Plastic package type semiconductor device

Abstract: A plastic package type semiconductor device comprises: a die pad (10) consisting of a plurality of parts; a tab lead (20) consisting of a plurality of parts holding the die pad; a flat type jumper lead (70a) formed between the parts of the die pad; an electrical insulating type insulating film (15) formed on the die pad; a semiconductor chip (30) bonded on the insulating film by an adhesive; and a plastic mold as a plastic package for molding the die pad, the tab lead, the flat type jumper lead, the insulating file, and the semiconductor device in the plastic mold, whereby the semiconductor chip is insulated electrically from the die pad. In addition, a SOJ plastic package type semiconductor device has a configuration without the jumper lead described above.

Description: BACKGROUND OF THE INVENTION 1.Field of the Invention The present invention relates to a plastic package type semiconductor device, and, in particular, to a plastic package type semiconductor device comprising a semiconductor chip and a die pad section (also referred to as a bed section) mounted in close contact on an insulating film by the formation of the film on the die pad inside an lead frame to electrically insulate from each other. 2.Description of the Prior Art FIG.1 is a plan view of a lead frame contained in a conventional plastic package type semiconductor device. FIG.2 is a sectional view showing the structure of the conventional plastic package type semiconductor device viewed along the section A - A' in FIG.1. As shown in the drawings, a die pad 1 is provided on which a semiconductor chip 3 is loaded. Also provided are a plurality of tab leads 2, specifically, tie bars, and a jumper lead 7b. As shown in FIG.2, the jumper lead 7b is formed in a U-shape to maintain the electrical resistance of the semiconductor chip 3. A bonding wire 9, an insulating adhesive 5 for electrically insulating and bonding the die pad 1 to the semiconductor chip 3, and a plurality of inner leads 4 are also provided. In addition, the die pad 1 is divided into two parts by the jumper lead 7b. The surface of the die pad 1 is normally silver plated. An insulating adhesive 5 is used to bond the semiconductor chip 3 onto the die pad 1. During the process of attaching the semiconductor chip 3 to the die pad 1, unbonded regions such as voids are formed in the insulating adhesive 5 used for bonding. When a semiconductor device containing such unbonded regions is used for a long period of time, the silver plating on the die pad 1 migrates into the voids in the insulating adhesive 5 and eventually reaches the under surface (the surface bonded to the insulating adhesive 5) of the semiconductor chip 3. The problem therefore arises that the electrical insulation between the die pad 1 and the semiconductor chip 3 is broken down by corrosion. In addition, in surface mounted type packages such as an SOP (Small Outline Package), an SOJ (Small Outline J-leaded Package), and the like, as shown in FIG.3, there are cases in which cracks are produced in the package from VPS (Vapor Phase Soldering) reflow, IR (Infrared Ray) reflow, and the like. These cracks are caused by the absorption of moisture by the package so that steam is formed from heating during reflow, creating sufficient force to form cracks in the package. The following problems are also associated with the conventional plastic package type semiconductor devices. Taking a TSOP (Thin Small Outline Package) as a typical example, the thickness of the package has been reduced to the point where, at the present time, a thickness of as low as about 1.0 mm can be provided. Specifically, FIG.4 shows the cross sectional configuration of a TSOP in which the thickness A of the plastic mold is 0.28 mm, the thickness B of the semiconductor chip is 0.35 mm, the thickness C of the conductive adhesive is 0.05 mm, the thickness D of the lead frame is 0.15 mm, and the thickness E of the plastic mold is 0.17 mm. The total thickness F of the package is therefore 1.0 mm. However, when the package is to be used as a bank cash card or the like, a thickness of 0.8 mm or less is desirable. A problem therefore exists in that a semiconductor chip with a conventional structure cannot be used for a bank card or the like. If, in order to correct this problem, 0.1 mm is removed from both the top and bottom of the plastic so that the lower side is less than 0.15 mm thick, it is difficult to form the mold. Also, if the thickness of the chip is cut from 0.35 mm to 0.2 mm, the strength of the chip is reduced. In addition, a reduction in the thickness of the lead frame is impossible from the aspect of strength and handling. As explained in the foregoing, the problems associated with conventional plastic package type semiconductor devices may be summarized as follows. In the conventional plastic package type semiconductor device, as a result of unbonded regions such as voids being formed during the manufacturing process, a breakdown in the electrical insulation in the resulting semiconductor device is possible, and cracking can occur in the package from reflow. Furthermore, in surface mounted type packages such as an SOP or an SOJ or the like, it is impossible to provide a package thickness of less than 1.0 mm which restricts the fields in which the package can be used. EP-A-0 350 833 shows a hybrid i.c. comprising a substrate and a support plate in a resin moulding. The support plate may comprise more than one part. Summary of the Invention From Patent Abstracts of Japan, Vol.13 (371), (E-807)[3719] a lead frame comprising a die pad having more than one part is known. EP-A-0 454 150 forms part of the state of the art defined by Article 54(3) EPC. It shows a device with