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With the widespread implementation of lead-free soldering and the widespread use of Immersion Tin board in high-reliability panels. The proportion of surface treatment of Immersion Tin is rising. Therefore, it is very important to understand the characteristics of the surface treatment of Immersion Tin to ensure the reliability of the tin plate.

Immersion Tin (ISn) is a copper surface treatment technology for PCB. The product of this process neither contaminates the solder (unlike the chemical nickel plate) nor creates an additional layer of polyester on the solder mask. By chemical immersion tin, it can be evenly covered with tin in the hole of any size PCB board and the position of the lands. In order to adapt to the global strategic development, the need to gradually realize the development of lead-free and PCB board market. Replacing the current hot air leveling process with a lead-free chemical tin-plating process becomes a prerequisite for the DPMC development plan.

According to IPC, connected to the Electronics Industry Association, ISn is a metal structure deposited by a chemical displacement reaction that is applied directly to the base metal of the board, ie copper. The underlying copper of ISn protection is not oxidized during its expected shelf life.

Immersion tin board reaction principle:

The electroless tin process is an electroless plating process that selectively tins the copper surface of the PCB during production. A dense tin layer having a thickness of about 1 um is formed on the copper surface by a metal ruthenium exchange reaction in a solution.

The board must be cleaned before immersion tin. CIMAPREP PR-514 Acid Cleaner is a concentrate used to remove oil and metal oxide particles from the board. Must be diluted according to the cleaning effect it can achieve. CIMAPREP PR-505 is a micro-etching agent that can be used directly without dilution. It can roughen the surface after micro-etching to provide a homogeneous copper surface that is good for immersion tin.

Advantage:

Suitable for horizontal line production, fine line processing, lead-free soldering, crimping technology. Good flatness, suitable for SMT. Excellent electrical conductivity and solderability can be welded multiple times. The tin layer is lead-free and has no pollution to the environment. The storage period is up to one year. The process is simple and the working environment is good.

Disadvantage:

Need good storage conditions, preferably no more than 6 months to control tin whisker growth. Not suitable for contact switch design. The process requirements for the solder mask process are relatively high, otherwise, the solder mask will fall off. When welding multiple times, it is best to protect with N2 gas. High requirements for incoming materials (uniform copper surface requirements before immersion, no oxidation, fingerprints, glue stains, etc.)