Application of Aluminum Flat Heat Pipe for Dry Cooling Near the Hot Spot of a Radar Array with a Multiscale Structure

Power amplifiers used for high-speed radio frequency (RF) consume a considerable amount of power and create thermal burden. The heat flux per module of power amplifiers that are based on gallium nitride (GaN) component devices, which have recently entered maturity in the market and shown excellent RF power output, is approximately 190 W/cm(2), thereby causing thermal management burden. When the number of arrays increases, and the power consumption is large, liquid cooling methods, such as maximizing cooling performance by optimizing the liquid flow path design or designing the cooling liquid line as close as possible to the heat source in the power package module, are mainly considered. However, the close contact of the liquid lines to the heat source may form a dewdrop in the package module, thereby decreasing reliability, especially in a radar system with power array modules. As an alternative, dry cooling methods that use heat pipes have been investigated. However, radar array package modules have not elicited much research attention. In this study, an aluminum flat heat pipe (AFHP) was developed for a 1 x 4 3D array module for the RF power amplifier of the next-generation X-band radar. This module is lightweight and is based on aluminum material, has a flat shape, and facilitates antenna interconnection through its hole structures. Subsequently, an AFHP with an antenna interconnection structure was designed and fabricated. Moreover, the temperature limit in the GaN power device and the temperature distribution in the entire package module were evaluated by testing the 1 x 4 antenna array module structure at 193 W/cm(2) of heat flux per module. The results obtained in this study could confirm the possibility of using AFHP as a dry cooling method to high heat flux application.