EP1390313A1

EP1390313A1 - Reinforcing glass yarns with low dielectric constants

Info

Publication number: EP1390313A1
Application number: EP02730379A
Authority: EP
Inventors: Emmanuel Lecomte; Sophie Creux
Original assignee: Saint Gobain Vetrotex France SA
Current assignee: Saint Gobain Adfors SAS
Priority date: 2001-05-23
Filing date: 2002-05-02
Publication date: 2004-02-25
Also published as: US20040175557A1; RU2003136776A; MXPA03010595A; FR2825084A1; WO2002094728A1; JP2004525066A; FR2825084B1; CN1511120A

Abstract

The invention concerns a glass yarn whereof the composition comprises the following constituents in the limits defined, expressed in weight percentages: SiO2 50 to 60 %, preferably SiO2 >/= 52 % and/or SiO2 </= 57 %; Al2O3 10 to 19 %, preferably Al2O3 >/= 13 % and/or Al2O3 </= 17 %; B2O3 16 to 25 %; P2O50.5 to 4 %; Na2O </= 1.5 %, preferably Na2O </= 0.8 %; K2O </= 1.5 %, preferably K2O </= 0.8 %; R2O </= 2 %, preferably R2O </= 1 %; CaO </= 10 %; MgO </= 10 %; F </= 0 to 2 %; RO 4 to 15 %, preferably RO >/= 6 % and/or RO </= 10 % ; miscellaneous </= 3 % ; wherein R2O = Na2O + K2O + Li2O and RO = CaO + MgO. The dielectric properties of said glass compositions are particularly advantageous.

Description

REINFORCING GLASS WIRES

WITH LOW DIELECTRIC CONSTANTS

The present invention relates to "reinforcing" glass yarns (or "fibers"), that is to say usable for reinforcing organic and / or inorganic materials and usable as textile yarns, these yarns being capable of being obtained by the process which consists in mechanically stretching molten glass streams flowing from orifices arranged at the base of a die generally heated by the Joule effect.

The present invention relates more specifically to glass strands with low dielectric constants having a particularly advantageous new composition. There is indeed an increasing demand for glass wires whose permittivity and dielectric losses are low, used mainly in the form of fabrics, to reinforce printed circuit supports. The latter consist mainly of a reinforcement, in particular glass strands, and of a resin on which there are various electrical and / or electronic components.

With on the one hand the increase in the processing speeds of electrical and / or electronic signals which implement signals of increasingly higher frequencies, and on the other hand the miniaturization of the components which makes it possible to increase their density on a support, the dielectric properties of this support become decisive. If these properties do not perform as expected, risks of overheating and / or distortion of the signals may appear.

The polymers traditionally used for printed circuit boards are essentially made of epoxy resin. Polymers with better dielectric properties are known today, in particular polyimide resins, cyanate ethers, polyester, or even PTFE, the dielectric properties of which are satisfactory.

The improvement of the dielectric properties of a printed circuit board must therefore essentially relate to the improvement of the properties of the reinforcement, wires of The improvement of the dielectric properties of a printed circuit board must therefore essentially relate to the improvement of the properties of the reinforcement, glass strands in the context of the present invention, which generally occupy approximately

60% of the volume. A glass subjected to an alternating current transforms part of it into electrical energy dissipated in the material. This electrical energy is known as dielectric losses. The dielectric losses are proportional to the permittivity and to the tangent of the angle of loss (tan δ) which depend on the composition of the glass for a given frequency. Dielectric losses are expressed in the form (see for example: J.C. Dubois, in "" Engineering Techniques ", treated" Electronics ", chapter E 1850:" dielectric properties of polymers ").

W = k.fV.ε.tan δ where: W: is the electrical energy dissipated in the glass or dielectric losses, k: a constant, f: the frequency, v: a potential gradient, ε: the permittivity and tan δ: the tangent of the dielectric loss angle or dielectric dissipation factor.

