What is Gold plating
The gold plating of the whole board generally refers to “electroplating gold”, “electroplating nickel gold plate”, “electrolytic gold”, “electric gold” and “electric nickel gold plate”. There is a distinction between soft gold and hard gold (generally hard gold is Used for gold fingers), the principle is to dissolve nickel and gold (commonly known as gold salt) in chemical water, immerse the circuit board in the electroplating tank and turn on the current to form a nickel-gold plating layer on the copper foil surface of the circuit board. Electro-nickel gold is widely used in electronic products because of its high hardness, abrasion resistance and resistance to oxidation.
The gold plating of the whole board generally refers to “electroplating gold”, “electroplating nickel gold plate”, “electrolytic gold”, “electric gold” and “electric nickel gold plate”. There is a distinction between soft gold and hard gold (generally hard gold is Used for gold fingers), the principle is to dissolve nickel and gold (commonly known as gold salt) in chemical water, immerse the circuit board in the electroplating tank and turn on the current to form a nickel-gold plating layer on the copper foil surface of the circuit board. Electro-nickel gold is widely used in electronic products because of its high hardness, abrasion resistance and resistance to oxidation. Gold plating uses the principle of electrolysis, also known as electroplating. The surface treatment of other metals is mostly electroplating.
In actual product applications, 90% of the gold-plated boards are immersion gold boards, because the poor solderability of the gold-plated boards is his fatal defect, and it is also the direct reason why many companies abandon the gold-plating process!
- For the surface mount process, especially for ultra-small surface mounts of 0201 and below, because the flatness of the pad is directly related to the quality of the solder paste printing process, it has a decisive influence on the quality of the subsequent reflow soldering, so the whole board Gold plating is common in high-density and ultra-small surface mount processes.
- In the trial production stage, due to factors such as component procurement, it is often not that the PCB board production is completed and the SMT placement process can be carried out immediately. Sometimes it takes several weeks or even months to start to arrange the SMT placement and the gold-plated board. The shelf life is many times longer than that of pewter, so everyone is willing to use it. Besides, the cost of the gold-plated PCB in the sample stage is almost the same as that of the lead-tin alloy board. But as the wiring becomes denser, the line width and spacing have reached 3-4MIL. Therefore, the problem of gold wire short circuit is brought about. As the frequency of the signal becomes higher and higher, the signal transmission in the multi-plated layer caused by the skin effect has more obvious influence on the signal quality. (Skin effect refers to: high frequency alternating current, the current will tend to concentrate on the surface of the wire. According to calculations, the skin depth is related to frequency.)
What is Immersion Gold(ENIG)
Immersion gold(ENIG) is a method of chemical oxidation-reduction reaction to generate a layer of plating, generally thicker, is a kind of chemical nickel-gold layer deposition method, can reach thicker gold.
There are many PCB surface processes, such as HASL, OSP, ENIG, GOLD PLATING and so on. According to different electronic components and different product quality levels, the corresponding surface technology will be selected. With more and more advanced technical capabilities, IC pins are becoming more and more dense, and it is difficult for HASL to flatten the thin-foot pads, which makes it difficult to solder SMT patches. In addition, HASL is ready for use. The lifespan is also shorter, and the PCB made of gold-plated board can just solve these problems. For some ultra-small surface mount boards such as 0402 and 0201, it plays a decisive role in quality, so the whole board gold plating is used in high-precision and ultra-small It is more common in the patch process.
PCBs using immersion gold technology mainly have the following characteristics:
- Because the crystal structure formed by immersion gold and gold plating is different, immersion gold will be golden yellower than gold plating, and customers will be more satisfied.
- Because the crystal structure formed by immersion gold and gold plating is different, immersion gold is easier to weld than gold plating, and will not cause poor welding and cause customer complaints.
- Because the immersion gold board only has nickel and gold on the pad, the signal transmission in the skin effect will not affect the signal on the copper layer.
- Because the crystal structure of immersion gold is denser than that of gold plating, it is not easy to produce oxidation.
- Because the immersion gold board only has nickel and gold on the pads, it will not produce gold wires and cause slight shortness.
- Because the immersion gold board only has nickel and gold on the pads, the solder mask on the circuit and the copper layer are more firmly bonded.
- The project will not affect the distance during compensation.
- Because the crystal structure formed by gold-immersion and gold-plating is different, the stress of the gold-immersion plate is easier to control. For products with bonding, it is more conducive to bonding processing. At the same time, it is precisely because the immersion gold is softer than the gilding, so the immersion gold plate is not wear-resistant as the gold finger.
- The flatness and stand-by life of the immersion gold board are as good as the gold-plated board.
The difference between ENIG and gold-plated circuit boards.
In the process of PCB circuit board proofing, gold plating and gold plating are widely used in the surface treatment process; the most fundamental difference between them is that gold plating is hard gold, and ENIG is soft gold.
1.(ENIG)Immersion gold is different from the crystal structure formed by gold plating. Immersion gold is much thicker than gold plating; Immersion gold will be golden yellow, which is more yellow than gold plating.
2.Immersion gold is easier to weld than gold plating, will not cause poor welding, and the stress of the sinking plate is easy to control. At the same time, since sinking gold is softer than gold plating, gold-plated gold fingers are more difficult to wear.
3.There is only nickel and gold on the pads of the sinking board, and the skin effect of the signal is transmitted on the copper layer, which will not affect the signal.
4.Immersion gold is denser than gold-plated crystal structure, and it is not easy to produce oxidation.
5.Gold plating is easy to short-circuit the gold wire; there is only nickel-gold on the pad of immersion gold, so it is not easy to produce gold wire short-circuit.
6.The combination of wire resistance and copper layer of immersion gold board is stronger.
7.The immersion gold process is generally used for boards with relatively high requirements, and has good flatness. Generally, deposits are used, and there is generally no black pad phenomenon after deposition. Its flatness and service life are better than gold-plated plates.