Physical Vapor Deposition (PVD)
What Is Physical Vapor Deposition (PVD)
Physical vapor deposition builds thin films atom by atom — sputtering, thermal and e-beam evaporation, cathodic arc, and ion plating — to coat tools, optics, decorative parts, glass, and electronics. Every one of these processes lives or dies on a clean, deep, repeatable vacuum. NAVAC’s HelixDrive dry screw pumps and BoostDrive roots blowers give coaters an oil-free primary vacuum with minimal maintenance, replacing both scroll pumps (dry, but seal-limited) and oil-sealed rotary vane pumps (wet, and a contamination risk to the film).
Why Vacuum Matters in Physical Vapor Deposition (PVD)
Deep Base Pressure
Chambers must reach roughly 10⁻⁵ to 10⁻⁷ Torr before deposition so residual gas doesn’t scatter the vapor flux or get trapped in the film. That base pressure is set by a high-vacuum pump — usually a turbomolecular pump, sometimes cryo or diffusion.
Contamination Control
Hydrocarbon oil backstreaming from a wet pump condenses on substrates and degrades adhesion, optical clarity, and film purity. A fully dry primary eliminates that risk at the source.
Gas and Particulate Handling
Sputtering runs a continuous argon (and often reactive N₂/O₂) flow at a few millitorr, and generates fine coating dust. The primary pump has to move that gas load continuously and tolerate particulates without wearing out.
Where HelixDrive and BoostDrive Fit in the Stack
A PVD system uses two vacuum stages. HelixDrive and BoostDrive are the primary (roughing and backing) stage — not the high-vacuum pump on the chamber. Positioned correctly, that is exactly the role scroll and rotary vane pumps fill today:
- Roughing. The dry primary pumps the chamber from atmosphere down to the high-vacuum pump’s crossover pressure (~10⁻² to 10⁻³ Torr).
- Backing. A turbomolecular pump can’t exhaust to atmosphere — it needs a backing pump holding its foreline well below ~1 Torr. HelixDrive’s 7.5×10⁻⁴ Torr ultimate sits comfortably below that.
- Boosting. Adding a BoostDrive roots blower ahead of the dry screw multiplies pumping speed at low pressure — cutting pump-down time and carrying higher sputter-gas throughput.
Why Go Dry: Replacing Scroll and Rotary Vane
The case for a dry screw primary comes down to contamination, wear parts, and uptime.
| Oil-sealed rotary vane (wet) | Scroll (dry) | HelixDrive screw (dry) | |
|---|---|---|---|
| Oil in the gas path | Yes — hydrocarbon backstreaming risk | No | No — oil only in sealed bearing (PFPE) |
| Ultimate pressure | ~10⁻³ Torr (two-stage) | ~10⁻² Torr typical | 7.5×10⁻⁴ Torr — matches or beats both |
| Wear parts | Vanes + oil | Tip seals — consumable, replaced periodically | No rubbing seals in the pumping chamber |
| Maintenance | Regular oil changes, mist filter, vane service | Tip-seal & bearing kits (typically ~yearly) | Minimal — long intervals, no tip seals or gas-path oil |
| Particulate / dust tolerance | Moderate | Poor — coating dust abrades tip seals | Good — robust to particulates |
| Contamination risk to film | High | Low | Low |
HelixDrive keeps the oil-free advantage of a scroll pump but removes the consumable tip seals and the dust-abrasion weakness, while reaching a lower ultimate pressure than either incumbent — with far less maintenance than a wet rotary vane.
HelixDrive Dry Screw — The Primary Pump
Ultra-compact, oil-free, coaxial dry screw with a proprietary rotor coating and gas-purge capability. Ultimate pressure across the line is 7.5×10⁻⁴ Torr (1.0×10⁻³ mbar) without gas ballast.
| Model | Pumping speed (60 Hz) | Ultimate pressure | Cooling | Inlet / Outlet | Weight |
|---|---|---|---|---|---|
| HD8 | 8 m³/h (5 CFM) | 7.5×10⁻⁴ Torr | Air | KF25 / KF16 | 84 lb |
| HD20 | 20 m³/h (12 CFM) | 7.5×10⁻⁴ Torr | Air | KF25 | 106 lb |
| HD40 | 32 m³/h (18.8 CFM) | 7.5×10⁻⁴ Torr | Air | KF25 | 106 lb |
| HD60 | 50 m³/h (29 CFM) | 7.5×10⁻⁴ Torr | Air | KF40 / KF25 | 159 lb |
| HD100 | 100 m³/h (60 CFM) | 7.5×10⁻⁴ Torr | Water | KF40 | 452 lb |
BoostDrive (BDi Series) Roots Blower — Add Speed
A compact, dry roots-style blower that mounts ahead of the HelixDrive (or another backing pump) to boost pumping speed at low pressure, shorten cycles, and improve ultimate vacuum. The BDi series has an integrated frequency converter, so the booster soft-starts and ramps up as chamber pressure falls — simplifying integration onto a roughing pump. Ultimate pressure is set by the backing pump; each BDi is rated for a 66 mbar (50 Torr) maximum permissible pressure differential.
| Model | Pumping speed (60 Hz) | Rec. backing pump | Inlet / Outlet | Motor | Weight |
|---|---|---|---|---|---|
| BD100i | 190 m³/h (112 CFM) | ED30 / DD48 | VG50 / VF50 | 0.37 kW | 51 lb |
| BD300i | 360 m³/h (212 CFM) | DD65 / DD90 | DN80 / DN80 | 0.37 kW | 60 lb |
| BD600i | 720 m³/h (424 CFM) | UD100 / DD90 | DN100 / DN63 | 1.5 kW | 218 lb |
| BD1200i | 1500 m³/h (1059 CFM) | UD300 | DN160 / DN100 | 3 kW | 470 lb |
Matching a Solution to the Coating Duty
| PVD duty | Suggested NAVAC setup |
|---|---|
| R&D coater, load-lock, or small chamber backing a turbopump | HD8–HD40 as the oil-free backing/roughing pump |
| Production sputter or evaporation chamber, standard cycle | HD40–HD100 sized to chamber volume and turbo foreline |
| Faster pump-down or higher reactive-sputter gas throughput | HelixDrive + BoostDrive BDi (BD100i–BD1200i) for boosted speed at low pressure |
Sizing depends on chamber volume, target cycle time, turbopump foreline requirement, and process-gas flow — our applications team can size the exact HD/BD pairing for a given coater.
Parts and Accessories
Genuine NAVAC components keep dry pumps running at spec: gas-purge and inlet fittings, filters, KF/DN connections, and the specified lubricants (PFPE bearing grease for HelixDrive, the specified gear-end oil for BoostDrive). Because the pumping chambers are dry, routine service is limited and intervals are long.
Contact NAVAC Today for PVD Solutions
NAVAC supplies oil-free primary vacuum engineered for the cleanliness, gas loads, and uptime demands of PVD coating. Contact us to size a HelixDrive or HelixDrive + BoostDrive package for your process.