We usually write ε. tan δ = ε ", if tan δ <0.1

It is clear from this formula that the more the frequency increases, or the more ε and / or tan δ increases, the greater the dielectric losses become.

In the following text, we name "dielectric properties" the couple

(ε, ε "). In order to minimize the distortions of a signal, we want both ε and ε" to be as low as possible.

It is therefore important to obtain glass compositions which can be fiberized to form continuous reinforcing wires, the dielectric properties of which are compatible with the requirements of new printed circuits.

More precisely there is a trend towards an increase in frequencies

^" of use of the components, with frequency domains of the order of GHz

(Giga Herz), in particular 0.9 and 1.8 GHz for telephony. It is therefore very important to study the behavior of glass strands in this frequency range and to optimize their composition in order to limit the dielectric losses, in particular for this field of application.

It should be noted that the previous studies published in this field deal with the dielectric properties of glasses in a frequency range of the order of MHz (Mega Herz).

It is therefore an objective of the invention to propose new glass compositions for forming reinforcing wires whose dielectric properties are of the same order of magnitude as the dielectric properties of known glasses in the MHz range and which simultaneously exhibit improved dielectric properties in the GHz range, while exhibiting satisfactory fiberizing properties for obtaining reinforcing wires under economical conditions.

In addition, it is desirable that the glass strands in question have good hydrolytic resistance properties.

In the following of the invention, we define:

→ - for the dielectric properties:

- "MHz range" as being a frequency range in which the characterizations of the dielectric properties of the glasses are carried out, in particular at 1 MHz

- "GHz range" as being a frequency range in which the characterizations of the dielectric properties of the glasses are carried out, in particular at 10 GHz

- it is usually considered that the dielectric properties are satisfactory if ε "is less than 50 x 10 ^{" 4} for measurements at 1 MHz and at

100 x 10 ^"4 for measurements at 10 GHz.

In addition, it is desirable that the value of ε is low, preferably less than 6, or even less than or equal to 5.

→ - the fiber-drawing properties which are in particular determined by: - the temperature corresponding to a viscosity equal to 10 ³ Poises

(deciPascal second), noted "T (log η = 3)", which gives a valuable indication of the temperature around which fiberizing is generally carried out, in particular from platinum dies; - the "liquidus temperature", noted "T | _iqU idus", which corresponds to the temperature where the growth rate of the most refractory crystal is zero. The liquidus temperature gives the upper limit of the temperature zone where the glass may tend to devitrify. We consider that it is possible to fiberize the glass under economic conditions if T (log η = 3) is less than or equal to 1350 ° C and if T | _iq is more than 100 ° C, preferably more than 300 ° C lower than T (log η = 3). The greater this difference between T (log η = 3) and Tκ _q , the more the fiber drawing is likely to take place without incident, and the more the risks of fiber breakage are minimized. → - hydrolytic resistance means the ability of a glass to dissolve by leaching.

This property is determined by measuring the weight loss of finely ground glass powders (between 360 and 400 μm) after staying in water maintained at the boiling point for five hours (10 g of glass in 100 ml of water). After rapid cooling, the solution is filtered and part of the filtrate is weighed after evaporation. The quantity of glass extracted ("leached" glass; in mg) is thus determined per gram of glass tested, which is denoted "DGG". The lower the DGG value, the more resistant the glass is to hydrolysis. A glass is considered to have good hydrolytic resistance if the value of DGG is less than 25, and excellent if the value is less than 10.

The most commonly used reinforcing glass strands are thus the strands formed from glass which derive from the eutectic at 1170 ° C. of the ternary diagram SiO ₂ -AI ₂ θ3-CaO, in particular the strands designated under the name of strands glass E, the archetype of which is described in patents US-A-2,334,981 and US-A-2,571,074. The strands of glass E have a composition essentially based on silica, alumina, lime and boric anhydride. Boric anhydride, present at levels ranging in practice from 5 to 13% by weight in the glass compositions qualified "glass E", replaces part of the silica. Glass strands E are further characterized by a limited content of alkaline oxides (essentially Na ₂ O and / or KO). Their dielectric properties are insufficient in view of the new requirements for printed circuit supports.

