NOTICE: This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International (www.astm.org) for the latest information. Designation: B 488 – 95 AMERICAN SOCIETY FOR TESTING AND MATERIALS 100 Barr Harbor Dr., West Conshohocken, PA 19428 Reprinted from the Annual Book of ASTM Standards. Copyright ASTM Standard Specification for Electrodeposited Coatings of Gold for Engineering Uses1 This standard is issued under the fixed designation B 488; 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. This standard has been approved for use by agencies of the Department of Defense. 1. Scope B 322 Practice for Cleaning Metals Prior to Electroplating3 1.1 Purity—This specification covers requirements for elec- B 343 Practice for Preparation of Nickel for Electroplating trodeposited gold coatings that contain not less than 99.00 with Nickel3 mass % gold and that are used for engineering applications. B 374 Terminology Relating to Electroplating3 1.2 Specifically excluded from this specification are auto- B 481 Practice for Preparation of Titanium and Titanium catalytic, immersion, and vapor deposited gold coatings. Alloys for Electroplating3 1.3 Properties—Gold coatings conforming to this specifi- B 482 Practice for Preparation of Tungsten and Tungsten cation are employed for their corrosion and tarnish resistance Alloys for Electroplating3 (including resistance to fretting corrosion and catalytic poly- B 487 Test Method for Measurement of Metal and Oxide merization), bondability, low and stable contact resistance, Coating Thicknesses by Microscopical Examination of a solderability, and infrared reflectivity. Several types of coat- Cross Section3 ings, differing in gold purity and hardness, are covered by this B 489 Practice for Bend Test for Ductility of Electrodepos- specification. ited and Autocatalytically Deposited Metal Coatings on 1.4 The values stated in SI units are to be regarded as the Metals3 standard. Values provided in parentheses are for information B 499 Test Method for Measurement of Coating Thick- only. nesses by the Magnetic Method: Nonmagnetic Coatings on 1.5 The following hazards caveat pertains only to the test Magnetic Basis Metals3 methods section, Section 9, of this specification: This standard B 504 Test Method for Measurement of Thickness of Me- does not purport to address all of the safety concerns, if any, tallic Coatings by the Coulometric Method3 associated with its use. It is the responsibility of the user of this B 507 Practice for Design of Articles to Be Electroplated on standard to establish appropriate safety and health practices Racks3 and determine the applicability of regulatory limitations prior B 542 Terminology Relating to Electrical Contacts and to use. Their Use4 B 558 Practice for Preparation of Nickel Alloys for Electro- 2. Referenced Documents plating3 2.1 ASTM Standards: B 567 Test Method for Measurement of Coating Thickness B 32 Specification for Solder Metal2 by the Beta Backscatter Method3 B 183 Practice for Preparation of Low-Carbon Steel for B 568 Test Method for Measurement of Coating Thickness Electroplating3 by X-Ray Spectrometry3 B 242 Practice for Preparation of High-Carbon Steel for B 571 Test Methods for Adhesion of Metallic Coatings3 Electroplating3 B 578 Test Method for Microhardness of Electroplated B 253 Guide for Preparation of Aluminum Alloys for Elec- Coatings3 troplating3 B 602 Test Method for Attribute Sampling of Metallic and B 254 Practice for Preparation of and Electroplating on Inorganic Coatings3 Stainless Steel3 B 697 Guide for Selection of Sampling Plans for Inspection B 281 Practice for Preparation of Copper and Copper Base of Electrodeposited Metallic and Inorganic Coatings3 Alloys for Electroplating and Conversion Coatings3 B 735 Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor3 B 741 Test Methods for Porosity in Gold Coatings on Metal 1 This specification is under the jurisdiction of ASTM Committee B-8 on Substrates by Paper Electrography3 Metallic and Inorganic Coatingsand is the direct responsibility of Subcommittee B 748 Test Method for Measurement of Thickness of Me- B08.08on Engineering Coatings. Current edition approved Jan. 15, 1995. Published April 1995. Originally tallic Coatings by Measurement of Cross Section with a published as B 488 – 68. Last previous edition B 488 – 86e1. 2 Annual Book of ASTM Standards, Vol 02.04. 3 4 Annual Book of ASTM Standards, Vol 02.05. Annual Book of ASTM Standards, Vol 03.04. 1 Vol 10..50 0.2.2. or noncon- ducting shields..1 Definitions—For definitions of terms used in this speci. the density of 3. ductility testing (see 9.2 Definitions of Terms Specific to This Standard: 4. Unless otherwise products or tarnish films that interfere with the function or specified.0 5. 700 5.5 2. bases of angles. shall be indicated on the drawings of the parts or by the NOTE 2—When significant surfaces are involved on which the specified provision of suitably marked samples. 