Automotive
New range of Top Cool N-Channel MOSFETs
onsemi has developed a range of Top Cool devices that are housed in a modified LFPAK 5x7 package measuring just 5mm x 7mm. Designated the TCPAK57, the new Top Cool package features a 16.5mm2
the top side, allowing heat to be dissipated directly into a heatsink.
Figure 3: The initial Top Cool portfolio comprises seven devices
compared to conventional heatsinking via a PCB, thereby delivering a better thermal response.
In addition to improved thermal
conductivity, heatsinks provide a much greater thermal mass which helps avoid saturation, providing a longer thermal time constant as the top mounted heatsink can be sized to suit the application needs.
Given the benefit of being directly attached
to a high thermal mass heatsink, the Top Cool package will have a better thermal response, measured as temperature rise per Watt. This enhanced thermal response allows for higher power operation for a given junction temperature increase.
Ultimately, the same MOSFET die packaged in a Top Cool package will have higher current and power capability than the same die placed in a standard SMD package.
Internally, the TCPAK57 devices feature a copper clip for the source and drain connections. This replaces the wire bonds and allows conduction of large currents with minimal resistance, as well as an effective thermal connection to the top side pad. The new devices deliver the electrical efficiency required in high power applications with RDS(ON) values as low as 1mΩ.
This solution leverages onsemi’s deep expertise in packaging to provide the highest power density solution in the industry. The TCPAK57 initial portfolio includes a total of seven devices, rated at 40V, 60V and 80V. All devices can operate at junction temperatures (Tj) of 175°C and are AEC-Q101 qualified and PPAP capable. This, along with their gull wings that allows inspection of solder joints and superior board level reliability, makes
thermal pad on
them ideally suited to demanding automotive applications. The target applications are high/ medium power motor controls such as electric power steering and oil pumps. The Top Cool TCPAK57 devices provide increased power density and the improved reliability of the new design adds to an extended overall system lifetime.
Summary
Managing heat in power designs is fundamental to achieving the challenging design goals that exist in the automotive industry. Conventionally, cooling discrete power devices such as MOSFETs involved passing thermal energy through the PCB to a heatsink. However, this is not an ideal thermal path and, consequently, device performance was hampered.
However, a new package style moves the thermal pad to the top, thereby allowing a heatsink to be bonded directly to the device. Not only does this improve cooling of the MOSFET, it also allows the underside of the PCB to be used for component placement, thereby increasing power density in critical applications such as automotive.
https://www.onsemi.com/
www.cieonline.co.uk.
Components in Electronics
February 2023 17
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