Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Metallic housing or support
Reexamination Certificate
2001-10-09
2004-04-13
Talbott, David L. (Department: 2827)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Metallic housing or support
C438S106000, C257S666000, C257S676000
Reexamination Certificate
active
06720207
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a leadframe as a land grid array (LGA) in which multiple lands are arranged in columns and rows of external terminals exposed on the bottom of a package. This invention also relates to a resin-molded semiconductor device including the leadframe, a method of making the leadframe and a method for manufacturing the device.
In recent years, to catch up with rapidly advancing downsizing and performance enhancement of electronic units, it has become increasingly necessary to assemble semiconductor components at a higher and higher density. To meet this demand, a resin-molded semiconductor device, formed by molding a semiconductor chip and leads together with a resin encapsulant, has its size and thickness reduced noticeably. In parallel with this downsizing trend, the number of pins required for a single electronic unit is also increasing day after day.
Hereinafter, a known leadframe for use in a resin-molded semiconductor device will be described with reference to the drawings.
FIG. 12
illustrates a plan view of a known leadframe. The leadframe
100
shown in
FIG. 12
is for use in a quad flat package (QFP) in which external pins extend outward from the four side faces of a rectangular parallelepiped package. As shown in
FIG. 12
, the leadframe
100
includes frame rail
101
, rectangular die pad
102
, inner leads
103
and outer leads
104
. The die pad
102
is located at the center of the frame rail
101
. The inner end of each inner lead
103
faces an associated side of the die pad
102
and the respective inner ends of the inner leads
103
are spaced apart from the sides of the die pad
102
. The inner end of each outer lead
104
is connected to the outer end of the associated inner lead
103
while the outer end of each outer lead
104
is connected to the frame rail
101
. The outer leads
104
are joined together by a tie bar
105
for preventing the overflow of a resin encapsulant during a resin molding process. And the die pad
102
is supported at the four corners by support pins
106
that are connected to the tie bar
105
.
In
FIG. 12
, the members existing inside the dashed-line region
109
will be molded together by a resin encapsulant. Although just a part of the leadframe
100
for one device is illustrated in
FIG. 12
, the leadframe
100
actually has many other parts that each have the pattern shown in FIG.
12
and that are arranged in columns and rows.
FIG. 13
illustrates a cross-sectional structure for a resin-molded semiconductor device including the leadframe
100
. In
FIG. 13
, each component also shown in
FIG. 12
is identified by the same reference numeral.
As shown in
FIG. 13
, a semiconductor chip
107
is bonded onto the die pad
102
using some adhesive or solder. The semiconductor chip
107
is electrically connected to the inner leads
103
using metal fine wires
108
. The die pad
102
, semiconductor chip
107
on the die pad
102
, metal fine wires
108
and inner leads
103
are molded together with a resin encapsulant
109
A. In this case, the bottom of the die pad
102
is completely buried in the resin encapsulant
109
A. The outer leads
104
extend outward from the side faces of the resin encapsulant
109
A parallelly to the surface of the die pad
102
on which the chip
107
has been mounted. Also, the outer leads
104
have been bent downward so that this package can be surface-mounted onto a motherboard.
As described above, the number of components that should be integrated together within a single semiconductor chip
107
, or the number of external electrodes (or pins) per chip, has been on the rise these days. Thus, the number of outer leads
104
should also be increased to catch up with this latest trend. That is to say, the number of inner leads
103
, which are joined to the outer leads
104
, should also be increased to cope with such an implementation. However, the width of the inner (or outer) leads
103
or
104
has a patternable limit. Accordingly, if the number of inner (or outer) leads
103
or
104
was further increased, the overall size of the leadframe
100
should also increase. This is not allowable because the increase in size of the leadframe
100
is incompatible with the recent downsizing trend. On the other hand, if the width of the inner or outer leads
103
or
104
were reduced, then it would be much more difficult to form the leadframe
100
in its desired shape.
To cope with these problems, face-bonded semiconductor devices, such as ball grid array (BGA) and land grid array (LGA) types, are also available recently. In semiconductor devices of these types, a semiconductor chip is mounted onto the non-circuitry side of a carrier (e.g., a printed wiring board), including ball or land electrodes on its back surface, and is electrically connected to these electrodes.
A semiconductor device of the BGA or LGA type is then mounted onto a motherboard so that its back surface faces the principal surface of the motherboard. And then the external electrodes (i.e., the ball or land electrodes), exposed on the back surface of the device, are directly connected electrically to the electrodes on the motherboard.
The BGA- or LGA-type semiconductor device, however, uses a multilayer carrier (or wiring board) in which ceramic or plastic layers have been stacked. Accordingly, the fabrication process thereof is overly complicated and the fabrication cost thereof is far from reasonable.
Also, it is hard to apply a method for manufacturing the known resin-molded semiconductor device shown in
FIGS. 12 and 13
as it is to forming a semiconductor device of the BGA or LGA type. The reason is as follows. In the manufacturing process, part of a metal plate, including portions to be lands as external electrodes, should be connected to the frame rail with some joining/supporting members before the lands are formed. Accordingly, where lands should be arranged in three or more rows, the device of the BGA- or LGA-type device cannot be so small.
In addition, according to the method for manufacturing the known resin-molded semiconductor device shown in
FIGS. 12 and 13
, the device cannot be mounted onto the motherboard so accurately as in manufacturing a face-bonded semiconductor device of the BGA or LGA type. As described above, the beam-like outer leads
104
shown in
FIG. 12
extend linearly outward from the sides of the resin encapsulant
109
A just after the members of the device have been molded. Accordingly, the outer leads
104
should be bent downward so that the far end of each outer lead
104
has its bottom located at least no higher than the back surface of the resin encapsulant
109
A. And in this bending process step, the outer leads
104
cannot be bent so uniformly and the far ends of the outer leads
104
are likely located at various levels.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to make a smaller leadframe, including lands arranged in multiple (three or more, in particular) rows, out of a single-layer metal plate easily enough to manufacture a downsized resin-molded semiconductor device using the leadframe.
To achieve this object, according to the present invention, a plurality of lands are arranged in columns and rows between a frame rail and a die pad, and the lands and frame rail get retained by a lead retaining member on the upper and/or lower surface(s) thereof.
Specifically, a first inventive leadframe includes: a frame rail; a die pad, disposed inside the frame rail, for mounting a semiconductor chip thereon; and a plurality of internal inner leads, which are disposed to surround the die pad and each of which has a convex portion on the bottom thereof. The frame rail and the internal inner leads are retained by a lead retaining member on their upper and/or lower surface(s).
In the first leadframe, the internal inner leads, each having a convex portion to be an external terminal (i.e., land) on its bottom, and the frame rail are retained by a lead retaining member on their upper and/or lower surface(s).
Fukuda Toshiyuki
Kawai Fumihiko
Koichi Masanori
Minamio Masanori
Oga Akira
Matsushita Electric - Industrial Co., Ltd.
Nixon & Peabody LLP
Studebaker Donald R.
Talbott David L.
Thai Luan
LandOfFree
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