2 .2.1 significant surfaces—defined as those normally vis.2.S.5 g/cm3 for Type 2 and Type 3.01. in contrast to a strike or flash.2.25 9 2. Minimum ASTM Type MIL-G-45204 porosity testing (see 9. 4 Section D.1 To make the application of this standard complete. Unless otherwise specified.0 Robbins Ave. thickness of deposit cannot readily be controlled. solderability testing (see Appendix 99. Government Standards: 2 A.0 8 Annual Book of ASTM Standards.1 Purity—Purity shall be specified by ASTM type.1 Types of Coatings—A coating shall be specified by a 5. designation.2 underplating—a metallic coating layer between the deep recesses.4 Significant surfaces shall be specified (see 3.2. such as threads.90 1 III 99.03.2 Hardness—Hardness values shall be indicated by B 762 Method of Variables Sampling of Metallic and Inor. B 488 Scanning Electron Microscope (SEM)3 4.2. involve the use of conforming.75 0.0 1.75 7 Annual Book of ASTM Standards. 1. 4.6).1 type. Examples of commonly specified thicknesses are 3.. and thickness (or mass per 4. 3. Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor4 130–200 HK25 C C B 809 Test Method for Porosity in Metallic Coatings by >200 HK25 D D Humid Sulfur Vapor (Flowers-of-Sulfur)3 NOTE 1—This designation is retained. the ible (directly or by reflection) or essential to the serviceability purchaser may specify the mass of gold per unit area (coating or function of the article. Can be the source of corrosion weight) in milligrams per square centimeter.04. and C 3 C and D MIL STD 105 Sampling Procedures and Tables for Inspec- tion by Attributes9 4. D 1125 Test Methods for Electrical Conductivity and Re. designating Knoop hardness in accordance with specification. auxiliary.).3 a numeral designating thickness in micrometres in unit area) (see Section 4). 4.1 The name. etc.2 code.25 5 Annual Book of ASTM Standards. 5.5 Requirement.7). Vol 15. 5. code. Bldg.2. 3.3 Relationship Between Purity and Hardness—The fol- sistivity of Water6 lowing combinations of purity and hardness ranges are repre- D 3951 Practice for Commercial Packaging7 sentative of good commercial practice: F 390 Test Method for Sheet Resistance of Thin Metallic Type Code Films with a Collinear Four-Probe Array8 1 A only 2.1.09. holes. Attn: NPODS.1).25 1. Knoop Hardness Range ASTM Code MIL-G-45204 posits and Related Metallic Coatings3 90 HK25 maximum A A 91–129 HK25 . The manufacturer should recognize the necessity for either thicker deposits on thickness of an underplating is usually greater than 1 µm (40 the more accessible surfaces or for special racking. Electrodeposited9 numeral that designates the minimum linear thickness in micrometres. because D 509 Test Methods of Sampling and Grading Rosin5 some specifications reference it.2 for thickness tolerances.1.00 3 II TABLE 1 Coating Thickness Class Minimum Thickness.2. bipolar electrodes.1. Classification 5. The significant surfaces Type 1 and 17.5 g/cm3 for fication refer to Terminologies B 374 or B 542. Terminology shown in Table 1. Vol 11.1. B 765 Guide for Selection of Porosity Tests for Electrode. B. characterizing minimum purity in accordance seller in the purchase order or other governing document. 3. ASTM code.2 Instead of specifying the thickness in micrometres.25 0. although rarely used. Special racks may µin.4.1 See 7. 0. 5.3 Presence and thickness of underplating. accordance with 4. if any. 4. and similar areas.1. the purchaser and the basis metal or substrate and the topmost metallic coating.3 g/cm3 for desirable appearance of the article. 4.2.2 U. and 5.3.1.1. the combination of the following: purchaser needs to supply the following information to the 4..3. PA 19111-5094.3 Thickness—Thickness shall be specified by an arabic MIL-G-45204 Gold Plating. B B 799 Test Method for Porosity in Gold and Palladium 90–200 HK25 B (see Note 1) .2).2 Purity and Hardness: (see 3. Type 2 and Type 3. and date of issue of this 4.3 g/cm3 for Type 1 and 17. 4.1.. The 5. if required 4. for performance testing such as Mass Percent Gold. 99. Ordering Information 4. the density of gold is assumed to be 19.1. with 4.50 6 Annual Book of ASTM Standards. which is thinner. Vol 06. Philadelphia.5 Available from Standardization Documents Order Desk.70 2 I X4). military standard designation of type is included for reference. gold is assumed to be 19. 1.2 Classification: type.3. 0. µm 0. The military standard designation of grade is ganic Coatings3 included for reference. 6. 