U.S. patent application number 09/284512 was filed with the patent office on 2001-07-19 for glass fiber of low permittivity.
Invention is credited to MORI, MASAHIRO, TAMURA, SHINICHI.
Application Number | 20010008864 09/284512 |
Document ID | / |
Family ID | 17530231 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008864 |
Kind Code |
A1 |
TAMURA, SHINICHI ; et
al. |
July 19, 2001 |
GLASS FIBER OF LOW PERMITTIVITY
Abstract
A low-dielectric-constant glass fiber having a glass composition
comprising, by % by weight, 45 to 60% of SiO.sub.2, 8 to 20% of
Al.sub.2O.sub.3, 15 to 30% of B.sub.2O.sub.3, 0 to 5% of MgO, 5%,
exclusive of 5%, to 12% of CaO, 0 to 1.0% of
Li.sub.2O+Na.sub.2O+K.sub.2O- , 0.5 to 5% of TiO.sub.2 and 0 to 2%
of F.sub.2 is suitable for use for reinforcing a high-density
printed wiring board required to have a low dielectric tangent and
its peripheral members.
Inventors: |
TAMURA, SHINICHI;
(FUKUSHIMA-SHI, JP) ; MORI, MASAHIRO;
(FUKUSHIMA-SHI, JP) |
Correspondence
Address: |
NIXON & VANDERHYE
1100 NORTH GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
222014714
|
Family ID: |
17530231 |
Appl. No.: |
09/284512 |
Filed: |
April 14, 1999 |
PCT Filed: |
October 8, 1997 |
PCT NO: |
PCT/JP97/03609 |
Current U.S.
Class: |
501/37 |
Current CPC
Class: |
C03C 13/00 20130101;
H05K 1/0366 20130101 |
Class at
Publication: |
501/37 |
International
Class: |
C03C 013/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 16, 1996 |
JP |
H8.273617 |
Claims
1. A low-dielectric-constant glass fiber having a glass composition
comprising, by % by weight, 45 to 60% of SiO.sub.2, 8 to 20% of
Al.sub.2O.sub.3, 15 to 30% of B.sub.2O.sub.3, 0 to 5% of MgO, 5%,
exclusive of 5%, to 12% of CaO, 0 to 1.0% of
Li.sub.2O+Na.sub.2O+K.sub.2O- , 0.5 to 5% of TiO.sub.2 and 0 to 2%
of F.sub.2.
2. The low-dielectric-constant glass fiber of claim 1, which has a
glass composition comprising, by % by weight, 50 to 57% of
SiO.sub.2, 10 to 18% of Al.sub.2O.sub.3, 18 to 25% of
B.sub.2O.sub.3, 0 to 5% of MgO, 5%, exclusive of 5%, to 10% of CaO,
0 to 0.3% of Li.sub.2O, 0 to 0.3% of Na.sub.2O, 0 to 0.5% of
K.sub.2O, 0.5 to 5% of TiO.sub.2, and 0 to 2% of F.sub.2, the
content of MgO+CaO exceeding 5% and being 12% or less, the content
of Li.sub.2O+Na.sub.2O+K.sub.2O equaling 0 to 0.6%.
3. The low-dielectric-constant glass fiber of claim 1, which
further contains at least one member selected from ZnO, SrO,
Fe.sub.2O.sub.3, Cr.sub.2O.sub.3, As.sub.2O.sub.3, Sb.sub.2O.sub.3,
P.sub.2O.sub.5, ZrO.sub.2, Cl.sub.2, SO.sub.3 or MoO.sub.2, in such
an amount that glass properties are not impaired.
4. The low-dielectric-constant glass fiber of claim 1, which has a
dielectric constant of 5 or less, a dielectric tangent of
10.times.10.sup.-4 or less and a spinning temperature of
1,350.degree. C. or less and exhibits an alkali elution amount of
less than 0.1% by weight.
5. The low-dielectric-constant glass fiber of claim 1, which is for
use as a glass fiber for a printed wiring board.
Description
TECHNICAL FIELD
[0001] The present invention relates to a low-dielectric-constant
glass fiber, particularly to a low-dielectric-constant glass fiber
having a low dielectric tangent suitable for use for reinforcing a
printed wiring board required to have a low dielectric tangent and
its peripheral plastic members.
TECHNICAL BACKGROUND
[0002] With the age of highly computerized societies in recent
years, communication machines and equipment for satellite
broadcasting, mobile phones, etc., tend to be digitized, and signal
processing tends to be quicker. These use printed wiring boards
constituted of composite materials composed of materials such as a
reinforcing material, a resin, a modifier, a filler, and the like.
