Future Thin and Flexible Systems?

Transcription

1 Packaging and Thermal Management Challenges for Future 1-mm Thin Smartphones? Y. C. Lee, University of Colorado - Boulder Three CU technologies: Flexible thermal ground planes All solid state battery Atomic layer deposition Future Thin and Flexible Systems? Microsystems Integration 1

2 Future 1-mm Thin and Flexible Smartphones? Glass or Polymer Cover; 0.05 mm 55-75µm thick chips OLED; 0.05 mm Chips (0.075mm) PCB TGP- Thermal Ground Plane (0.20 mm) Li Anode (0.075mm) Solid State Electrolyte (0.075mm) New Cathode (0.4 mm) K=300 W/mK K=5,000 W/mK Aluminum (0.05 mm) Polymer Case; mm Microsystems Integration 2

3 Copper Heat Spreader with 200µm Air Gap 2 W/(4mm x 4mm) Air Gap Polymer Copper 66 o C Polymer Natural convection on top and bottom sides with T air = 25 o C 45 o C Thickness = 1 mm + Air Gap Microsystems Integration 3

4 200µm Air Gap: Not Good Enough! Air Gap Polymer Copper 62 o C Polymer T air = 25 o C Bottom Side 43 o C Microsystems Integration 4

5 Flexible Thermal Ground Planes (TGPs) Heat pipe is used in almost every laptop computer today. Heat is transferred effectively by utilizing phase-change processes. Heat pipe is transformed into two-dimensional vapor chamber that is currently the working horse for many high power electronics. The flexible thermal ground plane (TGP) is the best vapor chamber with a thin, flexible and conformable configuration. TGP is very manufacturable since it is made by using printed circuit board (PCB) technologies. Microsystems Integration 5

6 Thermal Ground Plane (TGP) 2 D flat heat pipe, vapor chamber Microsystems Integration 6

7 Copper-Cladded Kapton for Flexible TGP 9.5 cm X 5 cm X 0.1cm; 8 grams Copper Mesh: 4 grams Nylon spacer: 1 gram Copper Cladded Kapton: 1.5 gram Water: 1 gram Microsystems Integration 7

8 Microsystems Integration 8

9 Flexible Circuit Board Technologies Flexible Thermal Ground Planes (TGPs) Copper (measured) K eff > 2,000 W/mK w/o thermal resistances across Kapton; K eff > 3,000 W/mK Microsystems Integration 9

10 Thermal Resistance Network of Another TGP Microsystems Integration 10

11 Vapor Core Thermal Resistance Vapor Thermal Resistance: A drop in pressure from viscous flow results in a drop in temperature (lower saturation pressure) affected by the gap of the vapor core: v. Viscous pressure drop in vapor-phase (Poiseuille s law): Vapor Transport: P vapor T vapor ~ 70 o C ~ 40 o C R a, vapor Temperature Difference: Heat Source Heat Sink Effective Thermal Conductivity of Vapor Clausius Clapeyron relation dp v /dt v = h v /T R vap = x/(k v w ) assumed Microsystems Integration 11

12 Microsystems Integration 12

13 An Example of Typical Thermal Resistances For a TGP with a thermal conductivity of ~1,500 W/mK; it is different from the one presented in the last slide. Microsystems Integration 13

14 Thin and Flexible Thermal Ground Planes (TGPs) (10cm x 5cm x mm) Microsystems Integration 14

15 Feasibility Demonstrated in 2015 thermal resistance(k/w) R=ΔT/Q out R cu ref R TGP input power(w) 8mm 8mm 5cm Effective Thermal Conductivity (W/m-K) k eff =(R cu /R TGP )k Cu input power(w) 2.5cm Improved substantially with our partners. Microsystems Integration 15

16 Leading Vapor Chambers Microsystems Integration 16

17 Vapor Core Playing a Dominating Role with TGP Thickness Reduced to <0.25mm R a, vapor R e, mesh R c, mesh R e, Cladding Heat Source R a, mesh R a, cladding Heat Sink R c, Cladding 10cm x 5cm x mm 9.5 cm X 5 cm X 1mm Vapor core s contribution to the total thermal resistance of a TGP is dominant with thickness <0.25mm. It is due to significantly increased pressure drop of vapor transport along a very small gap. R c, Cladding R c, mesh R e, Cladding Re, mesh R e, Cladding R c, Cladding R c, mesh R e, mesh R a, vapor R a, vapor Vapor core s contribution to the total thermal resistance of a TGP is small with thickness >0.4mm Clausius Clapeyron relation Microsystems Integration 17

18 Vapor Core Thermal Resistance Vapor Thermal Resistance: A drop in pressure from viscous flow results in a drop in temperature (lower saturation pressure) affected by the gap of the vapor core: v. Viscous pressure drop in vapor-phase (Poiseuille s law): Vapor Transport: P vapor T vapor ~ 70 o C ~ 40 o C R a, vapor Temperature Difference: Heat Source Heat Sink Effective Thermal Conductivity of Vapor Clausius Clapeyron relation dp v /dt v = h v /T R vap = x/(k v w ) assumed Microsystems Integration 18

