Semiconductor package with wire protection and method therefor

Details Semiconductor package with wire protection and method therefor Semiconductor package with wire protection and method therefor

1999-04-16

2001-04-03

Saadat, Mahshid (Department: 2815)

Active solid-state devices (e.g., transistors, solid-state diode

Combined with electrical contact or lead

Wire contact, lead, or bond

C257S787000, C257S667000

Reexamination Certificate

active

06211574

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor package that can prevent wire bonds from shifting during packaging, and more particularly to a semiconductor package that has a fixing portion in the wire bond area to position the wire bonds during packaging a semiconductor die or electric device on the substrate. The present invention also relates to a method of manufacturing a semiconductor package with wire protection to prevent the wire bonds from shifting.
2. Description of the Related Art
When molding encapsulating material for packaging a semiconductor die or an electric device on a substrate, it is found that the encapsulating material in liquid state will sweep the wire bonds and thus causes the wire bonds to contact each other. A closed circuit is formed between the wire bonds such that the semiconductor die or electric device will malfunction or be damaged since short circuit occurs as a result of the undesired closed circuit between the wire bonds. It is, therefore, always desirable to keep the wire bonds away from one another to avoid short circuit of the semiconductor die or electric device.
Taiwan Utility Model Publication No. 347573 issued on Dec. 11, 1998 discloses a method of protecting the wire bonds, and such method is illustrated in
FIGS. 1 through 3
of the drawings.
FIG. 1
illustrates that a semiconductor die
11
is mounted on a substrate
10
, and a plurality of wire bonds
12
extend outwardly from the semiconductor die
11
to provide electrical connection between the substrate
10
and the semiconductor die
11
.
FIG. 2
illustrates spraying of the adhesive over the wire bonds
12
so as to reduce the exposed length of the wire bond
12
. As shown in
FIG. 3
, when the adhesive
13
diffuses, the adhesive
13
flows outwardly to cover the wire bond
12
. However, it takes a relatively long time to spray, diffuse and harden the adhesive
13
.
U.S. Pat. No. 5,331,205 to Primeaux issued on Jul. 19, 1994 discloses a mold plastic package with wire protection to solve the wire sweep problem. As shown in
FIG. 4
, the mold plastic package includes an encapsulating material
20
, a package body
21
, a semiconductor die
23
, a plurality of wire bonds
24
, and a lead frame
26
with a plurality of leads
25
. The semiconductor die
23
is mounted on a die pad
22
of the lead frame
26
and includes a plurality of bonding pads (not shown). The wire bonds
24
each provides an electrical connection between the bonding pads of the semiconductor die
23
and the leads
25
of the lead frame
26
. The encapsulating material
20
that has a low coefficient of thermal expansion encapsulates the upper face of the semiconductor die
23
and all of the wire bonds
24
. The package body
21
encapsulates the die
23
, portions of the leads
25
, and the encapsulating material
20
. It is, however, found that hardening of the encapsulating material
20
still takes a long time since it must cover the die
23
and the wire bonds
24
.
It is, therefore, a long and unfulfilled need to provide a semiconductor package with wire protection and with short hardening time for the encapsulating material.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a semiconductor package with wire protection to prevent the wire bonds from shifting and a method for manufacturing the semiconductor package with wire protection. A portion of a wire bond area of the substrate is provided with a fixing portion to shorten the hardening time for the fixing material forming the fixing portion, thereby saving the hardening time for the fixing portion.
It is a secondary object of the present invention to provide a semiconductor package with wire protection to prevent the wire bonds from shifting and a method for manufacturing the semiconductor package with wire protection. The fixing portion does not cover the semiconductor die so as to avoid the thermal strain on the semiconductor die due to the different coefficients of thermal expansion between the fixing portion and the semiconductor package. When the wire bond sweeping problem is eliminated, the encapsulating conditions and parameters will not be limited.
According to the the method of the present invention, a fixing material is provided in a wire bonds area on an upper surface of the substrate adjacent to the semiconductor die. The hardened fixing material forms a fixing portion for insulating and separating wire bonds. Then, an encapsulating material is molded surrounding the semiconductor die and the wire bonds to form an encapsulant.
In a preferred embodiment of the present invention, a semiconductor die or electric device is mounted on an upper surface of a substrate. A plurality wire bonds electrically connect between a plurality of bonding pads on the upper surface of the substrate and a plurality of bonding pads on an upper surface of the semiconductor die. The fixing portion is disposed surrounding the semiconductor die and covers a main portion (the mediate section) of each wire bond, since the mediate sections of the wire bonds are tended to contact one another as a result of wire sweeping.
In another preferred embodiment of the present invention, a semiconductor die or electric device is mounted on an upper surface of a substrate. A plurality of wire bonds electrically connect between a plurality of bonding pads on the upper surface of the substrate and a plurality of bonding pads on an upper surface of the semiconductor die. A first fixing portion is provided on the upper face of the substrate adjacent to a mold gate where the wire sweeping is most likely to occur while molding. A second fixing portion is provided on the upper surface of the substrate in an area opposite to the mold gate where the wire sweeping is also likely to occur.
Since the present invention disposes the fixing portion at the area surrounding the semiconductor die or the area near the mold gate for fixing and insulating mediate sections of the wire bonds, the time for hardening the fixing material at the fixing portion is relatively shortened. In addition, since the fixing portion does not cover the semiconductor die, the thermal strain acting on the semiconductor die due to different coefficients of thermal expansion between the fixing portion and the semiconductor package is eliminated.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanied drawings.


REFERENCES:
patent: 5331205 (1994-07-01), Primeaux
patent: 5434750 (1995-07-01), Rostoker et al.
patent: 5847445 (1998-12-01), Wark et al.
patent: 5866953 (1999-02-01), Akram et al.
patent: 10-347573 (1998-12-01), None

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