U.S. patent application number 15/137343 was filed with the patent office on 2016-08-18 for production method for thermoplastic liquid crystal polymer film, circuit board and production method therefor.
This patent application is currently assigned to Kuraray Co., Ltd.. The applicant listed for this patent is Kuraray Co., Ltd.. Invention is credited to Takahiro NAKASHIMA, Minoru Onodera, Tatsuya Sunamoto.
Application Number | 20160236402 15/137343 |
Document ID | / |
Family ID | 53004045 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160236402 |
Kind Code |
A1 |
NAKASHIMA; Takahiro ; et
al. |
August 18, 2016 |
PRODUCTION METHOD FOR THERMOPLASTIC LIQUID CRYSTAL POLYMER FILM,
CIRCUIT BOARD AND PRODUCTION METHOD THEREFOR
Abstract
Provided are a method for producing a thermoplastic liquid
crystal polymer (TLCP) film having an improved thermo-adhesive
property, a circuit board, and a method for producing the same. The
production method of the TLCP film includes preparing a TLCP film
as the adherend film and a TLCP film as the adhesive film;
examining each of the prepared TLCP films for a relative intensity
calculated as a ratio in percentage of a sum of peak areas of C--O
bond peak and COO bond peak based on the total area of C1s peaks in
the XPS spectral profile so as to calculate a relative intensity X
(%) as for the prepared adherend film and a relative intensity Y
(%) as for the prepared adhesive film; and controlling the TLCP
film as the adhesive film to have a relative intensity Y by
selection or activation treatment of the adhesive film so that the
relative intensity X of the adherend film and the relative
intensity Y of the controlled adhesive film satisfy the following
formulae (1) and (2): 38<X+Y<65 (1) -8.0<Y-X<8.0
(2).
Inventors: |
NAKASHIMA; Takahiro;
(Saijo-shi, JP) ; Onodera; Minoru; (Saijo-shi,
JP) ; Sunamoto; Tatsuya; (Chiyoda-ku, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kuraray Co., Ltd. |
Kurashiki-shi |
|
JP |
|
|
Assignee: |
Kuraray Co., Ltd.
Kurashiki-shi
JP
|
Family ID: |
53004045 |
Appl. No.: |
15/137343 |
Filed: |
April 25, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2014/078063 |
Oct 22, 2014 |
|
|
|
15137343 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09J 2301/312 20200801;
B29C 66/73115 20130101; C09J 2203/326 20130101; B32B 2307/206
20130101; B29K 2105/0079 20130101; B32B 7/02 20130101; B29C
66/73111 20130101; H05K 1/032 20130101; B29C 65/5057 20130101; B29L
2031/3425 20130101; B29C 66/1122 20130101; B29C 66/0242 20130101;
B29C 66/45 20130101; C08J 2300/12 20130101; H05K 3/4644 20130101;
H05K 2201/0141 20130101; B32B 7/12 20130101; C09J 2467/006
20130101; B29C 66/73921 20130101; B29C 66/028 20130101; C08J 5/121
20130101; C08J 2367/00 20130101; B32B 27/08 20130101; B32B 2457/202
20130101; C09J 5/06 20130101; B29C 65/02 20130101; C09J 2467/00
20130101; C08J 2467/00 20130101; B29C 65/4815 20130101; B29C 66/73
20130101 |
International
Class: |
B29C 65/02 20060101
B29C065/02; H05K 1/03 20060101 H05K001/03; H05K 3/46 20060101
H05K003/46; B29C 65/00 20060101 B29C065/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 1, 2013 |
JP |
2013-228087 |
Claims
1. A method for producing a thermoplastic liquid crystal polymer
film as an adhesive film to be thermo-bonded to an adherend body of
a thermoplastic liquid crystal polymer film (hereinafter referred
to as an adherend film), the method at least comprising: preparing
a thermoplastic liquid crystal polymer film as the adherend film
and a thermoplastic liquid crystal polymer film as the adhesive
film; examining each of the prepared thermoplastic liquid crystal
polymer films for a relative intensity calculated as a ratio in
percentage of a sum of peak areas of C--O bond peak and COO bond
peak based on the total area of C1s peaks in the XPS spectral
profile so as to calculate a relative intensity X (%) as for the
prepared adherend film and a relative intensity Y (%) as for the
prepared adhesive film; and controlling the thermoplastic liquid
crystal polymer film as the adhesive film to have a relative
intensity Y by selection or activation treatment of the adhesive
film so that the relative intensity X of the adherend film and the
relative intensity Y of the controlled adhesive film satisfy the
following formulae (1) and (2): 38<X+Y<65 (1)
-8.0<Y-X<8.0 (2).
2. The method for producing a film according to claim 1, wherein
the controlling is performed by at least one activation treatment
selected from the group consisting of ultraviolet (UV) ray
irradiation, plasma irradiation, and corona discharge
treatment.
3. The method for producing a film according to claim 1, wherein
the thermoplastic liquid crystal polymer film as the adhesive film
is further subjected to degassing of the film before or after the
controlling process of the relative intensity Y (%) by degassing
the film (i) under vacuum of 1500 Pa or lower for 30 minutes or
more, by degassing the film (ii) under heating at a temperature
ranging from 100.degree. C. to 200.degree. C., or by degassing the
film under the vacuum (i) and under the heating (ii) simultaneously
or separately.
4. The method for producing a film according to claim 3, wherein
the degassing process is carried out by degassing the film under
vacuum of 1500 Pa or lower while heating at a temperature ranging
from 50.degree. C. to 200.degree. C.
5. The method for producing a film according to claim 1, wherein
the thermoplastic liquid crystal polymer film as the adhesive film
has a film thickness of 10 to 500 gm.
6. A method for producing a circuit board comprising a
thermoplastic liquid crystal polymer film as an adherend film and a
thermoplastic liquid crystal polymer film as an adhesive film, the
both films being laminated by thermo- bonding, the method
comprising: preparing the adherend film and the adhesive film as
circuit board materials; stacking the adherend film and the
adhesive film in accordance with a predetermined structure of a
circuit board to obtain a stacked material, followed by conducting
thermo-compression bonding of the stacked material by heating under
a predetermined compression pressure; wherein the prepared circuit
board materials are independently at least one member selected from
the group consisting of an insulating substrate having a conductor
layer on at least one surface, a bonding sheet, and a coverlay; and
the adhesive film is a thermoplastic liquid crystal polymer film
produced by a method recited in claim 1.
7. The method for producing a circuit board according to claim 6,
wherein the adherend film is an insulating substrate having a
conductor circuit on at least one surface, and the adhesive film is
at least one circuit board material selected from the group
consisting of an insulating substrate having a conductor layer on
at least one surface, a bonding sheet, and a coverlay.
8. The method for producing a circuit board according to claim 6,
wherein the method further comprises degassing the adherend film
and the adhesive film before thermo-compression bonding by
degassing the film (i) under vacuum of 1500 Pa or lower for 30
minutes or more, by degassing the film (ii) under heating at a
temperature ranging from 100.degree. C. to 200.degree. C., or by
degassing the film under the vacuum (i) and under the heating (ii)
simultaneously or separately.
9. The method for producing a circuit board according to claim 8,
wherein the degassing is carried out under vacuum at a vacuum
degree of 1500 Pa or lower for 30 minutes or more at a temperature
ranging from 50 to 150.degree. C.
10. A circuit board comprising a thermoplastic liquid crystal
polymer film as an adherend film and a thermoplastic liquid crystal
polymer film as an adhesive film, the both films being laminated by
thermo-bonding, wherein the adherend film has a surface portion to
be adhered, the surface portion having a relative intensity X (%)
calculated as a ratio in percentage of a sum of peak areas of C--O
bond peak and COO bond peak relative to the total area of C1s peaks
in the XPS spectral profile; the adhesive film has a surface
portion to be adhered, the surface portion having a relative
intensity Y (%) calculated as a ratio in percentage of a sum of
peak areas of C--O bond peak and COO bond peak relative to the
total area of C1s peaks in the XPS spectral profile; the relative
intensities X and Y satisfy the following formulae (1) and (2):
38<X+Y<65 (1) -8.0<Y-X<8.0 (2); and wherein the circuit
board shows a solder heat resistance when the circuit board is
placed in a solder bath at a temperature of 290.degree. C. for 60
seconds conforming to a method of JIS C 5012.
11. The circuit board according to claim 10, wherein a bonding
strength between the adherend film and the adhesive film in
accordance with JIS 05016- 1994 is 0.7 kN/m or higher.
12. The circuit board according to claim 10, wherein where there is
a conductive material portion between the adherend and adhesive
films, the surface area ratio of the conductive material portion
existing between the adherend and adhesive films is less than
30%.
13. The circuit board according to claim 10, wherein difference in
melting point between the adhesive film and the adherend film is
0.degree. C. to 60.degree. C.
Description
CROSS REFERENCE TO THE RELATED APPLICATION
[0001] This application is a continuation application, under 35
U.S.C..sctn.111(a), of international application No.
PCT/JP2014/078063, filed Oct. 22, 2014, which claims priority to
Japanese patent application No. 2013-228087 filed Nov. 1, 2013, the
entire disclosure of which is herein incorporated by reference as a
part of this application.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for producing a
film of a thermoplastic liquid crystal polymer capable of forming
an optically anisotropic melt phase (hereinafter may be referred to
as a thermoplastic liquid crystal polymer film, or TLCP film, or
simply abbreviated as a liquid crystal polymer film, or LCP film)
having an improved thermo-adhesive property, and to a circuit board
and a method for producing the same.
BACKGROUND ART
[0003] In recent years, there have been remarkable developments in
the field of information processing, such as personal computers, as
well as in the field communication equipment, such as mobile
phones. Such electronics and communication equipment have come to
be operated at higher frequencies of gigahertz region. In the high
frequency band, however, it is known that the electronics and
communication equipment generally have increased in transmission
loss.
[0004] Circuit boards have been conventionally known as one
comprising a wiring substrate in which a conductor circuit is
formed on a polyimide film, and a coverlay film bonded on the
wiring substrate, the coverlay film comprising a polyimide film and
an adhesive layer.
[0005] However, such a circuit board sometimes has poor heat
resistance, especially poor solder heat resistance, due to adhesive
usage. Further, some circuit boards contain residual solvent
originated from the adhesive. The presence of the solvent in the
circuit boards may cause defects in the circuit boards after
multi-layering process, resulting in deterioration of reliability
of the circuit boards. Accordingly, a technique for forming a
circuit board without using an adhesive has been desired.
[0006] On the other hand, TLCP films have attracted attention as
substrate materials for forming circuit boards without using an
adhesive. The TLCP film, however, contains rigid skin layers on the
surfaces, the skin layers generated during extrusion. Where the
TLCP films are heat-bonded with each other, the skin layers
sometimes interrupt sufficient interlayer adhesion between the TLCP
films.
[0007] In order to improve adhesive property, for example, Patent
Document 1 (JP Laid-open Patent Publication No. 2010-103269)
discloses a method for producing a multilayer circuit board
including: extruding a thermoplastic liquid crystal polymer capable
of forming an optically anisotropic melt phase to form a TLCP film,
softening at least one surface of the TLCP film by physical
grinding or UV irradiation to render the film surface to have a
hardness of 0.01 to 0.1 GPa measured in accordance with the
nanoindentation method so as to form an adhesive surface, and
counterposing the adhesive surface on a circuit surface of a wiring
substrate comprising a conductive circuit on at least one surface
of a TLCP film capable of forming an optically anisotropic melt
phase and carrying out a thermo-compression bonding of the entire
components.
[0008] In the meanwhile, Patent Document 2 (JP Laid-open Patent
Publication No. 2007-302740) discloses a highly adhesive LCP shaped
body characterized in that, the LCP shaped body has a surface to be
adhered, the surface having the following values with respect to
X-ray photoelectron spectroscopy analysis: where calculating each
of the relative peak areas of C--O and COO bond peaks based on the
total area of C1s peaks of each functional group in the XPS
spectral profile, a sum of relative peak areas of C--O and COO bond
peaks is 21% or more, and a peak area ratio of C--O bond peak/ COO
bond peak is 1.5 or less.
