Lead Free PCB Surface Finishes

Gold Finish

May be Electrolytic Electroless, or Immersion
 

-ENIG
(Electroless Nickel Immersion Gold)

2-5 micro inches. Purpose: To prevent oxidation, extend shelf life, provide a wire bonding surface (when aluminum wire is used), and used to provide an electrically conductive surface on PCBs. Used for solderability when the flatness of the pad is critical. ENIG has shelf life longer then 12 months.
 

-Hard Gold

Purpose: Used for Gold Fingers (minimum 30 micro inches), soldering (maximum 17 micro inches), to prevent oxidation and extend shelf life.
 

-Soft Gold

Purpose: Used for wire bonding (Ultrasonic minimum 2 micro inches/Thermasonic minimum 30 micro inches) and to prevent oxidation and extend shelf life.
 

Immersion Silver

Use for solderability purposes (2-10 micro inches). Used for solderability when the flatness of the pad is critical.
 

Lead Free Solder

Use for solderability purposes (2-5 micro inches). Used for solderability when the flatness of the pad is not critical.
 

OSP
Organic Solderability Preservatives)

Used for solderability when the flatness of the pad is critical.

White Tin (Immersion Tin)

Used for solderability when the flatness of the pad is critical.