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.
Technical Data November 2013
Construction
General Properties
Property Value
Adhesive Type Thermosetting Type
Particle Type Gold-Coated Polymer
Particle Size 10 micron
Liner Type Polyester Film with Silicone Release
Adhesive Thickness 25 micron
Liner Thickness 50 micron
Property(1) Test Substrates Value Test Method
Interconnect Flex-to- < 20 mOhms 3M TM-2314(3)
Resistance PC board(2)
Interconnect Flex-to- < 20 mOhms 3M TM-2314(3)
Resistance Ag-Ink/PET(4)
Peel Strength Flex-to- > 700 gf/cm 3M TM-2313(6)
ITO/PET(5)
Peel Strength Flex-to- > 600 gf/cm 3M TM-2313(6)
Ag-Ink/PET(4)
Peel Strength Flex-to- > 900 gf/cm 3M TM-2313(6)
bare-PET(7)
Ambient Physical Properties
(1) For a given application, values may differ depending on particular substrate
material or type of circuitry.
(2) 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.
(3) 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.
(4) 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.
(5) Measured for gold/nickel/copper polyimide flex circuits bonded to indium-
tin-oxide/polyester. Flex circuit pitch was 500 microns.
(6) 3M internal test method TM-2313 based on IPC 650 - Section 2.4.9.1.
(7) Measured for gold/nickel/copper polyimide flex circuits bonded to bare
polyester. Flex circuit pitch was 2 mm.
Property Value Units
Minimum Space Between 100 micron
Conductors (4) (mil)
Minimum Pitch 200 micron
(8) (mil)
Minimum Pad Area 0.1 sq. mm
(160) (sq. mil)
Design Requirements
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.
Reliability Performance – Electrical Contact(9)
Interconnect Resistance
Test Conditions (mOhms)
3M TM-2314(10)
100°C x 1000 hrs < 100
-40° to 85°C x 1000 cycles < 100
85°C / 85% r. h. x 1000 hrs < 100
Peel Strength
Test Conditions (gf/cm)
3M TM-2313(12)
100°C x 1000 hrs > 500
-40°C to 85°C x 1000 cycles > 500
85°C / 85% r. h. x 1000 hrs > 500
Reliability Performance – Peel Strength(11)
(2)
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.
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/cm2 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.
(8) Measured for gold/nickel/copper polyimide flex circuits bonded to glass.
Pad pitch was 100 microns.
(9) 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.
(10) 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.
(12) 3M internal test method TM-2313 based on test method IPC 650 - Section
2.4.9.1.
Ambient Physical Properties – Peel Strength(8)
Temperature (°C)
Peak Peel Strength (gf/cm)
1400
1200
1000
800
600
400
200
0
147 180160 190 200 210
PI Flex - to - Glass
All Bonds 15sec and 3MPa
Initial Peel Values
Boxplot of Peak Peel Strength vs. Bonding Temperature
3M™ Anisotropic Conductive Film 7371
Assembly Process Techniques (continued)
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/cm2 (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.)
Figure 1. Graph of ACF temperature vs. time profile
showing typical examples of bonding cycle.
Figure 2. Graph of predicted cross-link reaction
compared with bonding temperature and time.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 10
Conversion (%)
Time (sec)
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
20 30 40 50 60
(3)
(13) 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).
(14) 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.
(15) Bonding temperature up to 190°C has been shown to be acceptable for
3M™ Anisotropic Conductive Film 7371.
Tacking and Bonding Conditions
Procedure Conditions
Tacking Conditions
Temperature(13) 60 - 90°C
Pressure 1 - 15 kg/cm2
Time ~1 sec
Bonding Conditions
Temperature(13) 140 to 170°C
Pressure 10 - 20 kg/cm2
Time(14) 10 - 20 sec
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.
3M™ Anisotropic Conductive Film 7371
Thermode
Released
170°C x 15 sec
140°C x 10 sec
200
180
160
140
120
100
80
60
40
20
0
Temperature (°C)
0 2 4 6 810 12 14 16
Time (sec)
(4)
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 Value
Freezer (< 2°C) 12 months
Room Temperature 4 weeks
Assembly Process Techniques (continued)
Flex Type Connection Type Pitch and Space Requirements
Minimum
Flex to Space Minimum
Silver Ink Gold/Copper Gold/Copper Flex to Plastic Flex to Flex to Between Pad
on Polyester on Polyester on Polyimide Glass Device PCB Flex Conductors Area
ACF 5363 X X X 100 micron 0.15 sq. mm
ACF 7303 X X X X1 X2 X X 250 micron 0.75 sq. mm
ACF 7371 X X X X X X 100 micron 0.10 sq. mm
ACF 7371-20 X X X X X X 100 micron 0.50 sq. mm
ACF 7376-10 X X X X X X X 70 micron 0.10 sq. mm
ACF 7376-30 X X X X X X X 100 micron 0.50 sq. mm
ACF 7379 X X X X 50 micron 0.05 sq. mm
1Tested only for silver frit; not suitable for ITO traces.
2Suitable for silver ink traces only; not suitable for ITO traces.
Product Selection Guide
3M™ Anisotropic Conductive Film 7371
3M™ Anisotropic Conductive Film 7371
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.
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.
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.
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.
(5)
3M is a trademark of 3M Company.
Please recycle. Printed in U.S.A.
©3M 2013. All rights reserved.
60-5002-0443-7
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
