U.S. patent application number 15/541630 was filed with the patent office on 2017-11-02 for flexible laminated board and multilayer circuit board.
The applicant listed for this patent is UBE EXSYMO CO., LTD.. Invention is credited to Takao ARIMA, Junya KASAHARA, Kouji KONDOH, Eijirou MIYAGAWA, Taro SUZUKI, Eisuke TACHIBANA, Makoto TOTANI.
Application Number | 20170318670 15/541630 |
Document ID | / |
Family ID | 56405806 |
Filed Date | 2017-11-02 |
United States Patent
Application |
20170318670 |
Kind Code |
A1 |
TACHIBANA; Eisuke ; et
al. |
November 2, 2017 |
FLEXIBLE LAMINATED BOARD AND MULTILAYER CIRCUIT BOARD
Abstract
A flexible laminated sheet manufacturing method includes
thermocompression-bonding an insulation film formed of a liquid
crystal polymer onto a metal foil between endless belts to form a
flexible laminated sheet. The thermocompression bonding includes
heating the flexible laminated sheet so that the maximum
temperature of the sheet is in the range from a temperature that is
45.degree. C. lower than the melting point of the liquid crystal
polymer to a temperature that is 5.degree. C. lower than the
melting point. The thermocompression bonding also includes slowly
cooling the flexible laminated sheet so that an exit temperature,
which is a temperature of the sheet when transferred out of the
endless belts, is in the range from a temperature that is
235.degree. C. lower than the melting point of the liquid crystal
polymer to a temperature that is 100.degree. C. lower than the
melting point.
Inventors: |
TACHIBANA; Eisuke; (Tokyo,
JP) ; SUZUKI; Taro; (Tokyo, JP) ; TOTANI;
Makoto; (Kariya-shi, JP) ; KONDOH; Kouji;
(Kariya-shi, JP) ; MIYAGAWA; Eijirou; (Kariya-shi,
JP) ; KASAHARA; Junya; (Tokyo, JP) ; ARIMA;
Takao; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UBE EXSYMO CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
56405806 |
Appl. No.: |
15/541630 |
Filed: |
January 12, 2016 |
PCT Filed: |
January 12, 2016 |
PCT NO: |
PCT/JP2016/050709 |
371 Date: |
July 5, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 2307/546 20130101;
B32B 2405/00 20130101; B32B 7/04 20130101; B32B 7/06 20130101; B32B
2307/302 20130101; H05K 3/4655 20130101; B32B 37/1027 20130101;
H05K 1/115 20130101; B32B 2307/306 20130101; H05K 2201/0141
20130101; H05K 3/227 20130101; B32B 2309/02 20130101; B32B 2250/02
20130101; H05K 1/0393 20130101; B32B 15/20 20130101; H05K 2203/1194
20130101; B32B 2250/40 20130101; B32B 15/08 20130101; B32B 15/098
20130101; B32B 27/283 20130101; B32B 37/08 20130101; B32B 37/06
20130101; B32B 15/088 20130101; B32B 2307/50 20130101; B32B 3/08
20130101; B32B 2309/04 20130101; H05K 2201/068 20130101; H05K
2203/066 20130101; B32B 2457/20 20130101; H05K 3/067 20130101; B32B
37/10 20130101; B32B 2250/03 20130101; B32B 2307/538 20130101; B32B
27/28 20130101; B32B 15/09 20130101; H05K 2203/1545 20130101; H05K
3/022 20130101; B32B 2307/732 20130101; B32B 27/281 20130101; B32B
2307/734 20130101; B32B 2307/30 20130101; H05K 1/09 20130101; H05K
2201/0191 20130101; B32B 27/42 20130101; B32B 2307/748 20130101;
B32B 2457/08 20130101; B32B 27/36 20130101; B32B 15/18
20130101 |
International
Class: |
H05K 1/03 20060101
H05K001/03; B32B 37/06 20060101 B32B037/06; B32B 37/10 20060101
B32B037/10; H05K 3/46 20060101 H05K003/46; H05K 1/11 20060101
H05K001/11; B32B 15/08 20060101 B32B015/08; H05K 1/09 20060101
H05K001/09; B32B 37/08 20060101 B32B037/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 2015 |
JP |
2015-004337 |
Jan 13, 2015 |
JP |
2015-004338 |
Claims
2. A method for manufacturing a flexible laminated sheet, the
method comprising steps of: continuously feeding an insulation film
formed of a liquid crystal polymer and a metal foil between a pair
of two endless belts; and thermocompression-bonding the insulation
film onto the metal foil between the endless belts to form a
flexible laminated sheet, wherein the step of thermocompression
bonding includes heating the flexible laminated sheet so that the
maximum temperature of the flexible laminated sheet is in the range
from a temperature that is 45.degree. C. lower than the melting
point of the liquid crystal polymer of the insulation film to a
temperature that is 5.degree. C. lower than the melting point, and
slowly cooling the flexible laminated sheet so that an exit
temperature, which is a temperature of the flexible laminated sheet
when transferred out of the endless belts, is in the range from a
temperature that is 235.degree. C. lower than the melting point of
the liquid crystal polymer of the insulation film to a temperature
that is 100.degree. C. lower than the melting point.
3. The method for manufacturing a flexible laminated sheet
according to claim 2, wherein the insulation film is formed of a
liquid crystal polymer containing as constituent units
6-hydroxy-2-naphthoic acid and para-hydroxybenzoic acid and having
a melting point in excess of 250.degree. C.
4. The method for manufacturing a flexible laminated sheet
according to claim 2, wherein the metal foil is at least one
selected from the group consisting of a copper foil, an aluminum
foil, a stainless steel foil, and a foil formed of an alloy of
copper and aluminum.
5. A method for manufacturing a laminated sheet that is formed by
laminating an insulation film formed of a polymer of
6-hydroxy-2-naphthoic acid and 4-hydroxybenzoic acid and a metal
foil together and used to manufacture a multilayer circuit board,
the method comprising steps of: drying the insulation film by
heating the insulation film at a temperature of 120.degree. C. to
250.degree. C. for 20 seconds or longer; and
thermocompression-bonding the dried insulation film onto the metal
foil to form a laminated sheet by pressing the dried insulation
film and the metal foil against each other with a pressure of 0.5
MPa to 10 MPa for 10 seconds to 600 seconds while heating the dried
insulation film and the metal foil at a temperature of 250.degree.
C. to 330.degree. C., wherein the insulation film obtained by
removing the metal foil from the laminated sheet after the step of
thermocompression bonding has a maximum deformation rate of less
than or equal to 0.85% at 250.degree. C. to 300.degree. C. measured
with a dynamic viscoelasticity measurement device under the
conditions in which the dynamic load is 15 g, the frequency is 1
Hz, and the rate of temperature increase is 5.degree. C./min while
controlling the dynamic stress and the static load in a dynamic
stress control mode and an automatic static load mode.
6. A multilayer circuit board formed by laminating a plurality of
pattern films into a multilayer, wherein each pattern film is
formed by circuit-processing the laminated sheet obtained through
the method for manufacturing a laminated sheet according to claim
5, and wherein the insulation film contained in each of the pattern
films includes a via hole filled with an interlayer connection
material.
Description
TECHNICAL FIELD
[0001] The present invention relates to a flexible laminated sheet
and a multilayer circuit board.
BACKGROUND ART
[0002] A flexible laminated sheet in which an insulation layer and
a metal layer are bonded together is used as, for example, a
material for manufacturing a flexible printed wiring board. A
flexible laminated sheet that uses a liquid crystal polymer, which
is a low-dielectric material, in an insulation layer is drawing
attention because there is a need to increase the frequency of the
flexible printed wiring board.
