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1、BRITISH STANDARD BS 1872:1984 Specification for Electroplated coatings of tin UDC 669.058.7:669.65:621.357.7 Licensed Copy: Gilbert Athens, University of Birmingham, 25/10/2008 04:24, Uncontrolled Copy, (c) BSI BS 1872:1984 This British Standard, having been prepared under the direction of the Surfa
2、ce Coatings (other than Paints) Standards Committee, was published under the authority of the Board of BSI and comes into effect on 29 February 1984 BSI 02-1999 First published July 1952 First revision May 1964 Second revision February 1984 The following BSI references relate to the work on this sta
3、ndard: Committee reference SRC/3 Draft for comment 81/50223 DC ISBN 0 580 13664 7 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Surface Coatings (other than Paints) Standards Committee (SRC/-) to Technical Committee SRC/3 upon which th
4、e following bodies were represented: British Metal Finishing Suppliers Association British Telecommunications Electronic Components Industry Federation Electronic Engineering Association Institute of Metal Finishing International Tin Research Institute Metal Finishing Association Ministry of Defence
5、 Telecommunication Engineering and Manufacturing Association (TEMA) Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: Gilbert Athens, University of Birmingham, 25/10/2008 04:24, Uncontrolled Copy, (c) BSI 标准分享网 w w w .b z f x w .c o m 免费下载 BS 1872:1984 BSI 02-1999i Con
6、tents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definitions1 3Information to be supplied by the purchaser to the electroplater1 4Coating classification2 5Sampling2 6Heat treatment of steel2 7Undercoats2 8Coatings2 Appendix A Guidance information4 Appendix B Determination of u
7、ndercoat thickness and coating thickness5 Appendix C Adhesion tests6 Appendix D Sulphur dioxide porosity test6 Figure 1 Cabinet with door8 Figure 2 Hooded cabinet9 Table 1 Service condition and related recommended coating thickness5 Publications referred to Inside back cover Licensed Copy: Gilbert A
8、thens, University of Birmingham, 25/10/2008 04:24, Uncontrolled Copy, (c) BSI BS 1872:1984 ii BSI 02-1999 Foreword This British Standard has been prepared under the direction of the Surface Coatings (other than Paints) Standards Committee. It applies to coatings of tin applied by electroplating to f
9、abricated articles of ferrous and non-ferrous metals to protect them from corrosion and to facilitate soldering. It is a revision of the 1964 edition, which is withdrawn, the main changes from which are: a) inclusion, as an appendix, of guidance notes drawing the attention of the user to factors whi
10、ch should be taken into account when electroplating with tin; b) deletion of the post-electroplating heat treatment recommendations for relief of hydrogen embrittlement because tin is now known to be virtually impervious to hydrogen; c) rationalization of the coating thicknesses recommended for diff
11、erent service conditions. The electroplating processes used are not identified because, if the requirements of the specified tests are met, any of them may be considered suitable. The qualities of suitable chemicals for use in the electroplating of tin are specified in BS 1468. Attention is drawn to
12、 the legislative requirements for tin coatings used in the food industry set out, for example, in Statutory Instrument (1972) No. 1957. Grade T2 of BS 3338 is suitable for this purpose. It is essential, when specifying to BS 1872, that the purchaser should state the classification code and the other
13、 information listed in 3.1 (and, if appropriate, 3.2). Merely to ask for the electroplating to be carried out to BS 1872 without this information is insufficient. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for
14、 their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 10, an inside back cover and a back cover. This Standard has been update
15、d (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: Gilbert Athens, University of Birmingham, 25/10/2008 04:24, Uncontrolled Copy, (c) BSI 标准分享网 w w w .b z f x w .c o m 免费下载 BS 1872:1984 BSI 02-19991
16、 1 Scope This British Standard specifies requirements for electroplated coatings of tin. The coatings may be dull or bright as electroplated, or may be flow-melted by fusion after electroplating. These coatings are intended for use on ferrous and non-ferrous basis metals and also on printed wiring b
17、oards. A classification scheme is included by which the nature of the basis metal and undercoat, if any, and the tin coating thickness can be defined. This standard does not specify any requirements for the condition, finish or surface roughness of the basis material before electroplating (see A.3).