Another family of glass strands is known and obtained from compositions very rich in silica and boron. The glasses of this family, known under the name "glasses D" comprise approximately 75% of SiO ₂ , 20% of B ₂ O ₃ , 3% alkali. These glasses are particularly interesting for their dielectric properties, but they are very difficult to fiberize (T (log η = 3)> 1400 ° C) and therefore particularly expensive.

New families of compositions have recently been proposed which make it possible to obtain advantageous dielectric properties and relatively economical fiberizing conditions. These compositions are in particular described in applications WO 99/39363 and WO 99/52833.

These compositions, although very interesting by their dielectric properties measured in the MHz range, exhibit high dielectric losses in the GHz range, as shown by the results reported in Table I.

The glass strands according to the invention are obtained from a composition essentially comprising the following constituents, within the limits defined below, expressed in percentages by weight: SiO ₂ 50 to 60%

AI ₂ O ₃ 10 to 19%

B ₂ O ₃ 16 to 25%

Na ₂ O less than or equal to 1.5% K ₂ O less than or equal to 1.5%

R ₂ O (Na ₂ O + K ₂ O + Li ₂ O) less than or equal to 2%

CaO less than or equal to 10%

MgO less than or equal to 10%

RO (CaO + MgO) 4 to 15% F 0 to 2%

Miscellaneous less than or equal to 3%

The invention therefore proposes a new family of compositions selected to obtain good dielectric properties in the MHz range. Surprisingly, it is noted that the compositions according to the invention also have good dielectric properties in the GHz range. The compositions according to the invention make it possible to obtain satisfactory and advantageous fiberizing properties, making it possible to carry out economical fiberizing, in particular by virtue of T (log η = 3) <1350 ° C.

Remarkably, the compositions according to the invention have a very low liquidus temperature, in particular less than or equal to 1000 ° C. This results in a substantial reduction in the risks of devitrification during drawing in cold zones of the drawing crucible and in the channels leading the glass from the furnace to the drawing crucibles.

In addition, the compositions according to the invention exhibit good hydrolytic resistance, with in particular DGG values of less than 10.

Silica is one of the oxides which forms the network of glasses according to the invention and plays an essential role for their stability.

The silica content, SiO ₂ , of the selected compositions is between 50 and 60%, in particular greater than 52%, and / or in particular less than or equal to 57%.

Alumina also constitutes a trainer of the network of glasses according to the invention and plays a very important role with regard to the hydrolytic resistance of these glasses. Within the limits defined according to the invention, the decrease in the percentage of this oxide below 10% results in a significant increase in the hydrolytic attack of the glass while too large an increase in the percentage of this oxide entails risks of devitrification and an increase in viscosity.

The level of alumina, Al ₂ 0 _{3 l} of the selected compositions is between 10 and 19%, in particular greater than or equal to 13% and / or in particular less than or equal to 17%.

The level of lime, CaO, of the selected compositions is less than or equal to 10%, in particular less than or equal to 8%, or even even less than or equal to 6% and / or preferably greater than or equal to 2%, even even greater or equal to 4%. The level of magnesia, MgO, of the selected compositions is less than or equal to 10%, in particular less than or equal to 8%, or even even less than or equal to 6% and / or preferably greater than or equal to 2%.

The addition of phosphorus, expressed in the form P ₂ O ₅ , appears to be an essential point of the invention. The P ₂ O ₅ is between 0.5 and 4%, preferably greater than or equal to 1% and / or preferably less than or equal to 3%, or even less than or equal to 2%. This oxide appears to play a very important role on the dielectric properties, in particular in the range of the GHz as the results presented later prove it. The limits defined in alkaline earth oxides, lime and magnesia, make it possible to adjust the viscosity and control the devitrification of the glasses according to the invention. Good fiberizing ability is obtained by choosing the sum of these alkaline earth oxides between 4 and 15%, preferably greater than or equal to 6% and / or preferably less than or equal to 10%. In addition CaO appears to have a beneficial contribution on hydrolytic resistance.

