Superb electroplating technology Pogo Pin Rhodium-plated
There are many electroplating processes and materials. Gold plating is our most common processing technology and material, but palladium plating, rhodium plating, and ruthenium plating are better than gold plating.
Gold-plating Gold-plating uses real gold, even if it is only plated with a thin layer, it already accounts for nearly 10% of the cost of the entire circuit board. Gold plating uses gold as the plating layer, one is to facilitate welding, and the other is to prevent corrosion; even the gold fingers of the memory sticks that have been used for several years are still shiny.
Advantages: strong conductivity, good oxidation resistance, long life; dense plating, relatively wear-resistant, generally used in welding and plugging occasions. Disadvantages: higher cost and poor welding strength.
2. Chemical gold/immersion gold Chemical nickel immersion gold (ENIG), also known as chemical nickel gold, immersion nickel gold, abbreviated to chemical gold and immersion gold. Immersion gold is a chemical method, a thick layer of nickel-gold alloy with good electrical properties is wrapped on the copper surface and can protect the PCB for a long time. The deposition thickness of the inner layer of nickel is generally 120~240μin (about 3~6μm), and the deposition thickness of the outer layer of gold is generally 2~4μinch (0.05~0.1μm). Immersion gold can enable PCB to achieve good electrical conductivity during long-term use, and it also has environmental tolerance than other surface treatment processes do not have.
Advantages:
a. The surface of the PCB treated with gold is very flat and has good coplanarity, which is suitable for the contact surface of the button.
b. Immersion gold has excellent solderability, and gold will quickly melt into the molten solder to form a metal compound. Disadvantages: The process is complicated, and the process parameters need to be strictly controlled to achieve good results. The most troublesome thing is that the PCB surface that has been treated with gold is easy to produce black disk benefits, which affects reliability.
3. Compared with nickel and gold, ENEPIG has an extra layer of palladium between nickel and gold. In the deposition reaction of replacing gold, the electroless palladium layer will protect the nickel layer and prevent it. Excessive corrosion of the replacement gold; palladium is fully prepared for the immersion gold while preventing corrosion caused by the replacement reaction. The deposition thickness of a nickel is generally 120~240μin (about 3~6μm), the thickness of palladium is 4~20μin (about 0.1~0.5μm); the deposition thickness of gold is generally 1~4μin (0.02~0.1μm). Advantages: It has a wide range of applications. At the same time, nickel-palladium-gold is relatively immersed in gold, which can effectively prevent connection reliability problems caused by black disk defects. Disadvantages: Although nickel palladium gold has many advantages, palladium is expensive and is a scarce resource. At the same time, like Immersion Gold, its process control requirements are strict.
The chemical properties of rhodium are relatively stable, and it is difficult to react with sulfide and carbon dioxide gas in the air. At room temperature, it is insoluble in nitric acid and its salts, and even insoluble in water. It is more stable to various strong alkalis, but rhodium is soluble in concentrated sulfuric acid. The physical properties of rhodium are relatively good. In addition to good wear resistance and electrical conductivity, it has outstanding reflection ability, and its reflection coefficient can reach 80% (silver is 100%), and it can remain unchanged for a long time. Therefore, it is often used as an anti-silver discoloration coating. After testing, the 0.1um rhodium coating can protect the silver coating from discoloration for several years. The rhodium coating has very low contact resistance and high hardness, so it is often used as a coating for contact points.
The welding performance of rhodium is not very good, because the internal stress of the coating is relatively large. Rhodium plating technology began to be used in the United States in 1930, but it was mainly used for decorative plating. Later, with the rapid development of the electronics industry, rhodium plating played an important role in preventing silver discoloration and electrical contact points. In recent years, rhodium plating has become more popular in the jewelry electroplating industry. Electroplating a layer of rhodium on the surface of silver jewelry can prevent silver discoloration. The price is cheap, and it can also show a platinum-like texture. Since the density of rhodium is much smaller than that of platinum, the cost of rhodium plating is a little lower than that of platinum plating.