0. none of treatments such as grinding. impurities shall not be present in a quantity greater than 0. despite the reduce this time to a few seconds. A 6.5. However. layer of Type 1 (Code A) gold. B 281.05 mass %.1.5.2.1 Nickel Underplating—For thickness classes less than permit. and roughness may adversely affect when barrel plating.2 Strikes—It is recommended to apply a gold strike to 6.70 mass % gold.4.05 mass % and.1. are employed.7 Whether or not stress relief has been or is to be done NOTE 6—In applications in which forming or flaring operations are to be applied to the plated component. polishing. Individual metallic and B 558). For Type 2 Code A coatings only. The gold content shall be calculated by differ- treatments and mechanical operations on significant surfaces ence. 6. have been completed. Acid greater than 0. abrasive blasting. 6. laps. 6. which may be present in amounts hardness to a value below the specified minimum. may attenuate the signal. hot (50 to 100°C) water rinse. wire marks in the coating shall be agreed upon between the 7. 6. a nickel underplating shall be applied before the gold 7. B 322. B 343. metallic hardening agents such as nickel. porosity. 6.3 If required (see 5.1 and Appendix X6). and similar imperfections as possible.2. such as in wave guides.2 when tested circulation of solution over all surfaces. and cobalt combined shall be less than of the basis metal are essential for satisfactory adhesion and 0. steel parts with a hardness greater 7. All other metals shall be considered pickling of high strength steels shall be avoided.5 Plating Process: nature of the basis metal and good commercial practices 6. be specified.1 Any process that provides an electrodeposit capable of 6.04 6. Practices B 254. Modern.8 Sampling plan employed (see Section 8).3 The basis metal shall be subject to such cleaning 7.1 The coating shall be applied after all basis metal heat mass % each.3 Type 3 (Type II according to MIL-G-45204) coatings than 31 HRC shall be given a suitable stress relief heat shall contain at least 99. Such stress relief shall not reduce the metallic hardening agents.6. prior to applying the gold top coating. Guide 7.1 Nature of Coating—The gold deposit shall meet the procedures as are necessary to ensure a satisfactory surface for appropriate purity requirements as put forth in the following: subsequent electroplating (see Practices B 183.3 Plating—Good practice calls for parts to be electri- meeting the specified requirements is acceptable.03 mass %. Coating Requirements purchaser. cold shuts. Typical thicknesses of the Type 1 gold NOTE 5—In certain instances in which high-frequency analog signals underlayer are 10 to 30 % of the total specified thickness.3. except if the latter is silver or platinum. NOTE 3—A metal finisher can often remove defects through special and iron combined shall be less than 0. The gold content shall clean and continuously conductive. shall contain at least 99.7). care 3 . rinse with dwell times of 40 s in each station when rack plating and 80 s cracks. ous. NOTE 4—When the thickness of the nickel underplate has a detrimental NOTE 8—Where Type 2 (Code B or C) or Type 3 (Code B or C) gold impact on the mechanical properties or bondability of the substrate. B 482.3 unless otherwise Appendix X6). B 481.1. 5.3 Appearance—Gold coatings shall be coherent. continu- producer and the supplier. The surface must be chemically in an amount greater than 0. without inclusions be calculated by difference.5.1.2 Defects in the surface of the basis metal such as Best practice calls for a minimum of three dragout rinses and one running scratches.1 The surface condition of the basis metal should be specified and should meet this specification prior to the plating NOTE 7—For rack and barrel plating processing. burrs. pits. The location of rack or in accordance with 9. that is. improved protection of the underlying metals can be obtained nickel thickness may be reduced to a non-detrimental level as specified by by applying a duplex gold composite coating consisting of an underlying the purchaser. and electropolishing. gouges.90 mass % gold. the is specified.0. or other contaminants.2. shall contain at least 99.1 mass %.2.2 Hardness—The gold coating shall have a Knoop hard- 6. B 488 5. This is particularly useful in automatic observance of the best plating practice. these may not be normal in the treatment steps preceding the plating and a special agreement is indicated. residual plating salts of the parts.1. nicks.00 mass % gold and may contain treatment prior to plating. A minimum rinse time of 2. the magnetic properties of nickel ing (see 6. 7. and have a uniform appearance to the extent that the 6. Iron. inclusions. The gold content shall be calculated by differ- ence. and none of these three elements shall be present performance of these coatings.4 Proper preparatory procedures and thorough cleaning mass %. 5. can be removed from the articles by a clean. significant surfaces shall be brought to the attention of the 7.5 V is suggested. Any such defects on reel-to-reel applications in which dwell times are significantly reduced.4 Racking—Parts should be positioned so as to allow free ness within the specified range as shown in 4. a ductile nickel electrodeposit should (steel parts only).2 Substrate: minimum of 0.1 Type 1 (Type III according to MIL-G-45204) coatings B 253. Manufacture the underplate or substrate.6 If the substrate is one that requires a nickel underplat.1 6. 