ASTM B507-86(2003)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: B 507 – 86 (Reapproved 2003)
Standard Practice for
Design of Articles to Be Electroplated on Racks
This standard is issued under the fixed designation B 507; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Relative Throwing Powers of Different Electrolytes
1.1 This practice covers design information for parts to be 4.1 Throwing power is not the same for all metals and all
electroplated on racks. The recommendations contained herein electroplating baths. Table 1 lists the commonly used electro-
are not mandatory, but are intended to give guidance toward plating processes. They are arranged according to decreasing
good practice. throwing power.
1.2 This standard does not purport to address all of the 4.2 A Rochelle-type copper electroplating solution has ex-
safety concerns, if any, associated with its use. It is the cellent throwing power compared to the poor throwing power
responsibility of the user of this standard to establish appro- of a chromic acid solution used to deposit chromium. The
priate safety and health practices and determine the applica- widely used Watts-type nickel bath has fair throwing power.
bility of regulatory limitations prior to use.
5. Geometric Factors Determining Deposit Distribution
2. Significance and Use
5.1 Since a metal deposits preferentially at protuberances,
2.1 When an article is to be electroplated, it is necessary to such as sharp corners, edges, fins, and ribs, these should be
consider not only the characteristics of the electroplating rounded to a radius of at least 0.4 and preferably 0.8 mm to
process, but also the design of the part to minimize electro- avoid excessive buildup. Contouring a base corner in a
plating and finishing costs and solution dragout as well as to depression is also recommended to avoid thickness deficiency
improve appearance and functionality. It is often possible at the location.
during the design and engineering stages to make small 5.2 The width-to-depth ratio of a depression or recess
adjustments in shape that will result in considerable benefit should be held to more than three as shown in Fig. 2.
toward a better quality part at a lower cost. Otherwise, a special auxiliary anode must be employed inside
2.2 The specific property of an electroplating process that the recess to promote more uniform current distribution. An
would require some attention to the details of optional designs, auxiliary anode is usually made of the depositing metal and is
is the throwing power of the electroplating solution. Throwing placed close to the low-current density areas to enhance metal
power is the improvement of the coating distribution over the deposition at those regions.
primary current distribution on an electrode (usually cathode) 5.3 All sharp edges and base angles of a recess should be
in a given solution, under specified conditions. rounded to a radius of 0.25 times or more the depth of the
recess as shown in Fig. 3. When sharp recess angles are
3. Current Distribution and Throwing Power
required for a functional purpose, the electroplater cannot be
3.1 The apparent current during practical electroplating is
expected to meet a minimum thickness at those locations
never uniform over the surface of the product. Even parallel unless it is specifically required.
plates have a nonuniform distribution of current when freely
6. Examples of Distribution of Electrodeposited Nickel
suspended in a bath as shown in Fig. 1. In this example, the
on Various Shapes
current lines tend to concentrate as corners, and edges (high-
current density) of the part. Consequently more metal is 6.1 Fig. 4 through Fig. 5 show the kind of nickel distribu-
deposited at the high-current density areas than at the low- tion that was obtained on several different cathode configura-
current density areas. tions as deposited from a Watts-type bath at normal operating
current densities.The thicknesses illustrated are exaggerated to
emphasize the variations that were obtained. The data are
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.01 on
Ancillary Activities.
Current edition approved Feb. 10, 2003. Published May 2003. Originally Adapted from sketches appearing in Electroplating and Engineering Hand-
approved in 1970. Last previous edition approved in 1998 as B 507 – 86 (1998). book, 4th ed, Durney, L. J., ed., Reinhold Publishing Corporation, NewYork, 1984.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 507 – 86 (2003)
FIG. 1 Current Density Distribution and Typical Electrodeposit (filled area)
TABLE 1 Relative Throwing Powers of Common Electroplating
excessive buildup on protuberances. Fig. 6(a) illustrates a part
Baths
with a sharp angled recess. Nickel distribution is not very
Bath/Metal Ranking
uniform with practically no deposit down in the corners of the
Rochell copper (cyanide based) Excellent
recess.Roundingthecornersoftherecessonthepart,asshown
Cyanide cadmium Excellent
in Fig. 6(b), yields a more uniform nickel thickness in the
Cyanide gold Good
recess. The average-to-minimum thickness ratio in these ex-
Cyanide silver Good
Alkaline tin Goo
...