Technical Data
November 2013
3M
™
Anisotropic Conductive Film 7371
Product Description
3M™ Anisotropic Conductive Film (ACF) 7371 is a heat-
bondable, electrically conductive adhesive film. The
unbonded film is slightly tacky at room temperature and
consists of a thermoset-elastomer and thermoplastic
adhesive matrix randomly loaded with conductive
particles. These particles allow interconnection of circuit
lines through the adhesive thickness, but are spaced far
enough apart for the product to be electrically insulating
in the plane of the adhesive. Application of heat and
pressure causes the adhesive to flow and to bring the
circuit pads into contact by trapping the conductive
particles. The adhesive rapidly cross-links at modest
bonding temperature and pressure. 3M ACF 7371 may
be used to bond a flexible printed circuit to another
flexible printed circuit or to a plastic touch screen or
plastic flat panel display device.
Typical Physical Properties and
Performance Characteristics
Note:
The following technical information and data should
be considered representative or typical only and
should not be used for specification purposes.
Design Requirements
Property
Minimum Space Between
Conductors
Minimum Pitch
Minimum Pad Area
Value
100
(4)
200
(8)
0.1
(160)
Units
micron
(mil)
micron
(mil)
sq. mm
(sq. mil)
Ambient Physical Properties
Property
(1)
Interconnect
Resistance
Interconnect
Resistance
Peel Strength
Test Substrates
Flex-to-
PC board
(2)
Flex-to-
Ag-Ink/PET
(4)
Flex-to-
ITO/PET
(5)
Flex-to-
Ag-Ink/PET
(4)
Flex-to-
bare-PET
(7)
Value
Test Method
< 20 mOhms 3M TM-2314
(3)
< 20 mOhms 3M TM-2314
(3)
> 700 gf/cm 3M TM-2313
(6)
> 600 gf/cm 3M TM-2313
(6)
> 900 gf/cm 3M TM-2313
(6)
Construction
General Properties
Property
Adhesive Type
Particle Type
Particle Size
Liner Type
Adhesive Thickness
Liner Thickness
Value
Thermosetting Type
Gold-Coated Polymer
10 micron
Polyester Film with Silicone Release
25 micron
50 micron
(3)
(1)
Peel Strength
Peel Strength
(2)
(4)
(5)
(6)
(7)
For a given application, values may differ depending on particular substrate
material or type of circuitry.
Measured for gold/nickel/copper polyimide flex circuits bonded to printed
circuit board. Contact overlap area was 0.38 sq. mm. Pad pitch was 500
microns.
3M internal test method TM-2314 based on IPC 650 - Section 2.6.24. The
flex has the shorting strap located near the bond-line to approximate a
4-wire test structure and eliminate most extraneous resistance in the
measurement due to the circuit lines.
Measured for gold/nickel/copper polyimide flex circuits bonded to silver-
ink/indium-tin-oxide/polyester. Contact overlap area was 2.0 sq. mm. Pad
pitch was 2 mm.
Measured for gold/nickel/copper polyimide flex circuits bonded to indium-
tin-oxide/polyester. Flex circuit pitch was 500 microns.
3M internal test method TM-2313 based on IPC 650 - Section 2.4.9.1.
Measured for gold/nickel/copper polyimide flex circuits bonded to bare
polyester. Flex circuit pitch was 2 mm.
3M
™
Anisotropic Conductive Film 7371
Typical Physical Properties and
Performance Characteristics
(continued)
Note:
The following technical information and data should
be considered representative or typical only and
should not be used for specification purposes.
Ambient Physical Properties – Peel Strength
(8)
Reliability Performance – Peel Strength
(11)
Test Conditions
100°C x 1000 hrs
-40°C to 85°C x 1000 cycles
85°C / 85% r. h. x 1000 hrs
Peel Strength
(gf/cm)
3M TM-2313
(12)
> 500
> 500
> 500
Boxplot of Peak Peel Strength vs. Bonding Temperature
1400
1200
Peak Peel Strength (gf/cm)
PI Flex - to - Glass
All Bonds 15sec and 3MPa
Initial Peel Values
Assembly Process Techniques
Assembly Process
A source of heat and pressure, such as a thermo-compression
(hot bar) bonder is required for use of 3M™ Anisotropic
Conductive Film 7371. Several commercially available
models exist; a list of vendors can be obtained by calling the
toll free number on the back of this Technical Data Sheet.
