1、Designation: B 545 97 (Reapproved 2004)e1Standard Specification forElectrodeposited Coatings of Tin1This standard is issued under the fixed designation B 545; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. 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.e1NOTEThe warning note in S4.1 was editorially updated in Ap
3、ril 2004.1. Scope1.1 This specification covers the requirements for electrode-posited (electroplated) coatings of tin applied to metallicarticles. Tin coatings are used to provide a low contact-resistance surface, to protect against corrosion (see 1.2), tofacilitate soldering, to provide anti-gallin
4、g properties, and to bea stopoff coating in the nitriding of high-strength steels.1.2 Some corrosion can be expected from tin coatingsexposed outdoors. In normal indoor exposure, tin is protectiveon iron, steel, nickel, copper, and their alloys. Corrosion can beexpected at discontinuities in the coa
5、ting (such as pores) due togalvanic couples formed between the tin and the underlyingmetal through the discontinuities, especially in humid atmo-spheres. Porosity increases as the coating thickness decreases,so that minimum thicknesses must be specified for eachapplication. Parts coated with tin can
6、 be assembled safely incontact with iron and steel, tin-coated aluminum, yellowchromated zinc, cadmium, and solder coatings. (See X5.2 foroxidation and corrosion properties.)1.3 This specification applies to electroplated coatings ofnot less than 99 % tin (except where deliberately alloyed forspecia
7、l purposes, as stated in X6.3) obtained from any of theavailable tin electroplating processes (see 4.3).1.4 This specification does not apply to hot-dipped tin orother non-electrodeposited coating; it also does not apply tomill products. For mill products, refer to Specifications A 623or A 623M.1.5
8、The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.6 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 establish appro-p
9、riate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 623 Specification for Tin Mill Products, General Require-mentsA 623M Specification for Tin Mill Products, General Re-quirements MetricB 32 Specificat
10、ion for Solder MetalB 183 Practice for Preparation of Low-Carbon Steel forElectroplatingB 242 Practice for Preparation of High-Carbon Steel forElectroplatingB 246 Specification for Tinned Hard-Drawn and Medium-Hard-Drawn Copper Wire for Electrical PurposesB 281 Practice for Preparation of Copper and
11、 Copper-BaseAlloys for Electroplating and Conversion CoatingsB 320 Practice for Preparation of Iron Castings for Electro-platingB 322 Practice for Cleaning Metals Prior to ElectroplatingB 374 Terminology Relating to ElectroplatingB 487 Test Method for Measurement of Metal and OxideCoating Thicknesse
12、s by Microscopical Examination of aCross SectionB 499 Test Method for Measurement of Coating Thick-nesses by the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis MetalsB 504 Test Method for Measurement of Thickness of Me-tallic Coatings by the Coulometric MethodB 507 Practice for Design of Art
13、icles to be Electroplated onRacksB 542 Terminology Relating to Electrical Contacts andTheir UseB 558 Practice for Preparation of Nickel Alloys for Electro-platingB 567 Test Method for Measurement of Coating Thicknessby the Beta Backscatter MethodB 568 Test Method for Measurement of Coating Thickness
14、1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.08.04 on Soft Metals.Current edition approved April 1, 2004. Published April 2004. Originallyapproved in 1971. Last previous edition approved in 1
15、997 as B 545 97e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Har
16、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.by X-Ray SpectrometryB 571 Practice for Qualitative Adhesion Testing of MetallicCoatingsB 602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB 659 Guide for Measuring Thickness of Metallic andInorganic Coati
17、ngsB 678 Test Method for Solderability of Metallic-CoatedProductsB 697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic CoatingsB 762 Test Method of Variables Sampling of Metallic andInorganic CoatingsB 765 Guide for Selection of Porosity and Gross Defec
18、tTests for Electrodeposits and Related Metallic CoatingsB 809 Test Method for Porosity in Metallic Coatings byHumid Sulfur Vapor (“Flowers-of-Sulfur”)B 849 Specification for Pre-Treatments of Iron or Steel forReducing the Risk of Hydrogen EmbrittlementB 850 Specification for Post-Coating Treatments
19、of Iron orSteel for Reducing the Risk of Hydrogen EmbrittlementB 851 Specification for Automated Controlled Shot Peeningof Metallic Articles Prior to Nickel, Autocatalytic Nickel,or Chromium Plating, or as a Final FinishD 3951 Practice for Commercial Packaging3. Terminology3.1 DefinitionsMany of the
