THERMAL DESIGN PARAMETERS and SIGNIFICANCE OF SPREADING IMAPS 2015 Sept, 2015 Bharath Nagendran*, Arun Raghupathy, and William Maltz Electronic Cooling Solutions Inc. * [email protected] 1 Outline Recent trend in consumer electronics Tablet construction / teardown Quick overview of earlier work Spreading enhancements in forced convection tablet Use of blowers and outer surface spreading Experimental study : Baseline and Spreading enhancements Results Use of blower : Impact on battery life Use of blower : challenge miniaturization Thermal Design and impact on tablet weight 2 Tablet Construction / Teardown Heatpipes and blowers CPU and GPU Batteries Rear case 3 Quick overview of earlier work Airflow measurement Blower Teardown characterization Thermal IR imaging characterization 4 Quick overview of earlier work T3ster characterization Acoustic measurement 5 Quick overview of earlier work Construction of a CFD model in FloTherm XT 6 Use of blowers and outer surface heat spreading Outer Surface Heat Spreading Use of Blower Blower Speed Max. Surface Temperature Hot spots Blower noise to users Effective outer surface spreading Mic. Disruptions due to blower operation Blowers, heat-pipes, heat exchanges add weight Battery Isolation Max. battery temperature Blower Plenum Blower is effective with adequate plenum, but Weight increases tablet thickness Material selection of outer surface Battery Life Use of graphite spreader Blowers add parasitic load to the already short battery life Reliability Moving parts creates higher possibility of failure 7 Experimental Study : Heat spreading configurations Case 1 Case 2 Baseline With Spreading enhancements TIM Connected to rear case Graphite spreader + Blowers and Conduction path through TIM Magnesium rear case between heat-pipe and rear case 8 CPU and GPU temperatures CPU Temperature GPU Temperature GPU Temperature normalised to ambient CPU Temperature normalised to ambient 70 70 65 65 60 60 55 55 50 50 45 45 40 40 35 35 30 30 25 25 GPU CPU Baseline (case 1) with Blower @ 3900 RPM Baseline (case 1) with Blower @ 8900 RPM Enhanced Spreading (case 2) with Blower @ 3900 RPM 9 Max. outer surface temperature and battery temperature Max. Battery Temperature Max. Surface Temperature 50 50 45 45 40 40 35 35 30 30 25 25 Max. outer surface temperature Max. Battery Temperature Baseline (case 1) with Blower @ 3900 RPM Baseline (case 1) with Blower @ 8900 RPM Enhanced Spreading (case 2) with Blower @ 3900 RPM 10