1、Designation: B 579 73 (Reapproved 2004)Standard Specification forElectrodeposited Coatings of Tin-Lead Alloy (Solder Plate)1This standard is issued under the fixed designation B 579; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This specification cover
3、s the requirements for electrode-posited tin-lead coatings on fabricated articles of iron, steel,copper, and copper alloys, to protect them against corrosion(Note 1), to improve and preserve solderability over longperiods of storage, and to improve anti-galling characteristics.NOTE 1Some corrosion o
4、f tin-lead coatings may be expected inoutdoor exposure. In normal indoor exposure, tin-lead is protective oniron, copper, and copper alloys. Corrosion may be expected at disconti-nuities (pits or pores) in the coating. Porosity decreases as the thickness isincreased. A primary use of the tin-lead co
5、ating (solder) is with the printedcircuit industry as a solderable coating and as an etch mask material.1.2 This specification applies to electrodeposited coatingscontaining a minimum of 50 % and a maximum of 70 % tin.The specification applies to mat, bright, and flow-brightenedtin-lead coatings.NOT
6、E 2Tin-lead plating baths are composed of tin and lead fluobo-rates and of addition agents to promote stability. The final appearance maybe influenced by the addition of proprietary brighteners. Without bright-eners, the coatings are mat; with brighteners, they are semibright or bright.Flow-brighten
7、ed coatings are obtained by heating mat coatings to abovethe melting point of tin-lead for a few seconds and then quenching; palmoil, hydrogenated oils, or fats are used as a heat-transfer medium at atemperature of 260 6 10C (500 6 20F), but other methods of heatingare also in use. The maximum thick
8、ness for flow-brightening is about 7.5m (0.3 mil); thicker coatings tend to reflow unevenly. The shape of thepart is also a factor; flat surfaces tend to reflow more unevenly than wiresor rounded shapes (Note 3).NOTE 3Volatile impurities in tin-lead coatings will cause bubblingand foaming during flo
9、w-brightening resulting in voids and roughness.The impurities can arise from plating solution addition agents and fromimproper rinsing and processing.1.3 This specification does not apply to sheet, strip, or wirein the unfabricated form or to threaded articles having basicmajor diameters up to and i
10、ncluding 19 mm (0.75 in.).2. Referenced Documents2.1 ASTM Standards:2B 183 Practice for Preparation of Low-Carbon Steel forElectroplatingB 242 Guide for Preparation of High-Carbon Steel forElectroplatingB 281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Conversion
11、CoatingsB 322 Practice for Cleaning Metals Prior to ElectroplatingB 487 Test Method for Measurement of Metal and OxideCoating Thicknesses by Microscopical Examination of aCross SectionB 499 Test Method for Measurement of Coating Thicknessby the Magnetic Method: Nonmagnetic Coatings on Mag-netic Basi
12、s MetalsB 504 Test Method for Measurement of Thickness of MetalCoatings by the Coulometric MethodB 567 Test Method for Measurement of Coating Thicknessby the Beta Backscatter MethodB 568 Test Method for Measurement of Coating Thicknessby X-Ray SpectrometryE 105 Practice for Probability Sampling of M
13、aterialsE 122 Practice for Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for Charac-teristic of a Lot or Process2.2 Other Standards:MIL-STD-105 Sampling Procedures and Tables for Inspec-tion by Attributes3MIL-STD-414 Sampling Procedures and Tables for Inspec-tion
14、by Variables for Percent Defective33. Classification and Service Condition3.1 Orders for articles to be plated in accordance with thisspecification shall specify, in addition to the ASTM designation1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings
15、and is the direct responsibility of SubcommitteeB08.08.04 on Soft Metals.Current edition approved April 1, 2004. Published April 2004. Originallyapproved in 1973. Last previous edition approved in 1999 as B 57973 (1999).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact
16、ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.1Copyright
17、 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.number and year of issue, the classification notation indicatingthe basis metal and thickness of tin-lead coating required, orthe service condition number indicating the severity of servicerequir
18、ed for the coating. In addition, when specifying a tin-leadcoating composition, the first number shall refer to the tincontent in percent.3.1.1 Classification Notation:Symbol ClassificationFe/ Iron or steel basis metalsCu/ Copper or copper alloy basis metals/Sn-Pb Tin-lead coating and its compositio
