CO2 Composite Spray Technology
for Probe Card Cleaning
David Jackson
Cool Clean Technologies
Contributors
Roger Caldwell, Vitesse Semiconductor
Andy Hoyle, Vitesse Semiconductor
Resistive Surface Contamination
• Metal Oxides (Sn, Pb, Al)
• Passivation
• Silicon Nitride
• Polymers (plasticizers/fibers)
• Lapping Compounds
• Adhesive Residues
• Outgas Compounds
• Metals (solder, Al)
• Human Contaminants
• Cleaning Residues
• Solder Flux
June 8 to 11, 2008
IEEE SW Test Workshop
2
Cleaning and Cleanliness Issues
Contamination tends to
bond/adhere in cohesive
layers…
Contaminations:
• A mix of transferred metals, organics,
inorganics, ionics and adsorbed films
• Thin and thick layers/films
Contact Surfaces:
• Surface area (contact zone) changes
over time
• Small/complex topography (curved,
pointed, crowned)
Contamination generates
more contamination.
June 8 to 11, 2008
Cleaning Processes:
• Incompatibilities (damage/efficacy)
• Variability/Quality
• Long cleaning times (manual methods)
IEEE SW Test Workshop
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Cleaning Methods (probe/socket)
Method
1.
2.
3.
4.
5.
6.
7.
8.
WC Plate
Lapping Films
Metal/Polymer Brush
Ceramic Block
Polymer Sheets
Microabrasive Spray
Camel Hair Brushing
IPA Wet Brushing
M
T
x
x
x
x
x
x
x
x
C
Manual
9 Direct Contact
9 Low Capital
9 High Labor
x
Automated
9. Weak Acid Cleaning
10. Ultrasonic Cleaning
11. Plasma Cleaning
M – Mechanical Energy
June 8 to 11, 2008
x
x
x
T – Thermal Energy
IEEE SW Test Workshop
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x
x
x 9 Non-Contact
9 High Capital
x 9 Low Labor
x
C - Chemical Energy
4
1
CL
E
June 8 to 11, 2008
AN
IN
G
EN
ER
GY
10
EA
L
C
NG
I
N
0
Applying excessive cleaning
energy is wasteful, may increase
cleaning time and/or may damage
surfaces.
12
Applying insufficient cleaning
energy increases cleaning time.
CONTAMINATION
Cleaning Process Challenge
0
E
M
I
T
9
Adapted from “Theory of Cleaning”, B.N.Ellis,
IEEE SW Test Workshop Circuit World, Vol.12 No.1, 1985
5
Cleaning Process Challenge
Cleaning Energy >= ∑Contaminant-Surface Adhesion Energies
Method 3
Method 8
Method 4
Method 1
Method 5
Method 10
June 8 to 11, 2008
Method 2
Method 9
Method 7
Best
Practice
Method 6
Combination of Optimal
Chemical-Mechanical
Effects
IEEE SW Test Workshop
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Cleaning Process Challenge
The most desirable cleaning process:
9 Non-destructive (contact surface/peripheral surfaces)
9 Minimal or no human contact
9 Robust (in terms of energy control)
9 Both mechanical and chemical cleaning actions
9 Ability to clean dense and complex surfaces
9 Fast (less cleaning labor/time)
9 Low cost-per-clean
9 Minimal or no cleaning agent by-products
9 Acceptable ROI
June 8 to 11, 2008
IEEE SW Test Workshop
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CO Cleaning Technology
2
CO2 technology has been used to produce consistently
clean surfaces for high-tech products such as spacecraft
devices, optical devices, sensors, lasers, disk drives, air
bags, medical devices and probe cards…
Treatment Schemes
• Composite CO2 Spray *
• Immersion Solvent (Liquid)
• Extraction Solvent (Supercritical)
• Atmospheric Plasma *
• Low Pressure Plasma
• UV-CO2 Treatment
• Plasma-CO2 *
Hybrid Processes
• Laser-CO2 *
• Microabrasive-CO2 *
* - Probe cleaning candidates
June 8 to 11, 2008
IEEE SW Test Workshop
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CO is Abundant
2
South Pole - Mars
A recycled by-product from
industrial and natural sources
such as refineries, CaCO3 wells,
and bakeries.
A recyclable and renewable
resource.
