strength and Peel Strength - 3/22
C: corrected z-Axis CTE value to Pre-Tg - 05/23

Resource Title & Summary Date Updated
Isola Laminate Outgassing Data Properties 12/17/2019
FR406N Processing Guide 06/23/2020
FR406N Prepreg Safety Data Sheet 01/22/2024
FR406N Prepreg RoHS Declaration 11/01/2022