A dynamic analysis on the contaminant particles’ removal mechanism

in cryogenic carbon dioxide (CO2) cleaning process

Dept. of Mechanical EngineeringDept. of Mechanical EngineeringChung-Ang University Nano-System Dynamics Lab.Chung-Ang University Nano-System Dynamics Lab.Seonghoon Lee, Pilkee Kim, Jongwon SeokSeonghoon Lee, Pilkee Kim, Jongwon Seok

Contents

■ Motives & Objectives

■ Cleaning methods for the removal of fine particles

■ Theories of CO2 snow cleaning

■ Modeling of particle detachment mechanism

■ Simulation for particle detachment mechanism : Rebounding

■ Discussion & Remaining issue

Motive & Objectives

■ Motive- Weak point : Adhesion and removal mechanism among the particles

- Requirement : Optimization of CO2 snow cleaning method

by adopting reasonable adhesion model

■ Objectives- Adhesion mechanism between substrate & contaminant particle,

CO2 snow particle & contaminant particle

- Dynamic modeling and simulation

- Optimization of CO2 snow cleaning method

for high PRE (Particle Removal Efficiency)

Megasonic cleaning method

Wet cleaning Dry cleaning

Chemical fluid application

- APM (Ammonia peroxide mix)

- HPM (Hydrochloric peroxide mix)

- SPM (Sulfuric peroxide mix)

- DHF (Diluted hydrofluoric acid)

Sputtering

Chemical dry-cleaning

UV/O3 cleaning

Laser Cleaning

Cryogenic Cleaning

Cleaning methods for the removal of fine particles

Cleaning methods

■ The principal mechanisms

- Phase transition : gas & solid CO2 (2 phase)

- Nucleation process

- Particle removal mechanism

Phase transition

1 phase CO2 ( about 60 bar, -80 )℃

Gas CO2 + Solid CO2

(about 1bar, -80 )℃

Adiabatic expansion process

Theories of CO2 snow cleaning

Container

Nucleation process- For gas CO2 source (Build-up process)

45 % for liquid source >> 8 % for gas CO2

Liquid CO2

Gas CO2

Solid CO2

- For liquid CO2 source (Break-down process)

Dry ice snow yield

Theories of CO2 snow cleaning

Particle removal mechanism

- Momentum transfer by solid CO2

- Drag force by gas CO2

- Thermophoresis

Removal force Adhesion force

(40%)

(50%)

(10%)

: Rebounding, Rolling, Sliding, Lifting

Theories of CO2 snow cleaning

Adhesion forcesRemoval forces

- Van der waals force

- Electric double layer force

- Capillary force

- Hydrogen bond

detachment

■ Contact modelHertz model

JKR modelGT-JKR model

Hertz model : Model considering contact and deformation for external force JKR model : adhesion force + Hertz model GT-JKR model : surface roughness + JKR model

Contact between CO2 snow & contaminant particle Hertz model Contact between substrate & contaminant particle JKR model

Modeling of Particle Detachment Mechanism

y1, y2

x1

x2

d1

d2

■ Particle detachment

Modeling of Particle Detachment Mechanism

Dynamic modeling of rebounding by vertical collision among particles

d1 : displacement of CO2 snow , d2 : displacement of contaminant

v

■ Assumption Perfect-elastic bodies without plastic deformation for each materials

Shape of particles : Spherical contaminant / Spherical dry-ice

Contact model : Hertz model, JKR model

Removal mechanism : Rebounding by vertical collision

No gravity effect

Silica substrate PTFE contaminant Dry-ice

Young’s modulus (GPa) 94 0.53 8.9

Poisson’s ratio 0.17 0.33 0.34

Density (kg/m3) 2300 2200 917

Adhesion energy 0.024 (J/m2)

■ Material properties

Modeling of Particle Detachment Mechanism

Contaminant radius : 0.1 ㎛ Snow radius: 1 ㎛

(a) Initial Collision velocity : 3 ㎧ (b) Initial collision velocity : 5 ㎧

(c) Initial collision velocity : 8 ㎧ (d) Initial collision velocity : 10 ㎧

Collision velocity ↓ : Insufficient momentum

■ Dynamic characteristics according to collision velocity

Contaminant remain

Contaminant remain

Contaminant removal

Contaminant removal

Simulation for particle detachment mechanism : Rebounding

Contaminant displacementDry-Ice displacement

Radius ↓ : Adhesion force increase, Radius ↑ : Insufficient momentum

■ Dynamic characteristics according to contaminant radius

Contaminant displacementDry-Ice displacement

Simulation for particle detachment mechanism : Rebounding

Snow radius : 1 ㎛ Snow velocity : 1 ㎧

(a) Contaminant radius : 0.1 ㎛ (b) Contaminant radius : 0.5 ㎛

(c) Contaminant radius : 1 ㎛ (d) Contaminant radius : 2 ㎛

Contaminant removal

Contaminant remain

Contaminant remain

Contaminant remain

Conclusion & Remaining Issue

■ Conclusion

Finally, we concluded that the results of this simulation are similar to general tendencies of fine particles in the cleaning process.

Elasto-plastic material

Surface roughness

Sliding, rolling & lifting

■ Remaining Issue

First simulation shows that the insufficient momentum of snow induces the particle contaminant to remain on the substrate.

Also it is found that the fine particle is difficult to remove from the substrate surface as known generally

Thank you