[0003] For example, patent document 1 discloses a technique in
which a double belt press device is used to place a metal foil on
each surface of an insulation film formed of a liquid crystal
polymer and then thermocompression-molding the metal foils and the
insulation film to manufacture a flexible laminated sheet in which
the insulation film and the metal foils have been
thermocompression-bonded together. Further, patent document 1
discloses that the occurrence of dimensional distortion or the like
can be reduced in the manufactured flexible laminated sheet while
maintaining the peel strength between the insulation layer and the
metal foils by setting the heating temperature during the
thermocompression molding to the range from a temperature that is
equal to the melting point of the liquid crystal polymer of the
insulation film to a temperature that is 20.degree. C. higher than
the same melting point.
[0004] Patent document 2 discloses a method for manufacturing a
multilayer circuit board that includes laminating a plurality of
pattern films each including an insulation film formed of a
thermoplastic resin and a conductor pattern formed in the surface
of the insulation film and integrally bonding the pattern films
with a heating press into a multilayer. In the pattern film used
for manufacturing the multilayer circuit board, an insulation layer
formed of the insulation film includes a via hole, and the via hole
is filled with an interlayer connection material. The interlayer
connection material, with which the via hole is filled, ensures
conduction between the layers in the multilayer circuit board.
PRIOR ART DOCUMENTS
Patent Documents
[0005] Patent Document 1: Japanese Laid-Open Patent Publication No.
2010-221694
[0006] Patent Document 2: Japanese Laid-Open Patent Publication No.
2003-23250
SUMMARY OF THE INVENTION
Problems that are tbo e Solved by the Invention
[0007] The progress in technology for increasing the mounting
density on a flexible printed wiring board has resulted in the need
for a flexible laminated sheet having a small dimensional change
rate. More specifically, there is a need for a flexible laminated
sheet having a small dimensional change rate between before and
after forming a conductor circuit and between before and after a
heating process that performs reflow-soldering to mount various
elements.
[0008] When manufacturing multilayer circuit boards in each of
which pattern films are used that each include an insulation film
formed of a different liquid crystal polymer, conduction failures
between the layers of each multilayer circuit board occurs more
often when using an insulation film formed of a type II liquid
crystal polymer than when using an insulation film formed of a type
I liquid crystal polymer. This may be because conduction between
the layers through the interlayer connection material is
interrupted by the softened liquid crystal polymer that flows into
the via hole when integrating the pattern films with the heating
press.
[0009] The present invention is made in view of such circumstances,
and its objective is to provide a flexible laminated sheet having a
small dimensional change rate. It is another objective of the
present invention to provide a method for manufacturing a laminated
sheet that uses an insulation film formed of a type II liquid
crystal polymer and reduces, when forming a multilayer circuit
board, conduction failures between the layers and to provide a
multilayer circuit board that reduces conduction failures between
the layers.
Means for Solving the Problems
[0010] To achieve the above objectives and in accordance with one
aspect of the present invention, a flexible laminated sheet is
provided that includes an insulation layer formed of a liquid
crystal polymer and a metal layer formed on one surface or each of
both surfaces of the insulation layer. The liquid crystal polymer
has a melting point in excess of 250.degree. C. The flexible
laminated sheet has a dimensional change rate in the range of
.+-.0.05% when a heating temperature is 250.degree. C. in a
dimensional stability test defined in Japanese Industrial Standards
JIS C 6471. The insulation layer has a standard deviation of
thickness of less than or equal to 1.2 .mu.m in a widthwise
direction of the insulation layer.
[0011] To achieve the above objectives and in accordance with
another aspect of the present invention, a method for manufacturing
a flexible laminated sheet is provided that includes a step of
continuously feeding an insulation film formed of a liquid crystal
polymer and a metal foil between a pair of two endless belts and a
step of thermocompression-bonding the insulation film onto the
metal foil between the endless belts to form a flexible laminated
sheet. The step of thermocompression bonding includes heating the
flexible laminated sheet so that the maximum temperature of the
flexible laminated sheet is in the range from a temperature that is
45.degree. C. lower than the melting point of the liquid crystal
polymer of the insulation film to a temperature that is 5.degree.
C. lower than the same melting point. The step of thermocompression
bonding also includes slowly cooling the flexible laminated sheet
so that an exit temperature, which is a temperature of the flexible
laminated sheet when transferred out of the endless belts, is in
the range from a temperature that is 235.degree. C. lower than the
melting point of the liquid crystal polymer of the insulation film
to a temperature that is 100.degree. C. lower than the same melting
point.
[0012] In the method for manufacturing a flexible laminated sheet,
it is preferred that the insulation film be formed of a liquid
crystal polymer containing as constituent units
6-hydroxy-2-naphthoic acid and para-hydroxybenzoic acid and having
a melting point in excess of 250.degree. C.
[0013] In the method for manufacturing a flexible laminated sheet,
it is preferred that the metal foil be at least one selected from
the group consisting of a copper foil, an aluminum foil, a
stainless steel foil, and a foil formed of an alloy of copper and
aluminum.
[0014] To achieve the above objectives and in accordance with a
further aspect of the present invention, a method for manufacturing
a laminated sheet is provided that is formed by laminating an
insulation film formed of a polymer of 6-hydroxy-2-naphthoic acid
and 4-hydroxybenzoic acid and a metal foil together and used to
manufacture a multilayer circuit board. The method includes a step
of drying the insulation film by heating the insulation film at a
temperature of 120.degree. C. to 250.degree. C. for 20 seconds or
longer and a step of thermocompression-bonding the dried insulation
film onto the metal foil to form a laminated sheet by pressing the
dried insulation film and the metal foil against each other with a
pressure of 0.5 MPa to 10 MPa for 10 seconds to 600 seconds while
heating the dried insulation film and the metal foil at a
temperature of 250.degree. C. to 330.degree. C. The insulation film
obtained by removing the metal foil from the laminated sheet after
the step of thermocompression bonding has a maximum deformation
rate of less than or equal to 0.85% at 250.degree. C. to
300.degree. C. measured with a dynamic viscoelasticity measurement
device under the conditions in which the dynamic load is 15 g, the
frequency is 1 Hz, and the rate of temperature increase is
5.degree. C./min while controlling the dynamic stress and the
static load in a dynamic stress control mode and an automatic
static load mode.
[0015] To achieve the above objectives and in accordance with a
still another aspect of the present invention, a multilayer circuit
board is provided that is formed by laminating a plurality of
pattern films into a multilayer. Each pattern film is formed by
circuit-processing the laminated sheet obtained through the method
for manufacturing a laminated sheet. The insulation film contained
in each of the pattern films includes a via hole filled with an
interlayer connection material.
EFFECTS OF THE INVENTION
[0016] The present invention succeeds in providing a flexible
laminated sheet having a small dimensional change rate. Further,
the present invention succeeds in reducing conduction failures
between the layers of a multilayer circuit board.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic view showing a thermocompression
bonding step according to one embodiment of the present
invention.
[0018] FIG. 2 is a schematic view showing a thermocompression
bonding step of a modified embodiment.
MODES FOR CARRYING OUT THE INVENTION
First Embodiment
[0019] One embodiment of a flexible laminated sheet manufacturing
method of the present invention will now be described in detail
with reference to FIG. 1.
[0020] A method for manufacturing a flexible laminated sheet 10 of
the present embodiment includes a thermocompression bonding step of
continuously thermocompression-bonding a metal foil 12 onto each
surface of an insulation film 11. The flexible laminated sheet 10
is manufactured through the thermocompression bonding step.
