1、Designation: B679 98 (Reapproved 2015)Standard Specification forElectrodeposited Coatings of Palladium for EngineeringUse1This standard is issued under the fixed designation B679; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers requirements for electrodepos-ited palladium coatings containing at least 99.7 mass
3、 % ofpalladium metal. Composite coatings consisting of palladiumwith a thin gold overplate for applications involving electricalcontacts are also covered.1.2 PropertiesPalladium is the lightest and least noble ofthe platinum group metals. It has a specific gravity of 12.0,which is substantially less
4、 than gold (19.3) and platinum(21.5). This yields a greater volume or thickness of coatingand, consequently, some saving of metal weight accompaniedby a small sacrifice in corrosion resistance and reflectivity. Thefollowing table compares the hardness range of electrodepos-ited palladium with other
5、electrodeposited noble metals andalloys (1,2).2Approximate Hardness (HK25)Gold 50250Palladium 75600Platinum 150550Palladium-Nickel 300650Rhodium 7501100Ruthenium 60013001.3 The values stated in SI units are the preferred values.Values provided in parentheses are for information only.1.4 This standar
6、d 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 regulatory limitations prior to use.2. Referenced Documents2.1 The
7、following standards form a part of this specificationto the extent referenced herein:2.2 ASTM Standards:3B183 Practice for Preparation of Low-Carbon Steel forElectroplatingB242 Guide for Preparation of High-Carbon Steel for Elec-troplatingB254 Practice for Preparation of and Electroplating onStainle
8、ss SteelB281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Conversion CoatingsB322 Guide for Cleaning Metals Prior to ElectroplatingB343 Practice for Preparation of Nickel for Electroplatingwith NickelB374 Terminology Relating to ElectroplatingB481 Practice for Prep
9、aration of Titanium and TitaniumAlloys for ElectroplatingB482 Practice for Preparation of Tungsten and TungstenAlloys for ElectroplatingB487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination ofCross SectionB488 Specification for Electrodeposited Coatings of
10、 Goldfor Engineering UsesB489 Practice for Bend Test for Ductility of Electrodepos-ited and Autocatalytically Deposited Metal Coatings onMetalsB499 Test Method for Measurement of Coating Thicknessesby the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis Metals1This specification is under the j
11、urisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.04 on Precious Metal Coatings.Current edition approved Nov. 1, 2015. Published December 2015. Originallyapproved in 1980. Last previous edition approved in 2009 as B679 98(2009). D
12、OI:10.1520/B0679-98R15.2The boldface numbers in parentheses refer to the list of references at the end ofthis specification.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
13、efer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1B507 Practice for Design of Articles to Be Electroplated onRacksB542 Terminology Relating to Electrical Contacts and TheirU
14、seB558 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 Thicknessby X-Ray SpectrometryB571 Practice for Qualitative Adhesion Testing of MetallicCoatingsB602 Test
15、 Method for Attribute Sampling of Metallic andInorganic CoatingsB689 Specification for Electroplated Engineering NickelCoatingsB697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic CoatingsB741 Test Method for Porosity In Gold Coatings On MetalSubstrates
16、 By Paper Electrography (Withdrawn 2005)4B748 Test Method for Measurement of Thickness of Metal-lic Coatings by Measurement of Cross Section with aScanning Electron MicroscopeB762 Test Method of Variables Sampling of Metallic andInorganic CoatingsB765 Guide for Selection of Porosity and Gross Defect
17、 Testsfor Electrodeposits and Related Metallic CoatingsB799 Test Method for Porosity in Gold and PalladiumCoatings by Sulfurous Acid/Sulfur-Dioxide VaporB809 Test Method for Porosity in Metallic Coatings byHumid Sulfur Vapor (“Flowers-of-Sulfur”)D1125 Test Methods for Electrical Conductivity and Res
18、is-tivity of WaterD3951 Practice for Commercial Packaging3. Terminology3.1 DefinitionsMany terms used in this specification aredefined in Terminology B374 or B542.3.2 Definitions of Terms Specific to This Standard:3.2.1 underplatinga metallic coating layer between thebasis metal or substrate and the
19、 topmost metallic coating. Thethickness of an underplating is usually greater than 1 m (40in.), in contrast to a strike or flash.4. Classification4.1 Orders for articles to be plated in accordance with thisspecification shall specify the plating system, indicating thebasis metal, the thickness of th
20、e underplatings, the thickness ofthe palladium coating, and the grade of the gold overplatingaccording to Tables 1 and 2.5. Ordering Information5.1 In order to make the application of this standardcomplete, the purchaser needs to supply the following infor-mation to the seller in the purchase order
21、or other governingdocument:5.1.1 The name, designation, and date of issue of thisstandard.5.1.2 The coating system including basis metal, thicknessclass and gold overplate grade (see 4.1 and Tables 1 and 2).5.1.3 Presence, type, and thickness of underplating (see3.2.1).5.1.4 Significant surfaces sha
22、ll be defined (see 3.1).5.1.5 Requirements, if any, for porosity testing (see 9.5):5.1.6 Requirement, if any, for bend ductility testing (see9.6):5.1.7 Sampling plan employed (see Section 8), and5.1.8 Requirement, if any, for surface coating cleanliness(absence of residual salts). See Appendix X3.6.
