26 Layer 0.5 - 6oz Controlled Impedance Pcb

Is gold often used on circuit boards?

 Nowadays, circuit boards are basically made of gold, but now there are technologies that replace gold with metals such as copper and silver. That is, another layer of gold is plated on the copper foil, even if there is a small amount. It is precisely because of gold and precious metals that the recycling of electronic waste products (of course, there are also component recycling).
Many circuit boards need to be gold-plated, and some originality electronics ICs also contain trace amounts of gold.
Gold plating is mainly for anti-oxidation. However, the gold content of the circuit board or chip is very small. The gold of the circuit board must be crushed first, then chemically soaked and then replaced. Using this similar method, the pollution is very, very serious! ! !
In fact, while extracting gold, many other additional products will be obtained, such as copper, silver, etc.
There are many precious metals on the PCB. It is reported that, on average, each smart phone contains 0.05g of gold, 0.26g of silver, and 12.6g of copper. The gold content of a laptop is 10 times that of a mobile phone!
Why are there precious metals on the PCB?
PCB is the support body of Electronic Components. When PCBA Manufacturing requires soldering components on its surface, a part of the copper layer is required to be exposed for soldering. These exposed copper layers are called pads. The pads are generally rectangular or round with a small area. Therefore, after the solder mask is painted, the only copper on the pads is exposed to the air.
For the exposed pads on the PCB, the copper layer is directly exposed. This part needs to be protected to prevent it from being oxidized.

The copper used in the PCB is easily oxidized. If the copper on the pad is oxidized, it will not only be difficult to solder, but also the resistivity will greatly increase, which will seriously affect the performance of the final product. Therefore, the pad is plated with inert metal gold, or the surface is covered with a layer of silver through a chemical process, or a special chemical film is used to cover the copper layer to prevent the pad from contacting the air. Prevent oxidation and protect the pads, so that they can ensure the yield in the subsequent soldering process.
Gold, silver and copper on PCB
1. PCB copper clad laminate
Copper clad laminate is a plate-shaped material made by impregnating glass fiber cloth or other reinforcing materials with resin on one side or on both sides with copper foil and hot pressing.
Take glass fiber cloth-based copper clad laminate as an example. Its main raw materials are copper foil, glass fiber cloth, and epoxy resin, which account for about 32%, 29% and 26% of the product cost, respectively.
Copper clad laminate is the basic material of printed circuit boards, and printed circuit boards are the indispensable main components for most electronic products to achieve circuit interconnection. With the continuous improvement of technology, some special electronic copper clad laminates can be used in recent years. Directly manufacture printed electronic components. The conductors used in printed circuit boards are generally made of thin foil-shaped refined copper, that is, copper foil in a narrow sense.
2. PCB Immersion Gold Circuit Board
If gold and copper are in direct contact, there will be a physical reaction of electron migration and diffusion (the relationship between the potential difference), so a layer of "nickel" must be electroplated as a barrier layer, and then gold is electroplated on top of the nickel, so we generally call it The actual name of electroplated gold should be called "electroplated nickel gold".
The difference between hard gold and soft gold is the composition of the last layer of gold that is plated on. When plating gold, you can choose to electroplate pure gold or alloy. Because the hardness of pure gold is relatively soft, it is also called "soft gold" . Because "gold" can form a good alloy with "aluminum", COB will particularly require the thickness of this layer of pure gold when making aluminum wires. In addition, if you choose to electroplated gold-nickel alloy or gold-cobalt alloy, because the alloy will be harder than pure gold, it is also called "hard gold".
The gold-plated layer is widely used in the component pads, gold fingers, and connector shrapnel of the circuit board. The motherboards of the most widely used mobile phone circuit boards are mostly gold-plated boards, immersed gold boards, computer motherboards, audio and small digital circuit boards are generally not gold-plated boards