Arc evaporation

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Arc evaporation

Arc Evaporation

What is arc evaporation?
One form of physical vapour deposition (PVD coating) is arc evaporation. The history of PVD coating started using arc technology, which has its origin in arc welding.

Targets
The metal to be evaporated is placed as solid block (target) against the inside of a vacuum chamber. A glow discharge is ignited and runs on the target, leaving a footprint. Small spots of a few µm diameter target material are evaporated. The movement of the arc can be guided by magnets.

Plasma coating
The evaporated, ionized material is used as plasma coating on a product which rotates inside the vacuum chamber. Arc coatings are e.g. used as tool coating and component coating.

Examples of coatings
Examples of arc coating are TiN, AlTiN, AlCrN, TiSiN, TiCN, CrCN and CrN coating

Schematic view of a PVD arc process.

Arc coating technology is characterized by:

High deposition rates (~1-3 µm/h)
High ionisation, resulting in good adhesion and dense coatings
As the target is cooled, little heat to the substrate is generated, i.e. even coating at temperatures below 100°C is possible
Several compositions of metals can be evaporated, leaving the remaining solid target unchanged in its composition
The cathodes can be placed in any position (horizontal, vertical, upside down), which makes flexible machine design possible

The main disadvantages of arc coating technology are:

Limited kind of target materials - metals only (no oxides) - which do not have a too low evaporation temperature
Due to the high current densities some amount of the target material is ejected as small liquid droplets