a divided die pad. In one division the semiconductor chip is supported, while an interconnecting member is in the other division. Moulding plastic fills a gap between the chip and this member, enabling a reduced package thickness. EP-A-0 447 922 forms part of the state of the art defined by Article 54(3) EPC. It shows a resin seal type device having chip support below the chip, and a through wire lead running over the chip. Accordingly, an object of the present invention is to provide, with due consideration to the drawbacks of such conventional devices, a plastic package type semiconductor device wherein no voids or package type semiconductor device wherein no voids or package cracks are produced. Accordingly, the destruction of an electrical insulation between the die pad and the semiconductor chip can be prevented in the plastic package type semiconductor device. A further object of the present invention is to provide a thin plastic package type semiconductor device wherein there is no loss in package strength or in electrical insulation properties. According to the present invention, there is provided a plastic package type semiconductor device as set out in claim 1. Further, in the plastic package type semiconductor device described above, each part of the die pad may be rectangular, and the supporting tab leads are provided along the long side and the short side of the plastic package. Moreover, in the plastic package type semiconductor device described above, each part of the die pad may be a U-shaped type, and the supporting tab leads are provided along the long side and the short side of the plastic package. In addition, in the plastic package type semiconductor device described above, the supporting tab leads may be provided only along the long side of the plastic package. Furthermore, in the plastic package type semiconductor device described above, the supporting tab leads may be provided only along the short side of the plastic package. These and other objects, features, and advantages of the present invention will become more apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a plan view of a conventional plastic package type semiconductor device. FIG.2 is a sectional view of the conventional plastic package type semiconductor device viewed along the section A - A' in FIG.1. FIG.3 is a sectional view of a surface mounted type package such as an SOP (Small Outline Package) or an SOJ (Small Outline J-leaded Package). FIG.4 is a view for explaining the thickness of each structural part of the plastic package type semiconductor device shown in FIG.3. FIG.5 is a plan view of one embodiment of the plastic package type semiconductor device of the present invention. FIG.6 is a sectional view of the embodiment of the plastic package type semiconductor device viewed along the section B - B' in FIG.5. FIG.7 is a sectional view of the embodiment of the plastic package type semiconductor device viewed along the section C - C' in FIG.5. FIG.8A to FIG.8D are plan views of other plastic package types semiconductor devices which do not show all the features of the present invention using die pads of various structural types. FIG.9A and FIG.9B are views for explaining the thickness of each structural part of the plastic package type semiconductor devices shown in FIG.8A to FIG.8B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Other features of this invention will become apparent in the course of the following description of exemplary embodiments which are given for illustration of the invention and are not intended to be limiting thereof. An embodiment of the present invention will now be described with reference to the drawings. FIG.5 is a plan view of a lead frame on one embodiment of the plastic package type semiconductor device of the present invention. As shown in the drawing, the plastic package type semiconductor device comprises a die pad 10, a plurality of tap leads 20, a semiconductor chip 30, a second bonding section 50, a Jumper lead (flat type) 70a, a bonding wire 90, an insulating film or a polycide tape 15, and a plurality of inner leads 40. One of the features of this embodiment is that the jumper lead 70a is a flat type and not the U-shaped type found in the conventional device. For this reason, it is possible to provide a plastic package type semiconductor device which is thinner than a conventional semiconductor device. FIG.6 is a sectional view of the embodiment viewed along the section B - B' in FIG.5, and FIG.7 is a sectional view along the section C - C'. These two drawings show an insulating adhesive or a conductive adhesive 11a, a plastic mold 60, and an adhesive 17. As shown in the drawings, the insulating film 15 of the semiconductor device of the present invention is formed on the die pad 10 which is used as a lead frame, and the semiconductor chip 30 is bonded to the insulating film 15 by means of the insulating adhesive or conductive adhesive 11a. Following this, the semiconductor device is formed by the normal bonding, molding, and T/F (Trimming and Forming) processes. Therefore, in this embodiment of the plastic package type semiconductor device, because a silver plating formed on the die pad 10, which is used as a lead frame, and the semiconductor chip 30 bonded by means of the insulating adhesive or conductive adhesive 11a are not electrically conductive because of the insulating film 15 attached to the die pad 10, it is possible to prevent corrosion of the silver plating on the die pad 10. Furthermore, by forming the insulating film 15, it is possible to provide a flat type of jumper lead 70a so that a thin semiconductor device can be provided. FIG.8A to FIG.8D show other plastic package types. As illustrated in the drawings, a die pad 100 