Further, glass fibers are widely used as a reinforcing material for
their peripheral plastic members. Conventionally, E glass is known
as a commercially produced glass fiber of this kind.
[0003] When an alternate current is flowed in glass, generally, the
glass absorbs energy with regard to the alternate current and
absorbs it as heat. The dielectric loss energy to be absorbed is in
proportion to a dielectric constant and a dielectric tangent which
are determined by the components and the structure of the glass,
and is shown by the following expression.
W kfv.sup.2.times..epsilon. tan .epsilon.
[0004] in which W is a dielectric loss energy, k is a constant, f
is a frequency, v.sup.2 is a potential gradient, .epsilon. is a
dielectric constant, and tan6 is a dielectric tangent.
[0005] The above expression shows that with an increase in the
dielectric constant and the dielectric tangent, or with an increase
in the frequency, the dielectric loss increases.
[0006] E glass, for example, has a dielectric constant of 6.7 and a
dielectric tangent of 12.times.10.sup.-4 at a frequency of 1 MHz at
room temperature, and a printed wiring board formed of E glass is
insufficient for complying with demands of a higher density and a
higher processing speed. There are therefore desired glasses which
have a lower dielectric constant and a lower dielectric tangent
than the E glass. Among them is a glass called D glass. D glass is
for example, a glass having a composition containing 75.3% of
SiO.sub.2, 20.5% of B.sub.2O.sub.3, 0.6% of CaO, 0.4% of MgO, 0.6%
of Li.sub.2O, 1.1% of Na.sub.2O and 1.5% of K.sub.2O. For example,
it has a dielectric constant of 4.3 and a dielectric tangent of
10.times.10.sup.-4 at a frequency of 1 MHz at room temperature.
[0007] However, D glass has the following defects. Since it has
poor meltability and is liable to cause striae and foams, a glass
fiber frequently breaks during its spinning step, and it is poor in
productivity and workability. Further, since it has a very high
spinning temperature, the lifetime of a furnace is decreased.
Moreover, there is another problem that since D glass has poor
water resistance, and since it has poor adhesion to a resin, it is
liable to peel from a resin in a printed wiring board so that no
high reliability can be obtained when it is used for a printed
wiring board.
[0008] JP-A-6-219780 discloses a low-dielectric-constant glass
comprising 50.0 to 65.0% of SiO.sub.2, 10.0 to 18.0% of
Al.sub.2O.sub.3, 11.0 to 25.0% of B.sub.2O.sub.3, 6.0 to 14.0% of
MgO, 1.0 to 10.0% of CaO and 0 to 10 of ZnO, MgO+CaO+ZnO being 10.5
to 15%. The above glass is intended to decrease a spinning
temperature so as to improve productivity by particularly
incorporating at least 6% of MgO and adjusting MgO+CaO+ZnO to at
least 10.5%. Since, however, MgO, a component which is highly
liable to undergo phase separation and give a high dielectric
tangent, is incorporated in an amount of 6% or more, no sufficient
water resistance can be obtained, and the dielectric tangent of the
glass is relatively high.
[0009] JP-A-7-10598 discloses a glass having a composition
containing 50.0 to 65.0% of SiO.sub.2, 10.0 to 18% of
Al.sub.2O.sub.3, 11.0 to 25.0% of B.sub.2O.sub.3, 0 to 10.0% of
CaO, 0 to 10.0% of MgO, 1.0 to 15.0% of the CaO+the MgO, 0 to 10.0%
of ZnO, 0 to 10.0% of SrO and 1 to 10.0% of BaO. Since, however,
the above glass contains, as an essential component, BaO which is a
component to increase the dielectric constant, it is difficult to
obtain a sufficiently low dielectric constant. For obtaining a low
dielectric constant, it is inevitable to decrease the BaO amount,
and in this case, there is a problem that the viscosity of the
glass increases so that the spinning workability is poor. Further,
there is another problem that since BaO corrodes a furnace material
to a great extent, the lifetime of the furnace is decreased.
[0010] The present Applicant has already proposed, by Japanese
Patent Application No. 7-137688, a glass comprising 50 to 60% of
SiO.sub.2, 10 to 20% of Al.sub.2O.sub.3, 20 to 30% of
B.sub.2O.sub.3, 0 to 5% of CaO, 0 to 4% of MgO,
Li.sub.2O+Na.sub.2O+K.sub.2O being 0 to 0.5%, and 0.5 to 5% of
TiO.sub.2. The above glass retains a low dielectric constant and a
low dielectric tangent and at the same time shows excellent
properties during a spinning step with regard to workability and
productivity. However, it still has some slight difficulty in
workability and productivity.