[0021] First, the insulation film 11 and the metal foils 12 used
for manufacturing the flexible laminated sheet 10 will be
described.
[0022] The insulation film 11 forms an insulation layer of the
flexible laminated sheet 10. The insulation film 11 is formed of a
liquid crystal polymer having a melting point in excess of
250.degree. C. Examples of such a liquid crystal polymer include a
liquid crystal polymer containing as constituent units ethylene
terephthalate and para-hydroxybenzoic acid, a liquid crystal
polymer containing as constituent units phenol, phthalic acid, and
para-hydroxybenzoic acid, and a liquid crystal polymer containing
as constituent units 6-hydroxy-2-naphthoic acid and
para-hydroxybenzoic acid.
[0023] The thickness of the insulation film 11 is not particularly
limited. However, the thickness of the insulation film 11 is
preferably in the range from 6 .mu.m to 300 .mu.m, more preferably
in the range from 12 .mu.m to 150 .mu.m, and further preferably in
the range from 25 .mu.m to 100 .mu.m.
[0024] The metal foil 12 forms a metal layer of the flexible
laminated sheet 10. A metal foil such as a copper foil, an aluminum
foil, a stainless steel foil, and a foil formed of an alloy of
copper and aluminum can be used as the metal foil 12. In
particular, it is preferred that at least one selected from a
rolled copper foil, an electrolytic copper foil, and an aluminum
foil be used as the metal foil 12.
[0025] The surface roughness of the metal foil 12 is not
particularly limited. However, the ten point height of roughness
profile (Rz) of the metal foil 12 is preferably in the range from
0.5 .mu.m to 10 .mu.m and more preferably in the range from 0.5
.mu.m to 7 .mu.m. The thickness of the metal foil 12 is not
particularly limited. However, the thickness of the metal foil 12
is preferably in the range from 1.5 .mu.m to 150 .mu.m, more
preferably in the range from 2 .mu.m to 70 .mu.m, and further
preferably in the range from 9 .mu.m to 35 .mu.m.
[0026] Next, the thermocompression bonding step of the
manufacturing method of the present embodiment will be
described.
[0027] As shown in FIG. 1, the thermocompression bonding step is
performed on a production line including a double belt press device
20, a feeding unit 30 that feeds the insulation film 11 and the
metal foils 12 to the double belt press device 20, and a winding
unit 40 that winds the flexible laminated sheet 10 transferred out
of the double belt press device 20.
[0028] The double belt press device 20 includes a pair of upper
drums 21, which are spaced apart from each other by a predetermined
distance in a transfer direction, and a pair of lower drums 22,
which are located below the upper drums 21 and also spaced apart
from each other by a predetermined distance in the transfer
direction. An endless belt 23 runs around the pair of upper drums
21. The endless belt 23 is configured to rotate when the pair of
upper drums 21 rotate. In the same manner, an endless belt 24 runs
around the pair of lower drums 22. The endless belt 24 is
configured to rotate when the pair of lower drums 22 rotate. The
endless belts 23 and 24 are formed of, for example, a metal
material such as stainless steel, copper alloy, or aluminum
alloy.
[0029] A thermocompression device 25 is provided inside each of the
endless belts 23 and 24. The thermocompression devices 25 are
arranged one upon the other sandwiching the endless belts 23 and
24. The thermocompression devices 25 apply a predetermined pressure
to portions of the endless belts 23 and 24 located between the
thermocompression devices 25 and heat the portions. The
thermocompression devices 25 are configured to be capable of
adjusting the heating temperature of each of predetermined ranges
in the transfer direction. For example, for the thermocompression
devices 25 shown in FIG. 1, the heating temperature of each of four
portions 25A to 25D, which are arranged in the transfer direction,
is adjusted individually.
[0030] The feeding unit 30 includes an insulation film roll 31 in
which the elongated insulation film 11 is wound into a roll and a
set of metal foil rolls 32 in which the elongated metal foils 12
are wound into rolls.
[0031] In the thermocompression bonding step, first, the metal
foils 12 fed from the metal foil rolls 32 are placed on both
surfaces of the insulation film 11 fed from the insulation film
roll 31 of the feeding unit 30 and continuously fed to the double
belt press device 20. When the endless belts 23 and 24 rotate, the
insulation film 11 and the metal foils 12 fed to the double belt
press device 20 are transferred downstream in a state held between
the endless belts 23 and 24.
[0032] When passing between the endless belts 23 and 24, the
thermocompression device 25 applies a predetermined contact
pressure to the insulation film 11 and the metal foils 12 through
the endless belts 23 and 24. Simultaneously, the thermocompression
device 25 heats the insulation film 11 and the metal foils 12
through the endless belts 23 and 24. This softens the insulation
film 11 and thermocompression-bonds the insulation film 11 to the
metal foil 12 to form the flexible laminated sheet 10, in which a
metal layer is provided on each surface of an insulation layer. The
flexible laminated sheet 10 transferred out of the double belt
press device 20 is recovered and wound into a roll by the winding
unit 40.
[0033] In the thermocompression bonding step, the insulation film
11 and the metal foils 12 are heated as described below. More
specifically, at an upstream region (heating zone) between the
endless belts 23 and 24, the insulation film 11 and the metal foils
12 are heated to a first temperature T1. At a downstream region
(slow cooling zone) between the endless belts 23 and 24, the heat
applied to the insulation film 11 and the metal foils 12 is reduced
to slowly cool the insulation film 11 and the metal foils 12 so
that the flexible laminated sheet 10 is transferred out of the
double belt press device 20 at a second temperature T2 that is
lower than the first temperature T1. In other words, the heating is
performed so that the maximum temperature of the flexible laminated
sheet 10 (insulation film 11 and metal foils 12) when passing
between the endless belts 23 and 24 is the first temperature T1 and
an exit temperature, which is the temperature of the flexible
laminated sheet 10 when transferred out of the endless belts 23 and
24, is the second temperature T2. At a boundary portion between the
heating zone and the slow cooling zone, the mode of heating is
changed while maintaining a state in which the predetermined
contact pressure is applied to the flexible laminated sheet 10
(insulation film 11 and metal foils 12).
[0034] When the melting point of the liquid crystal polymer of the
insulation film 11 is expressed by mp, the first temperature T1 is
in the range of "mp-45.degree. C..ltoreq.T1.ltoreq.mp-5.degree. C."
That is, the first temperature T1 is in the range from a
temperature that is 45.degree. C. lower than the melting point of
the liquid crystal polymer to a temperature that is 5.degree. C.
lower than same melting point. For example, when the melting point
of the liquid crystal polymer of the insulation film 11 is
335.degree. C., the first temperature T1 is in the range of
"290.degree. C. T1.ltoreq.330.degree. C." The lower limit of the
first temperature T1 expressed by "mp-45.degree. C." is the minimum
temperature required to sufficiently bond the insulation film 11 to
the metal foils 12.
[0035] The upper limit of the first temperature T1 expressed by
"mp-5.degree. C." is the maximum temperature that limits the
melting of the liquid crystal polymer of the insulation film 11.
Once the liquid crystal polymer melts, the flow of the liquid
crystal polymer disturbs the molecular orientation. This causes
residual stress in the formed flexible laminated sheet 10. In this
case, when the flexible laminated sheet 10 is heated again, large
dimensional changes will occur. When the upper limit of the first
temperature T1 is "mp-5.degree. C." to restrict the melting and
flow of the liquid crystal polymer, such a problem will seldom
occur. This reduces the dimensional change rate of the flexible
laminated sheet 10 between before and after the heating process is
performed.
