A DropA Drop--onon--DemandDemandPrintheadPrinthead Suitable for Suitable for

Hot and Relatively Hot and Relatively Viscous LiquidsViscous Liquids

Wolfgang WehlWolfgang Wehl •• JJöörg Wild rg Wild •• BjBjöörn Lemmermeyer rn Lemmermeyer •• Michael KMichael Küüblerbler

International Workshop on Ink-jet Printing of Functional Polymers and Materials 29-30 June 2005, Eindhoven, The Netherlands

Institut für Mechatronik Heilbronn

© IMH • W. Wehl (2005)2

B. Lemmermeyer

Institut für Mechatronik HeilbronnInstitut für Mechatronik Heilbronn(University of (University of AppliedApplied SciencesSciences))

Prof. W. Wehl

Prof. J. Wild M. Kübler

© IMH • W. Wehl (2005)3

FlipFlip--Chip Chip –– Really very Simple, or?Really very Simple, or?

contact pads

substrate

0,5 mm

die

(solder) bumps

[adapted from Reichl Direktmontage 3.40]

© IMH • W. Wehl (2005)4

1. Stencil Printing

• Advantages: reasonably priced

• Disadvantages: lack of miniaturization potential, stencil required ⇒ prevents use for rapid prototyping

2. Galvanic Deposition

• Advantages: excellent miniaturization

• Disadvantages: prolonged and costly production, mask(s) required ⇒ prevents use for rapid prototyping

The Problem: Bump ProductionThe Problem: Bump Production

Up to now no production method for bumping Up to now no production method for bumping exists which is reasonably priced, reliable and exists which is reasonably priced, reliable and

harmless to the environment! harmless to the environment!

© IMH • W. Wehl (2005)5

PiezoPiezo--Jet Jet –– The Functional PrincipleThe Functional Principle

5 mm

throttle pressure chamber nozzle

piezo actuator

© IMH • W. Wehl (2005)6

PiezoPiezo--Electric DropElectric Drop--onon--DemandDemand--PrintheadPrinthead

silicon die34 x 15 mm2

glass covering

nozzle

pressure chamber

supply chamber

piezo actuator

© IMH • W. Wehl (2005)7

DropDrop--onon--DemandDemand--PrinttheadsPrinttheads::much more than only Ink Sprayers!much more than only Ink Sprayers!

•varnishes

•oils

•glues

•melted waxes

•fuels

•mercury

•…

•• … why not hot, liquid metals, too?… why not hot, liquid metals, too?[Video: TU München, Feingerätebau]

© IMH • W. Wehl (2005)8

The Invention: The MetalThe Invention: The Metal--JetJet PrintheadPrintheadmicro machined die

glass siliconnozzle

ceramic housing (ZrO2)

piezo-electricallamella actuator

passivated tip forthermal decoupling

heateractive part

© IMH • W. Wehl (2005)9

Function of the MetalFunction of the Metal--JetJet PrintheadPrinthead1. heater on

2. solder melts

3. electrical stimulation⇒ metal-jet printhead ejects droplets

© IMH • W. Wehl (2005)10

Many Contradictory ChallengesMany Contradictory Challenges1. Solder Leading System

• Tolerances in micro meter range

• Perfect thermal conductivity

• Homogenous temperature allocation

2. Actuator and Fixtures• Very less thermal conductivity

3. Connections• High force transfer (pull forces too)

• Partly tense for liquid and gaseous flows (solder / inert gas)

4. General• Temperature Resistance up to 300 °C (option 700 °C)

• Same material coefficients of expansion

© IMH • W. Wehl (2005)11

A Micro System A Micro System –– Core of the Metal JetCore of the Metal Jet PrintheadPrinthead

Micro machined silicon die with Pyrex glass coveringAdvantages

• high thermal resistance• chemical, mechanical resistant • micro machine made

34 x 10 mm2

© IMH • W. Wehl (2005)12

Structure of the Metal JetStructure of the Metal Jet PrintheadPrinthead

fixturepiezo ceramic

die

solder tank

heater

Drive: Piezo lamella actuator with a zirconium oxide fixtureAdvantages

• high thermal resistance• low thermal conductivity• lot of design scope

© IMH • W. Wehl (2005)13

… the Challenge is Putting it together!… the Challenge is Putting it together!heating to operation temperature: ΔT > 250 K

αSi = 2,6·10-6 K-1 αZiO2 = 10·10-6 K-1 αPiezo = 6,5·10-6 K-1

↑F

→F

↓F

connection points

Pyrex/silicon ceramic (ZrO2) piezo ceramic

© IMH • W. Wehl (2005)14

The Ingenious Simple Solution and …The Ingenious Simple Solution and …

Pyrex/silicon piezo ceramic

© IMH • W. Wehl (2005)15

... how it Works: In an Acoustic Manner... how it Works: In an Acoustic MannerPyrex-glass solder micro system (Si) piezoelectric actuator

heating droplet nozzle passive zone actuating zone

A

B

© IMH • W. Wehl (2005)16

t0

t1

t2

t3

t4

t5

t6

t7

t8

a b c d

A

B

Propagation of Tensile and Pressure WavesPropagation of Tensile and Pressure Waves

U

t

+F

-F

© IMH • W. Wehl (2005)17

The Assembled Metal JetThe Assembled Metal Jet PrintheadPrinthead

© IMH • W. Wehl (2005)18

MetalMetal--Jet: Solder Droplet EjectionJet: Solder Droplet Ejection

© IMH • W. Wehl (2005)19

potential of the IMH technology

4

4. hot-melt piezo-jet(IMH)

2

1,0

η/Pa·s

0,1

0,01

0,001

0,0001

DropDrop--onon--DemandDemand--Printing of Different LiquidsPrinting of Different Liquids

-100 -50 0 50 100 150 200 250 300 350 400 450 500t/°C

glycerinevarious

oils

3

1. bubble-jet

2. piezo-jet (standard)

3. hot-melt piezo-jet(Spectra)

1

water

Sn63Pb37solder

n-propanol

© IMH • W. Wehl (2005)20

Additional ApplicationsAdditional Applications

Micro dosing

• Ejection of “difficult” fluids at high temperatures, too

•Varnishes, oils, glues, fluxes, waxes and so on

Rapid Prototyping

• Manufacturing of small, metallic, robust and thermal resistant devices

3D-MID (Moulded Interconnected Device)

• Metallization and passivation of three-dimensional devices

© IMH • W. Wehl (2005)21

SummarySummary• The new printhead technology of the Institut für

Mechatronik Heilbronn allows ejection of liquids up to temperatures of 300 °C and viscosities of 400 mPa·s

• A smart thermal decoupling of the piezo actuator prevents risk of destruction

• Acoustic operation protects the parts of the printhead from thermal stress

• Wafer bumping is a pilot application of the new printhead

• Other applications are micro dispensing of “difficult” liquids, rapid prototyping, 3D-MID metallization