Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With structure for mounting semiconductor chip to lead frame
Reexamination Certificate
1999-01-21
2002-10-08
Jackson, Jerome (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With structure for mounting semiconductor chip to lead frame
C252S700000, C252S700000
Reexamination Certificate
active
06462406
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Filed of the Invention
The present invention relates to a method of producing a semiconductor device and a configuration thereof. More particularly, it relates to a method of producing a resin-sealed semiconductor device and a configuration thereof which make it possible to decrease the size, thickness, weight and cost of the device.
2. Description of the Related Art
FIGS. 10A and 10B
show a gull-wing type semiconductor device with the configuration of the prior art,
FIG. 10A
being a cross sectional view thereof and
FIG. 10B
being a top view (perspective view) thereof.
A semiconductor device of this configuration is generally produced in such steps as shown in
FIG. 11
, in a procedure described below. A semiconductor element
3
is bonded by means of a die bonding material
2
on an island
14
of a lead frame
6
which has the islands
14
and leads
1
as shown in FIG.
12
. Then after connecting an inner lead section la of the lead
1
surrounding the island
14
to an electrode pad located on the semiconductor element
3
by wire bonding of a wire
4
such as gold wire, the elements are sealed individually on both sides of the lead frame
6
by using a sealing resin
5
.
FIG. 13
is a top view of the semiconductor device with the configuration of the prior art after being sealed with the resin (the sealing resin is indicated with dotted line). In a last stage, an outer lead section
1
b
of the lead
1
is plated with tin or the like, cut off from the lead frame
6
and formed in gull wing shape, thereby to obtain the semiconductor device as in FIG.
12
.
In the method of the prior art, it is necessary to prepare the lead frame
6
having the islands
14
matched to the size of the semiconductor elements
3
and molding dies (not shown) for sealing the individual semiconductor elements with resin. Therefore, when semiconductor elements
3
of different specifications are used, it is necessary to prepare different lead frames
6
and different molding dies for the various specifications.
In the semiconductor device of the prior art shown in
FIG. 12
, there has been a limitation on the reduction of the size and weight of the semiconductor device because the resin covers both sides of the lead frame
6
.
Moreover, because heat generated by the semiconductor element
3
is dissipated through the lead
6
, it is difficult to apply the device to power transistors which generate much heat and, because of the relatively long connection between the semiconductor element
3
and a mother board, it is also difficult to apply the device to high-frequency transistors or the like.
To counter such problems as described above, a molded transistor of chip on lead (COL) configuration wherein a semiconductor chip is directly connected on a lead is disclosed, for example, in Japanese Patent Kokai Publication No. 9-27584. However, since production of such a molded transistor requires different lead frames for different specifications and molding with the resin is carried out individually for each semiconductor element, different molding dies must be prepared for different specifications and therefore the above problems are not solved.
Also because the devices are mounted on the mother board by using outer leads, the technology is difficult to be applied to devices which generate much heat and high-frequency elements.
SUMMARY OF THE INVENTION
An object of the present invention to provide a method of producing the semiconductor device wherein semiconductor elements are sealed with resin by using the same lead and other means regardless of the specifications of the semiconductor elements, and a semiconductor device which can be reduced in size and weight and has good heat dissipation performance and high-frequency performance.
The present inventors have intensively studied. As a result, they found that semiconductor devices can be produced with a same lead frame regardless of the specifications of semiconductor elements when a plurality of the semiconductor elements are mounted on the lead frame having the leads disposed substantially parallel to each other and, after sealing the whole with a resin, the individual semiconductor devices are cut off, and that the semiconductor device produced with this method has improved heat dissipation performance and high-frequency performance. Thus, the present invention has been accomplished.
The invention provides a method of producing a semiconductor device comprising a die bond pad, a wire bond pad, a semiconductor element mounted on the die bond pad, and a sealing resin for molding the semiconductor elements, which comprises preparing a lead frame having a plurality of leads disposed substantially in parallel to each other at intervals in the longitudinal direction in the same plane; bonding a plurality of semiconductor elements in parallel on at least one lead surface of the lead frame; electrically connecting an electrode of each semiconductor element, the lead having the semiconductor element bonded thereon and another lead adjacent therewith in the longitudinal direction; molding the plurality of semiconductor elements together by means of the sealing resin applied from above the lead surface so that the back side of the lead is exposed; and cutting the leads in the longitudinal direction to divide the lead with the semiconductor element being bonded thereon into a portion where the semiconductor element is bonded thereon and a portion which is connected to the electrode, and to divide the other lead into portions connected to different electrodes, thereby to take the lead with the semiconductor element being bonded thereon as a die bond pad, and to take the lead connected to the electrode as a wire bond pad.
With this method of producing the semiconductor element, it becomes possible to produce the semiconductor device having semiconductor elements of different sizes mounted thereon by using the lead frame of the same configuration, and therefore the production process can be simplified and the production cost can be reduced.
Also with this method, because the lead frame whereon the semiconductor elements are bonded is sealed with the resin as a whole at the same time, it is not necessary to prepare different molding dies for resin sealing of semiconductor devices of different sizes as in the case of the prior art where the semiconductor devices are sealed with a resin individually, thus making it possible to reduce the production cost.
In mass production, because the semiconductor devices are made by cutting off the lead frame whereon the semiconductor elements are mounted consecutively as shown in
FIG. 3A
, there is no part of the lead frame to be wasted, so that product yield per unit area of the lead frame is improved and the production cost can be reduced.
Moreover, even when the size of the semiconductor element is changed, the semiconductor devices can be produced by using the same lead frame. Thus, it is not necessary to prepare lead frames having islands of different sizes for the semiconductor elements of different sizes as in the case of the prior art, thereby making it possible to reduce the production cost by using the common lead frame.
The present invention provides a method of producing a semiconductor device comprising a die bond pad, a wire bond pad, a semiconductor element mounted on the die bond pad, and a sealing resin for molding the semiconductor element, which comprises preparing a lead frame having comb-shaped leads which are symmetrically disposed substantially in parallel and opposite to each other at intervals in the longitudinal direction in the same plane; bonding semiconductor elements on every other leads among the leads arranged in the longitudinal direction on at least one side of the symmetrical arrangement; electrically connecting an electrode of the semiconductor element and another lead adjacent to the former lead; molding the semiconductor elements together by means of the sealing resin applied from above the lead surface so that the back side of the lead is exposed; and
Fujihara Teruhisa
Ohgiyama Kenji
Yamasaki Atsushi
Cruz Lourdes
Jackson Jerome
Mitsubishi Denki & Kabushiki Kaisha
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