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#298 Tin Plating for Electronics

Category : Electroplating
June30, 2017

Tin plating, or tinning, has long been known for hot-dipping of iron plates and has been used for various cans.
Recent improvement in tinning baths has achieved enhanced luster, solderability, and corrosion resistance and has widened the applications of tinning to electronic components. It is now widely used as a plating film with high long-term reliability to substitute for expensive gold plating.
Characteristics and applications of tin plating film are summarized in [Table 1].

[Table 1] Characteristics and applications of tin plating film
CharacteristicsApplications
Stability against organic acidsSteel sheet for cans, tableware, water heaters, etc.
Flexibility, lubricityBearings and sliding components for various machinery, prevention of steel nitriding, etc.
Solderability, electrical characteristicsElectronic components, semiconductor components, mechanical components, etc.

[Table 2] shows the types of tinning baths and hardness of the films.The hardness of plating film shown here is a reference, as it varies depending on brightening agent and plating conditions.
Bright plating has better solderability than matt plating.It also has better corrosion resistance. Bright tinning to a thickness of 5 um or more leaves almost no pinholes.
  [Table 2] Types of tin plating baths and hardness of the films
Types of plating bathsHardness of films (Hv)
Acid bright plating bath40-60
Acid matt plating bath5-8
Alkaline matt plating bath3-4
Neutral semi-bright plating bath10-15
Neutral bright plating bath30-50

Precautions for the use of tinning on electronics include the need for1. anti-discoloration treatment and 2. whisker mitigation measures.

*Whiskers are fibrous metal crystals that look like cat whiskers and that grow on untreated metal surfaces. These may cause an accident such as shorting of an electrical circuit for downsized and high-density electronic and communication equipment.One of the whisker mitigation techniques is reflow treatment (melting treatment) which co-precipitates5-10% of lead with tin (alloy plating).

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