Photonic Curing and Soldering

Transcription

1 Photonic Curing and Soldering Ultra-fast Fabrication of Printed Electronics AIPIA Conference, Utrecht November 19 th, 215 Rob Hendriks Research Engineer

2 Presentation overview Introduction Photonic Curing Working principle Process optimization Photonic Soldering Reflow versus photonic Process study Simulation Summary PulseForge 13 Photonic Curing system Research and Development 2

3 Introduction NovaCentrix Enabling printed electronics Partnership model to drive technology PulseForge Tools Photonic curing equipment Sheet-to-sheet and Roll-to-roll SimPulse temperature simulation Highly advanced photonic curing systems Metalon Conductive Inks Silver, copper, copper oxide, etc. Nanopowders Silver, aluminum, metal oxide, etc. Copper oxide reduction ink 3

4 Introduction Smart Packaging & Printed electronics Smart packaging can be used to prevent wastage of food products Smart labels should be relative inexpensive compared to the product Roll-to-roll compatible fabrication methods are required Etched copper & Packaged chips Printed conductive inks & Bare die chips 4

5 Introduction Sintering Merging particles via atomic diffusion Fraction of bulk melting temperature Metal nanoparticle inks are suited for conductive structures on polymer films Curing of conductive inks Sintered Ag nanoparticles 1) Solvent evaporation: Densification and packing of particles 2) Breaking shells: Degradation/melting of polymer stabilizers 3) Sintering particles: Atomic diffusion, grain growth Solvent evaporation Breaking shells Sintering particles 5

6 Resistance (Ω) Temperature ( C) Introduction Oven curing on polymer / paper substrates Slow heating of the ink and substrate through convection Typical processing conductions: C for 2 minutes Oven curing not suited for roll-to-roll production Time (seconds) FIB-SEM cross-sectional image of a curing silver ink 6

7 Normailized absorption (emission) Photonic Curing Photonic curing working principle Selective heating of the ink through light absorption High intensity and short light pulses rapidly heat up the ink ( 25 C) Typical pulse lengths:.2 2 ms 1,9,8,7,6,5,4,3,2,1 PET film Ag nanoparticles Lamp emission Wavelength (nm) Absortion / emission spectrums Temperature modeling 2 millisecond pulse 7

8 Photonic Curing Wrong temperature profiles Too long above the glass transition temperature of the substrate Short and high intensity pulses on wet ink Too high peak temperatures at the ink / substrate interface Shell formation Short pulses on wet ink 5 x 5 x SEM, 1 x Exploding bubbles Too fast heating Ablation (pre-dried ink) Too high peak temperature 8

9 Temperature C) Photonic Curing Optimal temperature profile Highest conductivity, best topology, shortest time Photonic flash curing PulseForge equipment T melt IR dyring, continuous illumination T g Time (seconds) Pulse modulation, SimPulse Solvent evaporation Breaking shells Sintering particles 9

10 Photonic Curing Roll-to-roll processing of RFID antennas Modulated pulse (5 micro-pulses) to control temperature profile Operating at 33 m/min, longer pre-drying enables even higher speeds 1

11 Photonic Curing PulseForge equipment PulseForge 12 / 13: Research and Development (S2S) PulseForge 32 / 33: Development and Production (R2R) Full compatibilty Pulse settings Sheet-to-sheet (PulseForge 13) Roll-to-roll production (PulseForge 32) 11

12 Photonic Curing: Process optimization SimPulse: Temperature profile simulation Design your stack Shape the pulse Desired temperature profile Very fast for optimizing process conditions Stack design - Add up to 6 layers - Define thickness Materials - Database - Physical properties - Add your own Boundary conditions - Convection, heat sink Simulation time: - Fraction of a second 12

13 Temperature ( C) Photonic Curing: Process optimization Temperature / Resistance probe High temperature, high sensitivity, high speed: 4, S/s, > 5 C Close-up Conductive ink Insulation Temperature probe Glass 2 Double 4-point measurement T( C) = R(Ω) R² = Probe 2 Temperature sensor (RTD) Resistance (Ω) Temperature / Resistance probe Probe characterization 13

14 Resistance (Ω) Temperature ( C) Photonic Curing: Process optimization Temperature / Resistance measurements The measured temperature profile shows similar results as SimPulse Pulse modulation is a necessity for process control 1 PChem PSI-211: 2.5 µm thick Time (milliseconds) Measuring setup in PulseForge 13 14

15 Temperature ( C) Photonic Soldering Reflow versus Photonic Soldering Typical temperature profile for reflow soldering: > 2 C for 5 minutes Reflow is not possible with temperature sensitive substrates Reflow soldering Photonic soldering Time (milliseconds) 5 minutes 6, times faster 5 milliseconds 15

