ASTM F2749-09

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Designation: F2749 − 09
StandardTest Method for
Determining the Effects of Creasing a Membrane Switch or
1
Assembly
This standard is issued under the fixed designation F2749; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.3 Specific areas of testing include, but are not limited to:
3.3.1 Membrane switch flex tails, and
1.1 Thistestmethodestablishesamethodforthecreasingof
3.3.2 Any component of a membrane switch that may be
any part of a membrane switch with conductive circuits.
subjected to creasing.
1.1.1 The values given in SI units are to be regarded as the
standard. The values given in parentheses are for information
4. Interferences
only.
1.2 This standard does not purport to address all of the 4.1 The following parameters may affect the results of this
safety concerns, if any, associated with its use. It is the test:
responsibility of the user of this standard to establish appro-
4.1.1 temperature,
priate safety and health practices and determine the applica-
4.1.2 humidity, and
bility of regulatory limitations prior to use.
4.1.3 orientation of the conductor (either extension or com-
pression) could have significant impact on the results.
2. Terminology
4.1.4 Inelasticity and parallelism of roller and test bed will
2.1 Definitions:
affect the displacement of the force across the sample. In other
2.1.1 crease—a ridge or groove made by folding and press-
words, the roller and test bed must not be compressible or
ing.
subject to warping or distortion during the test cycle.
2.1.1.1 Discussion—The fold mark in the substrate will be
Furthermore, the roller must remain parallel to the test bed
caused by a roller rolled over a fold that will likely remain in
through the entire test cycle.
the substrate after testing.
NOTE 1—Experience has shown that some conductors recover their
2.1.2 crease cycle—a 180 degree crease followed by a
conductive properties if allowed to stabilize after the dynamic portion of
straightening of the crease (see Fig. 1). the test. Therefore, continuous monitoring is necessary.
2.1.3 membrane switch—a momentary switching device in
5. Apparatus
which at least one contact is on, or made of, a flexible
substrate.
5.1 Roller, allowed to rotate smoothly around its longitudi-
nal axis, rigid, low friction smooth surface.
2.1.4 membrane switch tail—a flexible portion of a mem-
brane switch used for input/output connection. 5.1.1 Roller, measuring 50.8 mm (2 in.) in diameter, toler-
ance 65%.
3. Significance and Use
5.2 Fixture to hold test sample securely in place in a
3.1 Creasingofmembraneswitchesortheircomponentscan
horizontal manner (refer to Fig. 1).
affecttheirvisualappearance,mechanicalintegrityorelectrical
5.3 Mechanisms capable of providing a constant force and
functionality. This practice simulates conditions that may be
rate of travel to roller.
seen during manufacture, installation or use.
5.4 Equipment for the continuous monitoring and recording
3.2 Crease testing may be destructive, therefore any
of resistance.
samples tested should be considered unfit for future use.
NOTE 2—Experience has shown that some conductors recover their
conductive properties if allowed to stabilize after the dynamic portion of
the test. Therefore, continuous monitoring is necessary.
1
This test method is under the jurisdiction of ASTM Committee F01 on
Electronics and is the direct responsibility of Subcommittee F01.18 on Membrane
6. Test Samples
Switches.
Current edition approved June 15, 2009. Published November 2009. Originally
6.1 The test samples may be components, tail assembles or
approved in 2008. Last previous edition approved in 2008 as F 2749-08. DOI:
10.1520/F2749-09. finished switches. If the sample length is too short for the test
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F2749 − 09
FIG. 1 Test Fixture Setup
fixture, a sample coupon of the same construction (layer to 7.1.2 Loop the unsecured end (dynamic end) of the test
layer) must be provided (minimum; 250 mm length by 25 mm
sample underneath the static portion.
width).
7.1.3 Clamp the dynamic end of the test sample to the
6.2 The width of the test sample must not exceed the length dynamic position of the test fixture.
of the roller.
7.1.3.1 Ensure that the both ends of the test sample remain
aligned (one on top of another) during motion of test.
7. Procedure
7.1.4 Connect to the test sample so that circuit resistance
7.1 Refer to Fig. 1 – drawing of mechanical hook up.
can be monitored continuo
...