1、January 2009DEUTSCHE NORM English price group 14No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 25.220.40!$UQ b) the s
2、ignificant surface of the article, indicated, for example, as dimensioned areas on drawings or by the provision of suitably marked samples; c) the nature, condition and finish of the basis metal if they are likely to affect the serviceability and/or the appearance of the coating (see Clause 1); d) t
3、he position on the surface of any unavoidable defects, such as rack marks (see 6.2); e) the finish required, for example bright, dull or another type, preferably accompanied by approved samples of the finish (see 6.2); f) the method of porosity testing to be used and the permitted number and locatio
4、n of acceptable pores (see 6.4); g) the tensile strength of the part and the requirements for any heat treatment prior to, or after, electroplating (see 6.7 and 6.8); h) sampling methods, acceptance levels and any other inspection requirements if different from those specified in ISO 4519 (see Claus
5、e 7); i) the requirements for coating thickness, including positions of measurement as indicated on dimensioned drawings (see 6.3); j) the requirements for adhesion testing (see 6.9). 4.2 Additional information The following additional information may be required and, if so, shall be specified by th
6、e purchaser in writing, for example in the contract or purchase order, or on drawings: a) the composition of the coating and details of intentional alloying elements and undesirable impurities (see 6.6); b) any special cleaning procedures to be used; c) any special requirements for undercoats (see 6
7、.15 and Annex A); d) any requirements for the composition and thickness of each layer in double or multilayer coatings (see Clause 3); e) the electrical properties of the coating and the methods of test to be used (see 6.10); f) the microhardness of the coating and the test method to be used (see 6.
8、11); g) any requirements for solderability and the test method to be used (see 6.12); h) any requirements for wear resistance and the test method to be used (see 6.13); i) the ductility of the coating and the method of test to be used (see 6.14); 7 DIN EN ISO 27874:2009-01 EN ISO 27874:2008 (E) j) a
9、ny requirements for the freedom from surface contamination of the finished articles (see 6.16); k) the agreed mean density of a gold alloy coating if the thickness measurement method requires a density correction (see Annex B); l) any requirements for accelerated-corrosion testing (see 6.5); m) any
10、other requirements, such as a residual-salts test, (see 6.16). 5 Designation 5.1 General The designation shall appear on engineering drawings, in the purchase order, in the contract or in the detailed product specification. The designation specifies, in the following order, the basis metal, the spec
11、ific alloy (optional), stress relief requirements, the type(s) and thickness(s) of undercoats (when present), the thickness and composition of the gold or gold alloy coating or coatings (when double or multilayer coatings are specified), and supplementary treatments such as heat treatment to reduce
12、susceptibility to hydrogen embrittlement. 5.2 Designation specifications The designation shall comprise the following: a) the term, “electrodeposited coating”; b) the number of this International Standard (ISO 27874); c) a hyphen; d) the chemical symbol of the basis metal (see 5.3); e) a solidus (/)
13、; f) if appropriate, the chemical symbol for an undercoat metal followed, if necessary, by a number giving the thickness of the undercoat in micrometres (see 6.15 and Annex A); g) a solidus (/); h) the chemical symbol for gold, Au, or the standard designation for a gold alloy, including the symbol o
14、f the alloying element and a figure in parentheses giving the mean content of that element expressed as a mass fraction in percent to one decimal place; i) a number giving the minimum local thickness requirement for the gold or gold alloy coating in micrometres; j) for double and multilayer gold coa
15、tings, repeat h) and i), followed by a solidus (/), for each subsequent gold or gold alloy coating required. 5.3 Designating the basis material The basis material shall be designated by its chemical symbol or the chemical symbol of its principal constituent if an alloy, for example: Fe for iron and
16、steel; Zn for zinc alloys; 8 DIN EN ISO 27874:2009-01 EN ISO 27874:2008 (E) Cu for copper and copper alloys; Al for aluminium and aluminium alloys. In the case of non-metallic materials, the letters NM shall be used. A specific alloy shall be identified by its standard designation, for example its U
17、NS number or the local, national, equivalent placed between the symbols . For example, Fe is the UNS designation for a particular high-strength steel (see Reference 5 in the Bibliography). 5.4 Designation of heat treatment requirements The heat treatment requirements shall be in brackets and designa
