science of plasma arc machining
TRANSCRIPT
![Page 1: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/1.jpg)
PRESENTED BY -VINIT SINGH2016PPE5370
Science of Plasma Arc Machining
SUBMITTED TO-Dr. HARLAL SINGH MALIDEPT. OF MECHANICAL ENGINEERING
![Page 2: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/2.jpg)
CONTENTS
•WHAT IS PLASMA• PLASMA CATEGORY• PLASMA PROPERTIES•USE OF PLASMA IN MANUFACTURING• PLASMA FORMATION• ETCHING• PLASMA ETCH REACTORS•ADVANTAGES OF RF PLASMA• REGIONS FORMED DURING PLASMA• PLASMA NOZZLE• REFRNECES
![Page 3: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/3.jpg)
WHAT IS PLASMA?
- Can be defined as “SUPERHEATED ELECTRICALLY IONIZED GAS”.- Creation of plasma is possible by heating the gas and subjecting through electromagnetic field.
![Page 4: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/4.jpg)
PLASMA 4th STATE OF MATTER
![Page 5: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/5.jpg)
- Plasma consist of a collection of free moving electrons and ions- atom that have lost electrons.
- Energy is needed to strip electrons from atoms to make plasma .
![Page 6: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/6.jpg)
PLASMA CATEGORY According to the temperature
PLASMA
HIGH TEMPERATURE PLASMA (10^8-10^9 K)
LOW TEMPERATURE PLASMA
HOT PLASMA
COLDPLASMA
![Page 7: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/7.jpg)
PLASMA PROPERTIES (1) PLASMA DENSITY - NO. of free electron per unit volume. (2) PLASMA TEMPERATURE - Temperature controls the degree of plasma ionization.
(3) DEBYE LENGTH - The Debye length is the distance over which significant charge separation can occur. (4) PLASMA FREQUANCY - Plasma Frequency are rapid oscillations of the electron density in conducting media.
![Page 8: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/8.jpg)
USE OF PLASMA IN MANUFACTURING
- Plasma Arc Welding HOT PLASMA �- Plasma Cutting �- Plasma Spraying�- Plasma Medicine COLD�- Food processing (non PLASMA thermal plasma, "cold plasma")- Plasma arc waste disposal (convert waste into reusable material with plasma).
![Page 9: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/9.jpg)
Plasma Formation1.By electric field2.By shock front
![Page 10: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/10.jpg)
Etching
• Electrons gain energy from RF (radio frequency) or µw (microwave)fields.
• Electrons impact with feed gas to generate ions, reactiveneutrals and more electrons.
• Ions and reactive neutrals diffuse and drift to wafersurface to remove the material.
![Page 11: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/11.jpg)
Plasma Etch Reactors
1. Capacitive Coupled Plasma CCP Type
2. Inductive Coupled Plasma (ICP) Type
![Page 12: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/12.jpg)
Capacitive Coupled Plasma (CCP)
• To start plasma formation initial voltage must exceed breakdownvoltage. It depends on gas pressure and spacing. Its value is nearly equalto 300 to 600 V
• RF current through gas maintains steady state discharge by heatingelectrons.
![Page 13: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/13.jpg)
CCP Characteristics
•The plasma is generated by RF current flow between electrodes •Plasma density (ne) tends to increase linearly with RF power •RF current across a sheath generates a dc voltage • Ions gain energy from the dc sheath voltage •ne and Eion tend to be coupled and increase together
![Page 14: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/14.jpg)
Inductive Coupled Plasma (ICP) Type
• Current in coil induces current loop in plasma in glass tube • In ICP, power is transferred to plasma by the oscillating B field.
![Page 15: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/15.jpg)
Advantages of RF Plasma
•RF current through wafer causes no damage •Easy to get induced self or DC bias •No charging damage if plasma is uniform
![Page 16: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/16.jpg)
Regions formed during plasma
1.Plasma Region • Ions are generated in this region. These are important for
etchingprocess. • Electrons carry the RF current in this region.
![Page 17: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/17.jpg)
2.Sheath Region •Electron depletion region forms at all surfaces to keep
electrons inplasma region. • In this region, number of positive ions are much
higher than number ofnegative ions. •Due to high electric field in this region, only few
electrons will be ableto overcome this region • Ions gain energy and directionality •RF current is carried by displacement (capacitor)
current
![Page 18: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/18.jpg)
Plasma Nozzle•Gas Swirling :
Swirling the gas assists cutting in several ways. Swirling increases cooling. The un-ionized gas atoms are heavier/cooler and are thrown to the outside of the spinning gas stream. This cool barrier provides protection for the copper nozzle. As amperage is increased, the amount of ionization increases (changing the 30/70% ratio) and cooling decreases, shortening the life of the nozzle. Nozzles are designed to operate within a specific current (amp) range.
![Page 19: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/19.jpg)
REFERANCES
(1)Plasma fundamentals part: http://www.prism.gatech.edu/~gtg928x/NNIN_reading_material/Fundamentals%20Part%201.pdf
(2) Plasma discharge fundamentals http://people.physics.anu.edu.au/~jnh112/AIIM/c17/Plasma_discharge_fundamentals.pdf
(3) Plasma physics Wikipedia
![Page 20: Science of plasma arc machining](https://reader036.vdocument.in/reader036/viewer/2022082620/58f9ad321a28ab776b8b45c5/html5/thumbnails/20.jpg)
THANK YOU