Metal fusion bonding – Process – Preplacing solid filler
Reexamination Certificate
1997-03-07
2002-10-08
Elve, M. Alexandra (Department: 1725)
Metal fusion bonding
Process
Preplacing solid filler
C228S041000, C228S180220, C228S224000, C228S245000
Reexamination Certificate
active
06460755
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a bump forming method in which conductive balls (represented by solder balls or gold balls) are mounted and formed on the type of semi-conductor package (hereinafter referred to merely as “package”), such as a BGA (Ball Grid Array) package and a CSP (Chip Size Package or Chip Scale Package), in which solder balls are used as a connecting material for connecting an electronic part to a current board. The invention also relates to an apparatus for performing this bump forming method, and to an electronic part formed by this method.
2. Related Art
As shown in
FIGS. 65A and 65B
, in a package such as a BGA package, an LSI chip
2005
is mounted on one side or face of a board
2001
, and terminals of the LSI chip
2005
are connected respectively to terminals of the board
2001
by lead wires
2006
made of gold or gold-plated aluminum, and the LSI chip
2005
is sealed on the board
2001
by a sealing resin
2002
, and then solder bumps
2000
are formed respectively on pads
2003
exposed through a resist film
2004
formed on the other side of the board
2001
.
One method of forming these solder bumps
2000
is disclosed in U.S. Pat. No. 5,284,287. This U.S. Patent discloses a technique in which solder balls, vacuum picked up by an arraying jig (suction jig), are immersed in a flux reservoir, thereby applying a flux to the solder balls, and these solder balls are mounted respectively on pads (connection terminals) formed on an electronic circuit board, and the electronic circuit board, holding the solder balls by the adhesive force of the flux, is heated (reflowed), thereby forming the solder bumps.
U.S. Pat. No. 5,279,045 also discloses a method of forming solder bumps. This U.S. Patent discloses a technique in which solder balls are supplied to an arraying jig (suction jig) by a gas flow, and the solder balls are mounted on a semiconductor device, and then are heated, thereby forming bumps.
FIGS. 66
to
68
show one example of a conventional solder ball mounting machine. Blocks
2
are fixedly mounted on a base
1
in parallel relation to each other. Linear guides
3
are fixedly mounted respectively on the blocks
2
in parallel relation to each other. A beam
4
is movably supported on the linear guides
3
. A feed screw
5
is rotatably supported on the block
2
, and is threadedly engaged with a nut (not shown) fixedly mounted on the beam
4
. A motor
6
is supported on the base
1
, and is connected to the feed screw
5
. Therefore, when the motor
6
is operated, the beam
4
is moved in a Y direction (upward and downward in FIG.
66
).
Linear guides
7
are fixedly mounted on the beam
4
in parallel relation to each other. A slider
8
is movably supported on the linear guides
7
. A feed screw
9
is rotatably supported on the beam
4
, and is threadedly engaged with a nut (not shown) fixedly mounted on the slider
8
. A motor
10
is supported on the beam
4
, and is connected to the feed screw
9
. Therefore, when the motor
10
is operated, the slider
8
is moved in an X direction (right and left in FIG.
66
).
Linear guides
11
are fixedly mounted on the slider
8
in parallel relation to each other. A saddle
12
is movably supported on the linear guides
11
. A feed screw
13
is rotatably supported on the slider
8
, and is threadedly engaged with a nut (not shown) fixedly mounted on the saddle
12
. A motor
14
is fixedly mounted on the slider
8
, and is connected to the feed screw
13
.
Therefore, when the motor
14
is operated, the saddle
12
is moved in a Z direction (upward and downward in FIG.
67
).
An arraying jig (suction jig)
15
is fixedly mounted on the saddle
12
. This arraying jig
15
is formed into a box-like shape, and a plurality of holes
17
for respectively suction-holding solder balls
16
in the same array as the array of solder balls to be mounted on a package are formed in a lower surface of the arraying jig
15
.
A solder ball supply device
19
is fixedly mounted on the base
1
, and holds the solder balls
16
therein. This solder ball supply device
19
is formed into a box-shape having an open top, and a plurality of holes smaller in diameter than the solder ball
16
are formed in its bottom surface.
A flux supply device
20
is fixedly mounted on the base
1
, and the solder balls
16
are immersed a predetermined depth in a flux
21
in this flux supply device
20
, thereby applying the flux
21
to the solder balls
16
.
A package
24
on which the solder balls
16
are to be mounted is conveyed by belts
22
, and is brought into engagement with stoppers
23
to be positioned.
In this construction, the motor
6
and the motor
10
are operated to position the arraying jig
15
above the ball supply device
19
. Then, the motor
14
is operated to move the arraying jig
15
downward until the lower end of the arraying jig
15
covers the open top of the ball supply device
19
. Then, compressed air is injected from the bottom surface of the ball supply device
19
to float the solder balls
16
between the arraying jig
15
and the bottom surface of the ball supply device
19
. At the same time, vacuum pressure is supplied to the arraying jig
15
, thereby drawing the air through the holes (suction holes)
17
, so that the solder balls
16
are suction-held in the holes
17
in the arraying jig
15
.
Upon lapse of a predetermined time period, the compressed air, injected from the bottom surface of the ball supply device
19
, is interrupted, and the motor
14
is operated to move the arraying jig
15
, suction-holding the solder balls
16
, upward.
Then, the motor
6
and the motor
10
are operated to move the arraying jig
15
, suction-holding the solder balls
16
, into a position above the flux supply device
20
. Then, the motor
14
is operated to move the arraying jig
15
downward until the lower ends (about ¼ to ⅓ of the diameter of the solder ball) of the solder balls
16
, suction-held on the lower surface of the arraying jig
15
, are immersed into the flux
21
, thereby supplying the flux
21
to the solder balls
16
. After the flux
21
is thus supplied to the solder balls
16
, the motor
14
is operated to move the arraying jig
15
upward.
Then, the motor
6
and the motor
10
are operated to move the arraying jig
15
, suction-holding the solder balls
16
supplied with the flux at their lower ends, into a position above a mounting position where the solder balls are transferred and mounted onto the package
24
. At this time, the package
24
, positioned in engagement with the stoppers
23
, is beforehand located in the mounting position. When the arraying device
15
is located in the predetermined position above the package
24
, the motor
14
is operated to move the arraying jig
15
downward, so that the solder balls
16
approach the package
24
.
At this time, compressed air is supplied into the arraying jig via a pipe
18
. This compressed air is injected from the holes
17
, so that the suction-held solder balls
16
are released, and are mounted onto the package
24
. The solder balls
16
thus mounted on the package
24
are held on the package
24
by the viscous nature of the flux supplied to the lower ends of the solder balls
16
. Then, the motor
14
is operated to move the arraying jig
15
upward, and the arraying jig
15
is further moved so as to suction hold the next hold solder balls
16
.
However, the above conventional method has the following problems.
In the above solder ball mounting machine, the operations are effected sequentially, and therefore the time required for one cycle is long (about 15 seconds), and the production ability of the solder ball mounting machine is low.
When the kind of the package is changed, the arraying jig must be changed, and the cost, required for preparing many kinds of expensive arraying jigs, and the time and labor, required for changing the arraying jig, offer a problem. In the steps of the above method, one or more solder balls may be omitted i
Hata Izumi
Honda Michiharu
Inoue Kosuke
Iwashita Katsuhiro
Murakami Tetsuo
Antonelli Terry Stout & Kraus LLP
Edmondson Lynne
Elve M. Alexandra
Hitachi , Ltd.
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