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DETAILED DESCRIPTION OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a method of preventing the transfer of an
adhesive substance to a ring frame for use in the wafer dicing process, a
pressure-sensitive adhesive sheet used in the above method and a wafer
working sheet having the above pressure-sensitive adhesive sheet.
2. Description of Prior Art
The process for producing a semiconductor device includes a dicing step in
which a semiconductor wafer having circuits formed through necessary
pretreatments is cut and separated into a plurality of chips. In this
step, a dicing sheet for fixing a wafer is stuck to a circular or square
frame known as a ring frame, a semiconductor wafer is stuck on this dicing
sheet and dicing is carried out every circuit to thereby obtain
semiconductor chips.
The dicing step is followed by bonding machine expanding and chip mounting
steps and further by wire bonding and molding steps to thereby complete
production of a semiconductor device. Although the dicing sheet is fixed
on the back of the wafer (chip) from the sticking of the wafer to a chip
pickup step, after the pickup step, the dicing sheet is manually peeled
from the ring frame and the ring frame is cleaned according to necessity
and recycled.
In the conventional dicing sheet, a pressure-sensitive adhesive with low
adhesive strength has been employed to facilitate the pickup. Accordingly,
manual peeling of the dicing sheet from the ring frame has been facile.
However, the conventional dicing sheet having the pressure-sensitive
adhesive with low adhesive strength has been unable to indicate a desired
performance when a single type thereof is employed despite the need for a
tape having higher dicing performance brought about in accordance with the
recent-year trend for increase of semiconductor element integration and
chip enlargement. Thus, a dicing sheet has been developed which can hold
the wafer (chip) at a high adhesive strength during the dicing step but
has its adhesive strength reduced by, for example, ultraviolet irradiation
in the pickup step to thereby enable easy pickup of chips (see, for
example, Japanese Patent Laid-open Publication Nos. 60(1985)-196956 and
61(1986)-28572).
Further, when a chip is die bonded, a die bonding adhesive such as one
composed of an epoxy resin has been applied to the back of the chip. This
operation is extremely time-consuming. Consequently, in recent years, a
dicing sheet has been developed which has an adhesive layer capable of
simultaneously serving as a wafer fixing pressure-sensitive adhesive and
as a die bonding adhesive (see, for example, Japanese Patent Laid-open
Publication Nos. 60(1985)-35531 and 2(1990)-32181).
In the former ultraviolet-curable dicing sheet, the adhesive is less
irradiated with ultraviolet at the part where the dicing sheet is stuck to
the ring frame (overlap width part) although the lowering of the adhesive
strength is marked at the part irradiated with ultraviolet. Thus, peeling
the dicing sheet from the ring frame is difficult because at the overlap
width part the adhesive maintains a high adhesive strength and also its
cohesive strength is small. Even if the peeling is effected, the adhesive
remains on the ring frame (adhesive transfer).
In the latter dicing sheet, the adhesive strength at the interface between
a base sheet and the adhesive layer is often set at low for transferring
the adhesive layer to the chip at the time of chip mounting. Thus, peeling
of the dicing sheet from the ring frame has often been accompanied by
peeling at the interface between the base sheet and the adhesive layer of
the dicing sheet to result in removal of only the base sheet while the
adhesive is left on the ring frame.
This has unfavorably increased the frequency of cleaning for removing the
adhesive from the ring frame and also shortened the life of the ring
frame.
OBJECT OF THE INVENTION
The present invention has been made in view of the above prior art, and its
object is to prevent the transfer of an adhesive substance to the ring
frame,
thereby reducing the frequency of ring frame cleaning to the requisite
minimum and prolonging the life of the ring frame.
SUMMARY OF THE INVENTION
The method of preventing the transfer of an adhesive substance to a dicing
ring frame according to the present invention comprises disposing an
easily releasing layer on a surface intended for dicing sheet sticking of
a dicing ring frame.
The above easily releasing layer is disposed, for example, by applying a
release agent to the surface intended for dicing sheet sticking of the
dicing ring frame.
Further, the present invention provides first and second pressure-sensitive
adhesive sheets, each of which is used to dispose the above easily
releasing layer.
