Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With work feeding or handling means
Reexamination Certificate
2000-04-13
2002-02-19
Sells, James (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With work feeding or handling means
C156S580000, C156S583100
Reexamination Certificate
active
06347655
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique to perform die bonding of a semiconductor chip on a lead frame of a semiconductor device with a resin film used as a bonding material.
2. Description of the Background Art
FIGS. 10 and 11
are process diagrams schematically showing a method of bonding a semiconductor chip and a lead frame in a prior-art die bonding device. In both figures, reference numeral
110
denotes a dispenser head, numeral
111
denotes a resin paste, numeral
1
denotes a lead frame for semiconductor device (hereinafter, simply referred to as lead frame) and numeral
2
denotes a semiconductor chip (hereinafter, simply referred to as chip).
First, a transport device (not shown) and a positioning device (not shown) for the lead frame provided in the prior-art die bonding device positions the lead frame
1
at a required position and then the dispenser head
110
guided in a transportable manner above a predetermined region in a bonding pad of the lead frame
1
applies an appropriate amount of resin paste
111
onto the predetermined region (see FIG.
10
).
Next, a chip transfer head (not shown) places the chip
2
on the resin paste
111
applied on the lead frame
1
and applies a required load onto the chip
2
to evenly spread the resin paste
111
between a lower surface of the chip
2
and an upper surface of the lead frame
1
, thereby temporarily bonding the chip
2
and the lead frame
1
(see FIG.
11
). Then, by the above bonding method, similarly, a plurality of chips
2
are temporarily bonded on the lead frame
1
.
After that, for each lead frame
1
, the resin paste
111
is dried in a later curing process to completely bond the chips
2
on the lead frame
1
.
Since the prior-art die bonding device has a constitution for bonding the chip and the lead frame by application of the resin paste, the following roughly-divided two problems (1) and (2) arise.
(1) The first problem lies in that the prior-art bonding method has high probability of creating a void
120
by sucking air into the resin paste
111
, as illustrated in
FIG. 12
, at the same time when the required load is put on the resin paste
111
to evenly apply the paste
111
between the lower surface of the chip
2
and the upper surface of the lead frame
1
in temporary bonding of the chip
2
on the lead frame
1
with the resin paste
111
put therebetween. When the void
120
is produced and left inside the resin paste
111
, the following ill effect may be caused after sealing the chip
2
, inner lead portions (not shown) of the lead frame
1
and the like with a mold resin (not shown). Specifically, when the chip
2
and the like generate heat due to an operation of the semiconductor device, this heat generation raises the temperature of the resin
111
existing between the lower surface of the chip
2
and the upper surface of the lead frame
1
. As a result, the void
120
(of
FIG. 12
) which is babble expands and it is worried that there arises an ill effect that the chip
2
is distorted or damaged by a stress due to this expansion. Further, it is also worried that the expansion force of the void
120
causes a crack in the peripheral mold resin which seals the chip
2
and the like, resulting in an imperfect sealing. Therefore, so long as such an ill effect is expected, there is great necessity of preventing the void
120
from appearing.
(2) The second problem is caused by that it is not sure in which direction the resin paste
111
(of
FIG. 11
) used in the prior art spreads when the load is applied from above through the chip
2
, i.e., unevenness in spreading direction of the resin paste
111
on applying the load. Therefore, if the resin paste
111
spreads one-sidedly when the load is applied, as shown in
FIG. 12
, for example, there may arise a problem that an extending-off portion
112
of the resin paste
111
is developed on one side-surface side from the lower surface of the chip
2
. This extending-off portion
112
also causes the following ill effect. (a) First arises a problem that a sealing region is reduced by the extending-off portion
112
and the thickness of the mold resin may be partially thinned depending on where the chip
2
having the extending-off portion
112
is placed. (b) Second, when the extending-off portion
112
rises up to near the surface of the chip
2
, a wire (not shown) and the extending-off portion
112
may come into contact with each other in a wire bonding process for the chip
2
. At this time, if the resin paste
111
is a pure insulative substance, no problem arises, but the resin paste
111
including silver, for example, is often used and in this case, the paste
111
and the wire become conducting. (c) Third, as shown in
FIG. 12
, a clearance
113
tends to appear on the other end side of the chip
2
and in a later sealing process, the mold resin enters the clearance
113
to weaken the bonding strength between the chip
2
and the lead frame
1
, so that it is worried that the chip
2
tends to be removed off. (d) Additionally, as shown in
FIG. 12
, the chip
2
is not bonded in parallel to the surface of the lead frame
1
and like the case of (c), that weakens the bonding strength between the chip
2
and lead frame
1
, and the mold resin layer over an upper surface of the chip
2
is thinned by the inclination of the chip
2
, which may cause a problem in terms of hermeticity. Therefore, there is great necessity of preventing the extending-off portion
112
from appearing.
SUMMARY OF THE INVENTION
The present invention is directed to a die bonding device. According to a first aspect of the present invention, the die bonding device comprises: a supply unit configured to generate a strap-like resin film from a resin film having stickiness on its back surface and a predetermined thickness, the strap-like resin film having first and second widths in first and second directions, respectively, and the predetermined thickness; a transport unit configured to transport the strap-like resin film to a predetermined region in a surface of a lead frame to bring the back surface of the strap-like resin film into contact with the predetermined region; a heating unit configured to set the temperature of the strap-like resin film to be higher than the room temperature and below the transition temperature of the strap-like resin film; and a pressurizing unit having a pressing portion which is vertically movable, the pressurizing unit configured to pressurize the strap-like resin film from a surface thereof heated by the heating unit, with the pressing portion, to bond the back surface of the strap-like resin film to the predetermined region, and in the die bonding device of the first aspect, the predetermined region has the first and second widths in the first and second directions, respectively.
According to a second aspect of the present invention, in the die bonding device according to the first aspect, the resin film comprises a resin ribbon whose stickiness at the room temperature is lower than that at the transition temperature; and a cover ribbon layered on a surface of the resin ribbon and having a surface of non-stickiness, the strap-like resin film comprises a strap-like resin ribbon; and a strap-like cover ribbon layered on a surface of the strap-like resin ribbon, and the pressing portion of the pressurizing unit pressurizes a surface of the strap-like cover ribbon layered on the surface of the strap-like resin ribbon whose temperature is set to be higher than the room temperature and below the transition temperature of the strap-like resin ribbon, to bond a back surface of the strap-like resin ribbon to the predetermined region, and defining the transport unit, the heating unit, the pressurizing unit and the pressing portion as a first transport unit, a first heating unit, a first pressurizing unit and a first pressing portion, respectively, the die bonding device further comprises: a removing unit configured to remove only the strap-like cover ribbon included in t
Ishitsuka Masahiro
Komemura Toshio
Yamamoto Masahiko
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