Advanced Circuit Materials Division
100 N. Dobson Road
Chandler, AZ 85224
Tel: 480-961-1382, Fax: 480-917-5256
www.rogerscorporation.com
Advanced Circuit Materials
Test Procedures
Measurement and Interpretation of Peel Strength
Test
Specimen
6 inch
Diameter
Figure 1. Rotary Drum Test Fixture
At Rogers, peel strength is measured in accordance with IPC test
method 650, 2.4.9, and must meet
industry defined specifications.
Bond is measured as received by
Quality Assurance, using either die
cut specimens 1/2 inch (12.7mm)
wide (Method B), or etched specimens 1/8 inch wide (3.2mm)
(Method A). Peel strength is also
measured after exposure of the
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specimen to solder temperatures,
in order to verify that bond is retained to meet specification [IPC
Methods C - 1/8 inch (3.2mm) and
D - 1/2 inch (12.7mm)]. In addition,
peel strength is measured after
temperature cycling [Methods E 1/8 inch (3.2mm) and F-1/2 inch
(12.7mm)].
Specimens for testing are prepared
at a 4 inch (102mm) length to yield
a minimum of 2 inch (51mm) length
tested. Die cut specimens are precision cut to 1/2 inch (12.7mm) to
eliminate rough edges that will
cause the substrate to tear under
tension and void the result. Etched
specimens are etched to ±0.010
inch (0.254mm) to assure accurate
results. The test specimens are preconditioned to 50% relative humidity and 73°F ±2° (23°C±1°C) in
order to standardize test conditions.
The peel strength test is performed
using a tensile testing apparatus,
with the specimen mounted on a
free-wheeling rotary drum test fixture (Figure 1).
The copper is thermally disbonded
from the first 1/2 inch (12.7mm) of
the laminate specimen. The polyimide side is mounted to the rotary
drum using double faced tape. The
loose copper end is clamped to
the load cell side of the peel testing
device. (At Rogers we use an Instron
Corporation Model 1000 Tensile
Tester for bond testing). The copper is pulled from the polyimide,
peeling at a rate of 2 inches per
minute, speed remaining constant
by varying pull force. Results of the
test are plotted (Figure 2).
The rotary drum is used to maintain
a 90° angle between copper and
polyimide. If the angle changes,
LOAD
Peel strength, or bond, is one of the
most important characteristics of
flexible circuit materials. Laminates
are tested after manufacture, as
are coversheets and bonding films,
both supported and unsupported,
which are laminated to copper foil
under standard conditions for testing. Consistency in peel strength
results indicates that the manufacturing process is under control.
AVERAGE
LOAD
PEEL DISTANCE
Figure 2. Typical Bond Pull Result
the force required to overcome
the bond also changes. Bond specimens are mounted to a rigid backer
of G-10 to prevent the specimen
from partially pulling away, or "tenting" on the drum. When such tenting occurs, the peel angle changes
from 90° so that the peel strength
measurement accuracy is affected. Small, variable deviations
from 90° will result in excessive variation in results. Peel strength is calculated using the following equation:
Average Load (Force)
Peel
Strength = Conductor Width
Peel strength will vary with the
mode of bond failure. Failure mode
inconsistency can result in a wide
range of bond values. There are
several possible bond failure modes
(Figure 3).
Cohesive failure (CA) occurs when the bond to the substrates exceeds the internal strength of the adhesive.
This is typical of lower modulus adhesives, including acrylic based systems such as Rogers R/flex 2000, 2005,
and1005. The CA failure mode usually gives both Method A and Method B peel strength results in the 8 to 10
pounds per linear inch (pli) range. Failure to copper (CU) and failure to polyimide (P) occur when the weakest
bond is between adhesive and either substrate. R/flex 1000 adhesive is a high modulus adhesive which does
not fail cohesively if fully cured. CU and P failure modes give Method A and B peel strength results in the 4.5 to
7.5 pli range, with P lower and CU higher.
®
The adhesive may pull away from either the polyimide or the copper side, or may shift from one to the other.
If this shift is rapidly repeated, the bond fails in a "zipper" (Z) mode. Method A and B peel strength here also shifts
rapidly over a range of 4.5 to 7.5 pli.
In a final failure mode, the strength of the adhesive bond to copper and polyimide may exceed the internal
strength of the polyimide itself,
resulting in a layer of polyimide delaminating and tearing away with the
adhesive. This failure mode is known as polyimide shattering (PS). In this case, peel strength is reported as
exceeding polyimide strength.
Further information about test procedures may be obtained from the
Institute for Interconnecting and
Packaging Electronic Circuits (IPC), 7380 N. Lincoln Ave., Lincolnwood, IL 60646.
Copper
Adhesive
Adhesive
Polyimide
Polyimide
CA CU PPS Z
CA = Cohesive Failure
CU = Failure to Copper
P = Failure to Polyimide
PS = Polyimide Shatter
Z = Zipper
Figure 3. Bond Failure Modes
The information contained in this datasheet is intended to assist you in designing with Rogers’ circuit materials. It is not intended to and
does not create any warranties, express or implied, including any warranty of merchantability or fitness for a particular purpose or that
the results shown on this datasheet will be achieved by a user for a particular purpose. The user should determine the suitability of
Rogers’ circuit materials for each application.
These commodities, technology and software are exported from the United States in accordance with the Export Administration
regulations. Diversion contrary to U.S. law prohibited.
R/flex is a licensed trademark of Rogers Corporation
Printed in U.S.A.
© 1994-2003 Rogers Corporation
0562-030-0.2SS Pub# 14-103