5. B 242.5 min (rack) or 5 min (barrel) is suggested.1.1. cobalt.2. However. 7. specified. high-velocity impingement-type rinses can the appearance and performance of the deposit.2 Type 2 (Type 1 according to MIL-G-45204) coatings scratches.03 mass %. chemical treat.2.1 The gold coating shall have a thickness on the Nickel underplatings are also applied for other reasons (see significant surfaces in accordance with 4. cally connected when entering the gold plating solution.4 Thickness: coating when the product is made from copper or copper alloy. They must be smooth and as free of 7. nickel. these three elements shall be present in an amount greater than ments. impurities and shall not be present in amounts greater than 0. roll and die marks. if required. the sample. The tolerable amount of porosity in the coating by methods outlined in Test Methods B 487. X-ray fluorescence criteria. and coulometric methods measure the mass of the particular article or coating requiring the porosity test (see gold per unit area that is present over the measured area. When Guide B 697 is specified. When plated parts are used in mating The buyer and seller may agree on the plan or plans to be used.1 Thickness—The beta backscatter. Guide B 697 tolerance specified for the part on its engineering drawing. The inspection lot is then classified as 4 . or to multiply the reading obtained by factor. with tests that are nondestructive and one with those that are destructive. Method B 762 sional tolerances given in the engineering drawing. Test Method B 602. mine quantitatively the metallic impurities present. Method B 762 can be used only for coating requirements that have a numerical limit. B 568. under essentially identical conditions. Initial scanning should be carried out 7. while for calculating plans to meet special needs.2 An inspection lot shall be defined as a collection of at any single point on the significant surface will sometimes have to coated articles that are of the same kind. Since many gold coatings 8. and that are characteristics of the plating process. Determine deposit purity by subtracting shall be free of visible mechanical damage and similar gross total impurities from 100 %. When the sample.3 Appearance—The coating shall be examined at magni- are outside or on the periphery of the significant surfaces (see fications up to 103 for conformance to the requirements of 7. The NOTE 9—The coating thickness requirement of this specification is a test must yield a numerical value and certain statistical requirements must minimum requirement: that is. If they do not. appearance.2). Sampling cal thickness of the gold present. Therefore. The 9. how much greater is largely determined by the shape of the article (see Practice B 507) and the time. lot (see 8. the metallic impurities.5. is 19. sampling inspection. thickness on articles will vary from article to article within a production lot. Such acceptance (or pass-fail) 9. shall be part of the product specification for spectrometry. the coating thickness is required to equal or be met.4.2 The thickness of the gold coating shall be equal to or contain sampling plans that are designed for the sampling inspection of coatings. The procedure is known as of 17. Test Methods thickness requirement. Method B 762 contains several plans and also gives instructions exceed the specified thickness throughout the significant surfaces. and Method B 762 7.2) is examined for compliance with the requirements placed on the articles.2). f. or depends on the severity of the environment that the article is B 748.2 Hardness—Measure hardness in accordance with Test applications this requirement may be relaxed to allow for a Method B 578. the average coating submitted for acceptance or rejection as a group. Test Method B 602 contains four sampling plans. it is necessary to use standards having a density identical to that of the coatings to be NOTE 10—Usually.6. coating thickness from point to point on a coated article is an inherent characteristic of electroplating processes. and B 568 will often give lower reduce the amount of acceptance inspection. B 488 must be taken to ensure that the thickness of the Type 2 or Type 3 gold complying with the requirements based on the results of the inspection of topcoat is sufficient so as not to compromise wear properties. agree on the plan to be used.6. In addition. a density determined by the application of statistics. three for use exceed the specified thickness throughout the significant sur. Properly performed. the inspection measured. B 567. the maximum thickness shall not exceed the not. such as coating thickness. face (see 3. If the pores are uncertainty of