ASTM B832-1993(2018) Standard Guide for Electroforming with Nickel and Copper.pdf

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1、Designation: B832 93 (Reapproved 2018)Standard Guide forElectroforming with Nickel and Copper1This standard is issued under the fixed designation B832; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu

2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers electroforming practice and describesthe processing of mandrels, the design of electroformedarticles, and the use of co

3、pper and nickel electroplatingsolutions for electroforming.1.2 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, health, and environmental practices and deter-mi

4、ne the applicability of regulatory limitations prior to use.1.3 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations

5、 issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B183 Practice for Preparation of Low-Carbon Steel forElectroplatingB242 Guide for Preparation of High-Carbon Steel for Elec-troplatingB252 Guide for Preparation of Zinc Alloy

6、 Die Castings forElectroplating and Conversion CoatingsB253 Guide for Preparation of Aluminum Alloys for Elec-troplatingB254 Practice for Preparation of and Electroplating onStainless SteelB281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Conversion CoatingsB311 Te

7、st Method for Density of Powder Metallurgy (PM)Materials Containing Less Than Two Percent PorosityB343 Practice for Preparation of Nickel for Electroplatingwith NickelB374 Terminology Relating to ElectroplatingB489 Practice for Bend Test for Ductility of Electrodepos-ited and Autocatalytically Depos

8、ited Metal Coatings onMetalsB490 Practice for Micrometer Bend Test for Ductility ofElectrodepositsB558 Practice for Preparation of Nickel Alloys for Electro-platingB571 Practice for Qualitative Adhesion Testing of MetallicCoatingsB578 Test Method for Microhardness of Electroplated Coat-ingsB636 Test

9、 Method for Measurement of Internal Stress ofPlated Metallic Coatings with the Spiral ContractometerB659 Guide for Measuring Thickness of Metallic and Inor-ganic CoatingsB849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen EmbrittlementE8 Test Methods for Tension Testi

10、ng of Metallic MaterialsE384 Test Method for Microindentation Hardness of Mate-rials3. Summary of Electroforming Practice3.1 Electroforming is defined (see Terminology B374)asthe production or reproduction of articles by electrodepositionupon a mandrel or mold that is subsequently separated from the

11、deposit.3.2 The basic fabrication steps are as follows: a suitablemandrel is fabricated and prepared for electroplating; themandrel is placed in an appropriate electroplating solution andmetal is deposited upon the mandrel by electrolysis; when therequired thickness of metal has been applied, the me

12、tal-covered mandrel is removed from the solution; and the mandrelis separated from the electrodeposited metal. The electroformis a separate, free-standing entity composed entirely of elec-trodeposited metal. Electroforming is concerned with thefabrication of articles of various kinds.4. Significance

13、 and Use4.1 The specialized use of the electroplating process forelectroforming results in the manufacture of tools and productsthat are unique and often impossible to make economically by1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct

14、responsibility of Subcommittee B08.03 onEngineering Coatings.Current edition approved June 1, 2018. Published June 2018. Originallyapproved in 1993. Last previous edition approved in 2013 as B832 93(2013). DOI:10.1520/B0832-93R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org,

15、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 Box C700, West Conshohocken, PA 19428-2959. United StatesThis international

16、 standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1

17、traditional methods of fabrication. Current applications ofnickel electroforming include: textile printing screens; compo-nents of rocket thrust chambers, nozzles, and motor cases;molds and dies for making automotive arm-rests and instru-ment panels; stampers for making phonograph records, video-dis

18、cs, and audio compact discs; mesh products for makingporous battery electrodes, filters, and razor screens; and opticalparts, bellows, and radar wave guides (1-3).34.2 Copper is extensively used for electroforming thin foilfor the printed circuit industry. Copper foil is formed continu-ously by elec

19、trodeposition onto rotating drums. Copper is oftenused as a backing material for electroformed nickel shells andin other applications where its high thermal and electricalconductivities are required. Other metals including gold areelectroformed on a smaller scale.4.3 Electroforming is used whenever

20、the difficulty and costof producing the object by mechanical means is unusuallyhigh; unusual mechanical and physical properties are requiredin the finished piece; extremely close dimensional tolerancesmust be held on internal dimensions and on surfaces ofirregular contour; very fine reproduction of