16 Resistance (Ω) Photodiode (V) Photonic Soldering Proof of Principle The bare die chip is soldered, but it jumps during heating What is the temperature within the stack during photonic soldering? 1 1 Channel 1 Channel 2 Photodiode,9,8 Bare die chip 1 1 Jumping chip,7,6 1,5 1 4 ms, 4.6 J/cm 2 1 Pre-dried 1 Soldered,1 Pulse, Time (milliseconds),4,3,2,1 Substrate: Polyimide 125 µm Bond pad: Copper 18 µm Solder paste: NC-56-LF ~ 2 µm Chip: IZM µm 16

17 Photonic Soldering: Process study Blow off & Flipped chips With photonic soldering there is a high change of blowing off the chip Too high chip temperature causes rapid gas generation within the solder The temperature profile should be properly controlled Chip blow off (IZM28) Flipped chip, partially soldered 17

18 Photonic Soldering: Process study Photonic Soldering probe The temperature probes are 18 x 18 µm 2 in size Designed for a IZM41.1 chip: 1 mm 2, 5 µm pitch, 25 µm bumps Temp / Resistance probe Microscope image of the bond pad (back) 18

19 Photonic Soldering: Process study Stack build-up Substrate: Borosilicate glass 7 µm Temperature probe: Metal.4 µm photolitho Conductive track: DuPont µm screen printed Buffer layer: DuPont Exp. paste 16 µm stencil printed Solder paste: NC-56-LF, type 6 2 µm stencil printed Bare die chip: IZM µm pick&place Bond pad Cross-section (FIB-SEM) Solder paste, without chip 19

20 Resistance (Ω) Temperature ( C) Photonic Soldering: Process study Experimental data After placing the chip, pre-drying at 95 C for 2 minutes Pulse settings: 5 ms, 3.4 J/cm ,1 6,1 5 ms, 3.4 J/cm 2 Pulse Time (milliseconds) 3 Photonic soldered IZM41.1 2

21 Photonic Soldering: Simulation Stack build-up A 3D model of the stack is developed to predict soldering behavior The solder paste has temperature dependent material properties Between every layer there is a decomposition layer to simulate blow-off P pulse * Abs chip P pulse * Abs ink P pulse * Abs glass Chip (2 µm) Pre-dried Soldered Solder paste (2 µm) Buffer layer (16 µm) Conductive ink (6 µm) Glass (7 µm) Limited heat sinking to substrate Strong heat sinking to substrate 21

22 Temperature ( C) Curing degree (-) Photonic Soldering: Simulation Temperature dependent material properties (irreversible) Soldering behavior is defined by three parameters: Activation temperature (T act. ), Effective curing time (t eff ), Accelerated Curing Factor (ACF) Thermal conductivity (heat sinking) increases with the curing degree 4 35 T decomposition 1 dt c t c 3 ACF T activation Curing profile 1 t effective Time (milliseconds) Effective time (s) 22

23 Photonic Soldering: Simulation Temperature profile & Soldering behaviour Soldering parameters: T act. : 18 C, t eff. : 1 ms, ACF: 2 Thermal conductivity of the bump: 1 6 W/mK, pre-dried soldered Temperature Soldering 23

24 Resistance (Ω) Temperature ( C) Average curing degree (-) Temperature ( C) Photonic Soldering: Simulation Validation A good fit between experimental and simulated data was found Peak temperature of the chip is 35 C, which is close to ablation Model can be used to predict soldering behavior various chips sizes Curing Probe Track Chip ,9,8,7, ,5 2, ,4,3,2, , Time (milliseconds) Time (milliseconds) 24

25 Curing degree (-) Temperature ( C) Photonic Soldering: Simulation Geometry dependency Significant influence of the chip geometry on the soldering behavior Thicker chip Higher fluence Larger chip Lower fluence The pulse settings need to be tuned for the chip geometry 1 Curing Probe Track Chip 4 1 Curing Probe Track Chip 6 1 Curing Probe Track Chip 4,9,8,7, ,9,8,7, ,9,8,7, ,5 2,5 3,5 2,4,3,2, ,4,3,2,1 decomposition ,4,3,2, Time (milliseconds) Time (milliseconds) Time (milliseconds) 4 µm thick chip 2 mm 2, 2 µm thick chip 2 mm 2, 4 µm thick chip 25

26 Summary Photonic Curing Fast method for achieving highly conductive structures Printed (flexo, inkjet, screen, etc.) to fully cured within seconds Two stage processing for limited substrate deformation Photonic Soldering Enables soldering on temperature sensitive substrates (PET, paper) Highly efficient and roll-to-roll compatible 3D simulation is necessary to understand process (in progress) PulseForge equipment State-of-the-art photonic curing equipment Enables roll-to-roll production of printed electronics 26

27 Acknowledgements Holst Centre Gari Arutinov, Daan van den Ende (Philips), Guy Bex, Eric Rubingh, Robert Abbel, Pit Teunissen, Pim Groen, Jeroen van den Brand Modelling Erica Coenen (TNO) Software and Data acquisition Henk Steijvers (TNO) Temperature probes Tom Geuns (Philips) 27

28 Thank you Rob Hendriks Research Engineer Ph: +31 () Harald Moder Merconics Ph: