IWLPC October 13-15, 2015 Daniel Duffy Ph.D., Hemal Bhavsar, Lin Xin, Jean Liu, Bruno Tolla Ph.D. Kester Inc., Itasca, IL, USA

 Introduction ◦ Conventional Flip Chip Assembly Process ◦ One Step Chip Attach Process & Materials ( OSCA )  OSCA Materials for Reflow Processing ( OSCA-R ) ◦ Copper Pillar Test Vehicle ◦ Design for Dispensing & Die Placement ◦ Fluxing and Curing Kinetics During Reflow ◦ Assembly by Conventional Reflow  Summary & Conclusions  Acknowledgements 2

New and Improved Process Flow Flux / Chip Place Reflow De-flux Underfill Post Cure Flux & Die Placement Reflow Cleaning Post Cure Underfill Underfill 3

 Process Simplification + Throughput Dispense OSCA-R Place Die Next Process Step Dispense OSCA-R Die PlacementConventional Reflow Processing 4

 Wafer level assembly  3D assembly  Fine pitch where flux residue removal is challenging 5  High device density  Use where capillary underfill materials face limitations

Dispensing Die Placement Reflow Processing Post Cure or Additional Assembly Steps OSCA-R Material OSCA-R Process  OSCA-R materials enable assembly process simplification ( no need to clean flux residues ) Rheology Wetting & Flow Design Cure Kinetics & Thermomechanical Design 6

Dispensing Die Placement Fluxing Reflow Processing Controlled Flow & Wetting Filet Formation Solder Wetting & Interconnection OSCA CuringAssembled Device 1/ Rheological Profile designed for Assembly 2/ Fluxing & Cure Kinetics balanced for appropriate sequencing 7  OSCA-R materials have a range of flow and functional requirements during processing

 OSCA-R materials are multi functional reactive mixtures that thermally cure to a high performance thermoset polymer composite during reflow processing Fillers Rheology Color Density Monomers Viscosity Flow, tack Wetting Cure Chemistry Activators Fluxing Adhesion Hardeners Viscosity Flow, tack Wetting Cure Chemistry Monomers Cross Links Tg, CTE Modulus Adhesion Hardeners & Activators Cross Links Thermal Stability Tg, CTE Modulus Adhesion Fillers CTE Modulus Hardness Toughness Thermal Conductivity Reliability Moisture Resistance Thermal Cure  Catalyst Cure Kinetics 1k Liquid Material High Tg Polymer Composite Fluxing

 OSCA-R materials have been investigated using a number device configurations ◦ Silicon & ceramics tend to have better outgassing than organics and lower voiding with OSCA-R materials ◦ Solder capped structures are found to exclude fillers from the joint during reflow 9

 Cu pillar test vehicle used for OSCA-R evaluations 10 Wafer thickness = 0.75mm Die size = 6.35x 6.35mm. Two daisy chained arrays Central Array 20x 20 bumps (400) Perimeter Array is 5x 70 bumps per side (1300) 128 interstitial bumps Pitch = 80 microns Cu Pillar Height = Diameter = 40 micron 10 micron SnAg cap on pillars Cu Pad Diameter = 40 microns Cu Pad Height = 10 micron

 OSCA-R materials designed for use with different dispense technologies 11 Time-PressureAugerJet Time-Pressure PDP - Auger NanoShot TM Jet Dispense

Formation of Stable Droplets Wetting & Flow Control During dispense No Stringing Controlled Flow Pattern & Shape Retention Reology & Dispensing Behavior  Fluids with shear thinning / yield stress behavior meet patterning & flow control CTQs 12

Reology & Dispensing Behavior  OSCA-R materials have good jet dispensing characteristics and pattern retention  Controlled flow keeps materials out of “no-go” zones and avoids bleed out 13 OSCA-R Dispensed on Test Vehicle

 OSCA-R materials designed to overcome key placement challenges Rebound (viscoelasticity) Void Elimination Flow properties enable dispense pattern and void elimination Flow behavior during die placement under compression can complicate accurate die placement 14

 OSCA-R materials designed to overcome key placement challenges and to be compatible with common placement technologies 15 Board Level Assembly Flip Chip Assembly R&D Bonder Thermo Compression Bonding

 Using a Finetech die bonder system ◦ Multi step placement procedure ensures die contact, and flow 16

 Timing kinetics of fluxing, solder melting, interconnection and cure 17

 OSCA-R cure kinetics tunable to meet a given reflow profile  Ensure fluxing, interconnection and cure occur in the proper sequence and at desired times during reflow 18 TAL BD Model Parameter DefinitionUnitsUnfilled, 0%Filled, 40% N Reaction order E Activation Energy kJ/mol4452 Log ( Z )Pre Factor1/min HH Reaction Enthalpy J/g Reaction Kinetics Modeling via DSC

 Examples of reflow profiles used to assemble devices with OSCA-R materials  Range of profiles for different assembly applications

 Illustration of relationship between placement voids and ORCA-R rheology design 20 (a) (b)

 Successful assembly of devices with copper pillar features using conventional reflow processing and OSCA-R materials 21

Property (method)UnitsABCD Filler %Wt% Filler Sizemicron0.5 5 Tg (a)°C CTE-1 (a)ppm/K CTE-2 (a)ppm/K  H (b) J/g T-onset (b)°C T-peak (b)°C Viscosity(c)Pa-s Viscosity(d)Pa-s STI (e)Ratio Yield Stress (f)Pa2000 Temperature Thinning (g)Kelvin Flow 22  Rheology, viscosity, flow properties tunable for target dispensing/flow during die placement, cure kinetics and thermomechanical properties Thermo. Cure

 One Step Chip Attach (OSCA-R) materials can be used to assemble devices with copper pillar features using convection or conduction mass reflow ◦ Single die devices assembled in this work ◦ Can be extended to wafer level ◦ Can be used for 3D assembly ◦ Device density increase, close placement ◦ Approach reduces complexity of manufacturing with respect to conventional processing ◦ Higher throughput with use existing processing equipment 23

 Approaches to overcoming the key technical challenges presented ◦ Systematic studies of soldering, rheology cure kinetics and used to design OSCA-R materials for dispensing and successful assembly ◦ Die and substrate size, configuration and type are integral considerations for OSCA-R materials and processing 24

 Process integration is key to enabling OSCA-R materials ◦ Chemistry matched to desired reflow processing ◦ Rheology adjusted for dispensing and die placement process 25

 Kester Inc.  David Eichstadt, Maulik Shah, Chris Klimaszewski, Jim Lowe, Kal Chokshi  ITW Innovation Center  Marina Litvinsky  Research Triangle Institute, NC.  Chris Gregory, Alan Huffman  TA-Instruments  Gregory Kamykowski PhD, Kushal Modi  Finetech  Neil O’Brian, Adrienne Gerard, Wade Gay  Sonoscan  Michelle Forbes 26

Thank You for Your Attention Questions? 27