17/02/02 IMAPS Thermal Management La Rochelle

Transcription

1 17/02/02 La Rochelle Coupling Effects during Thermo- Fluidic Analysis of Flip-Chip Devices with Peripheral Components CFD Simulation and Experimental Study - Torsten Nowak - IMAPS Thermal TORSTEN.NOWAK@B-TU.DE Management 1

2 CONTENT 1. BTU? 2. Motivation for the topic 3. Parametric studies 4. Experimental setup 5. CFD modeling 6. Validation results 7. Summary and outlook 2

3 FACTS AND FIGURES Foundation: 1 st July 2013 Brandenburgische Technische Universität (BTU) Cottbus-Senftenberg students for research and near to technical applications About 21 % of the students came from more than 100 different countries Percentage of international students 208 Professors and Junior-Professors 645 Academic Employees BTU = Awesome buildings + state-of-the-art equipment + modern learning methods Library, Campus Cottbus 3

4 INTERNATIONAL CORRELATIONS The BTU actually cooperates with more than 235 partners in 49 countries. 4

5 FACTS AND FIGURES FACULTIES Department Electronic Circuit Technologies Prof. Dr.-Ing. Ralph Schacht Department Aerodynamics and Fluid Mechanics Prof. Dr.-Ing. Christoph Egbers 5

6 Motivation Source: ansys.com 6

7 Motivation Aim of this essential study are the knowledge of thermal impacts and action-related dependencies of Thermal conductivity of a Printed Circuit Board (PCB) coupled by Thermo-fluidic convection via fluid flow Temperaturedistribution? Fluid measurement and visualization?? Parametric analysis of thermal coupling effects in dependency of: Distances between components (d): 8 or 16 mm Different fluid flow velocimetry (v): 0 5 m/s Power losses of active thermal test dies (P v ): 0 4 W Different obstacles between active components Thermal conductivity of the PCB (λ): 4L or 2L Multiple test boards for rack system analysis (x n ) Possible obstacles 7

8 Design and possibilities of the test PCB 3 Thermal Test Chips (TTC), assembled in Flip-Chip (FC) technology 5 NTC s in SMD technology for board level temperature monitoring 130 mm NTC 5 NTC 4 NTC 3 3,2 mm 80 mm 24 mm Heating area d 16 mm Heating area 16 mm NTC 2 Solder pads T sens Heaterstrings 3,2 mm Fluid flow direction T-Sensor position TTC 1 TTC 2 TTC 3 NTC 1 1x TTC cell Possible position for an fluid flow obstacle Card edge connector for TTC T-measurement Card edge connector for TTC heating and NTC T-measurement 8

9 Schematic sketch of the test assembly in wind tunnel measurement section (cross section) (top view) The TTC data measurement and heating control will be realized by in-situ monitoring by LabVIEW with external trigger box 9

10 Experimental setup in wind tunnel IR Cam control IR-Cam 1 m Air inlet Fan speed control Contraction 0,3 m Measurement section Diffusor Ventilator 0,6 m DAQ / Electronic Sensor / heat control 4 m CONNECT, Stokes Laboratories, University of Limerick, Limerick, Ireland 10

11 Experimental setup in wind tunnel - Measurement section - IR-Cam Test board IR transparent window PCB holder View through honeycomb filter inlet PCB holder PCB test board PCB holding system with card edge connectors (capacitor as an obstacle instead of TTC2) Measurement section of the wind tunnel system IR measurement with adopted emissivity (black varnish, ε = 0.92) on PCB test surface (capacitor as an obstacle instead of TTC2) 11

12 Particle Image Velocimetry / PIV Measurement of particle motion, not fluid motion! Source: 12

13 Particle Image Velocimetry / PIV - Setup and first results - PIV flow visualization Lens Leading edge Bubble Camera PCB PIV vector plot Laser Lens Laser sheet (low fire) TTC 1 TTC 3 5 m/s Thermal boundary layer (laminar flow) Leading edge TTC 1 TTC 2 Measurement and resolution of fluid flow near thermal boundary layer of TTC2 13

