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Chemical nickel gold(ENIG)
Nickel gold is a relatively large surface treatment process. The nickel layer is a nickel-phosphorus alloy layer. According to the phosphorus content, it is divided into high-phosphorus nickel and medium-phosphorus nickel. The application is different.
The advantages of nickel-gold:
Suitable for lead-free soldering-->The surface is very flat, suitable for SMT-->Through holes can also be coated with nickel and gold-->Long storage time, storage conditions are not harsh-->Suitable for electrical testing-->Suitable for switch contact design -->Suitable for aluminum wire binding, suitable for thick plates, strong resistance to environmental attacks.
2. Electroplating nickel gold
Electroplated nickel gold is divided into "hard gold" and "soft gold". Hard gold (such as goldcobalt alloy) is commonly used on gold fingers (contact connection design), and soft gold is pure gold. Electroplating of nickel and gold is widely used on IC substrates(such as PBGA). It is mainly suitable for bonding gold and copper wires. However, the plating of the IC substrate is suitable. The bonded gold finger area needs to be electroplated with additional conductive wires.
The advantages of electroplating nickel gold:
Long storage time>12 months-->Suitable for contact switch design and gold wire binding-->Suitable for electrical test
Weaknesses of nickel-gold electroplating:
Higher cost, thicker gold-->Additional design wire conductivity is needed when electroplating gold fingers-->Because the thickness of gold is not constant, it may cause solder joints embrittlement due to too thick gold and affect strength when applied to welding.--> The problem of surface uniformity of electroplating-->The electroplated nickel and gold do not cover the edge of the wire-->It is not suitable for aluminum wire bonding. Not suitable --> High storage conditions are required.
The advantages and disadvantages of PCB circuit board tin spraying
Tin spraying was a common treatment in the early days of PCBs. Now it is divided into lead spray tin and lead-free spray tin.
The advantages of tin spraying:
Long storage time -->After the PCB is completed, the copper surface is completely wetted (the tin is completely covered before soldering)
Suitable for lead-free soldering-->Mature process-->Low cost-->Suitable for visual inspection and electrical measurement
Weaknesses of tin spraying:
-->Not suitable for wire bonding; due to surface flatness, there are limitations on SMT; not suitable for contact switch design --> Copper will dissolve when spraying tin, and the board will withstand a high temperature --> Especially thick or thin board, The tin spraying has limitations, and the production operation is inconvenient.
