He XiaoJin, zhujin?

I must first declare that this article only speaks on personal experience and cognition, because I have not been in the circuit board manufacturing industry, for more information about the hardware, software, and flash on the circuit board, I have asked the relevant circuit board about the following for many years. If there is any error, please leave a message.
There are a lot of friends who are working in the later assembly plant. The hard gold and soft gold on the circuit board have been unclear, and some people still think that the gold plating must be hard gold, the chemical gold must be soft gold. In fact, such a method can only be half right.

Nickel Plating
ActuallyGold plating can be divided into hard gold and soft gold.. BecausePlating hard gold is actually an alloy., So the hardness will be relatively hard, suitable for use in places where stress friction is needed, in the electronics industry, is generally used as the shop Board edge contact point (commonly known as "golden finger"); andSoft Gold is generally used for CoB (chip on board) above the aluminum wireOr the contact surface of the mobile phone buttons, which has recently been widely used on both sides of the BGA board.
If you want to know the origin of hard and soft gold, you 'd better first understand the plating process. Aside from the pickling process, the purpose of electroplating is to plating the "gold" on the copper skin of the circuit board. However, the "gold" cannot directly react with the copper skin, therefore, we must first plating a layer of nickel and then plating the gold on the nickel. Therefore, we generally call the plating method. The actual name should be "nickel plating gold 」.
The difference between hard gold and soft gold is the final gold plating,When plating gold, you can choose to plating pure gold or alloy.BecauseThe hardness of pure gold is soft, so it is called "soft gold 」BecauseGold and aluminum can form a good alloy, so cob in ?? The thickness of the layer of gold is especially required when the aluminum wire is laid.. In addition, if you choose gold-plated nickel alloy or gold cobalt alloy, because the alloy is harder than pure gold, it is also called "Hard Gold 」.
Softbank:Pickling → Nickel Plating → pure plating gold
Hard Gold:Pickling → Nickel Plating → pre-plating → electroplating nickel or cobalt alloy

 

Finalize
Most of the current gold conversion methods are called the surface treatment method of the ENIG (electroless nickle Immersion Gold. Its advantages are:Plating Process is not requiredThe nickel and gold can be attached to the copper skin, andThe surface is more smooth than the plating.This is especially important for shrinking electronic parts and components requiring flatness.
Since ENIG uses the chemical replacement method to produce the effect of the surface gold layerThe maximum thickness of the Gold Layer cannot reach the same thickness as the gold plating, and the more gold the base layer, the less.
BecauseThe gold plating layer of ENIG is pure gold., So it alsoOften classified as "soft gold 」And some people take it as the surface treatment of CoB aluminum wire, but the gold layer thickness must be at least 3 ~ 5 microinches (μ "), generally more than 5μ" of the gold layer is difficult to achieve, too thin gold layer will affect the aluminum line adhesion; the general plating can easily reach more than 15 microinches (μ. But the price also increases with the thickness of the gold layer.

 

Flash gold)
The word "flash gold" is derived from flash, which means fast gold plating. In fact, it isPreplating process for hard plating, Refer to the process description of nickel plating gold, itUsing a large current and a liquid tank with a thick gold content, a layer of density is formed first in the nickel layer.,Thin gold plating layer for subsequent plating of nickel or cobalt alloy can be easily carried out. Because the subsequent electronic plating procedures are missing, the cost is much cheaper than the real electronic plating. However, because the gold layer is very thin, it cannot effectively cover the nickel layer under it, which may easily lead to oxidation during storage and affect solderability.
According to the current surface treatment methods of many circuit boards, the cost of nickel plating gold is relatively higher than that of other surface treatment methods (such as enig and osp), so it is rarely used now, unless it is used for special purposes, such as contact surface handling of connectors and the need for slide contact elements (such as golden finger ...) As far as current circuit board surface processing technology is concerned, the plating of nickel plating gold has good anti-friction ability and excellent anti-oxidation ability is still incomparable.

He XiaoJin, zhujin?