Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame
Reexamination Certificate
2001-03-20
2002-11-26
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
C257S528000, C257S532000, C257S786000, C257S531000
Reexamination Certificate
active
06486535
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to electronic packages, and more particularly to lead frame packages characterized by directly mounting surface-mountable devices on lead frame.
2. Description of the Related Art
An electronic package typically includes a lead frame with one or more active devices attached thereon; packages including only one device are known as Single Chip Modules (SCM), while packages including a plurality of devices are called Multi Chip Modules (MCM). The active device is typically a chip commonly made of Silicon, Germanium or Gallium Arsenide.
FIG. 1
depicts a conventional electronic package comprising a lead frame for supporting a semiconductor chip
100
. The lead frame includes a plurality of leads having outer lead portions
106
and inner lead portions
107
. The chip
100
is attached onto a die pad
111
using a die attach adhesive such as silver paste
114
. The die pad
111
is connected to the lead frame by supporting bars (not shown in FIG.
1
). The outer lead portions
106
are used for electrical coupling to an outside circuit. The chip
100
has bond pads electrically interconnected to the inner lead portions
107
of the lead frame through bonding wires
115
. The chip
100
, the die pad
111
, the inner lead portions
107
of the lead frame and bonding wires
115
are encapsulated in a package body
117
made of insulating material such as epoxy.
As the speed of semiconductor devices increase, noise in the DC power and ground lines increasingly becomes a problem. To reduce this noise, passive components such as decoupling capacitors are often used to reduce power supply noise which occurs due to change in potential difference between the ground voltage and the power-supply voltage supplied to the active device. The decoupling capacitors are typically surface-mountable devices (SMD's) used in the so-called surface-mounting technique. The decoupling capacitors are placed as close to the active device as practical to increase their effectiveness. For high pin count packages commonly encountered in the electronics manufacturing industry, as the number of I/O connections increases, finer pitches of the outer leads are required (i.e., below 0.5 mm) for the lead frame used therein. Therefore, lead frames for high pin count packages usually have a fine structure such that the decoupling capacitors cannot be directly mounted on the leads of the lead frames. Some wafers have capacitors built into the architecture of each chip, thereby significantly enhancing the electrical performance thereof. However, that will complicate the manufacturing process of wafer thereby increasing the production cost.
Accordingly, the present invention seeks to provide a method for directly mounting surface-mountable devices on a lead frame, which overcomes, or at least reduces the above-mentioned problems of the prior art.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide an electronic package with surface-mountable devices built therein. The electronic package comprises a lead frame for supporting a semiconductor chip and is characterized in that the surface-mountable devices are directly mounted on the lead frame thereby increasing the electric performance of the electronic package.
The electronic package in accordance with the present invention mainly comprises a lead frame including a die pad and a plurality of conductive leads; a semiconductor chip disposed on the die pad and electrically connected to the leads; a surface-mountable device disposed on the lead frame; and a package body encapsulating a portion of the lead frame, the semiconductor chip and the surface-mountable device. Preferably, the surface-mountable device is a passive component such as a resistor, a capacitor or an inductor.
In a preferred embodiment of the present invention, at least two leads of the lead frame have portions joined together to form a first pad and the die pad has a protruding portion to form a second pad such that the surface-mountable device is connected across the first pad and the second pad.
In another preferred embodiment of the present invention, at least two adjacent leads of the lead frame have portions joined together to form a first pad and at least another two adjacent leads of the lead frame have portions joined together to form a second pad. In addition, the electronic package further comprises a tape that is attached across the leads of the lead frame and has two openings formed corresponding to the first pad and the second pad. In this embodiment, the surface-mountable device is supported by the tape and connected across the first pad and the second pad through the openings of the tape.
In a further preferred embodiment of the present invention, the electronic package further comprises a tape attached across the leads of the lead frame and at least one layer of electrical circuitry formed on the tape. The electrical circuitry comprises two first pads and two second pads respectively coupled to the first pads. Each of the first pads has an aperture formed corresponding to one predetermined lead. The tape has openings formed corresponding to the apertures of the first pads. In this embodiment, the surface-mountable device is supported by the tape and connected across the two second pads. The apertures and corresponding openings are filled with a conductive paste so as to electrically connect the surface-mountable device to the predetermined leads.
According to a still further preferred embodiment of the present invention, the electronic package further comprises a tape attached across the leads of the lead frame and at least one layer of electrical circuitry formed on the tape. The electrical circuitry comprises two first pads and two second pads respectively coupled to the first pads. In this embodiment, the two first pads are adapted to support the surface-mountable device and the two second pads are adapted for wire bonding to the semiconductor chip.
REFERENCES:
patent: 5484959 (1996-01-01), Burns
patent: 5530622 (1996-06-01), Takiar et al.
patent: 5608359 (1997-03-01), Knecht et al.
patent: 5677566 (1997-10-01), King et al.
patent: 6054764 (2000-04-01), Howser et al.
patent: 6100112 (2000-08-01), Amano et al.
patent: 6310752 (2001-10-01), Shrier et al.
patent: 6313520 (2001-11-01), Yoshida et al.
Advanced Semiconductor Engineering Inc.
Anduja Leonardo
Flynn Nathan J.
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