38NPOLYIMIDE LOW-FLOW PREPREG
38N is an improved polyimide low-flow prepreg suitable forbonding multilayer polyimide rigid-flex, attaching heat sinks topolyimide MLBs, or other applications where minimal anduniform resin flow is required.

Features:• Novel chemistry ensuring faster and more uniform resin cure forminimal and consistent resin flow, preventing excessive flow into
clearance/relief areas• Improved bond strength to Kapton® polyimide of up to 50%
compared with conventional polyimide low-flow or no-flow products• Tg = 200°C and expansion characteristics typical of polyimide
greatly improves PTH reliability• Curable at temperatures as low as 350°F (177°C)• Excellent thermal stability• Improved bond strength to copper and other metals for excellent
performance in heat sink bonding applications• Electrical and mechanical properties meeting the requirementsof IPC-4101/42• Compatible with lead-free processing• RoHS/WEEE compliant

Typical Applications:• Bonding multilayer polyimide rigid-flex• Attaching heat sinks to polyimide MLBs
• Other applications where minimal and uniform resin flow is required

Typical Properties:
Property38NUnits

Value

Test Method-4.25

IPC TM-650 2.5.5.3
IPC TM-650 2.5.5.9-0.010

IPC TM-650 2.5.5.3
IPC TM-650 2.5.5.9

MΩ-cm
MΩ-cm

8.2 x 107
4.7 x 109

IPC TM-650 2.5.17.1
IPC TM-650 2.5.17.1

MΩ
MΩ
Volts/mil (kV/mm)
kV
sec

4.4 x 106
1.2 x 109
1600 (63.0)

IPC TM-650 2.5.17.1
IPC TM-650 2.5.17.1
IPC TM-650 2.5.6.2
IPC TM-650 2.5.6
IPC TM-650 2.5.1

°C
°C

200

IPC TM-650 2.4.24
IPC TM-650 2.4.25

°C°C
min
min
min
ppm/°C

311330505317

IPC TM-650 2.3.41
IPC TM-650 2.3.41
IPC TM-650 2.4.24.1
IPC TM-650 2.4.24.1
IPC TM-650 2.4.24.1
IPC TM-650 2.4.41

ppm/°Cppm/°C%

54157
1.5

IPC TM-650 2.4.24
IPC TM-650 2.4.24
IPC TM-650 2.4.24

lb/in (N/mm)
lb/in (N/mm)
lb/in (N/mm)

8.5 (1.5)

IPC TM-650 2.4.8
IPC TM-650 2.4.8.2
IPC TM-650 2.4.8

lb/in (N/mm)
lb/in (N/mm)
Mpsi (GPa)kpsi (MPa)kpsi (MPa)kpsi (MPa)

5.9 (1.0)
5.2 (0.9)
2.1 (14.5)
60 (414)32 (221)-0.18

ASTM D-3039

Water Absorption%<1.0

IPC TM-650 2.6.2.1

Specific Gravity

g/cm3

Thermal Conductivity

W/mK0.3

ASTM E1461

Flammabilityclass

Meets V-O

UL-94

1. Electrical Properties
Dielectric Constant (may vary with Resin %)@ 1 MHz@ 1 GHz
Dissipation Factor@ 1 MHz@ 1 GHz
Volume Resistivity
C96/35/90
E24/125
Surface Resistivity
C96/35/90
E24/125
Electrical Strength
Dielectric Breakdown
Arc Resistance125

2. Thermal Properties
Glass Transition Temperature (Tg)
TMADSC
Decomposition Temperature (Td)
Initial5%T260
T288
T300
CTE (x,y)CTE (z)< Tg> Tgz-axis Expansion (50-260ºC)

3. Mechanical Properties
Peel Strength to Copper (1 oz/35 micron)
After Thermal Stress
At Elevated Temperatures
After Process Solutions
Peel Strength to Kapton
As Received
After Solder
Young’s Modulus
Flexural Strength
Tensile Strength
Compressive Modulus
Poisson’s Ratio (x, y)

IPC TM-650 2.4.18.3
IPC TM-650 2.4.4
IPC TM-650 2.4.18.3
ASTM D-695

4. Physical Properties
ASTM D792 Method A

Results listed above are typical properties, provided without warranty, expressed or implied, and without liability. Properties may vary, depending on design and application. Arlon reserves
the right to change or update these values.

Availability:
Arlon Part
NumberGlass Style

Resin %

Flow Range

PressedThickness

38N0666106

66%

70 - 120 mils

1.9 mils

38N80601080

60%

70 - 120 mils

2.9 mils

Recommended Process Conditions:Because of varying storage conditions, it is recommended that 38N prepreg be dried at 29”(736mm) Hg for 12 to 24 hours.
38N Low-Flow prepreg is very process tolerant. It laminates well with either a cold platenpress start or with a hot start. Vacuum or vacuum assist lamination is recommended for theremoval of moisture and air. Low-Flow products do not displace air voids as well as standard
prepregs, and vacuum will help assure a void-free final product.
Lamination Cycle:
1)

Vacuum draw down the package for 30 minutes at <29” (736mm) Hg prior to applying pressurein the press. Maintain the vacuum beyond the set point of the resin, i.e., above 320°F (160°C)

2)

Use a platen temperature in the range of 360°F - 380°F (182°C - 193°C). Tg at epoxy curetemperature will be 200°C.

3)

Control the heat rise to about 8°F - 12°F per minute (4°C – 6°C) between 200°F and 300°F(93°C and 149°C)

4)

Use a pressure of 180 to 350 psi (12.6 to 24 kg/sq.cm), depending on panel size andcomplexity. Following are recommended pressures relative to panel size to use as starting
points:Panel Size

Pressureincm

psikg/sq cm

9 x 1222 x 30

1801312 x 1230 x 30

2001412 x 1830 x 46250

1816 x 1840 x 46

290

2018 x 24

46 x 61330

2324 x 24

61 x 61350

25

Cure time is 90 minutes at temperature.
The subsequent processing should be the same as those normally used for rigid-flex PCBs.

38N
Optimal processing requirements may vary depending on specific equipment and operating conditions. These recommendations are offered only as a starting point.

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Rev 1.2

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