21、detail and complexcombinations of surface finish are required; and the part cannotbe made by other available methods.5. Processing of Mandrels for Electroforming5.1 General Considerations:5.1.1 Mandrels may be classified as conductors or noncon-ductors of electricity, and each of these may be perman

22、ent,semipermanent, or expendable (Table 1).5.1.2 Whether or not a mandrel is a conductor will deter-mine the procedures required to prepare it for electroforming.Conductive mandrels are usually pure metals or alloys ofmetals and are prepared by standard procedures but mayrequire an additional thin p

23、arting film to facilitate separation ofthe electroform from the mandrel (unless the mandrel isremoved by melting or chemical dissolution).5.1.3 Whether or not a permanent or expendable mandrelshould be used is largely dependent on the particular articlethat is to be electroformed. If no reentrant sh

24、apes or angles areinvolved, it is possible to use permanent, rigid mandrels thatcan be separated from the finished electroform mechanicallyand reused. If reentrant angles and shapes are involved, it isnecessary to use mandrel materials that can be removed bymelting or by chemical dissolution, or mat

25、erials that arecollapsible, such as polyvinyl chloride and other plastics. Insome cases, multiple piece mandrels are used that can beremoved even with reentrant features.5.1.4 Many solid materials can be used to fabricate man-drels for electroforming, but the following generalizations mayhelp in sel

26、ecting a suitable material: permanent mandrels arepreferred for accuracy and for large production runs; expend-able mandrels must be used whenever the part is so designedthat a permanent mandrel cannot be withdrawn; and it isimportant that the mandrel retain its dimensional stability inwarm plating

27、baths. Wax and most plastics expand whenexposed to electroplating solutions operated at elevated tem-peratures. In such cases, it may be necessary to use acid copper,nickel sulfamate, and other electroplating solutions that func-tion at room temperature.5.2 Mandrel Design:5.2.1 The electroforming op

28、eration can often be simplifiedby design changes that do not impair the functioning of thepiece. Some of the design considerations are summarized in5.2.2, 5.2.3, 5.2.4, 5.2.5, and 5.2.6. Examples of mandrelshapes that may present problems during electroforming areillustrated in Fig. 1.5.2.2 Exterior

29、 (convex) angles should be provided with asgenerous a radius as possible to avoid excessive build up andtreeing of the deposit during electroforming. Interior (concave)angles on the mandrel should be provided with a fillet radius ofat least 0.05 cm per 5 cm (0.02 in. per 2 in.) of length of a sideof

30、 the angle.5.2.3 Whenever possible, permanent mandrels should betapered at least 0.08 mm per m (0.001 in. per ft) to facilitateremoval from the mandrel. (Where this is not permissible, themandrel may be made of a material with a high or lowcoefficient of thermal expansion so that separation can beef

31、fected by heating or cooling).5.2.4 A fine surface finish on the mandrel, achieved bylapping or by electropolishing, will generally facilitate separa-tion of mandrel and electroform. A finish of 0.05 m (2 in.)rms is frequently specified.5.2.5 Flat bottom grooves, sharp angle indentations, blindholes

32、, fins, v-shaped projections, v-bottom grooves, deepscoops, slots, concave recesses, and rings and ribs can causeproblems with metal distribution during electroforming unlessinside and outside angles and corners are rounded.5.2.6 An engineering drawing of the mandrel, the electro-formed article, and

33、 auxiliary equipment or fixture for separat-ing the electroform from the mandrel should be prepared. Thedrawing of the mandrel should provide for electrical connec-tions to be made in nonfunctional areas of the electroform. It3The boldface numbers in parentheses refer to the list of references at th

34、e end ofthis standard.TABLE 1 Types of Mandrel MaterialsTypes Typical MaterialsConductorsExpendable Low-melting point alloys; for example,bismuth-free 92 % tin and 8 % zincAluminum alloysZinc alloysPermanent NickelAustenitic StainlessInvar, KovarCopper and brassNickel-plated steelNickel/chromium-pla

35、ted aluminumNonconductorsExpendable WaxGlassPermanent (or Semi-Permanent) Rigid and collapsible plastic; forexample, epoxy resins and polyvinylchlorideWoodB832 93 (2018)2should provide reference points for and mechanical means ofholding if finish machining is necessary before removal of themandrel.5

