Micro-Nano Processing | Introduction to Electroplating Process

Electroplating is the process of depositing a metal or alloy on the surface of a substrate using the principle of electrolysis to form a uniform, dense, and well-bonded metal layer. Compared to thin film deposition techniques such as CVD and PVD, electroplating can use the principle of electrolytic deposition of metals to precisely replicate certain complex or specially shaped devices, and can increase the thickness of metals indefinitely.

1. Uses, advantages and disadvantages of common plating metals

MetalCommon UsesAdvantagesNot enough
CopperPrinted circuit boards, anti-carburization, increased conductivity, friction reduction during extrusion, repair of part dimensions, preparation of copper bumps, TSV, priming, conductivityGood electrical conductivity, low stress, improved adhesion of plating layer and corrosion resistanceCopper is easy to oxidize, post-treatment needs to be done to prevent oxidation
NickelElectrode materials, decorative and protective plating, and<br><br>priming,<br><br>MEMS structure.Good plasticity, easy to extend the pressure, has good mechanical processing and mechanical properties, good stability, anti-oxidation, corrosion resistance, electroplated nickel deformation is small, low roughness, wear-resistantMay be magnetic<br><br>Nickel is easy to passivation, need to try to complete the plating at once, the intermediate power failure is prone to plating layer delamination.
GoldApplications in the electronics industry, aerospace, aviation, microelectronics and decorative technology, electrical conductivity, wire bondingExcellent chemical stability. Soft gold is soft, very good ductility, strong bonding; hard gold has good wear resistance and is aesthetically pleasing. Used to improve conductive contact impedance and enhance signal transmission.High gold cost.
SilverElectrode material, conductiveGood chemical stability, good aesthetics, improved conductive contact impedance, improved signal transmissionLight sensitive, easily oxidized
Iron-NickelSoft magnetic materialsStrong magnetic properties, its corrosion resistance is comparable to that of nickel plating, its hardness is higher than that of nickel plating, and its toughness is better than that of bright nickel plating 
Chromium NickelResistors, thermocouples, gears, decorative platingHigh hardness, heat resistance, with wear resistance, corrosion resistance, high resistance, oxidation resistance, good stabilityDifficult to thicken the plating
TinApplication to the preparation of solderable plating materialsGood solderability 
PlatinumDecoration, semiconductor package parts, electrodesSoft texture, good ductility, good chemical stabilityPlating temperature up to 92°C
PalladiumDecorative, semiconductor packagesChemically stable, good corrosion resistance, high plating hardness, very low and unchanging contact resistanceRequires high concentration of main salt in the plating solution

2. Factors affecting the quality of plating

There are many factors affecting the quality of electroplated films, including current density, electric field distribution, line width, plating solution composition, and circulation method.

Tip effect: At the edge and tip of the workpiece or pole plate, more power lines tend to gather, a phenomenon called tip effect or edge effect. In plating, the tip effect can thicken, grow burrs or scorch the edges of the plating.

Current density: In electroplating production, the current passing through the workpiece surface per unit area is often called current density, which is usually measured in amperes per decimeter2 (A/dm2 or ASD). In general, low current density crystallization is delicate and soft, slow deposition speed and low productivity; high current density crystallization is coarse (burnt and powdered in serious cases) and hard, fast deposition speed and high productivity.


Impurities: All plating solutions contain impurities, usually from the chemicals used, impure anodes, additives, dissolution of substrates and photoresists during the plating process, etc. Organic impurities and metallic impurities can affect adhesion, produce pockmarks and pinholes, reduce dispersion and coverage ability, affect current efficiency and increase plating stress.

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