1、Designation: B507 86 (Reapproved 2008)1B507 14Standard Practice forDesign of Articles to Be Electroplated on Racks1This standard is issued under the fixed designation B507; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f 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 NOTEThe units statement in subsection 1.2 was corrected editorially in April 2008.1. Scope1.1 This practice covers design info
3、rmation for parts to be electroplated on racks. The recommendations contained herein arenot mandatory, but are intended to give guidance toward good practice.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This standar
4、d does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Significance and Use2.1 When a
5、n article is to be electroplated, it is necessary to consider not only the characteristics of the electroplating process,but also the design of the part to minimize electroplating and finishing costs and solution dragout as well as to improve appearanceand functionality. It is often possible during
6、the design and engineering stages to make small adjustments in shape that will resultin considerable benefit toward a better quality part at a lower cost.2.2 The specific property of an electroplating process that would require some attention to the details of optional designs, is thethrowing power
7、of the electroplating solution. This term describes the properties of the solution as it relates to the solutionelectrical resistance and solution capacitance at the cathode and overall efficiency of the electrolyte system. Throwing power isdefined as the improvement of the coating distribution over
8、 the primary current distribution on an electrode (usually cathode) ina given solution, under specified conditions.3. Current Distribution and Throwing Power3.1 The apparent current during practical electroplating is never uniform over the surface of the product. Even parallel plateshave a nonunifor
9、m distribution of current when freely suspended in a bath as shown in Fig. 1. In this example, the current linestend to concentrate as corners, and edges (high-current density) of the part. Consequently more metal is deposited at thehigh-current density areas than at the low-current density areas.4.
10、 Relative Throwing Powers of Different Electrolytes4.1 Throwing power is not the same for all metals and all electroplating baths. Table 1 lists the commonly used electroplatingprocesses. They are arranged according to decreasing throwing power.4.2 A Rochelle-type copper electroplating solution has
11、excellent throwing power compared to the poor throwing power of achromic acid solution used to deposit chromium. The widely used Watts-type nickel bath has fair throwing power.5. Geometric Factors Determining Deposit Distribution5.1 Since a metal deposits preferentially at protuberances, such as sha
12、rp corners, edges, fins, and ribs, these should be roundedto a radius of at least 0.4 and preferably 0.8 mm to avoid excessive buildup. Contouring a base corner in a depression is alsorecommended to avoid thickness deficiency at the location.1 This practice is under the jurisdiction ofASTM Committee
13、 B08 on Metallic and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.01 on AncillaryActivities.Current edition approved April 1, 2008May 1, 2014. Published April 2008June 2014. Originally approved in 1970. Last previous edition approved in 20032008 asB507 86 (2003).(2008)1. DO
14、I: 10.1520/B0507-86R08E01.10.1520/B0507-14.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, A
15、STM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.2 T
16、he width-to-depth ratio of a depression or recess should be held to more than three as shown in Fig. 2. Otherwise, a specialFIG. 1 Current Density Distribution and Typical Electrodeposit (filled area)TABLE 1 Relative Throwing Powers of Common ElectroplatingBathsBath/Metal RankingRochell copper (cyan
17、ide based) ExcellentCyanide cadmium ExcellentCyanide gold GoodCyanide silver GoodAlkaline tin GoodCyanide zinc GoodAlkaline non cyanide zinc GoodFluoborate lead GoodAll chloride nickel FairTin nickel FairSulfamate nickel FairWatts nickelA FairBright nickel FairAcid chloride zinc FairNickel-iron Fair
18、Chloride iron FairPyrophosphate copper FairAcid copper FairTrivalent chromium PoorHexavalent chromium PoorA Used for examples illustrated by Figs. 4-5.NOTE 1Ratio should be a minimum of threeFIG. 2 Width-to-Depth Ratio of a RecessB507 142auxiliary anode must be employed inside the recess to promote
19、more uniform current distribution. An auxiliary anode is usuallymade of the depositing metal and is placed close to the low-current density areas to enhance metal deposition at those regions.5.3 All sharp edges and base angles of a recess should be rounded to a radius of 0.25 times or more the depth
20、 of the recess asshown in Fig. 3. When sharp recess angles are required for a functional purpose, the electroplater cannot be expected to meet aminimum thickness at those locations unless it is specifically required.required and optional plating techniques are employed.NOTE 1Electroplating technique
21、s can be used to address uniform deposition in the recess angle.These techniques include bi-polar plating and directedflow electroplating in addition to conforming anodes.6. Examples of Distribution of Electrodeposited Nickel on Various Shapes6.1 Fig. 4 through Fig. 52 show the kind of nickel distri