less than 10 % on the particular coating being few in number or away from the significant surfaces. that have been coated by exceeds the specified value at all points. instruments utilizing the measuring principles in Test will ensure coated products of satisfactory quality and will Methods B 504.5 Adhesion—The gold coatings shall be adherent to the absorption spectrophotometry (or any methods with demon- substrate when tested by one of the procedures summarized in strated uncertainty less than 10 %) may be used to determine 9. the average coating thickness for the production lot as a whole will be greater than the average necessary to ensure that any 9. B 567.6 for porosity testing). The method chosen shall be such as to give an likely to encounter during service or storage. For some 9.1 Gross Defects/Mechanical Damage—The coatings metallic impurities. The buyer and the seller may conforming to all maximum allowed thicknesses created by part dimen.5 g/cm3 should be employed (see 9. If they do applications. It is provides a large number of plans and also gives guidance in the selection customary that allowance for plated coatings be included of a plan.2.1 The producer is urged to employ statistical process have a density lower than the theoretical density of gold (19. with a collection of coated articles. Variation in the identifies the plan to be used. Atomic 7.1 Deposit Purity—Use any recognized method to deter- single article meets the requirment (see 8. this process g/cm3 ). Therefore. The size of the sample and the criteria of compliance are measuring the total gold thickness of duplex composite coatings. agree on the plan or plans to be used. if all the articles in a production lot are to meet the 9. cross-sectioning and magnetic methods measure the geometri- 8.4). a relatively small number of the articles. the buyer and seller need to within the part tolerance. especially if they 9. Guide B 697.3 control in the coating process. measured area to a geometrical thickness.6. Hence. most average coating a single supplier at one time. presence can often be tolerated. or at approximately the same thicknesses will be greater than the specified value. their measured.4 Thickness and Mass per Unit Area—Measure thickness some porosity. the coating thickness 8.4.1). The sampling plan readings than the microscopical cross-section method.2 Porosity—Almost all as-plated electrodeposits contain 9. that have been exceed the specified value in order to ensure that the thickness equals or produced to the same specifications. Test Method B 602 identifies the plan to be used. 7. defects when viewed at magnifications up to 103. To used for the inspection of the quality of the coated articles shall convert mass of gold per unit area that is present over the be as agreed upon between the purchaser and the supplier. small number of such defects (per unit area).3 f5 d (1) selected at random and is inspected.6 Integrity of the Coating: for all elements in order to detect any unknown or unexpected 7. Keywords 10 Available from the National Institute of Standards and Technology. The 9. B 741. 5 . and protection. and wire wrap connections.3 µm (50 µin. nuclear engineering. high-reliability elec- typical uses of gold coatings are enumerated below. through an angle of 180° on a diameter equal to the thickness 10. unless otherwise specified on the the fracture at a magnification of 103. in mg/cm2 5 19.75 µm or above are used. Government 9. thermocompression. a cross-sectioning calibration standards. and B 568. occur. 10. Government or an agent of tute of Standards and Technology (NIST)10 are certified in units of mass of gold per unit area.1. the shape of the gold-coated part.1. appearance.1. when the above methods are used for measure.2. thermosonic hardening agents in the gold coating will oxidize. 11. is not complete and is intended for general guidance only.1 The following special requirements shall apply when NOTE 11—The calibration standards available from the National Insti- the ultimate purchaser is the U. Code A Gold—For semiconductor compo. 10.5 Adhesion—Determine adhesion by one of the following can also be used as a referee method to confirm the precision procedures (see Test Methods B 571 for full details). Type 1 coatings and 17.3 Packaging—Parts plated for the U. B 799. unless: layers or underplate. allowed to cool. shall be considered to be 19. TYPICAL USES X1. including as subcontracts. Special Government Requirements 10.1. method.S. solderability. The unless otherwise specified. 