DISCLOSURE OF THE INVENTION
[0011] The present invention has been made in view of the above
circumstances, and an object of the present invention is to provide
a glass which has properties of a low dielectric constant and a low
dielectric tangent, which is excellent in productivity and
workability and which is also excellent in water resistance.
[0012] The present inventors have made studies for achieving the
above object, and as a result, it has been found that a glass fiber
having a low dielectric constant and a low dielectric tangent can
be obtained by allowing a composition for the glass fiber to
particularly contain 60% or less of SiO.sub.2, 0.5 to 5% of
TiO.sub.2 and 5%, exclusive of 5%, to 12% of CaO to improve the
meltability of the glass and adjusting Li.sub.2O+Na.sub.2O+K.sub.2O
to 1.0% or less.
[0013] The gist of the present invention is therefore a
low-dielectric-constant glass fiber having a glass composition
comprising, by % by weight, 45 to 60% of SiO.sub.2, 8 to 20% of
Al.sub.2O.sub.3, 15 to 30% of B.sub.2O.sub.3, 0 to 5% of MgO, 5%,
exclusive of 5%, to 15% of CaO, 0 to 1.0% of
Li.sub.2O+Na.sub.2O+K.sub.2O- , 0.5 to 5% of TiO.sub.2 and 0 to 2%
of F.sub.2.
BEST MODES FOR PRACTICING THE INVENTION
[0014] In the present invention, the reason for the limitation of
the composition of the glass fiber is as follows.
[0015] SiO.sub.2 is a component to form a glass network together
with Al.sub.2O.sub.3 and B.sub.2O.sub.3. When the content of
SiO.sub.2 is less than 45%, not only the glass fiber has too large
a dielectric constant, but it has low water resistance and low acid
resistance, so that the glass fiber and a printed wiring board
using it as a reinforcing material are deteriorated. When the above
content exceeds 60%, the viscosity is too high, and it is sometimes
difficult to form a fiber during spinning. The content of SiO.sub.2
is therefore limited to 45 to 60%, and it is preferably 50 to 57%,
more preferably 51 to 56%.
[0016] Al.sub.2O.sub.3 is liable to undergo phase separation when
its content is less than 8%, and the glass is therefore downgraded
in water resistance. When the content thereof exceeds 20%, the
liquidus temperature of the glass increases to cause poor
spinnability. The content of Al.sub.2O.sub.3 is therefore limited
to 8 to 20%, and it is preferably 10 to 18%, more preferably 11 to
14%.
[0017] B.sub.2O.sub.3 is a component which is used as a flux to
decrease a viscosity and ease melting. When the content thereof is
less than 15%, however, the dielectric constant and the dielectric
tangent of the fiber are too large. When it exceeds 30%, a
volatilization amount during melting increases so that no
homogeneous glass can be obtained, and further, the glass is too
poor in water resistance. The content of B.sub.2O.sub.3 is
therefore limited to 15 to 30%, and it is preferably 18 to 25%,
more preferably 20 to 24%.
[0018] MgO is a component which is used as a flux to decrease a
viscosity and ease melting. When the content of MgO exceeds 5%,
however, phase separability is intensified so that the water
resistance decreases, and further, the dielectric constant and the
dielectric tangent are too large. The content of MgO is therefore
limited to 0 to 5%, and it is preferably 0 to 4%.
[0019] Like MgO, CaO is a component which is used as a flux to
decrease a viscosity and ease melting, and it is also a component
which inhibits the conversion of B.sub.2O.sub.3 to H.sub.3BO.sub.3
so that it improves the glass in water resistance. The content of
CaO is limited to over 5% and is limited to 12% or less. The reason
for excluding its content of 5% or less is to avoid the overlapping
of the above content with the content of CaO in the glass fiber
described in JP-A-7-137688 which is a prior application filed by
the present Applicant. The reason for limiting the upper limit
thereof to 12% is that when the content thereof exceeds 12%, the
dielectric constant and the dielectric tangent are too large. The
content of CaO preferably exceeds 5% and is 10% or less, more
preferably 6 to 9%.
[0020] The total content of MgO and CaO preferably exceeds 5% and
is 12% or less. The reason why the above total content is
preferably 12% or less is that when it exceeds 12%, the dielectric
constant and the dielectric tangent are too large in some cases.
The above total content more preferably exceeds 5% and is 10% or
less.
[0021] Li.sub.2O, Na.sub.2O and K.sub.2O are all used as a flux.
