1、Designation: B545 97 (Reapproved 2009)Standard Specification forElectrodeposited Coatings of Tin1This standard is issued under the fixed designation B545; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、 number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 covers the requirements for electr
3、ode-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-galling properties, and to bea stopoff coating in the nitriding of high-strength
4、 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 coating (such as pores) due togalvanic couples formed between the tin and the
5、 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 be assembled safely incontact with iron and steel, tin-coated aluminum, y
6、ellowchromated 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 forspecial purposes, as stated in X6.3) obtained from any of theavailable tin elect
7、roplating 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 A623or A623M.1.5 The values stated in SI units are to be regarded as thestandard. The values
8、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-priate safety and health practices and determine the applica-bility of regula
9、tory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A623 Specification for Tin Mill Products, General Require-mentsA623M Specification for Tin Mill Products, General Re-quirements MetricB32 Specification for Solder MetalB183 Practice for Preparation of Low-Carbon Steel forElectr
10、oplatingB242 Guide for Preparation of High-Carbon Steel for Elec-troplatingB246 Specification for Tinned Hard-Drawn and Medium-Hard-Drawn Copper Wire for Electrical PurposesB281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Conversion CoatingsB320 Practice for Prepa
11、ration of Iron Castings for Electro-platingB322 Guide for Cleaning Metals Prior to ElectroplatingB374 Terminology Relating to ElectroplatingB487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination of CrossSectionB499 Test Method for Measurement of Coating Thi
12、ck-nesses by the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis MetalsB504 Test Method for Measurement of Thickness of Me-tallic Coatings by the Coulometric MethodB507 Practice for Design of Articles to Be Electroplated onRacksB542 Terminology Relating to Electrical Contacts andTheir UseB558
13、 Practice for Preparation of Nickel Alloys for Electro-platingB567 Test Method for Measurement of Coating Thicknessby the Beta Backscatter MethodB568 Test Method for Measurement of Coating Thickness1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings
14、and is the direct responsibility of SubcommitteeB08.08.04 on Soft Metals.Current edition approved Sept. 1, 2009. Published December 2009. Originallyapproved in 1971. Last previous edition approved in 2004as B545 97 (2004)1.DOI: 10.1520/B0545-97R09_WIP_#857992.2For referenced ASTM standards, visit th
15、e 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 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,
16、United States.by X-Ray SpectrometryB571 Practice for Qualitative Adhesion Testing of MetallicCoatingsB602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB659 Guide for Measuring Thickness of Metallic and Inor-ganic CoatingsB678 Test Method for Solderability of Metallic-CoatedPro
17、ductsB697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic CoatingsB762 Test Method of Variables Sampling of Metallic andInorganic CoatingsB765 Guide for Selection of Porosity and Gross DefectTests for Electrodeposits and Related Metallic CoatingsB809 Te
18、st Method for Porosity in Metallic Coatings byHumid Sulfur Vapor (“Flowers-of-Sulfur”)B849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen EmbrittlementB850 Guide for Post-Coating Treatments of Steel for Re-ducing the Risk of Hydrogen EmbrittlementB851 Specification fo
19、r Automated Controlled Shot Peeningof Metallic Articles Prior to Nickel, Autocatalytic Nickel,or Chromium Plating, or as Final FinishD3951 Practice for Commercial Packaging3. Terminology3.1 DefinitionsMany of the terms used in this specifica-tion are defined in Terminology B374 or B542.3.1.1 rack-pl
20、atingan 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 coating is required to meet all of therequirements of the coating specification for that artic
21、le;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 desirable appearance of the article; significantsurfaces shall be indicated on the drawings o
22、f 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 basis metal or substrate and the topmost metalliccoating or coatings. The thickness of suc
23、h 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 accordancewith this specification shall specify the service class (4.2) (andunderplating, if
24、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 Minimum Thickness Typical ApplicationsA 2.5 m (100 in.) Mild service conditions, particularly
25、 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 operation of the product (for ex-ample, small electrical spring contacts and re-lays). Class A
26、 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 (below). Applications areas follows: precoating on solderable basis met-als to facilitate the
27、 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 in.)for steel substrates)Moderate exposure conditions, usually indoors,but more severe tha
28、n 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 duringstorage.D 15 m (600 in.)(20 m (800 in.)for steel substrates)Severe service, including expo
29、sure 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.E 30 m (0.0012 in.) Very severe service conditions, including el-evated temperatures, whe
30、re 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 corrosive liquids or corrosive atmo-spheres or gases. Thicker coatings are used forwater co
31、ntainers, 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 and short shelf-life requirements,subject to purchaser approval.4.3 Surface Appearance Type
32、 (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 brightening agents. However, all matte baths(except for stannate baths) do require the addi
33、tion 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 specificbright tin plating baths.4.3.3 Flow-Brightened ElectrodepositsFlow-brightenedcoatings
34、 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 6 8C (500 6 14F),but other heating methods also are in use, such as hot air. Themaximum t
35、hickness 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.B545 97 (2009)2NOTE 1Terms commonly used in soldering, such as dewet, aredescribed in solde
36、ring 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 supply the following informationto the seller in the purchase order and drawings:5.1.1 Title
37、, 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-strate to be coated (6.1);5.1.4 Additional underplating, if required (6.8);5.1.5 Surface-appeara
38、nce 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 Requirement S2); and5.1.8 Any other items needing agreement (for example,6.5.2 and 8.5).6. Coating Requ
39、irements6.1 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 preparation of metal surfaces is necessary in order toassure good adhesion and quality. For suitab
40、le methods, see PracticesB183, B242, B281, B320, B322, and B558. Also see 6.6.6.2 Electroplating shall be applied after all basis metal heattreatments and mechanical operations have been completed.6.3 AppearanceTin coatings shall have the characteristicappearance, including surface texture (4.3), fo
41、r 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 unplatedareas. They shall not be stained or discolored. Flow-brightenedcoatings shall be free of dewette
42、d 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 samples showing the finish shallbe supplied to and approved by the purchaser. Where a contactmark is in
43、evitable, 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 as to theminimum thickness on significant surfaces.6.5.1 Local ThicknessThe thickness values specif
44、ied in4.2 are the minimum local thicknesses measured by one ormore of the methods given in Practice B659 at any number ofdesired spots on the significant surface.6.5.2 Mean ThicknessWhen specified by the purchaser,instead of being a local minimum requirement, the thicknessrequirement can be a minimu
45、m (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 terminals.NOTE 4Thickness of electrodeposited coatings varies from point topoint on the surfaces of a pr
46、oduct (see Practice B507). 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 electroplater will have to use special techniques that probablywill increase the cost of the process
47、.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 thickness.6.6 AdhesionAdhesion of the coating shall be tested byone of the methods given in Appendix
48、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 Coating:6.7.1 Gross Defects/Mechanical DamageCoatings shallbe free of visible mechanical damage and similar
49、 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 thearticle is likely to encounter during service or storage. If thepores are few in number, or away f
