Spray Tin Board
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Tin-sprayed HASL/lead-free HASL (Hot air solder leveling) is a step and process in the production of PCB boards. Such as spray tin board. Most commonly used in the industry. The process involves immersing the circuit board in a tin/lead alloy bath. Then using a “gas knife” to remove excess solder and blowing hot air across the circuit board surface.
Specifically, the PCB board is immersed in the molten solder pool, so that all exposed copper surfaces are covered by solder. Then the excess solder on the PCB board is removed by hot air cutter. Because the surface of the PCB after spraying tin is similar to that of solder paste. So the welding strength and reliability are better.
However, due to its processing characteristics, the surface roughness of the tin-plated treatment is not good, especially for small electronic components such as BGA, because of the small welding area, if the flatness is not good, it may cause short-circuit problems, so it needs to be leveled. Better process to solve the problem of tin plate.
Generally, the gold process is selected (note that it is not a gold plating process), and the principle and method of the chemical displacement reaction are used for reworking to increase the thickness of the nickel layer of 0.03~0.05um or 6um to improve the surface flatness.
The main functions of the PCB spray tin board are as follows:
1. Prevention and oxidation of bare copper surface; copper is easily oxidized in the air, causing the PCB pad to be non-conducting or reducing the soldering performance. By tinning on the copper surface, the effective copper surface can be isolated from the gas to maintain the PCB. Continuity and solderability.
2. Maintain solderability; other surface treatment methods include hot melt, organic protective film OSP, chemical tin, chemical silver, chemical nickel gold, electroplated nickel gold, etc.
But the best cost-effective tin-plated PCB process Characteristics. The tin-plated plate consists of copper and tin two-layer metal which can adapt to the poor environment and the soldering performance is better in high temperature and corrosive environment. This kind of board is widely used in industrial control equipment communication products and military equipment products.
The advantages of tin-plated PCB: In the usual PCB surface treatment, the tin-spraying process is called the best solderability, because there is tin on the pad when soldering tin, with a gold-plated plate or rosin and OSP The process is quite easy. For hand soldering, it is very easy to apply in.