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#317 Tin-Lead Alloy Plating

Category : Electroplating
November10, 2017

JIS defines the requirements on plating applied over iron, copper, or their alloy substrates, in order to add solder wettability, electrical properties, and corrosion resistance to electrical/electronic components, as described hereinafter.

(1)Type and grade of plating

[Table 1] Chemical composition (%) of plating film
TypeSnPbOther elements
Type I70 or moreRemainder1 or less
Type II50 or more and less than 70Remainder1 or less

[Table 2] Type and grade of plating
TypeGradeMinimum plating thickness
(µm)
Reference
Operating environment and conditionRemarks
Type IGrade 11Normal indoor environmentFrequently used for semi-conductor parts
Grade 23
Grade 35
Grade 48Highly humid indoor environment
Grade 510
Type IIGrade 11Normal indoor environmentFrequently used for printed-wiring boards
Grade 23
Grade 35
Grade 48Highly humid indoor environment
Grade 510

(2)Appearance of plating

The visual inspection will be performed in the same manner as the other types of plating. The plating surface should be flat and free from defects, including burnt or swollen areas, lumps, scratches, pits, flaking, cracks, and exposure of substrates or undercoat.

(3)Chemical composition of plating film

The chemical composition of plating film can be measured by the fluorescence X-ray analysis, and so on.

(4)Minimum thickness of plating film

The plating thickness can be measured by instruments, such as a fluorescent X-ray film thickness meter and a magnetic film thickness meter. In both cases, the values shown in Table 2 must be satisfied.

(5)Plating adhesion

It should be measured by conducting an adhesion-tape test, a bending test, a thermal-shock test, and so on.

(6)Corrosion resistance of plating

The corrosion resistance must be verified to be at least rating number 9 by conducting a neutral salt spray test or a test method agreed between the parties concerned.

(7)Solder wettability of plating

Just like the case of silver coatings applied for engineering purposes, the following solder wettability test must be conducted:Immerse the flux-treated sample into a soldering bath heated at 250°C for three seconds, and shake the residual liquid off. Check the soldering surface and evaluate the property.

(8)Stress relief before plating

To include a heat treatment process for reducing residual stress on steel/copper alloy products before plating, the conditions must be determined and agreed by the parties concerned.

(9)Plating name and symbol

●Ep-Cu/Ni/Sn(75)-Pb5

Tin (75%)-lead alloy plating with a thickness of 5 µm over nickel base-coat plating on a copper substrate

●Ep-Cu/Ni/Sn(75)-Pb[3]

Type I/Grade 3 tin-lead alloy plating deposited over nickel base-coat plating on a copper substrate

●Ep-Fe/Cu/Sn(75)-Pb5

Tin (75%)-lead alloy plating with a thickness of 5µm over copper base-coat plating on an iron substrate

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