1. IPC-2221 4.4.4 Gold Plating A variety of gold platings are available for depositions on printed boards. These may be electrolytic, electroless, or immersion deposits. The electrolytic deposition may come in 24k soft gold, 23+k hard gold (hardening uses trace amounts of cobalt, nickel, or iron which are co-deposited with the gold), or the plating may be a lower karat alloy (14k-20k) for some applications. Gold plating serves several purposes:

2. IPC-2221 4.4.4 Gold Plating 1. To act as a self lubricating and tarnish resistant contact for edge board connectors (see Table 4-3). Hard electrolytic gold plating is most often used for this application. 2. To prevent oxidation of an underlying plating such as nickel and electroless nickel to enhance solderability and extend storage life. Electrolytic, immersion and electroless gold are most often used for this purpose.

3. IPC-2221 4.4.4 Gold Plating 3. To provide a wire bonding surface. This application employs a soft 24k electrolytic gold, see Table 4-3 for thickness. 4. To provide an electrically conductive surface on printed wiring boards when electrically conductive adhesives are used. A minimum thickness of 0.25  m is recommended. 5. To act as an etch resist during printed board fabrication. A minimum thickness of 0.13  m is recommended.

4. IPC-2221 4.4.4 Gold Plating Electrolytically deposited gold is often specified as required to meet MIL-G-45204 with the type and grade selected to satisfy the different applications. A low-stress nickel or electroless nickel shall be used between the gold overplating and the basis metal when gold finish is to be used for electrical or wire bonding.