CO2 Composite Spray Technology for Probe Card Cleaning David Jackson Cool Clean Technologies Contributors Roger Caldwell, Vitesse Semiconductor Andy Hoyle, Vitesse Semiconductor ResistiveResistive SurfaceSurface ContaminationContamination • 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 CleaningCleaning andand CleanlinessCleanliness IssuesIssues Contamination tends to Contaminations: bond/adhere in cohesive • A mix of transferred metals, organics, layers… 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) Cleaning Processes: • Incompatibilities (damage/efficacy) Contamination generates • Variability/Quality more contamination. • Long cleaning times (manual methods) June 8 to 11, 2008 IEEE SW Test Workshop 3 CleaningCleaning MethodsMethods (probe/socket)(probe/socket) Method M T C Manual 1. WC Plate x 9 Direct Contact 9 Low Capital 2. Lapping Films x 9 High Labor 3. Metal/Polymer Brush x 4. Ceramic Block x 5. Polymer Sheets x 6. Microabrasive Spray x 7. Camel Hair Brushing x 8. IPA Wet Brushing x x Automated 9. Weak Acid Cleaning x x x 9 Non-Contact 9 High Capital 10. Ultrasonic Cleaning x x x 9 Low Labor 11. Plasma Cleaning x x x M – Mechanical Energy T – Thermal Energy C - Chemical Energy June 8 to 11, 2008 IEEE SW Test Workshop 4 2 1 CONTAMINATION 0 0 Applying insufficient cleaning E 5 M energy increases cleaning time. I T CleaningCleaning ProcessProcess ChallengeChallenge G N Applying excessive cleaning I surfaces. N A E energy is wasteful, may increase L C cleaning time and/or may damage Adapted from “Theory of Cleaning”, B.N.Ellis, Circuit World, Vol.12 No.1, 1985 9 1 10 CLEANING ENERGY IEEE SW Test Workshop June 8 to 11, 2008 CleaningCleaning ProcessProcess ChallengeChallenge Cleaning Energy >= ∑Contaminant-Surface Adhesion Energies Method 3 Method 4 Method 8 Method 1 Method 5 Method 9 Method 10 Method 2 Method 7 Method 6 Best Practice Combination of Optimal June 8 to 11, 2008 Chemical-MechanicalIEEE SW Test Workshop Effects 6 CleaningCleaning ProcessProcess ChallengeChallenge 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 7 COCO2 CleaningCleaning TechnologyTechnology 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 2 • Laser-CO * • Microabrasive-CO2 * * - Probe cleaning candidates June 8 to 11, 2008 IEEE SW Test Workshop 8 COCO2 isis AbundantAbundant 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 IEEE SW Test Workshop 9 COCO2 isis SafeSafe Ozone Depleting OSHA Solvent Potential PEL VOC (ODP) (ppm) Carbon Dioxide None 5,000 No Isopropyl Alcohol ~0 400 Yes Acetone ~0 1000 No Trichloroethylene ~0 50 Yes 1,1,1-Trichloroethane 0.15 350 Yes n-Propyl Bromide ~0 100 Yes CO2 is non-toxic, non-flammable and non-corrosive. 2 Recycled CO is exempt from the EPA Global Warming legislation. June 8 to 11, 2008 IEEE SW Test Workshop 10 COCO2 isis InexpensiveInexpensive Bulk Price Range Solvent $/kg Carbon Dioxide 0.10 - 0.25 Acetone 0.44 - 0.49 Isopropyl Alcohol 0.75 - 0.88 Methylene Chloride 0.80 - 1.25 1,1,1-Trichloroethane 1.25 - 2.00 n-Propyl Bromide 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 11 COCO2 CleaningCleaning AgentsAgents CLEANING PROCESS 4 Extraction PHASE DIAGRAM FOR CO2 SCF Immersion 73 ATM