SME initiative
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
Materials and Processes Division
ESA-ESTEC TOS/QM
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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
Materials and Processes Division
ESA-ESTEC TOS/QM
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Part 1
Types of contamination
– Introduction
– Origin of Contaminants
– Requirements
– Verification of requirements
– Handling of contamination problems
Materials and Processes Division
ESA-ESTEC TOS/QM
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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
Materials and Processes Division
ESA-ESTEC TOS/QM
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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
Materials and Processes Division
ESA-ESTEC TOS/QM
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Requirements
• Inorganic / Particulate contamination
– Airborne
• ISO-14644-1 (1999) – superseded FED-Std-209)
“ Cleanrooms and associated controlled environments”
• PSS-01-201 / ECSS Q-70-01 “Cleanliness and Contamination control”
– Surface contamination
• IEST-Std-CC1246D - “Product Cleanliness levels and
Contamination control program” superseded Mil-Std-1246C
• PSS-01-201 / ECSS Q-70-01
Materials and Processes Division
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Requirements
Materials and Processes Division
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Requirements Fed-Std-209E
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Requirements ISO-14644_1
Materials and Processes Division
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Requirements ISO-14644_1
Materials and Processes Division
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Requirements Mil-Std-1246C
Materials and Processes Division
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Requirements Mil-Std-1246C
Materials and Processes Division
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Requirements Mil-Std-1246C
Materials and Processes Division
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Requirements IEST-STD-CC1246D
Materials and Processes Division
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Requirements IEST-STD-CC1246D
Materials and Processes Division
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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.
– ECSS Q-70-02A
• Outgassing requirements of materials.
– IEST-Std-CC1246D
• Level AA5 up to level J, what is 10 ng till 25 mg per 0.1m2
Materials and Processes Division
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Requirements Mil-Std-1246C
Materials and Processes Division
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Requirements IEST-STD-CC1246D
Materials and Processes Division
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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
Materials and Processes Division
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Verification of requirements
Micro VCM
Materials and Processes Division
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Verification of requirements
Micro VCM
Materials and Processes Division
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Verification of requirements
Micro VCM
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Verification of requirements
• Acceptance limits PSS-01-702 : TML < 1.0%, CVCM < 0.1%
• Acceptance limits ECSS-Q-70-02A : RML < 1.0%, CVCM < 0.1%
• Micro VCM results
TML RML
A - 1.12% 0.05%
B - 0.56% 0.45%
C - 2.15% 1.01%
D - 9.52% 9.50%
CVCM
0.01%
0.23%
0.09%
6.17%
WVR
1.07%
0.11%
1.14%
0.02%
Materials and Processes Division
ESA-ESTEC TOS/QM
Remarks
Too high water
Too high CVCM
Too high TML/RML
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.
Abs. = E * b * C
Absorption of sample
E = Molar Absorption Coefficient
Concentration
of sample
b = Pathlength
C = Concentration
Concentration
– Calibration curves for four standards
• Paraffin, Di-octylPhthalate ester, Methylsilicone and
MethylPhenylsilicone
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Verification of requirements
Materials and Processes Division
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Verification of requirements
Materials and Processes Division
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Verification of requirements
Materials and Processes Division
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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
Materials and Processes Division
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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
Materials and Processes Division
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Verification of requirements
PFO - meter
Materials and Processes Division
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Verification of requirements
• Particulate Contamination
– PFO meter and correlation with cleanliness specifications table
Materials and Processes Division
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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
Materials and Processes Division
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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?
Materials and Processes Division
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Part 2
Cleaning Procedures
• Introduction
• Selection of Cleaning method
• Verification of cleaning efficiency
• Cleaning procedure
Materials and Processes Division
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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
Materials and Processes Division
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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 3
Prevention
• Introduction
• Material selection
• Garment
• Potential risks
• Preventive actions
• Contamination control plan
Materials and Processes Division
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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
Materials and Processes Division
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VBQC
VBQC SYSTEM
Heating system
Cooling system
Measuring devices
Vacuum balance
TS2
TS5
TS1
TS7
QCM
plate
TS8
QCM plate
cooling
Reference
mass
Sample
Heater plate
TS6
Condensor
plate cooling
Pumping
system
Materials and Processes Division
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Shroud
heater
Shroud
cooling
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VBQC
O ut gas sin g an d
sam ple t em pe ra tur e pro file
1
150
T M L (% )
0.8333333333
TML (% )
100
0 .5
Tem per ature (ºC)
0.6666666667
50
0.3333333333
0.1666666667
T e m p e r a tu re
0
0
0
24
48
72
96
120
T i m e ( h)
Materials and Processes Division
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VBQC
C VC M pr ofile
0 .2 5
C V C M a t -2 5 ºC
C V C M a t -5 0 ºC
C V C M a t -7 5 ºC
C VC M (% )
0.2
0 .1 5
0.1
0 .0 5
0
0
24
48
72
T i m e ( h)
Materials and Processes Division
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120
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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.
6
t

W  W0,i  1  e

i 1
 0 ,i



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
• Thermal vacuum tests
– Pumping oils
– Outgassing of materials
– Solar radiation
• Clean room operations
– Too many personnel in C.R.
– Unauthorised entry in C.R.
– Maintenance in C.R.
– Violation of dress code
– Dirty activity during AIT
Materials and Processes Division
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Preventive actions
Check procedure
Blank test
Check DML
Adequate thermal protection
Training of personnel
Entry form
Access code for CR / locked
Check impact, protect items
Clear signs on doors,training
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
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