BS 4393:1991

Committees responsible
Foreword
Specification
1. Scope
2. Definitions
3. Materials
4. Solderability
5. Dimensions and tolerances
6. Bend test for robustness of termination
7. Elongation
8. Bend test for coating adhesion
9. Sampling
10. Packaging and labelling
Appendices
A. Information to be supplied by the purchaser
B. Methods for use in cases of dispute for the
    determination of the thickness of tin and tin-lead
    coating and undercoat
C. Method for use in cases of dispute for the
    determination of the composition of tin and tin-lead
    coatings by atomic absorption spectrophotometry
D. Method for the detection of lead in tin and tin-lead
    coatings
E. Method for bend test
F. Guidance notes to aid selection of suitable basis
    wire and coatings for component terminations
Tables
1. Composition of the preferred tin or tin-lead
    solderable coatings
2. Average thickness for solderable coating
3. Density of tin-lead alloys
4. Calibration solutions
Figures
1. Rotor head for bend tester
2. Arrangement of bend test apparatus

Requirements for solderability, mechanical properties, materials of manufacture, etc., for wires intended for component leads in the electronics industry, where solderability is a major criterion. It deals with wire in a range of materials, in the size range 0.25 mm to 1.20 mm.

This British Standard specifies requirements for the solderability, mechanical properties, sampling, packaging and materials of manufacture for tin and tin-lead coated wire. It applies to coated wire which is primarily intended for component leads in the electronics industry, where good solderability is the main criterion, and where the basis wire has a nominal diameter within the range 0.25 mm to 1.20 mm. A range of materials is specified for the basis wire.

Details of information to be supplied by the purchaser are given in appendix A.

The coating thickness range, necessary to achieve good solderability, is specified.

Test methods, particularly for use in cases of dispute, for the measurement of coating thickness, for the determination of the tin content of the coating and for the detection of lead in the coating are given in appendices B, C and D respectively. Appendix E gives the method for carrying out the bend test, which is used for assessing the robustness of the termination and for the coating adhesion.

NOTE 1. Guidance notes to assist the purchaser/user in the selection of the most appropriate basis wire and coating are given in appendix F.

NOTE 2. The titles of the publications referred to in this standard are listed on the inside back cover.