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.

Purposes of 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 several 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)
• ImmAg (immersion silver)
• ImmSn (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)