Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Making plural separate devices
Reexamination Certificate
2001-11-06
2003-10-28
Pham, Long (Department: 2823)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Making plural separate devices
C438S123000, C438S127000, C438S108000, C438S118000
Reexamination Certificate
active
06638790
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a leadframe, which includes leads with land electrodes functioning as external terminals and can replace a conventional leadframe with beam-like leads. The present invention also relates to a method for manufacturing a land-grid-array (LGA) resin-molded semiconductor device, in which a semiconductor chip is bonded onto the leadframe and the assembly is molded with a resin encapsulant.
In recent years, to catch up with rapidly advancing downsizing of electronic units, it has become increasingly necessary to assemble semiconductor components, like resin-molded semiconductor devices, at a higher and higher density. In response, sizes and thicknesses of semiconductor components have also been noticeably reduced. In parallel with this downsizing trend, the number of pins needed for a single electronic unit is also increasing day after day. To meet these demands, resin-molded semiconductor devices of a greatly shrunken size and with a drastically reduced thickness should now be assembled at an even higher density.
Hereinafter, a conventional leadframe for a resin-molded semiconductor device will be described.
FIG. 22
is a plan view illustrating the structure of a conventional leadframe. As illustrated in
FIG. 22
, the leadframe includes rectangular die pad
102
, support leads
103
, beam-like inner leads
104
, outer leads
105
and tie bars
106
, all of these members being provided inside a frame rail
101
. The die pad
102
is used for mounting a semiconductor chip thereon. The support leads
103
support the die pad
102
. The inner leads
104
will be electrically connected to the semiconductor chip with some connection members like metal fine wires. The outer leads
105
are joined to the respective inner leads
104
and to be connected to external terminals. And the tie bars
106
are provided for joining and fixing the outer leads
105
together and for preventing a resin encapsulant from overflowing during a resin molding process.
It should be noted that normally the leadframe does not consist of the single pattern shown in
FIG. 22
, but is made up of a plurality of such patterns, which are arranged and connected together both horizontally and vertically.
Next, a known resin-molded semiconductor device will be described.
FIG. 23
is a cross-sectional view illustrating a resin-molded semiconductor device including the leadframe shown in FIG.
22
.
As shown in
FIG. 23
, a semiconductor chip
107
has been bonded onto the die pad
102
of the leadframe and electrically connected to the inner leads
104
with metal fine wires
108
. The semiconductor chip
107
on the die pad
102
, the inner leads
104
and so on have been molded with a resin encapsulant
109
. The outer leads
105
protrude from the side faces of the resin encapsulant
109
and have had their outer ends bent downward.
Next, a method for manufacturing the resin-molded semiconductor device will be described with reference to
FIGS. 23 and 24
. First, the semiconductor chip
107
is bonded, with an adhesive, onto the die pad
102
of the leadframe. This process step is called “die bonding”. Next, the semiconductor chip
107
is connected to the respective inner ends of the inner leads
104
with the metal fine wires
108
. This process step is called “wire bonding”. Subsequently, the semiconductor chip
107
and a portion of the leadframe inside the tie bars
106
(i.e., the inner leads
104
and so on) are molded with the resin encapsulant
109
such that the outer leads
105
protrude outward. This process step is called “resin molding”. Finally, the tie bars
106
are cut off at the boundary between the tie bars
106
and the resin encapsulant
109
to separate the outer leads
105
from each other and remove the frame rail
101
, and the respective outer ends of the outer leads
105
are bent. This process step is called “tie bar cutting and bending”. In this manner, a resin-molded semiconductor device with the structure shown in
FIG. 23
is completed. In
FIG. 24
, the dashed line indicates a region where the assembly is molded with the resin encapsulant
109
.
As described above, the number of devices that should be integrated within a single semiconductor chip, or the number of pins per chip, has been on the rise these days. Thus, the number of outer leads should also be increased to catch up with this latest trend. That is to say, the number of inner leads, which are joined to the outer leads, should preferably be increased to cope with such an implementation. However, the width of the inner (or outer) lead has a processable limit. Thus, as the number of inner (or outer) leads is increased, the overall size of the leadframe and that of the resulting resin-molded semiconductor device also increase. In view of these states in the art, it is difficult to realize a downsized and thinned resin-molded semiconductor device. On the other hand, if only the number of inner leads is increased to cope with the rise in the number of pins needed for a semiconductor chip while using a leadframe of substantially the same size, then the width of a single inner lead should be further reduced. In such a case, however, it is much more difficult to perform various process steps for forming the leadframe, like etching, as originally designed.
Recently, face-bonded semiconductor devices, such as ball grid array (BGA) types and land grid array (LGA) types, are also available. In the semiconductor device of any of these types, first, a semiconductor chip is mounted onto a carrier (e.g., a printed wiring board) including external electrodes (e.g., ball electrodes or land electrodes) on its bottom. Next, the semiconductor chip is electrically connected to the external electrodes. And then the chip and its associated members are molded with a resin encapsulant on the upper surface of the carrier. The semiconductor device of this face-bonded type, which is mounted directly on a motherboard on the bottom, will be a mainstream product in the near future. Accordingly, it is now clear that the conventional leadframe and resin-molded semiconductor device using the leadframe will soon be out of date under the circumstances such as these.
Also, the conventional resin-molded semiconductor device includes outer leads protruding outward from the side faces of a resin encapsulant, and is supposed to be mounted onto a motherboard by bonding the outer leads to the electrodes on the motherboard. Accordingly, the conventional device cannot be mounted onto the board so reliably as the semiconductor devices of the BGA and LGA types. Nevertheless, the semiconductor devices of the BGA and LGA types are expensive, because these devices use a printed wiring board.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a leadframe effectively applicable to a resin-molded semiconductor device, in which external terminals are arranged and exposed in lines on the bottom of the package with almost no resin bur left on.
It is another object of the present invention to provide a method for manufacturing the resin-molded semiconductor device using the leadframe.
An inventive leadframe includes a frame rail, a die pad, support leads and first and second groups of leads. The frame rail is made of a metal plate. The die pad is used for mounting a semiconductor chip thereon, and disposed approximately in a center region of an opening of the frame rail. One end of each of the support leads supports the die pad, while the other end thereof is connected to the frame rail. One end of each of the leads of the first group extends toward the die pad at least partially, while the other end thereof is connected to the frame rail. The bottom of each lead of the first group is used as a land electrode of a first group. One end of each of the leads of the second group extends toward the die pad and is closer to the die pad than the end of the lead of the first group is, while the other end thereof is connected to the frame rail. Part of the bottom of each lead of the second gr
Adachi Osamu
Minamio Masanori
Matsushita Electric - Industrial Co., Ltd.
Nixon & Peabody LLP
Pham Long
Studebaker Donald R.
Trinh Hoa B.
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