Major commercial uses include
beverage carbonation, fire
extinguishing and welding.
June 8 to 11, 2008
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CO is Safe
2
Solvent
Carbon Dioxide
Isopropyl Alcohol
Acetone
Trichloroethylene
1,1,1-Trichloroethane
n-Propyl Bromide
Ozone Depleting
Potential
(ODP)
None
~0
~0
~0
0.15
~0
OSHA
PEL
(ppm)
5,000
400
1000
50
350
100
VOC
No
Yes
No
Yes
Yes
Yes
CO2 is non-toxic, non-flammable and non-corrosive.
Recycled CO2 is exempt from the EPA Global
Warming legislation.
June 8 to 11, 2008
IEEE SW Test Workshop
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CO is Inexpensive
2
Solvent
Carbon Dioxide
Acetone
Isopropyl Alcohol
Methylene Chloride
1,1,1-Trichloroethane
n-Propyl Bromide
Bulk Price Range
$/kg
0.10 - 0.25
0.44 - 0.49
0.75 - 0.88
0.80 - 1.25
1.25 - 2.00
3.00 - 5.00
Just pennies of CO2 are used in composite spray
formulations for a cleaning operation…
June 8 to 11, 2008
IEEE SW Test Workshop
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CO Cleaning Agents
2
CLEANING
PROCESS
4
PHASE DIAGRAM
FOR CO2
SCF
73 ATM
SOLID
LIQUID
Immersion
2
PRESSURE
Spray
GAS
3
-80 C
5b
H.P.
PLASMA
5a
L.P.
PLASMA
1
1 ATM
June 8 to 11, 2008
Extraction
TEMPERATURE
32 C
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CO Solvent Properties
2
Carbon Dioxide
Acetone
Solid
Liquid
Supercritical
1.6
0.8
0.5
0.8
VISCOSITY
mN-s/m2
-
0.07
0.03
0.32
SURFACE
TENSION
dynes/cm
5-10
5
0
24
SOLUBILITY
MPa1/2
22
22
14
20
DENSITY
g/ml
June 8 to 11, 2008
IEEE SW Test Workshop
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Solid Carbon Dioxide
SEM
Photomicrograph
1 μm
June 8 to 11, 2008
• Structure - molecular crystal, angular,
octahedron
• Solvency – hydrocarbon-like, 22 MPa1/2
• Impact Phenomenon – ablation and
phase change (solid->gas, solid->liquid>gas)
• Chemistry – can be modified with
plasmas, liquids, solids, vapor-phase
additives
• Compressibility - incompressible
• Density - 1.6 g/cm3
• Hardness – 0.3 Hm (8 Hv)
• Particle Size – < 0.5 microns to > 500
microns, range adjustable (coarse/fine)
• Impact Stress - up to 60 MPa (8,700 psi)
IEEE SW Test Workshop
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Conventional Snow Cleaning
9 CO2 “snow” particles are too small and
can’t deliver the shear stress required to
dislodge resistive contaminants.
9 CO2 snow sprays are too dense and
cold (- 80 F), which tends to shield/freeze
surface contamination (“Igloo Effect”).
9 CO2 snow sprays discharge at a high
pressure (800+ psi) that can damage
structures at close proximity (needed for
cleaning effectiveness with small particles).
CO2 composite spray technology is better suited
to the contact cleaning task…Why ?
June 8 to 11, 2008
IEEE SW Test Workshop
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First…Variable Particle Size and Density
Adjustable compositions of lean (high freq. impacts) energetic CO2 particles
(size control) and heated propellant gas…at low spray pressures (10 -120
psi).
PARTICLE RANGE
(microns)
CO2 COMPOSITE SPRAY
CLEANING ENERGY
F=mx
COARSE
500
CO2 Composite Sprays
(0.01 - 60 MPa)
MEDIUM
100
FINE
10
∆v
∆t
Shaved Ice and
Pellets
(100 - 500 MPa)
Impact !