18、ted as follows: a) the letters SR for stress relief heat treatment prior to electroplating, the letters ER for hydrogen embrittlement relief heat treatment after electroplating, and the letters HT for heat treatment for other purposes; b) in parentheses, the minimum temperature, in C; c) the duratio
19、n of the heat treatment in hours, for example SR(210)1 designates stress relief heat treatment at 210 C for 1 h. When heat treatment prior to or after electrodeposition is specified, the requirements shall be included in the designation as shown in the examples (see 5.5). The structure and compositi
20、on of gold and gold alloy coatings may be modified and the coating properties substantially altered by heat treatment. Designers should be aware of these effects before specifying gold coatings on high-tensile-strength basis material. 5.5 Examples A pure gold coating, Au, with a minimum thickness of
21、 5 m on nickel-electroplated steel, Fe/Ni, will have the following designation: Electrodeposited coating ISO 27874 Fe/Ni/Au5 An alloy coating containing 98,0 % gold and 2 % silver, AuAg(2,0), with a minimum thickness of 5 m on a zinc alloy, Zn, with copper and nickel undercoats will have the followi
22、ng designation: Electrodeposited coating ISO 27874 Zn/Cu/Ni/AuAg(2,0)5 An alloy coating containing 99,5 % gold and 0,2 % nickel, AuNi(0,2), with a minimum thickness of 0,5 m deposited over a pure-gold coating, Au, with a minimum thickness of 1 m on a Cu alloy will have the following designation: Ele
23、ctrodeposited coating ISO 27874 Cu/Au1/AuNi(0,2)0,5 A pure-gold coating with a minimum thickness of 5 m, Au5, deposited over a copper undercoat that is 5 m thick, Cu5, on a steel that has an ultimate tensile strength of 1 200 MPa and is heat-treated prior to electroplating for stress relief at 200 C
24、 for 3 h, SR(200)3, and after electroplating to reduce the risk of hydrogen embrittlement at 190 C for 12 h, ER(190)12, will have the following designation: Electrodeposited coating ISO 27874 Fe/SR(200)3/Cu5/Au5ER(190)12 The designation describes the heat treatment and electroplating steps in the or
25、der in which they are performed. The standard designation of the basis material could be placed after the chemical symbol, Fe, in the above example. It is especially important to know the standard designation of a metal or alloy that is difficult to prepare for electroplating and that is susceptible
26、 to hydrogen embrittlement. 9 DIN EN ISO 27874:2009-01 EN ISO 27874:2008 (E) 6 Requirements and test methods 6.1 General Gold and gold alloy coatings normally consist of a single layer of gold metal, usually with a strike undercoat of unspecified thickness, but double or multilayer coatings may be s
27、pecified by the purchaser see 4.2 c). 6.2 Appearance Although this International Standard does not specify the condition, finish or surface roughness of the basis material prior to electroplating, the appearance of electroplated gold and gold alloy coatings depends on the condition of the basis mate
28、rial (see the Bibliography for surface preparation methods). Over the significant surface, the electroplated article shall be free from clearly visible blisters, pits, roughness, cracks and uncoated areas other than those that arise from defects in the basis material. The electroplated article shall
29、 be free from extraneous soil and mechanical damage. On articles where a contact mark is unavoidable, its position and extent shall be specified by the purchaser see 4.1 d). In the case of selectively plated articles, the degree and extent of discoloration at the boundary between the areas that have
30、 been electroplated and those that are not electroplated shall be specified on the product drawing. If required, a preliminary sample with the required standard of finish shall be supplied or approved by the purchaser see 4.1 e). The types of article which are selectively electroplated with gold are
31、 commonly also selectively electroplated with other metals, such as a nickel undercoat or solderable tin alloy coating. Agreements on visual standards will thus extend to all such areas and boundaries. It is therefore essential that such parameters be specified on the product drawing. 6.3 Thickness
32、The thickness of the coating specified in the designation shall be the minimum local thickness. The minimum local thickness of the coating shall be measured within the reference area or at a site specified on the component drawing. The minimum thickness of the gold or gold alloy coating shall be tha
33、t specified by the purchaser. One or more of the methods given in Annex B shall be used to measure the thickness of the gold or gold alloy coating. A profile of the minimum-thickness distribution may alternatively be specified on suitably prepared drawings. Thicknesses of gold and gold alloy coating