Alkalis, in particular sodium hydroxide, Na ₂ O, and potassium hydroxide, K ₂ O, can be introduced into the compositions of the glass strands according to the invention in order to limit devitrification and possibly reduce the viscosity of the glass. The content of alkaline oxides Na2θ + K ₂ O + Li ₂ O must however remain less than or equal to 2% to avoid deterioration of the dielectric properties and to avoid a penalizing decrease in the hydrolytic resistance of the glass. The level of alkalis is generally greater than 0.1%, due to the presence of impurities contained in the raw materials carrying other constituents and it is preferably less than or equal to 1%, or even 0.5%, or even 0.3%. The composition may contain a single alkali metal oxide (from Na ₂ O, K ₂ O and LÎ ₂ O) or may contain a combination of at least two alkali metal oxides, the content of each alkali being less than or equal to 1.5%, preferably less than or equal to 0.8%.

The boron content is between 16 and 25%, preferably greater than or equal to 18% and / or preferably less than or equal to 22%, or even less than or equal to 20%. According to a preferred version of the invention, it is desired to limit this oxide to moderate contents compared to those of glass D on the one hand so as not to degrade the hydrolytic resistance and on the other hand because the price of the raw materials carrying boron is high. Boron can be introduced in a moderate amount by the incorporation, as a raw material, of waste glass fibers comprising boron, for example waste glass fibers E.

Fluorine, F ₂ , can be added in small amounts to improve the melting of the glass, in particular by 0.5 to 2%, or be present in the state of impurity, in particular from 0.1 to 0.5%. The possible contents of ΗO ₂ , and / or Fe ₂ θ ₃ are rather to be considered as contents of impurities, frequently encountered in this family of compositions. TiO ₂ can reach contents of between 2 and 3%, but is preferably less than 2%, or even less than 1%. In the rest of the text, any percentage of a constituent of the composition must be understood as a weight percentage, and the compositions according to the invention can contain up to 2 or 3% of compounds to be considered as non-analyzed impurities, such as this is known in this kind of composition. The invention also relates to composites formed from glass strands and organic material in which the reinforcement is provided at least by the glass strands of compositions defined above.

Preferably, such glass strands are used for the manufacture of printed circuit support. The invention also relates to a process for manufacturing glass strands of compositions defined above according to which a multiplicity of molten glass strands is drawn, flowing from a multiplicity of orifices arranged at the base of one or more dies, in the form of one or more layers of continuous filaments, then the filaments are gathered into one or more threads which are collected on a moving support.

Preferably, the molten glass supplying the orifices of the die (s) has the following composition, expressed in percentages by weight:

SiO ₂ 50 to 60%, preferably SiO ₂ > 52% and / or SiO ₂ <57%

AI2O3 10 to 19%, preferably AI ₂ O ₃ > 13% and / or AI ₂ O ₃ ≤ 17% B ₂ O ₃ 16 to 25%

Na ₂ O <1.5%, preferably Na ₂ O <0.8%

K ₂ O <1.5%, preferably K ₂ O <0.8%

R ₂ O <2%, preferably R ₂ O <1% CaO <10%

MgO <10%

F <0 to 2%

RO 4 to 15%, preferably RO> 6% and / or RO <10%

Miscellaneous <3%, where R ₂ O = Na ₂ O + K ₂ O + Li ₂ O, and RO = CaO + MgO

It is thus possible to manufacture such glass strands under processing conditions close to those of glass E and thus obtain in a particularly economical manner glasses with good dielectric properties. The invention also relates to glass compositions suitable for producing reinforcing glass strands comprising the following constituents, within the limits defined below, expressed in percentages by weight:

