1、MILITARY STANDARD . CLASSIFICATICN OF VISUAL AND MECHANICAL DEFECTS Fa EQIJIPMENT, ELECTRONIC, WIRED, AM OTHER DEVICES Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. This sttm
2、dard has been approved ky the Electronics Cod, Department of the Am, and ia nmdatorg for use by activities within the Department of the m. N other militav activities are required to employ this 8Wrd where mitable. 2. Recarmnnded corrections, additions or deletions should be addressed to Headquarters
3、, US m Electronics Material Support Agency, Fort however, defects may be grouped into other classes or into sub-classes within these classes. Other defects not classified herein of lesser import than nminorf1, having no effect upon functioning, assembly, maintenance or me (formerly classified as con
4、trol defects) pay be tolerated to the extent established by the Government, not to exceed lo$* Such defects are considered within the purview of workmnship only. When the rate of occurrence exceeds lo$, it may indicate a general degradation trend in workmanship and for control purposes such defects
5、may be classified as 1 Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4.2 Coding of Defects. The defects listed in Sectiun 5 have been given key rimuber8 to siplpllFy the prepart
6、ion sad maintenance of inspection m- Cord80 Recording the key movement of wire or solder upon pick or spadger application. U7. Rosin joint. - Presence of rosin; relative movement of wire or solder upon pick application. US. Insulation in tenninal hole. - Solder over insulation; no ap U. Minor Defect
7、. pearance of visible wire contour. lB1. Improper map. - l/4 turn or more, but less than l/2 turn; or more than 3/4 turn. lB2. Wire end - Projecting more than 1/16 inch from surface. Note: When wire end8 project to the axtent that a possible short circuit could occur, the defect Shall be evaluated i
8、n accordance with Tspe 6. 2 P Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-#IZrSTD-252B(EL) 19 Januarg 1970 5.2 SouERING DEFECTS PECULIAR TO PRINTED KIRII?G ASEiEbw 5.2.1 Class
9、ifying Defects for Solder Connections in Printed Wiring Boards . A deteminaticm of whether more than one defect will be applied to a single connection in a grinted wiring board #ill depend upon the soldering process used in fabriation and appllcstion of components to a printed niring bard. When the
10、process used applies 8older to both eides of the board during one operation, missing or poor solder on either or both sides can om be ChS8ified a8 one defect, When the process used requires two separate 8ppl.i- cations of solder (one on each side of the board), missing or poor solder on both sides o
11、f the board wUI. be classified as defects. U. Major Defects UlO, Any printed wiring solder joint that is not a cqlete con- centric void-free fillet of sQlder wetting both the flange of the part (eye- let terminal post, etc.) or the component lead and the terminal area. Ull. Clearance - Any buildup o
12、f solder or protruding of leads greatel than 3/32 inch above the control laminate on the side opposite the component. 1A12, Charred Area - Any charred area between laminates. M3. Lead Terminations - Leads through termination holes not with- in specified dimensional tolerances. 5.3 TYPE - SOLDERLESS
13、CONNECTCPiS 2A. Va3or Defects U?, Incorrect terminal size for a given wire gauge. 2A8. Cracked metal part, affecting use. 2B Minor Defect 2B3. Be-insulation broken, but no potential short circuit hasard. 2B6. Improper crimp (evidenced by round shape of basic wire edge) . 3 * Copyright Communications
14、 - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-252B MI m 77777LL 0077553 I m 2B6. Cracked metal part, not affecting use. 5.4 TPPE 3 - CABLING AND WIRING S, Major Defects 3AL Broken or nicked str
15、ands - More than 20% of wire, except: a. In less than 7 strand wire, 1 broken or nicked strand. b, In 7.atrand wire, 2 broken or nicked strands. 1 33. for example, a poly- styene lead dressed against a power tube. Copyright Communications - Electronics Command Provided by IHS under license with CRAI
16、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-252B MI M 9799711 0077554 3 m I u* Halor Defects: See Table I. me four subdivisions respectively refer, for example, to one fastener missing where one wad intended, one fastener missing where two were intended
17、, one fastener missing where three or mre were intended, and two fasteners missing where three or more were intended. Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I MIL-STD-252