34、s commonly specified for electrical, electronic or engineering applications are given in Table 1. Table 1 Examples of commonly specified thicknesses of gold and gold alloy coatings for various applications Application Minimum thickness m Solderability retention, low-reliability electrical contacts 0
35、,1 Medium-reliability electrical connector and switch contacts (electroplated acid gold alloy) 0,25 Semiconductor bonding (pure gold) 0,5 High-reliability consumer electrical contacts 0,75 High-frequency devices and waveguides (pure gold) 1,0 High-reliability electrical contacts for safety-critical
36、applications 2,5 or 5,0 10 DIN EN ISO 27874:2009-01 EN ISO 27874:2008 (E) The thickness values given are approximate only. The thickness which a designer specifies for an application will be the minimum necessary for satisfactory performance in porosity and/or wear tests. 6.4 Porosity When specified
37、 by the purchaser, the parts shall be subjected to one or more of the environmental and porosity tests given in ISO 4524-3, ISO 10308, ISO 12687 or ISO 14647. The method to be used and the acceptable number and location of pores shall be specified by the purchaser. The electrographic tests given in
38、ISO 4524-3:1985, Clauses 2 to 5, can be used for articles with flat surfaces. The tests given in ISO 12687 and ISO 14647 involving gas exposure and the electrographic test given in ISO 4524-3:1985, Clause 6, can be used for articles with curved surfaces. 6.5 Accelerated-corrosion testing Where the c
39、orrosion resistance of the coated articles is important and accelerated-corrosion testing is specified, one of the tests given in ISO 4524-2 shall be used. The acceptable corrosion rating after testing shall be specified by the purchaser in accordance with ISO 10289. The duration and results of acce
40、lerated-corrosion tests may bear little relationship to the service life of the coated article and, therefore, the results obtained are not to be regarded as a direct guide to the corrosion resistance of the tested coatings in all environments where these coatings may be used. Accelerated-corrosion
41、tests are frequently used as part of the qualification testing of electrical subassemblies containing gold or gold alloy electroplated components. Such operational tests typically involve multiple operations of the assembly followed by exposure to a corrosive atmosphere. Qualification depends upon t
42、he satisfactory results of electrical tests, such as contact resistance measurements, conducted before and after the operational tests. Corrosion testing on its own is not to be used as a guide to performance in qualification tests. 6.6 Composition When required, the minimum gold content of the coat
43、ing shall be specified by the purchaser in the designation. Where alloy coatings are required, the gold and alloyed-metal contents shall be specified. The nature and amount of non-metallic inclusions may be specified, especially in the case of electrical and electronic applications. The properties o
44、f the coating may be significantly affected by the presence of non-metallic inclusions. If specified by the purchaser, the gold content of the coating shall be determined by the method given in Annex D. Pure-gold coatings or gold alloy coatings electroplated from sulfite-containing solutions produce
45、 deposits with a tendency to cold welding. They are not recommended for use as finishes for connector or switch contacts. 6.7 Stress relief heat treatment prior to electroplating When specified by the purchaser, steel parts that have an ultimate tensile strength equal to or greater than 1 000 MPa an
46、d that contain tensile stresses caused by machining, grinding, straightening or coil-forming operations shall be given a stress relief heat treatment prior to cleaning and metal deposition. The procedures and classes for stress relief heat treatment shall be as specified by the purchaser or the purc
47、haser shall specify appropriate procedures and classes from ISO 9587 see 4.1 g). Steels with oxide or scale shall be cleaned before application of the coatings. For high-strength steels (strength equal to or greater than 1 000 MPa), non-electrolytic alkaline and anodic alkaline cleaners as well as m
48、echanical cleaning procedures are preferred to avoid the risk of inducing hydrogen embrittlement during cleaning. 11 DIN EN ISO 27874:2009-01 EN ISO 27874:2008 (E) 6.8 Hydrogen embrittlement relief heat treatment after electroplating Steel parts having an ultimate tensile strength equal to or greate
49、r than 1 000 MPa as well as surface-hardened parts shall receive hydrogen embrittlement heat treatment in accordance with the procedures and classes of ISO 9588 or as specified by the purchaser. The effectiveness of the hydrogen embrittlement relief heat treatment may be determined by test methods specified by the purchaser or by test methods described in International Standards (see the Bibliography). The properties of some gold alloy coatings may be changed by heat treatment procedures. It is, however, unlikely that high-strength steels of strength equal to o
