High‑power conductive copper busbars and integrated shunt resistors commonly adopt a dual‑layer electroplating structure: 1.5‑4μm nickel underlayer + 3‑8μm tin top layer, balancing corrosion resistance and electrical assembly requirements.

Acting as a barrier layer, the dense nickel underlayer blocks outward diffusion and oxidation of copper substrate ions. It improves plating adhesion, enhances wear‑resistant and high‑temperature‑resistant performance, and mitigates fretting corrosion under vibration. This makes it ideal for demanding applications such as energy‑storage systems, DC charging piles and vehicle‑mounted electronic controls.

The outer tin coating delivers stable low contact resistance and excellent solderability. It deforms plastically under bolt compression, ensuring long‑term low‑thermal‑resistance performance at connection points.

Single tin plating suffers from Cu‑Sn interdiffusion, tarnishing and discoloration. Nickel‑only plating shows poor solderability. The combined nickel‑tin plating leverages strengths of both layers while avoiding their drawbacks. It is widely used in energy‑storage shunts, PV inverter busbars and high‑power new‑energy electrical connectors.

Key challenge for metallographic preparation of Ni‑Sn double‑layer coated busbars & shunts: handling this alternating soft‑hard thin‑layer structure.

Precise control over three critical steps is essential:

✅ Cutting: avoid thermal damage

✅ Mounting: prevent compression‑induced deformation

✅ Grinding & polishing: eliminate delamination and plastic flow

Standardized operation minimizes preparation artifacts, faithfully restores real microstructure and coating thickness, and delivers reliable metallographic data for coating‑thickness verification and process quality control.

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