The first pressure-sensitive adhesive sheet of the present invention
comprises a ring-shaped base film and, formed on a surface thereof, a
pressure-sensitive adhesive layer,
the pressure-sensitive adhesive sheet having a size ensuring its fixability
to the dicing ring frame, wherein a adhesive strength between the
pressure-sensitive adhesive layer and the dicing ring frame is smaller
than that between the base film and a dicing sheet.
The second pressure-sensitive adhesive sheet of the present invention
comprises a ring-shaped base film and, formed on a surface thereof, a
pressure-sensitive adhesive layer,
the pressure-sensitive adhesive sheet having a size ensuring its fixability
to the dicing ring frame, wherein the base film has its back subjected
with releasing treatment.
It is preferred that each of the above first and second pressure-sensitive
adhesive sheets have its inner circumference part provided with a stress
relaxation part such as notches.
Still further, the present invention provides a wafer working sheet having
the above pressure-sensitive adhesive sheet for preventing the transfer of
an adhesive substance to a dicing ring frame.
The wafer working sheet of the present invention comprises the above
pressure-sensitive adhesive sheet for preventing the transfer of an
adhesive substance to a dicing ring frame and a dicing sheet,
wherein the pressure-sensitive adhesive sheet is laminated via the base
film thereof to an adhesive layer of the dicing sheet.
The above employed dicing sheet is preferably capable of serving both
dicing and die bonding workings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a ring frame;
FIG. 2 is a sectional view showing the state of support of a wafer;
FIG. 3 is a perspective view of the first pressure-sensitive adhesive sheet
of the present invention;
FIG. 4 is a sectional view on the line X--X of FIG. 3;
FIG. 5 shows the state of use of the first pressure-sensitive adhesive
sheet of the present invention;
FIG. 6 is a perspective view of a modified form of the first
pressure-sensitive adhesive sheet of the present invention;
FIG. 7 is a perspective view of the second pressure-sensitive adhesive
sheet of the present invention;
FIG. 8 is a sectional view on the line Y--Y of FIG. 7; and
FIG. 9 shows the state of use of the second pressure-sensitive adhesive
sheet of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described in greater detail with
reference to the appended drawings.
FIG. 1 shows a typical form of a ring frame 1 suitable for use in the
present invention. The ring frame 1 is generally a shaped article of a
metal or plastic. The ring frame 1 has an inner opening 2 and, its inner
diameter is sized so as to be slightly larger than the diameter of a wafer
to be diced. A flat cut part for guide 3 is formed on part of the
periphery of the ring frame 1. The shape of the ring frame 1 suitable for
use in the present invention is not limited to that shown in FIG. 1 and
any of the conventional ring frames with various shapes can be used.
This ring frame 1 is used with a dicing sheet stuck to its lower side.
Hereinbelow, the side of the ring frame 1 to which the dicing sheet is
stuck will be referred to as "surface intended for dicing sheet sticking
4".
The ring frame 1 has a sectional structure as shown in FIG. 2, and the
dicing sheet 5 is stuck to the surface intended for dicing sheet sticking
4 thereof. A semiconductor wafer 6 is supported by the dicing sheet 5 in
the inner opening 2. Dicing is performed in this state, thereby obtaining
semiconductor chips.
The dicing sheet 5 to be used in the present invention is not particularly
limited and various conventional pressure-sensitive adhesive tapes can be
employed. Examples thereof are as described in, for example, Japanese
Patent Laid-open Publication Nos. 60(1985)-196956, 61(1986)-28572,
60(1985)-35531 and 2(1990)-32181. This dicing sheet 5 is generally
composed of a base 5b and, formed thereon, an adhesive layer 5a.
The method of preventing the transfer of an adhesive substance to the
dicing ring frame according to the present invention is characterized by
applying release agent to the surface intended for dicing sheet sticking 4
of the ring frame 1. Providing the surface intended for dicing sheet
sticking 4 with releasing treatment enables easily peeling the dicing
sheet 5 from the ring frame 1 after completion of necessary process steps
to thereby prevent the transfer of an adhesive substance to the ring frame
1, so that the frequency of cleaning of the ring frame 1 can be minimized
and that the life of the ring frame 1 can be prolonged.
