ASTM B885-97

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: B 885 – 97
Standard Test Method for
Presence of Foreign Matter on Printed Wiring Board
Contacts
This standard is issued under the fixed designation B 885; 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 3.2.2 printed wiring board (PWB) contacts, PWB fingers,
n—areas near the edge of a printed wiring board coated with
1.1 This test method defines a resistance probing test for
gold and designed to function as electrical contacts when the
detecting the presence of foreign matter on Printed Wiring
board is plugged into a compatible edgecard connector.
Board (PWB) contacts or fingers that adversely affects electri-
cal performance. This test method is defined specifically for
4. Summary of Test Method
such fingers coated with gold. Application of this test method
4.1 Two closely spaced electrodes are brought into contact
to other types of electrical contacts or to fingers coated with
with a single PWB finger in such a manner that they contact the
other materials may be possible and desirable but may require
surface with a minimum of wipe. A fixture loads each electrode
some changes in fixturing, procedures, or failure criteria.
to apply a force in the range of 0.5 to 0.7 N to the surface of
1.2 Practice B 667 describes another contact resistance
the finger. Two electrical leads attached to each electrode are
probe method that has more general application to electrical
used to make a four–wire resistance measurement to detect
contacts of various materials and shapes. Practice B 667 should
elevated resistance indicative of the presence of a film or other
be used for more fundamental studies. This test method
contaminant on the finger.
provides a fast inspection method for printed wiring board
fingers.
5. Significance and Use
1.3 This standard does not purport to address all of the
5.1 This test method provides a way to detect contamination
safety concerns, if any, associated with its use. It is the
on printed wiring board fingers that affects the electrical
responsibility of the user of this standard to establish appro-
performance of such fingers. Such contamination may arise
priate safety and health practices and determine the applica-
during PWB manufacture, circuit assembly, or service life and
bility of regulatory limitations prior to use.
may include solder mask, solder flux, hardened lubricants,
2. Referenced Documents dust, or other materials. This test method provides a nonde-
structive method of inspecting such fingers at any point in the
2.1 ASTM Standards:
life of the product including after original manufacture, after
B 539 Test Methods for Measuring Contact Resistance of
2 assembly of circuit components to the PWB, and after time in
Electrical Connections (Static Contacts)
service such as when returned for repair. Because this test
B 542 Terminology Relating to Electrical Contacts and
2 method uses two probes to finger contacts in series, it provides
Their Use
a sensitive test for contaminants that may increase electrical
B 667 Practice for Construction and Use of a Probe for
2 resistance when the fingers are plugged into an edgecard
Measuring Electrical Contact Resistance
connector that typically makes contact to the finger through
3. Terminology only one contact to finger interface.
5.2 Practice B 667 describes a more general procedure for
3.1 Definitions—Terms used in this test method related to
measuring contact resistance of any solid material in practi-
electrical contacts are defined in accordance with Terminology
cally any geometrical form. The method in Practice B 667
B 542.
should be used for general studies and fundamental studies of
3.2 Definitions of Terms Specific to This Standard:
electrical contact materials.
3.2.1 edgecard connector, n—an electrical connector de-
signed to connect physically and electrically with a compatible
6. Apparatus
PWB equipped with gold fingers.
6.1 Four-Wire mV Meter, with a resolution of 0.0001 V or
better, capable of performing dry circuit resistance measure-
This test method is under the jurisdiction of ASTM Committee B-02 on
ments in accordance with Test Method B 539.
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
6.2 Two Gold-Tipped Electrodes (Probes), with a radius not
B02.11 on Electrical Contact Test Methods.
Current edition approved Dec. 10, 1997. Published November 1998. less than 3.0 mm at the tips. Each electrode shall have two
Annual Book of ASTM Standards, Vol 02.04.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
B 885
wires attached. One wire, the voltage lead, shall be attached 6.10 Compressed Air, at 100 to 200 kPa above atmospheric
within 2 mm of the tip end. The other wire, the current lead, pressure (15 to 25 psig) or a handheld can of compressed gas
shall be attached at any convenient location that is at least 0.5 with nozzle designed for use as a dust removal tool, commonly
mm farther away from the tip than the attachment point of the referred to as a “duster.”
voltage lead.
7. Reagents and Materials
6.3 Fixture, to hold the PWB securely while it is being
probed and a fixture to hold the two electrodes, such that the 7.1 Isopropyl Alcohol (IPA), P
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