Understanding Thermal Analysis of GaN

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Understanding Thermal Analysis of GaN [Copy link]

https://training.eeworld.com.cn/course/5120/learn?preview=1#lesson/19780 The system's requirements for amplifier output power are getting higher and higher, which has promoted the development of technology. But with the introduction of new technologies, new challenges will also arise. In this article, we will talk about the thermal analysis of GaN RF devices. The following is the text content of the video: To understand the analysis of GaN heat, first let's understand how Qorvo determines the thermal reliability of GaN. The infrared camera will not tell you the actual peak temperature of the GaN transistor. The infrared image only measures the surface temperature of the device. However, the actual peak temperature of the device is below the surface of the GaN epitaxial layer. In addition, the length of the GaN gate is generally only 0.25 or 0.15 microns, while the resolution supported by the infrared camera is only 3-5 microns. Qorvo determines the channel temperature by building a 3D thermal model or finite element analysis (also known as FEA), and uses microscopic slow thermal imaging technology to obtain empirical measurement results for comparison, and then verifies it through RF testing and infrared imaging. Since the biggest uncertainty in the FEA model of the product comes from the die mounting. Therefore, Qorvo conducts a large number of tests and compares the ice and rain benchmark values to determine the die mounting characteristics of a given package. We use this combined method to build an FEA model for the packaged component. Through this model, the maximum channel temperature under given operating conditions is accurately estimated, and the estimated value is compared with the GaN period reliability table based on measured microscopic slow data. The other three thermal considerations are the backside temperature, die or product mounting, and PC board design. The thermal reference surface of the packaged product is the backside of the package. For delayed die, we assume that it is mounted on a copper-molybdenum carrier board using gold-tin solder. The fixed temperature thermal reference surface of the die is the backside of the carrier board. For detailed information on product mounting methods and PC board design, please refer to the data sheet, application notes or consult a local application engineer. For PC board design details, please download the Gerber layout files, which can be found under the Documents tab on the device page. This method will replicate the evaluation board as closely as possible, especially the footprint layout, using the QPD1022 data sheet. Let's first determine the IR surface channel temperature. We will use this data for continuous wave applications to determine the IR surface channel temperature. We need to know the device case or Tbase temperature and power dissipation. For continuous wave applications, the data sheet shows thermal performance at a backside temperature of 85 degrees. If you need to measure the base temperature, measure the backside of the device. When measuring, it may be helpful to use a thermocouple. The power dissipation we will use is 7.6W. If the power dissipation is not given in the data sheet, use the calculator provided by the Qorvo Design Center to calculate it. For continuous wave power dissipation of 7.6W and a backside temperature of 85 degrees, follow the graph above the table. The IR surface channel temperature is 132 degrees. Use the same graph to calculate the IR surface channel temperature for your specific application. Now, let's calculate the MTBF of the GaN device. Because the actual channel temperature of the GaN device will exceed the IR surface channel temperature value, we use the FEA model data to calculate the MTBF. To determine the channel temperature of the FEA model and the MTBF of the device, you may need to consult the application note. Please click the link in the data sheet to view it. Use Figure 6 in the application note to calculate the estimated value of the FEA model. The IR surface temperature is 132 degrees and the substrate temperature is 85 degrees, which is equivalent to the maximum channel temperature of the FEA model of 155 degrees. Finally, use Figure 5. Note that in this step, you need to link the GaN process technology QPD1022 is GaN25, its channel temperature is 155 degrees, and the FEA MTBF is 1 billion hours. If your application provides a pulse signal at a 20% duty cycle, then your FEA MTBF is 5 billion hours. In summary, to accurately determine the MTBF of a GaN FEA device, you must determine the IR surface channel temperature and then determine the reliability of a Qorvo GaN device as described in the application note. Visit the Qorvo Design Center for tools, eBooks and blogs. We solve your toughest RF challenges.

月下良缘

Thanks for sharing!