is divided into two parts (100a, 100b) so that it is possible to adequately disperse the thermal stress within the package during reflow. In addition, a plurality of tab leads 20 is provided so that any steam generated during the above mentioned reflow is adequately discharged from the package. Accordingly, it is possible to prevent the formation of cracks in the package from the reflow. Die pads 100(100a,100b),110(110a,110b),120(120a,120b),130(130a,130b) of various configurations are shown in FIG.8A to FIG.8D. The insulating film 15, which is one of the features of the present invention, is for example, a polycide tape. Because the insulating film 15 is provided, the die pad sections 100, 110, 120, 130 are completely insulated electrically from the semiconductor chip 300, therefore voids which occur during the manufacturing process and cracks which form in the package after completion of the product can be prevented, making it possible to provide a thin plastic package type semiconductor device free from such defects. In FIG.8A, the die pad 100 is a rectangular type; in FIG.8B, the die pad 110 is a U-shaped type; in FIG.8C, the die pad 120 is a rectangular type; and in all these cases the area of the insulating film 15 is smaller than that of the semiconductor chip 300; and in FIG.8D, the die pad 130 is supported only by the two sides of the semiconductor chip 300. However, the present invention is not limited to semiconductor devices with die pads of these configurations. In the above-described embodiment of the plastic package type semiconductor device of the present invention, the large-area die pad 1 found in the conventional device is unnecessary. For example, with the configuration shown in FIG.9A and FIG.9B, the thickness "a" of the semiconductor chip is 0.35 mm, the thickness "b" of the insulating film is 0.02 mm, the thickness "c" of the insulating/conductive adhesive is 0.03 mm, the thickness "d" of the lead frame is 0.15 mm, the thickness "e" of the plastic mold is 0.2 mm, the thickness "f" of the plastic mold is 0.2 mm, and the thickness "f'" of the plastic mold is 0.05 mm. The total thickness "g" of the package is therefore 0.8 mm. Accordingly, this semiconductor device can be used in the field of bank cards and the like in which an ultrathin type package is required. By means of the present invention as described above, a semiconductor device with an ultrathin type package is provided wherein the die pad and the semiconductor chip are completely insulated electrically by the insulating film, and the breakdown of the electrical insulation of the semiconductor chip from the silver coating of the die pad can be prevented. In addition, no cracks are produced in the package as a result of reflow. Further, because it is possible to form the flat type of jumper lead under the semiconductor chip, with no depression, rather than the conventional type which has a depression, the lead frame process can also be shortened, with an accompanying reduction in cost. The present invention is, however, not restricted to this embodiment. For example, it is possible to fabricate a plastic package type semiconductor device with a structure which combines the first and second embodiments. Various modifications will become possible for those skilled in the art after the teaching of the present disclosure without departing from the scope thereof.

Claims: A plastic package type semiconductor device comprising: a die pad having first and second parts (10a, 10b); a plurality of tab leads (20) supporting said first and second parts of said die pad; a jumper lead (70a) provided between said first and second parts of said die pad, but spaced therefrom; an electrically insulating film (15) bonded to both said first and second parts of said die pad and to said jumper lead (70a) by adhesive (17), a rectangular semiconductor chip bonded to the insulating film by a further adhesive (11a); a plurality of leads (40) provided adjacent first and second opposing sides of said chip, and first and second ends of said jumper lead (70a) projecting beyond third and fourth opposing sides of said chip, said chip being electrically connected to said leads and to said first and second ends of said jumper lead by wire bonds; and a plastic mould as a plastic package for moulding the die pad, the tab lead, the jumper lead, the insulating film, and the semiconductor device in the plastic mould. The plastic package type semiconductor of claim 1 wherein the thickness of the jumper lead (70a) is approximately equal to the thickness of the die pad (10a, 10b). A plastic package type semiconductor device according to claim 1, wherein each part of the die pad is rectangular in shape, and the supporting tab leads are provided along the long sides and the short sides of each die pad. A plastic package type semiconductor device according to claim 1, wherein each part of the die pad is U-shaped, and the supporting tab leads are provided along the long sides and the short sides of each die pad. A plastic package type semiconductor device according to claim 3, wherein the area occupied by the die pad parts is larger than the area of the insulating film. A plastic package type semiconductor device according to claim 1, wherein each part of the die pad is rectangular in shape and the supporting tab leads are provided only along the long sides of each die pad. A plastic package type semiconductor device according to claim 2, wherein each part of the die pad is rectangular and the supporting tab leads are provided only along the short sides of the die pad.

Inventors: BABA ISAO, IMAMURA TSUTOMU, BABA, ISAO, IMAMURA, TSUTOMU
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1992
Main classification: H01L23
IPC codes: H01L21, H01L23