An easily releasing layer can be formed on the surface intended for dicing
sheet sticking 4, for example, by any of the following:
(1) method in which a release agent is applied to the surface intended for
dicing sheet sticking 4;
(2) method in which the first pressure-sensitive adhesive sheet of the
present invention is stuck to the surface intended for dicing sheet
sticking 4; and
(3) method in which the second pressure-sensitive adhesive sheet of the
present invention is stuck to the surface intended for dicing sheet
sticking 4.
In the above method (1), the release agent is selected from among, for
example, fluororesins, silicone resins and olefin resins, depending on the
property of material of the ring frame 1. For example, when the ring frame
1 is made of a metal, a preferred release agent is a fluororesin. When the
ring frame 1 is made of a plastic, a preferred release agent is a silicone
resin.
The above release agent is applied to the surface intended for dicing sheet
sticking 4 by brushing, dipping, printing or the like to thereby provide
the surface subjected with releasing treatment.
This releasing treatment enables not only stably holding the dicing sheet 5
during the dicing but also easily peeling the dicing sheet 5 without
adhesive transfer after the requisite process steps.
A perspective view of the first pressure-sensitive adhesive sheet 7 of the
present invention which is employed in the above method (2) is shown in
FIG. 3, and a sectional view on the line X--X thereof is shown in FIG. 4.
As apparent from FIGS. 3 and 4, the first pressure-sensitive adhesive
sheet 7 is comprised of a ring-shaped base film 8 and, formed on the
surface thereof, a pressure-sensitive adhesive layer 9.
The size of the pressure-sensitive adhesive sheet 7 is satisfactory as long
as it is as large as one enabling fixing the pressure-sensitive adhesive
sheet 7 on the surface intended for dicing sheet sticking 4 of the ring
frame 1. Specifically, it is satisfactory as long as the outer diameter of
the pressure-sensitive adhesive sheet 7 is larger than the diameter of the
inner opening of the ring frame 1.
Examples of suitably employed base films 8 include those which are made of
polyethylene, polypropylene, polyvinyl chloride, polyethylene
terephthalate, ethylene/vinyl acetate copolymer and ionomer resins. The
thickness of each of these films is preferred to range from about 15 to
100 .mu.m.
With respect to the adhesive strength of the pressure-sensitive adhesive
layer 9, it is preferred that, as measured in accordance with Japanese
Industrial Standard Z-0237, the adhesive strength be not greater than 300
g/25 mm and the holding power be at least 70,000 sec. If this adhesive
strength requirement is met, the adhesive transfer is not caused by the
peeling. The pressure-sensitive adhesive constituting the
pressure-sensitive adhesive layer 9 is selected from among, for example,
those based on acrylics, rubbers and silicones. The thickness of the
pressure-sensitive adhesive layer 9 is preferred to range from about 5 to
50 .mu.m.
The above first pressure-sensitive adhesive sheet 7 of the present
invention is stuck to the surface intended for dicing sheet sticking 4 of
the ring frame 1 as shown in FIG. 5.
The adhesive strength A at the interface between the pressure-sensitive
adhesive layer 9 and the ring frame 1 is set at a value lower than the
adhesive strength B at the interface between the base film 8 and the
pressure-sensitive adhesive layer 5a of the dicing sheet 5. The adhesive
strength A at the interface between the pressure-sensitive adhesive layer
9 and the ring frame 1 is preferred to range from about 10 to 300 g/25 mm
and to have an adhesive strength ratio (A/B) of 1/1.5 or below and
especially 1/2 or below. When this adhesive strength ratio cannot be
obtained depending on the performance of the dicing sheet 5, the surface
(surface for dicing sheet sticking) of the base film 8 of the
pressure-sensitive adhesive sheet 7 can be provided with corona treatment
or the like to thereby cause the adhesive strength ratio to fall in the
desirable value range.