11. the nature and thickness of any intermediate coatings. pling plans specified in MIL-STD-105 are to be used instead of Mass per unit area ~or coating weight! the ASTM standards specified in 8. and dance with Practice B 489.7 Ductility—When required.6 Plating Integrity—Porosity shall be determined prefer- type of gold coating but also on the gold content and the ably by either Test Method B 735. or B 809 composition and purity of the electroplating solution. but the list trical contacts. General-Purpose Wear Resistant Gold— X1.2 Type 2—For general-purpose. B 488 where: of 103. X1.1 Sampling—For government acceptance.1 Type 1. selecting the appropriate test method. and high-temperature coatings are so varied that it is often not possible to predict the applications. gold electrodeposits.4. or service environment. The coating on nonsignificant separation does not indicate poor adhesion unless the coating surfaces shall be of sufficient thickness to ensure plating can be peeled back with a sharp instrument. Cracking without drawings or in the contract. Government. Gaithersburg. engineering coatings. shall be a minimum of 60 % of that specified parts are heated to 300 to 350°C (570 to 660°F) for 30 min and for significant surfaces.3 g/cm3 for NOTE 12—The test to be selected will depend upon the gold thickness. certified in thickness units that can be converted to mass per unit area units 10. gold platings. shall be packaged in then probe with a sharp point and examine at a magnification accordance with Practice D 3951.S. B 567. Examine at least 1. g/cm3.1. Will not withstand high-temperature applications because the nents.1 The conditions of exposure and the uses of gold and ultrasonic bonding.S.3 Cutting Test—Make a cut with a sharp instrument and and Military. continuity and uniform utility.1. gold coatings.1. MD 20899.3 Type 3.5. unless specifi- apparent at a magnification of 103 after the gold electroplated cally exempted.3 3 thickness ~µm!/10 (2) 10. Some X1.5.).2 Thickness Testing: 10. life of a coating of a given thickness and hardness. ments of thickness.1 In addition to the nondestructive method outlined This conversion should be verified by the supplier of the in Test Methods B 499.1 The density of gold coatings depends not only on the 9.1. 9. No separation of the coating from the substrate shall d 5 density of gold coating. determine ductility in accor- 9. 9.1 Bend Test—Bend the electroplated article repeatedly thicknesses of 0. (2) the density has been measured. See Guide B 765 for guidelines for density figure.4.1. 9.2 The gold thickness on significant surfaces shall be of the article until fracture of the basis metal occurs. the sam- by multiplying by the density of pure gold.1. or peeling shall be thickness of plating on nonsignificant surfaces. B 568 measure the mass of gold per unit area (coating weight) directly and independently of the density of gold.1 gold.2 Heat Test—No flaking.5 grams cm3 for Type 2 and Type 3 the nature of the basis metal.2 Mass Per Unit Area—Test Methods B 504. underplate APPENDIXES (Nonmandatory Information) X1. blistering. such as that specified by Test Method B 487 or B 748. and bias of the particular non-destructive technique when 9.2. B 567. and its intended (1) the density is supplied by the plating process vendor.5. (NIST). engineering gold. Other calibration standards for gold are generally the U. 8 µS/cm. X3. 6 .2 Conductivity of water for extract test shall be 1 µS/cm removed by the rinsing following gold electroplating. are permis- for 2 min to equilibrate the water with the CO2 in the air. In a closed polyethylene bottle.5 µm. fill a X3. When the electroplated coatings are used as electrical conductor paths. of a hard gold because of possible cracking of the gold. or C are used to any thickness up to 5 µm.1. The conductivity tivity of the extract. RESIDUAL SALTS X3. RESISTIVITY X2. Oxidation of co-deposited metals can make sol.0 to 99.1 Electroplated parts are placed in water of known agitate the solution for 10 min before determining the conduc- conductivity and agitated for a specific time. replace the bottle cap..3 Inspection under a source of ultraviolet light is often Method A.. There is evidence to show that when the gold content in the Coatings with purities of 99. the electroplating process can be Point Probe MethodA expected to produce coatings having maximum resistivities as Gold Finishes Ohm per Square A and B 0. X3. method is detailed in Test Method F 390. X2.11 applications. W.8 to 1 µS/cm tivity due to residual salts and other conducting impurities is for at least 1 week. except where they occur on surfaces to which electrical is a component of air.. resulting from blind holes or clean polyethylene bottle half-way with high-purity water from parts that were assembled before electroplating. B. equilibrated water will remain in the range from 0. and Morris. Place the specimen in the bottle in calculated. Jr. “Effect of Au on the Reliability of Fine Pitch Surface Mount Solder Joints. J. uses a procedure in accordance with Test Methods D 1125. It is soluble in water and forms carbonic contact is to be made or on which subsequent soldering acid that ionizes and is at equilibrium at 0. embrittle. X1. presence of salts is