sirris materials day 2011 thin film sensors - a key to intelligent production - smart coating...

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Thin film sensors: a key to intelligent production

Materials Day 2011

Why use thin film sensors?

• Measurement on every position in the system

• The integrity of the tool is not decreased

• The coating has no influence on the behavior of the system

• Fast response time due to the small mass of the sensor

• No interference with other components of the system

6-10-2011© Sirris | www.sirris.be | [email protected] | 2

Key to intelligent production?

Case: The machining industry• Machining of high-end applications

• Too expensive limiting cost is a must

Higher productivity using high quality tools


Modern Machine Shop, 2008

Machining: Ceramic Wear- ResistantCoatings

• Widely accepted and applied• Deposited mainly using PVD and CVD• Increase in tool life up to a factor 10 compared to uncoated

tools

IFused correctly!


Machining: Lifetime of a Tool

• Influenced by the temperature• Too high temperature for too long: degradation of the coating• For some coatings, too low working temperature: no advantage


Machining: optimal tool usage


in time40%

400k€

too early45%

450k€

too late15%

scrap 45k€

Machining: Tool Condition Monitoring


Technique Principle Advantages Disadvantages Acoustic emission Measurement of

released energy from dislocation movements

• Good technique for tool breakage or fracture

• Difficult analysis of signals • Interference from cutting

condition variations • Only suitable as additional

technique for increased reliability for TCM

• Difficult to measure wear • Lack of database on AE for

different materials and machining conditions

Cutting edge temperature

The temperature has an influence on the rate and mode of wear and friction

• Ideal for wear monitoring • Temperature distribution is not uniform

• Cutting edge temperature is very difficult to monitor exactly

Cutting forces Measurement and

interpretation of force measurements

• Correlated to tool wear • Interference from tool vibrations • High degree of variability

Vibrations • Sensitive to tool wear • Only usable in combination with force measurements

Machining: Tool Condition Monitoring

Advantages of knowing the tool’s cutting edge temperature

• Prevention of excessive heating• In time feedback to machining parameters

• Prevention of sub-optimal use of the tools• Cost reduction in purchasing new tool• Minimal scrap production

• Constant product quality

• Higher productivity and efficiency


Machining: cutting edge temperature

• „However, none of the laboratory methods for measuring temperatures reported in the literature is simple and reliable enough for routine testing” [1993].

• “However, the search for a practical method that can be used in an industrial environment continues” [2000].

• „Unfortunately, determination of cutting tool temperature distributions is technically difficult and past research has not provided sufficiently accurate temperature data” [2005].


Machining: Temperature MeasurementMethods

Tool thermocouple Radiation techniqueBuilt-in thermocouple

Inverse heat conduction method (IHCM)Metallographic technique

Powder techniqueThermo-luminescence

OpticalTemperature Sensor Coatings:

• The integrity of the tool is not decreased• The coating has no influence on the temperature behavior and the

heat flow of the system • Fast response time due to the small mass of the sensor• No chip interference


Temperature sensor coatings


Other application

• Injection moulding


Thin film sensors today



Sensor- development

Sensor coating(isolation and sensor)

StructuringLithography

Laser caving

Aerosol printing

Wireless

Concept of the sensor

RTD Thermocouple

larger measurement spot small size

Power source needed thermoelectric power

easy signal amplification more difficult signal amplification

1 layer sensor 2 layer sensor

signal can be customized signal depending on materialcomposition

4 bond pads 2 bond pads

Accurate and stable in time extreme temperatures



RTD Thermocouple


substrateisolatorsensorisolator

Wear resistant layer

substrateisolator

sensor

isolatorWear resistant layer

sensor isolatorisolatorisolisol



• Multilayer stack • The different layers have to be compatible. • Important parameters are the linear coefficient of

expansion and hardness

• High temperature stability• High oxidation resistance and structural stability at high

temperature

• Economically• Can the sensor coating stack be deposited in a limited

number of steps.

The dielectric layer

• Required properties• Electric isolation• High break down voltage

• Influenced by defects and porosities in the layer• High temperature stability• Compatible with substrate and coating• As thin as possible• Low cost

• Some possible coatings

• Al2O3, AlN, Si3N4, SiO2,…


• Effect on deposition rate

The dielectric layer


(Glockner et al. 2000)

(Chiba et al 2007)

Al2O3

Requirements for structuring of a sensor

Structuring a sensor coating on a 3D-shape


• 2D 3D• High resolution• Conformal• Reproducible• Scalable• Flexible• Low cost

Structuring Techniques


• Investigation on possible techniques for structuring a sensor coating on a 3D surface

• Cost, time, accuracy, degree of difficulty, compatibility with PVD

• Methods for thin film structuring described in literature• Masking, • Laser ablation• Photolithography

• Aerosol• Ink jetting • Screen printing a chemical etching

Well known techniques

Development stage

Laser ablation


• Locally remove coating by sublimation using a laser beam• Flexible design adaptation (CAD drawing)• Non-contact, non-chemical• Maskless• Low cost

• Contour laser ablation• Efficiency process depends on thermal and optical properties of material• Ablation rate and depth influenced by

• Absorption properties material• Laser parameters

• Laser energy• Pulse duration• Pulse repetition rate

Laser ablation


Substrate: steel

Coating: ceramic

Ablation time: 5 seconds!

Laser ablation TiAlN


Melting edgeSmall cracks

Laser ablation


• Optimisation of parameters

Photolithography versus laser ablation

Photolithography: 6 steps Laser ablation: 1 stepLong throughput times 40 seconds complete wafer

Laser ablation

• High resolution• Contourscan


Photolithography versus laser ablation

Building a proof of concept for a wirelessconnection

Basis = CC2520 development kit TI (Texas Instruments)• Complete platform to test advanced prototype RF systems


Proof- of- concept wireless system


R-meas.

Sensor

Heating element

Solid state relais

PT100

Interface

Master

Slave

Sensor interface specifications

• Wireless Communication: Zigbee (2.4 GHz)• Sensor sample rate: 1600 Hz• Accuracy: 0,5 °C • # sensors: 2• Dimensions: ± 5cm x 3cm


Measurement set- up


Electrical characterization

• Positioning of components important• No hysteresis when Pt 100 reference is

positioned on sample


Electrical characterization


If a thin temperature sensor is available

• development of thin film pressure sensorsis possible

Outlook

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Thank you for your attention!

Questions?

sirris materials day 2011 thin film sensors - a key to intelligent production - smart coating...

Technology

cutting edge

thin film

small mass

infosirris

temperature

tool

sensor

structuring