[0036] When the melting point of the liquid crystal polymer of the
insulation film 11 is expressed by mp, the second temperature T2 is
in the range of "mp-235.degree. C..ltoreq.T2.ltoreq.mp-100.degree.
C." That is, the second temperature T2 is in the range from a
temperature that is 235.degree. C. lower than the melting point of
the liquid crystal polymer to a temperature that is 100.degree. C.
lower than same melting point. For example, when the melting point
of the liquid crystal polymer of the insulation film 11 is
335.degree. C., the second temperature T2 is in the range of
"100.degree. C..ltoreq.T2.ltoreq.235.degree. C." Slow cooling
performed with the second temperature T2 in the above range
decreases the influence of orientation changes caused by the flow
of the liquid crystal polymer that occurs when the temperature
reaches the first temperature T1. This reduces the dimensional
change rate of the flexible laminated sheet 10 between before and
after the heating process is performed.
[0037] The first temperature T1 can be checked by measuring the
temperature of the flexible laminated sheet 10 when passing by a
position in the thermocompression device 25 where the heating
temperature turns to decrease. For example, in the
thermocompression device 25 shown in FIG. 1, when the portions 25A
and 25B serve as the heating zones that perform high-temperature
heating to heat the flexible laminated sheet to the first
temperature T1 and when the portions 25C and 25D serve as the slow
cooling zones that perform low-temperature heating to heat the
flexible laminated sheet to the second temperature T2, the first
temperature T1 can be checked by measuring the temperature of the
flexible laminated sheet 10 when passing by a position
corresponding to the boundary between the portions 25B and 25C. The
second temperature T2 can be checked by measuring the temperature
of the flexible laminated sheet 10 immediately after transferred
out of the endless belts 23 and 24.
[0038] It is preferred that the difference between the first
temperature T1 and the second temperature T2, T1-T2, be in the
range from 55.degree. C. to 230.degree. C. It is preferred that the
ratio of the first temperature T1 and the second temperature T2,
T1/T2, be in the range from 1.2 to 3.3.
[0039] The contact pressure applied to the insulation film 11 and
the metal foils 12 when passing between the endless belts 23 and 24
is, for example, preferably in the range from 0.5 MPa to 6.0 MPa
and more preferably in the range from 1.5 MPa to 5.0 MPa.
[0040] The flexible laminated sheet 10 manufactured through the
above thermocompression bonding step has a small dimensional change
rate. For example, the dimensional change rate is in the range of
.+-.0.05% when the heating temperature is 250.degree. C. in a
dimensional stability test defined in Japanese Industrial Standards
(JIS) C 6471-1995. Further, the flexible laminated sheet 10 has
small thickness variation. For example, the standard deviation of
thickness of the insulation layer is less than or equal to 1.2
.mu.m in the widthwise direction of the insulation layer.
[0041] The flexible laminated sheet 10 obtained through the
manufacturing method of the present embodiment is used for a
flexible printed board and may be used as a tape used in a mounting
technique such as the tape automated bonding (TAB) technique and
the chip on film (COF) technique. Examples of the products having
the flexible laminated sheet 10 include electric devices such as a
camera, a personal computer, a liquid crystal display, a printer,
and a mobile device.
[0042] The advantages of the present embodiment will now be
described.
[0043] The method for manufacturing a flexible laminated sheet
includes a step of continuously feeding an insulation film 11
formed of a liquid crystal polymer and metal foils 12 between a
pair of endless belts 23 and 24 and a step of
thermocompression-bonding the insulation film 11 to the metal foils
12 between the endless belts 23 and 24 to form a flexible laminated
sheet 10.
[0044] The thermocompression bonding step includes heating the
flexible laminated sheet 10 so that the maximum temperature (first
temperature T1) of the flexible laminated sheet 10 is in the range
from a temperature that is 45.degree. C. lower than the melting
point of the liquid crystal polymer of the insulation film 11 to a
temperature that is 5.degree. C. lower than the same melting point.
The thermocompression bonding step also includes slowly cooling the
flexible laminated sheet 10 so that an exit temperature (second
temperature T2), which is a temperature of the flexible laminated
sheet 10 when transferred out of the endless belts 23 and 24, is in
the range from a temperature that is 235.degree. C. lower than the
melting point of the liquid crystal polymer of the insulation film
11 to a temperature that is 100.degree. C. lower than the same
melting point.
[0045] The above structure decreases the dimensional change rate of
the flexible laminated sheet 10, in particular, the dimensional
change rate between before and after the process of heating at
250.degree. C. If the flexible laminated sheet 10 is used as a
flexible printed board, the flexible laminated sheet 10 is exposed
to a high temperature of approximately 250.degree. C. when forming
a conductor circuit or reflow-soldering to mount various elements.
The reduction of dimensional changes in the flexible laminated
sheet 10 is important from the viewpoint of high-density mounting.
Thus, the flexible laminated sheet 10 in which the dimensional
change rate between before and after the heating process performed
at 250.degree. C. is effective for a material of a flexible printed
board used in high-density mounting.
[0046] The above embodiment may be modified as described below.
[0047] In the above embodiment, the metal foil 12 is
thermocompression-bonded onto each surface of the insulation film
11. However, the metal foil 12 may be thermocompression-bonded onto
only one surface of the insulation film to form a flexible
laminated sheet 10 in which a metal layer is provided on one
surface of an insulation layer.
[0048] In this case, for example, as shown in FIG. 2, the feeding
unit 30 may include a release film roll 33 on which an elongated
release film 13 is wound into a roll. The metal foil 12 fed from
the metal foil roll 32 may be placed on one surface of the
insulation film 11, which is fed from the insulation film roll 31
of the feeding unit 30. The release film 13 fed from the release
film roll 33 may be placed on the opposite surface of the
insulation film 11. The insulation film 11, the metal foil 12, and
the release film 13 may be continuously fed to the double belt
press device 20. The flexible laminated sheet 10 transferred out of
the double belt press device 20 is recovered and wound into a roll
by the winding unit 40 with the release film 13 on the flexible
laminated sheet 10. The heating and pressing conditions for
thermocompression-bonding the insulation film 11 to the metal foil
12 may be the same as the above embodiment.
[0049] The release film 13 limits the transfer of the softened
insulation film 11 to the double belt press device 20 during the
thermocompression bonding. A known release film used to manufacture
a flexible laminated sheet may be used as the release film 13. In
particular, a release film is preferably used that is formed of a
material excellent in heat resistance, releasability, and
flexiblitlue and, for example, at least one selected from
heat-resistant aromatic polyimide, fluorine resin, and silicone
resin that are not thermocompression bondable.
[0050] The release film 13 is removed when the flexible laminated
sheet 10 is used. A recovery roll that recovers the release film 13
may be arranged in the winding unit 40 to remove the release film
13 from the flexible laminated sheet 10 and separately recover the
flexible laminated sheet 10 and the release film 13 when
transferred out of the double belt press device 20.
[0051] Next, the above embodiment will be described below in detail
using examples and comparative examples.
Examples 101 to 113 and Comparative Examples 101 to 112
[0052] A double belt press device was used to manufacture flexible
laminated sheets in each of which a metal layer is provided on each
surface or one surface of an insulation layer. The quality of each
of the obtained flexible laminated sheets was evaluated. Tables 1
and 2 show heating conditions of thermocompression bonding steps in
examples 101 to 113 and comparative examples 101 to 112. That is,
in examples 101 to 113, the first temperature T1 is in the range of
"mp-45.degree. C.<T1<mp-5.degree. C." (290.degree.