23、 Manufacture6.1 Any process that provides an electrodeposit capable ofmeeting the specified requirements will be acceptable.6.2 Substrate:6.2.1 The surface condition of the basis metal should bespecified and should meet this specification prior to the platingof the parts.6.2.2 Defects in the surface
24、 of the basis metal, such asscratches, porosity, pits, inclusions, roll and die marks, laps,cracks, burrs, cold shuts, and roughness may adversely affectthe appearance and performance of the deposit, despite theobservance of the best plating practice. Any such defects onsignificant surfaces should b
25、e brought to the attention of thesupplier and the purchaser.6.2.3 Clean the basis metal as necessary to ensure a satis-factory surface for subsequent electroplating in accordancewith Practices B183, B254, B281, B322, B343, B481, B482,and B558, and Guide B242.6.2.4 Proper preparatory procedures and t
26、horough cleaningof the basis metal are essential for satisfactory adhesion andperformance of these coatings. The surface must be chemicallyclean and continuously conductive, that is, without inclusions4The last approved version of this historical standard is referenced onwww.astm.org.TABLE 1 Thickne
27、ss ClassAThickness Class Minimum Thickness of Pd (m)0.08 0.080.15 0.150.25 0.250.50 0.500.75 0.751.00 1.001.25 1.251.5 1.52.5 2.53.0 3.05.0 5.0ASee Appendix X4 for specific applications of the various thickness classes.TABLE 2 Gold OverplateAGrade Type MIL-G-45204 Hardness (Code)ThicknessRange0 No O
28、verplate . . . . . . . . .1 1 (99.9 % Au min) III 90 HK25max (A) 0.05-0.12 m2 2 (99.7 % Au min) I 130-200 HK25(C) 0.05-0.25 mASee Specification B488 and Appendix X1.B679 98 (2015)2or other contaminants.The coatings must be smooth and as freeof scratches, gouges, nicks, and similar imperfections aspo
29、ssible.NOTE 1A metal finisher can often remove defects through specialtreatments such as grinding, polishing, abrasive blasting, chemicaltreatments, and electropolishing. However, these may not be normal in thetreatment steps preceding the plating, and a special agreement is indicated.6.3 Apply the
30、coating after all basis metal preparatorytreatments and mechanical operations on significant surfaceshave been completed.6.4 Racking:6.4.1 Position parts to allow free circulation of solution overall surfaces. The location of rack or wire marks in the coatingshould be agreed upon between the produce
31、r and supplier.6.5 Plating Process:6.5.1 Nickel UnderplatingApply a nickel underplatingbefore the palladium when the product is made from copper orcopper alloy. Nickel underplatings are also applied for otherreasons. See Appendix X2.NOTE 2In certain instances where high frequency analog signals aree
32、mployed, such as wave guides, the magnetic properties of nickel mayattenuate the signal. Palladium itself is non-ferromagnetic.6.5.2 StrikesStandard practice calls for a gold or palla-dium strike to follow any underplate or substrate (other thansilver or platinum) immediately prior to applying the p
33、alla-dium.6.5.3 PlatingGood practice calls for the work to beelectrically connected when entering the bath. A minimum of0.5 V is suggested. During electroplating it is extremelyimportant to maintain the voltage, current density, or bothbeneath the value for hydrogen evolution. (See 7.2)6.5.4 Stress
34、CrackingProblems associated with the incor-poration of hydrogen in the palladium, which can lead to stresscracking of the coating, shall be controlled by choosing platingbaths and plating conditions that minimize the H/Pd depositionratio (3) . The presence of stress-induced microcracks thatpenetrate
35、 to the underlying substrate or underplating can bedetected with one of the porosity tests specified in 9.5.6.5.5 Gold OverplatingApply a thin gold overplating afterthe palladium in any application in which palladium platedelectrical connectors are mated together in a contact pair. Thisprocess is ne
36、cessary to preserve the performance of the contactsurface. See Appendix X1 for other reasons for using a goldoverplate.NOTE 3When using Type 1 gold, the thickness of the gold overplateshall not exceed 0.12 m (5 in.) due to increased risk of degradingdurability and increasing the coefficient of frict