18、B MI m 7799733 0077555 5 m i 5 - FCfBIQ? 03JECTS Ma30r Defects L l m meUc foreign object, not finaly attached, uhich could circuit, an electrical contact failure, or mechanical failure. i Two or metallic foreign objects. non-metalllc foreign object, auch as insubtion, dirt phenoc chips, or cede cps,
19、 that could cause jnnan.t.ng of a mechanism, Wge to gear teeth or driving mechanism, or prevent electrical contact. 1 I 4 s. Minor Defects: 5Bl. Foreign objects that cannot be dislodged the application of i P roaml+b with a pick or spudger 8hall be considered to be firmly attached. Such objects, if
20、becaming loosened due to environmental conditions in service, would not likely cause failures such as cited in 5A3). (Small size objects) /1 Pwsence of any foreign objects either firmly or not firmly attached is very undesireable and is considered poor worhanshp. Under environmental conditions, (sho
21、ck, vibration, temperature) . Firmly attached objects at factory inspection may become loosened and became dislodged in 8ervice, due to change in the adhesive, properties of the substance holding the foreign object . (Substances such as rosin flux, varnish, paint, etc. are in this category). Foreign
22、 objects such as screws, washers, chips of naterial, etc, which are inadvertently clantped between wires, camponents or component and chassis or other elements may become loosened or dislodged due to vibration during field use, which my cause failures such as cited in W, 92 and 5A3. 5.7 TIE 6 - POTE
23、NTIAL SHORT CIRCUIT 5.7.1 Amlicablity: The potential short classification covers instances there there are bare conducting members inadequately separated due to irregularities of worlananship during the manufacturing process, e.g., missing, frayed, or damged insulation, excess solder, projecting wir
24、e ends, improper assembly, improper placement of uninsulated conductors, etc. Com- ponent leads and other conductors which are uninsulated and wbich are adja- cent to each other must be separated sufficiently to prevent short circuits resulting from flsshover or from low resistance leakage paths due
25、 to inade- pate creepage distance. This precaution is especially important in equip- ment which will be subject to vibration and shock, or subjected to adverse environmental cmditions. The potential short classification does not apply to spacing which is inherent in the-design of the equipment e,g.,
26、 nomal space between variable capacitor plates, between aocket terminals, submini- ahwe and printed wiring circuit design, etc. The distance between the bare . 6 Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitte
27、d without license from IHS-,-,-MIL-STD-252B MI m 79777LL 0079556 7 m d tmnducting surfaces creepage distance is the leakage path for a poten- tial short circuit between any two conductors (insulating material - surface path). (See Figure 1) . / A- ELECTRICAL CLEARANCE B- CREEPAGE DISTANCE FIGURE E 8
28、 Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-252B MI m 7777711 0077558 O m Table II - Electria Clearance and Creepage Distance Voltage Peak AC or DC 301-600 601-1000 A
29、 B c A B C A B C A B C J- - 1/16 l/s v4 1/16 % Creepage Distance in Inches fisss than Enclosure I Enclosure II v2 1 2 Condition A- For use where the effect of a short circuit is limited ta the Mit, and where noml operating power does not exceed 50 watts. Condition B - For use where short circuit pro
30、tection in the form of fuses, circuit breakers, etc, is provided, and uhem nod operating pomr does not exceed 2000 watts. Condition C - For use where short circuit protection in the -form of ftmes, circuit breakers, etc, i8 provided, and where noFmal operating power exceeds 2000 watts. Enclosure I -
31、 Enclosure I is an esuipmrent enclosure which has no openings, .or in which the openings are so constructed that drops of li or contact pressure less than required by applicable speci- fication. . ,-g-, Contacts may appear to be, but are not touching. (A paper sheet Figure 2 passes through) 1OA2, Cl
32、osed contacts - Contacts do not open upon release action of device to provide proper clearance, (me m 6, J Table II, Min. Clearances). 10A3, Improper Knifing - No contact, or no pressure dsts between knife blade and mating contacts (see Figure 3). Figure 3 12 Copyright Communications - Electronics C
33、ommand Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-252B MI m 9777733 0079562 2 MIL-STD-Z52B(EL) 19 J- J970 - 1OB. mor Defects 10B3. Round flat COntaCts (mismatching) , Relative displacement of centers greater than