19、n number, when re-quired; for example, Sn60-Pb40Number Minimum coating thickness in micrometres(5 to 50)Suffix Letterf flow-brightenedb brightm matAn example of complete classification notation is as follows: Cu/Sn60-Pb40/5F3.1.2 Service Condition Number:No. Service Condition4 very severe exposure3
20、severe exposure2 moderate exposure1 mild exposureNOTE 4See Appendix X1 for additional description of exposureconditions and examples of typical end uses. The coating thicknessesgiven for each service condition are guidelines and are not intended to beabsolute values.4. Significant Surfaces4.1 Signif
21、icant surfaces are defined as those surfaces nor-mally visible (directly or by reflection) that are essential to theappearance or serviceability of the article when assembled innormal position; or those surfaces that can be the source ofcorrosion products that will deface visible surfaces on theasse
22、mbled article. When necessary, the significant surfacesshall be indicated on the drawing of the part, or by theprovision of suitably marked samples.NOTE 5When significant surfaces include areas on which the speci-fied thickness of deposit cannot readily be controlled, such as threads,holes, deep rec
23、esses, bases of angles, and similar areas, the purchaser andthe manufacturer should recognize the necessity for either thicker depositson the more accessible surfaces or for special racking. Special racks mayinvolve the use of conforming, auxiliary bipolar electrodes, or noncon-ducting shields.5. Ma
24、terials and Manufacture5.1 Defects in the surface of the basis metal, such asscratches, porosity, nonconducting inclusions, roll and diemarks, cold shuts, and cracks, may adversely affect theappearance and the performance of coatings applied theretodespite the observance of the best plating practice
25、s. Accord-ingly, the platers responsibility for defects in the coatingresulting from such conditions shall be waived, except when heis also in the position of prime contractor supplying platedparts.NOTE 6In order to minimize problems of this sort, the specificationscovering the basis material or the
26、 item to be plated should containappropriate limitations on such basis metal conditions.5.2 When required the basis metal shall be subjected to suchpolishing or buffing operations as are necessary to yielddeposits with the desired final appearance (Section 6).5.3 Proper preparatory procedures and th
27、orough cleaning ofthe basis metal surface are essential in order to assure satis-factory adhesion and corrosion performance of the coating.Accordingly, it is suggested that the following Practices for thepreparation of various basis metals for electroplating befollowed when appropriate: B 183, B 281
28、, and B 322 andGuide B 242.5.4 When necessary, preliminary samples showing the finishshall be supplied to and approved by the purchaser. Where rackmarks are inevitable, their location shall be the subject ofagreement between supplier and purchaser.6. Physical Composition6.1 CompositionThe tin-lead c
29、oating composition shallbe as follows (Note 7):Element Weight, %Tin (Sn) 50 to 70Lead (Pb) remainder6.1.1 The tin percentage is calculated as follows:Tin, % 5 134.1 3 L/A 2 1! (1)where:L = weight of lead coating, g, andA = weight of alloy coating, g.NOTE 7Only the tin content need be determined. Lea
30、d is usuallydetermined by difference. A sample of the deposit can be obtained byplating on a stainless steel panel from which the coating can be peeled orby employing any recognized stripping method. The alloy composition ofthe deposit can be determined by methods such as gravimetric orvolumetric an
31、alysis, density measurements, atomic absorption spectropho-tometry, X-ray fluorescence, and beta backscatter.In addition, the alloy composition produced by a plating solution maybe obtained by comparing the weight of a tin-lead coating deposited by agiven number of ampere-hours to the weight of lead
32、 coating produced ina lead fluoborate coulometer in series with the plating bath.6.2 AppearanceThe tin-lead coating shall be smooth, finegrained, continuous, adherent, and shall be free of visibleblisters, pits, nodules, indications of burning, excessive build-up, staining, and other defects. Flow-b
33、rightened coatings shallnot have dewetted areas or beads, and shall be free of the oilused in the fusion process.6.3 ThicknessThe thickness of the coating on significantsurfaces shall conform to the requirements in Table 1 and TableTABLE 1 Tin-Lead Alloy Coatings on SteelServiceConditionClassificati
34、onNumberMinimumThicknessm milSC4AFe/SnPb 30 30 1.2SC3AFe/SnPb 20 20 0.8SC2 Fe/SnPb 10 10 0.4SC1 Fe/SnPb 5 5 0.2SC1 Fe/SnPb 5fB5 0.2AAn undercoat of 2.5 m (0.1 mil) copper is recommended for SC3 and SC4.Bf = flow brightened orm = mat orb = brightB 579 73 (2004)22.6.3.1 Thickness MeasurementsTin-lead
