1、Designation: B 832 93 (Reapproved 2003)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 (e) 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
3、of 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 appli
4、ca-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:B 183 Practice for Preparation of Low-Carbon Steel forElectroplating2B 242 Practice for Preparation of High-Carbon Steel forElectroplating2B 252 Practice for Preparation of Zinc Alloy Die Castingsfor Electropl
5、ating and Conversion Coatings2B 253 Guide for Preparation of Aluminum Alloys for Elec-troplating2B 254 Practice for Preparation of and Electroplating onStainless Steel2B 281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Conversion Coatings2B 311 Test Method for Dens
6、ity Determination for PowderMetallurgy (P/M) Materials Containing Less Than TwoPercent Porosity2B 343 Practice for Preparation of Nickel for Electroplatingwith Nickel2B 374 Terminology Relating to Electroplating2B 489 Practice for Bend Test for Ductility of Electrodepos-ited and Autocatalytically De
7、posited Metal Coatings onMetals2B 490 Practice for Micrometer Bend Test for Ductility ofElectrodeposits2B 558 Practice for Preparation of Nickel Alloys for Electro-plating2B 571 Practice for Qualitative Adhesion Testing of MetallicCoatings2B 578 Test Method for Microhardness of ElectroplatedCoatings
8、2B 636 Test Method for Measurement of Internal Stress ofPlated Metallic Coatings with the Spiral Contractometer2B 659 Guide for Measuring Thickness of Metallic andInorganic Coatings2B 849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen Embrittlement2E 8 Test Methods of
9、 Tension Testing of Metallic Materials3E 384 Test Method for Microhardness of Materials33. 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 fr
10、om thedeposit.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,
11、the metal-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. Signif
12、icance 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 bytraditional methods of fabrication. Current applications ofnickel electroforming include: textile printing
13、 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 products for making1This guide is under the jurisdiction of ASTM Committ
14、ee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.08.01onEngineering Coatings.Current edition approved Feb. 10, 2003. Published May 2003. Originallyapproved in 1993. Last previous edition approved in 1998 as B 832 93 (1998).2Annual Book of ASTM Standards,
15、Vol 02.05.3Annual Book of ASTM Standards, Vol 03.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.porous battery electrodes, filters, and razor screens; and opticalparts, bellows, and radar wave guides (1-3).44.2 Copper is extensiv
16、ely used for electroforming thin foilfor the printed circuit industry. Copper foil is formed continu-ously by electrodeposition onto rotating drums. Copper is oftenused as a backing material for electroformed nickel shells andin other applications where its high thermal and electricalconductivities
17、are required. Other metals including gold areelectroformed on a smaller scale.4.3 Electroforming is used whenever the difficulty and costof producing the object by mechanical means is unusuallyhigh; unusual mechanical and physical properties are requiredin the finished piece; extremely close dimensi
18、onal tolerancesmust be held on internal dimensions and on surfaces ofirregular contour; very fine reproduction of 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 Consideration
19、s: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 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
20、usually pure metals or alloys ofmetals and are prepared by standard procedures but mayrequire an additional thin parting 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 m
21、andrelshould be used is largely dependent on the particular articlethat is to be electroformed. If no reentrant shapes 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
22、involved, it isnecessary to use mandrel materials that can be removed bymelting or by chemical dissolution, or materials 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
23、 materials can be used to fabricate man-drels for electroforming, but the following generalizations mayhelp in selecting 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
24、 mandrel cannot be withdrawn; and it isimportant that the mandrel retain its dimensional stability inwarm plating 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, an
25、d other electroplating solutions that func-tion at room temperature.5.2 Mandrel Design:5.2.1 The electroforming operation 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.
26、 Examples of mandrelshapes that may present problems during electroforming areillustrated in Fig. 1.5.2.2 Exterior (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 mand
27、rel 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, 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, t
28、hemandrel 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 fine surface finish on the mandrel, achieved bylapping or by electropolishing, will generally facilitate separa-tion of mandrel and electroform. A f
29、inish 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 grooves, deepscoops, slots, concave recesses, and rings and ribs can causeproblems with metal distribution during electroforming unlessinside and o
30、utside angles and corners are rounded.5.2.6 An engineering drawing of the mandrel, the electro-formed article, and 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 no
31、nfunctional areas of the electroform. Itshould 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 method of fabrication of the mandrel will dependon the type selected, the material chosen, and th
32、e object to be4The boldface numbers in parentheses refer to the list of references at the 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 Nick
33、elAustenitic StainlessInvar, KovarCopper and brassNickel-plated steelNickel/chromium-plated aluminumNonconductorsExpendable WaxGlassPermanent (or Semi-Permanent) Rigid and collapsible plastic; forexample, epoxy resins and polyvinylchlorideWoodB 832 93 (2003)2electroformed. Mandrels may be manufactur
34、ed by casting,machining, electroforming, and other techniques. Permanentmandrels can be made by any of the conventional 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-duc
35、tive. Porous materials, for example, leather and plastic, maybe impregnated with wax, shellac, lacquer, or a synthetic 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 chemi
36、cally reduced film of silver, copper, ornickel to the surface. In general, these processes are carried outby spraying 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
37、 surface; the metal is reduced and is deposited on themandrel surface. Chemical reduction processes are preferredbecause 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 n
38、itricacid, warm sulfuric acid, or a cyanide solution.5.4.3 Other ways of making non-conducting materials con-ductive include: using finely divided metal powders dispersedin binders (“bronzing”), applying finely divided graphite towax, and to natural or synthetic rubbers that have an affinity forgrap
39、hite, 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 semiconductorindustry, the optical disc industry, and the manufacture ofholograms. In these cases the mandrel must be made of amaterial that does not outga
40、s in the vacuum chamber. Glass isthe preferred substrate for making masters and stampers foroptical read-out discs 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 andin preparation for
41、electroforming. See Practices B 183, B 242,B 254, B 281, and B 558, 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 s
42、olvents, various metallicmandrels are given different treatments for this purpose (see5.5.3, 5.5.4, 5.5.5, 5.5.6, and 5.5.7).NOTEExamples of deposit distribution on contours that require special consideration are shown in an exaggerated fashion. The designer should conferwith the electroformer befor
43、e 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 (2003)35.5.3 Stainless steel, nickel, and nickel- or chromium-platedsteel are cleaned using standard proced
44、ures, 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 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
45、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 require special treatments evenwhen they are used as expendable mandrels to be separated bychemical dissolution. If the deposits are highly stressed, i
46、t 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 from the mandrel. When low-stressed deposits (near zero) are being produced, treatment ofthe aluminum by degreasing, cathodic alkaline cleaning,
47、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
48、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 1employed to make expendable mandrels that can be meltedaway have a tendency to leave a residue of tin on the surfaceof the electroform. The mandrel
49、 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 The nickel electroplating solutions commonly used forelectroforming are Watts and nickel sulfamate with and with-out addition agents. The advantages
