Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With dam or vent for encapsulant
Reexamination Certificate
2001-06-13
2003-08-05
Talbott, David L. (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With dam or vent for encapsulant
C257S666000, C257S670000, C438S123000, C438S124000
Reexamination Certificate
active
06603194
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a lead frame such that the lead frame is exposed on the bottom surface after it is encapsulated in a resin, and a method for fabricating a resin-encapsulated semiconductor device that can be surface-mounted on a substrate, using such a lead frame.
In recent years, there is an increasing demand for high-density mounting of semiconductor elements in order to realize smaller electronic devices with higher functionalities. Accordingly, the overall size and the thickness of a resin-encapsulated semiconductor device (a device obtained by integrally encapsulating a semiconductor chip and leads in a resin mold) have been quickly reduced. Moreover, various techniques have been developed in order to reduce the production cost and to increase the productivity.
A conventional method for fabricating a resin-encapsulated semiconductor device will now be described with reference to FIG.
11
.
FIG. 11
illustrates a conventional method for fabricating a resin-encapsulated semiconductor device. More specifically,
FIG. 11
is a cross-sectional view illustrating a step of separating a plurality of semiconductor devices resin-encapsulated onto a lead frame from one another. As illustrated in
FIG. 11
, a lead frame
101
, on which a plurality of semiconductor devices
100
are individually encapsulated in a resin, is held on a dicing sheet
200
, and then the lead frame
101
is cut by a cutting blade
201
along a cut region extending between adjacent semiconductor devices
100
. A burr
101
a
(a rough edge remaining after cutting the lead frame
101
) may be produced on the end surface (the cut surface) of the lead frame
101
after being cut by the cutting blade
201
.
The burr
101
a
occurring on the bottom surface of the semiconductor device
100
is undesirable. If the semiconductor device
100
is a surface-mounted device in which the leads are exposed on the bottom surface thereof, the adherence between the semiconductor device
100
and the substrate on which it is mounted may be insufficient due to the burr
101
a
, thereby making the electrical connection therebetween imperfect.
While diamond powder, or the like, is typically applied on the cutting surface of the cutting blade
201
, the cutting surface is likely to be loaded with metal powder as the cutting blade
201
is repeatedly used to cut the lead frame
101
, which is made of a metal. Once the cutting blade
201
is loaded, the cutting process cannot be continued with the loaded cutting blade
201
, and it is necessary to replace the loaded cutting blade
201
with a new blade. Such a replacement process reduces the productivity.
SUMMARY OF THE INVENTION
The present invention has been made to solve the these problems in the prior art, and has an object to reduce the burr occurring on the cut surface of a lead frame, thereby improving the quality of a resin-encapsulated semiconductor device while prolonging the life of a cutting blade, thus improving the productivity.
In order to achieve this object, the present invention provides a lead frame made of a metal and having cut regions along which the lead frame is cut into a plurality of semiconductor devices, wherein the cut regions are partially depressed to reduce the amount of metal existing along the cut regions. When fabricating a resin-encapsulated semiconductor device, the depressed portion of each cut region of the lead frame may be filled with an encapsulation resin.
Specifically, a first lead frame according to the present invention includes: an outer frame section; a plurality of chip mounting sections which are supported by the outer frame section and on which a plurality of semiconductor chips are mounted; lead sections surrounding the chip mounting sections; connecting sections for connecting and supporting the lead sections and the outer frame section with each other; and an encapsulation region in which the chip mounting sections are encapsulated together in an encapsulation resin, wherein an opening is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region and along an extension of one of the connecting sections.
In the first lead frame, an opening is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region and along an extension of one of the connecting sections. Therefore, when the lead frame is cut by a cutting blade along the connecting sections, the amount of the lead frame to be cut by the cutting blade is reduced in a portion of the outer frame section that is outside the encapsulation region. In this way, it is possible to reduce the occurrence of a burr of the lead frame and to suppress the loading of the cutting blade, thereby improving the quality of the resin-encapsulated semiconductor device while prolonging the life of the cutting blade, thus improving the productivity.
In the first lead frame, it is preferred that a width of the opening is greater than a thickness of cutting means for cutting the lead frame along the connecting sections. In this way, the cutting means does not contact the lead frame in the openings, thereby reliably suppressing the occurrence of a burr of the lead frame and the loading of the cutting means.
A second lead frame according to the present invention includes: an outer frame section; a plurality of chip mounting sections which are supported by the outer frame section and on which a plurality of semiconductor chips are mounted; lead sections surrounding the chip mounting sections; connecting sections for connecting and supporting the lead sections and the outer frame section with each other; and an encapsulation region in which the chip mounting sections are encapsulated together in an encapsulation resin, wherein a depressed portion is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region, on a reverse side of a runner section along which the encapsulation resin flows, and along an extension of one of the connecting sections.
In the second lead frame, a depressed portion is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region, on a reverse side of a runner section along which the encapsulation resin flows, and along an extension of one of the connecting sections. Therefore, when the lead frame is cut by a cutting blade along the connecting sections, the amount of the lead frame to be cut by the cutting blade is reduced in a portion of the outer frame section that is outside the encapsulation region. In this way, it is possible to reduce the occurrence of a burr of the lead frame and to suppress the loading of the cutting blade. In addition, the depressed portion may be filled with an encapsulation resin. Since an encapsulation resin is typically mixed with silica (silicon oxide) as a filler, there is provided a so-called “dressing effect” of recovering the cutting blade, etc., from a loaded state by the silica component mixed in the encapsulation resin. As a result, the occurrence of a burr is reduced, thereby improving the quality of the resin-encapsulated semiconductor device, while the life of the cutting blade can be prolonged by the dress effect provided by the silica component.
In the second lead frame, it is preferred that a width of the depressed portion is greater than a thickness of cutting means for cutting the lead frame along the connecting sections. In this way, the cutting means does not contact the lead frame in the depressed portions, and the cutting means instead contacts the encapsulation resin, thereby suppressing the occurrence of a burr of the lead frame while further improving the dressing effect on the cutting means.
In the first or second lead frame, it is preferred that each of the connecting sections includes a thinned portion whose thickness is smaller than a thickness of the outer frame section. In this way, the thickness of the encapsulation resin is increased above or below the conne
Funakoshi Masashi
Hamatani Tsuyoshi
Morikawa Takeshi
Nakabayashi Yukio
Utsumi Masaki
Nixon & Peabody LLP
Studebaker Donald R.
Talbott David L.
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