1、BRITISH STANDARD BS 6137:1982 Specification for Electroplated coatings of tin/lead alloys UDC 669.058.7:669.654:621.357.7BS6137:1982 This British Standard, having been prepared under the directionof the Surface Coatings(other than Paints) Standards Committee, was published under the authority ofthe
2、Board of BSI and comes intoeffect on 26February1982 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference SRC/3 Draft for comment 80/51106DC ISBN 0 580 12209 3 Cooperating organizations The Surface Coatings (other than Paints) Standards Committee, under wh
3、ose direction this British Standard was prepared, consists of representatives from the following: Aluminium Federation Assay Offices Committee of Great Britain Association of Metal Sprayers British Jewellers Association British Jewellery and Giftware Federation Ltd. British Metal Finishing Suppliers
4、 Association* British Steel Industry Chemical Industries Association Electricity Supply Industry in England and Wales Engineering Equipment Users Association Galvanizers Association Greater London Council Institute of Metal Finishing* Institute of Sheet Metal Engineering Institute of Vitreous Enamel
5、lers Institution of Corrosion Science and Technology Metal Finishing Association* Ministry of Defence* Motor Cycle Association of Great Britain Society of Motor Manufacturers and Traders Limited Vitreous Enamel Development Council Zinc Development Association The organizations marked with an asteris
6、k in the above list, together with the following, were directly represented on the Technical Committee entrusted with the preparation of this British Standard: Electronic Components Industry Federation Electronic Engineering Association International Tin Research Institute Telecommunication Engineer
7、ing and Manufacturing Association (TEMA) Post Office Individual expert Individual manufacturer Amendments issued since publication Amd. No. Date of issue CommentsBS6137:1982 BSI 11-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii 1 Scope 1 2 References 1 3 Definitions 1
8、4 Information to be supplied by the purchaser to the electroplater 1 5 Coating classification 2 6 Sampling 2 7 Heat treatment of steel 2 8 Undercoats 2 9 Coatings 3 Appendix A Guidance information 4 Appendix B Determination of tin content of the coating 5 Appendix C Determination of undercoat thickn
9、ess and coating thickness 7 Appendix D Sulphur dioxide porosity test 7 Appendix E Adhesion tests 10 Figure 1 Cabinet with door 8 Figure 2 Hooded cabinet 9 Table 1 Service condition and related recommended coating thickness 5 Publications referred to Inside back coverBS6137:1982 ii BSI 11-1999 Forewo
10、rd This British Standard has been prepared under the direction of the Surface Coatings (other than Paints) Standards Committee in order to extend the range of standardized electroplated coatings of tin and its alloys. Electroplated coatings of tin/lead alloys are already being used extensively in th
11、e telecommunications industry and standardization at this time is accordingly desirable in order to avoid variety proliferation. The use of such finishes has resulted in high integrity and high reliability of soldered electrical circuits. Tin/lead alloy coatings are also known to be resistant to whi
12、sker growth. It is essential that the purchaser should state the coating classification code together with the other information listed in4.1 (and, if appropriate, 4.2). Merely to ask for the electroplating to be carried out in accordance with BS6137 without this information is insufficient. NOTEAlt
13、hough this standard applies specifically to the composition range55% to70% by mass of tin, it may be used as a basis for standardizing electroplated coatings of tin/lead alloys of other compositions, but it should be borne in mind that the properties of such coatings may not necessarily be those of
14、the alloy range covered by this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations.
