Technical Information Site of Power Supply Design

2022.01.26 Si Power Device

Outer Shapes and Inner Structures of PMDE Package

Evaluation of PMDE Compact and Highly Heat Dissipating Package for Si Diodes

PMDE and PMDU Packages: Comparison of Outer Shapes

Below, the outer shapes of the PMDE and PMDU packages are compared. Compared with the PMDU package, the new PMDE package, despite footprint reduced by about 40%, has a back electrode area that is increased 1.5-fold, resulting in a package allowable dissipation comparable to that of the PMDU package, as well as a mounting strength that is increased roughly 1.4-fold.

Comparison of the Outer Shapes of the Conventional PMDU Package and the New PMDE Package

PMDE and PMDU Packages: Comparison of Internal Structures and Heat Dissipation Paths

Similarly to the conventional PMDU package, the new PMDE package does not use wires to electrically connect the element to the frame, but adopts a "wireless structure" in which the element is directly clamped by the frame. As a result, there is no longer the risk of wire fusion due to surge currents, so that a high surge current rating (IFSM) is realized. In the case of the lineup of SBDs described below, extremely large IFSM values of 20 to 30 A are guaranteed. Below, the internal structures and heat dissipation paths of the PMDE and PMDU packages are compared.


Comparison of the Inner Structures and Heat Dissipation Paths of the PMDE and PMDU Packages

In the PMDU package, because nearly the entire bottom surface is covered with molding resin, heat dissipation on the cathode side is mainly by horizontal heat conduction through the lead frame. In contrast, the PMDE package adopts a structure where the back electrode is greatly exposed, allowing a more direct and efficient heat dissipation to the PCB. Thus, care has been taken to ensure that the smaller size of the PMDE package does not result in a smaller allowable dissipation.

Key Points:

・The PMDE package has an allowable dissipation comparable to that of the PMDU package, while reducing the footprint by roughly 40%, and increase the mounting strength by 1.4 times.

・Due to the wireless structure, there is no risk of wire fusion caused by a surge current, so that a high surge current rating (IFSM) is achieved.

・Through greater exposure of the back electrodes, the PMDE package directly and efficiently dissipates heat to the PCB.

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