When the above pressure-sensitive adhesive sheet 7 is stuck to the surface
intended for dicing sheet sticking 4 of the ring frame 1, the dicing sheet
5 can be stably held during the dicing and, after the requisite process
steps, peeling of the dicing sheet 5 is accompanied by simultaneous
peeling of the pressure-sensitive adhesive sheet 7. The pressure-sensitive
adhesive of the pressure-sensitive adhesive sheet 7 has low adherence, so
that the pressure-sensitive adhesive sheet 7 is peeled without adhesive
transfer.
The above pressure-sensitive adhesive sheet 7 may be stuck to the surface
intended for dicing sheet sticking 4 of the ring frame 1 prior to the use
of the ring frame 1.
Referring to FIG. 6, it is preferred that a stress relaxation part 10 be
formed at the inner circumference part of the pressure-sensitive adhesive
sheet 7. The stress relaxation part 10 is formed, for example, by
providing the inner circumference part of the pressure-sensitive adhesive
sheet 7 with small notches. It is preferred that the notches provided as
the stress relaxation part 10 be formed radially in uniform positional
relationship at the inner circumference part of the pressure-sensitive
adhesive sheet 7. Although the number of notches is not particularly
limited, it is preferred to be at least 4 and, especially, at least 6. The
formation of this stress relaxation part 10 relaxes the stress applied to
the pressure-sensitive adhesive sheet 7 when the dicing sheet 5 is
expanded to thereby prevent the stress from localization, so that the
expansion can be smoothly performed.
A perspective view of the second pressure-sensitive adhesive sheet 11 of
the present invention which is employed in the above method (3) is shown
in FIG. 7, and a sectional view on the line Y--Y thereof is shown in FIG.
8. As apparent from FIGS. 7 and 8, the second pressure-sensitive adhesive
sheet 11 is comprised of a ring-shaped base film 12 and, formed on the
surface thereof, a pressure-sensitive adhesive layer 13.
The size of the pressure-sensitive adhesive sheet 11 is satisfactory as
long as it is as large as one enabling fixing the pressure-sensitive
adhesive sheet 11 on the surface intended for dicing sheet sticking 4 of
the ring frame 1. Specifically, it is satisfactory as long as the outer
diameter of the pressure-sensitive adhesive sheet 11 is larger than the
diameter of the inner opening of the ring frame 1.
The base film 12 can be composed of the same material as employed in the
base film 8 of the above first pressure-sensitive adhesive sheet 7. Its
thickness is preferred to range from about 15 to 100 .mu.m. The back of
the base film 12 is subjected to releasing treatment to thereby form a
releasing treatment surface 14. The releasing treatment is conducted, for
example, by applying a release agent of a fluororesin, a silicone resin,
an olefin resin or the like to the back of the base film 12. This
releasing treatment reduces the adhesive strength between the base film 12
and the dicing sheet 5, thereby enabling peeling the dicing sheet 5
without adhesive transfer.
With respect to the adhesive strength of the pressure-sensitive adhesive
layer 13, it is preferred that, as measured in accordance with Japanese
Industrial Standard Z-0237, the adhesive strength be 200 g/25 mm or
greater and the holding power be at least 70,000 sec. The
pressure-sensitive adhesive constituting the pressure-sensitive adhesive
layer 13 is selected from among, for example, those based on acrylics,
rubbers and silicones. The thickness of the pressure-sensitive adhesive
layer 13 is preferred to range from about 5 to 50 .mu.m.
The above second pressure-sensitive adhesive sheet 11 of the present
invention is stuck to the surface intended for dicing sheet sticking 4 of
the ring frame 1 as shown in FIG. 9.
The adhesive strength C at the interface between the pressure-sensitive
adhesive layer 13 and the ring frame 1 is larger than the adhesive
strength D at the interface between the base film 12 and the
pressure-sensitive adhesive layer 5a of the dicing sheet 5 because of the
releasing treatment surface 14 formed on the back of the base film 12. The
adhesive strength C at the interface between the pressure-sensitive
adhesive layer 13 and the ring frame 1 is preferred to range from about
200 to 1000 g/25 mm and to have an adhesive strength ratio (C/D) of 1.5/1
or higher and especially 2/1 or higher.
