ZIQUAL | Consistency · Precision · Speed
We manufacture UHV components with traceability built in. Every part ships with a QR-coded DNA — Digital Nameplate Archive: drawings, material certs, process notes, and cleaning/bake records tied to the exact machinist and machine. Reorders are literally a scan away.

Ultra-high vacuum (UHV) is unforgiving. The “wrong” alloy, a blind hole that traps air, a smear of cutting oil—any of these can push base pressure out of spec, contaminate optics, or turn pump-down into an all-day saga. This guide focuses on what actually matters in the shop and on your drawing so the parts you receive behave in UHV.

What counts as UHV—and what fails first

• UHV regime: typically < 10⁻⁹ mbar (≈10⁻⁹ Torr).
• Dominant gas loads: outgassing (surface + bulk) and permeation (through elastomers), not external leaks.
• Common failure modes: outgassing films, virtual leaks from trapped volumes (blind holes, double O-rings), poor weld geometry, and elastomer permeation.

Design, material choice, machining, cleaning, and bakeout all attack the same enemy: gas load.

Materials that actually work

Metals (default structural choices)

• Stainless steels: 304L and 316L are the workhorses. Low-carbon “L” grades weld cleanly and bake well.
  • Avoid 303/free-machining grades: sulfur/selenium additives outgas and contaminate.
• OFHC copper (C10100/C10200): gaskets and heat sinks; the standard for CF (ConFlat) all-metal seals.
• Aluminum 6061-T6: great for weight and machining ease; mind lower bake limits and creep; cleanliness is everything.
• Titanium (Grade 2/5): non-magnetic, strong, low outgassing; watch galling—spec compatible thread lubricant or coatings.

Ceramics & glasses

• Alumina, fused silica/quartz, sapphire: excellent for insulators, standoffs, viewports. Handle and clean like vacuum parts.

Polymers (use sparingly)

• PTFE, PEEK, Polyimide/Kapton, Vespel: acceptable in small, justified quantities with known ASTM E595 outgassing (TML/CVCM) and within bake limits. Pre-bake when possible.

Seals & flanges

• Use CF (ConFlat) with annealed OFHC copper gaskets for true UHV boundaries; bakeable, robust, and no permeation.
• Elastomer O-rings (e.g., Viton) are for access doors and non-UHV subsystems; they permeate and set a pressure floor.

Quick material & seal selection (cheat-table)

Design rules that prevent “invisible leaks”

• Vent every trapped volume. Blind-tapped holes, double O-ring grooves, and overlapping plates create virtual leaks. Prefer through-holes; otherwise add a 0.5–1.0 mm vent or use vented screws.
• Prefer all-metal seals for UHV boundaries; isolate elastomers away from the high-vacuum space if you must use them.
• Welds: specify full-penetration, continuous TIG on the vacuum side; no pockets or skip welds on UHV boundaries.
• Leak-rate targets: design and test toward ≤ 1×10⁻¹⁰ mbar·L/s (He-equiv) for UHV interfaces; modern detectors reach ~10⁻¹² mbar·L/s.

Machining for UHV: prints, tools, fluids, finishes

What to put on the drawing

• Material: “316L or 304L; free-machining grades (e.g., 303) not permitted.”
• Features: “All blind holes must be vented (Ø ≥ 0.5 mm) or converted to through-holes; add thread undercut/relief to vent roots.”
• Hardware: “Stainless only; no Zn/Cd plating. Use vented fasteners internally.”
• Finish (vacuum-wetted surfaces): Ra ≤ 1.6 µm (63 µin) pre-treatment; specify electropolish if you need lower outgassing or easier cleaning.
• Sealing surfaces: follow CF/ISO knife-edge specs; protect with caps after machining.
• Marking: avoid inks/dyes on vacuum surfaces; if needed, laser etch off-vacuum.

Process choices

• Cutting fluids: avoid sulfurized oils. Favor clean, water-soluble synthetics; flush liberally; clean immediately post-op.
• Deburr like it matters (it does). Burrs trap fluid and outgas. Break edges lightly; add vent-reliefs in deep threads.
• Surface treatment: Electropolishing reduces surface area and contaminants; avoid bead/sand blasting on vacuum-wetted surfaces unless process-controlled and followed by rigorous cleaning.

Fasteners & lubrication

• Use vented screws for internal threads.
• For high-load threads (e.g., CF studs), apply dry MoS₂ or PFPE (Krytox™) sparingly per spec to prevent galling.

