Materials and Processes Division

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CONTAMINATION CONTROL

• SME-Course
• D Materials
• Materials and Processes Division
• Materials Physics and Chemistry Section
• Jaco M. Guyt TOS-QMC
• Topics
• 1 Types of contamination
• 2 Cleaning procedures
• 3 Prevention

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Introduction

• Why contamination control ?
• Satellites are operational in orbit - no
  maintenance after launch
• Sophisticated equipment with higher demands on
  performance
• Increased mission duration
• Increased reliability is needed

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Part 1 Types of contamination

• Introduction
• Origin of Contaminants
• Requirements
• Verification of requirements
• Handling of contamination problems

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Introduction

• Definition
• Any foreign matter
• Unwanted deposition on surfaces.
• Contamination effects
• On thermal control surfaces - changes ? and ?
  ratios
• On solar arrays - decrease on power output
• On optical instruments - decrease signal /
  scattering
• In waveguides - Multipaction

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Types of contamination

• Organic and Inorganic contamination coming from
• Humans - Skin, handling greases/salts, hair,
  cosmetics
• Clothing - Fibres, dust collected in clothing
• Materials - Outgassing, solvent extraction,
  creeping(oil
• greases), direct contact, degradation
• Vacuum test - Pump oils, chamber history,
  turbulence at
• start, venting (lines and gas quality)
• Machining - Drilling, abrasion, polishing,
  cleaning
• Transport - Packaging, pressure drop in plane
• Space - Pyro-valves, wire cutters, thrusters
• Exposure C. R.- Working activities, soldering,
  air circulation

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Requirements

• Inorganic / Particulate contamination
• Airborne
• Fed-Std-209 - Airborne Particulate Cleanliness
  Classes in Cleanrooms and Clean Zones
• ISO-14644-1 (1999) -
• Cleanrooms and associated controlled
  environments
• PSS-01-201 / ECSS Q-70-01 -
• Cleanliness and Contamination control
• Surface contamination
• Mil-Std-1246C - Product Cleanliness levels and
  Contamination control program
• PSS-01-201 / ECSS Q-70-01

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Requirements
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Requirements Fed-Std-209E
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Requirements ISO-14644_1
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Requirements ISO-14644_1
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Requirements Mil-Std-1246C
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Requirements Mil-Std-1246C
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Requirements Mil-Std-1246C
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Requirements

• Organic Contamination
• PSS-01-201 / ECSS Q-70-01
• exposure in clean room during a continuous period
  of one week, less than 2.0x10-7 g/cm2
• Exposure in vacuum chamber after a blank test of
  24 hours, less than 1.0x10-7 g/cm2
• Project depending, more stringent levels.
• PSS-01-702 / ECSS Q-70-02A
• Outgassing requirements of materials.
• Mil-Std-1246C
• Level A/100 till F ,
• which is 0.01mg/0.1m2 up to 25 mg/0.1 m2.

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Requirements Mil-Std-1246C
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Verification of requirements

• Organic Contamination
• Visual inspection - levels unto 10-6 g/cm2 range
• ECSS-Q-70-02 (old PSS-01-702) Thermal vacuum
  outgassing test for the screening of space
  materials
• PSS-01-705 (ECSS-Q-70-05) The detection of
  organic contamination of surfaces by infrared
  spectroscopy
• ASTM E1235 Gravimetric Determination of
  Nonvolatile Residue (NVR) in Environmentally
  Controlled Areas for Spacecraft
• ESTEC work instructions contact and immersion
  test

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Verification of requirements Micro VCM
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Verification of requirementsMicro VCM
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Verification of requirementsMicro VCM
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Verification of requirements

• Acceptance limits PSS-01-702 TML lt 1.0, CVCM lt
  0.1
• Acceptance limits ECSS-Q-70-02A RML lt 1.0,
  CVCM lt 0.1
• Micro VCM results
• TML RML CVCM WVR Remarks
• A - 1.12 0.05 0.01 1.07 Too high water
• B - 0.56 0.45 0.23 0.11 Too high CVCM
• C - 2.15 1.01 0.09 1.14 Too high TML/RML
• D - 9.52 9.50 6.17 0.02 Too high RML/CVCM

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Verification of requirements

• PSS-01-705 (ECSS-Q-70-05) The detection of
  organic contamination of surfaces by infrared
  spectroscopy
• Identification due to specific absorption of the
  molecule due to vibrations and rotations of atoms
• Quantification by Lambert/Beers Law relation
• Abs. E b C
• E Molar Absorption Coefficient
• b Pathlength
• C Concentration
• Calibration curves for four standards
• Paraffin, Di-octylPhthalate ester, Methylsilicone
  and MethylPhenylsilicone

Abs.
Absorption of sample
Concentration of sample
Concentration
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Verification of requirements
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Verification of requirements
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Verification of requirements
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Verification of requirements

• Sampling for infrared analysis
• Indirect by rinsing surface with solvent and
  analyse of NVR
• Indirect by wiping surface with tissue and
  analyse of NVR
• Direct by using infrared transparent windows
  ZnSe, CaF2