When the above pressure-sensitive adhesive sheet 11 is stuck to the surface
intended for dicing sheet sticking 4 of the ring frame 1, the dicing sheet
5 can be stably held during the dicing and, after the requisite process
steps, peeling of the dicing sheet 5 is accompanied by easy peeling at the
interface between the pressure-sensitive adhesive sheet 11 and the dicing
sheet 5. The pressure-sensitive adhesive sheet 11 remains on the ring
frame 1. No adhesive transfer occurs onto the back of the base film 12 of
the pressure-sensitive adhesive sheet 11 remaining on the dicing ring
frame 1. Therefore, the dicing ring frame 1 with the pressure-sensitive
adhesive sheet 11 attached thereto can be recycled.
Repeated use of the dicing ring frame 1 with the pressure-sensitive
adhesive sheet 11 attached thereto may cause the same to suffer from
fouling by friction, etc. However, even at the use limit, peeling is easy
if the adhesive properties of the pressure-sensitive adhesive sheet 11 of
the present invention are as described above, so that the
pressure-sensitive adhesive sheet 11 can be replaced by a new one to
thereby enable recycling the ring frame 1.
The above pressure-sensitive adhesive sheet 11 may be stuck to the surface
intended for dicing sheet sticking 4 of the ring frame 1 prior to the use
of the ring frame 1.
Moreover, it is preferred that a stress relaxation part 10 be formed at the
inner circumference part of the pressure-sensitive adhesive sheet 11 as in
the above first pressure-sensitive adhesive sheet 7.
The wafer working sheet of the present invention will be described below.
The wafer working sheet of the present invention is comprised of the above
pressure-sensitive adhesive sheet 7 or 11 previously laminated onto the
dicing sheet 5. The pressure-sensitive adhesive sheet 7 is laminated in a
manner such that it is stuck via the base film 8 thereof to the adhesive
layer 5a of the dicing sheet 5 (see FIG. 5). The pressure-sensitive
adhesive sheet 11 is laminated in a manner such that the side of releasing
treatment surface 14 of the base film 12 thereof is stuck to the adhesive
layer 5a of the dicing sheet 5 (see FIG. 9).
Not only a dicing sheet intended for exclusive use in dicing working but
also a dicing sheet capable of serving both dicing and die bonding
workings can be used as the dicing sheet 5 as a member of the wafer
working sheet of the present invention.
The dicing sheet intended for exclusive use in dicing working is comprised
of a base 5b and, unpeelably laminated thereto, a pressure-sensitive
adhesive layer 5a.
The pressure-sensitive adhesive of the adhesive layer 5a of the dicing
sheet intended for exclusive use in dicing working may be either one of
the low adhesive strength type adhesive constantly exhibiting low adhesive
strength or one of the ultraviolet-curable type adhesive whose adhesive
strength is lowered by ultraviolet irradiation conducted before the pickup
step.
The pressure-sensitive adhesive of the low adhesive strength type is a
pressure-sensitive adhesive regulated to have a low adhesive strength and
composed of a polymer of an acrylic, a rubber, a silicone or the like
which is capable of exhibiting pressure-sensitive adherence. In the
present invention, it is preferred that an acrylic pressure-sensitive
adhesive be employed from the viewpoint of general-purpose availability,
ease in the control of adherence properties, etc.
The ultraviolet-curable pressure-sensitive adhesive is comprised of a
pressure-sensitive adhesive component and an ultraviolet-curable
component. The above polymer capable of exhibiting pressure sensitivity is
used as the pressure-sensitive adhesive component. A compound having a
carbon-to-carbon double bond or a compound having an oxirane ring is used
as the ultraviolet-curable component to which a photopolymerization
initiator is appropriately added. In particular, those described in
Japanese Patent Laid-open Publication Nos. 60(1985)-196956 and
61(1986)-28572 can suitably be employed.
The above pressure-sensitive adhesive layer of the low adhesive strength
type and the ultraviolet-curable pressure-sensitive adhesive layer each
have a thickness generally ranging from about 1 to 100 .mu.m and
preferably from about 5 to 30 .mu.m.
