The difference between hard gold and soft gold plating

The so-called hard gold, as the name implies, is to make the coating hard by adding other metals in the gold layer and changing the structure of the gold layer. Commonly used metals are: cobalt, nickel, copper, palladium, indium, and iron, tin, cadmium, etc. in the past. Cobalt and nickel are commonly used at the moment, but in order to adjust the color, a small amount of indium is also added. The hardness of the coating depends on the alloy content. Usually, the hardness of the connector is HV130 - 220. The jewellery is usually 18k gold, and the highest hardness can reach 400 or so. (For example, gold and copper cadmium used in the past, and gold-copper-indium plating used now. )

Hard gold is usually used in places where wear resistance is required, such as connector terminals, jewelry decoration industry, etc.

Soft gold makes it not coated with any other metal or non-metal elements. The coating is soft and the hardness is about Hv70. It is suitable for chip welding (ultrasonic welding). LED industry bonding welding is used more.