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Verification of requirements

• Particulate Contamination
• Airborne Counters - Fed Std 209E
• Surface contamination
• Visual inspection, less than 300 ppm
• ECSS-Q-70-50, Particle Fall Out measurement
• ASTM E1216, Tape lift method
• ASTM F312, Counting and sizing particles
• ASTM F311, Liquid samples

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Verification of requirementsPFO - meter
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Verification of requirements

• Particulate Contamination
• PFO meter and correlation with cleanliness
  specifications table

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Verification of requirements

• Tape lift method as performed at ESTEC
• Define area which needs to be checked
• Take Polyethylene transparent tape from 3M
  Scotch 480
• Stick it on a surface of at least 5 x 5 cm
• Take with tweezers the 0.45 micron filter paper
  with grid
• Apply the filter paper against the just released
  tape
• Cut excessive tape away
• Count particles by Microscope in different size
  ranges

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Handling of contamination problems

• Define problem and location
• Define starting point of problem
• Write Non Conformance Report (NCR)
• Identification of contamination by analysis
• Search for possible sources
• on location
• Detailed Material Lists
• Excluding by analysis / search / calculation

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Handling of contamination problems

• Can the problem be solved?
• Can we live with it?
• Will it happen again?
• Can we avoid the risk by preventive actions or
  adjusting procedures?

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Part 2Cleaning Procedures

• Introduction
• Selection of Cleaning method
• Verification of cleaning efficiency
• Cleaning procedure

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Introduction

• Definition of clean
• A contamination level below the acceptance limits
  or not detectable with the used method.
• Procedure for cleaning is needed for
• Customer - that you are cleaning and how
• Personnel - that they know how to clean and what
• Sub-contractor - that they know how and what are
  the requirements

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Selection of Cleaning method

• Selection should be based on
• Method compatibility with hardware
• ultrasonic, temperature, mechanical scratching
• Method efficiency with hardware
• accessibility design
• Solvent compatibility with hardware
• corrosion, chemical attack, dissolving, removable
• Solvent efficiency for contaminant
• what are you removing, polar/non-polar

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Cleaning methods

• Mechanical cleaning - grinding, brushing,
  blasting
• Detergent cleaning or soap cleaning
• Solvent bath / ultrasonic
• Chemical cleaning - acids, alkalines and salts
• Vacuum bake out
• Vacuum cleaner / ionised air
• Plasma cleaning
• Dry ice
• Polymer film
• Adhesive

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Verification of cleaning efficiency

• By representative test samples and checked
  visually or by analysis
• Visual inspection after cleaning
• Check of hardware by taking samples, followed by
  analysis
• Check performance of hardware and verify against
  previous tests

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Cleaning procedure

• Should contain description or information about
• Hardware
• Method, with details about e.g. solvents/duration
  and flow chart
• Restrictions or hazards for hardware or personnel
• Requirements
• Verification of requirements
• Inspection after cleaning
• Operators (trained)
• Logbook entry

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Part 3Prevention

• Introduction
• Material selection
• Garment
• Potential risks
• Preventive actions
• Contamination control plan

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Introduction

• Prevention is better and cheaper then the cure!!
• Think ahead.
• If you are not sure it will contaminate the
  hardware? Stop the activity! Because the answer
  is yes.
• If something can go wrong, it will go wrong.
• Working towards a dead-line is where prevention
  looses its power.

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Material selection

• Outgassing characteristics
• low TML and CVCM
• Mass of used material
• Location
• Optical applications
• Cryogenic
• High Temperature
• Long term predictions with VBQC

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VBQC
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VBQC
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VBQC
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VBQC

• Results taken out of the Mathematical treatment
  consist of Accelaration factor, Activation
  energy, Residence time - Temperature dependency.
• Long term predictions with VBQC data is used
  within the temperature range of test.
• The TML or CVCM data are fitted period by period
  with a sum of 6 exponential equations.
• With W0.i the variables, affected with the time
  constant ?0,i, which are 50, 20, 5, 1, 0.5 and
  0.1 hour.

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Garment

• As humans are the main source of contamination,
  garment should be taken into account from the
  beginning of the project.
• Depending of the contamination budget allocated
  to a specific operation, selection of garment can
  be done
• Storage of garment should be separate from street
  clothing
• Procedure of dressing should be trained to the
  personnel
• Regular cleaning of garment by specialised
  company / quality check

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Potential risks

• Potential risks Preventive actions
• Thermal vacuum tests Check procedure
• Pumping oils Blank test
• Outgassing of materials Check DML
• Solar radiation Adequate thermal protection
• Clean room operations Training of personnel
• Too many personnel in C.R. Entry form
• Unauthorised entry in C.R. Access code for CR /
  locked
• Maintenance in C.R. Check impact, protect items
• Violation of dress code Clear signs on
  doors,training
• Dirty activity during AIT Separate from
  sensitive item

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CONTAMINATION CONTROL PLAN

• Contamination control plan
• Preventive
• All requirements are mentioned
• Procedures for delicate handling or testing