A general-purpose monolayer or multilayer film of a polyolefin or the like
can be used as the base 5b, one side of the base 5b close to the adhesive
layer 5a may be subjected to corona or primer treatment for increasing the
strength of bond with the adhesive layer 5a. The thickness of the base 5b
generally ranges from about 10 to 300 .mu.m and preferably from about 50
to 200 .mu.m.
The following will describe the dicing sheet capable of serving both dicing
and die bonding workings.
The dicing sheet capable of serving both dicing and die bonding workings is
comprised of a base 5b and, peelably laminated thereto, an adhesive layer
for die fixing.
The adhesive layer for die fixing is pressure sensitive and adherent at
ordinary or elevated temperatures before dicing working. It can stick to a
semiconductor wafer to thereby enable dicing working and can bond a die
and a lead frame, which are strongly bonded and fixed by heat treatment.
As the adhesive for die fixing, there can be mentioned one composed of a
B-stage (semi-cured) thermosetting adhesive component and one composed of
a low-molecular-weight thermosetting adhesive component together with a
polymer component.
An ultraviolet-curable component can further be added to the adhesive layer
for die fixing. Ultraviolet radiation improves the peelability of the thus
obtained adhesive layer from the base to thereby facilitate the pickup
working. For example, those described in Japanese Patent Laid-open
Publication No. 2(1990)-32181 can suitably be employed as the above
adhesive layer for die fixing.
The thickness of the above adhesive layer for die fixing generally ranges
from about 5 to 200 .mu.m and preferably from about 10 to 100 .mu.m.
The base 5b for use in the dicing sheet capable of serving both dicing and
die bonding workings is fundamentally the same as that of the dicing sheet
intended for exclusive use in dicing working.
It is preferred that the base sheet 5b have a surface tension of not
greater than 40 dyn/cm and, especially, not greater than 35 dyn/cm. The
use of the base with this surface tension improves the peelability from
the adhesive layer to thereby improve the pickup adaptability. This base
with low surface tension can be obtained by appropriately selecting the
material or by subjecting the surface of the base with releasing treatment
such as application of a silicone resin or the like.
The procedure of use of the above wafer working sheet is as follows,
although the working sequence can appropriately be altered.
The adhesive layer 5a of the wafer working sheet is stuck to the wafer to
be diced at ordinary or elevated temperature under pressure as shown in
FIG. 5 or 9. Subsequently, the pressure-sensitive adhesive sheet 7 or 11
is stuck to the surface intended for dicing sheet sticking 4 of the ring
frame 1 at ordinary temperature, and the wafer working sheet is fixed with
the ring frame 1. In this state, the wafer is subjected to the steps of
dicing, cleaning and drying.
When the adhesive layer 5a contains the ultraviolet-curable component as
described in Japanese Patent Laid-open Publication Nos. 61(1986)-28572 and
2(1990)-32181, ultraviolet irradiation is carried out prior to the pickup
step to thereby attain peelability improvement.
According to necessity, the wafer working sheet is subjected to the
expanding step. In this step, the presence of the stress relaxation part
on the pressure-sensitive adhesive sheet 7 or 11 leads to desired chip
spacing and alignment.
When the dicing sheet intended for exclusive use in dicing working has been
used in the wafer working sheet, only the die is picked up in the pickup
step and thereafter conventional semiconductor production steps are
carried out.
When the dicing sheet capable of serving both dicing and die bonding
workings has been used in the wafer working sheet, the die is picked up in
the state of having a die fixing adhesive layer laminated thereto and
mounted on the lead frame. Subsequent heat treatment strongly bonds the
die and the lead frame to attain fixing thereof. In any instances, the
above special pressure-sensitive adhesive sheet 7 or 11 is interposed
between the ring frame 1 and the dicing sheet 5, so that the dicing sheet
5 can easily be peeled from the ring frame 1 without the remaining of an
adhesive substance, etc. on the ring frame 1. Therefore, the ring frame 1
has no need of being cleaned and can be recycled as it is.
