Technical Information Site of Power Supply Design

2022.11.24 Si Power Device

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

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

Compared with the previous PMDU package, the PMDE package has larger back electrodes even with the footprint that is about 40% smaller, for improved heat dissipation properties, and achieving heat dissipation performance equal to or exceeding that of the PMDU package, given appropriate PCB design. Moreover, in order to adequately take advantage of the heat dissipation performance of the PMDE package in a limited space, the settings of the copper foil area and thickness onto which mounting is performed are extremely important. These evaluation results have demonstrated that the PMDE package has important advantages for use not just in automotive equipment, but in various systems and devices with strict requirements relating to space limitations and low heat generation.

Below are links to each of the past articles and summaries of the important points therein.

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

Key Points of This Article

・The new "PMDE" package is a successor to the previous "PMDU" package.

・The PMDE package reduces footprint by roughly 40% from that required by the PMDU package, yet back electrodes about 1.5 times larger to secure comparable allowable dissipation of the package, while mounting strength is improved by a factor of 1.4.

Outer Shapes and Inner Structures of PMDE Package

Key Points of This Article

・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.

Heat Dissipation Performance of PMDE Package (Simulations)

Key Points of This Article

・In the PCB mounted state, as the copper foil area increases, heat is spread more readily, so that heat dissipation improves.

・If the copper foil area is too small, the PMDE Rth(j-a) value becomes larger than that for PMDU, and adequate heat dissipation is not exhibited.

・As the copper foil area increases, the PMDE heat dissipation performance improves, exceeding that of the PMDU package.

・The thicker the copper foil, the smaller the copper foil area at which the PMDE heat dissipation performance exceeds that of the PMDU package.

・If the copper foil area is made larger than necessary, the heat dissipation performance reaches saturation, and an effect equivalent to the area is no longer obtained. Hence an appropriate size should be chosen for the copper foil area.

Evaluation of PMDE Package in Actual Equipment

Key Points of This Article

・In these comparative evaluations, the PMDE package had a package temperature Tc and an efficiency comparable to those of the PMDU package, despite its compact size.

・It can be inferred that if efficiencies are similar, Tj values will also be similar, indicating that the PMDE package, while compact, exhibits heat dissipation performance similar to that of the PMDU package.

Lineup of SBD Products with PMDE Packages

Key Points of This Article

・The PMDE package is being adopted in numerous product types, particularly SBDs.

・Hereafter there are plans to use the package with FRDs, ZDs, TVS diodes, etc. as well.

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