C.<T1<330.degree. C.), and the second temperature T2 is in
the range of "mp-235.degree. C.<T2<mp-100.degree. C."
(100.degree. C.<T2<235.degree. C.). In comparative examples
101 to 112, one of the first temperature T1 and the second
temperature T2 falls outside the above ranges.
[0053] The conditions of the manufacturing other than the heating
conditions are as follows.
[0054] Metal foil: rolled copper foil (made by JX Nikko Nisseki
Co., Ltd., BHYX-92-HA).
[0055] Insulation film: LCP film (made by Kuraray Co., Ltd.,
Vecstar CTZ, melting point of 335.degree. C.)
[0056] Release film: polyimide film (Ube Industries, Ltd., Upilex
S, thickness of 25 .mu.m). The release film was separated from the
flexible laminated sheet after the thermocompression bonding
step.
[0057] Pressure: 4.0 MPa.
[0058] The thicknesses of the metal foil and the insulation film
that were used are shown in Tables 1 and 2.
[0059] Evaluation of Dimensional Change Rate
[0060] The dimensional change rate of each of the flexible
laminated sheets when heated at the temperatures of 150.degree. C.
and 250.degree. C. was measured in compliance with a dimensional
stability test defined in Japanese Industrial Standards (JIS) C
6471. The results are shown in Tables 1 and 2. In Tables 1 and 2,
MD stands for machine direction, that is, a longitudinal direction
when continuously manufacturing the flexible laminated sheet, and
TD stands for transverse direction, that is, the direction
perpendicular to the longitudinal direction when continuously
manufacturing the flexible laminated sheet.
[0061] Evaluation of Thickness Variation
[0062] A sample of 50 mm.times.520 mm width was collected from the
flexible laminated sheet of each of examples 101 to 113 and
comparative examples 101 to 112, and the metal layer was removed
from this sample through an etching process. The thickness of the
remaining insulation layer was measured with an intermittent
thickness meter at fifty-two points at 10 mm intervals in the
widthwise direction, and the standard deviation was calculated. The
results are shown in Tables 1 and 2.
[0063] Evaluation of Peel Strength
[0064] The peel strength of the metal layer of the flexible
laminated sheet of each of examples 101 to 113 and comparative
examples 101 to 112 was measured in compliance with a peel strength
test of copper foil defined in Japanese Industrial Standards (JIS)
C 6471. The results are shown in Tables 1 and 2.
TABLE-US-00001 TABLE 1 Example Example Example Example Example
Example Example 101 102 103 104 105 106 107 Materials Metal Foil
(.mu.m) 12 12 12 12 12 12 12 Insulation Film (.mu.m) 50 50 50 50 50
50 50 Metal Foil (.mu.m) 12 12 12 12 12 12 12 Heating First
Temperature T1 (.degree. C.) 290 290 300 300 310 310 320 Conditions
Melting Point Minus T1 (.degree. C.) 45 45 35 35 25 25 15 Second
Temperature T2 (.degree. C.) 100 235 100 235 100 235 100 Melting
Point Minus T2 (.degree. C.) 235 100 235 100 235 100 235
Evaluations Availability Yes Yes Yes Yes Yes Yes Yes of Continuous
Operation Dimensional 150.degree. C. MD (%) 0.00 -0.01 0.00 -0.01
0.00 -0.02 0.00 Change Ratio TD (%) 0.02 0.02 0.01 0.02 0.02 0.02
0.02 250.degree. C. MD (%) -0.02 -0.01 -0.02 0.00 -0.02 0.00 0.00
TD (%) 0.01 0.02 0.01 0.03 0.02 0.03 0.02 Thickness Variation
(.mu.m) 0.97 1.01 0.96 0.99 0.95 0.97 1.04 Peel Strength (N/mm) 0.6
0.7 0.7 0.7 0.7 0.7 0.8 Example Example Example Example Example
Example 108 109 110 111 112 113 Materials Metal Foil (.mu.m) 12 12
12 12 12 12 Insulation Film (.mu.m) 50 50 50 25 100 50 Metal Foil
(.mu.m) 12 12 12 12 12 -- Heating First Temperature T1 (.degree.
C.) 320 330 330 320 320 320 Conditions Melting Point Minus T1
(.degree. C.) 15 5 5 15 15 15 Second Temperature T2 (.degree. C.)
235 100 235 100 100 100 Melting Point Minus T2 (.degree. C.) 100
235 100 235 235 235 Evaluations Availability of Yes Yes Yes Yes Yes
Yes Continuous Operation Dimensional 150.degree. C. MD (%) -0.01
0.01 -0.01 0.00 0.01 0.00 Change Ratio TD (%) 0.02 0.02 0.02 0.03
0.04 0.01 250.degree. C. MD (%) 0.00 0.00 0.01 -0.01 0.00 -0.02 TD
(%) 0.03 0.02 0.04 0.04 0.02 0.02 Thickness Variation (.mu.m) 1.06
1.09 1.08 1.01 1.13 1.01 Peel Strength (N/mm) 0.8 0.9 1.0 0.8 0.7
0.8
TABLE-US-00002 TABLE 2 Comparative Comparative Comparative
Comparative Comparative Comparative Example 101 Example 102 Example
103 Example 104 Example 105 Example 106 Materials Metal Foil
(.mu.m) 12 12 12 12 12 12 Insulation Film (.mu.m) 50 50 50 50 50 50
Metal Foil (.mu.m) 12 12 12 12 12 12 Heating First Temperature T1
(.degree. C.) 290 290 300 300 310 310 Conditions Melting Point
Minus T1 (.degree. C.) 45 45 35 35 25 25 Second Temperature T2
(.degree. C.) 90 245 90 245 90 245 Melting Point Minus T2 (.degree.
C.) 245 90 245 90 245 90 Evaluations Availability of No Yes No Yes
No Yes Continuous Operation Dimensional 150.degree. C. MD (%) --
0.00 -- 0.00 -- 0.00 Change Ratio TD (%) -- 0.05 -- 0.05 -- 0.05
250.degree. C. MD (%) -- 0.02 -- 0.02 -- 0.03 TD (%) -- 0.06 --
0.06 -- 0.06 Thickness Variation (.mu.m) -- 0.97 -- 0.95 -- 1.03
Peel Strength (N/mm) -- 0.7 -- 0.7 -- 0.8 Comparative Comparative
Comparative Comparative Comparative Comparative Example 107 Example
108 Example 109 Example 110 Example 111 Example 112 Materials Metal
Foil (.mu.m) 12 12 12 12 12 12 Insulation Film (.mu.m) 50 50 50 50
50 50 Metal Foil (.mu.m) 12 12 12 12 12 12 Heating First
Temperature T1 (.degree. C.) 320 320 330 330 335 355 Conditions
Melting Point Minus T1 (.degree. C.) 15 15 5 5 0 -20 Second
Temperature T2 (.degree. C.) 90 245 90 245 100 100 Melting Point
Minus T2 (.degree. C.) 245 90 245 90 235 235 Evaluations
Availability of No Yes No Yes Yes Yes Continuous Operation
Dimensional 150.degree. C. MD (%) -- 0.00 -- 0.00 0.00 0.02 Change
Ratio TD (%) -- 0.07 -- 0.07 0.05 0.07 250.degree. C. MD (%) --
0.02 -- -0.03 -0.15 -0.21 TD (%) -- 0.08 -- 0.12 0.22 0.28
Thickness Variation (.mu.m) -- 1.1 -- 1.1 1.25 2.4 Peel Strength
(N/mm) -- 0.9 -- 1.0 1.0 1.1
[0065] First, as shown in the column indicated as availability of
continuous operation in Table 2, in each of comparative examples
101, 103, 105, 107, and 109, in which the second temperature T2 was
lower than "mp-235.degree. C." (100.degree. C.), a defect occurred
in the rotation of the double belt press device when a flexible
laminated sheet having a predetermined length was manufactured.