15、 Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside
16、front cover.BS6137:1982 BSI 11-1999 1 1 Scope This British Standard specifies requirements for electroplated coatings of tin/lead alloys with a nominal composition of60% of tin and actual tin content in the range55% to70% by mass of tin. These coatings are intended for use on ferrous and non-ferrous
17、 basis metals and also on printed circuit boards. A classification scheme is included by which the nature of the basis metal and the coating composition can be defined and which also contains provision for flow-melting and bright deposited coatings. This standard specifies no requirements for the co
18、ndition, finish or surface roughness of the basis material before electroplating (seeA.3.1). NOTEAttention is drawn to BS9760, which specifies capability approval procedure and rules for printed circuits of assessed quality. This standard does not apply to: a) threaded components (see BS3382-5); b)
19、tin/lead coated copper wire (see BS4393); c) bearing overlays; d) terne plate; e) electroplating of steels with tensile strengths greater than1000MPa (see note toclause7). 2 References The titles of the standards publications referred to in this standard are listed on the inside back cover. 3 Defini
20、tions For the purposes of this standard, the following definitions, together with those given for other terms in BS5411-1, apply. 3.1 significant surface the part of the article covered or to be covered by the coating and for which the coating is essential for serviceability and/or appearance 3.2 fl
21、ow-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 applicable to this definition are “fusing”, “flow-brightening”, and “reflowing”. NOTE 2SeeA.6. 4 Information to be supplied by the purchas
22、er to the electroplater 4.1 Compulsory information. The following information shall be supplied by the purchaser to the electroplater: a) the number of this standard, i.e.BS6137; b) the nature of the basis material; c) the classification code of the coating (seeclause5) and the tolerance on the requ
23、ired tin content, in%, together with any special requirements for the composition of the alloy; 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 testing from Appendix E is to
24、 be used (see9.4); f) the sampling procedure to be adopted (seeclause6); g) the positions where unavoidable contact marks and other defects are acceptable (see9.1). 4.2 Additional information. The following additional information may be required, and if so, shall be specified by the purchaser, if ne
25、cessary in consultation with the electroplater: a) whether any heat treatment, with the exception of that specified inclause7 for certain steels, is required before electroplating; b) whether, for coatings whose minimum thickness is104m or greater, the porosity test ofAppendix D is to be applied (se
26、e9.5), and if so: 1) the type, number, shape and dimensions of the test pieces to be used and whether cut edges of test specimens are to be protected; 2) the total exposed surface area of the specimen or specimens to be tested at one time, and the angle of inclination of flat test specimens, if othe
27、r than that specified inD.4; 3) the criteria for the evaluation of the result of the test, including any cleaning procedure involved; c) whether solderability testing is required, and if so, the test methods and conditions to be applied (see9.6);BS6137:1982 2 BSI 11-1999 d) undercoats: 1) for a basi
28、s material of copper 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 (see8.1); 2) whether an undercoat (or undercoats) is required for applications or basis materials other than th
29、at described in item1), and if so: i) its nature and minimum local thickness (seeA.3); ii) which method is to be used to determine the required undercoat thickness; e) which method is to be used to determine the required coating thickness (see9.2); f) whether any special pretreatment is required. If
30、 necessary, the purchaser shall supply a sample showing the required finish. 5 Coating classification Coatings shall be classified by a code consisting of five parts, each of which shall be separated by an oblique stroke, as follows: a/b/c/d/e where Example. Fe/Ni/Sn60-Pb/10/f represents an iron or
31、steel basis metal, a nickel undercoat, tin/lead electroplated with a tin content of60% by mass having a coating thickness of104m, and flow-melted. NOTESee9.2 andA.7 for recommended coating thicknesses. 6 Sampling The method of sampling shall be selected from the procedures given in either BS6001 or
32、BS6041. NOTEThe acceptance levels should be agreed between the purchaser and supplier. 7 Heat treatment of steel Severly cold-worked steel parts shall be stress-relieved before electroplating by either: a) heating for1h at a temperature of190 C to230 C; or b) where such treatment in itema) would imp
