Die bonding equipment

Details Die bonding equipment Die bonding equipment

2001-08-06

2004-11-23

Stoner, Kiley (Department: 1725)

Metal fusion bonding

With control means responsive to sensed condition

Work-responsive

C228S049500, C228S105000

Reexamination Certificate

active

06820792

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to die bonding equipment and methods for the fabrication of ball grid packages and more particularly to a die bonding method capable of detecting a failure of a land pattern on a mount tape before a chip transfer unit picks up a chip and capable of matching a good land pattern to a good semiconductor chip and a failed land pattern to a failed semiconductor chip.
2. Description of the Related Art
Recently, technologies for packaging semiconductor chips have rapidly developed with the development of thin film forming technologies. Ball grid array packages, currently in use, are a result of the application of such technologies. A ball grid array package uses a flexible tape in place of a lead frame. The flexible tape includes a conductive pattern formed thereon. One end of the conductive pattern is soldered to terminals of a printed circuit board by a solder ball interposed therebetween, and the other end is bonded to bonding pads that act as input and output terminals of a semiconductor chip.
In the fabrication of ball grid array packages, the process of attaching solder balls is the last step, which provides various advantages in carriage and handling of elements for a die attaching process and in mass production. Ball grid array packages also make unnecessary the trimming and forming processes that are indispensable in fabrication of more conventional packages.
Recently developed chip scale packages have a fine pitch in which the pitch of solder balls ranges from a few tens of microns to a few hundreds of microns and sizes of such packages approach about 120% of the chip sizes.
To form a fine pitch ball grid package, multiple land patterns are first formed on a rectangular, polyimide based tape. Throughholes are formed at selected portions of the polyimide based tape. The land patterns include solder ball pads, which are on a first surface of the polyimide based tape such that each of the pads covers a corresponding throughhole and has a circular plate shape. The land patterns also include conductive patterns that electrically connect to respective solder ball pads and extend to edges of the tape.
Beam leads, that is, the ends of the conductive patterns, are die-bonded to respective bonding pads of semiconductor chip. For such die bonding, rectangular openings or windows are formed at edges of the polyimide based tape. After the die bonding, an electrical test determines whether or not the land patterns have open or short failures and from the electrical test, failed land patterns are marked. An elastomer is attached to a second surface of the polyimide based tape.
Continuously, the polyimide based tape on which the elastomer is attached is rolled, and the rolled tape is cut to length, for example, to include a number of land patterns. Hereinafter, a rolled tape having the above mentioned unit length is referred to as one base mount tape. A base mount tape's edge portions are attached to a square mount tape frame using an adhesive tape.
Semiconductor chips separated by sawing a wafer are transferred to corresponding base mount tapes, and a press head die bonds bonding pads of each of the semiconductor chips with beam leads exposed through open windows of base mount tape.
Afterwards, base mount tapes having semiconductor chips attached are subject to a solder ball attaching process. The solder ball attaching process attaches solder balls to solder ball pads through the throughholes in the base mount tape. The above solder ball attaching process prepares multiple ball grid array packages having a fine pitch. The multiple ball grid array packages are separated into individual ball grid array packages, and the individual ball grid array packages are tested. Thus, the above processes fabricate ball grid array packages.
FIG. 1
shows conventional die bonding equipment
100
for fabrication of ball grid array packages having a fine pitch. Referring to
FIG. 1
, die bonding equipment
100
generally includes a wafer mount frame stocker
5
, a base mount stocker
10
, a chip pickup table
15
, and a bonding unit
20
on a support plate
1
. A chip transfer unit
25
moves a semiconductor chip from the chip pickup table
15
to the bonding unit
20
, and a guide rail unit
40
guides a base mount tape frame
35
from the base mount tape stocker
10
to the bonding unit
20
. Multiple charge coupled device(CCD) cameras observe the operation of die bonding equipment
100
.
In
FIG. 1
, the chip pickup table
15
faces an opening
50
of the wafer mount frame stocker
5
so that a wafer mount frame
45
carrying multiple semiconductor chips can be loaded into or unloaded from the wafer mount frame stocker
5
. A square chip tray
55
that is attached to the chip pickup table
15
receives failed semiconductor chips. The chip tray
55
moves together with the chip pickup table
15
in an X-Y plane.
Meanwhile, an alignment table
65
, which includes a mount head
60
, is spaced apart from the chip pickup table
15
. The mount head
60
receives a semiconductor chip from the chip pickup table
15
, moves the received semiconductor chip to the bonding unit
20
, and aligns the semiconductor chip for die bonding. To align the semiconductor chip, the alignment table
65
can freely move along X-Y coordinate axes as does the chip pickup table
15
, and when the semiconductor chip is skewed from the required orientation for bonding of the chip, the alignment table
65
rotates the skewed semiconductor chip for the required alignment. The alignment table
65
can also move along the Z coordinate axis direction.
Here, the chip transfer unit
25
, which reciprocates between the chip pickup table
15
and the alignment table
65
, transfers semiconductor chips from the wafer mount frame
45
of the chip pickup table
15
. The chip transfer unit
25
includes: a collet
70
(hereinafter referred to as the first collet) for holding good semiconductor chips with a vacuum; a collet
75
(hereinafter referred to as the second collet) for holding failed semiconductor chips; and a moving block
80
including a collet selection unit (not shown) that selects the first or second collet
70
or
75
for use. The chip transfer unit
25
also includes a straight line reciprocating unit (not shown) for transferring the moving block
80
.
The described base mount tape stocker
10
is spaced away from the wafer mount frame stocker
5
. The guide rail unit
40
extends from an opening
85
of the base mount tape stocker
10
, and a base mount tape frame
35
received at the base mount tape stocker
10
is unloaded through the opening
85
. The guide rail unit
40
includes a pair of guide rails
42
and
44
that guide the base mount tape frame
35
. Each of the guide rails has a moving unit (not shown) for moving the base mount tape frame
35
, which is unloaded from the base mount tape stocker
10
.
A bonding unit
20
is over the guide rails
42
and
44
and distant from the base mount tape stocker
10
. The bonding unit
20
includes a press head
22
, which moves up and down, and a bonding unit CCD camera
24
, which moves together with the press head
22
. The press head
22
is over the base mount tape frame
35
, and the mount head
60
is below the base mount tape frame
35
so that the press head
22
faces the mount head
60
. The bonding unit CCD camera
24
checks the position of the base mount tape frame
35
as it moves and simultaneously checks for a failed mark formed during the production of the base mount tape.
In addition to the bonding unit CCD camera
24
, the conventional die bonding equipment typically includes two other CCD cameras. A chip pickup table CCD camera
17
is for determining a position of a failed semiconductor chip or a good semiconductor chip among the chips sawed from a wafer, and an alignment table CCD camera
62
is for checking the alignment of a semiconductor chip on the mount head
60
of the alignment table
65
.
Hereinafter, the operation of the conventional die bonding equipment is

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