How to use Thermal Design Software

1. How to use Thermal Design Software Paul Rose European Electronics AE Manager LuxLive 2013

2. Design Challenges in Electronics Design Figure 1 : Junction Life Statistics (Source : GEC Research) • Overheating is the major reason for electronics failures • There is a need to remove the heat generated by the electronic components. • Whether or not using mechanical means PMR, Fast and Accurate Predictability of CFD Thermal Analysis for PCB Design, June 2010

3. Design Challenges in Electronics Design • Working against us… • Moore’s Law (increasing power) • Increased functionality • Reduce size • Reduce noise • Increase reliability • Constrictions of manufacture PMR, Fast and Accurate Predictability of CFD Thermal Analysis for PCB Design, June 2010

4. Design Challenges in Luminaire Design • Junction temperature directly impacts light efficiency. • Heat transfer paths have changed: • Challenge is to ensure sufficient conduction to the environment. Light Light & Heat TJ = 2000+ ˚C TJ = 50 - 100 ˚C Heat

5. Thermal analysis of Electronics Concept Detailing Final Design Testing CFD CFD CFD • Could employ physical testing • Cost of redesign / testing • Over engineer to avoid possibility of failure • Use numerical computer based virtual testing which is where Computational Fluid Dynamics comes into play Concept Detailing Final Design Testing CAD CAD CAD CAD Manufacture Prototype Prototype Prototype CAD Manufacture 5

6. What is CFD? • From a text book (Versteeg & Malalasekera, “An Introduction to Computational Fluid Dynamics: The Finite Volume Method”) • “Computational Fluid Dynamics or CFD is the analysis of systems involving fluid flow, heat transfer and associated phenomena, such as chemical reactions by means of computer-based simulation”

7. What is CFD? • In Pictures…

8. What is CFD? • 18th and 19th Century many eminent scientists carried out research to mathematically describe the motion of Fluids: • Daniel Bernoulli (1700 – 1782) • Leonhard Euler (1707 – 1783 • Claude Louis Marie Henry Navier (1785 – 1836) and George Gabriel Stokes (1819 – 1903) • Navier Stokes equations forms the basis of modern day CFD – based around conservation laws • Late 20th Century and beyond… • Research to create numerical methods to solve the basic equations • A number of general purpose codes developed and marketed • Computer power increasing allowing more accurate analysis to be performed

9. Analysis Process • Create geometry • Create an analysis project

10. Analysis Process • Add thermal properties / heat sources / environmental conditions • Look at the results….

11. System Analysis

12. System Analysis

13. A System Level Problem Max. Allowable Junction temperature Available Headroom PCB Heat sink Air Ambient temperature • Helpful to think in terms of ‘thermal headroom’ LED Package Vendor Designer’s job is to decide how to split up the temperature rise from ambient to case System Designer

14. “Thermal Head Room” Acceptable LED Temperature = 70.0°C Predicted LED Temperature = 65.1°C Available Headroom 4.9°C

15. Design Challenge Heat flow from device to Heat Sink Heat flows within Heat sink to its surface Transfer from Surface into surrounding air

16. Design Challenge Surface Area Alter Number of Fins Transfer from Surface into surrounding air Aerodynamics

17. Heat Sink Design Changes

18. Heat Sink Design Changes

19. What about the components active layer to submount classical die attach (TIM1) solder/glue to MCPCB • Can use simulation to investigation component level thermal performance… • …but also transient measurement techniques can accurately characterize the LED classical TIM to heat-sink (TIM2) System-Level Thermal Management of LEDs John Parry & Paul Rose, 07 July 2009

20. Role of Physical Testing • Combined thermal and radiometric characterization: T3Ster + TERALED

21. Your Initials, Presentation Title, Month Year

22. Completing the Circle • Characterization of the LED from the physical test can be used in the simulation software…

23. Final Thoughts… • Thermal analysis should be an integrated part of the design process to: • Optimise thermal performance at the earliest possible stage • Prevent over engineering required to sort out problems that occur at a late stage of the design • Design a system that you know will work • Stand G42 “FloEFD from Mentor helps us to understand and optimize headlamps. Even very complex geometries and test conditions can be investigated with a minimum of effort.“ Peter Jauernig, Head of Department Automotive Lighting http://www.mentor.com/products/mechanical