14 MODELING 14

15 300 mm CFD modeling Measurement section, dimensions, boundary conditions Outlet p = 0 Pa Wall T = 298 K (const.) Name x [ mm ] y [ mm ] z [ mm ] FR TTC P V Volume TTC Solder bump (Cu + SnAg) UF / Solder bump volume Wind tunnel / measurement section PCB holder Fluid flow help (center) 20 0 v = 0 4 m/s Inlet Name Ambient temperature (wind tunnel walls) Outlet pressure Inlet velocity (T = 298 K) Distance between TTC s Distance from PCB-edge to TTC1 value 298 K 0 Pa 0 5 m/s 8, 16 mm 24 mm 15

16 CFD modeling PCB dimensions, material data Material Thermal Conductivity [W/mK] PCB card holder and PCB dimensions FR4-4L Cu (x / y / z) 17.4 / 17.4/ FR4-2L Cu (x / y / z) 0.8 / 0.8 / 0.3 Air (25 C) FR4 (x / y / z) 0.8 / 0.8 / 0.4 Under fill (UF) 0.63 SnAg 52 Cu (galv.) 300 Cu 380 Si 150 UF_SodlerBump,eff 3.82 PCB holder mm PCB cap PCB card carrier (acryl glass) 16

17 CFD modeling PCB solder bumps and under fill Chip (Si) Power loss in this thin Si Contact as thin layer modeled (100 µm), volume (16 x 16 x 0.1 mm³) Instead of under fill layer with tiny solder balls (30 µm) 0.57 mm 0.1 mm 1.6 mm PCB (FR-4) PCB-, TTC- dimensions as cross section Power loss will be generated in thin silicon die (active area to bottom) in a separate volume The solder bump / under fill volume will be modeled as thin layer (100 µm) 17

18 CFD modeling Mesh setup and boundary conditions Mesh: A total number of 9,329,078 elements (Tetrahedral for the wind tunnel, Wedges and Hexahedral for PCB, -holder) as 2,451,995 nodes were required. The fluid properties were set to: Morphology Continuous Fluid for Air at 25 C Heat transfer Thermal Energy incl. Viscous Dissipation Turbulence option Shear Stress Transport, Automatic wall func. 18

19 CFD results - Flow contour plot / distribution in wind tunnel - Flow velocity distribution of wind tunnel: air direction flow from left to right 19

20 CFD results, example PCB test design 4L8-A/B P D,TTC1 = 2.5 W, v = 1.43 m/s Without obstacle Velocity [m/s] TTC2 Temperature [K] TTC2 Capacitor 2 h = 11 mm d = 8 mm h = 11 mm d = 8 mm Capacitor 3 h = 15 mm d = 13 mm h = 15 mm d = 13 mm 20

21 Simulation results Example with capacitor T TTC [K] Pv,TTC1 = 2.5 W w/o cap cap2 cap3 Capacitor dimensions Height [mm] Diameter [mm] PCB test design 4L8 v [m/s] T cap /T w/o_cap [%] Pv,TTC1 = 2.5 W v [m/s] cap2 cap3 ~10 % 21

22 Comparison between simulation and experiment PCB test design 4L8-B T TTC [K] TTC1-Sim TTC1-Exp TTC3-Sim TTC3-Exp P V,TTC1 [W] v = 1 m/s Example with capacitor: The increase of obstacle size have an influence by temperature reduction of nearby TTC s. Convective heat transfer by fluid flow (air) is reduced. Only conductive heat transfer along the PCB board have temperature influences from TTC1 to TTC3. 22

23 Summary / Outlook Development of analytical model equations for thermo-fluidic coupling effects with consideration of interferences of peripheral components between in FC technology assembled unhoused bare dies Validation of experimental and numerical data for calculation of thermo-fluidic factor 23

24 Thank you for your attention!

25 Laboratories Aero- and Fluid Dynamics 07 Aero Dynamics and Fluid Mechanics in Cottbus

26 Faculty 3 Chair of aerodynamic and fluid mechanics campus Cottbus Prof. Dr.-Ing. Christoph Egbers Wind tunnel Göttinger setup: - Section of measurement A = 0,6 m x 0,5 m (rectangle) - closed / open for PIV/LDA - Velocimetry U max. = 50 m/s (closed measurement section) - Rated speed U rs. = 40 m/s ± 0,1 m/s - Intensity of turbulence: Tu < 0,1 % For fluid visualization and measurement methods (e.g. LDA, PIV) a three way optical access for the measurement section will be necessary. Address for Visitors Building 3A Siemens-Halske-Ring Cottbus / Germany Lab Laboratories 3D Siemens-Halske-Ring Cottbus / Germany 26