SiO ₂ 50 to 60%, preferably SiO ₂ > 52% and / or SiO ₂ <57%

AI ₂ O ₃ 10 to 19%, preferably AI ₂ O ₃ > 13% and / or AI ₂ O ₃ ≤ 17% B ₂ O ₃ 16 to 25%

P ₂ O ₅ 0.5 to 4%

Na ₂ O <1.5%, preferably Na ₂ O <0.8%

K ₂ O <1.5%, preferably K ₂ O <0.8%

R ₂ O <2%, preferably R ₂ O <1% CaO <10%

MgO <10%

F <0 to 2%

RO 4 to 15%, preferably RO> 6% and / or RO <10%

The advantages presented by the glass strands according to the invention will be better appreciated through the following examples denoted Ex. 1 and Ex. 2, appearing in Table I, illustrating the present invention without however limiting it.

Comparative examples, marked A, B, C are also given in Table I.

In these examples, glass strands composed of glass filaments 14 μm in diameter are obtained by drawing molten glass, the glass has the composition mentioned in Table I, expressed in weight percentages.

When the total sum of the contents of all of the compounds is slightly less than or greater than 100%, it should be understood that the residual level corresponds to the impurities, minority components not analyzed (rate of at most 1 to 2%) and / or is due to the approximation accepted in this area in the analysis methods used. We denote by T (log η = 3) the temperature at which the viscosity of the glass is 10 ³ Poises (deciPascal second).

T It is noted | j _that i _o f _s the liquidus temperature of the glass corresponding to the temperature at which the most refractory phase, which may devitrification in the glass, has a zero growth rate is corresponds to the melting temperature of this devitrified phase.

The values of the dielectric properties (ε, ε ") measured both at 1 MHz and at 10 GHz are reported.

The 1 MHz measurements are carried out in a traditional manner, known to those skilled in the art for this type of metrology.

The measurements at 10 GHz were carried out according to the method described by WB Westphal ("Distributed Circuits", in "Dielectric materials and applications", the Technology Press of MIT and John Wiley & Sons, Inc. New York, Chapman & Hall, Ltd , London, 1954. See in particular p. 69). The principle of this method is based on the measurement of the dielectric properties of a sample in the form of a disc, placed against a waveguide.

This method provides precise results at very high frequencies.

The hydrolytic resistance measurements of the glass are also reported as carried out according to the "DGG" test defined above. Comparative examples A, B, C correspond respectively to

A: glass E

B: glass D

C: glass according to patent application WO 99/52833.

It appears that the examples according to the invention present a remarkable compromise between fiberizing properties and dielectric properties.

Indeed, their fiberizing properties are particularly advantageous, in particular with a liquidus temperature below 1000 ° C.

The fiber drawing range is very wide, in particular with a difference between T (log η = 3) and T | _ic jdus greater than 300 ° C. The dielectric properties of the compositions according to the invention are of the same order of magnitude as those of the compositions according to WO 99/52833 for measurements at 1 MHz.

A surprising effect is observed for measurements of dielectric properties carried out at 10 GHz with the glasses according to the invention. Indeed the dielectric losses are approximately two times lower with the glasses according to the invention than with the glasses according to WO 99/52833 and they are approximately five times lower than those obtained with an E glass.

The dielectric properties of glass D are thus remarkably approached, while considerably lowering the fiber-drawing temperature of the glasses according to the invention in comparison with that of glass D.

It is also noted that the glasses according to the invention have excellent hydrolytic resistance.

The glass strands according to the invention are advantageously suitable for all the usual applications of conventional glass strands E and can be substituted for glass strands D for certain applications.