20、 terms used in this specifica-tion are defined in Terminology B 374 or B 542.3.1.1 rack-platingan electrodeposition process in whicharticles to be coated are mounted on racks or other fixturesduring the process.3.1.2 significant surfacethat portion of the surface of acoated article at which the coat
21、ing is required to meet all of therequirements of the coating specification for that article;significant surfaces are usually those that are essential to theserviceability or function of the article, or that can be a sourceof corrosion products or tarnish films that interfere with thefunction or des
22、irable appearance of the article; significantsurfaces shall be indicated on the drawings of the parts or bythe provision of suitably marked samples.3.1.3 undercoating (see 3.1.4)also called an underplate inthe electronics industry.3.1.4 underplatingapplication of a metallic coating layerbetween the
23、basis metal or substrate and the topmost metalliccoating or coatings. The thickness of such an undercoating isusually greater than 0.8 m (30 in.). This is in contrast tostrikes or flashes, whose thicknesses are generally muchsmaller.4. Classification4.1 GeneralOrders for articles to be plated in acc
24、ordancewith this specification shall specify the service class (4.2) (andunderplating, if required), indicating the severity of servicerequired for the coating. Other coatings variations, such assurface appearance type (4.3) or alloy composition (AppendixX6), are optional.4.2 Service Class:Class Min
25、imum Thickness Typical ApplicationsA 2.5 m (100 in.) Mild service conditions, particularly where thesignificant surface is shielded from the atmo-sphere (as in electronic connector housings). Toprovide corrosion and tarnish resistance wheregreater thicknesses may be detrimental to themechanical oper
26、ation of the product (for ex-ample, small electrical spring contacts and re-lays). Class A is often used for tin coatings thatare not to be soldered, but must function aslow-resistance electrical contact surfaces.B 5 m (200 in.) Mild service conditions with less severe require-ments than Class C (be
27、low). Applications areas follows: precoating on solderable basis met-als to facilitate the soldering of electrical com-ponents; as a surface preparation for protectivepainting; for antigalling purposes; and as a sto-poff in nitriding. Also found on baking pans afterreflow.C 8 m (320 in.),(10 m (400
28、in.)for steel substrates)Moderate exposure conditions, usually indoors,but more severe than Class B. Examples areelectrical hardware (such as cases for relaysand coils, transformer cans, screened cages,chassis, frames, and fittings) and for retentionof the solderability of solderable articles during
29、storage.D 15 m (600 in.)(20 m (800 in.)for steel substrates)Severe service, including exposure to damp-ness and mild corrosion from moderate indus-trial environments. Examples are fittings for gasmeters, automotive accessories (such as aircleaners and oil filters), and in some electronicapplications
30、.E 30 m (0.0012 in.) Very severe service conditions, including el-evated temperatures, where underlying metaldiffusion and intermetallic formation processesare accelerated. Thicknesses of 30 to 125 m(0.0012 to 0.005 in.) may be required if thecoating is subjected to abrasion or is exposedto slowly c
31、orrosive liquids or corrosive atmo-spheres or gases. Thicker coatings are used forwater containers, threaded steel couplings of oildrilling strings, and seacoast atmospheres.Coatings subject to mild etchants are included.F 1.5 m (60 in.) Similar to Class A, but for shorter-term contactapplications a
32、nd short shelf-life requirements,subject to purchaser approval.4.3 Surface Appearance Type (Electroplating Process):4.3.1 Matte Tin ElectrodepositsCoatings with a matteappearance are obtained from tin plating baths (stannate,sulfate, methylsulfonate, and fluoborate) used without theaddition of any b
33、rightening agents. However, all matte baths(except for stannate baths) do require the addition of grain-refiners, and often of other additives in order to produce thedesired matte finish.4.3.2 Bright Tin ElectrodepositsBright coatings are ob-tained when proprietary brightening agents are used in spe
34、cificbright tin plating baths.4.3.3 Flow-Brightened ElectrodepositsFlow-brightenedcoatings are obtained by heating the matte coating above themelting point of tin for a few seconds, followed by quenching;palm oil and hydrogenated oils and fats are used as heat-transfer medium at a temperature of 260