[0009] This document describes as follows: where a sum of relative
peak areas of C--O and COO bond peaks is 21% or more, destruction
of liquid crystal polymer molecules appropriately proceeds on the
surface to be adhered in the liquid crystal polymer shaped body,
resulting in improvement in initial adhesive property of the film
because of enhanced reactivity of the surface; where the peak area
ratio of C--O/COO is 1.5 or less, the adhesive property can be kept
for a long time so as to enhance long-term reliability.
SUMMARY OF THE INVENTION
[0010] Patent Document 1 achieves the enhanced interlayer adhesion
between liquid crystal polymer films by carrying out the softening
treatment of the skin layers by physical grinding or UV
irradiation. Patent Document 1, however, fails to disclose or
suggest improvement in interlayer adhesion between liquid crystal
polymer films without causing damage to the skin layer.
[0011] Patent Document 2 essentially requires for LCP films, which
generally have difficulty in thermo-adhesion, to have the specific
state that a sum of relative peak areas of C--O and COO bond peaks
based on the total area of C1s peaks is 21% or more, and a peak
area ratio of C--O bond peak/ COO bond peak is 1.5 or less in view
of breakage of LCP molecules on the film surface. In the Patent
Document 2, films that do not satisfy the above state cannot
improve adhesive property.
[0012] An object of the present invention is to provide a method
for producing a liquid crystal polymer film making it possible to
improve interlayer adhesion between the films by controlling the
film to have a specific relationship with an adherend body.
[0013] Another object of the present invention is to provide a
circuit board having an improved interlayer adhesion and a method
producing the same.
[0014] Based on the result of intensive studies to achieve the
above objects, the inventors of the present invention have found
the following aspects of the present invention.
[0015] That is, a first aspect of the present invention relates to
a method for producing a TLCP film as an adhesive film to be
thermo-bonded to an adherend body of a TLCP film (hereinafter
referred to as an adherend film), the method at least
including:
[0016] preparing a TLCP film as the adherend film and a TLCP film
as the adhesive film;
[0017] examining each of the prepared TLCP films for a relative
intensity calculated as a ratio in percentage of a sum of peak
areas of C--O bond peak and COO bond peak based on the total area
of C1s peaks in the XPS spectral profile so as to calculate a
relative intensity X (%) as for the prepared adherend film and a
relative intensity Y (%) as for the prepared adhesive film; and
[0018] controlling the TLCP film as the adhesive film to have a
relative intensity Y by selection or activation treatment of the
adhesive film so that the relative intensity X of the adherend film
and the relative intensity Y of the controlled adhesive film
satisfy the following formulae (1) and (2):
38<X+Y<65 (1)
-8.0<Y-X<8.0 (2).
[0019] In the above method, the controlling process may be
performed by at least one activation treatment selected from the
group consisting of ultraviolet (UV) ray irradiation, plasma
irradiation, and corona discharge treatment.
[0020] The above method may further include degassing process. In
the degassing process, the TLCP film(s) may be further subjected to
degassing of the film before or after the controlling process of
the relative intensity Y (%) by degassing the film (i) under vacuum
of 1500 Pa or lower for 30 minutes or more, and/or
[0021] by degassing the film (ii) under heating at a temperature
ranging from 100.degree. C. to 200.degree. C.
[0022] The degassing process may be carried out, for example, by
degassing the film under vacuum of 1500 Pa or lower while heating
at a temperature ranging from 50.degree. C. to 200.degree. C.
[0023] The TLCP film as the adhesive film may have a film thickness
of, for example, 10 to 500 .mu.m.
[0024] A second aspect of the present invention relates to a method
for producing a circuit board comprising a TLCP film as an adherend
film and a TLCP film as an adhesive film, the both films being
laminated by thermo-bonding, the method including:
[0025] preparing the adherend film and the adhesive film as circuit
board materials;
[0026] stacking the adherend film and the adhesive film in
accordance with a predetermined structure of a circuit board to
obtain a stacked material, followed by conducting
thermo-compression bonding of the stacked material by heating under
a predetermined compression pressure; wherein
[0027] the prepared circuit board materials are independently at
least one member selected from the group consisting of an
insulating substrate having a conductor layer on at least one
surface, a bonding sheet, and a coverlay; and
[0028] the adhesive film is a TLCP film produced by the
above-mentioned film production method.
[0029] In the method for producing a circuit board, wherein the
adherend film may be an insulating substrate having a conductor
circuit on at least one surface; and the adhesive film may be at
least one circuit board material selected from the group consisting
of an insulating substrate having a conductor layer on at least one
surface, a bonding sheet, and a coverlay.
[0030] The method further may comprise degassing, as described
above, the adherend film and the adhesive film before
thermo-compression bonding. For example, the degassing may be
carried out under vacuum at a vacuum degree of 1500 Pa or lower for
30 minutes or more at a temperature ranging from 50 to 150.degree.
C.
[0031] In the circuit board production method, among the circuit
board materials selected from the group consisting of an insulating
substrate, a bonding sheet, and a coverlay, at least two circuit
board materials may comprise a first LCP film (e.g., a
high-melting-point film having higher heat resistance) and a second
LCP film (e.g., a low-melting-point film having lower heat
resistance than the first LCP film). The difference in melting
point between the first and second LCP films may be within
60.degree. C.
[0032] A third aspect of the present invention relates to a circuit
board comprising a TLCP film as an adherend film and a TLCP film as
an adhesive film, the both films being laminated by thermo-bonding,
wherein
[0033] the adherend film has a surface portion to be adhered, the
surface portion having a relative intensity X (%) calculated as a
ratio in percentage of a sum of peak areas of C--O bond peak and
COO bond peak based on the total area of C1s peaks in the XPS
spectral profile;
[0034] the adhesive film has a surface portion to be adhered, the
surface portion having a relative intensity Y (%) calculated as a
ratio in percentage of a sum of peak areas of C--O bond peak and
COO bond peak based on the total area of C1s peaks in the XPS
spectral profile;
[0035] the relative intensities X and Y satisfy the following
formulae (1) and (2):
38 <X+Y<65 (1)
-8.0<Y-X<8.0 (2); and wherein
[0036] the circuit board shows a solder heat resistance when the
circuit board is placed in a solder bath at a temperature of
290.degree. C. for 60 seconds conforming to a method of JIS C
5012.
[0037] For example, the circuit board may be a circuit board
produced by the above production method. For example, in the
circuit board, a bonding strength between the adherend film and the
adhesive film in accordance with JIS 05016-1994 is 0.7 kN/m or
higher.
[0038] Further, where there is a conductive material portion
between the adherend and adhesive films, the surface area ratio of
the conductive material portion existing between the adherend and
adhesive films may be less than 30%.
[0039] The difference in melting point between the adhesive film
and the adherend film may be within 60.degree. C.
[0040] It should be noted that any combination of at least two
constructions, disclosed in the appended claims and/or the
specification should be construed as included within the scope of
the present invention. In particular, any combination of two or
more of the appended claims should be equally construed as included
within the scope of the present invention.
[0041] According to the first aspect relating to a production
process of a TLCP film, by performing a specific controlling
process for a TLCP film, the TLCP film enables to have a specific
relative intensity as a sum of relative peak areas of C--O and COO
bond peaks in XPS analysis with respect to a relative intensity of
an adherend TLCP film. As a result, a TLCP film can be produced to
achieve improved adhesiveness to the corresponding adherend TLCP
film.
[0042] According to the second and third aspects, by using an
adhesive TLCP film that is excellent in thermo-adhesiveness to the
corresponding TLCP film as the adherend film, interlayer adhesion
between TLCP films can be enhanced so as to suppress local adhesion
failure. Accordingly, usage of the specific adhesive film make it
possible to efficiently produce a circuit board that can inhibit
occurrence of blisters on the circuit board during a high
temperature treatment such as a reflow process for mounting
electronic components on the circuit board. In particular, since
the circuit board can enhance interlayer adhesion without adhesive
usage, reliability of the circuit board can be enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] In any event, the present invention will become more clearly
understood from the following description of preferred embodiments
thereof, when taken in conjunction with the accompanying drawings.
However, the embodiments and the drawings are given only for the
purpose of illustration and explanation, and are not to be taken as
limiting the scope of the present invention in any way whatsoever,
which scope is to be determined by the appended claims, and:
[0044] FIGS. 1A and 1B are schematic cross-sectional views for
explaining a production process of a circuit board according to an
embodiment of the present invention, and show statuses before and
after lamination, respectively;
[0045] FIGS. 2A and 2B are schematic cross-sectional views for
explaining a production process of a circuit board according to
another embodiment of the present invention, and show statuses
before and after lamination, respectively;
[0046] FIG. 3A is a schematic view for explaining a status before
lamination as for each of the multilayer circuit boards produced in
Examples 1 to 4; and
[0047] FIG. 3B is a schematic view for explaining a status after
lamination as for each of the multilayer circuit boards produced in
Examples 1 to 4.
DESCRIPTION OF EMBODIMENTS
[0048] Method for Producing TLCP Film
[0049] The first aspect of the present invention is based on the
findings as below, that is, (i) it has been conventionally
recognized as a critical contributor that improvement in
adhesiveness of a TLCP film necessarily requires destruction of a
surface skin layer of the TLCP film because the skin layer made of
rigid mesogenic groups inevitably intervene thermo-adhesion between
TLCP films; on the contrary, (ii) it is more important for a
plurality of TLCP films that the TLCP films used as an adhcrend
film and an adhesive film should have a specific relationship with
each other regarding a sum of relative peak areas of C--O and COO
bond peaks based on the total area of C1s peaks in X-ray
photoelectron spectroscopy analysis. Surprisingly, where the
adherend TLCP film has a specific relationship with an adhesive
TLCP film as described above, interlayer adhesion between the TLCP
films can be greatly improved in spite of the presence or absence
of the destruction of the skin layers.
[0050] The first aspect of the present invention relates to a
method for producing a TLCP film as an adhesive film to be
thermo-bonded to an adherend body of a TLCP film (hereinafter,
sometimes referred to as an adherend film), the method at least
including:
[0051] preparing a TLCP film as the adherend film and a TLCP film
as the adhesive film;
[0052] examining each of the prepared TLCP films for a relative
intensity calculated as a ratio in percentage of a sum of peak
areas of C--O bond peak and COO bond peak based on the total area
of C1s peaks in the XPS spectral profile so as to calculate X (%)
as for the prepared adherend film and Y (%) as for the prepared
adhesive film; and
[0053] controlling the TLCP film as the adhesive film to have a
specific relative intensity Y by selection or activation treatment
of the adhesive film so that the relative intensity X of the
adherend film and the relative intensity Y of the controlled
adhesive film satisfy the following formulae (1) and (2):
38<X+Y<65 (1)
-8.0<Y-X<8.0 (2).
[0054] TLCP Film
[0055] The TLCP film to be used as an adherend film as well as an
adhesive film is formed from a melt-processable liquid crystalline
polymer. Chemical formulation of the thermoplastic liquid crystal
polymer is not particularly limited to a specific one as long as it
is a liquid crystalline polymer that can be melt-processable, and
examples thereof may include a thermoplastic liquid crystal
polyester, or a thermoplastic liquid crystal polyester amide
obtained by introducing an amide bond thereto.
[0056] Furthermore, the thermoplastic liquid crystal polymer may be
a polymer obtained by further introducing, to an aromatic polyester
or an aromatic polyester amide, an imide bond, a carbonate bond, a
carbodiimide bond, or an isocyanate-derived bond such as an
isocyanurate bond.
[0057] Specific examples of the thermoplastic liquid crystal
polymer used in the present invention may include known
thermoplastic liquid crystal polyesters and thermoplastic liquid
crystal polyester amides obtained from compounds classified as (1)
to (4) as exemplified in the following, and derivatives thereof.
However, it is needless to say that, in order to form a polymer
capable of forming an optically anisotropic melt phase, there is a
suitable range regarding the combination of various raw-material
compounds.