When the total content of Li.sub.2O, Na.sub.2O and K.sub.2O exceeds
1.0%, not only the dielectric constant is too high, but the water
resistance is poor. The total content of
Li.sub.2O+Na.sub.2O+K.sub.2O is therefore limited to 0 to 1.0%, and
it is preferably 0 to 0.6%, more preferably 0.2 to 0.5%.
[0022] When the content of each of Li.sub.2O and Na.sub.2O exceeds
0.3%, or when the content of K.sub.2O exceeds 0.5%, the dielectric
constant is too high in some cases. Therefore, preferably, the
content of each of Li.sub.2O and Na.sub.2O is 0 to 0.3%, and the
content of K.sub.2O is 0 to 0.5%. More preferably, the content of
Li.sub.2O is 0 to 0.2%, the content of Na.sub.2O is 0.1 to 0.2%,
and the content of K.sub.2O is 0 to 0.2%.
[0023] TiO.sub.2 is effective for decreasing the dielectric tangent
and decreasing the viscosity, and further, it has a remarkably
excellent effect on the inhibition of separation of a melt during
initial melting, to decrease scum which occurs on a furnace
surface. When the content thereof is less than 0.5%, these effects
are small. When it exceeds 5%, it is liable to cause phase
separation, which results in poor chemical durability. The content
of TiO.sub.2 is therefore limited to 0.5 to 5%, and it is
preferably 1 to 4%, more preferably 1 to 3%.
[0024] In the glass composition of the present invention, F.sub.2
not only works, as a flux, to decrease the viscosity of the glass,
but also decreases the dielectric constant and, particularly, the
dielectric tangent. When the content of F.sub.2 exceeds 2%, the
phase separability is intensified, and at the same, the heat
resistance is poor in some cases. The content of F.sub.2 is
therefore limited to 0 to 2%. It is preferably 0.01 to 1.8%, more
preferably 0.2 to 1.5%.
[0025] Besides the above component, the glass composition of the
present invention may contain ZnO, SrO, Fe.sub.2O.sub.3,
Cr.sub.2O.sub.3, As.sub.2O.sub.3, Sb.sub.2O.sub.3, P.sub.2O.sub.51
ZrO.sub.2, Cl.sub.2, SO.sub.3, MoO.sub.2, etc., up to 3% so long as
the properties of the glass are not impaired.
[0026] As far as preferred physical properties of the
low-dielectric-constant glass fiber of the present invention are
concerned, the low-dielectric-constant glass fiber has a dielectric
constant of 5 or less, a dielectric tangent of 10.times.10.sup.-4
or less, a spinning temperature of 1,330.degree. C. or lower and an
alkali elution amount of 0.1% by weight or less.
[0027] The low-dielectric-constant glass fiber of the present
invention preferably has a glass composition comprising, by % by
weight, 50 to 57% of SiO.sub.2, 10 to 18% of Al.sub.2O.sub.3, 18 to
25% of B.sub.2O.sub.3, 0 to 5% of MgO, 5%, exclusive of 5%, to 10%
of CaO, 0 to 0.3% of Li.sub.2O, 0 to 0.3% of Na.sub.2O, 0 to 0.5%
of K.sub.2O, and 0.5 to 5% of TiO.sub.2, the content of MgO+CaO
exceeding 5% and being 12% or less, the content of
Li.sub.2O+Na.sub.2O+K.sub.2O equaling 0 to 0.6%.
[0028] The glass fiber of the present invention is produced
according to production techniques of known glasses such as E
glass, C glass and D glass.
[0029] The glass fiber of the present invention has a low
dielectric constant and a low dielectric tangent and is suitable as
a glass fiber for a printed wiring board, particularly for
reinforcing a printed wiring board for a high-density circuit.
Further, since it has excellent properties with regard to
productivity, water resistance and low thermal expansion
properties, it can stably give a quality-stabilized glass fiber
particularly for reinforcing a printed wiring board for a
high-density circuit.
[0030] Particularly, a printed wiring board using a fabric of the
glass fiber of the present invention has characteristics concerning
drillability that positions of holes are not easily deviated and
that the degree of wearing of a drill is low, and highly reliable
printed wiring boards can be stably produced.
[0031] Further, substrates formed of the glass fiber of the present
invention such as a fabric, a non-woven fabric, a textile, a
chopped strand, a roving, a glass powder and a mat, and composite
materials (e.g., a sheet molding compound, a bulk molding compound
and a prepreg) formed of mixtures of these substrates with various
thermosetting resins can be used as substrates for various resin
reinforcements for communication machines and equipment and their
peripheral members by utilizing the low dielectric constant and the
low dielectric tangent thereof.
