Modular semiconductor power device

Details Modular semiconductor power device Modular semiconductor power device

1994-01-21

2003-03-18

Chaudhuri, Olik (Department: 2814)

Active solid-state devices (e.g., transistors, solid-state diode

Lead frame

With structure for mounting semiconductor chip to lead frame

C257S762000, C257S771000

Reissue Patent

active

RE038037

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a modular semiconductor power device and to a device as obtained by such method.
BACKGROUND OF THE INVENTION
In the manufacture of modular semiconductor power devices, as in the manufacture of numerous other components, an important target is to produce extremely reliable products using simple and inexpensive procedures.
The known semiconductor power devices involve complex and costly procedures, both from the point of view of the individual components necessary for constructing them and from the standpoint of their assembly and reciprocal insulation.
Some of these known devices are described in the U.S. Pat. No. 4,518,982. This patent gives a detailed description of a modular power device whose manufacturing process consists of soldering one or more semiconductor chips onto a flat portion of a first electrode (which also serves as a heat sink), soldering other electrodes (possibly containing other chips) onto the flat portion by means of a dielectric adhesive material, electrically connecting the various chips and electrodes, encapsulating the device in resin, and electrically insulating the heat dissipating surface by means of a further layer of insulating material.
OBJECT OF THE INVENTION
The object of this invention is to provide a particularly reliable modular power device obtained by means of an extremely simple and not very expensive assembly procedure, according to a highly flexible manufacturing method and with components which, although extremely limited in number, can be used to create various circuit arrangements and layouts, always using the same tools and always maintaining an identical external geometrical configuration of the devices obtained.
SUMMARY OF THE INVENTION
According to a particular feature of the manufacturing method, the reciprocal insulation of the electrodes and their encapsulation are carried out in a single step. The manufacturing method according to the invention for making a modular semiconductor power device comprising one or more semiconductor chips, a metal plate for dissipating heat generated by the Joule effect, a plurality of electrodes constituting the signal and power terminals of the device, and a resin encapsulation, comprises:
soldering the chip or chips onto one or more plates of electrically conductive material;
positioning the plate or plates on a plane substantially parallel to the aforesaid heat dissipating plate and close to the latter;
blanking, from a single sheet of conductive material, a one-piece frame designed to constitute the power and signal terminals, the blanking enabling temporary connections to be kept between the portions of the terminal conductors designed to remain outside of the resin encapsulation;
soldering the inner ends of the terminals to points arranged for the connection to the aforesaid chips;
encapsulating with insulating resin all the active parts of the device, leaving uncovered the outer surface of the plate and the portions of the terminals involved with the aforesaid temporary connections; and
shearing the temporary connections.
Each sheet can be made of copper and
that
the latter, before the chips are soldered onto it, can be placed in a plate consisting of three layers soldered directly onto each other, in which the first layer is made up of the sheet and copper strips insulated from the sheet itself. The intermediate
layer
consists of an alumina plate and the third layer consists of a sheet of copper substantially equal in size or slightly smaller than the intermediate layer. The
aforesaid
points of connection are situated on the aforesaid sheets and strips, the soldering of the inner ends of the terminals to the aforesaid points is preceded by soldering of wires connecting the chips to the aforesaid strips.
The sheet can be soldered onto the internal surface of the plate and the connections between chips and strips can be made by means of ultrasound soldering of aluminum wires.
The aforesaid points of connection with the chips can be located on the
foresaid

aforesaid
sheets and on wettable metal coatings on the surface of the chips.
After blanking of the one-piece frame and before the aforesaid soldering of the inner ends of the terminals to be points of connection, the inner ends of the terminals can be bent in a direction perpendicular to the plane of the frame.
After the encapsulation and the shearing of the temporary connections of the one-piece frame, the terminals designed to perform the function of signal terminals can be bent in a direction perpendicular to the base plate, while the terminals designed to perform the function of power terminals can be bent over the capsule in a direction parallel to the base plate itself.


REFERENCES:
patent: 4396936 (1983-08-01), McIver et al.
patent: 4518982 (1985-05-01), DuBois et al.
patent: 4615031 (1986-09-01), Eales et al.
patent: 5038198 (1991-08-01), Perniciaro Spatrisano et al.

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