18、 NOTE 1Attention is drawn to BS 9760, which specifies capability approval procedure and rules for printed circuits of assessed quality. The standard is not applicable to electroplating of: a) threaded components (see BS 3382-5); b) tin coated copper wire (see BS 4393); c) sheet, strip (see BS 2920)
19、or wire in the unfabricated form, or of coil springs; d) steels with tensile strengths greater than 1 000 MPa because such steels require hydrogen embrittlement relief after plating (see clause 6). This standard does not apply to coatings applied by other processes, e.g. autocatalytic, immersion or
20、“electroless” processes. NOTE 2The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this standard, the following definitions, together with those given for other terms in BS 5411-1, apply. 2.1 significant surface the part
21、of the article covered or to be covered by the coating and for which the coating is essential for serviceability and/or appearance 2.2 flow-melting a process by which a coating is melted in order to impart desirable properties, such as brightness or improved solderability NOTE 1Less preferred terms
22、applicable to this definition are “fusing”, “flow-brightening” and “reflowing”. NOTE 2See A.6. 3 Information to be supplied by the purchaser to the electroplater 3.1 Essential information. The following information shall be supplied by the purchaser to the electroplater: a) the number of this standa
23、rd, i.e. BS 1872; b) the nature of the basis material; c) the classification code of the coating required (see clause 4); d) the significant surface of the article to be electroplated, indicated, for example, by drawings or by the provision of suitably marked samples; e) which method of adhesion tes
24、ting from Appendix C is to be used (see 8.3); f) the sampling procedure to be adopted (see clause 5); g) the positions where unavoidable contact marks and other defects are acceptable (see 8.1); h) requirements, where they exist, regarding the purity of the coating. 3.2 Additional information. The f
25、ollowing additional information may be required, and if so, shall be specified by the purchaser, if necessary in consultation with the electroplater: a) whether any heat treatment, with the exception of that specified in clause 6 for certain steels, is required before electroplating; b) whether, for
26、 coatings whose minimum thickness is 10 m or greater, the porosity test of Appendix D is to be applied (see 8.4), and if so: 1) the type, number, shape and dimensions of the test specimens to be used and whether cut edges to test specimens are to be protected; 2) the total exposed surface area of th
27、e specimen or specimens to be tested at one time, and the angle of inclination of flat test specimens, if other than that specified in D.4; c) whether solderability testing is required, and if so, the test methods and conditions to be applied (see 8.5); d) undercoats: 1) for a basis material of copp
28、er alloy, containing zinc as an alloying constituent, and where solderable properties are required, which method is to be used to determine the required undercoat thickness; 2) whether an undercoat (or undercoats) is required for basis materials other than described in item d) 1) above, and if so: i
29、) its nature and minimum local thickness (see A.3 and A.4); Licensed Copy: Gilbert Athens, University of Birmingham, 25/10/2008 04:24, Uncontrolled Copy, (c) BSI BS 1872:1984 2 BSI 02-1999 ii) which method is to be used to determine the required undercoat thickness; e) which method is to be used to
30、determine the required coating thickness (see 8.2); f) whether any special pretreatment is required. If necessary, the purchaser shall supply a sample showing the required finish. 4 Coating classification Coatings shall be classified by a code consisting of five parts, each of which shall be separat
31、ed by an oblique stroke, as follows: a/b/c/d/e where Example. Fe/Ni/Sn/5/f represents a ferrous basis metal with a nickel undercoat, tin electroplated to a coating thickness of 5 m and flow-melted. 5 Sampling The method of sampling shall be selected from the procedures given in either BS 6001 or BS
32、6041. NOTEThe acceptance levels should be agreed between the purchaser and supplier. 6 Heat treatment of steel Severely cold-worked steel parts shall be stress-relieved before electroplating by either: a) heating for 1 h at a temperature of 190 C to 230 C; or b) where treatment as in item a) would i
33、mpair some steels which have been carburized, flame-hardened or induction-hardened and subsequently ground, heating at a lower temperature, e.g. at 170 C for not less than 1 h. NOTEHydrogen embrittlement relief after electroplating. Because diffusion of hydrogen through tin coating is very slow, hea
34、t treatment for hydrogen embrittlement relief after electroplating is impractical. 7 Undercoats 7.1 General. If the basis material is a copper alloy containing zinc as an alloying constituent, and solderable properties are required, a nickel or copper undercoat of minimum local thickness 2.5 m shall
