Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Making plural separate devices
Reexamination Certificate
1999-08-24
2001-02-13
Picardat, Kevin M. (Department: 2823)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Making plural separate devices
C438S124000, C438S127000
Reexamination Certificate
active
06187614
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to electronic components of resin molded package type, and, more particularly, to electronic components suitable for surface mount technology.
Electronic components of the surface mount type are well known.
FIG. 22
shows an external view of a conventional electronic component of the surface mount type which incorporates therein a semiconductor chip (an electronic element). Electronic component
70
, shown in
FIG. 22
, has elongated, first to third leads
71
-
73
.
74
is a resin having the form of a rectangular parallelepiped which encapsulates a semiconductor chip. Each lead
71
-
73
horizontally stretches out from opposite lateral surfaces of resin
74
and has an L-shaped bent. The bottom dimensions of resin
74
is 1.6 mm×0.8 mm, and each lead
71
-
73
projects from resin
74
for from 0.4 mm to 0.6 mm. To prevent poor soldering (i.e., defective soldering in which, when mounting electronic component
70
onto a printed board, a good bond is not produced at a junction between the printed board and each lead
71
-
73
), it is required by lead stand-off specifications that the bottom surface of resin
74
floats 0 mm to 0.1 mm on the printed board surface.
FIG. 23
is a plan view of a conventional lead frame for use in the fabrication of electronic component
70
. Lead frame
80
of
FIG. 23
is formed of a rectangular metal plate that has a uniform thickness and comprises lead formation part
81
and exterior frame
82
for enclosing lead formation part
81
. Bridge part
83
is provided which acts as a bridge to connect together opposite sides of exterior frame
82
, and a plurality of sets of lead parts
71
-
73
extend from the opposite sides of exterior frame
82
. These lead parts
71
-
73
are one-dimensionally placed at pitches ranging from 3.0 mm to 4.0 mm, running in the lengthwise direction of lead frame
80
.
The fabrication of electronic component
70
, that is, the assembly process thereof, comprises a die bonding process, a wire bonding process, a molding process, a deburring process, a lead finishing process, a trimming process, and a forming process. In the die bonding process, semiconductor chips are fixed on the corresponding leading ends of first lead parts
71
of lead frame
80
of
FIG. 23
using a conductive adhesive. In the wire bonding process, two electrodes on each semiconductor chip are electrically connected with the leading ends of second and third lead parts
72
and
73
by fine wires of Au (gold). In the molding process, a mold assembly for transfer mold is used for integral encapsulation of the individual semiconductor chips, the Au wires, the leading ends of lead parts
71
-
73
with resin
74
. In this molding process; a plurality of cavities, defined between an upper mold element and a lower mold element, are one-dimensionally arranged, running in the lengthwise direction of lead frame
80
and being isolated from one another. In other words, a resin is injected, from a common runner through respective gates, into each cavity.
FIG. 24
shows lead frame
80
that has undergone a molding process. In the deburring process, burrs, formed by resin escaped from fine gaps defined between the mold assembly and the lead frame
80
onto lead parts
71
-
73
, are removed. In the lead finishing process, lead parts
71
-
73
extending from each resin
74
are solderplated. Deburring is an indispensable process to smooth solderplating. In the trimming process, lead parts
71
-
73
are cut such that individual electronic components
70
are separated. In the forming process, bending is performed so that each lead part
71
-
73
has a bent, as shown in FIG.
22
.
The above-described conventional electronic component
70
has elongated leads
71
-
73
which project from lateral surfaces of resin
74
. Therefore, electronic component
70
occupies a considerably larger space in comparison with a semiconductor chip (an electronic element), therefore producing the problem that mounting density on a printed board cannot be increased much. Additionally, leads
71
-
73
which project from resin
74
are vulnerable, which may result in an unexpected change in the lead form at the time of mounting an electronic component
70
onto a printed board, thereby causing defective soldering.
The above-described fabrication method of electronic component
70
requires both a deburring process and a forming process. It is preferred that deburring is eliminated, since the deburring process produces no additional values to products. In the forming process, unexpected lead deformation and the cut of a lead may occur. Further, in the forming process, there are difficulties in always conforming to lead stand-off specifications and there has been the problem that yields tend to drop.
In the above-described lead frame
80
, a plurality of sets of lead parts
71
-
73
are one-dimensionally arranged at a great pitch, therefore producing the problem that the number of electronic components
70
that a single lead frame
80
can yield is small. Metal material for forming lead frame
80
is used inefficiently.
In the above-described conventional mold assembly, a plurality of cavities, which are one-dimensionally arranged at a great pitch corresponding to lead frame
80
, are defined between the upper mold element and the lower mold element, so that the number of electronic components
70
that a single molding process can yield is small, resulting in poor productivity.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved electronic component of a resin molded package type capable of realizing a higher mounting density on a printed board in comparison with conventional techniques and capable of suppressing lead deformation occurring at the mounting process.
Another object of the present invention is to provide a method for fabricating an electronic component of a resin molded package type capable of eliminating deburring and forming processes thereby providing a high productivity.
Still another object of the present invention is to provide an improved lead frame for use in the fabrication of electronic components of a resin molded package type so that a greater number of electronic components can be taken efficiently in comparison with conventional techniques.
Another object of the present invention is to improve the productivity of mold assembly for use in the fabrication of electronic components of a resin molded package type.
The present invention provides an electronic component of a resin molded package type. This electronic component comprises:
(a) an electronic element;
(b) a lead which is electrically connected within the electronic element; and
(c) a resin which encapsulates the electronic element and the lead;
wherein a lateral surface of the lead and a lateral surface of the resin are simultaneously formed by a single cut such that the lateral surface of the lead is located at a lower end area of the lateral surface of the resin and the lateral surfaces of the lead and the resin are exposed forming the same plane.
Accordingly, the lateral surface of the lead, formed by cutting, is exposed at the lower end area of the lateral surface of the resin. In other words, an area, taken up by an electronic component of this invention on a printed board, is equal to the bottom surface area of the resin. In accordance with the electronic component of the present invention, a higher mounting density on a printed board, as compared with conventional electronic components in which elongated leads project from resin lateral surfaces, is accomplished. Additionally, lead deformation is unlikely to occur when performing a mounting process on a printed board. If it is arranged such that the lead bottom surface slightly projects from a resin bottom surface, lead standoff specifications can be met easily.
More specifically, a lead of an electronic component of the present invention includes a thin part which is electrically connected with an electronic element and a t
Takata Hirofumi
Tanida Tadashi
Collins D. M.
Matsushita Electronics Corporation
McDermott & Will & Emery
Picardat Kevin M.
LandOfFree
Electronic component, method for making the same, and lead... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electronic component, method for making the same, and lead..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electronic component, method for making the same, and lead... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2596174