▪ Usual thickness: 0.7 µm (0.00003”) to 1.3 µm (0.00005”) gold (99.7%) over 5.0
▪ µm (0.0002”) nickel or 0.2 µm (0.000008”) to 0.3 µm (0.00001”) gold (99.7%) over
▪ 5.0 µm (0.0002”) nickel for a solderable surface
▪ Very good for corrosion resistance
▪ Rated at 130-220 Knoop hardness
▪ Very good wear resistance
▪ Excellent for surface rotary switches, on-off contacts, and edge connectors
▪ Very good shelf life
There are a lot of friends in the rear assembly plant, for the circuit board of hard gold and soft gold has not been very clear, some people have always thought that electroplating must be hard gold, and chemical gold must be soft gold, in fact, this division can only say half right
Actually electroplating itself can be divided into hard gold and soft gold oh.Because electroplating hard gold is an alloy, so the hardness is relatively hard, suitable for use in the need of force friction place, in the electronics industry, generally used as a PCB board edge contact point (commonly known as goldfinger);Soft gold is generally used for the aluminum wire On the COB (Chip On Board) or the contact surface of mobile phone buttons. Recently, it is widely used On the two sides of BGA Board.
To understand the origin of hard gold and soft gold, it is best to have a little understanding of the plating process, let’s not talk about the previous pickling process.The purpose of electroplating is basically to electroplate the gold on the copper sheet of the circuit board, but the gold cannot react directly with the copper, so it is necessary to electroplate a layer of “nickel”, and then the gold plating on the nickel above, so we commonly called electroplating, its actual name is called “electroplating nickel gold”.
And the difference between hard and soft gold, is finally up to the gold plating, gold-plated can choose pure gold plating or alloy, because of the hardness of pure gold is soft, so it is called “soft gold”, because gold and aluminum trip good alloy, so the COB line when it comes to special requirements for the thickness of this layer of gold.In addition, if the choice of electroplated nickel alloy or gold cobalt alloy, because the alloy is harder than pure gold, so it is also called “hard gold.”
Soft gold: pickling → plating nickel → plating pure gold
Hard gold: pickling → electroplating nickel → preplating → electroplating nickel or alloy alloy
Today’s Electroless Nickle Immersion Gold is mostly used as a surface treatment for this type of ENIG(Electroless Nickle Immersion Gold).The advantage is that nickel and gold can be attached to the same skin without electroplating, and the surface is smoother than electroplating, which is especially important for shrinking electronic parts and components requiring flatness.
Because ENIG USES a chemical process to produce the effect of a gold layer on the surface, the maximum thickness of the gold layer is not as thick as that of electroplating, and the lower it goes, the less gold it contains.
Because ENIG’s gold-plated layer is pure gold, it is often classified as “soft gold”, and it has also been used as COB aluminum wire, but it must be strictly required that the thickness of the gold layer is at least 3 to 5 microinches (” “), more than 5 microinches of gold layer is difficult to achieve, too thin layer of gold will affect the adhesion of the aluminum wire;On the other hand, regular electroplating can easily be more than 15 microinches.But the price also increases with the thickness of the gold layer.
The word “Flash gold” comes from Flash, which means rapid gold plating. In fact, it is the “pre-gold plating” process of hard gold plating. It USES a large current and a thin liquid containing gold to form a layer of gold with a fine density in the nickel layer, which is very thin, for the subsequent electric gold plating of nickel or gold and cobalt alloy.Because there is less electroplating behind the process, so the cost is much cheaper than the real electroplating.But also because the gold layer is very thin, can not effectively cover the bottom of the nickel layer, easy to cause oxidation, weldability is very bad.
At present many circuit board surface treatment, electroplating nickel gold cost compared with other surface treatment methods (such as ENIG, OSP), relatively less so now, unless special purpose, such as coupling plug-in processing, and with the demand of the sliding contact element (gold finger), etc., in terms of the circuit board surface treatment technology, gold plating nickel coating has good friction resistance and excellent antioxidant ability is second to none
1、What to do with gold finger pcb