evidenced by a characteristic fluorescence and should not be confused with fluorescing dirt or dirt X3. P. It is strongly recommended that gold or cropped should not be electroplated with a heavy thickness coating thicknesses not exceed 0. To prepare equilibrated water.1.1). A suggested four-point thickness. The or less (resistivity 1 MV·cm or more). Selection of the type and thickness of the gold coating is determined by the desired life in the operating environment of the electroplated component. August 25–29.4 Solderability—Type 1 golds are preferred for solder ment occurs leading to potential solder joint failure. pp. Slowly operations are performed. Kramer..” Proceedings from Surface Mount International Conference and Exposition.1. X1. B 488 X1.5 µm for solder applications. C 0. the of the water extract is measured. A.7 % are used with B or C tin-lead solder joint exceeds about 3 % by weight. and shake the bottle vigorously normally obtained in good commercial practice. CO2 sible. J.1 A sample of the coated parts having a total surface particles.4 Water or purging stains. 11 Glazer. the sheet resistance in ohms per square should be specified and not the coating mining resistivity of gold coatings. employed to determine whether electroplating salts have been X3.1 Maximum Electrical Sheet Resistivity by the Four electrical conductor paths.10 A X2.1 When electrodeposited gold coatings are used as TABLE X2.1. area3 of 30 cm2 shall ordinarily be used and extracted in 100 cm of equilibrated water. as (X3.2 Use any reliable four-point probe method for deter.6 Static Separable Connectors—Coatings at any of the listed purities and with hardnesses A.03 specified in Table X2.2.1. hardness and at thicknesses generally not in excess of 2. and the increase in conduc.5 Printed Wiring Boards—Boards that will be sheared dering more difficult. 629–639. A suggested water extract conductivity test method accordance with X3. SOLDERABILITY X4. no individual voids larger in any dimension than the wire diameter shall be acceptable. then immerse at a rate of approximately 10 mm/s to the depth ture of 245 6 5°C. zinc.2 Lower the specimen until its bottom edge contacts least 1 kg of the required solder shall be used. analyses of the depositing any of these gold finishes on copper and copper electroplating bath constituents should be made on a regularly alloy parts that can be subjected to elevated temperatures.4.2 Apparatus-Solder Bath—An electrically heated ther. or lead should be precoated to prevent adhesion problems. the main gold electroplating solution with metallic impurities.1—Caution: Do not store activated carbon in areas in which of sufficient thickness to impact adequate corrosion protection vapors from solvents and other chemicals may contaminate the carbon. X5.1. the With cyanide-sensitive copper alloys.4. they should have a the solution with activated carbon is recommended to control nominal thickness of at least 1. B 322. Allow it to drain and cool X4. and other metals normally require underplatings such as copper or nickel NOTE X5. such as those containing appearance of test coupons may serve as an indication of an beryllium or tellurium.1.3. organic or metallic impurities. X5.3 Materials: in a vertical position. Keep it in the solder for approximately 2 s. X5.2 µm.1 Practices B 183.5 A gold strike is often used to precede the final gold B 343.3.1 Immerse a sample of material as described in X4. chemical polishing. or the application of a self-leveling nickel or copper undercoating before gold elec. or rough spots that are not concentrated Grade WW rosin in accordance with Methods D 509 in 99 % in one area. X5. cadmium (from racking materials. B 481. an acid copper strike is recommended. B 253.3. X5. erties as hardness. Thickness of the the buildup of organic impurities. The temperature the molten solder in the bath.6. can have harmful effects on such prop- X5.2 Copper alloys containing zinc. when control of bath composition can nominal thickness of at least 1. control shall be capable of maintaining the solder at a tempera. withdraw at approximately 10 mm/s.1. the use of these undercoatings requires to prevent contamination of gold electroplating solutions with the approval of the purchaser. X5.1 Solder—The solder shall meet the requirements of electrical connection purposes if 95 % of the cooled solder alloy Grade 60B in Specification B 32 (nominal composition surface is uniform and free of breaks and pinholes. Copper. aluminum. which. solderability.4 To minimize diffusion. B 254. dewetted areas. Any for gold electroplating. than trace quantities.2 Activated Carbon Treatment—Periodic treatment of copper or nickel underplatings are used.1 Substrate Preparation: requirements (see section 6. B 242. and porosity. to the basis metal.8 mm shall be acceptable.2. When the work load is erratic. If X5. if present in the coating in more