ASTM B885-1997(2003) Standard Test Method for Presence of Foreign Matter on Printed Wiring Board Contacts《印刷线路板触点上存在杂质的标准试验方法》.pdf

1、Designation: B 885 97 (Reapproved 2003)Standard Test Method forPresence of Foreign Matter on Printed Wiring BoardContacts1This standard is issued under the fixed designation B 885; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th

2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method defines a resistance probing test fordetecting the presence of foreign matter on Printed W

3、iringBoard (PWB) contacts or fingers that adversely affects electri-cal performance. This test method is defined specifically forsuch fingers coated with gold. Application of this test methodto other types of electrical contacts or to fingers coated withother materials may be possible and desirable

4、but may requiresome changes in fixturing, procedures, or failure criteria.1.2 Practice B 667 describes another contact resistanceprobe method that has more general application to electricalcontacts of various materials and shapes. Practice B 667 shouldbe used for more fundamental studies. This test

5、methodprovides a fast inspection method for printed wiring boardfingers.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to become familiarwill all hazards including those identified in the

6、appropriateMaterial Safety Data Sheet for this product/material as pro-vided by the manufacturer, to establish appropriate safety andhealth practices, and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:B 539 Test Methods for Measuring Cont

7、act Resistance ofElectrical Connections (Static Contacts)2B 542 Terminology Relating to Electrical Contacts andTheir Use2B 667 Practice for Construction and Use of a Probe forMeasuring Electrical Contact Resistance23. Terminology3.1 DefinitionsTerms used in this test method related toelectrical cont

8、acts are defined in accordance with TerminologyB 542.3.2 Definitions of Terms Specific to This Standard:3.2.1 edgecard connector, nan electrical connector de-signed to connect physically and electrically with a compatiblePWB equipped with gold fingers.3.2.2 printed wiring board (PWB) contacts, PWB f

9、ingers,nareas near the edge of a printed wiring board coated withgold and designed to function as electrical contacts when theboard is plugged into a compatible edgecard connector.4. Summary of Test Method4.1 Two closely spaced electrodes are brought into contactwith a single PWB finger in such a ma

10、nner that they contact thesurface with a minimum of wipe. A fixture loads each electrodeto apply a force in the range of 0.5 to 0.7 N to the surface ofthe finger. Two electrical leads attached to each electrode areused to make a fourwire resistance measurement to detectelevated resistance indicative

11、 of the presence of a film or othercontaminant on the finger.5. Significance and Use5.1 This test method provides a way to detect contaminationon printed wiring board fingers that affects the electricalperformance of such fingers. Such contamination may ariseduring PWB manufacture, circuit assembly,

12、 or service life andmay include solder mask, solder flux, hardened lubricants,dust, or other materials. This test method provides a nonde-structive method of inspecting such fingers at any point in thelife of the product including after original manufacture, afterassembly of circuit components to th

13、e PWB, and after time inservice such as when returned for repair. Because this testmethod uses two probes to finger contacts in series, it providesa sensitive test for contaminants that may increase electricalresistance when the fingers are plugged into an edgecardconnector that typically makes cont

14、act to the finger throughonly one contact to finger interface.1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.11 on Electrical Contact Test Methods.Current edition approved June 10, 2003. Published J

15、uly 2003. Originallyapproved in 1997. Last previous edition approved in 1997 as B 885 - 97.2Annual Book of ASTM Standards, Vol 02.04.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 Practice B 667 describes a more general procedur

16、e formeasuring contact resistance of any solid material in practi-cally any geometrical form. The method in Practice B 667should be used for general studies and fundamental studies ofelectrical contact materials.6. Apparatus6.1 Four-Wire mV Meter, with a resolution of 0.0001 V orbetter, capable of p

17、erforming dry circuit resistance measure-ments in accordance with Test Methods B 539.6.2 Two Gold-Tipped Electrodes (Probes), with a radius notless than 3.0 mm at the tips. Each electrode shall have twowires attached. One wire, the voltage lead, shall be attachedwithin 2 mm of the tip end. The other

18、 wire, the current lead,shall be attached at any convenient location that is at least 0.5mm farther away from the tip than the attachment point of thevoltage lead.6.3 Fixture, to hold the PWB securely while it is beingprobed and a fixture to hold the two electrodes, such that thedistance between the

