Metal fusion bonding – Process – Preplacing solid filler
Reexamination Certificate
2000-09-15
2001-08-28
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Preplacing solid filler
C228S246000, C228S180220, C438S612000, C438S613000
Reexamination Certificate
active
06279816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a process for mounting conductor balls, on terminal pads of semiconductor devices or other electronic devices collectively formed in a single semiconductor wafer or other substrate, stepwise for divisions of the substrate that include different numbers of the devices. The present invention also relates to an adsorbing unit advantageously used in the apparatus and a process and a mask plate suitably used in the adsorbing unit.
2. Description of the Related Art
FIG. 1
shows a conventional semiconductor device
100
of a BGA (ball grid array) type having ball form terminals or solder balls
110
bonded to terminal pads
108
to form external connection terminals on one side of a circuit board
102
. The terminal pads
108
form one end of conductor wiring patterns
106
having the other ends wire-bonded to a semiconductor chip
104
on the other side of the circuit board
102
.
To mount the solder balls
110
on the terminal pads
108
, U.S. Pat. No. 5,284,287 discloses an adsorbing unit for adsorbing the solder balls
110
as shown in FIG.
2
.
The adsorbing unit
100
includes an adsorbing plate
114
having adsorbing holes
112
penetrating therethrough at positions corresponding to the terminal pads
108
of the circuit board
102
and having a diameter smaller than that of the solder balls
110
, in which the adsorbing plate
114
is connected to a vacuum pump system for evacuating the adsorbing holes
112
to adsorb the solder balls
110
at an open end thereof.
As shown in
FIG. 3
, the adsorbing holes
112
are evacuated to adsorb the solder balls
110
contained in a vessel
116
with one adsorbing hole
112
adsorbing one solder ball
110
and the adsorbing plate
114
is then moved to bring the adsorbed solder balls
110
into close contact to the corresponding terminal pads
108
where the adsorbing holes
112
are freed from evacuation to release the solder balls
110
onto the terminal pads
108
, thereby mounting the solder balls
110
on the terminal pads
108
.
As shown in
FIG. 4
, a chip size package (CSP)
200
has substantially the same size as the semiconductor chip
202
packaged therein and having on one side a conductor pattern
206
with one end electrically connected to an electrode terminal
204
of the chip and the other end forming a terminal pad on which a solder ball
208
is mounted to provide a ball-form external connection terminal. The conductor pattern
206
is formed on one side of a resin film
210
. A resilient resin layer
212
is interposed between the conductor pattern
206
and the surface of the semiconductor chip
202
, on which surface the electrode terminal
204
is formed, to absorb thermal stress generated by the different thermal expansion coefficients of the semiconductor chip
202
and a mother board on which the CSP
200
is mounted.
The above-mentioned end of the conductor pattern
206
connected to the electrode terminal
204
protrudes from an edge of the resin film
210
and is sealed or packaged with the electrode terminal
204
by a packaging resin
214
.
The CSP
200
shown in
FIG. 4
is smaller than the BGA type semiconductor device
100
shown in FIG.
1
and is manufactured, as shown in
FIG. 5
, by forming many csPs
200
on many semiconductor elements formed in the wafer
300
and then dicing or cutting the wafer
300
into respective CSPs
200
. FIG.
5
(
a
) shows the whole area of the wafer
300
and FIG.
5
(
b
) is an enlarged partial view showing the circled part P of the wafer
300
.
Before dicing the wafer
300
, the solder balls
208
are mounted on terminal pads of the above-formed semiconductor devices or CSPs
200
. The solder balls
208
are mounted quickly by using the adsorbing unit shown in
FIGS. 2 and 3
.
The wafer
300
is imaginarily divided into plural divisions
302
a
to
302
l
having the same shape and size as that of the adsorbing plate
114
of the adsorbing unit and the mounting of the solder balls
208
is carried out division by division, because the adsorbing plate
114
has a limited actually producible size while ensuring the necessary flatness and other accuracies.
The wafer
300
includes twelve divisions
302
a
to
302
l
, in which four divisions
302
c
,
302
d
,
302
i
and
302
j
have an area occupied by a group of the semiconductor devices
200
(corresponding semiconductor elements
202
are shown in
FIG. 5
) that completely fills each of these four divisions, so that the device-occupied areas of these four divisions have the same shape and size, i.e., have a single pattern. In contrast, eight divisions
302
a
,
302
b
,
302
e
,
302
f
,
302
g
,
302
h
,
302
k
and
302
l
have an area occupied by the semiconductor devices
200
that incompletely fills each of these eight divisions, so that the device-occupied areas of these eight divisions are different in shape and size between divisions, i.e., have eight patterns.
To mount solder balls
208
on terminal pads of semiconductor devices
200
arranged in nine different patterns, it is necessary to prepare adsorbing plates
114
having adsorbing holes
112
arranged in nine different patterns.
The adsorbing plate
114
is very expensive to produce and the cost of producing semiconductor devices is significantly raised by preparing various types of adsorbing plates.
The adsorbing unit shown in
FIGS. 2 and 3
also has a drawback in that the adsorbing plate
114
is fixed to the unit body and exchange of the adsorbing plate
114
is not possible, so that it is extremely difficult, or actually impossible, to quickly mount solder balls
208
on the desired terminal pads with quickly exchanging adsorbing plates
114
.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an apparatus and a process for mounting solder balls or other conductor balls on terminal pads of semiconductor devices or other electronic devices collectively formed on a semiconductor wafer or other substrate by using a single adsorbing plate.
The semiconductor wafer shown in
FIG. 5
has divisions
302
a
to
302
l
in which the semiconductor devices
200
are common to each other in the pitch of terminal pads or other parameters except for the area occupied by the devices
200
that are different between divisions.
Therefore, quick mounting of conductor balls on terminal pads division by division, or stepwise for divisions, by using a single adsorbing plate can be achieved, according to the present invention, by using a mask plate having adsorbing holes arranged corresponding in number and position to the terminal pads of the devices present in the division
302
c
,
302
d
,
302
i
or
302
j
that includes a largest number of the devices and partially masking the adsorbing plate with a mask plate having an opening conformed in shape and size to the device-occupied area of the other divisions, while exchanging the mask plate with another, between divisions, having the device-occupied areas different in shape and size from each other.
According to the first aspect, the present invention provides an apparatus for mounting conductor balls on terminal pads of semiconductor devices. or other electronic devices on a semiconductor wafer or other substrate, stepwise, for divisions of the substrate that include different numbers of the devices, the apparatus including an adsorbing unit which comprises:
an adsorbing head;
an adsorbing plate attached to the head and having adsorbing holes for adsorbing the conductor balls, the adsorbing holes being arranged corresponding in number and position to the terminal pads present in one of the divisions that includes a largest number of the devices; and
a mask plate attached to one side of the adsorbing plate and having an opening conformed in shape and size to an area of the substrate occupied by a group of the devices included in a selected one of the divisions so that the conductor balls are only adsorbed by the adsorbing holes corresponding in position to the terminal pads of the devices of th
Fujimori Yoshiharu
Nakajima Kiyonori
Cooke Colleen
Dunn Tom
Pennie & Edmonds LLP
Shinko Electric Industries Co., Ltd
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