Thus, the double belt press device could not be continuously
operated. Accordingly, it was assumed that these flexible laminated
sheets had extremely low mass productivity. Therefore, the
dimensional change rate, the thickness variation, and the peel
strength were not evaluated. Such a problem did not occur in the
other examples and comparative examples in which the temperature T2
was greater than or equal to "mp-235.degree. C." (100.degree.
C.)
[0066] A comparison of the results between examples 102, 104, 106,
108, and 110 and comparative examples 102, 104, 106, 108, and 110
shows that the dimensional change rate in each of the tests of
150.degree. C. and 250.degree. C. was at least two times greater
when the second temperature T2 was "mp-100.degree. C." (235.degree.
C.) or greater.
[0067] A comparison of the results between example 101 and
comparative examples 111 and 112 shows that the dimensional change
rate in each of the tests of 150.degree. C. and 250.degree. C. was
at least two times greater when the first temperature T1 was
"mp-5.degree. C." (330.degree. C.) or greater.
[0068] As shown in Table 1, in each of examples 101 to 113, the
thickness variation was a small value of less than or equal to 1.2
.mu.m and the peel strength was a high value of 0.6 N/m or
greater.
[0069] These results confirm that when the first temperature T1 and
the second temperature T2 were in the above ranges, the dimensional
change rate between before and after heating at 250.degree. C. were
decreased while ensuring the quality such as thickness variation
and peel strength. These results also confirm that no problem
occurred in terms of mass productivity of the flexible laminated
sheets. Such advantageous effects were the same when the thickness
of the insulation film was changed (examples 111 and 112) and when
the flexible laminated sheet in which only one metal layer was
provided was used (example 113). Although the detail data is not
shown, similar results were obtained when using an electrolytic
copper foil having a thickness of 12 .mu.m (made by Mitsui Mining
& Smelting Co., Ltd., 3EC-VLP) as the metal foil and when using
other LCP films (made by Primatec Inc., BIAC-BC, melting point of
315.degree. C., thickness of 50 .mu.m) as the insulation film.
Second Embodiment
[0070] One embodiment of a laminated sheet manufacturing method of
the present invention will now be described in detail.
[0071] A method for manufacturing a laminated sheet of the present
embodiment includes a drying step of drying an insulation film and
a thermocompression bonding step of thermocompression-bonding a
metal foil onto the insulation film after the drying step. The
laminated sheet is manufactured through the drying step and the
thermocompression bonding step.
[0072] First, the insulation film and the metal foil used for
manufacturing the laminated sheet will be described.
[0073] The insulation film forms an insulation layer of the
laminated sheet. An insulation film formed of a polymer of
6-hydroxy-2-naphthoic acid and 4-hydroxybenzoic acid (hereinafter
referred to as type II liquid crystal polymer) is used as the
insulation film. The melting point of the type II liquid crystal
polymer is preferably in the range from 280.degree. C. to
360.degree. C. and more preferably in the range from 300.degree. C.
to 345.degree. C.
[0074] The thickness of the insulation film is not particularly
limited. However, the thickness of the insulation film 11 is
preferably in the range from 5 .mu.m to 200 .mu.m, more preferably
in the range from 12 .mu.m to 150 .mu.m, and further preferably in
the range from 25 .mu.m to 100 .mu.m.
[0075] The metal foil forms a metal layer of the laminated sheet. A
metal foil such as a copper foil, an aluminum foil, a stainless
steel foil, and a foil formed of an alloy of copper and aluminum
can be used as the metal foil. In particular, it is preferred that
at least one selected from a rolled copper foil, an electrolytic
copper foil, and an aluminum foil be used as the metal foil. The
thickness of the metal foil is not particularly limited. However,
the thickness of the metal foil is preferably in the range from 3
pm to 40 .mu.m, more preferably in the range from 3 .mu.m to 35
.mu.m, and further preferably in the range from 8 .mu.m to 35
.mu.m.
[0076] Next, the drying step of the manufacturing method of the
present embodiment will be described.
[0077] The drying step is a step of drying the insulation film to
remove moisture contained in the insulation film. In the drying
step, the insulation film is heated with a drying device by
exposing the insulation film to a particular temperature
environment for a particular time.
[0078] The temperature (drying temperature) of the drying step is
in the range from 120.degree. C. to 250.degree. C. and preferably
in the range from 150.degree. C. to 220.degree. C. When the drying
temperature is less than 120.degree. C., the moisture contained in
the insulation film may not be sufficiently removed. When the
drying temperature exceeds 250.degree. C., the liquid crystal
polymer of the insulation film may be softened.
[0079] The time (drying time) of the drying step is greater than or
equal to 20 seconds. When the drying time is less than 20 seconds,
the moisture contained in the insulation film may not be
sufficiently removed. Although the upper limit of the drying time
is not particularly limited, it is preferred that the drying time
be, for example, less than or equal to 600 seconds taking the
production efficiency into account.
[0080] The drying device used in the drying step is not
particularly limited as long as the above conditions are satisfied.
Examples of the drying device include an infrared heater, an air
heating furnace, an electric furnace, and a dielectric heating
roller.
[0081] The drying step may be continuously performed for the
insulation film that is continuously fed from, for example, a film
roll or performed in batches every predetermined unit.
[0082] Next, the thermocompression bonding step of the
manufacturing method of the present embodiment will be
described.
[0083] The thermocompression bonding step is a step of forming the
laminated sheet by thermocompression-bonding the metal foil onto
the dried insulation film after the drying step. In the
thermocompression bonding step, a heating and pressing device is
used to heat the insulation film and the metal foil and apply a
predetermined pressure to the insulation film and the metal foil in
a state in which the metal foil is placed on one surface or each
surface of the insulation film.
[0084] The insulation film under a high temperature immediately
after the drying step may be used as is for the thermocompression
bonding step. Alternatively, the insulation film after the drying
step may be used for the thermocompression bonding step after the
temperature of the insulation film is decreased to a predetermined
temperature (for example, room temperature). However, when the
insulation film whose temperature has been decreased is used, it is
preferred that the insulation film after the drying step be cooled
and stored in a dehumidified environment so that the moisture is
not absorbed.
[0085] In the thermocompression bonding step, the insulation film
and the metal foil are heated to a temperature in the range from
250.degree. C. to 330.degree. C. and preferably in the range from
300.degree. C. to 320.degree. C. When the heating temperature is
less than 250.degree. C., the insulation film and the metal foil
may not be sufficiently bonded. When the heating temperature
exceeds 330.degree. C., the crystal structure of the liquid crystal
polymer of the insulation film may be broken, which causes a
decrease in the viscoelasticity of the insulation film.
[0086] In the thermocompression bonding step, the pressure applied
to the insulation film and the metal foil is in the range from 0.5
MPa to 10 MPa and preferably in the range from 2 MPa to 6 MPa. When
the pressure is less than 0.5 MPa, the insulation film and the
metal foil may not be sufficiently bonded. The pressure exceeding
10 MPa is excessive for bonding the insulation film and the metal
foil, which decreases the productivity.