[0058] (1) Aromatic or aliphatic dihydroxy compounds (see Table 1
for representative examples)
TABLE-US-00001 TABLE 1 Chemical structural formulae of
representative examples of aromatic or aliphatic dihydroxyl
compounds ##STR00001## ##STR00002## ##STR00003## ##STR00004##
[0059] (2) Aromatic or aliphatic dicarboxylic acids (see Table 2
for representative examples)
TABLE-US-00002 TABLE 2 Chemical structural formulae of
representative examples of aromatic or alphatic dicarboxylic acids
##STR00005## ##STR00006## ##STR00007## ##STR00008## ##STR00009##
##STR00010## ##STR00011##
[0060] (3) Aromatic hydroxycarboxylic acids (see Table 3 for
representative examples)
TABLE-US-00003 TABLE 3 Chemical structural formulae of
representative examples of aromatic or alphatic hydroxycarboxylic
acids ##STR00012## ##STR00013## ##STR00014##
[0061] (4) Aromatic diamines, aromatic hydroxy amines, and aromatic
aminocarboxylic acids (see Table 4 for representative examples)
TABLE-US-00004 TABLE 4 Chemical structural formulae of
represenative examples of aromatic diamines, aromatic hydroxy
amines, or aromatic aminocarboxylic acids ##STR00015##
##STR00016##
[0062] Representative examples of liquid crystal polymers obtained
from these raw-material compounds may include copolymers having
structural units shown in Tables 5 and 6.
TABLE-US-00005 TABLE 5 Representative examples (1) of a
thermoplastic liquid crystal polymer ##STR00017## (A) ##STR00018##
(B) ##STR00019## (C) ##STR00020## ##STR00021## (D) ##STR00022##
##STR00023## (E) ##STR00024## (F) ##STR00025##
TABLE-US-00006 TABLE 6 Representative examples (2) of thermoplastic
liquid crystal polymer ##STR00026## (G) ##STR00027## (H)
##STR00028## (I) ##STR00029## (J) ##STR00030##
[0063] Of these copolymers, polymers including at least
p-hydroxybenzoic acid and/or 6-hydroxy-2-naphthoic acid as
repeating units are preferable; and particularly preferred polymers
include:
[0064] a polymer (i) having repeating units of p-hydroxybenzoic
acid and 6-hydroxy-2-naphthoic acid, and
[0065] a polymer (ii) having repeating units of [0066] at least one
aromatic hydroxycarboxylic acid selected from a group consisting of
p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, [0067] at
least one aromatic diol selected from a group consisting of
4,4'-dihydroxybiphenyl and hydroquinone, and [0068] at least one
aromatic dicarboxylic acid selected from a group consisting of
terephthalic acid, isophthalic acid, and 2,6-naphthalene
dicarboxylic acid.
[0069] For example, in the case where the polymer (i) comprises a
thermoplastic liquid crystal polymer having repeating units of at
least p-hydroxybenzoic acid (A) and 6-hydroxy-2-naphthoic acid (B),
the liquid crystal polymer may have a mole ratio (A)/(B) of
preferably about (A)/(B)=10/90 to 90/10, more preferably about
(A)/(B)=50/50 to 85/15, and further preferably about (A)/(B)=60/40
to 80/20.
[0070] Furthermore, in the case where the polymer (ii) comprises a
liquid crystal polymer having repeating units of at least one
aromatic hydroxycarboxylic acid (C) selected from a group
consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid,
at least one aromatic diol (D) selected from a group consisting of
4,4'-dihydroxybiphenyl and hydroquinone, and at least one aromatic
dicarboxylic acid (E) selected from a group consisting of
terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic
acid, the liquid crystal polymer may have a mole ratio of aromatic
hydroxycarboxylic acid (C): aromatic diol (D): aromatic
dicarboxylic acid (E)=30 to 80:35 to 10:35 to 10, more preferably
about (C):(D):(E)=35 to 75:32.5 to 12.5:32.5 to 12.5, and further
preferably about (C):(D):(E)=40 to 70:30 to 15:30 to 15.
[0071] Furthermore, the liquid crystal polymer may have a mole
ratio of a repeating structural unit derived from an aromatic
dicarboxylic acid relative to a repeating structural unit derived
from an aromatic diol of preferably (D)/(E) =95/100 to 100/95.
Deviation from this range may tend to result in a low degree of
polymerization and deterioration in mechanical strength.
[0072] It should be noted that, in the present invention, optical
anisotropy in a molten state can be determined by, for example,
placing a sample on a hot stage, heating the sample with an
elevating temperature under nitrogen atmosphere, and observing
light transmitted through the sample. Preferred thermoplastic
liquid crystal polymer has a melting point (hereinafter, referred
to as Tm.sub.o) in a range from 260.degree. C. to 360.degree. C.,
and more preferably from 270.degree. C. to 350.degree. C. The
melting point is determined by measuring the temperature at which
the main endothermic peak appears using a differential scanning
calorimeter (Shimadzu Corporation DSC).
[0073] As long as the advantageous effect of the present invention
is not deteriorated, to the thermoplastic liquid crystal polymer,
may be added any thermoplastic polymer such as a polyethylene
terephthalate, a modified polyethylene terephthalate, a polyolefin,
a polycarbonate, a polyarylate, a polyamide, a polyphenylene
sulfide, a polyether ether ketone, and a fluorine resin; and/or
various additives. If necessary, a filler may be added to the
thermoplastic liquid crystal polymer.
[0074] The TLCP film used in the present invention can be obtained
by extruding a thermoplastic liquid crystal polymer. As long as the
direction of rigid rod-like molecules in the thermoplastic liquid
crystal polymer can be controlled, any extrusion method may be
applied. In particular, well-known methods such as a T-die method,
a laminate-stretching method, and an inflation method (tubular
blown film extrusion method) are industrially advantageous. In
particular, the inflation method or the laminate-stretching method
can apply stresses not only in a machine direction of the film (or
the machine processing direction, hereinafter referred to as MD
direction), but also in a transverse direction (hereinafter,
abbreviated as TD direction) perpendicular to the MD direction.
Accordingly, the inflation method or the laminate-stretching method
can be advantageously used to obtain a film having controlled
properties such as molecular orientation and dielectric
characteristics in both the MD and TD directions.
[0075] If necessary, the extrusion-molded TLCP film may be further
subjected to stretching. The stretching method itself is known, and
either biaxial stretching or uniaxial stretching may be employed.
From the viewpoint of easy control of molecular orientation,
biaxial stretching is preferable. The stretching may be carried out
using a known machine such as a uniaxial stretching machine, a
simultaneous biaxial stretching machine, and a sequential biaxial
stretching machine.
[0076] If necessary, a known or conventional heat treatment may be
carried out in order to control a melting point and/or thermal
expansion coefficient of the TLCP film. Heat treatment conditions
can be set appropriately depending on the purpose. The heat
treatment may be carried out by heating for several hours at a
temperature of, for example, (Tm.sub.0-10).degree. C. or higher,
wherein Tm.sub.0 denotes a melting point of a liquid crystal
polymer, for example, about (Tm.sub.0-10).degree. C. to
(Tm.sub.0+30).degree. C., and preferably about Tmo.degree. C. to
(Tm.sub.0+20).degree. C. to increase a melting point (Tm) of the
TLCP film.
[0077] Thus-obtained TLCP film according to the present invention
has improved properties such as dielectric properties, gas barrier
properties and low moisture absorption, thus the TLCP film can be
suitably used as a circuit board material.
[0078] In order to achieve desired heat resistance and
processability of the film, the melting point (Tm) of the TLCP film
may be selected in a range from about 200.degree. C. to 400.degree.
C., preferably about 250.degree. C. to 360.degree. C., more
preferably about 260.degree. C. to 340.degree. C. It should be
noted that the melting point of the film could be determined by
observing the thermal behavior of the film using a differential
scanning calorimeter. That is, a test film is heated at a rate of
20.degree. C./min to completely melt the film, and the melt is
rapidly cooled or quenched to 50.degree. C. at a rate of 50.degree.
C./min. Subsequently, the quenched material is reheated at a
heating rate of 20.degree. C./min., and a position of an
endothermic peak appearing in the reheating process may be recorded
as a melting point of the film.
[0079] The TLCP film may have a Segment Orientation Ratio SOR, as
an indicator of isotropic property of the film, of, for example,
0.8 to 1.4, preferably 0.9 to 1.3, more preferably 1.0 to 1.2, and
particularly preferably 1.0 to 1.1. Here, the Segment Orientation
Ratio SOR is an index descriptive of a degree of molecular
orientation, and represents, unlike the standard MOR (Molecular
Orientation Ratio), a value that takes the thickness of an object
into consideration.
[0080] The TLCP film used in the present invention may have any
thickness. Where the TLCP film is used in a high-frequency
transmission line, the TLCP film may have a thickness as thick as
possible because usage of a thicker film can reduce transmission
loss. Where a TLCP film is used as an electrically insulating
layer, the film may preferably have a thickness in a range from 10
to 500 .mu.m, and more preferably in a range from 15 to 200 gm.
Since a film having too small thickness has small rigidity and poor
strength, it is possible to achieve a desired thickness by
laminating the films having a thickness in a range from 10 to 200
.mu.m.
[0081] Examination of Surface States of Films
[0082] Surface states of thermoplastic liquid crystal polymer films
as an adherend film and an adhesive film are examined (or detected)
by X-ray photoelectron spectroscopy analysis.
[0083] In the X-ray photoelectron spectroscopy analysis (XPS
analysis), X-ray that is irradiated to a surface of a subject
material activates electrons of atomic orbitals in the surface
atoms. As a result, the activated electrons are emitted outside the
orbitals as photoelectrons. It is possible to determine the species
of elements and oxidation states of the elements in the surface of
the material by detecting kinetic energies of the
photoelectrons.
[0084] Energy peak positions of 1 s orbital of carbon, hereinafter
expressed as C1s peak positions, can be used to examine (evaluate)
various bonding states of carbon atoms. For example, in accordance
with the XPS analysis in the below-described Examples, it is
possible to separate C1s peaks to each of bond peaks such as C--C
bond peak at 284.8 eV, C--O bond peak at 286.6 eV, C.dbd.O bond
peak at 287.6 eV, COO bond peak at 288.6 eV, CO.sub.3 bond peak at
290 to 291 eV, and .pi.-.pi.* satellite peak at 291.9 eV.
[0085] For example, in a first examination, a TLCP film used as an
adherend film may be subjected to X-ray photoelectron spectroscopy
analysis.
[0086] In the first examination, a surface portion of the adherend
film to be adhered to the adhesive film is examined (measured) by
X-ray photoelectron spectroscopy analysis to determine a relative
intensity X (%) that is a sum of C--O and COO peak areas calculated
as a ratio in percentage of a sum of peak areas of C--O bond peak
and COO bond peak based on the total area of each of the C1s peaks
in the XPS spectral profile, where a peak area denotes an area from
a background base line to a bond peak. That is, in the examination,
the surface of the adherend film was analyzed by X-ray
photoelectron spectroscopy to obtain a first relative intensity X
(hereafter sometimes referred to as relative intensity X) relating
to the adherend film, the first relative intensity X being a ratio
in percentage of a sum of peak areas of C--O bond peak and COO bond
peak based on the total area of C1s peaks in the XPS spectral
profile.
[0087] In a second examination, a TLCP film used as an adhesive
film may be subjected to X-ray photoelectron microscopy
analysis.
[0088] In the second examination, a TLCP film is prepared as an
adhesive film, and an adhesive surface portion (surface to be
adhered to the adherend film) of the film is examined (measured) by
X-ray photoelectron spectroscopy analysis to determine a relative
intensity Y (%) that is a sum of C--O and COO peak areas calculated
as a ratio in percentage of a sum of peak areas of C--O bond peak
and COO bond peak based on the total area of each of the C1s peaks
in the XPS spectral profile.