1000
800
600
400
200
0
147
160
180
190
Temperature ( C)
200
210
Bonding of 3M ACF 7371 requires a three-part procedure:
Tacking the film to one substrate (pre-tacking)
Removing the release liner
Bonding the first substrate to the second substrate.
A pre-tacking temperature of 90°C under a pressure of
about 10 kg/cm
2
should be used (see Table below).
For
automated ACF application:
Set the ACF pretacking
equipment to deliver the conditions provided in the
Tacking and Bonding Conditions Table below. Slight
adjustment to these conditions may be necessary for each
application or for different types of circuitry.
For manual
ACF application:
Cut the adhesive to the size of the flex
circuit. Place the adhesive on the flex and set flex on hot
plate at setpoint up to 90°C. Use roller to press adhesive
onto the flex. After allowing flex and adhesive to cool,
remove liner.
Reliability Performance – Electrical Contact
(9)
Test Conditions
100°C x 1000 hrs
-40° to 85°C x 1000 cycles
85°C / 85% r. h. x 1000 hrs
Interconnect Resistance
(mOhms)
3M TM-2314
(10)
< 100
< 100
< 100
(8)
Measured for gold/nickel/copper polyimide flex circuits bonded to glass.
Pad pitch was 100 microns.
Measured for gold/nickel/copper polyimide flex circuits bonded to Ag-Ink/
indium-tin-oxide/polyester. Contact overlap area was 2.0 sq. mm. Pad pitch
was 2 mm. Also, measured for gold/nickel/copper polyimide flex circuits
bonded to printed circuit board. Overlap area was 0.38 sq. mm. Pad pitch
was 500 microns.
3M internal test method TM-2314 based on IPC 650 - Section 2.6.24. The
flex has the shorting strap located near the bond-line to approximate a
4-wire test structure and eliminate most extraneous resistance in the
measurement due to the circuit lines.
(11)
Measured for gold/nickel/copper polyimide flex circuits bonded to Ag-Ink/
ITO/polyester. Contact overlap area was 2.0 sq. mm. Pad pitch was 2 mm.
3M internal test method TM-2313 based on test method IPC 650 - Section
2.4.9.1.
(9)
(12)
(10)
(2)
3M
™
Anisotropic Conductive Film 7371
Assembly Process Techniques
(continued)
Tacking and Bonding Conditions
Temperature ( C)
Procedure
Tacking Conditions
Temperature
(13)
Pressure
Time
Bonding Conditions
Temperature
(13)
Pressure
Time
(14)
Conditions
60 - 90°C
1 - 15 kg/cm
2
~1 sec
140 to 170°C
10 - 20 kg/cm
2
10 - 20 sec
200
180
160
140
120
100
80
60
40
20
0
0
2
4
6
8
10
12
14
16
170 C x 15 sec
140 C x 10 sec
Thermode
Released
Final bonding must be done under heat and pressure,
with a typical desirable bond line temperature that
reaches at least 140°C after 10 seconds at a pressure
of at least 10kg/cm
2
(see Table above). This has been
achieved using a total bond time of 10-20 seconds
where over the first 3-5 seconds the adhesive ramps
quickly to near the target temperature and over the last
5-17 seconds the temperature reaches between 140°C
and 170°C.
(15)
A plot of the temperature vs. time profile is
shown in Figure 1. Electrical contact between the circuits
is typically achieved shortly after the thermode is pressed
against the parts. Additional time at temperature is
necessary to cross-link the thermoset-elastomer material
to generate peel strength and the ultimate reliability.
Bond times may vary depending upon the substrates to
be bonded. (Optionally, for maximum mechanical and
electrical performance, the pressure may be maintained
while cooling to below 100ºC. This increases the total
bond time. The time required to drop adhesive bond-line
temperature below 100ºC is highly dependent on the
bonding equipment used.)
(13)
Time (sec)
Figure 1. Graph of ACF temperature vs. time profile
showing typical examples of bonding cycle.
Predicted 3M™ ACF 7371 Cross-link Reaction
140.0°C
150.0°C
160.0°C
170.0°C
180.0°C
190.0°C
100%
90%
80%
Conversion (%)
70%
60%
50%
40%
30%
20%
10%
0%
0
10
20
30
Time (sec)
40
50
60
Figure 2. Graph of predicted cross-link reaction
compared with bonding temperature and time.
A comparison of the predicted level of cross-link reaction
across a range of bonding temperature and bonding time
is shown in Figure 2.
Repair
Bonds made with 3M™ Anisotropic Conductive Film
7371 may be repairable. The method for successful
rework can show considerable variation for different
design applications, process parameters, and
equipment capabilities. Contact your local Tech Service
Representative for further information.