Claims

1. Reinforcing glass wire, the composition of which comprises the following constituents, within the limits defined below, expressed in percentages by weight: Si0 ₂ 50 to 60%, preferably SiO ₂ > 52% and / or SiO ₂ <57%

AI ₂ O ₃ 10 to 19%, preferably AI ₂ O ₃ > 13% and / or AI ₂ O ₃ <17%

B ₂ 0 ₃ 16 to 25%

P ₂ 0 ₅ 0.5 to 4%

Na ₂ O <1.5%, preferably Na ₂ O <0.8% K ₂ 0 <1.5%, preferably K ₂ O <0.8%

R ₂ 0 <2%, preferably R ₂ O <1%

CaO <10%

MgO <10%

F <0 to 2% RO 4 to 15%, preferably RO> 6% and / or RO <10%

Miscellaneous <3%, where R ₂ O = Na ₂ 0 + K ₂ O + Li ₂ O, and RO = CaO + MgO

2. Glass strand according to claim 1, characterized in that the composition comprises a phosphorus level P ₂ O ₅ , such as P ₂ 0 ₅ > 1% and / or P ₂ O ₅ <3%, or even P ₂ O ₅ <2%

3. Glass strand according to one of the preceding claims, characterized in that the composition comprises a rate of lime CaO, such that CaO <8%, or even CaO <6% and / or CaO> 2%, even CaO> 4 %.

4. Glass strand according to one of the preceding claims, characterized in that the composition comprises a level of magnesia MgO, such as MgO <8%, or even MgO <6% and / or MgO> 2%.

5. Glass strand according to one of the preceding claims, characterized in that the composition comprises a boron content, B ₂ O ₃ , such as B ₂ O ₃ > 18% and / or B ₂ 0 ₃ <22%, see B ₂ O ₃ <20%.

6. Composite of glass strands and of organic and / or inorganic material (s), characterized in that it comprises glass strands as defined by one of claims 1 to 5.

7. Use of glass son defined by one of claims 1 to 5 for the manufacture of printed circuit support.

8. A method of manufacturing glass strands as defined in one of claims 1 to 5 according to which a multiplicity of strands of molten glass is stretched, flowing from a multiplicity of orifices arranged at the base of a or several dies, in the form of one or more sheets of continuous filaments, then the filaments are gathered into one or more threads which are collected on a moving support.

9. Method according to claim 8, characterized in that the molten glass supplying the orifices of the die (s) has the following composition, expressed in percentages by weight:

Si0 ₂ 50 to 60%, preferably SiO ₂ > 52% and / or SiO ₂ <57%

B ₂ 0 ₃ 16 to 25% P ₂ 0 ₅ 0.5 to 4%

Na ₂ O <1.5%, preferably Na ₂ O <0.8%

K ₂ 0 <1.5%, preferably K ₂ O ≤ 0.8%

R ₂ 0 <2%, preferably R ₂ O ≤ 1%

CaO ≤ 10% MgO <10%

F <0 to 2%

RO 4 to 15%, preferably RO> 6% and / or RO 10%

Miscellaneous <3%, where R ₂ O = Na ₂ 0 + K ₂ O + Li ₂ O, and RO = CaO + MgO 10. Glass composition suitable for the production of reinforcing glass strands comprising the following constituents, in the limits defined below expressed as percentages by weight:

SiO ₂ 50 to 60%, preferably SiO ₂ > 52% and / or Si0 ₂ <57%

AI ₂ O ₃ 10 to 19%, preferably AI ₂ O ₃ > 13% and / or Al ₂ 0 ₃ <17% B ₂ 0 ₃ 16 to 25%

P ₂ 0 ₅ 0.5 to 4%

Na ₂ O <1.5%, preferably Na ₂ O <0.8%

K ₂ O <1.5%, preferably K ₂ O <0.8%

R ₂ O <2%, preferably R ₂ O <1% CaO ≤ 10%

MgO <10%

F <0 to 2%

RO 4 to 15%, preferably RO> 6% and / or RO <10%

Miscellaneous <3%, where R ₂ O ≈ Na ₂ O + K ₂ O + Li ₂ O, and RO = CaO + MgO