There are many friends, they are not very clear about the "hard gold" and "soft gold" on the circuit board. It is still believed that electroplating must be hard gold, while chemical gold must be soft gold. Now let's introduce:
In fact, electroplating itself can be divided into hard gold and soft gold, because hard gold electroplating is actually an electroplating alloy (i.e. gold and other metals), so it is hard and suitable for places requiring force friction. In the electronic industry, it is usually used as the contact point of the plate edge. Soft gold, usually used for aluminum wiring on cob (chip on board) or contact surface of mobile phone keys, has recently been widely used for front and back of BGA carrier.
To understand the origin of hard gold and soft gold, it is best to first understand the gold plating process. Let's not talk about the pickling process first, basically for the purpose of obtaining "gold", electroplate copper on the circuit board, but "gold" can't directly react with copper, so we must first electroplate a layer of "nickel", and then put the gold plating on the top of nickel, so we usually call it electroplating, and its actual name should be called "gold plating nickel".
The difference between hard gold and soft gold is the composition of the layer of gold that is finally gilded. When plating gold, you can choose to plating pure gold or alloy, because the hardness of pure gold is very soft, so it is called "soft gold". Because gold and aluminum can form a good alloy, cob will need the thickness of this pure gold layer for the production of aluminum wire. In addition, if nickel alloy or gold cobalt alloy is selected, it is also called "hard gold" because it is harder than pure gold.
Plating procedures for soft and hard gold:
Soft gold: pickling, nickel plating, pure gold
Hard gold: pickling, nickel plating, pre plating, nickel plating or cobalt alloy.
Most of today's alloys are called electroless nickel plating gold, which has the advantage that nickel and gold can be attached to copper without plating, and the surface is smoother than plating, which is particularly important for reducing the flatness of electronic parts and components.