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Design007-Nov2021

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30 DESIGN007 MAGAZINE I NOVEMBER 2021 e growing popularity of wide bandgap (WBG) semiconductors, such as gallium nitride (GaN) and silicon carbide (SiC) has enabled components to achieve higher operat- ing temperatures and power outputs than sil- icon-based technology. However, this has not eliminated the need for careful thermal man- agement to evenly distribute the heat gener- ated to avoid the formation of dangerous hot spots and to minimize power losses. e heat generated by integrated circuits (Figure 1) poses great challenges, especially given today's higher speeds, smaller board surface areas, and multiple devices populated on PCBs. ese Impact of Filled Vias on Thermal and Signal Integrity demands call for solutions to effectively dis- sipate the heat and ensure the performance and lifetime of the electronic system product. One solution is to use copper filled vias which complement thermal management, but how do filled vias affect signal integrity? e conventional plating process cannot close the via completely—there is always an air gap in the middle. icker barrel plating improves the thermal transfer and current-car- rying characteristics of vias at DC and low fre- quencies. IPC-4761 Design Guide for Protec- tion of Printed Board Via Structures Standard covers via fabrication and protection. ere are seven categories, but just three basic types: 1. Tented via. 2. Plugged via. 3. Filled via. All three via types can also be covered (on both sides); how- ever, the filled via may also be capped. Capped vias are gener- ally used for via-in-pad applica- tions to prevent paste or resin flowing down the hole—the surface is planar and solderable. Typically, vias are plated over with electroless nickel immer- sion gold (ENIG). However, if via-in-pad is used, then ensure the connection to the planes uses thermal reliefs or you'll Beyond Design by Barry Olney, IN-CIRCUIT DESIGN PTY LTD / AUSTRALIA Figure 1: Thermal simulation of hot spots on the bottom of the PCB. (Source: Siemens EDA)

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