What is hard gold on PCB?
Gold plating can be divided into hard gold plating solution and soft gold plating. Electroplated hard gold is alloy, so its hardness is relatively hard. It is suitable for use in places where friction is required. It is commonly used as PCB board edge contact point (commonly known as golden finger). Soft gold is generally used for aluminium wire on COB (Chip On Board) or mobile phone button contact surface. Recently, it has been widely used on both sides of BGA board. The difference between hard gold and soft gold is the composition of the last layer of gold plated. When plating gold, you can choose pure gold or alloy. The hardness of pure gold is softer, so it is also called "soft gold".
Why does the gold wire bonding area of PCB require hard gold plating solution? Be careful:
1. This may be a misunderstanding. In fact, all gold wire binding products and binding areas must be soft gold.
2. Hard gold has high hardness, which is not conducive to making gold thread. So soft gold should be used.
3. When the gold thread is tied and struck, it is struck in the gold layer, so the gold thickness is required.
4. In the industry, the thickness of soft gold is usually more than 0.3um.
Hard gold and soft gold belong to electrolytic gold in the process. As long as they are plug-and-touch resistant, hard gold is used, such as Card board of golden finger, Keypad, calculator board, etc. But Wire bonding takes soft gold and high purity gold plating.