EFFECT OF THE INVENTION
The present invention enables preventing the transfer of an adhesive
substance to the ring frame, reducing the frequency of cleaning of the
ring frame to the requisite minimum and prolonging the life of the ring
frame.
EXAMPLES
The present invention will further be illustrated with reference to the
following Examples which in no way limits the scope of the invention.
EXAMPLE 1
Fluororesin release agent (Teflon (trade name) FEP Green, produced by E. I.
Du Pont De NEMOURS AND COMPANY) was applied by brushing to ring frame
(MODTF (trade name) 2-6-1, manufactured by DISCO Corp.) so as to obtain a
dry film thickness of 10 .mu.m and dried.
Use was made of a dicing sheet capable of serving both dicing and die
bonding workings which consisted of base (80 .mu.m thick polyolefin), a
pressure-sensitive adhesive (50 .mu.m thick acrylic adhesive containing
thermosetting epoxy resin) and a release film (38 .mu.m thick polyethylene
terephthalate film having one side provided with peeling treatment).
This sheet capable of serving both dicing and die bonding workings was
stuck to the release-agent-coated side of the ring frame. The adhesive
side of the sheet capable of serving both dicing and die bonding workings
was diced under full cut condition and the sheet capable of serving both
dicing and die bonding workings was manually peeled. These were repeated
50 times but no adhesive transfer on the ring frame occurred. Moreover,
the sheet capable of serving both dicing and die bonding workings was
allowed to stand still at 40.degree. C. for 3 days in the state of being
stuck to the release-agent-coated side of the ring frame. Thereafter, the
sheet capable of serving both dicing and die bonding workings was manually
peeled but no adhesive transfer on the ring frame occurred.
EXAMPLE 2
A pressure-sensitive adhesive sheet consisting of a base of polyethylene
terephthalate (25 .mu.m) and a pressure-sensitive acrylic adhesive (M0003
(trade name) produced by Lintec Corporation, amount of coating: 20
g/m.sup.2) was punched in the state of retaining a release film in
conformity to the shape of the overlap width of the ring frame, and
peripheral and inner central unneeded parts were removed.
Subsequently, the same sheet capable of serving both dicing and die bonding
workings as employed in Example 1 was laminated while peeling its release
film to the above punched pressure-sensitive adhesive sheet and cut along
the overlap width of the ring frame.
The adhesive strength between the pressure-sensitive adhesive sheet and the
ring frame was 70 g/25 mm as measured in accordance with Japanese
Industrial Standard Z-0237, and the holding power of the
pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet
was more than 70,000 sec. Further, the adhesive strength at the interface
between the adhesive layer of the sheet capable of serving both dicing and
die bonding workings and the base of the pressure-sensitive adhesive sheet
was 150 g/25 mm.
The laminated sheet was stuck to the ring frame (MODTF (trade name) 2-6-1,
manufactured by DISCO Corp.). The adhesive side of the sheet capable of
serving both dicing and die bonding workings was diced under full cut
condition and the sheet capable of serving both dicing and die bonding
workings was manually peeled from the ring frame. These were repeated 50
times but no adhesive transfer occurred. Moreover, the sheet capable of
serving both dicing and die bonding workings was allowed to stand still at
40.degree. C. for 3 days in the state of being stuck to the ring frame.
Thereafter, the sheet capable of serving both dicing and die bonding
workings was manually peeled. The sheet capable of serving both dicing and
die bonding workings was accurately peeled while holding the
pressure-sensitive adhesive sheet laminated and the ring frame suffered
from no adhesive transfer.
EXAMPLE 3
A silicone release agent was applied in an amount of 0.1 g/m.sup.2 to a
polyethylene terephthalate base (thickness: 25 .mu.m) and a
pressure-sensitive acrylic adhesive (MF (trade name) produced by Lintec
Corporation, amount of coating: 20 g/m.sup.2) was applied to the opposite
side of the base, thereby obtaining a pressure-sensitive adhesive sheet.
The pressure-sensitive adhesive sheet was punched in a manner such that
its periphery agreed with the overlap width of the ring frame and that its
inner circumference agreed with the diameter of the through hole of the
ring frame.