[0087] The heating and pressing time in the thermocompression
bonding step is in the range from 10 seconds to 600 seconds and
preferably in the range from 30 seconds to 500 seconds. When the
heating and pressing time is less than 10 seconds, the insulation
film and the metal foil may not be sufficiently bonded. The heating
and pressing time exceeding 600 seconds is excessive for bonding
the insulation film and the metal foil, which decreases the
productivity.
[0088] The heating and pressing device used for the
thermocompression bonding step is not particularly limited as long
as the above conditions are satisfied. Examples of the heating and
pressing device include a heat press, a vacuum batch press, a
multi-stage press, and a heating roll press, each of which has a
flat heating and pressing unit. Examples of the heating and
pressing device also include a double belt press device that
performs heating and pressing between belts.
[0089] The thermocompression bonding step may be continuously
performed for the insulation film and the metal foil that are
continuously fed from, for example, film rolls or performed in
batches every predetermined unit.
[0090] The laminated sheet manufactured through the manufacturing
method of the present embodiment is used as a material for
manufacturing a multilayer circuit board. That is, a pattern film
is formed by forming a circuit on the metal layer portion of the
laminated sheet. A via hole is formed in the insulation layer
portion of the pattern film and filled with an interlayer
connection material. A plurality of pattern films thus formed from
the laminated sheet are laminated together and integrally bonded
through a heating press into a multilayer. As a result, a
multilayer circuit board is obtained.
[0091] A known manufacturing method (for example, manufacturing
method disclosed in patent document 2) can be used for
manufacturing the multilayer circuit board. However, it is
preferred that the heating temperature of the heating press be in
the range from 250.degree. C. to 330.degree. C. Further, it is
preferred that the pressure of the heating press be in the range
from 1 MPa to 10 MPa.
[0092] The laminated sheet manufactured through the manufacturing
method of the present embodiment has a small dynamic thermal
deformation amount at the insulation layer portion formed of the
insulation film. For example, the maximum deformation rate is less
than or equal to 0.85% at 250.degree. C. to 300.degree. C. when
measured with a dynamic viscoelasticity measurement device under
the conditions in which the dynamic load is 15 g, the frequency is
1 Hz, and the rate of temperature increase is 5.degree. C./min
while controlling the dynamic stress and the static load in a
dynamic stress mode and an automatic static load mode.
[0093] In the manufacturing method of the present embodiment, the
thermocompression bonding step is performed with the dried
insulation film after the drying step. Thus, the manufactured
laminated sheet has a small amount of moisture contained in the
type II liquid crystal polymer of the insulation layer. As a
result, it is assumed that a laminated sheet having a small dynamic
thermal deformation amount is obtained.
[0094] More specifically, the type II liquid crystal polymer has
ester linkage. Thus, the type II liquid crystal polymer undergoes
hydrolysis when heated with water. A low-molecular-weight type II
liquid crystal polymer generated through the hydrolysis has a
tendency to flow. Thus, the generation of the low-molecular-weight
type II liquid crystal polymer increases the dynamic thermal
deformation amount at the insulation layer portion. The laminated
sheet manufactured through the manufacturing method of the present
embodiment has a small amount of moisture contained in the type II
liquid crystal polymer of the insulation layer. This limits
hydrolysis of the type II liquid crystal polymer when heated and
limits decreases in molecular weight caused by the hydrolysis. As a
result, it is assumed that a laminated sheet having a small dynamic
thermal deformation amount at the insulation layer portion is
obtained.
[0095] The laminated sheet manufactured through the manufacturing
method of the present embodiment has a small dynamic thermal
deformation amount at the insulation layer portion. This limits
occurrence of large flow caused by the softening of the type II
liquid crystal polymer of the insulation layer during heating press
for manufacturing the multilayer circuit board. The flow of the
type II liquid crystal polymer into the via hole is thus decreased.
As a result, conduction failure between the layers of the
multilayer circuit board is reduced.
[0096] The advantages of the present embodiment will now be
described.
[0097] The laminated sheet formed by laminating an insulation film
of a type II liquid crystal polymer and a metal foil together and
used to manufacture a multilayer circuit board is manufactured
through a drying step of drying the insulation film by heating the
insulation film at a temperature of 120.degree. C. to 250.degree.
C. for 20 seconds or longer and a thermocompression bonding step of
thermocompression-bonding the dried insulation film onto the metal
foil by pressing the dried insulation film and the metal foil
against each other with a pressure of 0.5 MPa to 10 MPa for 10
seconds to 600 seconds while heating the dried insulation film and
the metal foil at a temperature of 250.degree. C. to 330.degree.
C.
[0098] The above structure allows for the manufacturing of a
laminated sheet having a small dynamic thermal deformation amount
in which the maximum deformation rate is less than or equal to
0.85% at 250.degree. C. to 300.degree. C. when measured with a
dynamic viscoelasticity measurement device under the conditions in
which the dynamic load is 15 g, the frequency is 1 Hz, and the rate
of temperature increase is 5.degree. C./min while controlling the
dynamic stress and the static load in a dynamic stress mode and an
automatic static load mode.
[0099] Next, the above embodiment will be described below in detail
using examples and comparative examples. Examples 201 to 205 and
Comparative Examples 201 to 206
[0100] Laminated sheets were manufactured under different
conditions of the drying step and the thermocompression bonding
step. That is, when forming each laminated sheet, first, an
insulation film fed from a film roll was continuously fed to a
drying device, and the insulation film was dried by passing for a
predetermined time through the drying device heated to a
predetermined temperature (drying step). Then, metal foils fed from
a pair of metal foil rolls were placed on both surfaces of the
insulation film that had been passed through the drying device to
be in a dried state, the metal foils were continuously fed to a
double belt press device, and the double belt press device
performed thermocompression bonding for the metal foils and the
insulation film to obtain a laminated sheet (thermocompression
bonding step).
[0101] Tables 3 and 4 show the conditions of the drying step
(drying temperature and drying time) and the conditions of the
thermocompression bonding step (heating temperature, pressure, and
heating and pressing time) in examples 201 to 205 and comparative
examples 201 to 206. The other manufacturing conditions are as
follows.
[0102] Insulation film: type II liquid crystal polymer film (made
by Kuraray Co., Ltd., Vecstar CTZ, melting point of 335.degree.
C.)
[0103] Metal foil: copper foil (made by Furukawa Electric Co.,
Ltd., F2-WS) or stainless steel foil (made by Toyo Seihaku Co.,
Ltd., SUS304H-TA)
Example 206
[0104] An insulation film cut out to a predetermined size was put
into a drying device, and the insulation film was dried by applying
to the insulation film a hot air having a predetermined temperature
(drying step). Subsequently, a metal foil was placed on each
surface of the dried insulation film, and the insulation film and
the metal foils were thermocompression-bonded together by a heat
press (thermocompression bonding step).
[0105] Evaluation of Dynamic Thermal Deformation Amount
[0106] The metal layers of both surfaces of the laminated sheet
obtained in each of examples 201 to 206 and comparative examples
201 to 206 were removed through an etching process with a ferric
chloride solution. A sample of 10 mm length x 5 mm width was cut
out from the remaining insulation film (insulation layer) and set
to a dynamic viscoelasticity measurement device (made by UBM,
Rheogel-E4000). The dynamic viscoelasticity measurement device set
the dynamic load to 15 g and the frequency to 1 Hz in a dynamic
stress control mode as a dynamic stress control method and in an
automatic static load mode as a static load control method. The
dynamic deformation amount of each sample was measured while
increasing the temperature at a rate of 5.degree. C./min. The
column indicated as "dynamic thermal deformation amount" in Tables
3 and 4 shows the maximum value of the dynamic deformation amount
in the longitudinal direction of each sample at 250.degree. C. to
300.degree. C. The column indicated as "maximum deformation rate"
in Tables 3 and 4 shows, expressed as a percentage, a value
obtained by dividing the maximum value of the dynamic deformation
amount by the original length of the same sample (10 mm).