[0089] In the method for producing the adhesive film, the order of
the first and second examinations for determining the surface
states of films is not particularly limited. The first examination
may be carried out before the second examination, i.e., the surface
state of the adherend film may be examined before the examination
of the surface state of the adhesive film. Alternatively, the
second examination may be carried out before the first examination,
i.e., the adhesive film may be subjected to the examination of
surface state before the examination of the surface state of the
adherend film. Alternatively, the first and second examinations may
be substantially simultaneously carried out, i.e., both the
adherend and adhesive film may be subjected to the examination of
surface states substantially at the same time. After the
examination of surface states of the films, the surface state of
the adhesive film is controlled in order to have satisfactory
adhesiveness to the adherend film.
[0090] Control of Surface State
[0091] As for the TLCP film as the adhesive film, the surface state
of the film has been preliminarily examined. In the controlling
process, the TLCP film used as the adhesive film is controlled to
have a desired surface state depending on the examination result of
the relative intensity X of the adherend film. That is, the TLCP
film as the adhesive film may be selected or treated in order for
the portion to be adhered to have a second relative intensity Y
(hereafter sometimes referred to as relative intensity Y), that is
a sum of relative peak areas of C--O and COO bond peaks based on
the total area of each of the C1s peaks in the XPS spectral
profile.
[0092] In the controlling process, the adhesive film is selected or
treated such that the relative intensity Y (%) satisfies following
formulae (1) and (2) with respect to a predetermined relative
intensity X (%):
38<X+Y<65 (1)
-8.0<Y-X<8.0 (2).
[0093] The formula (1) shows that high adhesiveness can be obtained
where both of the adhesive film and the adherend film have specific
activation energy states. The formula (2) shows that high
adhesiveness can be obtained where the surfaces of the adhesive
film and the adherend film show similar activation states with each
other. Where these formulae are satisfied, it is possible to
improve thermo-adhesiveness of the adhesive film to the adherend
film, for example, even when the skin layer of the film is not
destroyed by an activating treatment.
[0094] In the above-described formula (1), for example, X+Y may be
50 or less, or less than 42. In the above-described formula (2),
for example, Y-X may be -7.5 or more, -5.0 or more, -2.0 or more,
or -1.0 or more.
[0095] Y-X may be 7.5 or less, 5.0 or less, 2.0 or less, or 1.0 or
less. Y--X may satisfy any combination of the above-described
ranges. Preferably, |Y--X| satisfies 7.5 or less, 5.0 or less, 2.0
or less, or 1.0 or less.
[0096] Surprisingly, by controlling the surface state of the
adhesive film to show a relative intensity Y within the
predetermined range depending on the surface state of the adherend
film having the relative intensity X, it is possible to improve
interlayer adhesiveness between LCP films, even when at least one
of the films has a sum of relative peak areas of C--O and COO bond
peaks of less than 21% based on the total area of C1s peaks in the
XPS spectral profile. For example, the relative intensity X (%) of
the adherend film may be 30% or less (for example, 15 to 30%),
preferably 25% or less, more preferably less than 21%, and even
more preferably 20% or less.
[0097] In relation with the relative intensity X (%) of the
adherend film, the relative intensity Y (%) of the adhesive film
may be 30% or less (for example, 15 to 30%), preferably 25% or
less, more preferably less than 21%, and even more preferably 20%
or less.
[0098] In the controlling process, the relative intensity Y of the
adhesive film is controlled to have a specific value in relation
with the relative intensity X of the adherend film depending on the
surface state of the adherend film. For example, the adhesive film
may be selected from films having a predetermined relative
intensity Y in relation with the relative intensity X of the
adherend film. Alternatively, where the adhesive film does not have
a relative intensity Y within the predetermined range in relation
with the relative intensity X of the adherend film, it is possible
to control (modify) the relative intensity Y by activating
treatment of the surface of the adhesive film.
[0099] For example, the relative intensity Y of the adhesive film
may be controlled to have a desired value by activating treatment
of the film surface, for example, by ultraviolet (UV) ray
irradiation, by plasma irradiation, and/or by corona discharge
treatment.
[0100] For example, the inventor have found that a ratio in
percentage of a sum of relative peak areas of C--O and COO bond
peaks of an LCP film is increased by enhanced ultraviolet
irradiation dose where ultraviolet ray with a predetermined
wavelength is irradiated to the surface of the LCP film. Such a
phenomenon can be used to control the relative intensity to be in
the predetermined range.
[0101] In addition, it is expected that a ratio in percentage of a
sum of relative peak areas of C--O and COO bond peaks of an LCP
film can be increased by enhancing an amount to be treated by other
surface activation treatment such as plasma treatment and corona
discharge treatment. Therefore, it is also possible to control a
sum of relative peak areas of C--O and COO bond peaks of the LCP
film so as to be within the predetermined range by the various
activation treatments.
[0102] In the case of UV irradiation, types of the UV rays are not
particularly limited provided that the relative intensity Y can be
controlled to be in the predetermined range. For example, UV ray of
185 nm in wavelength or UV ray of 254 nm in wavelength may be
irradiated to the film. Alternatively, UV rays having different
wavelengths (for examples UV rays of 185 nm and 254 nm in
wavelengths) may be irradiated to the film simultaneously.
[0103] Preferably, the distance between the film surface to be
irradiated and the light source may be shortened so as to irradiate
higher energy radiation for a short period of time. For example,
the distance between the film surface and the light source may be
set in the range of about 0.3 to 5 cm, and preferably about 0.4 to
2 cm. The treatment period may be set arbitrarily. For example, it
is possible to employ a treatment period in the range of about 20
seconds to about 5 minutes, and preferably in the range of about 30
seconds to about 3 minutes.
[0104] The plasma treatment may be performed under atmospheric
pressure or under vacuum conditions. Plasma may be generated by
applying microwave or high frequency wave to oxidizing gas
introduced into an apparatus. The generated plasma may be
irradiated to an object to be treated so as to plasma-treat the
surface of the object.
[0105] For example, the oxidizing gas may be selected from oxygen
and other oxygen-containing gas such as air, carbon mono-oxide, and
carbon dioxide.
[0106] Preferably, for example, the plasma treatment may be
performed under a vacuum pressure of 1000 Pa or less, and
preferably 800 Pa or less.
[0107] Direct plasma (DP) or reactive ion etching (RIE) may be used
in the plasma treatment. The output energy may be arbitrarily
selected depending on the irradiation mode, treatment period or the
like. For example, the plasma treatment may be performed with
output of about 0.2 to about 2.0 W/cm.sup.2, and preferably about
0.2 to about 1.0 W/cm.sup.2.
[0108] The treatment period may be for example in a range of about
30 to 200 seconds, preferably in a range of about 30 to 100
seconds, and more preferably in a range of about 40 to 80
seconds.
[0109] In the corona discharge treatment, the film may be passed
through a space between an electrode and a roll of dielectric
material, both being insulated with each other, and corona
discharge is generated by applying high frequency (for example, 40
kHz or the like) and high voltage electric current. The corona
discharge produces plasma from gas components such as oxygen, and
thereby activating the polymer surface.
[0110] For example, metals such as stainless steel and aluminum may
be used as the electrode. Ceramics, silicone rubber, EPT rubber,
hypalon rubber, or the like may be used as the dielectric material.
The electrode may have various shapes such as knife-edge, plate,
roll, and wire. The output power may be selected depending on the
treatment period or the like. For example, the corona discharge
treatment may be performed with output power of about 100 W to
about 800 W, and preferably about 200 W to about 600 W. Moving
speed of the film may be, for example, about 2 to 10 m/min.,
preferably about 3 to 9 m/min.
[0111] Preferably, after the activating treatment of the adhesive
film, the adhesive film may be further subjected to X-ray
photoelectron spectroscopy analysis to re-examine the relative
intensity Y after the treatment so as to determine whether the
relative intensity Y satisfies the above-described formulae 1 and
2. Where necessary, the activation treatment may be preferably
performed (repeated) until the relative intensity Y satisfies the
above-described formulae 1 and 2.
[0112] Degassing Process
[0113] If necessary, the adhesive LCP film may be subjected to
degassing before or after the controlling process.
[0114] The degassing of a TLCP film can be carried out by degassing
the TLCP film under a specific vacuum condition and/or degassing
under a specific heat condition to reduce gas components in the
TLCP film at an extremely low degree. As a result, surprisingly,
the TLCP film that has undergone such a degassing process can
improve the thermo-adhesive property.
[0115] In the degassing process, degassing of the TLCP film can be
carried out (i) by degassing under vacuum of 1500 Pa or lower for
30 minutes or more, and/or (ii) by degassing under heating at a
temperature ranging from 100.degree. C. to 200.degree. C.
[0116] The degassing process may be carried out in a condition
satisfying either degassing (i) under vacuum, or degassing (ii)
under heating, preferably in a condition satisfying both (i) and
(ii).
[0117] Where degassing under vacuum (i) and degassing under heating
(ii) are carried out in combination to the extent that
thermo-adhesiveness of the TLCP film is capable of being increased,
the degassing processes (i) and (ii) may be carried out in any
order, preferably carried out by degassing under heating (ii) as a
first degassing, followed by degassing under vacuum (i) as a second
degassing.
[0118] Specifically, for example, degassing process may comprise a
first degassing process in which degassing of the adhesive film is
carried out under heating at a temperature ranging from 100.degree.
C. to 200.degree. C. for a predetermined time, and a second
degassing process in which degassing of the adhesive film is
carried out under vacuum of 1500 Pa or lower for another
predetermined time. These degassing processes may be appropriately
carried out by combining the above-mentioned conditions.
[0119] Moreover, from the viewpoint of improving degassing
efficacy, degassing may be carried out without substantial
pressurization (under pressure release). For example, degassing may
be carried out under a minimum pressure or pressure-released state
(for example, under a compression pressure of about 0 to 0.7 MPa,
preferably under a compression pressure of about 0 to 0.5 MPa).
[0120] Degassing under vacuum (i) may be carried out at a vacuum
degree of 1500 Pa or lower, preferably 1300 Pa or lower, and more
preferably 1100 Pa or lower.
[0121] Where degassing under vacuum is performed independently,
degassing may be carried out at an ambient temperature (for
example, from 10.degree. C. to 50.degree. C., preferably from
15.degree. C. to 45.degree. C.). In view of enhancing the degassing
efficiency, degassing may be carried out under heating, for
example, at a heating temperature ranging from 50.degree. C. to
200.degree. C. (for example, from 50.degree. C. to 150.degree. C.),
preferably from 80.degree. C. to 200.degree. C., and more
preferably from about 90.degree. C. to about 190.degree. C.
[0122] Degassing under heating (ii) may be carried out in a range
from 100.degree. C. to 200.degree. C., preferably from 105.degree.
C. to 190.degree. C., and more preferably from 110.degree. C. to
180.degree. C.
[0123] Degassing temperature under heating may be set in a
predetermined temperature range with respect to a melting point
(Tm) of the TLCP film. Degassing may be carried out by heating at a
temperature ranging from (Tm-235).degree. C. to (Tm-50).degree. C.
[e.g., from (Tm-200).degree. C. to (Tm-50).degree. C.], preferably,
from (Tm-225).degree. C. to (Tm-60).degree. C. [e.g., from
(Tm-190).degree. C. to (Tm-60).degree. C.], and more preferably
from (Tm-215).degree. C. to (Tm-70).degree. C. [e.g., from
(Tm-180).degree. C. to (Tm-70).degree. C.].
[0124] By heating the TLCP film in a specific temperature range as
described above, while suppressing rapid moisture generation from
the film, the moisture in the film (for example, inside or on a
surface of the film) can be degassed as water vapor, or the air on
the surface of the film can be degassed by enhancing kinetic energy
of the air.
[0125] It should be noted that where degassing under heating is
carried out independently, the degassing might be carried out under
a condition that does not contain the vacuum condition of 1500 Pa
or lower. For example, degassing may be carried out by heating
under an atmospheric pressure (or ambient pressure) where the
pressure is not specifically adjusted. Alternatively, if necessary,
degassing may be carried out by heating under a reduced pressure
from the atmospheric pressure (for example, beyond 1500 Pa and less
than 100000 Pa, preferably about 3000 to 50000 Pa).
