Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Die bond
Reexamination Certificate
2002-06-14
2004-07-13
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Die bond
C438S118000
Reexamination Certificate
active
06762504
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to release films used for adhesive films, and particularly release films used for anisotropic conductive adhesive films.
BACKGROUND OF THE INVENTION
Adhesive films have been widely used to bond a semiconductor chip to a wiring board.
Reference
110
in FIG.
5
(
a
) represents an adhesive film of the prior art. Adhesive film
110
comprises a release film
111
and an adhesive layer
118
adhered to the surface of release film
111
.
Release film
111
comprises a substrate
112
and a release agent layer
115
formed on the surface of substrate
112
, and release agent layer
115
is provided on the side of release film
111
adhered to adhesive layer
118
.
Reference
102
in FIG.
5
(
a
) represents a wiring board. Wiring board
102
comprises a base film
103
and metal lines
104
provided on the surface of base film
103
. For connecting this wiring board
102
to a semiconductor chip described below, the side of adhesive film
110
having adhesive layer
118
is first pressed against the side of wiring board
102
having metal lines
104
(FIG.
5
(
b
)).
Generally, release agent layer
115
comprises silicone oil, and the adhesive force between silicone oil (release agent layer) and adhesive layer
118
is lower than the adhesive force between silicone oil and substrate
112
and also lower than the adhesive force between adhesive layer
118
and wiring board
102
, so that release film
111
is separated from adhesive layer
118
and adhesive layer
118
is left on wiring board
102
when release film
111
is separated in the state shown in FIG.
5
(
b
) (FIG.
5
(
c
)).
Reference
105
in FIG.
5
(
d
) represents a semiconductor chip comprising a chip body
106
and bump-like connection terminals
107
formed on one side of chip body
106
. After the side of semiconductor chip
105
having connection terminals
107
is opposed to the side of wiring board
102
having metal lines
104
and the alignment is adjusted, semiconductor chip
105
is pressed against adhesive layer
118
on wiring board
102
and semiconductor chip
105
is heated under pressure in this state so that connection terminals
107
on semiconductor chip
105
come into contact with the surfaces of metal lines
104
on wiring board
102
. Adhesive layer
118
develops adhesiveness by heating to mechanically connect semiconductor chip
105
to wiring board
102
, and an electric device
101
shown in FIG.
5
(
e
) is obtained.
When release film
111
having release agent layer
115
is used to form adhesive film
110
in this manner, release film
111
can be easily separated from adhesive layer
118
to connect wiring board
102
and semiconductor chip
105
.
However, the release agent consisting of silicone oil has low adhesion to substrate
112
, so that release agent layer
115
may be partially removed during preparation of adhesive film
110
or release agent layer
115
may be partially transferred to adhesive layer
118
during separation of release film
111
from adhesive layer
118
.
When release agent layer
115
is removed from release film
111
, adhesive layer
118
and substrate
112
come into direct contact with each other in the areas lacking the release agent layer and the adhesive force to adhesive layer
118
increases in those areas making it difficult to separate adhesive layer
118
from release film
111
.
When release agent layer
115
transferred to the surface of adhesive layer
118
remains, the adhesive force between adhesive layer
118
and semiconductor chip
105
decreases to deteriorate the reliability of the resulting electric device
101
.
As described in JPA 5-154857, it is known to use a releasable substrate such as a fluororesin film as a release film without forming a release agent layer.
However, fluororesin films are normally prepared by stretching and elongating the film during the preparation process so that they tend to vary in thickness, which compromises the precision of the width of the resulting films or the precision of the thickness of the adhesive films formed therewith.
When an adhesive layer is directly provided on the surface of a substrate without release agent, the adhesive force between the adhesive layer and the substrate (release film) directly depends on the surface roughness on the surface of the substrate. Therefore, any variation in surface roughness on the surface of the substrate causes variation in the adhesive force between the adhesive layer and the substrate.
SUMMARY OF THE INVENTION
In one aspect, the present invention relates to a release film comprising a substrate and a release agent layer formed on the surface of the substrate wherein the substrate has a surface roughness of 3 &mgr;m or less on the side having the release agent layer, and the release agent layer is based on a fluorine compound.
In one embodiment, the present invention provides the release film wherein the substrate has a surface roughness of 1 &mgr;m or more and 3 &mgr;m or less on the side having the release agent layer.
In another embodiment, the present invention provides the release film wherein the release agent layer is formed by applying a release agent based on the fluorine compound in an amount of 0.01 g or more and 5 g or less per 1 m
2
on the surface of the substrate.
In another embodiment, the present invention provides the release film wherein the contact angle of the release agent layer to water is between about 100° and about 140° and the contact angle of the release agent layer to silicone oil is between about 30° and about 50°.
In one embodiment, the present invention provides the release film wherein the fluorine compound comprises at least one compound selected from the group consisting of C
6
H
4
(CF
3
)
2
, C
8
F
16
O and C
8
F
18
.
In one embodiment, the present invention provides the release film wherein the substrate has a thickness of between about 12.5 &mgr;m and about 100 &mgr;m.
In one embodiment, the present invention provides the release film wherein the substrate comprises a polyester resin formed in a film and a filler dispersed in the polyester resin.
In one embodiment, the present invention provides an adhesive film comprising a release film and an adhesive layer wherein the release film has a substrate and a release agent layer formed on the surface of the substrate, the substrate having a surface roughness of 3 &mgr;m or less on the side having the release agent layer, and the release agent layer is based on a fluorine compound and the adhesive layer is formed on the surface of the release agent layer.
In one embodiment, the present invention provides the adhesive film wherein the adhesive layer includes a thermosetting resin.
In one embodiment, the present invention provides the adhesive film wherein the thermosetting resin is based on an epoxy resin.
As used herein, the surface roughness means the center line average roughness obtained from the height in direction Z measured by focusing on the surface of an object (substrate) using a laser microscope interferometer (eg, available from Lasertec Corp. sold under the name “Laser Microscope ILM21”).
In release films of particular embodiments in accordance with the present invention, the surface roughness of the substrate is 3 &mgr;m or less. When a release agent layer is formed on the surface of such a substrate and an adhesive layer is formed on the surface of the release agent layer, the surface roughness on the side of the adhesive layer adhered to the release agent layer becomes 2 &mgr;m or less.
If the surface roughness of the adhesive layer is as small as 2 &mgr;m or less, excessive air does not enter between the object and the adhesive layer and any bubbles are not formed between the adhesive layer and the object when the side of the adhesive layer separated from the release film is applied on the object.
If the surface roughness of the substrate is greater than about 1 &mgr;m, the adhesive layer is not separated from the release film when the adhesive film is slit because irregularities on the surface of the rel
Andújar Leonardo
Flynn Nathan J.
Rosenthal & Osha L.L.P.
Sony Chemicals Corp.
LandOfFree
Release films and adhesive films using the release films does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Release films and adhesive films using the release films, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Release films and adhesive films using the release films will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3256895