1、Designation: B984 12Standard Specification forElectrodeposited Coatings of Palladium- Cobalt Alloy forEngineering Use1This standard is issued under the fixed designation B984; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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-cobalt alloy coatings containing approxima
3、tely80% of palladium and 20% of cobalt. Composite coatingsconsisting of palladium-cobalt with a thin gold overplate forapplications involving electrical contacts are also covered.Palladium and palladium-cobalt remain competitive finishesfor high reliability applications.1.2 PropertiesPalladium is th
4、e lightest and least noble ofthe platinum group metals (1)2. IIt has the density of 12 gm percubic centimeter, specific gravity of 12.0, that is substantiallylower than the density of gold, 19.29 gm per cubic centimeter,specific gravity 19.3, and platinum 21.48 gm per cubiccentimeter, specific gravi
5、ty 21.5. The density of cobalt on theother hand is even less than palladium. It is only 8.69 gm percubic centimeter, specific gravity 8.7. This yields a greatervolume or thickness of coating and, consequently, some savingof metal weight and reduced cost. Palladium-cobalt coatedsurface provides a har
6、d surface finish (ASTM E18) thusdecreasing wear and increasing durability. Palladium-cobaltcoated surface also has very low coefficient of friction 0.43compared to hard gold 0.60 thus providing lower mating andunmating forces for electrical contacts (1)2. Palladium-cobalthas smaller grain size (ASTM
7、 E112), 50 150 Angstroms,compared to Hard Gold 200 250 Angstroms (1)2.515nanometer, compared to hard gold 20 25 nanometer (1)2.Palladium-cobalt has low porosity (ASTM B799) 0.2 porosityindex compared to hard gold 3.7 porosity index (1)2.Palladium-cobalt coated surface has higher ductility (ASTMB489)
8、 3-7 than that of hard gold 3 (1)2. The palladium-cobaltcoated surface is also thermally more stable 395C than hardgold 150C, and silver 170C. The following Table 1 comparesthe hardness range of electrodeposited palladium-cobalt withother electrodeposited noble metals and alloys (3,4).2TABLE 1 - Har
9、dness of Noble MetalsApproximate Hardness (HK25)Gold 50250Palladium 75600Platinum 150550Palladium-Nickel 300650Palladium-Cobalt 500650Rhodium 7501100Ruthenium 60013001.3 UnitsThe values stated in SI units are to be regardedas standard. No other units of measurement are included in thisstandard.1.4 T
10、his 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 regulatory limitations prior to use. Some specifichazard
11、s statements are given in Section 7 on Hazards.2. Referenced Documents2.1 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 onStainless SteelB281 Pr
12、actice 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 Preparation of Tita
13、nium 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 Section1This specification is under the jurisdiction of ASTM Committee B0
14、8 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.08.02 on Precious Metal Coatings.Current edition approved May 1, 2012. Published September 2012. DOI:10.1520/B0984-122The boldface numbers in parentheses refer to the list of references at the end ofthis specific
15、ation.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, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO
16、 Box C700, West Conshohocken, PA 19428-2959. United States1B488 Specification for Electrodeposited Coatings of Goldfor Engineering UsesB489 Practice for Bend Test for Ductility of Electrodepos-ited and Autocatalytically Deposited Metal Coatings onMetalsB499 Test Method for Measurement of Coating Thi
17、cknessesby the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis MetalsB507 Practice for Design of Articles to Be Electroplated onRacksB542 Terminology Relating to Electrical Contacts and TheirUseB558 Practice for Preparation of Nickel Alloys for Electro-platingB567 Test Method for Measurement
18、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 Method for Attribute Sampling of Metallic andInorganic CoatingsB679 Specification for Electrodeposit
19、ed Coatings of Palla-dium for Engineering UseB689 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 By Paper Electrogr
20、aphy (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 Testsfor Electrode
21、posits 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 Resis-tivity of WaterD
22、3951 Practice for Commercial PackagingE18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE112 Test Methods for Determining Average Grain Size3. Terminology3.1 DefinitionsMany terms used in this specification aredefined in Terminology B374 or B542.3.2 Definitions of Terms Specific to This S
23、tandard:3.2.1 underplating, na metallic coating layer between thebasis metal or substrate and the topmost metallic coating. Thethickness of underplating is usually greater than 1 m. For highenergy electrical contact the thickness may be 2.0 4.0 m.3.2.2 significant surfaces, ndefined as those normall
24、yvisible (directly or by reflector) or essential to the serviceabilityor function of the article. Can be the source of corrosionproducts or tarnish films that interfere with the function ordesirable appearance of the article. The significant surfacesshall be indicated on the drawings of the parts or
25、 by theprovision of suitable marked samples.4. Classification4.1 Orders for articles to be plated in accordance with thisspecification shall specify the plating system, indicating thebasis metal, the thickness of the underplatings, the thickness ofthe palladium-cobalt coating, and the grade of the g