[0126] The period of time required for degassing procedure may be
suitably set depending on various conditions such as a state of the
TLCP film, a vacuum degree, and/or a heating temperature. In view
of removing moisture and air from the entire TLCP film, the period
for degassing for the degassing process (i) and/or the degassing
process (ii) (i.e., under vacuum, under heating, under vacuum while
heating) may be same or different. The degassing period may be 30
minutes or more, 40 minutes or more, or 50 minutes or more. The
degassing period may be 6 hours or less, 4 hours or less, 3 hours
or less, 2 hours or less, or 1.5 hours or less.
[0127] Alternatively, the degassing period may be set appropriately
depending on the moisture content in the TLCP film, for example,
may be carried out until the TLCP film has a desired moisture
content range to be described later (for example, 300 ppm or less,
or 200 ppm or less).
[0128] The TLCP film obtained by the degassing process may have
extremely low moisture. The moisture content may be, for example,
300 ppm or less, preferably 200 ppm or less, more preferably 180
ppm or less, and even more preferably 150 ppm or less. Here, the
moisture content indicates a value measured by the method described
in Examples below.
[0129] The TLCP film may have a dielectric loss tangent at 25 GHz
of, for example, 0.0025 or less (e.g., about 0.0001 to 0.0023), and
preferably about 0.0010 to 0.0022. The TLCP film having such a
dielectric loss tangent enables to lower power consumption as well
as to reduce noise.
[0130] The relative dielectric constant of the TLCP film varies
depending on the thickness of the film. The TLCP film may have a
relative dielectric constant at 25 GHz in the TD direction, for
example, of 3.25 or less (e.g., about 1.8 to 3.23), and preferably
about 2.5 to 3.20. It should be noted that the dielectric constant
can be generally calculated by multiplying the vacuum dielectric
constant (=8.855.times.10.sup.-12 (F/m)) to relative dielectric
constant.
[0131] For example, the dielectric constant measurement may be
carried out by a resonance perturbation method at a frequency of 1
GHz. Where a 1 GHz cavity resonator (manufactured by Kanto
Electronic Application and Development Inc.) is connected to a
network analyzer ("E8362B", manufactured by Agilent Technologies,
Inc.), and a small sample (width: 2.7 mm.times.length: 45 mm) is
inserted into the cavity resonator, the dielectric constant and the
dielectric loss tangent of the sample can be measured from the
change in resonance frequency before and after inserting the
material to expose the material to an environment at a temperature
of 20.degree. C. and a humidity of 65%(RH) for 96 hours.
[0132] Method for Producing Circuit Board
[0133] An embodiment of the present invention may include a method
for producing a circuit board having an improved interlayer
adhesion.
[0134] The method for producing a circuit board comprising a TLCP
film as an adherend film and a TLCP film as an adhesive film, the
both films being laminated by thermo-bonding, the method
including:
[0135] preparing the adherend film and the adhesive film as circuit
board materials;
[0136] stacking the adherend film and the adhesive film in
accordance with a predetermined structure of a circuit board to
obtain a stacked material, followed by conducting
thermo-compression bonding of the stacked material by heating under
a predetermined compression pressure; wherein
[0137] the prepared circuit board materials are independently at
least one member selected from the group consisting of an
insulating substrate having a conductor layer on at least one
surface, a bonding sheet, and a coverlay; and
[0138] the adhesive film is a TLCP film produced by the
above-described method.
[0139] Preparation of Circuit Board Materials
[0140] In the preparation process, there are prepared an adherend
body comprising a TLCP film (hereinafter sometimes simply referred
to as an adherend film) and an adhesive film comprising a TLCP film
(hereinafter sometimes simply referred to as an adhesive film). The
adherend film as well as the adhesive film are prepared as circuit
board materials comprising independently at least one member
selected from the group consisting of an insulating substrate, a
bonding sheet, and a coverlay, where the insulating substrate
having a conductor layer (e.g., a conductor circuit or a conductor
pattern, a conductor foil, a conductor film) on at least one
surface.
[0141] Examples of the insulating substrates each having a
conductor layer on at least one surface may include:
[0142] a unit circuit board comprising an insulating substrate and
a conductor circuit or pattern formed on one surface of the
insulating substrate;
[0143] a unit circuit board comprising an insulating substrate and
conductor circuits or patterns formed on both surfaces of the
insulating substrate, respectively;
[0144] a unit circuit board comprising an insulating substrate, a
conductor circuit or pattern formed on one surface of the
insulating substrate, and a conductor film or foil formed on the
other surface of the insulating substrate; and others.
[0145] The conductor layer can be at least formed for example from
a conductive metal. By using a known circuit processing method, the
conductor layer may be formed into any pattern of circuits. As the
conductor for forming a conductor layer, there may be mentioned
various metals having conductivity, such as gold, silver, copper,
iron, nickel, aluminum, and an alloy metal thereof.
[0146] Any known method may be used as a method for forming a
conductor layer on an insulating substrate of a TLCP film. For
example, a metal layer may be formed by evaporation, electroless
plating, and/or electrolytic plating. Alternatively, a metal foil
(for example, copper foil) may be thermo-compression bonded on a
surface(s) of the TLCP film.
[0147] The metal foil constituting the conductor layer may be
preferably a metal foil used in electrical connections. Examples of
the metal foils may include a copper foil, as well as various metal
foils such as gold, silver, nickel, aluminum foils, and also an
alloy foil comprising these metals in a substantial manner (for
example, 98% by weight or greater).
[0148] Of these metal foils, a copper foil can be preferably used.
The species of the copper foil is not particularly limited, and can
be any of copper foil usable in the circuit board, for example, a
rolled copper foil or an electrolytic copper foil.
[0149] The combination of the adherend film and the adhesive film
is not limited to a specific one as long as the adhesive film has
an above-described specific relationship to the adherend film and
both films are laminated by thermo-bonding.
[0150] For example, the adherend film may be an insulating
substrate having a conductor circuit on at least one surface, and
the adhesive film may be at least one member selected from the
group consisting of an insulating substrate having a conductor
circuit on at least one surface, a bonding sheet, and a
coverlay.
[0151] For example, the adhesive film may be an insulating
substrate having a conductor circuit on at least one surface, and
the adherend film may be at least one member selected from the
group consisting of an insulating substrate having a conductor
circuit on at least one surface, a bonding sheet, and a
coverlay.
[0152] Examples of combinations of the adhesive and adherend films
may include:
[0153] (a) a circuit board at least including an adherend film as
an insulating substrate and an adhesive film as a coverlay to cover
a conductor circuit formed on the adherend film (here the adhesive
film is controlled to have a predetermined relative intensity Y
respective to the relative intensity X of the adherend film);
[0154] (b) a circuit board at least including a first adherend film
and a second adherend film as insulating substrates and an adhesive
film as a bonding sheet to adhere to both of the first and second
adherend films (here the adhesive film is controlled to have
predetermined relative intensities Y1 and Y2 on each of the
adhesive surfaces respective to the relative intensities X1 and X2
of the first and second adherend films, respectively);
[0155] (c) a circuit board at least including an adhesive film as
an insulating substrate and an adherend film as a coverlay to cover
a conductor circuit formed on the adhesive film (here the adhesive
film is controlled to have a predetermined relative intensity Y
respective to the relative intensity X of the adherend film);
[0156] (d) a circuit board at least including a first adhesive film
and a second adhesive film as insulating substrates and an adherend
film as a bonding sheet to adhere both the first and second
adhesive films (here the adhesive film is controlled to have a
predetermined relative intensities Y1 and Y2 on each of the
adhesive surfaces respective to the relative intensities X1 and X2
of the first and second adherend films, respectively);
[0157] (e) a circuit board at least including an adherend film as a
first insulating substrate and an adhesive film as a second
insulating substrate to be adhered to the first insulating
substrate (here the adhesive film is controlled to have a
predetermined relative intensity Y respective to the relative
intensity X of the adherend film); and other combinations.
[0158] It should be noted that, if necessary, a coverlay might be
optionally provided to cover a conductor circuit of an insulating
substrate on an outermost layer. In such a case, the coverlay and
the insulating substrate may be an adhesive film and an adherend
film, respectively, or vice versa. In any case, there is a specific
relationship between adherend and adhesive LCP films adjacent with
each other such that the adhesive film have a predetermined
relative intensity Y respective to the relative intensity X of the
adherend film.
[0159] Among them, a preferable embodiment includes a circuit board
including an adherend film as an insulating substrate having a
conductor circuit on at least one surface and an adhesive film as
at least one circuit board material selected from the group
consisting of an insulating substrate having a conductor circuit on
at least one surface, a bonding sheet, and a coverlay.
[0160] In the circuit board, the TLCP film type of the adherend
film may be same with or different from the type of the adhesive
film. For example, the adherend film and the adhesive film may be a
first TLCP film and a second TLCP film, respectively. For example,
the first TLCP film may have a melting point that is same with a
melting point of the second TLCP film. Alternatively, the first
TLCP and second TLCP films may have melting points that are
different from each other, i.e., one may be a TLCP film having a
higher melting point (for example, a melting point of about 300 to
350.degree. C.), or a high-melting-point TLCP film, and the other
may be a TLCP film having a lower melting point (for example, a
melting point of about 250 to 300.degree. C.) than that of the
former TLCP film, or a low-melting-point TLCP film. For example,
the difference in melting point between the first and second LCP
films may be, for example, in a range about from 0 to 60.degree.
C., and more preferably about from 0 to 50.degree. C. (for example
10.degree. C. to 50.degree. C.).
[0161] The adhesive film may be used as a high-melting-point TLCP
film or as a low-melting-point TLCP film. For example, the adherend
film and the adhesive film may be both high-melting-point TLCP
films; alternatively, the adherend film and the adhesive film may
be both low-melting-point TLCP films. For example, in this case,
difference in melting point between the adherend film and the
adhesive film may be, for example, about 0.degree. C. to 20.degree.
C., and more preferably about 0.degree. C. to 10.degree. C.
[0162] Alternatively, one of the adherend film and the adhesive
film may be a high-melting-point TLCP film and the other may be a
low-melting-point TLCP film. In this case, the adhesive film may be
a low-melting-point TLCP film.
[0163] In this case, particularly preferable embodiments may
include a circuit board including an adherend film of a
high-melting-point TLCP film as an insulating substrate, and an
adhesive film of a low-melting-point TLCP film as an coverlay
and/or a bonding sheet; a circuit board including an adherend film
and an adhesive film, in which both films constitute insulating
substrates each having a conductor circuit on at least one surface,
and are directly bonded to each other without a bonding sheet.
[0164] Thermo-Compression Bonding Process
[0165] In the thermo-compression bonding process, the adherend
film(s) and the adhesive film(s), both prepared as the circuit
board materials are stacked (overlaid), and the stacked circuit
board materials are thermo-compression bonded by heating at a
predetermined compression pressure.
[0166] The stacked circuit board materials may have a structure in
accordance with the before-mentioned combinations (a) to (e) or
others so that the adherend film(s) and the adhesive film(s) are
provided.
[0167] Optionally, before thermo-compression bonding process, the
above-described degassing process may be carried out to improve
thermo-adhesiveness of TLCP films.
[0168] The degassing process may be carried out by degassing the
films (i) under vacuum of 1500 Pa or lower for 30 minutes or more,
and/or by degassing the films (ii) under heating at a temperature
ranging from 100.degree. C. to 200.degree. C., and thereby
degassing TLCP films. Further, as one embodiment of the degassing
(i) under vacuum of 1500 Pa or lower for 30 minutes or more, a
pre-heating may be carried out. In this case, the pre-heating
process may be carried out prior to the thermo-compression bonding,
for example, in a heating temperature range from 50.degree. C. to
150.degree. C. under vacuum of 1500 Pa or lower for 30 minutes or
more. The heating temperature during the pre-heating process may be
preferably about 60.degree. C. to 120.degree. C., and more
preferably 70.degree. C. to 110.degree. C.
[0169] Such a pre-heating process makes it possible to remove air
and/or moisture on and/or in the LCP film to some extent. As a
result, it is possible to improve the interlayer adhesion in the
circuit board even without an adhesive agent.