Cleaning & bakeout that actually work

A practical recipe you can copy into your traveler:

1. Pre-clean: Alkaline detergent (e.g., Liquinox) + hot DI rinse. Repeat until water breaks cleanly.
2. Solvent clean: Acetone and/or IPA (reagent grade), then DI rinse; blow dry with filtered N₂.
3. Particulate control: Cleanroom wipes and gloves; bag between steps.
4. Bakeout: Assemble with only vacuum-approved materials; bake under vacuum.
   • Stainless systems: ~150–200 °C for 24–48 h (component limits govern).
   • Aluminum systems: lower bake temps; watch seals and viewport ratings.
5. Documentation: Record detergents, solvents, batch numbers, bake temps/times, and leak-check results.

Validation: helium leak testing

• Spec: aim for ≤ 1×10⁻¹⁰ mbar·L/s on UHV boundaries.
• Method: local spray while pumping; sniff external joints; monitor background stability; confirm after thermal cycles if applicable.
• Virtual-leak check: if the rate decays slowly rather than snapping to baseline, re-inspect for trapped volumes.

Common gotchas & anti-patterns

• Free-machining SS (303) anywhere near UHV.
• Zinc/cadmium-plated hardware in assemblies that see heat.
• Blind holes with no vents; thread roots with no relief.
• Media blasting that embeds grit into the surface.
• Elastomer O-rings at the main UHV boundary.
• “Shop clean” instead of vacuum clean (different standard!).

How Ziqual helps

• Traceability by default: Every part ships with a DNA QR linking the exact revision, material certs, cleaning/bake records, torque specs, and even vent-screw part numbers.
• Process discipline: UHV-safe coolants, controlled deburr, DI/solvent cleaning, bake, and leak testing on request.
• Speed without chaos: Need a fast turn? We can still keep the process clean—because we built for Consistency · Precision · Speed from day one.

Printable Checklist — UHV Material & Machining Prep

Print tip: In your browser’s print dialog, enable “Print backgrounds.” This page is designed to fit on one sheet.

1) Material & Seal Selection

• Structural metal is 304L or 316L (no 303 anywhere).
• OFHC copper gaskets specified for all CF seals.
• Any polymers are minimized and have known ASTM E595 outgassing data.
• Ceramics/glass (if used) are compatible with planned bake temperature.
• Elastomers isolated from the UHV boundary or justified in gas-load budget.

2) Design Against Virtual Leaks

• All blind holes converted to through-holes or vented (Ø ≥ 0.5–1.0 mm).
• Thread undercuts/reliefs added to vent thread roots.
• No double O-ring grooves or overlapping plates that trap volumes.
• Weld notes specify full-penetration continuous TIG on vacuum side.
• Leak-rate target on drawing: ≤ 1×10⁻¹⁰ mbar·L/s (He).

3) Machining Notes on the Print

• “316L/304L only; free-machining grades not permitted.”
• “Stainless hardware only; no Zn/Cd plating.”
• “Use vented fasteners internally.”
• Vacuum-wetted surfaces Ra ≤ 1.6 µm (63 µin) pre-treatment.
• Electropolish specified where lower outgassing/easier cleaning is required.
• Marking off vacuum surfaces (laser etch acceptable off-vacuum).

4) Process Controls

• No sulfurized oils; approved water-soluble synthetics only.
• Immediate cleaning after machining; no dried coolant films.
• Controlled deburr; no media embedding; edges broken lightly.
• Fastener lubrication: dry MoS₂ or PFPE where needed (sparingly).

5) Cleaning & Bake

• Alkaline detergent wash + hot DI rinse until water breaks cleanly.
• Solvent clean (acetone/IPA, reagent grade) + DI rinse; N₂ dry.
• Clean handling (wipes, gloves); bag between steps.
• Bake under vacuum (record temps/times):
  • Stainless: 150–200 °C for 24–48 h
  • Aluminum: lower temp per component limits
• Records kept for detergents, solvents, batch IDs, bake profile.

6) Inspection & Test

• Visual: knife-edges pristine; no scratches on sealing faces.
• Particulate: wipe test clean; no embedded media.
• Helium leak test passed at spec (≤ 1×10⁻¹⁰ mbar·L/s).
• Virtual-leak check performed (no slow decay).
• All ports capped and bagged clean.

7) Documentation to Attach (Ziqual DNA)

• Material certs (heat/lot)
• Process traveler (coolant, tools, deburr)
• Cleaning and bake logs (temps/times)
• Leak-test report (method, background, result)
• Torque specs and fastener callouts
• Final inspection photos

Have a tricky part or subsystem you’d like us to sanity-check? Send the model/drawing and we’ll mark up venting, finishes, and seal choices before a single chip is cut.