[0032] The low-dielectric-constant glass fiber of the present
invention will be explained in detail on the basis of Examples.
EXAMPLES 1-6
[0033] A batch prepared to have a glass composition of a sample
shown in Table 1 was placed in a platinum crucible and melted in an
electric furnace with stirring under conditions of 1,500 to
1,550.degree. C. and 8 hours. Then, the resultant molten glass was
cast onto a carbon plate to obtain a glass cullet. The glass cullet
was charged into a glass fiber production furnace and then melted
at 1,300 to 1,400.degree. C., and the molten glass was spun into a
fiber to show that the voltatilization of a large amount of
B.sub.2O.sub.3, which is caused in spinning of D glass, was not
observed and that the fiber was spun without any trouble.
[0034] Separately, the glass cullet was melted in the form of a
plate and gradually cooled and there was obtained a sample having a
diameter of 45 mm and a thickness of 2 mm and both surfaces of
which were optically polished. The sample was measured for a
dielectric constant and a dielectric tangent at a frequency of 1
MHz at room temperature with a precision LCR meter (supplied by
Hewlett-Packard) as a measuring device. Further, the sample was
measured for a temperature (.degree. C.) as a spinning temperature
found when the glass had a viscosity .eta. (poise) of 10.sup.3.
Furthermore, for water resistance, the sample was measured for a
weight (%) of an alkali component which was eluted from the glass
fiber obtained by the spinning, according to the alkali elution
test method provided by JIS R 3502. Table 1 shows these measurement
results.
1 TABLE 1 Comparative Example D E Example glass glass 1 2 3 4 5 6
SiO.sub.2 75.3 54.7 51.5 53.5 54.2 55.2 55.7 52.4 Al.sub.2O.sub.3
0.0 14.3 13.6 13.6 11.8 13.8 11.8 13.8 B.sub.2O.sub.3 20.5 6.3 22.0
22.0 24.0 20.0 23.0 21.0 MgO 0.4 0.6 2.4 2.4 1.0 2.0 2.0 3.0 GaO
0.6 22.7 6.7 6.7 7.0 7.0 5.7 6.0 MgO + CaO 1.0 23.3 9.1 9.1 8.0 9.0
7.7 9.0 Li.sub.2O 0.6 0.0 0.15 0.15 0.15 0.10 0.15 0.10 Na.sub.2O
1.1 0.3 0.15 0.15 0.15 0.20 0.15 0.10 K.sub.2O 1.5 0.1 0.00 0.00
0.20 0.00 0.00 0.10 Li.sub.2O + Na.sub.2O + 3.2 0.4 0.30 0.30 0.50
0.30 0.30 0.30 K.sub.2O TiO.sub.2 0.0 0.2 3.0 1.0 1.0 1.0 1.0 3.0
F.sub.2 0.0 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Dielectric 4.30 6.70 4.75
4.70 4.60 4.70 4.50 4.70 constant Dielectric 10.0 12.0 8.2 8.4 8.5
9.0 7.7 8.6 tangent (.times. 10.sup.-4) Spinning 1,410 1,200 1,250
1,292 1,320 1,315 1,347 1,270 temperature (.degree. C.) Alkali 0.30
0.01 0.04 0.05 0.04 0.04 0.02 0.03 elution amount (wt %)
[0035] As shown in Table 1, the glass fibers of Examples had
dielectric constants of less than 5.0 or less and dielectric
tangents of 10.times.10.sup.-4 or less, and all of these values are
smaller than that of E glass and are smaller than, or almost
equivalent to, that of D glass.
[0036] Further, as shown in Table 1, D glass showed an alkali
elution amount of 0.30%, while all the glass fibers of Examples
showed alkali elution amounts of less than 0.1% and are excellent
in water resistance.
[0037] Furthermore, the glass fibers of Examples had spinning
temperatures which were lower than that of D glass or were not
higher than 1,350.degree. C., said spinning temperature being a
temperature at which a viscosity .mu. (poise) of a fiber is log
.mu.=3.0 which is an index for spinning. And boric anhydride
(B.sub.2O.sub.3) is not easily volatilzied, so that they have
excellent productivity.
[0038] Industrial Utility
[0039] The glass fiber of the present invention has a low
dielectric constant and a low dielectric tangent and is excellent
as a glass fiber for printed wiring boards, particularly for
reinforcing printed wiring boards for high-density circuits.
Further, it has excellent properties with regard to productivity,
water resistance and low thermal expansion, so that the present
invention can stably provide a quality-stabilized glass fiber
particularly for reinforcing printed wiring boards for high-density
circuits.
* * * * *