In high-current output LLC converters, the design and optimization of the termination layout are critical. For applications with high thermal dissipation requirements, such as situations with multiple times overload requirements, numerous vias are often needed to connect components to the heatsink on the bottom side. These vias traverse the PCB, presenting new challenges for PCB layout. Based on a 300 kHz 270 V/28 V LLC converter with a planar transformer, this paper improves the design by switching from a lateral to a vertical termination structure. Simulations and experiments demonstrate the vertical structure's benefits in current distribution and thermal management, resolving uneven current distribution and excessive output capacitor temperature, resulting in a more stable converter and increased efficiency.