19 Understanding of Vapor Core s Role through Its Effective Thermal Conductivities Vapor transport 1.E+06 K vapor (W/mK) 1.E+05 1.E+04 1.E+03 1.E+02 1.E+01 Gap of Vapor Core = δ v =200 μm δ v =100 μm δ v =50 μm Gap and temperature dependent 1.E Vapor Temperature ( o C) 0.6mm <0.3mm Paradigm shift in design and manufacturing System specific TGP Microsystems Integration 19

20 Super-thin TGP Prototyping Polyimide (structure)/copper (sacrificial) layers ALD for hydrophilic coating and hermetic sealing Posts Mesh (wick) Vapor core 200 um Liquid channels 57 mm Microsystems Integration 20

21 All-Polymer Ultra-thin TGPs k eff (W/m K) Copper Feasibility proven enhancements Power (W) ~175 μm K eff >400 W/m K Microsystems Integration 21

22 ALD Atomic Layer Deposition A: Al-OH* + Al(CH 3 ) 3 Al-O-Al-(CH 3 ) 2* + CH 4 Trimethyl Aluminum (TMA) CH 3 Al CH 3CH3 CH 4 A) OH OH OH Al(CH 3 ) 3 CH Al CH 3 3 CH CH Al 3CH3 Al CH 3 3 OH OH OH B: Al-CH 3* + H 2 O Al-OH * + CH 4 H 2 O CH 4 B) CH Al CH 3 3 CH CH Al 3CH3 Al CH 3 3 OH OH OH Water H 2 O H 2 O OH Al CH CH OH OH 3 3 CH CH Al 3CH3 Al CH 3 3 OH OH OH Microsystems Integration 22

23 ALD Growth Rate Ellipsometer ALD Alumina Stylus Profiler on MEMS Al 2 O 3 Growth Rate = 1.29 Å/Cycle AB Cycles Microsystems Integration A typical laboratory setup for a typical process: Step A: Growth: 2 seconds Purge: 10 seconds Step B: Growth: 2 seconds Purge: 10 seconds Note: These numbers can vary significantly for different processes; they have been reduced by at least 10X for semiconductor processing and can be reduced further. 23

24 Wicking Test Vehicle w/o ALD Coating Microsystems Integration 24

25 Wicking Test Vehicle w/ ALD Coating Microsystems Integration 25

26 ALD-Based Moisture Barrier Coating (Steve M. George, CU-Boulder) 10 1 Polymer Film WVTR (g/m2/day) HTO test Permeation Rate ALD-on-Polymer Film 5X10 5 g/m 2 /day at 38 C/85% RH Carcia et al., JAP, Alumina ALD Thickness (nm) Microsystems Integration 26 26

27 Polymer film Polymer film Polymer film Polymer film Polyimide substrate Toughened ALD Coatings Al 2 O 3 can have a 1% strain. Nano-laminates improve to a 2% strain. New material improves to a 6% strain. Toughened ALD coatings to avoid cracking as shown 100 μm Critical strain Basic Al 2 O Thickness (nm) 2Γ Strain enhancement Nano laminates # of layers in NL Cracking strain New material Al 2 O 3 New material 6x improvement ALD thickness (Å) Microsystems Integration 27

28 Polymer Molecular Layer Deposition (MLD) (Steve M. George, CU-Boulder) 1,6-Hexanediamine for Nylon 66 H H N CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 N H H (A) Adipoyl Chloride for Nylon 66 Cl C O CH 2 CH 2 CH 2 CH 2 (B) O C Cl Microsystems Integration 28

29 MLD of Hybrid Organic-Inorganic Polymers: Alucones (Steve M. George, CU-Boulder) (B) Ethylene Glycol (A) Trimethylaluminum Microsystems Integration 29

30 Future 1-mm Thin and Flexible Smartphones? Glass or Polymer Cover; 0.05 mm 55-75µm thick chips OLED; 0.05 mm Chips (0.075mm) PCB TGP- Thermal Ground Plane (0.20 mm) Li Anode (0.075mm) Solid State Electrolyte (0.075mm) New Cathode (0.4 mm) K=300 W/mK K=5,000 W/mK Aluminum (0.05 mm) Polymer Case; mm Microsystems Integration 30

31 ALD-Protected Li-ion Batteries (Steve George and Se-Hee Lee at CU) 200 Specific Capacity / ma h g Al 2 O 3 -LCO 7-10µm 10Al-LCO 6Al-LCO 2Al-LCO b-lco SEI: solid electrolyte interphase Cycle Number Microsystems Integration 31

32 ALD Moisture Barrier Coating Packaging of Battery Electrode thickness C/LCO 100um 250um 500um 1000um 17 Layers 3900um 7 Layers 3000um 4 Layers 2800um 2 Layers 2600um Si/S 7 Layers 1400um 3 Layers 1000um 2 Layers 950um 1 Layer 850um 1400 mah x 3.7 V = 5180 mwh capacity 5cm x 4.4cm battery footprint Li anode (10X of C) 200µm thick case. SSE Cathode Microsystems Integration 32

33 Packaging and Thermal Management Challenges for Future 1-mm Thin Smartphones? Y. C. Lee, University of Colorado - Boulder Three CU technologies: Flexible thermal ground planes All solid state battery Atomic layer deposition Future Thin and Flexible Systems? Microsystems Integration 33