Thermal Testing and Analysis of On-the-Market Smartwatches

The smartwatch is rapidly becoming one of the most popular consumer electronics devices on the market. Tech giants such as Apple, Samsung, and Google are releasing new products each year with upgrades that include health monitoring, water proofing, crash detection, and more. The smartwatch industry had a market size and share of 28.5 billion dollars in 2021. It is expected to grow to 80.1 billion dollars by 2028.Thermal management plays a key role in the design and safety of wearable devices. Wearables need to be able to process large amounts of information. This can lead to periods of high-power dissipation. Since the smart watch is in direct contact with the skin, the temperature has to be carefully controlled. If the power dissipation of a smartwatch is not managed correctly, it can cause discomfort or harm to the wearer.Large companies are struggling to successfully address the thermal design requirements of these products. On March 2, 2022, Fitbit announced a recall of its Ionic smartwatches. Their recall notice cautioned that the battery within the watch was prone to overheating and could cause a burn to its users. In September of the same year, some users reported that their Samsung Galaxy Watch 2 gave them 3rd degree burns while they were sleeping.This presentation analyzes the thermal design of various smartwatches on the market by performing thermal testing, teardown, and thermal modeling simulations. The simulations were done using Siemens’ Simcenter FloEFD software. This effort was coordinated with Siemens to demonstrate the capabilities of the Siemens FloEFD CFD software.The smartwatches chosen for this study were the Apple Watch Series 8 and the Samsung Galaxy Watch 5. These products are representative of the latest and most advanced designs from two of the world’s leading technology companies. These products are also of interest as they can monitor heart rate, electrocardiogram, blood oxygen, and skin temperature. Each of these products also have access to an extensive library of apps. These apps allow for a variety of use cases that can be replicated in a lab setting.First, these smartwatches will go through thermal testing for different use scenarios with thermocouples applied to different points of interest, such as the battery, human contact points, and the main processor. Then, the smartwatches will go through a teardown process to weigh and measure each individual component of the device. Finally, a 3D CAD model will be built with appropriate material and thermal properties, using the results of the teardown and testing. Since access to precise power dissipation data is unavailable, the temperature profiles of the device for different use cases were used to estimate component power dissipations. After the modeling was completed, Simcenter FloEFD was used to perform CFD simulations.Comparison of the results of simulation and testing enables the authors to understand how the design of each smartwatch dissipates heat and which design features function better.