Leadframe with heat dissipator connected to S-shaped fingers

Abstract

An improved leadframe for packages of integrated power devices which, by virtue of its configuration, allows to press the dissipator on the bottom of the shell during the molding of the plastic case, without the dissipator having exposed portions of its inner face (which is in contact with the chip). In order to achieve this, the leadframe according to the invention comprises a monolithic body which defines a perimetric frame, the leads and the dissipator. The dissipator extends in a depressed plane with respect to the frame and is connected to the frame and to the leads in at least three step-like points which are mutually spaced and non-aligned. During the molding of the plastic case, a pressure is exerted on the frame and is transmitted to the dissipator by the three step-like points, so that the dissipator is effectively pressed flat against the bottom of the mold without using pushers which pass through the plastic case.

Description

BACKGROUND OF THE INVENTIONThe present invention relates to an improved leadframe for packages of integrated power devices. In particular, the present invention is related to medium-power integrated circuits.As is known, in the manufacture of integrated power devices, the chip of semiconductor material which integrates the electronic components is welded to a dissipator which is connected to a leadframe. Generally, the dissipator, which is thicker than the leadframe and is arranged on a different plane, is manufactured separately and is connected mechanically to the leadframe so that its face which is to be welded to the chip is directed toward the leads. Then, after the provision of the interconnections between the chip and the leads or terminals, a plastic case of epoxy resin, with a generally parallelepipedal shape, is molded on one face of the dissipator and completely embeds the chip. In particular, the plastic case only partially covers the face of the dissipator which is in c...

AI Technical Summary

Benefits of technology

Within the scope of this aim, a particular object of the present invention is to provide an improved leadframe which has such a configuration that no pushers which pass through the resin and cause interruptions therein are required during the molding of the plastic case.

In particular, an object of the present invention is to provide a leadframe by virtue of which, after the molding of the plastic case, the inner face of the dissipator which is in contact with the chip is completely covered by the resin, so that it is protected against external contaminating agents, avoiding thus the deposit of resin residues on the outer side of the dissipator.

An important object of the present invention is to provide a leadframe which allows to obtain a significant simplification in the mold for the plastic case, with a reduction in manufacturing costs.

Problems solved by technology

However, this solution is disadvantageous.

However, the exposure of even only part of the inner face of the dissipator is unwanted, since said face is not protected against external influences during the further manufacturing steps (e.g. nickel-plating for the coating of the leads), and in particular it facilitates the penetration of humidity inside the package, reducing the life and therefore the reliability of the device.

Due to the presence of the pushers, the mold furthermore has a relatively complicated and therefore expensive configuration.

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