Metal fusion bonding – With means to juxtapose and bond plural workpieces – Wire lead bonder
Reexamination Certificate
2000-09-11
2002-10-01
Elve, M. Alexandra (Department: 1725)
Metal fusion bonding
With means to juxtapose and bond plural workpieces
Wire lead bonder
C228S001100
Reexamination Certificate
active
06457627
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a capillary for wire bonding, and in particular for wire bonding for semiconductor devices.
2. Description of the Related Art
Generally, a capillary is formed of a cone-shaped insulating material, and a hole through which a metal wire passes is provided within the capillary.
As shown in
FIGS. 6A and 6B
, this capillary comes in two types, that is, a normal capillary
100
and a bottleneck capillary
102
. These capillaries are distinguished from each other based on the shape of the ends thereof.
The bottleneck capillary
102
is formed in such a manner that an end thereof is made narrow in the transverse direction by shaving off an end of the normal capillary
100
. The length L
1
′ of a face surface
102
A by which compression bonding portions
106
and
108
of a metal wire
104
(see
FIGS. 7A and 7B
) are formed, is shorter than the length L
2
′ of a face surface
100
A of the normal capillary
100
.
FIG.
8
and
FIGS. 9A and 9B
each show a wire bonding method using the normal capillary
100
. In this wire bonding method, bead bonding is employed, in which the metal wire
104
is discharged and melted by an electric torch (not shown in the drawings) and a ball (not shown in the drawings), which will be hereinafter referred to as a “bead”, is formed at an end of the metal wire
104
.
The bead thus formed is compressively bonded onto an electrode pad
110
by the face surface
100
A of the normal capillary
100
, and a compression bonding portion
112
is formed. The compression bonding portion
112
allows one end of the metal wire
104
to be joined to the electrode pad
110
on a semiconductor element
101
.
The other end of the metal wire
104
is compressively bonded by the face surface
100
A of the normal capillary
100
onto a post portion
116
connected to an external electrode of a semiconductor device
114
, and a compression bonding portion
118
is formed. The compression bonding portion
118
allows the other end of the metal wire
104
to be joined to the post portion
116
.
In such a manner as described above, the electrode pad
110
and the post portion
116
are connected by the metal wire
104
. Subsequently, the metal wire
104
is cut off on the compression bonding portion
118
and wiring between the electrode pad
110
and the post portion
116
is thereby completed.
On the other hand,
FIGS. 7A and 7B
show a wire bonding method using the bottleneck capillary
102
.
The length L
1
′ of the face surface
102
A in the bottleneck capillary
102
is shorter than that in the normal capillary
100
. Therefore, the respective areas of the compression bonding portions
106
and
108
formed at the time of wire bonding are each made smaller.
When the semiconductor element
101
(see
FIG. 8
) is of small size and the pitch between electrode pads
120
is short, bonding is not possible in the normal capillary
100
. Therefore, the bottleneck capillary
102
is used. However, in the bottleneck capillary
102
, the area of the compression bonding portion
108
formed on a post portion
122
is also small, and therefore, bonding strength of the post portion
122
decreases.
Further, minuteness of the semiconductor element
101
and reduction in the pitch between the electrode pads
120
have been demanded in recent years, and it is necessary that the face surface
102
A of the bottleneck capillary
102
be reduced in length. Therefore, the area of the compression bonding portion
108
further becomes smaller, and it is difficult to maintain the bonding strength of the post portion
122
.
As a result, when the semiconductor device
114
has a multi-pin structure and is formed as a large-sized package due to a tendency toward the minuteness and a multifunctional structure of the semiconductor element
101
, a stress acting on the compression bonding portion
108
of the post portion
122
becomes larger at the time of resin-sealing of the semiconductor element
101
. Accordingly, it is difficult for the area of the compression bonding portion
108
in the bottleneck capillary
102
in the present state to withstand a stress acting at the time of resin-sealing for the semiconductor element
101
.
In view of the above-described circumstances, it is an object of the present invention to provide a capillary which prevents an electrode pad of a micro-sized and multifunctional semiconductor element from contacting an adjacent wire previously subjected to wiring and which allows the area of a compression bonding region in a post portion to increase.
SUMMARY OF THE INVENTION
In a first aspect of the present invention, there is provided a capillary used for wire bonding, wherein a compression bonding area formed when a metal wire is bonded onto a post portion to be connected to an electrode pad formed on a semiconductor element is made larger than a compression bonding area formed when the metal wire is bonded onto the electrode pad.
Thus, the respective compression bonding areas in the electrode pad and in the post portion can be changed appropriately. Therefore, even when the semiconductor element is of small size and the pitch between electrode pads is short, the compression bonding area on the post portion can be increased.
As a result, the bonding strength of the post portion increases. Even if the semiconductor device has a multi-pin structure and is formed as a large-sized package, the post portion can withstand a stress acting thereon at the time of resin-sealing for the semiconductor element.
In a second aspect of the present invention, there is provided a semiconductor device in which a pitch between post portions respectively connected to electrode pads formed on a semiconductor element is made greater than a pitch between the electrode pads, and a compression bonding area formed when a metal wire is bonded onto the post portion is larger than a compression bonding area formed when the metal wire is bonded onto the electrode pad.
The pitch between the post portions is made greater than the pitch between electrode pads. Therefore, even if the compression bonding area formed by bonding for the post portion is made larger than the compression bonding area formed by bonding for the electrode pad, short circuits do not occur between the post portions.
In a third aspect of the present invention, an accommodating portion is provided at an end of the capillary main body, and a movable portion through which a wire passes is accommodated in the accommodating portion. The movable portion slides to protrude from the end of the capillary main body, wherein further movement in this direction is prevented. Further, urging means is accommodated in the accommodating portion and urges the movable portion toward the end of the capillary main body.
When a metal wire is bonded onto the electrode pad formed on the semiconductor element, a molten metal wire is compressively bonded by the movable portion using pressing means. Further, when the metal wire is bonded onto a post portion to be connected to the electrode pad, the metal wire is compressively bonded by the movable portion and the end of the capillary main body, using the pressing means.
So long as the movable portion is thus made to slide, when bonding is carried out for the electrode pad, the metal wire can be compressively bonded only by the movable portion. Further, when bonding is carried out for the post portion, the metal wire can be compressively bonded by the end of the capillary main body and the movable portion acting together.
As a result, respective functions of a normal capillary and a bottleneck capillary can be provided by a single capillary. Moreover, the compression bonding area in the post portion can be easily made larger than the compression bonding area in the electrode pad.
In a fourth aspect of the present invention, the accommodating portion includes an inner peripheral surface having a groove defined therein and extending in a direction that the movable portion slides, and the movable portion in
Cooke Colleen P.
Elve M. Alexandra
Oki Electric Industry Co. Ltd.
Rabin & Berdo P.C.
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