34、D/4, but actual contact S%= sPd8t8. (Sm Fim 4) 10%. Spherical contacts (mismatching), Relative displacement of centers greater than D/4, but actual contact still. exists. (See Figrue 5) 10B5, Spherical arid flat contacts (mismatching), Center of spherical contact is off edge of flat contact, but act
35、ual contact still dsts. (See Figure 6) Center off dge Figure -5 Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CF PART or aterial. U. Improper adjustment rmsafo in service. -3. D
36、efonned or damaged h service, U. Levers, toggles and do not functicm peoperly P or use i or assembly causing parts. to be inoperative or ! parts, inoperative or do not function properly I 1 other such mechanisms that are inoperative or intended and could cause failure in use . 1185. Improper machini
37、ng resultant in sharp burrs or imperfections which would cause parts to be dangerous to handle or cause major difficulty in assembly or repair operations. UA7. Holes or holes missing, improperly aligned, or unuseable because llA8. Insulators or insulation missing or damaged so as to affect intended
38、I OP size or fill. mechanical or electrical use. llA9. Color coding wrong, missing, or illegible. llAJ.0. Staking or riveting missing or defective so as to cause probable mechanical or electrical failure. UAll. External or internal threads missing, wrong size, or so damaged as to prevent proper use.
39、 llA3.2. Weight not within specified limits (when applicable). W. Seal missing or defective. lIAl.4. hbrication missing (dry reservoir) or incorrect type (too heavy for principal mechanism to function properly). llAl5. Ceramic, glass, porcelain, or plastic parts cracked, chipped, or brolcsrr, which
40、could cause part to be unuseable or unsafe, or could cause mohanical or electrical failure in service. llAl6. Dimensions out of tolerance which will affect interchangeability, asssmblg, or operation, 4-4 Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for Re
41、saleNo reproduction or networking permitted without license from IHS-,-,-MILSTD-252B(EL) 19 January 1970 llAl7. Missing, broken or incaplete welds (resultant in structural weak- ness). llAl8. Welds having evldence of poor penetration or poor fusion. ll4l9. Velds containing blow holes, cracks or slag
42、 inclusion. Wl. Corrosion - corrosion which could cause mechanical, operational or electrical failure. UB. Minor Defects llB2. Improper adjustment or.assembly which could reduce efficiency of operation or use but not inoperative or unsafe in service. m3 Deformed or damaged parts *ch do not affect op
43、eration or use in service. W. Levers, toggles and.other such mechanism which function improperly reducing efficiency of operation but would probably not cause failure in use. UB5. Burrs or imperfections on pa excessive (cauae possible malfunction). UB16. Dimensions out of tolerance which would not a
44、ffect interchange- ability assembly, or operation. llB20. Incomplete removal of welding flux residue which may subsequently affect the application of a finish. llB2L Corrosion - Corrosion on parts . does not interfere with 5nbnded function or u88 in semrlce. 16B8. Fastening Device - warped, bUstered
45、, soiled, scratched, or burned. 16W. 1/32 inch. Gaskets - Gaskets torn, twisted, rroiled, or extruding more than 17A. kAor Defects 17Al. Missing, or wrong parts. 174. Required marldngs incorrect, missing, or illegible. 17A5. Finish incorrecO or missing. 17A6. Burrs, splinters, sharp edges, likely to
46、 cause parsalal injury. 17A7. Outline dimensions exceeded. 17A8. Deformed or damaged parts which will affect operation or use in service . 17A9. Marking method not as specified (method of application). lm, rSTD-=252B(EL) 19 Jarnrary W70 10.0 References APPEXDIX I 10.1 The folJ.owing documents have b
47、een used in the technical develop- mont of this standard; however, they are not specifically referenced and do not form a part of this document. 10.2. l4ilital.g KLP-55llO printed Circuit Boards 10.3. Standards “D-454 Staxxard General Requirements for Electronic -pent 10.4. Ab612054 Department of Co
48、mmerce Standards of Worlollanship for Wired Equipment (Quality Assurance Pamphlet) 24 Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-WS. GOVERNMENT PRINTING OFFICE:1972-714-907/150 Copyright Communications - Electronics Command Provided by IHS under license with CRAINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