Temperature measured in the adhesive. Thermode set points will be higher
and will depend upon the substrate materials and bonding equipment. A
typical set-up for tacking is a setpoint temperature of 125ºC. Typical set-up
for a flex circuit to polyester touch screen bond is a thermode temperature of
250ºC and bonding time of at least 10 seconds (see next note).
The required minimum bonding temperature is usually reached at the
endpoint of bonding time. The optimum bonding temperature and time may
be different depending on customer application and design. Also, it may
be desirable to hold pressure while cooling to below 100ºC for maximum
performance.
Bonding temperature up to 190°C has been shown to be acceptable for
3M™ Anisotropic Conductive Film 7371.
(14)
(15)
(3)
3M
™
Anisotropic Conductive Film 7371
Assembly Process Techniques
(continued)
Storage
The 3M™ Anisotropic Conductive Film 7371 should be kept frozen in the original airtight shipping bag and stored at
temperatures ≤ 2°C. The product should be allowed to warm to room temperature for approximately 30 minutes prior
to use to prevent moisture condensation on the film. Whenever possible, 3M ACF 7371 should be kept away from high
humidity environments as absorbed water can lead to moisture volatilization producing bubbles during heat bonding or
gradual degradation of the product. The 3M ACF 7371 can be held at room temperature for product utilization provided
the cumulative room temperature shelf life of 4 weeks is not exceeded.
Shelf Life Data
Storage Environment
Freezer (< 2°C)
Room Temperature
Value
12 months
4 weeks
Product Selection Guide
Flex Type
Connection Type
Pitch and Space Requirements
Minimum
Space
Between
Conductors
100 micron
250 micron
100 micron
100 micron
70 micron
100 micron
50 micron
Silver Ink
on Polyester
ACF 5363
ACF 7303
ACF 7371
ACF 7371-20
ACF 7376-10
ACF 7376-30
ACF 7379
1
2
Gold/Copper
on Polyester
Gold/Copper
on Polyimide
X
Flex to
Glass
Flex to
Plastic
Device
Flex to
PCB
X
Flex to
Flex
X
X
X
X
Minimum
Pad
Area
0.15 sq. mm
0.75 sq. mm
0.10 sq. mm
0.50 sq. mm
0.10 sq. mm
0.50 sq. mm
0.05 sq. mm
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1
X
X
X
X
X
X
2
X
X
X
X
X
X
X
X
X
Tested only for silver frit; not suitable for ITO traces.
Suitable for silver ink traces only; not suitable for ITO traces.
(4)
3M
™
Anisotropic Conductive Film 7371
Technical Information
The technical information, recommendations and other
statements contained in this document are based upon
tests or experience that 3M believes are reliable, but the
accuracy or completeness of such information is not
guaranteed.
Warranty, Limited Remedy, and Disclaimer
Unless an additional warranty is specifically stated on the
applicable 3M product packaging or product literature,
3M warrants that each 3M product meets the applicable
3M product specification at the time 3M ships the
product. 3M MAKES NO OTHER WARRANTIES OR
CONDITIONS, EXPRESS OR IMPLIED, INCLUDING, BUT
NOT LIMITED TO, ANY IMPLIED WARRANTY OR CONDITION
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE OR ANY IMPLIED WARRANTY OR CONDITION
ARISING OUT OF A COURSE OF DEALING, CUSTOM OR
USAGE OF TRADE. If the 3M product does not conform to
this warranty, then the sole and exclusive remedy is, at
3M’s option, replacement of the 3M product or refund of
the purchase price.
Product Use
Many factors beyond 3M’s control and uniquely within
user’s knowledge and control can affect the use and
performance of a 3M product in a particular application.
Given the variety of factors that can affect the use and
performance of a 3M product, user is solely responsible
for evaluating the 3M product and determining whether
it is fit for a particular purpose and suitable for user’s
method of application.
Limitation of Liability
Except where prohibited by law, 3M will not be liable for
any loss or damage arising from the 3M product, whether
direct, indirect, special, incidental or consequential,
regardless of the legal theory asserted, including
warranty, contract, negligence or strict liability.
Electronics Markets Materials Division
3M Center, Building 225-3S-06
St. Paul, MN 55144-1000
1-800-251-8634 phone
651-778-4244 fax
www.3M.com/electronics
3M is a trademark of 3M Company.
Please recycle. Printed in U.S.A.
© 3M 2013. All rights reserved.
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(5)
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