22、bution that was obtained on several different cathode configurations asdeposited from a Watts-type bath at normal operating current densities. The thicknesses illustrated are exaggerated to emphasizethe variations that were obtained. The data are measurements taken from metallographic cross sections
23、. Reference to the figuresenables similar conclusions to be drawn with most other metals, excluding chromium. The ranges will be smaller for metals abovenickel in Table 1 and larger for metals below nickel.6.2 Improvement in nickel distribution can be gained inside an angle by increasing the angle s
24、ize, as shown in Fig. 4. Twosurfaces meeting at an angle of 60 show an average-to-minimum thickness ratio of 3.3, and increasing the angle to 90 or 120the ratio can be reduced to 2.7 or 1.9, respectively.6.3 Sharp corners should be given as large a radius as practical to improve metal distribution i
25、n a recess and avoid excessivebuildup on protuberances. Fig. 6(a) illustrates a part with a sharp angled recess. Nickel distribution is not very uniform withpractically no deposit down in the corners of the recess. Rounding the corners of the recess on the part, as shown in Fig. 6(b), yieldsa more u
26、niform nickel thickness in the recess. The average-to-minimum thickness ratio in these examples was 9.2 for the part withsharp corners and 5.6 for the part with the rounded corners.6.4 Deep recesses will always have a thinner deposit than the surrounding external areas, as shown in the cross section
27、 of aconcave part in Fig. 7(a). The average-to-minimum nickel thickness ratio for this example was 6.6. A more uniform depositthickness can be obtained on a convex-shaped part, as shown in the example of Fig. 7(b). In this case the average-to-minimumnickel thickness ratio was 2.6.5 Another example o
28、f an elongated curved surface (convex) is illustrated in Fig. 5(a). The nickel deposit was fairly uniformwith an indicated average-to-minimum thickness ratio of 2. However, when this shape is joined to another like a flat plate, metaldistribution is considerably different as illustrated by Fig. 5(b)
29、.7. Racking and Rinsing7.1 Other factors besides metal distribution should also be taken into account when designing a part that will be rackelectroplated. The parts must be attached firmly to the rack, so that all significant surfaces come in contact with the electrolyte.7.2 The parts must be attac
30、hed to a rack firmly enough to prevent falling off during electroplating, and the attachment shouldbe with enough force to provide a continual low-resistance electrical contact. In many cases, parts are rigidly fastened to racksthrough spring clips, prongs or bolts. Little or no metal will deposit a
31、t the points of contact; therefore, it is important to selectnoncritical areas for attaching parts to racks.7.3 Articles attached to racks should be oriented to permit electroplating to be free of roughness on significant surfaces.Roughness comes from insoluble debris suspended in an electroplating
32、bath that becomes incorporated into the depositing metal,2 Adapted from sketches appearing in Electroplating and Engineering Handbook, 4th ed, Durney, L. J., ed., Reinhold Publishing Corporation, New York, 1984.FIG. 3 Rounding Corners to a Radius (r) Related to the Depth of a Recess, r 0.25DB507 143
33、especially on upward facing surfaces. Thus, in many circumstances, it is advisable to have the significant surfaces in a verticalposition, or even be inverted during electroplating.7.4 Orientation of a part on a rack is also important to reduce opportunities for air entrapment in cupped areas.Air po
34、ckets willpreventrevent metal deposition on the exposed surface. Adequate drainage of parts on racks is also desirable to reduce dragout ofthe electrolyte to the rinses. Engineering design can incorporate holes at strategic locations to allow satisfactory runoff of solution.7.5 Racks that are near t
35、he significant surface may interfere with the plating by robbing the surface of current and cause thindeposition. Robbers can be used to remove some of the current to increase the uniformity on the significant surface. Thesetechniques can be used to produce a uniform deposit thickness on complex sha
36、pes.NOTE 1Adapted from sketches appearing in Electroplating and Engineering Handbook, 3rd ed. Reinhold Publishing Corporation, Graham, A. K.,and Pinkerton, H. L., eds., New York, 1971.FIG. 4 Influence of Increasing Angle to Improve Thickness Distribution of Electrodeposited NickelFIG. 5 Nickel Distr
37、ibution on a Convex Surface (a) alone Com-pared to the Same Configuration as Part of a Larger Composite(b)B507 1448. Keywords8.1 cathode; current density; fixture; rack; racking; uniformityFIG. 6 Improving Nickel Thickness Distribution (Average/Minimum Thickness Ratio) by Rounding CornersB507 145FIG
38、. 7 Comparing Nickel Distribution on Concave (a) and Convex (b) SurfacesB507 146ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the val
39、idity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn.Your comm
40、ents are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have
41、not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple c
42、opies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).B507 147
