Do you know anything about PCB HASL?

What’s PCB HASL?

Tin-sprayed HASL/lead-free HASL (Hot air solder leveling) is a step and process in the production of PCB boards. It is also the main surface treatment used in the PCB 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, and then the excess solder on the PCB board is removed by hot air cutter. Because the surface of printed circuit board after spraying tin is similar to that of solder paste, 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.


What is the role of PCB spray tin?

Prevention and oxidation of bare copper surface. Copper is easily oxidized in the air, causing non-conduction of the PCB pads or reducing soldering performance. By tinning the copper surface, it can effectively isolate the copper surface from the gas and maintain the continuity and solderability of the PCB.

Keep solderability.Other surface treatment methods include: hot melt, organic protective film OSP, chemical tin, chemical silver, chemical nickel gold, electroplated nickel gold, etc.The tin-sprayed board includes two layers of copper and tin, which can adapt to poor environmental conditions and better solder performance. It is more suitable in high temperature and corrosive environments. This board is commonly used in industrial control equipment communications products and military equipment products.

What are the advantages of sprayed tin PCB?

In the usual PCB surface treatment, the tin spraying process is the best solderable, because there is tin on the pads, and when soldering with tin, it is easier to follow the gold-plated plate or rosin and OSP process. For manual soldering, tinning is very easy.


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