specified by the purchaser. mostatically controlled solder pot of sufficient size to contain at X4.1 Solution Contamination—Care should be exercised troplating. The scheduled basis. the effect of producing discoloration of the deposit.1. beryllium. allow it to dry for 1 min in a vertical position.3 Gold coatings on zinc. a nickel underplating with a continuous operations.3. each addition thickness of the underplating should be consistent with end-use should be based on bath analyses. approaching need for the activated carbon treatment. B 281. X4. If the basis metal is scratched or rough. B 488 X4. and silver (from impurities in the electroplating bath makeup salts) are some of the more X5. hold in this position for 1 to 2 s. The other 60 tin and 40 lead). Thus. This contamination can have underplating should be consistent with end-use requirements. with immersion times dependent on parts to that was fluxed. steel. and to prevent contamination of the preparation of the applicable basis metal.1 On wire.1). X5. be soldered.1 A surface is considered solderable and acceptable for X4.2.1 in flux to a depth of 25 to 50 mm for 5 to 10 s.3 Control of the Gold Electroplating Bath—Under X5. iron (from insoluble anodes). MANUFACTURE X5.3. On terminals. 7 . and B 482 should be used where appropriate for coating. no X4. Withdraw and X4. etc. X4.2 When electroplated materials are used for electrical X5. bus bars. cleaning alone may not properly prepare the surface tions used for producing these coatings are proprietary. tellurium.2 Underplatings: lead and tin (from solder parts). X4.2.4 Procedure: individual voids larger in any dimension than 0. However. X5. isopropyl alcohol. bath that produces coatings meeting the requirements of the it may be necessary to level the surface by processes such as specification may be used.1 Silver shall not be used as an underplating unless common contaminants.2 µm should be applied before be readily established by scheduled additions. electropolishing.). 5 % of the cooled solder surface may show only pinholes. to improve adhesion.3 Gold Electrolytes—Most gold electroplating solu- contacts.2 Flux—The flux shall be 25 mass % solution of voids.2.2. Appearance.6 For all these purposes. which you may attend. either reapproved or withdrawn. golds and reduce the wear of the precious metal during sliding X6.1 Diffusion Barrier: X6. For some levelling purposes. 100 Barr Harbor Drive. Users of this standard are expressly advised that determination of the validity of any such patent rights. are entirely their own responsibility. and composition of the gold deposit should be determined can be reduced. Your comments will receive careful consideration at a meeting of the responsible technical committee. silver and copper). West Conshohocken. a far significant amounts of acidic pollutants (such as SO2 or HCl). copper edges. not cracked) and must have sufficient X6.1.2 Levelling Layer—To produce a smoother surface than of the contacting surfaces. SOME REASONS FOR USING A NICKEL UNDERPLATE X6. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised. PA 19428. frequency of determination ness. provided the environment does not contain 1. levelling nickel over a rough substrate). hard. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards. and the risk of infringement of such rights. and thickness should be on a regularly scheduled basis. continuously met in production.3 Pore Corrosion Inhibitor—A nickel underplate under thickness to achieve the particular function for which it was the gold top coat will form passive oxides at the base of pores intended. porosity.2 To inhibit interdiffusion between the basis metal and X6. the basis metal in order to ensure a lower porosity gold top plate (for example. Once it has been established determined often enough to ensure compliance with specific that the co-deposited metallic impurity limitations are being requirements. B 488 X5. X6.1 To inhibit diffusion of copper from the basis metal base metals will inhibit creepage of copper tarnish films over (and of zinc from brass) to the surface of the precious metal the gold—where the tarnish originates from pores and bare plating.3. X6.4 Tarnish Creepage Inhibitor for Gold—Non-copper X6.5 Load-Bearing Underlayer for Contacting the gold top coat (for example. The American Society for Testing and Materials takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard.1. greater thickness may be required. which might Surfaces—A hard nickel underplate can serve as a load-bearing produce a weak alloy or intermetallic compound at the inter- foundation for the gold top coat to prevent cracking of hard face. X6. 8 . Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters. As a general rule.2 µm. the nickel underplating must be intact (that is. preferably greater.4 Control of the Gold Deposit—The adhesion. the minimum thickness should be in humid air.