35、 6 8C (500 6 14F),but other heating methods also are in use, such as hot air. Themaximum thickness for flow-brightening is, in most cases,approximately 8 m (300 in.); thicker coatings tend to dewet.The shape of the part is also a factor; flat surfaces dewet morereadily than wires or rounded shapes.B
36、 545 97 (2004)e12NOTE 1Terms commonly used in soldering, such as dewet, aredescribed in soldering textbooks (1)3or reviews of solderability testing(2). Some examples are given in Appendix X6.5. Ordering Information5.1 In order to make the application of this specificationcomplete, the purchaser must
37、 supply the following informationto the seller in the purchase order and drawings:5.1.1 Title, ASTM designation number, and year of issue ofthis specification;5.1.2 Deposit by classification (4.1), including thickness orservice class (4.2);5.1.3 Composition and metallurgical condition of the sub-str
38、ate to be coated (6.1);5.1.4 Additional underplating, if required (6.8);5.1.5 Surface-appearance type (for example, matte, flow-brightened, or bright), if required (4.3 and 6.2);5.1.6 Location of significant surfaces (3.1.2);5.1.7 Hydrogen embrittlement relief, if required (Supple-mentary Requiremen
39、t S2); and5.1.8 Any other items needing agreement (for example,6.5.2 and 8.5).6. Coating Requirements6.1 SubstrateThe metal substrate shall be subjected tosuch surface preparation, cleaning, and electroplating proce-dures as are necessary to yield deposits with the desiredquality.NOTE 2Careful prepa
40、ration of metal surfaces is necessary in order toassure good adhesion and quality. For suitable methods, see PracticesB 183, B 242, B 281, B 320, B 322, and B 558. Also see 6.6.6.2 Electroplating shall be applied after all basis metal heattreatments and mechanical operations have been completed.6.3
41、AppearanceTin coatings shall have the characteristicappearance, including surface texture (4.3), for the processused. The appearance shall be uniform throughout, insofar asthe basis metal will permit. They shall be adherent and visuallyfree of blisters, pits, peeled areas, cracks, nodules, and unpla
42、tedareas. They shall not be stained or discolored. Flow-brightenedcoatings shall be free of dewetted areas and beads. All surfacesshall be substantially free of grease or oil used in theflow-brightening process.6.4 All tin-coated articles shall be clean and undamaged.When necessary, preliminary samp
43、les showing the finish shallbe supplied to and approved by the purchaser. Where a contactmark is inevitable, its location shall be subject to agreementbetween the supplier and the purchaser.6.5 Thickness of CoatingsTin coatings on articles shallconform to the thickness requirements specified in 4.2
44、as to theminimum thickness on significant surfaces.6.5.1 Local ThicknessThe thickness values specified in4.2 are the minimum local thicknesses measured by one ormore of the methods given in Practice B 659 at any number ofdesired spots on the significant surface.6.5.2 Mean ThicknessWhen specified by
45、the purchaser,instead of being a local minimum requirement, the thicknessrequirement can be a minimum (arithmetic) mean thickness.NOTE 3Specification of the coating thickness in terms of the mean isnormally made when the coated articles are small and relatively simple,such as connector pins and term
46、inals.NOTE 4Thickness of electrodeposited coatings varies from point topoint on the surfaces of a product (see Practice B 507). The thickness isless in interior corners and holes. Such surfaces are normally exempt fromthe thickness requirement. If the full thickness is required on thesesurfaces, the
47、 electroplater will have to use special techniques that probablywill increase the cost of the process.NOTE 5When articles are plated by mass plating techniques (such asbarrel plating), such measurement methods as “strip and weigh” or “weighbefore and after plating” may be used to determine the mean
48、thickness.6.6 AdhesionAdhesion of the coating shall be tested byone of the methods given in Appendix X2. The coating shouldadhere to the basis metal when subjected to the agreed test;flaking or blistering of the coating is to be taken as evidence ofunsatisfactory adhesion.6.7 Integrity of the Coatin
49、g:6.7.1 Gross Defects/Mechanical DamageCoatings shallbe free of visible mechanical damage and similar gross defectswhen viewed at up to 43 magnification. For some applications,this requirement may be relaxed to allow for a small number ofsuch defects (per unit area), especially if they are outside of oron the periphery of significant surfaces (also see 6.7.2).6.7.2 PorosityAlmost all as-plated electrodeposits containsome porosity. The amount of porosity in the coating that maybe tolerable depends on the severity of the environment that t
