L–Cleaning Components After Manufacturing

In particular when used in UHV environments or optics setups

Initial Inspection

• Reasoning: Identify and assess contaminants or damages before cleaning.

• Importance: The knife edges of ConFlat (CF) flanges are precision-engineered sealing surfaces crucial for maintaining ultra-high vacuum (UHV) conditions. Any damage or contamination to these knife edges can compromise the integrity of the seal, leading to vacuum leaks and system failures. More on this, e.g.: https://www.rbdinstruments.com/blog/protect-the-cf-flange-knife-edge/ and https://de.lesker.com/newweb/flanges/flanges_technicalnotes_conflat_1.cfm

Mechanical Cleaning

• For Stainless Steel, Aluminum, Titanium, Copper, Ceramics (Alumina):

  • Use a clean, lint-free cloth or brush, such as Kimtech Science Precision Wipes (model number 75512) or Premium Optical Cleaning Tissues from Thorlabs.

  • Reasoning: Remove gross contaminants without leaving residues. Kimtech Science Precision Wipes are low-lint and suitable for precision cleaning, making them appropriate for some of the work in UHV component cleaning where lint-free materials are needed.

• For PEEK, Kapton, Electrical Wires with Insulation:

  • Use a soft brush with gentle strokes.

  • Reasoning: Prevent surface damage on sensitive materials.

Ultrasonic Cleaning with Detergent Solution

• Mixture Level: Prepare a 5% (by weight) alkaline detergent solution (e.g., Tickopur RW77) in deionized water.

• For Stainless Steel, Aluminum, Titanium, Ceramics (Alumina):

  • Set ultrasonic bath temperature to 20–80°C.

  • Immerse components for 10–30 minutes.

  • Reasoning: Effectively remove oils and greases.

• For PEEK, Kapton, Electrical Wires with Insulation:

  • Set temperature to 30–40°C to minimize thermal stress.

  • Limit ultrasonic exposure to 5–15 minutes.

  • Reasoning: Prevent heat and vibration damage due to material sensitivity.

Rinsing with Deionized Water

• Rinse all components thoroughly.

• Reasoning: Eliminate detergent residues that could outgas.

Oxide Removal (Pickling) for Copper

Reasoning: Copper surfaces often develop oxides that can hinder UHV performance. Removing these oxides is crucial.

Acid Bath Preparation

• Option 1: Citric Acid Solution

Mixture Ratio: Dissolve 50 grams of citric acid powder in 950 mL of deionized water to make a 5% solution.

• Option 2: Acetic Acid (Vinegar) Solution

Use household white vinegar, which is typically a 5% acetic acid solution. No dilution necessary unless higher purity is required.

• Option 3: Sulfuric Acid Solution (For Tough Oxides)

Mixture Ratio: Carefully add 100 mL of concentrated sulfuric acid (approx. 98%) to 900 mL of deionized water to make a 10% sulfuric acid solution.

Procedure

1. Immersion:

• Submerge the copper components in the prepared acid solution for 5–10 minutes.

• Gently agitate the solution to enhance oxide removal.

2. Monitoring:

• Observe the components closely to prevent over-etching.

• Remove the parts once the oxides have dissolved.

Safety Precautions

• Wear appropriate PPE: acid-resistant gloves, safety goggles, and a lab coat.

• Conduct the process in a well-ventilated area or under a fume hood.

• Always add acid to water, never water to acid, to prevent exothermic reactions.

• Have neutralizing agents (like baking soda solution) readily available in case of spills.

Neutralization and Rinsing

1. Neutralization:

• Immerse the treated components in a baking soda solution prepared by dissolving 50 grams of sodium bicarbonate in 950 mL of deionized water.

• Soak for 5 minutes to neutralize residual acid.

2. Rinsing:

• Rinse thoroughly with deionized water.

• Perform multiple rinses to ensure complete removal of residues.

Ultrasonic Cleaning with Two Solvent Solutions

• Mixture Levels and Quality:

  • First Bath: 100% acetone (analytical grade – 99.5% or higher purity).

  • Second Bath: 100% ethanol or isopropanol (analytical grade – 99.5% or higher purity).

• For Stainless Steel, Aluminum, Titanium, Copper, Ceramics (Alumina):

  • Immerse components in acetone bath with ultrasonic agitation for 10–15 minutes.

  • Transfer immediately to ethanol or isopropanol bath with ultrasonic agitation for another 10–15 minutes.

  • Reasoning: Sequential solvent cleaning dissolves and removes a wide range of organic contaminants.

• For PEEK, Kapton, Electrical Wires with Insulation:

  • Important: Do not use acetone.

  • Immerse only in ethanol or isopropanol bath with ultrasonic agitation for 10–15 minutes.

  • Reasoning: Acetone can degrade these materials; ethanol or isopropanol is safer.

Drying

• Use filtered compressed air or nitrogen to dry components thoroughly.

