Title: Materials and Processes Division
1CONTAMINATION 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
2Introduction
- 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
3Part 1 Types of contamination
- Introduction
- Origin of Contaminants
- Requirements
- Verification of requirements
- Handling of contamination problems
4Introduction
- 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
5Types 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
6Requirements
- 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
7Requirements
8Requirements Fed-Std-209E
9Requirements ISO-14644_1
10Requirements ISO-14644_1
11Requirements Mil-Std-1246C
12Requirements Mil-Std-1246C
13Requirements Mil-Std-1246C
14Requirements
- 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.
15Requirements Mil-Std-1246C
16Verification 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
17Verification of requirements Micro VCM
18Verification of requirementsMicro VCM
19Verification of requirementsMicro VCM
20Verification 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
21Verification 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
22Verification of requirements
23Verification of requirements
24Verification of requirements
25Verification 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
26Verification 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
27Verification of requirementsPFO - meter
28Verification of requirements
- Particulate Contamination
- PFO meter and correlation with cleanliness
specifications table
29Verification 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
30Handling 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
31Handling 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?
32Part 2Cleaning Procedures
- Introduction
- Selection of Cleaning method
- Verification of cleaning efficiency
- Cleaning procedure
33Introduction
- 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
34Selection 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
35Cleaning 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
36Verification 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
37Cleaning 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
38Part 3Prevention
- Introduction
- Material selection
- Garment
- Potential risks
- Preventive actions
- Contamination control plan
39Introduction
- 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.
40Material selection
- Outgassing characteristics
- low TML and CVCM
- Mass of used material
- Location
- Optical applications
- Cryogenic
- High Temperature
- Long term predictions with VBQC
41VBQC
42VBQC
43VBQC
44VBQC
- 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.
45Garment
- 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
46Potential 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
47CONTAMINATION CONTROL PLAN
- Contamination control plan
- Preventive
- All requirements are mentioned
- Procedures for delicate handling or testing