37、ion.6.5.6 Residual SaltsFor rack and barrel platingapplications, residual plating salts can be removed from thearticles by a clean, hot (50 to 100C) water rinse. A minimumrinse time of 2.5 min (racks) or 5 min (barrel) is suggested.Best practice calls for a minimum of three dragout rinses andone run
38、ning rinse with dwell times of 40 s in each station whenrack plating and 80 s when barrel plating. Modern high-velocity impingement type rinses can reduce this time to a fewseconds. This is particularly useful in automatic reel-to-reelapplications where dwell times are significantly reduced. SeeAppe
39、ndix X3.7. Coating Requirements7.1 Nature of CoatingThe palladium deposit shall haveminimum purity of 99.7 mass %.7.2 AppearancePalladium coatings shall be coherent,continuous, and have a uniform appearance to the extent thatthe nature of the basis metal and good commercial practicespermit.7.3 Thick
40、nessEverywhere on the significant surface (see5.1.4), the thickness of the palladium coating shall be equal toor exceed the specified thickness. The maximum thickness,however, shall not exceed the drawing tolerance.NOTE 4The coating thickness requirement of this specification is aminimum requirement
41、; that is, the coating thickness is required to equal orexceed the specified thickness everywhere on the significant surfaceswhile conforming to all maximum thickness tolerances given in theengineering drawing.Variation in the coating thickness from point to pointon a coated article is an inherent c
42、haracteristic of electroplating processes.Therefore, the coating thickness will have to exceed the specified value atsome points on the significant surfaces to ensure that the thickness equalsor exceeds the specified value at all points. Hence, in most cases, theaverage coating thickness on an artic
43、le will be greater than the specifiedvalue; how much greater is largely determined by the shape of the article(see Practice B507) and the characteristics of the plating process.In addition, the average coating thickness on articles will vary fromarticle to article within a production lot. Therefore,
44、 if all of the articles ina production lot are to meet the thickness requirement, the average coatingthickness for the production lot as a whole will be greater than the averagenecessary to assure that a single article meets the requirement.7.4 AdhesionThe palladium coatings shall be adherent tothe
45、substrate, when tested by one of the procedures summa-rized in 9.4.7.5 Integrity of the Coating:7.5.1 Gross Defects/Mechanical DamageThe coatingsshall be free of visible mechanical damage and similar grossdefects when viewed at magnifications up to 10. For someapplications this requirement may be re
46、laxed to allow for asmall number of such defects (per unit area), especially if theyare outside of or on the periphery of the significant surfaces.See 7.5.2 and 6.5.4.7.5.2 PorosityAlmost all as-plated electrodeposits containsome porosity, and the amount of porosity to be expected forany one type of
47、 coating will increase with decreasing thethickness of that particular coating type. The amount ofporosity in the coating that may be tolerable depends on theseverity of the environment that the article is likely toencounter during service or storage. If the pores are few innumber, or away from the
48、significant surfaces, their presencecan often be tolerated. Acceptance or pass-fail criteria, ifrequired, shall be part of the product specification for theparticular article or coating requiring the porosity test. See 9.5.NOTE 5Extensive reviews of porosity and porosity testing can befound in the l
49、iterature (4, 5).8. Sampling8.1 The sampling plan used for the inspection of a quality ofthe coated articles shall be as agreed upon between thepurchaser and the supplier.NOTE 6Usually, when a collection of coated articles, the inspectionlot (see 8.2), is examined for compliance with the requirements placed onB679 98 (2015)3the articles, a relatively small number of the articlesthe sampleisselected at random and is inspected. The inspection lot is then classified ascomplying or not complying with the requirements based on the results ofthe ins
