Top Cool Package for Power Discrete MOSFETs AND90190/D

Introduction

In power applications, the majority of MOSFETs utilized tend to be surface mount devices (SMD). Some package examples include SO8FL, u8FL, and LFPAK. These SMDs are usually selected due to their power capabilities while maintaining a compact size. This in turn, allows for a more compact application solution. Although these devices have good power capabilities, the heat dissipation is not ideal because the heat propagation is mainly through the PCB.
The heat flows through the board because the lead frame of the device, including the exposed drain pad, is soldered directly onto a copper footprint. The rest of the device is enclosed in mold compound and cooled only through air convection. The efficiency of heat transfer is then largely dependent on the board properties: Cu plane size, Cu layers, Cu weight, and Cu layout. This is the case regardless of the board being mounted to a heatsink or not.
Due to this, the maximum power capability of the device is not optimal since PCBs don’t generally have high thermal conductivity and thermal mass. To counter this issue and to improve on application size even further, a new MOSFET package has been developed which exposes the lead frame (drain) of the MOSFET on the top side of the package.