PLASMA SOURCES IN WEB COATING APPLICATIONS

Transcription

1 PLASMA SOURCES IN WEB COATING APPLICATIONS V. Bellido-González 1, A. Smith 2 1 Gencoa Ltd, Liverpool, UK 2 Dalmatian Technology Ltd, Kelsall, UK PSE 2008 Garmisch-Partenkirchen Germany 16 th September

2 Web coating technology It is a roll to roll process, so you start with a roll of untreated or uncoated stuff and you end up with a roll of treated or coated stuff. Web substrate vary in nature: polymeric, metallic foils, fabrics (textiles), paper 2

3 Web coating a global market Mass production sites across the globe: Traditional Packaging: Pharmaceutical Food New markets Touch pannel displays Textiles / Fabrics Solar PV on flexibles Flexible electronics Local production sites Near to market Unique features 3

4 Web Coating EMPA GVE 4

5 Why Plasma Pretreatment? Typical webs such as polymers or textiles produce a large outgassing Surface condition on webs had elements forming weak bonds deposting over them will lead to delamination. Surface energy, texture and chemistry in many cases is not ideal for a strong bond with the coating material. Web processes deposit material under web tension which strains the interface. 5

6 Web coaters coating around a drum or free spand Source: Gencoa Source: Leybold Optics High rates usually require a plurality of sputtering sources 6

7 Web Coater Source: General Vacuum Equipment Ltd., UK 7

8 Vacuum Plasma Treaters Hollow Cathode Gas N Source: Sigma Technologies International Inc. S 8

9 Vacuum Plasma Treaters Linear Microwave Source Source: Roth & Rau 9

10 Inverted Magnetron Ion Source The combination of electrical and magnetic fields under the right pressure regime forms the plasma jets GAS PLASMA PLASMA GAS 10

11 Linear Stationary Plasma Thruster Advantages: No contamination from cathode Low Ion Beam Energy <300 ev Source: W.K. Choi, KIST, Korea 11

12 Magnetron sputter sources as plasma treater Singles # Source: Gencoa / GVE Advantage: Neutral & Ion bombardment Gettering (Me + X -> MeX) Dual # Source: Gencoa 12

13 FFE for Slow moving web- fast moving plasma 13

14 Rotatables plasma treaters Source: General Vacuum Equipment, UK 14

15 Modelling the inteaction plasma-web Final configuration and settings not always optimised. 15

16 Magnetron Sputtering as Plasma Treater The right amount of Me sputtering is beneficial in terms of gettering. Excessive amounts of Me produces metal seeds or even a layer. Target life reduced. Defective amounts of Me leaves excess of components which could/would react in the nest stage of the process. What s the right amount? 16

17 Case Study An international web coater company has the same process running in 2 different countries: -Country A: Cold & Low Humidity site -Country B: variable Hot & High Humidity site Plasma treater target needs change after: 6 months in country A 1 week in country B How to put the right amount of treatment.. whatever the weather? 17

18 Right amount by feedback control Example# Typically St.St. target used Plasma spectrum & Optical Filter 520 nm filter used in standard Speedflo Plasma emmission monitoring StSt mag sputtering spectrum Cr Ar 18

19 Hysteresis curve for St.St target- O 2 reactive St St 1.0 KW# Target Voltage & PEM PEM, a.u Target V first PEAK first VALLEY PLATO Tim, s 1KW-PEM last VALLEY 1 KW-Target Voltage last PEAK PEM 520nm Gas Target Voltage, V The Plasma Emission at 520 nm has a simpler variation than the target voltage where a structure of PEAK-VALLEY-PLATO can be seen (for O 2 ramp values see previous slide) 19

20 Correlation to Me rich and O 2 excess areas St St Magnetron sputtering spectra# Gencoa HY 1.0 KW nm PLATO O 777 nm Signal, a.u VALLEY PEAK G1 (pure Ar) 777nm G2 (first peak V) G3 (first valley V) G4 O(plato 2 peak V) PURE Argon Wavelength, nm The excess of O 2 (after target poisoning) can be seen on the spectra. Notice that Ar signals are almost unchanged for the different O 2 concentrations. 20

21 Feedback Control using PEM as sensor and O 2 flow as actuation St.St. Control at different % of PEM Signals, (%, a.u.) % 90% 70% 50% 30% %PEM-Control setpoint %O2 MFC %Target Voltage 50% % 10% 5% Time, s The SPEEDFLO can control at any value of PEM setpoint (520nm- Cr peak). Different setpoints correspond to different target status. 21

22 Results from feedback control The basic plasma treatment process is the same across company sites across extreme weather conditions. 22

23 Conclusions Plasma Pretreatment of webs is necessary in order to ensure good adhesion and decreasing any detrimental influence on coating properties on the next treatment stage. Some of the main plasma treaters in use by the current industry are based on: - Hollow cathode - Linear Microwave Sources - Ion Sources - Magnetron Sputtering -The main advantage of magnetron sputtering is the getter effect which in general should require a feedback control. 23