1、Designation: B 832 93 (Reapproved 2008)Standard Guide forElectroforming with Nickel and Copper1This standard is issued under the fixed designation B 832; 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.1. Scope1.1 This guide covers electroforming practice and describesthe processing of mandrels, the design of electroformed ar-ticles, and the use o
3、f copper and nickel electroplating solutionsfor 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 and health practices and determine the applic
4、a-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B 183 Practice for Preparation of Low-Carbon Steel forElectroplatingB 242 Guide for Preparation of High-Carbon Steel forElectroplatingB 252 Guide for Preparation of Zinc Alloy Die Castings forElectroplating an
5、d Conversion CoatingsB 253 Guide for Preparation of Aluminum Alloys for Elec-troplatingB 254 Practice for Preparation of and Electroplating onStainless SteelB 281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Conversion CoatingsB311 Test Method for Density Determina
6、tion for PowderMetallurgy (P/M) Materials Containing Less Than TwoPercent PorosityB 343 Practice for Preparation of Nickel for Electroplatingwith NickelB 374 Terminology Relating to ElectroplatingB 489 Practice for Bend Test for Ductility of Electrodepos-ited and Autocatalytically Deposited Metal Co
7、atings onMetalsB 490 Practice for Micrometer Bend Test for Ductility ofElectrodepositsB 558 Practice for Preparation of Nickel Alloys for Electro-platingB 571 Practice for Qualitative Adhesion Testing of MetallicCoatingsB 578 Test Method for Microhardness of ElectroplatedCoatingsB 636 Test Method fo
8、r Measurement of Internal Stress ofPlated Metallic Coatings with the Spiral ContractometerB 659 Guide for Measuring Thickness of Metallic andInorganic CoatingsB 849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen EmbrittlementE8 Test Methods for Tension Testing of Meta
9、llic MaterialsE 384 Test Method for Microindentation Hardness of Ma-terials3. Summary of Electroforming Practice3.1 Electroforming is defined (see Terminology B 374)asthe production or reproduction of articles by electrodepositionupon a mandrel or mold that is subsequently separated from thedeposit.
10、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 metal-cove
11、red 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 and Use
12、4.1 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 responsi
13、bility of Subcommittee B08.08.01 onEngineering Coatings.Current edition approved Aug. 1, 2008. Published September 2008. Originallyapproved in 1993. Last previous edition approved in 2003 as B 832 93 (2003).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer
14、 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, United States.traditional methods of fabrication. Cur
15、rent 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-discs, and audio compact discs; mesh produ
16、cts 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 electrodeposition onto rotating drums. Copp
17、er 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 the difficulty and costof producing the
18、 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 detail and complexcombinations of surfa
19、ce 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 permanent,semipermanent, or expendable (Table
20、 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 parting film to facilitate separation of
21、the 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 shapes or angles areinvolved, it is possi
22、ble 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 materials that arecollapsible, such as pol
23、yvinyl 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 selecting a suitable material: permanent m
24、andrels 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 baths. Wax and most plastics expand whe
25、nexposed 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 operation can often be simplifiedby desig
26、n 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 (convex) angles should be provided wit
27、h 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 the angle.5.2.3 Whenever possible, per
28、manent 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 beeffected by heating or cooling).5.2.4 A f
29、ine 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, fins, v-shaped projections, v-bottom
30、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 auxiliary equipment or fixture for sep
31、arat-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 the end ofthis standard.TABLE 1 Types of
32、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-plated aluminumNonconductorsExpendable Wax
33、GlassPermanent (or Semi-Permanent) Rigid and collapsible plastic; forexample, epoxy resins and polyvinylchlorideWoodB 832 93 (2008)2should provide reference points for and mechanical means ofholding if finish machining is necessary before removal of themandrel.5.3 Mandrel Fabrication:5.3.1 The metho
34、d 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 conventional pattern-making processes.5.4 Prep
35、aring 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 synthetic resinformulation. It is often pref
36、erable 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 spraying the reagent containing the metal io
37、ns 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 preferredbecause dimensional accuracy is not affe
38、cted, 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-ductive include: using finely divided metal
39、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 nonconducting mandrels used in the semicond
40、uctorindustry, 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 of all kinds.5.5 Preparing Metallic Ma
41、ndrels:5.5.1 Standard procedures should be used whenever adher-ent electrodeposits are applied to metallic mandrels prior to andin preparation for electroforming. See Practices B 183, B 242,B 254, B 281, and B 558, for example.NOTEExamples of deposit distribution on contours that require special con
42、sideration are shown in an exaggerated fashion. The designer should conferwith 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 ElectroformsB 832 93 (2008
43、)35.5.2 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 different treatments for this purp
44、ose (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. The mandrel must then berinsed to re
45、move 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 sulfide.5.5.5 Aluminum alloys may requi
46、re 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 B 253 to achieve a degree of adhesion that willprevent lifting of the deposit
47、 from the mandrel. When low-stressed deposits (near zero) are being produced, treatment ofthe aluminum 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 u
48、sed 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 B 252.5.5.7 The low-melting point alloys included in Table 1e
49、mployed to make expendable mandrels that can be meltedaway have a tendency to leave a residue of tin on the surfaceof the electroform. The mandrel can be plated with copper priorto electroforming to prevent this.6. Nickel and Copper Electroforming Solutions6.1 The choice of metal selected for the electroform willdepend on the mechanical and physical properties required inthe finished article as related to function. The two metalsselected most frequently are nickel and copper. The operationand control of nickel and copper electroforming solutions aredescribed in this section.6.2
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