Control Parameters
CO2 Particle Size
CO2 Particle Density
Propellant Pressure
Propellant Temperature
Snow
Sprays
(0.01 - 2 MPa)
ULTRAFINE
1
0.1
1
10
60
IMPACT SHEAR STRESS
(MPa)
June 8 to 11, 2008
IEEE SW Test Workshop
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Second…Spray Composition Control
Additive(s)
Gas
(Chemical/ (Propulsion/
Physical)
Heating)
Chemical
Thermal
Mechanical
CO2
CO2 Spray Cleaning Parameters
Spray Pressure/Temp:
Cleaning Time/Distance:
Chemistry:
June 8 to 11, 2008
40 psi / 120 C
30 seconds / 1.5 inches
CDA, Fine CO2 Particles
IEEE SW Test Workshop
Particle Size
Chemistry
Spray Density
Temperature
Pressure
Distance/Angle
Time
17
Third…Process Enhancement Tool
CO2 composite sprays easily
adapt to and augment an
existing probe maintenance
program to increase overall
cleaning process efficiency and
effectiveness ….
Existing Cleaning and
Inspection Process
Composite sprays are additive without being
mechanically destructive (energy control)…
June 8 to 11, 2008
IEEE SW Test Workshop
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CO Composite Spray Technology
2
Hybrid
Coanda
Coaxial
• Capillary condensation for particle size control
• Micro-metered mass flow for precise spray density control
• Clean hot propellant gas for pressure and temperature control
• Coaxial and Coanda composite spray nozzles
• Chemical co-solvents easily employed
• Hybrid CO2 composite spray treatments - Microabrasives,
Laser, Atmospheric Plasma, Chemical Adjuncts, Brush
June 8 to 11, 2008
IEEE SW Test Workshop
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CO Composite Spray Technology
2
Lean Composite CO2 Sprays, used in cooperation.
June 8 to 11, 2008
IEEE SW Test Workshop
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CO Composite Spray Technology
2
SNOW SPRAYS (Conventional)
Convergent-Divergent
Nozzle
Liquid
CO2
FINE SOLIDS
ENTRAINED
IN COLD
HIGH
VELOCITY
CO2 GAS
COMPOSITE SPRAYS
Liquid
CO2
Coaxial or Coanda
Mixing Nozzle
Hot
CDA
Additive(s)
June 8 to 11, 2008
IEEE SW Test Workshop
SIZE-CONTROLLED
SOLIDS ENTRAINED
IN HEATED,
VELOCITYCONTROLLED
AIR
21
CO Composite Spray Technology
2
Mechanical and Tribo-Chemical Cleaning Actions
CO2 composite spray cleaning process
effectiveness and efficiency is controlled
by:
9 Particle velocity
9 Particle mass/size
9 Spray chemistry
9 Particle hardness (fine Æ coarse)
9 Particle shape (angular is better (stress conc.))
9 Impact frequency
9 Spray distance
9 Time
June 8 to 11, 2008
IEEE SW Test Workshop
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CO Composite Spray Technology
2
Peak Impact Stress v. Propellant Pressure
65
120 psi
Increasing propellant pressure and working closer to
the surface increases impact energy.
60
Impact Stress/MPa
55
50
206 kPa
45
414 kPa
483 kPa
40
621 kPa
35
827 kPa
30 psi
30
Coanda M
25
100 Deg. C (378 K)
20
0
5
10
15
20
25
30
35
Distance/cm
CO2 composite spray cleaning energy varies with pressure, temperature,
particle size and additive energy…
June 8 to 11, 2008
IEEE SW Test Workshop
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CO Composite Spray Technology
2
Surface Impact
Adjustable
Particle Size,Velocity,
and Spray Density
Lean sprays create
more energetic
impacts/time…
(2-Phase Flow)
CO2
AIR
Metal Oxides, Particles, Fibers,
Thin Films
75-300 m/s
DIRTY CONTACT SURFACE
June 8 to 11, 2008
IEEE SW Test Workshop
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CO Composite Spray Technology
2
Contamination Removal
Contaminants
Filtered from
Air
Scrubs complex
surfaces…
Mechanical Ablation
Chemical Solubility
CLEAN CONTACT SURFACE
June 8 to 11, 2008
IEEE SW Test Workshop
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CO Composite Spray Cleaning System
2
Several CO2 composite spray
cleaning methods and processes
under development for probe
cards (and test sockets)…
Manual – Automated - Hybrids
June 8 to 11, 2008
IEEE SW Test Workshop
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Cleaning Process Development
R&D System at customer site
June 8 to 11, 2008
IEEE SW Test Workshop
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Cleaning Process Development
Goal: Minimize or eliminate direct contact cleaning.
