ASTM F1896-98

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Designation: F 1896 – 98
Test Method for
Determining the Electrical Resistivity of a Printed
Conductive Material
This standard is issued under the fixed designation F 1896; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Apparatus
1.1 This test method covers the determination of the elec- 4.1 Resistance Measuring Device, (that is, ohm meter)
trical resistivity of a conductive material as used in the equipped with test leads and probes. The device should be
manufacture of a membrane switch. capable of measuring resistances up to 100 MV with an
1.2 This test method is not suitable for measuring force accuracy of greater than 1.5 % of full scale reading. Test probes
sensitive conductive materials. should have tips that are 25 to 250 % of the width (W)ofthe
1.3 The values stated in inch-pound units are to be regarded printed conductor test pattern.
as the standard. The values given in parentheses are for 4.2 Test Surface, to be flat, smooth, unyielding and larger
information only. than switch under test.
1.4 This standard does not purport to address all of the 4.3 Thickness Measuring Device, capable of measuring to
safety concerns, if any, associated with its use. It is the the nearest 0.00005 in. (1.25 μm).
responsibility of the user of this standard to establish appro- 4.4 Dimensional Measuring Device, capable of measuring
priate safety and health practices and determine the applica- to the nearest 0.001 in. (25 μm).
bility of regulatory limitations prior to use.
5. Test Specimen
2. Terminology
5.1 A resistance test strip of printed and cured conductive
2.1 Definitions: material with a minimum length (L) to width (W) ratio of 50:1
2.1.1 membrane switch—a momentary switching device in (equal to or greater than 50 squares). A pattern of membrane
which at least one contact is on, or made of, a flexible switch circuitry is sufficient if a straight measurable strip, with
substrate. a minimum length (L) to width (W) ratio of 50:1 (equal to or
2.1.2 circuit/test pattern resistance—electrical resistance as greater than 50 squares), is available. The accuracy of the
measured between two terminations of a circuit trace. resistivity determination will be improved as the number of
2.1.3 square—A geometric unit of a printed conductive squares of the resistance test strip is increased.
circuit trace/pattern obtained by dividing the length (L)ofthe
6. Procedure
printed conductive circuit trace/pattern by its width (W).
2.1.4 resistivity—ohms per square per mil of a conductive 6.1 Pre-Test Setup:
6.1.1 Secure switch/test pattern (that is, printed and cured
material.
conductive material) on the test surface.
3. Significance and Use
6.1.2 Measure the geometry of the test pattern as follows:
3.1 Resistivity is useful to suppliers and manufacturers as 6.1.2.1 Measure the length (L) of the printed test pattern.
follows: 6.1.2.2 Measure the width (W) of the printed test pattern.
3.1.1 when designing membrane switch interface circuitry, 6.1.2.3 Divide the length (L) by the width (W) to calculate
3.1.2 when selecting the appropriate conductive material, the number of squares of the printed test pattern. Should be
3.1.3 for conductive material quality verification, and $50 squares.
3.1.4 for conductive material cure optimization and quality
NOTE 1—Measuring the length (L) and width (W) of the actual printed
control.
pattern checks the accuracy of the actual number of squares printed versus
the artwork.
1 6.2 In-Process Test:
This test method is under the jurisdiction of Committee F01 on Electronics ,
and is the direct responsibility of Subcommittee F01.18 on Membrane Switches.
Current edition approved May 10, 1998. Published September 1998.
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F1896–98
6.2.1 Us
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