33、airsome steels that have been carburized, flame-hardened or induction-hardened, and subsequently ground, heating at a lower temperature, e.g.at170 C for not less than1h. NOTEHydrogen embrittlement relief of steel after electroplating. Steels with tensile strengths greater than1000MPa require hydroge
34、n embrittlement relief. Because diffusion of hydrogen through tin/lead alloy coatings is very slow, and also because the coatings would melt at the temperatures required, heat treatment for hydrogen embrittlement relief of steel after electroplating is impractical. 8 Undercoats 8.1 General. If the b
35、asis material is a copper alloy containing zinc as an alloying constituent, and solderable properties are required, a nickel or copper undercoat of minimum local thickness2.54m shall be applied. In other cases where an undercoat is specified, its nature and minimum local thickness shall be specified
36、 by the purchaser (seeA.4). 8.2 Thickness. The thickness of any undercoat (orundercoats) shall be determined by either: a) one of the methods given inAppendix C, as specified by the purchaser; or b) any other method the purchaser specifies, provided that it can be demonstrated to have an accuracy of
37、10% or better of the true local thickness or is as good as or better than the methods given inAppendix C for the particular application. The method specified shall be one that is expected to yield the most reliable results considering such factors as shape of component, size of component, undercoat
38、material, basis material, etc. In the case of dispute, the method referred to inC.1.1 shall be used. a indicates the chemical symbol for the basis metal (or for the main constituent if an alloy); b indicates the undercoat, by the symbol “Ni” or “Cu” in the case of nickel and copper, or by the symbol
39、 “u” where other undercoat materials or systems are required see4.2 d), or by the symbol “z” where an undercoat is not required; c indicates the composition of the coating by means of the symbol “Sn”, followed by the percentage by mass of tin in the coating, followed by a hyphen and the symbol “Pb”;
40、 d indicates the minimum coating thickness, in4m; 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.BS6137:1982 BSI 11-1999 3 9 Coatings 9.1 Appearance. When examined by the unaided eye, the significant surface
41、(s) of the electroplated article shall be free from visible defects such as blisters, pits, roughness, cracks or unplated areas and shall not be stained or discoloured. The acceptability of defects on non-significant surfaces and the position of unavoidable contact marks shall be specified by the pu
42、rchaser. The finished article shall be clean and free from damage. The surface shall be of a smooth texture, free from nodules and, where fused, shall be free from de-wetted areas. The occurrence of a cellular pattern on the surface shall not be considered to be detrimental. If necessary, a sample s
43、howing the required finish shall be supplied or approved by the purchaser. 9.2 Thickness. The minimum thickness of the tin/lead coating shall be specified in the coating classification code see4.1 c), clause5 andA.7 from within the range24m to304m, and the preferred thickness values shall be54m, 104
44、m, 204m and304m The thickness of the coating shall be measured over a reference area (see BS5411-1) on any part of the significant surface that can be touched with a20mm diameter ball. In the case of articles having a significant surface area of100mm 2or greater, theminimum thickness shall be regard
45、ed as theminimum value of local thickness. In the case of articles having a significant surface area of less than100mm 2 , the minimum thickness shall be regarded as the minimum value of average thickness (seeA.5.2). In the case of printed circuit boards with electroplated-through holes, the measure
46、ments shall also be carried out on the surfaces within the holes, and not only the areas that can be touched with a20mm diameter ball. In the case of flow-melted coatings, the measurements shall be carried out on the as-electroplated condition, prior to flow-melting (seeA.6). The thickness of the co
47、ating shall be determined by either: a) one of the methods given inAppendix C, as specified by the purchaser; or b) any other method the purchaser specifies, provided that it can be demonstrated to have an accuracy of10% or better of the true thickness or is as good as or better than the methods giv
48、en inAppendix C 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 case of dispute, the method referr
49、ed to inC.1.1 shall be used. 9.3 Composition. The tin content shall be in the range55% to70% by mass and shall be within the tolerance on the value specified by the purchaser. The actual tin content shall be shown in the coating classification code and the tolerance on the tin content shall be included in the information to be supplied to the electroplater. A suitable method for determining the tin content of the coating is given inAppendix B and shall be used in case of dispute. 9.4 Adhesion. When tested by one of the methods described inAppendix E (as specified