The adhesive strength between the pressure-sensitive adhesive sheet and the
ring frame was 200 g/25 mm as measured in accordance with Japanese
Industrial Standard Z-0237, and the holding power of the
pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet
was more than 70,000 sec. Further, the adhesive strength at the interface
between the adhesive layer of the sheet capable of serving both dicing and
die bonding workings as employed in Example 1 and the base of the
pressure-sensitive adhesive sheet was 15 g/25 mm.
The pressure-sensitive adhesive sheet was stuck to the ring frame (MODTF
(trade name) 2-6-1, manufactured by DISCO Corp.) and then the same sheet
capable of serving both dicing and die bonding workings was stuck thereto.
The adhesive side of the dicing sheet was diced under full cut condition
and the sheet capable of serving both dicing and die bonding workings was
manually peeled. These were repeated 50 times but no adhesive transfer on
the ring frame occurred. Moreover, the sheet capable of serving both
dicing and die bonding workings was allowed to stand still at 40.degree.
C. for 3 days in the state of being stuck to the ring frame. Thereafter,
both the sheet capable of serving both dicing and die bonding workings and
the adhesive sheet was manually peeled but no adhesive transfer on the
ring frame occurred.
EXAMPLE 4
A pressure-sensitive adhesive sheet consisting of a base of soft polyvinyl
chloride (70 .mu.m) and a pressure-sensitive adhesive layer of removable
acrylic pressure-sensitive adhesive (amount of coating: 10 g/m.sup.2) was
prepared. The pressure-sensitive adhesive sheet was punched in the state
of retaining a release film with the use of a cutting edge to thereby
simultaneously conduct formation of a stress relaxation part and removal
of inner central unneeded part.
Subsequently, the same sheet capable of serving both dicing and die bonding
workings as employed in Example 1 was laminated while peeling its release
film to the above punched pressure-sensitive adhesive sheet, thereby
obtaining a wafer working sheet.
The wafer working sheet was formed so as to have an outer diameter of 206
mm, an inner diameter of pressure-sensitive adhesive sheet of 170 mm and a
stress relaxation part radially arranged at eight locations in the
direction from the inner circumferential edge toward the periphery of the
pressure-sensitive adhesive sheet with a size of 10 mm. The adhesive
strength between the pressure-sensitive adhesive sheet and the ring frame
was 190 g/25 mm as measured in accordance with Japanese Industrial
Standard Z-0237, and the holding power of the pressure-sensitive adhesive
layer of the pressure-sensitive adhesive sheet was more than 70,000 sec.
Further, the adhesive strength at the interface between the adhesive layer
of the sheet capable of serving both dicing and die bonding workings and
the base of the pressure-sensitive adhesive sheet was 350 g/25 mm.
The laminated sheet was stuck to the ring frame (MODTF (trade name) 2-6-1,
manufactured by DISCO Corp.). The adhesive side of the sheet capable of
serving both dicing and die bonding workings was diced under full cut
condition and the sheet capable of serving both dicing and die bonding
workings was manually peeled from the ring frame. These were repeated 50
times but no adhesive transfer on the ring frame occurred. Moreover, the
sheet capable of serving both dicing and die bonding workings was allowed
to stand still at 40.degree. C. for 3 days in the state of being stuck to
the ring frame. Thereafter, the sheet capable of serving both dicing and
die bonding workings was manually peeled. The sheet capable of serving
both dicing and die bonding workings was accurately peeled while holding
the pressure-sensitive adhesive sheet of the lower side laminated and the
ring frame suffered from no adhesive transfer.
The wafer working sheet was stuck to a silicon wafer of 6 inch in diameter,
and the silicon wafer was diced into 5 mm.times.5 mm chips by the use of a
dicing device. Thereafter, the wafer working sheet was placed with the
silicon wafer side up on a cylinder of 190 mm in outer diameter and a load
was applied to the ring frame so as to effect a pull down of 15 mm. Thus,
expansion was executed. No local load was applied to the wafer working
sheet and the chip spacing was satisfactory.
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