19、 centers of the electrodes is 2.0 to 2.5 mmand both electrodes will be centered roughly on a single PWBfinger. Fig. 1 shows an example of a suitable fixture. Otherfixtures that provide the same capability may be used. Locatethis fixture to minimize shock and vibration reaching theprobes. Placement o

20、n a foam pad on a bench top has beenfound suitable.6.4 Two Springs, one for each electrode, having a springconstant and a pretension that will apply a load in the range of0.5 to 0.7 N when the electrode is brought to rest on the fingerbeing tested. Other mechanisms that achieve the same resultare ac

21、ceptable.6.5 Mechanism, that will move the electrode fixture from anopen position to the closed position on the finger in such amanner that the electrodes meet the surface of the contact witha minimum of wipe.6.6 Lens Tissue, for cleaning the electrodes.6.7 Beakers, 100-mL size, two required.6.8 Hot

22、 Plate, suitable for warming two breakers.6.9 Thermometer, calibrated in C over the range of 0 to 100C.6.10 Compressed Air, at 100 to 200 kPa above atmosphericpressure (15 to 25 psig) or a handheld can of compressed gaswith nozzle designed for use as a dust removal tool, commonlyreferred to as a “du

23、ster.”7. Reagents and Materials7.1 Isopropyl Alcohol (IPA), Pure Chemical Grade7.2 A goldcoated calibration coupon covered with a mini-mum of 2.0 m of gold electrodeposit on the surface to be usedin testing and verifying the cleanliness of the probes. Specialcare should be taken with the coupon to e

24、nsure and preserveFIG. 1 Resistance ProbeB 885 97 (2003)2the cleanliness of the gold surface, including avoiding touchingthe gold surface with anything other than the test probes.8. Test Procedure8.1 Clean the goldplated calibration coupon within 8 hprior to performing measurements, by dipping it in

25、to a beakerof isopropyl alcohol at 50C for 1 min. and then into a secondbeaker with isopropyl alcohol at 50C for 1 min.8.2 Connect probe connections to the milliohmeter usingfour-wire connections and set the milliohmeter for dry circuitconditions.8.3 Both before and after each PWB is probed, probe t

26、hegoldplated calibration coupon once. If this reading is greaterthan 4 mV, clean the electrodes by wiping with clean lenstissue and measure resistance again, repeating the process untilthe reading is 4 mV or below.8.4 Blow dust and particles off of the fingers using cleancompressed air or handheld c

27、ompressed gas duster.8.5 Probe each finger on the PWB on the board onceaccording to the following steps and record the resistance valuefor each finger. Repeat 8.6-8.9 for each finger.8.6 Align the finger that is to be probed under the electrodesand clamp down.8.7 Bring the probe down onto the finger

28、 such that theelectrodes contact the surface of the finger with a minimum ofwipe. As discussed in Section 6, the load on each electrodeshall be in the range of 0.5 to 0.7 N.8.8 Record the initial reading, taken within2softheelectrodes contacting the finger. The electrodes gradually maypenetrate film

29、s or other contamination on the surface, and asthey do, the measured resistance will decrease. It is important,therefore, to obtain and record the initial reading.8.9 If the reading exceeds 10 mV, wipe the probe tips withclean lens tissue.9. Interpretation of Results9.1 The fingers on the PWB are fr

30、ee of significant contami-nation if the results satisfy both of the following conditions:9.1.1 No finger has resistance greater than 50 mV, and9.1.2 Not more than one finger has a resistance greater than10 mV.10. Report10.1 Report the following information:10.1.1 Test laboratory identification.10.1.

31、2 Test operator.10.1.3 Date of test.10.1.4 Identification of apparatus used.10.1.5 Identification of parts tested.10.1.6 Test results, including number of fingers probed,number exceeding predetermined resistance levels, and pass orfail conclusions as appropriate.10.1.7 Deviations, if any, from docum

32、ented test method.10.1.8 Any observations that the test operator feels arerelevant.10.1.9 Any failure analysis performed on boards tested.11. Precision and Bias11.1 No statement is made about either the precision or biasof this test method for measuring presence of foreign matter onprinted wiring bo

33、ard contacts since the result merely stateswhether there is conformance to the criteria for successspecified in the procedure.12. Keywords12.1 contact resistance; contamination; edgecard connector;printed wiring board fingersASTM International takes no position respecting the validity of any patent

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35、any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments

36、 will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by

37、 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).B 885 97 (2003)3