[0170] The pre-heating process may be carried out under a vacuum
degree of 1500 Pa or less, preferably 1300 Pa or less, and more
preferably 1100 Pa or less.
[0171] During the pre-heating process, a compression pressure may
be applied to the circuit board material within a range that does
not inhibit the effect of the invention. The compression pressure
in the pre-heating process may be, for example, 0.8 MPa or less,
and more preferably 0.6 MPa or less. The pre-heating process may be
preferably carried out with applying a compression pressure as low
as possible, preferably substantially without applying a
compression pressure.
[0172] The pre-heating process may be carried out for about 30
minutes or more, for example, for about 30 to 120 minutes,
preferably about 40 to 100 minutes, and more preferably about 45 to
75 minutes.
[0173] Thermo-compression bonding of a stacked body can be carried
out by using a vacuum hot press apparatus, a heating roll
lamination equipment, or others, depending on the type of circuit
board materials. From the viewpoint of reducing further gas from
the LCP film, it is preferable to use a vacuum hot press
apparatus.
[0174] The heating temperature in the thermo-compression bonding
may be a temperature for example from (Tm-20).degree. C. to
(Tm+40).degree. C., and preferably from (Tm-10).degree. C. to
(Tm+30).degree. C., where Tm denotes the melting point of the TLCP
film to be bonded (where TLCP films having different melting points
with each other, Tm denotes a lower melting point in the
films).
[0175] Also, the pressure applied during thermo-compression bonding
can be selected, depending on the LCP film characteristics, for
example, from a wide range from 0.5 to 6 MPa. Where an
adhesion-improved LCP film(s) undergone the degassing process
is(are) used for bonding, satisfactory adhesion between LCP film
layers can be achieved even at a pressing pressure of 5 MPa or
less, particularly 4.5 MPa or less, resulting in avoidance of local
adhesion failure caused by air introduction in a circuit board even
after bonding.
[0176] The time required for the thermo-compression bonding
(retention time under a constant temperature and pressure) is not
particularly limited as far as the circuit board can have an
improved interlayer adhesion, and for example, may be about 15 to
60 minutes, and preferably about 20 to 40 minutes. It should be
noted that the method for producing the circuit board might
include, if necessary, various producing processes that are known
or conventional (e.g., circuit formation process,
through-connection process, inter-layer connection process).
[0177] Hereinafter, with reference to the drawings, as an
embodiment according to the present invention, there may be
mentioned a method for producing a circuit board. It should be
noted that the scope of the present invention is not limited to
these embodiments.
[0178] FIG. 1A is a schematic sectional view showing a circuit
board in a state before stacked where both surfaces of the
insulating substrate having conductor circuit on both surfaces are
covered with coverlays. Here are prepared a first unit circuit
board 14 that comprises a first TLCP film 11 as an insulating
substrate and conductor circuits (e.g., strip line pattern) formed
on both surfaces of the film 11; and second TLCP films 13, 13 as
coverlays provided on both surfaces of the first unit circuit board
14. Here the first TLCP film is an adherend film and the second
TLCP films are adhesive films. The first TLCP film and the second
TLCP film are controlled to have a specific relationship with each
other regarding a sum of relative peak areas of C--O and COO bond
peaks in each of the XPS spectral profiles as described above.
[0179] Before carrying out thermo-compression bonding, the adhesive
film and/or the adherend film may be heated for a predetermined
time preferably under a nitrogen gas atmosphere (first degassing
process). The conditions for degassing temperature and degassing
time may follow the conditions described above.
[0180] Thereafter, the coverlays 13, 13 and the first unit circuit
board 14 interposed between the coverlays are placed in stack in a
chamber of a vacuum hot press apparatus (not shown) so as to obtain
a stacked body as shown in FIG. 1B. Then, heating treatment may be
carried out for a predetermined time (second degassing process)
while retaining a vacuum degree of 1500 Pa or lower by vacuuming.
The conditions for degassing temperature and degassing period may
follow the conditions described above.
[0181] Then, while maintaining the vacuum degree of 1500 Pa or
lower, the heating temperature may be elevated to a temperature for
carrying out a thermo-compression bonding to laminate each of the
layers in the stacked body under a predetermined compression
pressure. The conditions of temperature as well as period for
thermo-compression bonding may follow the conditions described
above.
[0182] Thereafter, according to a conventional process, the
conditions inside the apparatus are returned to ambient temperature
and ambient pressure so as to collect a circuit board 10 from the
apparatus.
[0183] In the above embodiment, the first unit circuit board 14 is
attached to both of the coverlays 13, 13. Alternatively, as a
modified embodiment, a bonding sheet may be interposed between the
first unit circuit board and a second unit circuit board. As a
further modified embodiment, unit circuit boards are directly
bonded with each other without a bonding sheet.
[0184] In the embodiment shown in FIG. 1B, the circuit board has
two conductor layers. The number of conductor layers may be set
appropriately, and may be one or more layers (for example, 2 to 10
layers).
[0185] FIG. 2A is a schematic sectional view showing a status
before lamination of a circuit board including a first unit circuit
board 34 that comprises an insulating substrate 31 and conductor
circuits 32, 32 formed on both surfaces of the substrate; an upper
unit circuit board that comprises an insulating substrate 39 and a
conductor circuits 38a and a conductor layer 38b formed on both
surfaces of the substrate, respectively; a lower unit circuit board
that comprises an insulating substrate 35 and a conductor circuits
36a and a conductor layer 36b formed on both surfaces of the
substrate, respectively; and bonding sheets 33 and 37 for bonding
the unit circuit boards. The number of conductor layers is 6 layers
in the circuit board.
[0186] Each of the first TLCP films 31, 35, and 39 as insulating
substrates constitutes an adherend film. Each of the second TLCP
films 33 and 37 as bonding sheets constitutes an adhesive film. The
first TLCP films and the second TLCP films are controlled to have a
specific relationship with each other regarding a sum of relative
peak areas of C--O and COO bond peaks in each of the XPS spectral
profiles as described above.
[0187] Before carrying out thermo-compression bonding, the adhesive
film and/or the adherend film may be heated for a predetermined
time preferably under a nitrogen gas atmosphere (first degassing
process). The conditions for degassing temperature and degassing
period may follow the conditions described above.
[0188] Thereafter, the circuit board materials are placed in stack
in a chamber of a vacuum hot press apparatus (not shown) so as to
obtain a stacked body as shown in FIG. 2B. In the stacked body, the
first unit circuit board 34 is interposed between the bonding
sheets 33, 37; the conductor circuits 36a and 38b of the unit
circuit board are attached to the bonding sheets 33, 37,
respectively. Then, heating treatment may be carried out for a
predetermined period (second degassing process) while retaining a
vacuum degree of 1500 Pa or lower by vacuuming. The conditions for
degassing temperature and degassing period may follow the
conditions described above.
[0189] Subsequently, while maintaining the vacuum degree of 1500 Pa
or lower, the heating temperature is elevated to a temperature
condition for carrying out a thermo-compression bonding to laminate
each of the layers in the stacked body under a predetermined
compression pressure. The conditions of temperature as well as
period for thermo-compression bonding may follow the conditions
described above.
[0190] Thereafter, according to a conventional process, the
conditions inside the apparatus are returned to ambient temperature
and ambient pressure so as to collect a circuit board 30 from the
apparatus.
[0191] Circuit Board
[0192] The third aspect of the present invention relates to a
circuit board.
[0193] The circuit board comprises a TLCP film as an adherend film
and a TLCP film as an adhesive film, the both films being laminated
by thermo-bonding, wherein
[0194] the adherend film has a surface portion to be adhered, the
surface portion having a relative intensity X (%) calculated as a
ratio in percentage of a sum of peak areas of C--O bond peak and
COO bond peak relative to the total area of C1s peaks in the XPS
spectral profile;
[0195] the adhesive film has a surface portion to be adhered, the
surface portion having a relative intensity Y (%) calculated as a
ratio in percentage of a sum of peak areas of C--O bond peak and
COO bond peak relative to the total area of C1s peaks in the XPS
spectral profile;
[0196] the relative intensities X and Y satisfy the following
formulae (1) and (2):
38<X+Y<65 (1)
-8.0<Y-X<8.0 (2); and wherein
[0197] the circuit board shows a solder heat resistance when the
circuit board is placed in a solder bath at a temperature of
290.degree. C. for 60 seconds conforming to a method of JIS C
5012.
[0198] Preferably, the relative intensities X and Y may
appropriately satisfy the above-described relationship with respect
to each of the X+Y and Y-X.
[0199] The circuit board may be either a single-layer circuit board
or a multi-layer circuit board. Further, the circuit board may be a
circuit board produced by the above production method.
[0200] In the circuit board according to the present invention,
since the adhesive film is controlled to have a relative intensity
Y in a specific range with respect to the relative intensity X of
the adherend film, the circuit board has an improved interlayer
adhesion between LCP films.
[0201] The circuit board has an improved heat resistance, and is a
circuit board showing a solder heat resistance when the circuit
board is placed in a solder bath at a temperature of 290.degree. C.
for 60 seconds conforming to a method of JIS C 5012. The solder
heat resistance may be evaluated by observing a substrate sample
that is subjected to solder float test in a solder bath at a
temperature of 290.degree. C. for 60 seconds conforming to a method
of JIS C 5012 to be determined whether the substrate sample has
blisters each having an area of 100 .mu.m.times.100 .mu.m or wider
by sight or using an optical microscopy (5 magnifications or
higher).
[0202] Where there is a conductive material portion between the
adherend and adhesive films, the surface area ratio of the
conductive material portion existing between the adherend and
adhesive films may be less than 30%. It should be noted that the
existing ratio of conductive material might be determined as
follows:
Existing ratio of conductive material=(Surface area of conducive
material on the adhered surface)/(Surface area of the adhered
surface).times.100
[0203] Further, since the circuit board has an improved interlayer
adhesion between LCP films, the bonding strength between two LCP
films (one is an adherend film and the other is an adhesive film)
may be, for example, 0.7 kN/m or higher (e.g., 0.72 to 3 kN/m),
more preferably 0.75 kN/m or higher (e.g., 0.76 to 3 kN/m), further
preferably 0.8 kN/m or higher (e.g., 0.83 to 3 kN/m), still further
preferably 1.0 kN/m or higher (e.g., 1.1 to 3 kN/m), and
particularly preferably 1.2 kN/m or higher (e.g., 1.3 to 3
kN/m).
[0204] It should be noted that upon determining interlayer
adhesion, existence of cohesive failure could be generally
determined as an evidence of good bonding. In contrast, occurrence
of interfacial separation shows poor bonding in many cases.
[0205] Preferably, the circuit board is generally improved in
bonding strength in every direction. For example, with respect to a
first direction (A direction) of a circuit board sample and a
second direction (B direction) perpendicular to the first
direction, where bonding strengths of the sample are measured in
four direction by peeling from both sides, i.e., in a forward A
direction, in an adverse A direction, in a forward B direction, and
in an adverse B direction, the minimum bonding strength in the four
directions between the adherend film and the adhesive film may be
0.5 kN/m or higher (e.g., 0.5 to 3 kN/m), preferably 0.6 kN/m or
higher, more preferably 0.7 kN/m or higher, still more preferably
0.8 kN/m or higher, and particularly preferably 0.9 kN/m or
higher.
[0206] Since the circuit board according to the present invention
can employ, as an insulating material, a thermoplastic liquid
crystal polymer excellent in dielectric characteristics, the
circuit board can be used particularly suitably as a high frequency
circuit board. Examples of high frequency circuits include a
circuit for transmitting mainly (only) high frequency signals; in
addition; a circuit for a transmission line transmitting low
frequency signals, for example, a circuit for a transmission line
transmitting low frequency signals as output after converting high
frequency signals into low frequency signals, a circuit for a
transmission line supplying electronic power to drive high
frequency- corresponding parts; as well as a circuit provided with
the above circuits or transmission lines on the same plane.
