1. ImSn:
The ImSn involves immersing the entire PCB board in a solution containing molten tin, so that the entire surface of the PCB board is covered with a thin layer of tin, thereby achieving the effect of protecting the circuit and increasing soldering ability.
The ImSn has the following characteristics:
Large coverage area: The entire surface of the PCB board can be coated with tin, ensuring that all solder joints are fully protected without solder leakage or poor soldering.
Durable solder joints: The tin layer in the sinking process is relatively thick, which can make the solder joints more sturdy.
Wide applicability: The tin deposition process can be applied to most PCB boards.
2. HASL:
The HASL is to spray molten tin onto the surface of a PCB board, forming a thin layer of tin to protect the circuit and increase soldering ability.
The HASL has the following characteristics:
Small coverage area: The HASL can only spray onto the parts that need to be welded, and cannot cover the entire surface of the PCB board.
Small solder joints: In the HASL, the tin layer is relatively thin, which can make the solder joints smaller.
Narrow applicability: The HASL is only applicable to specific PCB boards, such as SMT (Surface Mount Technology) soldering.
HASL can be divided into lead-based HASL and lead-free HASL. HASL was once the most important surface treatment process in the 1980s, but nowadays, fewer and fewer circuit boards choose HASL because circuit boards are developing towards "small and fine" direction. HASL can lead to poor production caused by tin beads and spherical tin dots during the soldering of fine components, In order to pursue higher process standards and production quality, PCBA processing plants often choose ENIG and SOP surface treatment processes.
Advantages of lead-based HASL: lower price, excellent welding performance, better mechanical strength, glossiness, etc. compared to lead -based HASL.
Disadvantages of lead based HASL: Lead based HASL contains lead heavy metals, which is not environmentally friendly and cannot pass environmental evaluation such as ROHS.
Advantages of lead-free HASL: low price, excellent welding performance, and relatively environmentally friendly, able to pass environmental evaluation such as ROHS.
Disadvantages of lead-free HASL: mechanical strength, glossiness, etc. are not as good as lead-free HASL.
