Packaging and assembly

In leadframe packages, what is the main purpose of plating the exposed leads with tin (Sn)-based plating?

  1. ATo improve solder wetting for reliable soldering to the board and to prevent lead oxidation
  2. BTo make the leads shiny for appearance
  3. CTo make the leads insulating
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Answer: A. To improve solder wetting for reliable soldering to the board and to prevent lead oxidation

Lead surfaces of copper alloy and similar oxidize easily, and solder does not wet them well as is. Tin-based plating lets solder wet readily, making joints reliable during assembly. With the move to lead-free, tin-lead plating was replaced by pure tin and similar plating.

  • A. Correct. It improves solderability and prevents oxidation.
  • B. It is not for appearance.
  • C. Plating is metal and does not make the leads insulating.
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