26、oldoverplating according to Table 2 and Table 3.5. 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 or other governingdocument:5.1.1 The name, designation, and date of issue
27、 of thisstandard.5.1.2 The coating system including basis metal, thicknessclass and gold overplate grade (see 4.1 and Table 1 and Table2).5.1.3 Presence, type, and thickness of underplating (see3.2.1).5.1.4 Significant surfaces shall be defined (see 3.2.2).5.1.5 Requirements, if any, for porosity te
28、sting (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. Materials and Manufacture6.1 Any process that provides an electrod
29、eposit 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.4The last approved version of this historical standard is referenced onwww.astm.o
30、rg.TABLE 2 Thickness ClassAThickness Class Minimum Thickness of Pd-Co (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 X4.1 for specific applications of the various thickness classes.B984 1226.2.2 Defects in the surface of the basis metal, such asscr
31、atches, 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 be brought to the attention of t
32、hesupplier and the purchaser (See Note 1).6.2.3 Proper preparatory procedures and thorough cleaningof the basis metal are essential for satisfactory adhesion andperformance of these coatings. The surface must be chemicallyclean and continuously conductive, that is, without inclusionsor other contami
33、nants.The coatings must be smooth and as freeof scratches, gouges, nicks, and similar imperfections aspossible.6.2.4 The base materials are to be cleaned and prepared asnecessary to ensure good Pd-Co plating. The base materialpreparation may be accomplished in accordance with PracticesB183, B254, B2
34、81, B322, B343, B481, B482, and B558, andGuide B242.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
35、special agreement is indicated.6.3 Apply the 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 (ASTM B507). The location of rack or wire mark
36、sin the coating should be agreed upon between the purchaserand supplier.6.5 Plating Process:6.5.1 Nickel UnderplatingThe nickel underplating(ASTM B689) must be applied before the palladium-cobaltalloy plating when the product is made from copper or copperalloy. Nickel underplatings are also applied
37、for other reasons.See Appendix X2.6.5.2 Palladium-Cobalt OverplatingThe electrodeposi-tion process produces mechanically stable Pd-Co films atcurrent densities from less than 50 mA/cm2to greater than 700mA/cm2. It can produce alloys of 10 to 30 percent Cobaltcontent. Any desired composition (for exa
38、mple, 20% Co) cabbe maintained within 65 percent over a wide range ofoperating conditions and bath aging.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 vo
39、ltage, current density, or bothbeneath the value for hydrogen evolution, if possible.6.5.4 Stress CrackingProblems associated with the incor-poration of hydrogen in the palladium-cobalt, which can leadto stress cracking of the coating, shall be controlled bychoosing plating baths and plating conditi
40、ons that minimize theH/Pd-Co deposition ratio. The presence of stress-inducedmicrocracks that penetrate to the underlying substrate orunderplating can be detected with one of the porosity testsspecified in 9.5.6.5.5 Gold OverplatingA thin gold overplating after thepalladium-cobalt can be applied in
41、an application in which goldplated electrical connectors are mated together in a contactpair. This process is necessary to preserve the performance ofthe contact surface. See Appendix X1 for other reasons forusing a gold overplate.6.5.6 Residual SaltsFor rack and barrel platingapplications, residual
42、 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 running rinse with dwell times of 40 s in each station whenrack plating and
43、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. SeeAppendix Appendix X3.7. Coating Requirements7.1 Coating CompositionThe prefer
44、red palladium-cobaltalloy composition should be 80% palladium and 20% cobalt;however the palladium (ASTM B679) content should never beless than 70% and the cobalt should never be more than 30%.7.2 AppearancePalladium-cobalt coatings shall besmooth, uniform and continuous in appearance with no cracks
45、,pits, nodules, blisters, roughness, excessive edge buildup, areasof no plating, burned deposits or any other unwanted visibleplating irregularity. The examination should be done with theunaided eye and under 10X magnification.7.3 ThicknessEverywhere on the significant surface (see5.1.4), the thickn
46、ess of the palladium coating shall be equal toor exceed the specified thickness. The maximum thickness,however, shall not exceed the drawing tolerance (see Note 3and Note 2).NOTE 2The coating thickness requirement of this specification is aminimum requirement; that is, the coating thickness is requi
47、red 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 characteristic of electroplating processes
48、.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 article will be greater than the specifiedvalu
49、e; how much greater is largely determined by the shape of the article(see Practice B507) and the characteristics of the plating process.NOTE 3In addition, the average coating thickness on articles will varyfrom article to article within a production lot. Therefore, if all of thearticles in a production lot are to meet the thickness requirement, theaverage coating thickness for the production lot as a whole will be greaterthan the average necessary to assure that a single article meets therequirement.TABLE 3 Gold OverplateAGrade Type MIL-G-45204H