Clean-during-Inspection
CO2
Pretreatment
(no additives)
Manual
Mechanical
As little as
possible
As much as
possible
June 8 to 11, 2008
IEEE SW Test Workshop
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Cleaning Process Development
For a given spray cleaning
composition:
1. Scan rate
2. Distance
y
3. Spray angle
4. Time
x
z
June 8 to 11, 2008
IEEE SW Test Workshop
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Cleaning Process Development
What should be cleaned ?
Best Practice:
Contacts plus
Peripheral Surfaces
Contamination
migrates through
ES-Fields, thermal
gradients, physical
transfer modes…
Not cleaning the entire surface creates the
potential for cross-contamination…
June 8 to 11, 2008
IEEE SW Test Workshop
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Cleaning Process Development
Pre-Cleaning 1
Pre-Cleaning 2
CO2 Composite Spray Cleaning
Post Cleaning
70.0000
60.0000
Pad 90
(outlier)
50.0000
Ohms
40.0000
30
30.0000
20.0000
15 second
Spray Treatment
10.0000
1.5
0.0000
Pad
June 8 to 11, 2008
IEEE SW Test Workshop
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Cleaning Process Development
Pad Cres
5
Ohms
4
Cres Preclean 1
3
Cres Preclean 2
2
CO2 Composite Spray
1
0
1 7
June 8 to 11, 2008
82% reduction in pad
Cres failures/ 15 sec
13 19 25 31 37 43 49 55 61 67 73 79 85
spray treatment.
Contact Pad
33Æ6
Outlier data (Pad 90) removed from data set
IEEE SW Test Workshop
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Cleaning Process Development
Average Cres Reduction
2.0000
28% reduction/15 sec.
Cres Preclean 1
1.5000
Cres Preclean 2
Ohms 1.0000
15 second Spray
Treatment
0.5000
0.0000
Outlier data (Pad 90) removed from data set.
June 8 to 11, 2008
IEEE SW Test Workshop
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Cleaning Action
Before
After
Metal Oxides/Solder
Cleaning Spray Parameters:
Spray Pressure/Temp:
Cleaning Time/Distance:
Chemistry:
June 8 to 11, 2008
80 psi/120 C
1 minute/1 inch
CDA, Coarse CO2 Particles
IEEE SW Test Workshop
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Cleaning Action
Before
After
Aluminum/Al203
Cleaning Spray Parameters:
Spray Pressure/Temp:
Cleaning Time/Distance:
Chemistry:
June 8 to 11, 2008
70 psi/120 C
3 minutes/2 inches (robotic process)
CDA, Fine CO2 Particles
IEEE SW Test Workshop
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Cleaning Action
Metal Oxides
and Solder
Flux
Cleaning Spray Parameters:
Spray Pressure/Temp:
Cleaning Time/Distance:
Chemistry:
June 8 to 11, 2008
40 psi/120 C
30 seconds/1.5 inches
CDA, Fine CO2 Particles
IEEE SW Test Workshop
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Cleaning Cost Reduction
Existing Process:
• Easy to get lost under scope
• Surface contamination remains
in complex topography (crevices)
• Potential physical damage to
surfaces with brush
• Time intensive
June 8 to 11, 2008
IEEE SW Test Workshop
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Cleaning Cost Reduction
New Process:
In combination with CO2
pretreatment:
9 Significant reduction in
maintenance labor
9 Cleaner surfaces…faster
9 Much less direct contact
9 Much less physical damage
June 8 to 11, 2008
IEEE SW Test Workshop
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Wrap-up
• Composite CO2 sprays are fully adjustable
and provide quick, clean, and nondestructive contact cleaning.
• Worker- and equipment-safe cleaning process.
• Adaptable to existing cleaning processes.
Minimizes manual cleaning, potential to replace
mechanical contact treatments.
• Low cost-per-clean with a significant contact
maintenance labor (time) reduction potential.
June 8 to 11, 2008
IEEE SW Test Workshop
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Questions ?
For more information:
David Jackson
david.jackson@coolclean.com
661-803-0546
http://www.purco2.com
June 8 to 11, 2008
IEEE SW Test Workshop
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