DFM 101: Final Finishes ENEPIG and IAg


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Introduction
One of the biggest challenges facing PCB designers is not understanding the cost drivers in the PCB manufacturing process. This article is the latest in a series that will discuss these cost drivers (from the PCB manufacturer’s perspective) and the design decisions that will impact product reliability.

Final Finishes
Final finishes provide a surface for the component assembler to either solder, wire bond, or conductively attach a component pad or lead to a pad, hole, or area of a PCB. The other use for a final finish is to provide a known contact resistance and life cycle for connectors, keys, or switches. The primary purpose of a final finish is to create electrical and thermal continuity with a surface of the PCB.

There are a number of final finishes in use in the industry today, including:

  • ENIG (electroless nickel, immersion gold)
  • ENIPIG (electroless nickel, immersion palladium, immersion gold)
  • ENEPIG (electroless nickel, electroless palladium, immersion gold)
  • IAg (immersion silver)
  • ISn (immersion tin)
  • Sulfamate nickel/hard or soft gold (Electrolytic nickel/gold)
  • HASL (hot air solder leveling)
    • SnPb (63/37 tin/lead)
    • LF (lead free)
  • OSP (organic solderability preservative)

Final finishes are primarily application driven, so there are a number of considerations that should be part of any decision to choose a final finish.

To read this entire article, which appeared in the September 2022 issue of Design007 Magazine, click here.

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