35、 be applied. In other cases where an undercoat is specified, its nature and minimum local thickness shall be specified by the purchaser (see A.3, A.4 and A.5.2). 7.2 Thickness. The thickness of any undercoat (or undercoats) shall be determined by either: a) one of the methods given in Appendix B, as
36、 specified by the purchaser; or b) any other method that the purchaser specifies, provided that it can be demonstrated to have an accuracy of 10 % or better of the true local thickness, or is as good as or better than the methods given in Appendix B for the particular application. The method specifi
37、ed shall be the one that is expected to yield the most reliable results considering such factors as shape of component, size of component, undercoat material, basis material, etc. In the case of dispute, the microscopical method referred to in B.1.1 shall be used. 8 Coatings 8.1 Appearance. When exa
38、mined by normal or corrected vision without other aid, the significant surface(s) of the electroplated article shall be clean, free from visible defects such as blisters, pits, roughness, nodules, cracks or unplated areas and shall not be stained or discoloured. Where fused, the surface shall be fre
39、e from de-wetted areas. The acceptability of defects on non-significant surfaces and the position of unavoidable contact marks shall be specified by the purchaser. If necessary, a sample showing the required finish shall be supplied or approved by the purchaser. 8.2 Thickness. The minimum thickness
40、of the tin coating shall be specified in the coating classification code (see 3.1 c), clause 4, and A.8) from within the range 5 m to 30 m and the preferred thickness values shall be 5 m, 10 m, 20 m and 30 m. a indicates the chemical symbol for the basis metal (or for the main constituent if an allo
41、y); b indicates the undercoat, by the symbol “Ni” or “Cu” in the case of nickel or copper, or by the symbol “u” where other undercoat materials or systems are required see 3.2 d), or by the symbol “z” where an undercoat is not required; c indicates the chemical symbol “Sn” for tin; d indicates the m
42、inimum coating thickness, in m; e indicates the surface finish, by the symbol “m” if the coating is matt, or “b” if it is bright electroplated, or “f” if it is flow-melted. Licensed Copy: Gilbert Athens, University of Birmingham, 25/10/2008 04:24, Uncontrolled Copy, (c) BSI 标准分享网 w w w .b z f x w .c
43、 o m 免费下载 BS 1872:1984 BSI 02-19993 The thickness of the coating shall be measured over a reference area (see BS 5411-1) on any part of the significant surface that can be touched with a 20 mm diameter ball. In the case of articles having a significant surface area of 100 mm2 or greater, the minimum
44、 thickness shall be regarded as the minimum value of local thickness. In the case of articles having a significant surface area of less than 100 mm2, the minimum thickness shall be regarded as the minimum value of average thickness (see A.5.2). In the case of printed wiring boards with electroplated
45、-through holes, the measurements shall also be carried out on the surfaces within the holes, and not only the areas that can be touched with a 20 mm diameter ball. In the case of flow-melted coatings, the measurements shall be carried out on the as-electroplated condition, prior to flow-melting (see
46、 A.6). The thickness of the coating shall be determined by either: a) one of the methods given in Appendix B, as specified by the purchaser; or b) any other method the purchaser specifies, provided that it can be demonstrated to have an accuracy of 10 % or better of the true thickness, or is as good
47、 as or better than the methods given in Appendix B for the particular application. The method specified shall be one that is expected to yield the most reliable results considering such factors as coating thickness, shape of component, size of component, coating material, basis material, etc. In the
48、 case of dispute, the microscopical method referred to in B.1.1 shall be used. 8.3 Adhesion. Coatings shall be subjected to one of the adhesion tests described in Appendix C, when there shall be no evidence of poor coating adhesion. 8.4 Porosity. If specified by the purchaser, coatings having a mini
49、mum thickness of 10 m or greater shall be subjected to a porosity test as follows: a) for ferrous basis material, the test given in BS 5466-1; b) for non-ferrous basis material, the test given in Appendix D. In either case, there shall be no evidence of corrosion of the substrate when viewed with a magnification of 3 (see A.2.1). 8.5 Solderability 8.5.1 General materials and piece parts. If specified by the purchaser, solderability testing on general materials and piece parts shall be carried out in accordance with method 1 of test Ta of BS 2011-2.1T:1981,