35、alloy thicknessmeasurements shall be made on those areas of the significantsurfaces where the coating would be expected to be thinnest.The method of determining the thickness shall be agreed uponby the manufacturer and purchaser. Several methods areavailable depending upon the thickness of coating,
36、the shape ofthe article, and the basis metal. They include beta backscatter,coulometric, magnetic, microscopical, and X-ray fluorescencetest methods. The methods are outlined in 9.1.NOTE 8Thicknesses determined by beta backscatter, coulometry, andX-ray fluorescence are a function of the composition
37、as well as thethickness of the coating.6.4 AdhesionThe adhesion of the coating shall be ad-equate to pass the tests described in 9.2.6.5 Solderability:6.5.1 When specified by the purchaser, the coating shall betested by one of the methods described in 9.2. The results shallbe evaluated in accordance
38、 with each procedure described inthat section.6.5.2 When specified by the purchaser, the coating oncopper and copper alloys shall, before solderability testing, besubjected to the preliminary artificial aging treatment describedin 9.3.6 to determine if they may be expected to retain theirsolderabili
39、ty during periods of storage.NOTE 9See Appendix X2 for design considerations that have an effecton the selection of thickness of the coating and, ultimately, on thesolderability of the electrodeposits.7. Hydrogen Embrittlement7.1 High-tensile strength steels, and severely cold-workedsteels, are susc
40、eptible to embrittlement by hydrogen in bothcleaning and plating operations. The embrittling hydrogenshall be removed by heat treatment. Procedures for baking tominimize embrittlement before and after plating are covered inSections 2 and 7 of Guide B 242.8. Sampling8.1 Test methods are time consumin
41、g and often destructive;therefore 100 % inspection is usually impractical. The pur-chaser should select a suitable sampling plan for the acceptancetesting of lots of coated items. In order that the manufacturer(plater) may know the quality standard he is expected to meet,the plan selected should be
42、made part of the purchase contract.8.2 General information on sampling procedures is given inRecommended Practices E 105 and E 122. Standard samplingplans are suggested in Military Standards MIL-STD-105 andMIL-STD-414.9. Test Methods9.1 Thickness:9.1.1 To meet the thickness specifications of the coa
43、tings,the plater is advised to:9.1.1.1 Maintain regular control of all solutions,9.1.1.2 Inspect the equipment at regular intervals, and9.1.1.3 Check thickness at periodic intervals.9.1.2 The following ASTM methods are acceptable formeasuring local thickness of the coating: B 487, B 499, B 504,B 567
44、, and B 568.9.2 Adhesion:9.2.1 Burnishing TestRub an area of not more than 630mm2(1 in.2) of the coated surface, selected at the discretion ofthe inspector, rapidly and firmly for 15 s with a smooth metalimplement. A suitable burnishing implement is a copper orsteel disk used edgewise and broadside.
45、 Maintain a pressuresufficient to burnish the coating at every stroke, but not so greatas to cut it. Poor adhesion will be shown by the appearance ofa loose blister which grows as burnishing is continued. If thequality of the coating is poor also, the blister may crack and thecoating peel away from
46、the basis metal.9.2.2 Quenching TestHeat the coating article in an ovenfor a sufficient time to reach 150 6 10C (300 6 20F) andquench in room-temperature water. The adhesion is inadequateif the coating blisters, cracks, or peels.9.2.3 Reflow TestParts may be evaluated by immersion ina bath of palm o
47、il at a temperature of 205 260C (400 500F) until the deposit melts. A bright coating completelycovering the significant surfaces indicates adequate adhesion.9.2.4 Bend TestBend a sample, with the coated surfaceaway, over a mandrel until its two legs are parallel. Themandrel shall have a diameter equ
48、al to the thickness of thesample. Examination at 43 magnification should show noevidence of peeling or cracking.9.3 Solderability:9.3.1 General:9.3.1.1 Methods for testing the solderability of tin-leadcoated articles are based on the measurement of the extent ofwetting by molten solder or the determ
49、ination of the minimumtime required to produce full or perfect wetting by solder.9.3.1.2 The extent of wetting can be observed by manual orautomatic immersion in molten solder under controlled condi-tions.9.3.1.3 Determine the minimum wetting time by carrying aspecimen in a fixture through a standing wave of solder at acontrolled speed and by measuring the shortest time ofimmersion that will give complete wetting.9.3.2 Dip Tests (Non-Automated):9.3.2.1 SampleFor small articles of suitable shape andsize take the whole article for testing. For larger art