SOLID LIQUID 2 Spray GAS H.P. PRESSURE 5b 3 PLASMA 1 1 ATM L.P. 5a PLASMA -80 C TEMPERATURE 32 C June 8 to 11, 2008 IEEE SW Test Workshop 12 COCO2 SolventSolvent PropertiesProperties Carbon Dioxide Acetone DENSITY Solid Liquid Supercritical g/ml 1.6 0.8 0.5 0.8 VISCOSITY - 0.07 0.03 0.32 mN-s/m2 SURFACE TENSION 5-10 5 0 24 dynes/cm SOLUBILITY 22 22 14 20 MPa1/2 June 8 to 11, 2008 IEEE SW Test Workshop 13 SolidSolid CarbonCarbon DioxideDioxide SEM Photomicrograph • 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 1 μm plasmas, liquids, solids, vapor-phase additives • Compressibility - incompressible 3 • Density - 1.6 g/cm • 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) June 8 to 11, 2008 IEEE SW Test Workshop 14 ConventionalConventional SnowSnow CleaningCleaning 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 15 FirstFirst……VariableVariable ParticleParticle SizeSize andand DensityDensity Adjustable compositions of lean (high freq. impacts) energetic CO2 particles (size control) and heated propellant gas…at low spray pressures (10 -120 psi). CO2 COMPOSITE SPRAY CLEANING ENERGY ∆v Shaved Ice and F = m x Pellets ∆t (100 - 500 MPa) COARSE CO2 Composite Sprays Impact ! 500 (0.01 - 60 MPa) MEDIUM Control Parameters 100 CO2 Particle Size CO2 Particle Density FINE Propellant Pressure (microns) Snow Propellant Temperature 10 Sprays (0.01 - 2 MPa) PARTICLE RANGE ULTRAFINE 1 0.1 1 10 60 IMPACT SHEAR STRESS (MPa) June 8 to 11, 2008 IEEE SW Test Workshop 16 SecondSecond……SpraySpray CompositionComposition ControlControl Additive(s) Gas (Chemical/ (Propulsion/ Physical) Heating) Chemical Thermal Mechanical Particle Size Chemistry CO2 Spray Density Temperature CO2 Spray Cleaning Parameters Pressure Spray Pressure/Temp: 40 psi / 120 C Cleaning Time/Distance: 30 seconds / 1.5 inches Chemistry: CDA, Fine CO2 Particles Distance/Angle Time June 8 to 11, 2008 IEEE SW Test Workshop 17 ThirdThird……ProcessProcess EnhancementEnhancement ToolTool 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 18 COCO2 CompositeComposite SpraySpray TechnologyTechnology 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 19 COCO2 CompositeComposite SpraySpray TechnologyTechnology Lean Composite CO2 Sprays, used in cooperation. June 8 to 11, 2008 IEEE SW Test Workshop 20 COCO2 CompositeComposite SpraySpray TechnologyTechnology SNOW SPRAYS (Conventional) Convergent-Divergent FINE SOLIDS Nozzle ENTRAINED Liquid IN COLD CO2 HIGH VELOCITY CO2 GAS COMPOSITE SPRAYS Liquid Coaxial or Coanda CO2 Mixing Nozzle SIZE-CONTROLLED Hot SOLIDS ENTRAINED CDA IN HEATED, Additive(s) VELOCITY- CONTROLLED June 8 to 11, 2008 IEEE SW Test Workshop AIR 21 COCO2 CompositeComposite SpraySpray TechnologyTechnology 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 22 COCO2 CompositeComposite SpraySpray TechnologyTechnology Peak Impact Stress v. Propellant Pressure 65 120 psi Increasing propellant pressure and working closer to 60 the surface increases impact energy. 55 50 206 kPa 45 414 kPa 483 kPa 40 621 kPa 35 827 kPa Impact Stress/MPa 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 23 COCO2 CompositeComposite SpraySpray TechnologyTechnology Surface Impact Adjustable Particle