EXAMPLES
[0207] Hereinafter, the present invention is described in greater
detail by examples, but the invention is not limited in any way by
the present invention to this embodiment. In the following Examples
and Comparative Examples were measured for various physical
properties by the following method.
[0208] Melting Point
[0209] Melting point of a film was determined based on the
observation of thermal behavior of the film using a differential
scanning calorimeter. A test film was heated at a rate of
20.degree. C./min to completely melt the film, and the melt was
rapidly cooled to 50.degree. C. at a rate of 50.degree. C./min.
Subsequently, the quenched material was reheated at a heating rate
of 20.degree. C./minute, and a position of an endothermic peak
appearing in the reheating process was recorded as a melting point
of the film.
[0210] Peak Areas Obtained by X-Ray Photoelectron Spectroscopy
Analysis X-Ray Photoelectron Spectroscopy Analysis
[0211] Using PHI Quantera SXM (available from ULVAC-PHI,
[0212] INCORPORATED), a sample is subjected to spectroscopic
analysis in the following condition so as to calculate a relative
intensity (%) of C--O and COO bond peaks as a ratio in percentage
of a sum of peak areas of C--O bond peak and COO bond peak based on
the total area of C1s peaks in the XPS spectral profile.
[0213] It should be noted that analysis of the unit circuit board
is carried out on the LCP film surface on which the circuit is not
formed.
[0214] X-ray excitation conditions: 100 .mu.m-25 W-15 kV Anode: Al
(aluminum)
[0215] Measurement range: 1000 .mu.m.times.1000 .mu.m
[0216] Pressure: 1.times.10.sup.-6 Pa
[0217] With no sample washing
[0218] Further, attribution of functional groups related to carbon
and oxygen was determined in accordance with the method shown
below.
[0219] Regarding C1s
[0220] C--C: 284.8 eV; C--O: 286.4 eV; C.dbd.O: 287.6 eV;
O--C.dbd.O: 288.6 eV; CO.sub.3: 290-291 eV; and ShakeUp: 291 eV
[0221] Regarding O1s
[0222] C.dbd.O: 532.0 eV; C--O: 533.1 eV
[0223] Measurement of Ultraviolet-Ray Irradiation Dose
[0224] Using an ultraviolet illuminometer (UV-M03A) available from
OAC MANUFACTURING CO., LTD., ultraviolet illumination was measured
in the width direction to obtain an average value of three
points.
[0225] Moisture Content
[0226] Karl Fischer method was employed as a measuring method of
moisture content, that is, moisture content was measured by
observing change in potential difference before and after allowing
moisture absorbed in a solvent in accordance with the principle of
the Karl Fischer titration.
[0227] (1) Device name for trace moisture measurement: VA-07, CA-07
available from Mitsubishi Chemical Analytech Co., Ltd.
[0228] (2) Heating temperature: 260.degree. C.
[0229] (3) N2 purge pressure: 150 mL/min.
[0230] (4) Measurement preparation (automatic) [0231] Purge: 1
minute [0232] Pre-heat: 2 minutes for baking a sample board [0233]
Cooling: 2 minutes for cooling the sample board
[0234] (5) Measurement [0235] Time for accumulating moisture in a
measurement titration cell, i.e., time for sending moisture with
N.sub.2: 3 minutes
[0236] (6) Sample weight: 1.0 to 1.3 g
[0237] Segment Orientation Ratio (SOR)
[0238] Using a microwave type molecular orientation meter, a liquid
crystal polymer film is inserted into a microwave resonance
waveguide tube such that a propagation direction of microwave is
perpendicular to the film surface, and electric-field strength
(microwave transmission intensity) of microwave transmitting
through the film is measured. Then, based on the measured value, m
value (referred to as refractive index) is calculated from the
following formula:
m=(Zo/.DELTA.z).times.[1-v max/vo]
[0239] Here, Zo represents a device constant, Az represents an
average thickness of an object subjected to the measurement, vmax
represents the frequency at which the maximum microwave
transmission intensity can be obtained when the frequency of the
microwave is varied, and vo represents the frequency at which the
maximum microwave transmission intensity can be obtained when the
average thickness is zero, that is, when no object is present.
[0240] Next, when the rotation angle of the object relative to the
direction of oscillation of the microwaves is 0.degree., that is,
when the direction of oscillation of the microwaves is aligned with
the direction in which molecules of the object are most oriented as
well as in which the minimum microwave transmission intensity is
exhibited, an m value obtained in such a case was represented as
m.sub.0. An m value obtained as m90 represents the value of the
refractive index when the angle of rotation of the object is
90.degree.. A segment orientation ratio SOR was calculated as
m.sub.0/m.sub.90.
[0241] Film Thickness
[0242] Thicknesses of an obtained film were measured at intervals
of 1 cm in the TD direction using a digital thickness meter
(available from Mitutoyo Corporation), and the film thickness was
determined as an average thicknesses of 10 points arbitrarily
selected from a center portion and end portions.
[0243] Heat Resistance Test (Solder Heat Resistance)
[0244] Solder float test was carried in conformity with JIS C 5012
to examine solder heat resistance of the circuit board. The solder
heat resistance was evaluated by observing a substrate sample that
was subjected to solder float test in a solder bath of 290.degree.
C. for 60 seconds whether the substrate sample had at least one
blister having an area of 100 .mu.m.times.100 .mu.m or wider by
sight or using an optical microscopy (5 magnifications or
higher).
[0245] Specifically, from a circuit board sample having a size of
30 cm square (30 cm.times.30 cm) were derived five circuit board
samples each having a size of 5 cm square (5 cm.times.5 cm) by
randomly cutting. Each of the five circuit board samples were
subjected to the solder float test, and blister occurrence was
observed by sight or using an optical microscopy (5 magnifications
or higher). Where blister was not observed in all of the five cut
samples, the originated circuit board sample was determined as
good, i.e., showing solder heat resistance. Where blister was
observed in any one of the five cut samples, the originated circuit
board sample was determined as poor.
[0246] Interlayer adhesion
[0247] A circuit board was press-cut into a thin-strip form with a
width of 10 mm to obtain a test sample. After peeling an edge of
the adhesion interface in the test sample, peel strength was
measured in ambient temperature by peeling adherend and adhesive
films from each other at a peeling angle of 90.degree. and at a
peeling rate of 5 cm per minute using "Digital Force Gauge"
available from NIDEC-SHIMPO CORPORATION to obtain an average value
of loads for a length of 5 cm. It should be noted that too-large
fluctuated values in the beginning and ending of the measurement
were not used for calculating the average.
Example 1
[0248] (1) Production of Adhesive LCP Film (Adhesive Film)
[0249] From a copolymerization product of p-hydroxybenzoic acid and
6-hydroxy-2-naphthoic acid (mole ratio: 73/27) was obtained a TLCP
film having a melting point of 280.degree. C. and a film thickness
of 50 .mu.m. The TLCP film had a moisture content of 400 ppm and an
SOR of 1.02.
[0250] (2) Production of Unit Circuit Board (Adherend Film)
[0251] From a copolymerization product of p-hydroxybenzoic acid and
6- hydroxy-2-naphthoic acid (mole ratio: 73/27) was obtained a TLCP
film having a melting point of 280.degree. C. and a film thickness
of 50 .mu.m. The TLCP film was heat-treated under nitrogen
atmosphere at 260.degree. C. for 4 hours, and at 280.degree. C. for
another 2 hours to increase a melting point into 320.degree. C. to
obtain an adherend film. Onto each surface of the film, a rolled
copper foil with a thickness of 12 .mu.M and a predetermined
surface roughness was set to be laminated using a continuous
heat-pressing machine with a pair of rolls at a roll temperature of
300.degree. C., a linear pressure of 100 kg/cm, and a line speed of
2 m/min to obtain a copper-clad laminate. The copper-clad laminate
was processed to produce a unit circuit board having a strip line
structure (the existing ratio of conductive material on the
conductor circuit surface is less than 30%). The TLCP film in the
unit circuit board had a moisture content of 400 ppm and an SOR of
1.02.
[0252] (3) Production of Multilayer Circuit Board
[0253] The adhesive LCP film 23 obtained in the process (1) was
used as a bonding sheet. As shown in the circuit board
configuration in FIGS. 3A and 3B, the adhesive LCP film 23 was
interposed between two sheets of the insulating substrates 21 and
25 to obtain a stacked material. The stacked material was placed
(set) in a vacuum heat press apparatus. It should be noted that the
insulating substrate 21 had a conductor circuit 22a a conductor
layer 22b on both surfaces, respectively, to configure a unit
circuit board; and that the insulating substrate 25 had a conductor
circuit 26a and a conductor layer 26b on both surfaces,
respectively, to configure a unit circuit board. The surfaces 23a
and 23b of the adhesive LCP film 23 covered the conductor circuits
22a and 26a, respectively.
[0254] Before set (stacked), the adhesive LCP film 23 and the
insulating substrates 21 and 25 had surface states of relative
intensities (%) each being a sum of relative peak areas of C--O and
COO bond peaks in each of the XPS spectral profiles as shown in
Table 7. Thereafter, the stacked material was subjected to
pre-heating (degassing under vacuum at a vacuum degree of 1500 Pa
or lower for 60 minutes) and then to thermo-compression bonded
under vacuum at a vacuum degree of 1300 Pa and a compression
pressure of 4 MPa at 300.degree. C. for 30 minutes to be bonded
with each other to obtain a circuit board having a configuration of
unit circuit board/bonding sheet/unit circuit board. The obtained
circuit board was evaluated in various physical properties. Table 7
shows obtained properties.
Example 2
[0255] Each of the surfaces to be adhered in the adhesive LCP film
and the unit circuit boards obtained in Example 1 was subjected to
UV-irradiation by irradiating 254 nm of ultra-violet ray at an
irradiation amount of 400 mJ/cm.sup.2 at a distance between the
light source and the surface to be irradiated of 2 cm for 1.05
minutes using a UV-irradiation machine "UV-surface Treating
Machine" available from SEN ENGENEERING CO., LTD.
[0256] Thus-obtained adhesive LCP film 23 was used as a bonding
sheet. As shown in the circuit board configuration in FIGS. 3A and
3B, the adhesive LCP film 23 was interposed between two sheets of
the insulating substrates 21 and 25 to obtain a stacked material.
The stacked material was placed in a vacuum heat press apparatus.
It should be noted that the insulating substrate 21 had a conductor
circuit 22a and a conductor layer 22b on both surfaces,
respectively, to configure a unit circuit board; and that the
insulating substrate 25 had a conductor circuit 26a and a conductor
layer 26b on both surfaces, respectively, to configure a unit
circuit board. The surfaces 23a and 23b of the adhesive LCP film 23
covered the conductor circuits 22a and 26a, respectively.
[0257] Before set (stacked), the adhesive LCP film 23 and the
insulating substrates 21 and 25 had surface states of relative
intensities (%) each being a sum of relative peak areas of C--O and
COO bond peaks in each of the XPS spectral profiles as shown in
Table 7. Thereafter, the stacked materials were subjected to
pre-heating (degassing under vacuum at a vacuum degree of 1500 Pa
or lower for 60 minutes) and then to thermo-compression bonded
under vacuum at a vacuum degree of 1300 Pa and a compression
pressure of 4 MPa at 300.degree. C. for 30 minutes to be bonded
with each other to obtain a circuit board having a configuration of
unit circuit board/bonding sheet/unit circuit board. The obtained
circuit board was evaluated in various physical properties. Table 7
shows obtained properties.
Example 3
[0258] Before being placed in a vacuum heat press apparatus, the
adhesive LCP film and the unit circuit boards obtained in Example 1
were subjected to degassing under heating so as to decrease
moisture contents of them to be 200 ppm or lower. Except for
subjecting them to the degassing, the same configuration was
adopted with Example 1. It should be noted that degassing under
heating was carried out by heating the adhesive films obtained in
Example 1 at 120.degree. C. for 60 minutes.
[0259] Thus-obtained adhesive LCP film 23 was used as a bonding
sheet. As shown in the circuit board configuration in FIGS. 3A and
3B, the adhesive LCP film 23 was interposed between two sheets of
the insulating substrates 21 and 25 to obtain a stacked material.