• Reasoning: Prevent solvent residues and avoid introducing new contaminants.

• Note for Sensitive Materials (PEEK, Kapton):

  • Use ambient air drying or gentle warming (not exceeding 40°C).

  • Reasoning: Avoid high temperatures that could cause damage.

Bake-Out (Optional)

• For Stainless Steel, Titanium, Ceramics (Alumina):

  • Bake in an oven at 100–200°C for several hours (typically 2–4 hours).

  • Reasoning: Remove absorbed gases and moisture for ultra-high vacuum readiness.

• For PEEK, Kapton, Electrical Wires with Insulation, Aluminum:

  • Bake at lower temperatures (50–80°C) for several hours.

  • Reasoning: Prevent material degradation due to high temperatures.

Wiping (Optional)

• Use a clean, lint-free cloth, such as Kimtech Science Precision Wipes (model number 75512) or Premium Optical Cleaning Tissues from Thorlabs together with isopropanol for optional mechanical cleaning.

Final Inspection

• Visually inspect all components for cleanliness and any signs of residue or damage.

• Reasoning: Ensure they meet UHV standards before assembly or use.

Packaging

• Wrap components individually in clean, lint-free materials (e.g., cleanroom-grade bags or aluminum foil).

• Store in a clean, dust-free environment until assembly.

• Reasoning: Maintain cleanliness and prevent re-contamination during storage.

Additional Tips

• Avoid Abrasives on Copper:

Do not use abrasive materials or scouring pads on copper surfaces, as they can introduce scratches and contamination.

• Safety First:

When working with acids and solvents, always follow safety protocols, including proper PPE and working in well-ventilated areas or fume hoods.

• Regular Maintenance:

Implement a routine cleaning schedule for components that are frequently exposed to air or contaminants.

• Minimize Air Exposure:

Especially for copper, reduce the time between cleaning and installation to prevent oxidation.

---

Note on Cleaning Tools for Assembling UHV Components

When preparing tools for the assembly of ultra-high vacuum (UHV) components, it is essential to ensure that they are free from contaminants that could compromise the vacuum environment. Proper cleaning minimizes the risk of transferring oils, greases, particles, or other impurities to the components during assembly. However, it is crucial not to remove functional grease from the tools, as it is necessary for their proper operation.

Initial Inspection:

• Examine tools for visible contaminants such as dirt, dust, or residues.

• Identify areas requiring special attention without disassembling the tools.

Mechanical Cleaning:

• Wipe down the tool surfaces with a clean, lint-free cloth (e.g., Kimtech Science Precision Wipes).

• Use soft brushes to clean crevices, avoiding dislodging or removing grease from moving parts.

Solvent Wiping:

• Moisten a lint-free wipe with high-purity isopropanol or ethanol (analytical grade).

• Gently wipe the external surfaces of the tools.

• Avoid soaking or immersing tools to prevent solvents from penetrating areas with functional grease.

Preserving Functional Grease:

• Do not clean internal mechanisms or moving parts where grease is present.

• Reasoning: Functional grease ensures smooth operation and longevity of the tools; removing it can cause wear or failure.

Tool Materials and Greased Tools:

• Avoid using tools with plastic handles or parts, as these can be difficult to clean properly.

• Reasoning: Tools with plastic or greased components may introduce contaminants if not cleaned adequately, which can compromise UHV conditions.

Drying:

• Allow tools to air dry in a clean environment.

• Alternatively, use filtered compressed air or nitrogen to blow-dry surfaces, taking care not to disturb greased areas.

Final Inspection:

• Check tools for any remaining residues or contaminants.

• Ensure that all solvent has evaporated before use.

Glove Protocol:

• Wear clean, powder-free gloves when handling cleaned tools.

• Reasoning: Prevents skin oils and particles from contaminating the tools after cleaning.

Storage:

• Store tools in a clean, dry area, preferably in cleanroom-grade bags or containers.

• Reasoning: Maintains cleanliness until the tools are used for assembly.

Additional Considerations:

• Dedicated Tool Set:

  • Use a set of tools exclusively for UHV assembly.

  • Reasoning: Reduces the risk of cross-contamination from other activities.

• Regular Maintenance:

  • Periodically inspect tools for wear and reapply functional grease as needed.

  • Use vacuum-compatible greases if reapplication is necessary.

• Avoid Contaminant Introduction:

  • Do not touch cleaned tool surfaces with bare hands.

  • Keep tools away from sources of contaminants such as dust, aerosols, or chemical vapors.

Summary:

Properly cleaned tools are vital for maintaining the integrity of UHV components during assembly. By following careful cleaning procedures and preserving functional grease, you ensure both the cleanliness required for UHV conditions and the operational effectiveness of your tools. Tools with plastic handles or greased parts should be avoided for UHV work, as they can be difficult to clean effectively.