36、.3 Mandrel Fabrication:5.3.1 The method of fabrication of the mandrel will dependon the type selected, the material chosen, and the object to beelectroformed. Mandrels may be manufactured by casting,machining, electroforming, and other techniques. Permanentmandrels can be made by any of the conventi

37、onal pattern-making processes.5.4 Preparing Non-Conducting Mandrels:5.4.1 Nonconducting mandrels must be made impervious towater and other processing solutions and then rendered con-ductive. Porous materials, for example, leather and plastic, maybe impregnated with wax, shellac, lacquer, or a synthe

38、tic resinformulation. It is often preferable to use thin films of lacquer toseal porous, nonmetallic mandrels.5.4.2 Nonconducting materials may be rendered conductiveby applying a chemically reduced film of silver, copper, ornickel to the surface. In general, these processes are carried outby sprayi

39、ng the reagent containing the metal ions of choicesimultaneously with a specific reducing agent onto the surfaceof the mandrel using a double-nozzle spray gun. The chemicalsreact at the surface; the metal is reduced and is deposited on themandrel surface. Chemical reduction processes are preferredbe

40、cause dimensional accuracy is not affected, the film has littleadhesion, and parting is not difficult. If necessary, a silver filmcan be stripped from a nickel electroform with either nitricacid, warm sulfuric acid, or a cyanide solution.5.4.3 Other ways of making non-conducting materials con-ductiv

41、e include: using finely divided metal powders dispersedin binders (“bronzing”), applying finely divided graphite towax, and to natural or synthetic rubbers that have an affinity forgraphite, and applying graphite with a binder.5.4.4 Vapor deposition of silver and other metals is pre-ferred for nonco

42、nducting mandrels used in the semiconductorindustry, the optical disc industry, and the manufacture ofholograms. In these cases the mandrel must be made of amaterial that does not outgas in the vacuum chamber. Glass isthe preferred substrate for making masters and stampers foroptical read-out discs

43、of all kinds.5.5 Preparing Metallic Mandrels:5.5.1 Standard procedures should be used whenever adher-ent electrodeposits are applied to metallic mandrels prior to andNOTE 1Examples of deposit distribution on contours that require special consideration are shown in an exaggerated fashion. The designe

44、r shouldconfer with the electroformer before designing an electroform having any of these contours. An experienced electroformer can minimize some of theexaggeration shown.FIG. 1 Examples of Deposit Distribution on ElectroformsB832 93 (2018)3in preparation for electroforming. See Practices B183, B24

45、2,B254, B281, and B558, for example.5.5.2 With most metallic mandrels an additional chemicaltreatment that forms a parting film on the surface is required toseparate the electroform from the mandrel. After removing alltraces of grease and oil by means of solvents, various metallicmandrels are given

46、different treatments for this purpose (see5.5.3, 5.5.4, 5.5.5, 5.5.6, and 5.5.7).5.5.3 Stainless steel, nickel, and nickel- or chromium-platedsteel are cleaned using standard procedures, rinsed, and passi-vated by immersion in a 2 % solution of sodium dichromate for30 to 60 s at room temperature. Th

47、e mandrel must then berinsed to remove all traces of the dichromate solution.5.5.4 Copper and brass mandrels that have been nickeland/or chromium-plated may be treated as described in 5.5.3.Ifnot electroplated, the surface can be made passive by immer-sion in a solution containing 8 g/L sodium sulfi

48、de.5.5.5 Aluminum alloys may require special treatments evenwhen they are used as expendable mandrels to be separated bychemical dissolution. If the deposits are highly stressed, it maybe necessary to use the zincate or stannate treatments includedin Guide B253 to achieve a degree of adhesion that w

49、ill preventlifting of the deposit from the mandrel. When low-stresseddeposits (near zero) are being produced, treatment of thealuminum by degreasing, cathodic alkaline cleaning, andimmersion in a 50 % solution of nitric acid may be sufficient.5.5.6 Zinc and its alloys may require no other preparationthan conventional cleaning if used for expendable mandrelsand are to be parted by chemical dissolution. In the case ofnickel electroforming, it is necessary to electroplate the zincalloy with copper and treat it accordingly to prevent attack ofthe mandrel. See Practice B252.5.5.7 Th