The stacked material was placed in a vacuum heat press apparatus.
It should be noted that the insulating substrate 21 had a conductor
circuit 22a and a conductor layer 22b on both surfaces,
respectively, to configure a unit circuit board; and that the
insulating substrate 25 had a conductor circuit 26a and a conductor
layer 26b on both surfaces, respectively, to configure a unit
circuit board. The surfaces 23a and 23b of the adhesive LCP film
covered the conductor circuits 22a and 26a, respectively.
[0260] Before set (stacked), the adhesive LCP film 23 and the
insulating substrates 21 and 25 had surface states of relative
intensities (%) each being a sum of relative peak areas of C--O and
COO bond peaks in each of the XPS spectral profiles as shown in
Table 7. Thereafter, the stacked materials were subjected to
pre-heating (degassing under vacuum at a vacuum degree of 1500 Pa
or lower for 60 minutes) and then to thermo-compression bonded
under vacuum at a vacuum degree of 1300 Pa and a compression
pressure of 4 MPa at 300.degree. C. for 30 minutes to be bonded
with each other to obtain a circuit board having a configuration of
unit circuit board/bonding sheet/unit circuit board. The obtained
circuit board was evaluated in various physical properties. Table 7
shows obtained properties.
Example 4
[0261] (1) Production of Adhesive LCP Polymer Film
[0262] From a copolymerization product of p-hydroxybenzoic acid and
6-hydroxy-2-naphthoic acid (mole ratio: 73/27) was obtained a TLCP
film having a melting point of 280.degree. C. and a film thickness
of 50 .mu.m . The TLCP film was heat-treated under nitrogen
atmosphere at 260.degree. C. for 4 hours, and at 280.degree. C. for
another 2 hours to increase a melting point into 320.degree. C. The
TLCP film had a moisture content of 400 ppm and an SOR of 1.02.
[0263] (2) Production of Multilayer Circuit Board
[0264] The adhesive LCP film 23 obtained in the above (1) was used
as a bonding sheet. As shown in the circuit board configuration in
FIGS. 3A and 3B, the adhesive LCP film 23 was interposed between
two sheets of the insulating substrates 21 and 25 to obtain a
stacked material. The stacked material was placed in a vacuum heat
press apparatus. It should be noted that the insulating substrate
21 had a conductor circuit 22a and a conductor layer 22b on both
surfaces, respectively, to configure a unit circuit board; and that
the insulating substrate 25 had a conductor circuit 26a and a
conductor layer 26b on both surfaces, respectively, to configure a
unit circuit board. The surfaces 23a and 23b of the adhesive LCP
film covered the conductor circuits 22a and 26a, respectively.
[0265] Before set (stacked), the adhesive LCP film 23 and the
insulating substrates 21 and 25 had surface states of relative
intensities (%) each being a sum of relative peak areas of C--O and
COO bond peaks in each of the XPS spectral profiles as shown in
Table 7. Thereafter, the stacked materials were subjected to
pre-heating (degassing under vacuum at a vacuum degree of 1500 Pa
or lower for 60 minutes) and then to thermo-compression bonded
under vacuum at a vacuum degree of 1300 Pa and a compression
pressure of 4 MPa at 300.degree. C. for 30 minutes to be bonded
with each other to obtain a circuit board having a configuration of
unit circuit board/bonding sheet/unit circuit board. The obtained
circuit board was evaluated in various physical properties. Table 7
shows obtained properties.
Example 5
[0266] Production of Multilayer Circuit Board
[0267] The adhesive LCP films and the unit circuit board obtained
in the above (1) were used. The insulating substrate 11 was
interposed between the adhesive films 13 as coverlays. As shown in
the circuit board configuration in FIGS. 1A and 1B, the unit
circuit board was provided with the insulating substrate 11 and the
conductor circuits 12, 12 formed on the both surfaces,
respectively, of the insulating substrate 11. The adhesive films
13a and 13b were overlaid on the conductor circuits 12, 12,
respectively, so as to be placed in a vacuum heat press
apparatus.
[0268] Before set (stacked), the adhesive LCP film 13 and the
insulating substrate 11 had surface states of relative intensities
(%) each being a sum of relative peak areas of C--O and COO bond
peaks in the XPS spectral profiles as shown in Table 7. Thereafter,
the stacked materials were subjected to pre- heating (degassing
under vacuum at a vacuum degree of 1500 Pa or lower for 60 minutes)
and then to thermo-compression bonded under vacuum at a vacuum
degree of 1300 Pa and a compression pressure of 4 MPa at
300.degree. C. for 30 minutes to be bonded with each other to
obtain a circuit board having a configuration of coverlay/unit
circuit board/coverlay. The obtained circuit board was evaluated in
various physical properties. Table 7 shows obtained properties.
Example 6
[0269] Except for omitting pre-heating process, a multilayer
circuit board was produced in the same manner as Example 1. The
obtained circuit board was evaluated in various physical
properties. Table 7 shows obtained properties.
Examples 7 to 9
[0270] Except for changing the irradiating conditions (UV wave
length, irradiation dose, distance between light source and
irradiated surface, irradiation time) of UV-rays as shown below,
UV-ray was irradiated onto each of the surfaces to be adhered in
adhesive LCP film and unit circuit boards obtained in Example 2 so
as to produce a multilayer circuit boards in the same manner as
Example 2. The obtained circuit boards were evaluated in various
physical properties. Table 7 shows obtained properties.
TABLE-US-00007 Irradiation Irradiation Irradiation UV wave amount
distance period length (nm) (kJ/m.sup.2) (cm) (min) Ex. 7 Adherend
film 254 400 2 0.8 Adhesive film 254 400 2 0.3 Ex. 8 Adherend film
254 400 2 1 Adhesive film 254 400 2 0.1 Ex. 9 Adherend film 254 400
2 1.4 Adhesive film 254 400 2 1.4
Comparative Example 1
[0271] Except for using the UV-irradiated film obtained in Example
2 as the adhesive LCP film 23, a circuit board was obtained in the
same manner with Example 1. The obtained circuit board was
evaluated in various physical properties. Table 7 shows obtained
properties.
Comparative Example 2
[0272] Except for using the UV-irradiated films obtained in Example
2 as the insulating substrates 21, 25, a circuit board was obtained
in the same manner with Example 1. The obtained circuit board was
evaluated in various physical properties. Table 7 shows obtained
properties.
Comparative Example 3
[0273] Except for using the UV-irradiated films obtained in Example
2 as the insulating substrates 21, 25, a circuit board was obtained
in the same manner with Example 6. The obtained circuit board was
evaluated in various physical properties. Table 7 shows obtained
properties.
Comparative Example 4
[0274] Except for changing the irradiating conditions (UV wave
length, irradiation dose, distance between light source and
irradiated surface, irradiation time) of UV-rays as shown below,
UV-ray was irradiated onto each of the surfaces to be adhered in
adhesive LCP film and unit circuit boards obtained in Example 2 so
as to produce a multilayer circuit boards in the same manner as
Example 2. The obtained circuit board was evaluated in various
physical properties. Table 7 shows obtained properties.
TABLE-US-00008 Irradiation Irradiation Irradiation UV wave amount
distance period length (nm) (kJ/m.sup.2) (cm) (min) Com. Adherend
film 254 400 2 0.1 Ex. 4 Adhesive film 254 400 2 1
TABLE-US-00009 TABLE 7 Adherend film Adhesive film Sum of Sum of
Circuit board relative peak relative peak Solder Inter- areas X
Melting Moisture areas Y Melting Moisture heat layer [C--O] + point
content [C--O] + point content Pre- Configu- resis- adhesion
[COO](%) (.degree. C.) (ppm) [COO](%) X + Y Y - X (.degree. C.)
(ppm) heat ration tance (kN/m) Ex. 1 19.6 320 400 19.6 39.2 0.0 280
400 Yes 20 Good 1.4 Ex. 2 29.3 320 400 29.3 58.6 0.0 280 400 Yes 20
Good 0.7 Ex. 3 19.6 320 200 19.6 39.2 0.0 280 200 Yes 20 Good 1.4
Ex. 4 19.6 320 400 19.6 39.2 0.0 320 400 Yes 20 Good 1.1 Ex. 5 19.6
320 400 19.6 39.2 0.0 280 400 Yes 10 Good 1.4 Ex. 6 19.6 320 400
19.6 39.2 0.0 280 400 No 20 Good 0.8 Ex. 7 26.7 320 400 22.2 48.9
-4.5 280 400 Yes 20 Good 0.8 Ex. 8 28.2 320 400 20.7 48.9 -7.5 280
400 Yes 20 Good 0.6 Ex. 9 30.56 320 400 30.56 61.12 0.0 280 400 Yes
20 Good 1.1 Com. Ex. 1 19.6 320 400 29.3 48.9 9.7 280 400 Yes 20
Poor 0.65 Com. Ex. 2 29.3 320 400 19.6 48.9 -9.7 280 400 Yes 20
Poor 0.3 Com. Ex. 3 29.3 320 400 19.6 48.9 -9.7 280 400 No 20 Poor
0.2 Com. Ex. 4 20.2 320 400 28.7 48.9 8.5 280 400 Yes 20 Poor
0.4
[0275] As shown in Table 7, in Examples 1 and 3 to 6, where an
appropriate combination between the relative intensity Y of the
adhesive film and the relative intensity X of the adherend film was
achieved by controlling the selection of the adhesive film and the
adherend film to have specific ranges of X+Y and Y-X, even if the
value of X+Y was less than 42, the laminated body of these films
has a satisfactory interlayer adhesion, as well as good solder
resistance. That is, these Examples reveal that where each of the
adhesive films is selected so as to have a specific relationship
with each of the adherend films, even without activation treatment,
the selected adhesive films contribute to satisfactory interlayer
adhesion as well as good solder heat resistance.
[0276] Example 5 shows that the similar effect can be obtained
where the adhesive LCP films are used as coverlays.
[0277] In Examples 2 and 7 to 9, which are subjected to UV
irradiation, where each of the adhesive films is controlled so as
to have a specific relationship of X+Y and Y-X with each of the
adherend films, the adhesive films contribute to satisfactory
interlayer adhesion as well as good solder heat resistance.
[0278] Further, some Examples reveal that the interlayer adhesion
is presumably further improved by degassing treatment of films such
as pre-heat treatment or degassing under vacuum. For example, in
comparison with Example 6 without degassing treatment, Example 1
that is subjected to pre-heat treatment and Example 3 that is
subjected to degassing under vacuum show higher interlayer
adhesion.
[0279] On the contrary, as shown in Comparative Examples 1 to 3,
where only one of the adhesive and adherend films is UV-irradiated
so as to be outside of the specific relationship of X+Y and Y-X
defined in the present invention, the obtained circuit boards have
unsatisfactory solder heat resistance. Further as shown in
Comparative Example 4, even where both the adhesive and the
adherend films were UV-irradiated, since Comparative Example 4 does
not satisfy the specific relationship of X+Y and Y-X defined in the
present invention, the obtained circuit board has unsatisfactory
solder heat resistance.
[0280] More specifically, in Comparative Examples 1 to 4, at least
one of the adhesive and adherend films satisfies that a sum of
relative peak areas of C--O and COO bond peaks is 21% or more, and
that a peak area ratio of C--O bond peak/COO bond peak is 1.5 or
less. However, the obtained circuit boards are deteriorated in
solder heat resistance. Further, Comparative Examples 2 to 4 show
significantly deteriorated interlayer adhesion.
INDUSTRIAL APPLICABILITY
[0281] The circuit board according to the present invention can be
used as substrates for various electrical and electronic products.
In particular, since the LCP film has excellent dielectric
characteristics at high frequency, the circuit board according to
the present invention can be advantageously used as a high
frequency circuit board or the like.
[0282] Although the present invention has been fully described in
connection with the preferred embodiments thereof, those skilled in
the art will readily conceive numerous changes and modifications
within the framework of obviousness upon the reading of the
specification herein presented of the present invention.
Accordingly, such changes and modifications are to be construed as
included therein.
* * * * *