Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With structure for mounting semiconductor chip to lead frame
Reexamination Certificate
1997-03-18
2001-07-24
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
C257S666000, C257S783000
Reexamination Certificate
active
06265762
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a lead frame and a semiconductor device, and more particularly to a technique which is applicable to a lead frame having multi-leads and a semiconductor device using the lead frame.
In the production of a semiconductor device, such as an LSI, more complicated circuits are being fabricated and the number and type of functions are also increasing with improvement in the degree of integration. Because of the ability to provide increased functions, the semiconductor device has come to require more external terminals, and thus, the numbers of pad electrodes provided on a semiconductor chip and the number of leads that form the external terminals of a semiconductor device have increased in a corresponding manner. For example, the number of external terminals has reached the hundreds in a logic semiconductor device. An example of such a multi-lead semiconductor device is a quad flat package (QFP) type semiconductor device. Since a plurality of leads are provided on all four sides of a sealing body for sealing a semiconductor chip in the QFP type semiconductor device, such a device is suitable for forming multi-leads in that the total spacing around the semiconductor device can be utilized effectively when the semiconductor device is packaged on a packaging substrate.
A lead frame of the type used for the assembling of such a QFP type semiconductor device is disclosed in “VLSI Packaging Technique (the first volume)” issued on May 31, 1993, pp. 155 to 164, and in particular an example of the pattern is shown on p157 and p159.
Further, since the number of elements formed on a semiconductor chip has been increased by means of the above-mentioned refinement and since these elements are operated at a higher speed, the generation of heat from the semiconductor chip has also increased. A semiconductor device in which heat radiation performance has been improved for the purpose of coping with this problem using a heat spreader is described in, for example, “VLSI Packaging Technique (the last volume)” pp. 200 to 203. In this semiconductor device, the heat radiation performance of the semiconductor device is improved by installing a heat spreader on a semiconductor chip.
SUMMARY OF THE INVENTION
In order to cope with the problems of multi-lead formation, as described above, it is necessary in a lead frame to diminish the lead pitch, which is the spacing between leads, as well as the width dimension of the lead.
Further, similar to the above, a plurality of pad electrodes are provided in a semiconductor chip in recognition of the increased number of functions, as described above, and the pad pitch, which is the spacing between pad electrodes, is also made smaller. Generally, there are a variety of pitches of the pad electrodes of a semiconductor chip, but it is desirable for the chip size to be small in order to increase the number of chips acquired per wafer. Thus, there is a tendency for the pitch among respective pad electrodes also to be made smaller.
However, there is a problem in that a short-circuit in which adjacent wires come into contact with each other becomes more likely as the spacing becomes smaller when multi-leads and respective pad electrodes are bonded with each other using a wire of Au or the like. Since the wires bonded to the pad electrodes stretch in an oblique direction with respect to a semiconductor chip at a corner portion of the semiconductor chip in particular, the spacing between wires becomes small even when the pad pitches are the same, and so the tendency for a short circuit to occur is more likely.
Further, there is a problem in that wire running, in which a wire is transformed by the flow of molding resin due to the lowering of the mechanical strength of respective leads, or a decrease in the wire spacing sometimes occurs in the case of resin molding after wire bonding, and so a short-circuit of the wires is often produced under these circumstances.
In addition, in a QFP, the area in which the leads are arranged becomes narrower as one gets nearer a semiconductor chip installed at the center of the support. As a result, when the lead pitch cannot be refined sufficiently with respect to the pad pitch of a semiconductor chip due to the limit of working accuracy of the leads, it becomes impossible to bring the point of the lead close to the semiconductor chip. Therefore, the wire for bonding the pad electrode and the lead with each other cannot help but be lengthened. When the wire is lengthened in such a manner, the probability of generation of the above-mentioned short-circuit or wire running conditions becomes higher.
Further, since the mechanical strength of respective leads is lowered by such refinement of the leads, the leads and more liable to be transformed by a slight force, and so a short-circuit condition is also created by such a transformation.
It is an object of the present invention to provide a technique which is capable of preventing a short-circuit or wire running condition in a semiconductor device having multi-leads from occurring and of stabilizing the bonding.
It is another object of the present invention to provide a technique which is capable of improving the heat radiation characteristics of a semiconductor device having multi-leads.
The above-mentioned and the other objects and unique features of the present invention will become apparent from the following description of the present invention and the accompanying drawings.
Among those features that are disclosed in the present application, summaries of representative features will be described briefly as follows.
In a semiconductor device in which a semiconductor chip is mounted on a supporting body and inner leads are fixed to this supporting body through an insulator, points of the inner leads are fixed to the whole periphery of the semiconductor chip mounting area by an adhesive layer provided on the whole surface of the above-mentioned supporting body.
Furthermore, the largest lead pitch is set to less than double the smallest lead pitch with respect to the lead pitch at the points of respective inner leads.
Furthermore, the lead pitch at inner lead points corresponding to a corner portion of a semiconductor chip is made wider than the lead pitch at the other lead points.
Alternatively, a dummy lead which does not extend outside a sealing body is provided among inner leads corresponding to the corner portion of the semiconductor chip.
Furthermore, the pad pitch of pad electrodes located at the corner portion of a semiconductor chip is made wider than the pad pitch of the other pad electrodes.
According to the above-mentioned features, it becomes possible to have the points of the inner leads come closer to a semiconductor chip mounting area by fixing the inner lead points to the whole periphery of the semiconductor chip mounting area. Therefore, a short-circuit, in which adjacent wires come into contact with each other, and wire running, in which the wires are transformed by means of the flow of mold resin, are avoided.
Further, since it becomes possible to make the lead pitch at the inner lead points corresponding to the corner portion wider than the lead pitch at the other inner lead points, the possibility of a short-circuit, in which adjacent wires come into contact with each other, and wire running, in which the wire is transformed by the flow of mold resin, is decreased.
Furthermore, since turbulence is reduced in the flow of resin with the providing of a dummy lead, poor resin injection due to the presence of a void is decreased.
Furthermore, it becomes possible to perform cross-bonding easily because there is no tab suspending lead.
Furthermore, it becomes possible to perform a production process to make a lead frame with a supporting body easier and to reduce the production cost by forming an adhesive layer in advance on the whole surface of the supporting body, thereby to fix the inner leads.
Furthermore, by mounting a semiconductor chip on a supporting body, the heat generated in the semiconductor chip can be rad
Fujisawa Atsushi
Hirano Tsugihiko
Konno Takafumi
Nagano Souichi
Okamoto Toshiaki
Antonelli Terry Stout & Kraus LLP
Chaudhuri Olik
Ha Nathan W.
Hitachi Ltd
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