NanoBond : Target Bonding for Optimum Sputtering Performance Alan Duckham Reactive NanoTechnologies Reactive NanoTechnologies, Inc. (RNT) 111 Lake Front Drive Hunt Valley, MD 21030 (p) 410.771.9801 (f) 410.771.0586 www.rntfoil.com AIMCAL Fall Technical Conference October 10, 2007
NanoFoil Technology: Formation Reactions & Thermite Reactions Ni (NanoFoil ) Al Initial Reactants: Al and Ni layers (micro or nano thick) Final Product: Al-Ni Intermetallic 2
NanoFoil Applications Joining Applications Large Area Joining of Dissimilar Materials Sputter targets Ceramic-metal joining armor mounting Power Amp LED attach Large area joining Microelectronics Applications Thermal interface material Packaged part attach Power-amplifier Connector mounting 3
Conventional Soldering or Brazing Different materials shrink at a different rates Large thermal stresses when joining dissimilar materials using furnaces or hot plates Room Temperature Solder: 220 ºC Braze: 700 ºC Room Temperature 4
Joining with NanoFoil (NanoBond) Heat only the interface Use any solder and some brazes Rapid, room temperature process Metallized or Prewet Surfaces 5
Bonding Sputter Targets by NanoBond 56 x 10 TiC to Ti 50 x6 ITO to Cu 40 x10 Glass to CU 6
Modeling Heat Transfer during NanoBond Energy Conservation in each layer h r = Ñ q + Q& t Braze Layer NanoFoilTM Ti-6-4 Plate Braze Layer Inputs SiC Plate Foil reaction properties Materials properties Material geometries Interface resistances x 7
Temperature ( C) Predicted Thermal Profiles: SiC/Ti 1500 1400 1300 1200 1100 1000 900 800 t=0 Braze layers Reactive Foil 700 600 500 400 Ti-6-4 SiC (6.7 W/mK) (110 W/mK) 300 200 100 0-1.5-1 -0.5 0 0.5 1 1.5 x (mm) 8
Predicted Thermal Profiles: SiC/Ti 1500 Braze layers 1400 1300 t = 7 ms Temperature ( C) 1200 1100 1000 900 800 Ti-6-4 SiC 700 (6.7 W/mK) (110 W/mK) 600 500 400 300 200 100 0-1.5-1 -0.5 0 0.5 1 1.5 x (mm) 9
Predicted Thermal Profiles: ITO to CU 10
Case Study: SiC/Ti-6-4 SiC Plate Braze Layer (40µm) 100µm Reacting Foil IR Camera Braze Layer (40µm) Ti-6-4 Plate 11
IR Imaging of Reaction K = 80 W/m-K SiC K = 6.7 W/m-K Ti-6-4 12
IR Imaging of Reaction Images spaced at 140msec 13
Modeling of Dissimilar CTE System (2D) ITO Cu Deflection and Residual Stress significantly lower with NanoBond 14
Properties of Sputtering Targets bonded by NanoBond Elastomer Indium SnAg NanoBond 250 157 220 Thermal Conductivity (W/mK) 0.75 83.7 40 Electrical Conductivity (106S/m) 0.0021 13.9 9.3 Shear Strength (psi) 461 310 3600 Vapor Pressure (Torr) Less than 1% TMC @ 150ºC @ 10-7 Torr for 24 hr) 10-8 @ 487 ºC 10-6 @ 597 ºC 10-4 @ 742 ºC 10-8 @ 682 ºC 10-6 @ 807 ºC 10-4 @ 997 ºC Temperature Limit (ºC) Thermal Shock Bond Coverage Survived MIL-STD810: Cycle between -51 ºC and 71 ºC 95 99 % 15
Bond Inspection Destructive Strength testing Typical shear strengths = 25 MPa (3600 psi) Cross-sectional microscopy 16
Bond Inspection Non Destructive Ultrasonic scanning of bond interface to check for void content Void content of < 2 % is typical 17
Case Study Alumina Elastomer NanoBond Elastomer Bonds: Cracked at 300W, Pieces Fell off at 400 W NanoBond: Very Stable at 400 W, Ramped to 500W, Not run to Failure 18
Case Study B4C Indium Bonded NanoBond 4 tile array to Cu: 25 x 6 Vertical cracks after brief 2kW sputtering and debonding on corners No cracks after 4kW sputtering for 20 cycles and >200hrs total operation 19
Comparison Study Targets bonded to indirect cooled Cu B/Ps Target Material Power Mode Bond Type Max. Power without Failure (W) Power at Failure (W) ITO DC Elastomer 300 424 ITO DC InSn-Reflow 200 300 ITO DC In Reflow 325 (1 Hour) 425 ITO DC NanoBond 460 (12 hours) 540 Alumina RF Elastomer 300 400 Alumina RF NanoBond 400 Not Run to Failure Quartz RF NanoBond 400 Not Run to Failure TiC DC NanoBond 400 500 TiC DC Braze NanoBond 1600 (Stable) Not Run to Failure Si DC NanoBond 400 500 Significantly better performance than elastomer and reflow joints 20
Power Dependency on Solder Melting Temperature 21
Stresses During Sputtering Al2O3 bonded to Cu 22
Stresses During Sputtering Al2O3 bonded to Cu Average Temp. in Target (ºC) 50.1 Average Temp. in B/P (ºC) 31.3 Expansion of Target (ppm) 208 Expansion of B/P (ppm) 158 Stress in Target (MPa) 6 (compressive) Unconstrained expansion 23
Braze NanoBond of Sputtering Targets New process to replace diffusion bonding Ultra high strengths and temperature limits Trials on 4 in diameter targets Al to Al: 100 % coverage Cu to Cu: 100 % coverage W to Brass: >99 % coverage Scaling up process to 18 in diameter targets 24
Summary NanoBond is a substitute for Indium, Pb-Sn and Elastomer Bonds Significantly lower residual stress and deflection on components Increased throughput Higher Strength, Reliability Good Thermal and Electrical Conduction (No Arcing) Improved bond line, thickness, flatness control compared to conventional process Compatible with any solder: SnAg most often used Process proved on a number of commercial applications (All metals, Si, Ge, Oxides - incl. ITO, SiO2, Al2O3, Carbides and Nitrides) Process demonstrated on joints up to 750 Sq in with no known size limitation Braze NanoBond under development 25