[0107] Evaluation of Adhesiveness
[0108] In compliance with a peel strength test of copper foil
defined in Japanese Industrial Standards (JIS) C 6471, the peel
strength of the metal layer of the flexible laminated sheet
obtained in each of examples 201 to 206 and comparative examples
201 to 206 was measured, and the adhesiveness of the laminated
sheet was evaluated based on the measurement values. The results
are shown in Tables 3 and 4. The evaluation of adhesiveness was
conducted on the basis that the peel strength that is greater than
or equal to 0.3 N/m is "good" and the peel strength that is less
than 0.3 N/m is "not acceptable."
[0109] Manufacturing of Multilayer Circuit Board
[0110] Pattern films were manufactured by preparing sets of
laminated sheets that were the same as the laminated sheets of
examples 201 to 206 and comparative examples 201 to 203 as
described above, forming a circuit on one of two metal layers of
each laminated sheet, and removing the other metal layer through an
etching process. Via holes were formed in some of the pattern films
formed from the same laminated sheets, and the via holes were
filled with interlayer connection materials. A multilayer circuit
board was obtained by laminating eight pattern films with via holes
and one pattern film without a via hole among the pattern films
formed from the same laminated sheets and by pressing the pattern
films at 4 MP with a vacuum heating press while heating the pattern
films to 280.degree. C.
[0111] Evaluation of Conductivity
[0112] A liquid phase heat impact test (-40.degree. C. to
125.degree. C., 300 cycles) was conducted on the obtained
multilayer circuit board, and circuit resistance values of the
multilayer circuit board before and after the test were measured
with a resistance measurement device. The change rate of the
circuit resistance value before the liquid phase heat impact test
to the circuit resistance value after the liquid phase heat impact
test was calculated, and conductivity of the multilayer circuit
board was evaluated based on the change rate. The evaluation of
conductivity was conducted on the basis that the change rate of a
resistance value that is less than 20% is "good" and the change
rate of a resistance value that is greater than or equal to 20% is
"not acceptable." Evaluation of conductivity is not shown in
comparative examples 204 to 206 in which the evaluation of
adhesiveness was not acceptable.
TABLE-US-00003 TABLE 3 Example Example Example Example Example
Example 201 202 203 204 205 206 Manufacturing Thickness of
Insulation Film (.mu.m) 50 50 25 100 50 50 Conditions Type of Metal
Foil Copper Foil Copper Foil Copper Foil Copper Foil SUS Foil
Copper Foil Thickness of Metal Foil (.mu.m) 12 12 12 12 20 12
Drying Temperature (.degree. C.) 200 200 200 200 200 200 Drying
Time (Sec) 60 60 60 60 60 60 Heating Temperature (.degree. C.) 310
330 310 310 310 310 Pressure (MPa) 4 4 4 4 4 2.5 Heating and
Pressing Time (Sec) 210 210 210 210 210 210 Evaluations Dynamic
Thermal Deformation 70 80 70 70 70 74 Amount (.mu.m) Maximum
Deformation Ratio (%) 0.70 0.80 0.70 0.70 0.70 0.74 Adhesiveness
Good Good Good Good Good Good Conductivity Good Good Good Good Good
Good
TABLE-US-00004 TABLE 4 Comparative Comparative Comparative
Comparative Comparative Comparative Example 201 Example 202 Example
203 Example 204 Example 205 Example 206 Manufacturing Thickness of
Insulalton Film (.mu.m) 50 50 50 50 50 50 Conditions Type of Metal
Foil Copper Foil Copper Foil Copper Foil Copper Foil Copper Foil
Copper Foil Thickness of Metal Foil (.mu.m) 12 12 12 12 12 12
Drying Temperature (.degree. C.) 100 200 200 200 200 200 Drying
Time (Sec) 60 10 60 60 60 60 Heating Temperature (.degree. C.) 310
310 340 240 310 310 Pressure (MPa) 4 4 4 4 0.4 4 Heating and
Pressing Time (Sec) 210 210 210 210 210 5 Evaluations Dynamic
Thermal 88 87 >90 70 70 70 Deformation Amount (.mu.m) Maximum
Deformation Ratio (%) 0.88 0.87 >0.90 0.70 0.70 0.70
Adhesiveness Good Good Good Not Acceptable Not Acceptable Not
Acceptable Conductivity Not Not Acceptable Not Acceptable -- -- --
Acceptable
[0113] As shown in Tables 3 and 4, the evaluation of conductivity
was "good" in examples 201 to 206 in which the dynamic heat
deformation amount was less than or equal to 85 .mu.m (maximum
deformation rate was less than or equal to 0.85%), and the
evaluation of conductivity was "not acceptable" in comparative
examples 201 to 203 in which the dynamic heat deformation amount
exceeded 85 .mu.m (maximum deformation rate exceeded 0.85%). This
result confirms that decreases in the dynamic thermal deformation
amount (maximum deformation rate) limited conduction failure of the
multilayer circuit board.
[0114] The result of comparative example 201 confirms that when the
drying temperature in the drying step was lower than the range from
120.degree. C. to 250.degree. C., the dynamic thermal deformation
amount and the maximum deformation rate were large. The result of
comparative example 202 confirms that when the drying time in the
drying step was shorter than 20 seconds, the dynamic thermal
deformation amount and the maximum deformation rate were large. The
result of comparative example 3 confirms that when the heating
temperature in the thermocompression bonding step was higher than
the range from 250.degree. C. to 330.degree. C., the dynamic
thermal deformation amount and the maximum deformation rate were
large. These results confirm that the drying temperature and the
drying time in the drying step and the heating temperature in the
thermocompression bonding step are important to adjust the dynamic
thermal deformation amount and the maximum deformation rate.
[0115] Further, the results of comparative examples 204 to 206
confirm that sufficient adhesiveness was not obtained when the
heating temperature in the thermocompression bonding step was lower
than the range from 250.degree. C. to 330.degree. C., when the
pressure in the thermocompression bonding step was smaller than the
range from 0.5 MPa to 10 MPa, and when the heating and pressing
time in the thermocompression bonding step was shorter than the
range from 10 seconds to 600 seconds. These results confirm that
the heating temperature, the pressure, and the heating and pressing
time in the thermocompression bonding step are important to ensure
sufficient adhesiveness of the laminated sheet.
[0116] The embodiments and the modified embodiments may be combined
or replaced. Further, the illustrated features may be combined.
[0117] The present invention is not limited to the illustrated
features. For example, all the features of the disclosed particular
embodiments should not be interpreted as essential for the present
invention, and the subject matter of the present invention may
exist in fewer features than all the features of the disclosed
particular embodiments.
DESCRIPTION OF REFERENCE CHARACTERS
[0118] 10 . . . flexible laminated sheet, 11 . . . insulation film,
12 . . . metal foil, 13 . . . release film, 20 . . . double belt
press device, 21 . . . upper drum, 22 . . . lower drum, 23 and 24 .
. . endless belts, 25 . . . thermocompression device, 30 . . .
feeding unit, 31 . . . insulation film roll, 32 . . . metal foil
roll, 33 . . . release film roll, 40 . . . winding unit.
* * * * *