Liquid crystalline polymer composition

Abstract

A polymer composition is disclosed that comprises a polymer matrix containing at least one thermotropic liquid crystalline polymer and at least one hollow inorganic filler having a dielectric constant of about 3.0 or less at a frequency of 100 MHz wherein the weight ratio of the at least one thermotropic liquid crystalline polymer to the at least one hollow inorganic filler is from about 0.1 to about 10 and wherein the polymer composition exhibits a dielectric constant of about 4 or less and a dissipation factor of about 0.02 or less, as determined at a frequency of 10 GHz.

Description

BACKGROUND OF THE INVENTION

Electrical components often contain molded parts that are formed from a liquid crystalline, thermoplastic resin. Recent demands on the electronic industry have dictated a decreased size of such components to achieve the desired performance and space savings. One such component is an electrical connector, which can be external (e.g., used for power or communication) or internal (e.g., used in computer disk drives or servers, link printed wiring boards, wires, cables and other EEE components). To obtain the desired properties, specific liquid crystalline polymers having certain monomers may be employed and in addition, certain additives may be utilized with the liquid crystalline polymers. Despite the benefits achieved, such compositions have various drawbacks. For example, such compositions may not exhibit the desired dielectric properties. In particular, such compositions may exhibit a relatively high dielectric constant and dissipation factor, which can make it difficult to use them in certain applications. Even further, such compositions may not exhibit the desired balance among the dielectric properties, thermal properties, and mechanical properties of the polymer composition.

As such, a need exists for a polymer composition that can have a relatively low dielectric constant and a relatively low dissipation factor but still maintain excellent mechanical properties and processibility (e.g., low viscosity).

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a polymer composition is disclosed that comprises a polymer matrix containing at least one thermotropic liquid crystalline polymer and at least one hollow inorganic filler having a dielectric constant of about 3.0 or less at a frequency of 100 MHz, wherein the weight ratio of the at least one thermotropic liquid crystalline polymer to the at least one hollow inorganic filler is from about 0.1 to about 10 and wherein the polymer composition exhibits a dielectric constant of about 4 or less and a dissipation factor of about 0.015 or less, as determined at a frequency of 10 GHz.

In accordance with another embodiment of the present invention, a molded part is disclosed that comprises the aforementioned polymer composition.

In accordance with another embodiment of the present invention, an electrical connector is disclosed that is formed from the aforementioned polymer composition.

Other features and aspects of the present invention are set forth in greater detail below.

BRIEF DESCRIPTION OF THE FIGURES

A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

FIG. 1A depicts a thin walled electrical connector according to aspects of present invention;

FIG. 1B depicts an enlarged view of a portion of thin walled connector of FIG. 1A;

FIG. 2 is an exploded perspective view of another embodiment of a thin walled connector and connector receptacle that may be formed according to the present invention; and

FIG. 3 depicts a 5G communication system including a base station, relay stations, user computing devices, and Wi-Fi repeaters.

DETAILED DESCRIPTION

It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention.

Generally speaking, the present invention is directed to a polymer composition that contains a unique combination of a thermotropic liquid crystalline polymer and a hollow inorganic filler. In particular, because the thermotropic liquid crystalline polymer and the hollow inorganic filler each have their own attributes, utilizing them in combination within a certain ratio can provide a polymer composition with beneficial properties. For instance, the polymer composition is not only able to exhibit a relatively low dielectric constant (Dk) and a relatively low dissipation factor (Df), the polymer composition also exhibits good mechanical properties and good processability.

To provide such beneficial properties, the weight ratio of the thermotropic liquid crystalline polymer to the hollow inorganic filler may be about 0.1 or more, in some embodiments about 1 or more, in some embodiments about 1.5 or more, in some embodiments from about 0.1 to about 10, in some embodiments from about 1 to about 10, in some embodiments from about 2 to about 10, in some embodiments from about 2 to about 6, and in some embodiments from about 2 to about 5.

As a result, the polymer composition may have a relatively low dielectric constant and dissipation factor. By providing a polymer composition with such dielectric properties, this may assist in minimizing signal loss and improving performance when utilized for a particular application, such as in signal transfer applications and in particular those related to 5G communications.

In this regard, the dielectric constant of the polymer composition may be about 4 or less, in some embodiments about 3.7 or less, in some embodiments about 3.5 or less, in some embodiments from about 0.5 to about 3.4, and in some embodiments from about 1.0 to about 3.2, as determined by the split post resonator method at a frequency of 10 GHz. In addition, the dissipation factor, a measure of the loss rate of energy, of the polymer composition may be about 0.02 or less, in some embodiments about 0.015 or less, in some embodiments about 0.01 or less, in some embodiments from about 0.001 to about 0.01, and in some embodiments from about 0.001 to about 0.006, as determined by the split post resonator method at a frequency of 10 GHz.

In particular, to provide such a relatively low dielectric constant, the hollow inorganic filler may be able to reduce the dielectric constant of the polymer matrix. For instance, utilization of both the hollow inorganic filler may lead to a reduction in the dielectric constant of the polymer matrix by about 2% or more, in some embodiments about 3% or more, in some embodiments from about 3.5% to about 50%, and in some embodiments from about 4% to about 30%. Similarly, utilization of both the hollow inorganic filler may lead to a reduction in the dissipation factor of the polymer matrix. For instance, utilization of the hollow inorganic filler may be able to reduce the dissipation factor of the polymer matrix by about 2% or more, in some embodiments about 3% or more, in some embodiments from about 3.5% to about 50%, and in some embodiments from about 4% to about 30%.

Conventionally, it was also believed that polymer compositions exhibiting such a combination of a low dielectric constant and a low dissipation factor would not also possess sufficiently good thermal, mechanical properties and ease in processing (i.e., low viscosity) to enable their use in certain types of applications. Contrary to conventional thought, however, the polymer composition has been found to possess both excellent thermal, mechanical properties and processability.

For example, the melting temperature of the polymer composition may, for instance, be about 180° C. or more, in some embodiments about 200° C., in some embodiments from about 210° C. to about 400° C., in some embodiments from about 220° C. to about 380° C. Even at such melting temperatures, the ratio of the deflection temperature under load (“DTUL”), a measure of short term heat resistance, to the melting temperature may still remain relatively high. For example, the ratio may range from about 0.5 to about 1.00, in some embodiments from about 0.6 to about 0.95, and in some embodiments from about 0.65 to about 0.85. The specific DTUL values may, for instance, be about 200° C. or more, in some embodiments from about 200° C. to about 350° C., such as from about 210° C. to about 320° C., such as from about 230° C. to about 290° C.

The polymer composition may also possess excellent mechanical properties, which can be useful when forming molded parts. For example, the polymer composition may exhibit a tensile strength of about 20 MPa or more, in some embodiments about 30 MPa or more, in some embodiments from about 40 MPa to about 300 MPa, and in some embodiments from about 50 MPa to about 100 MPa. The tensile properties may be determined at a temperature of 23° C. in accordance with ISO Test No. 527:2012. Also, the polymer composition may exhibit a flexural strength of about 20 MPa or more, in some embodiments about 50 MPa or more, in some embodiments from about 60 MPa to about 300 MPa, and in some embodiments from about 80 MPa to about 250 MPa. The flexural properties may be determined at a temperature of 23° C. in accordance with 178:2010. Furthermore, the polymer composition may also possess a high impact strength, which may be useful when forming thin substrates. The polymer composition may, for instance, possess a Charpy notched impact strength of about 3 kJ/m² or more, in some embodiments about 5 kJ/m² or more, in some embodiments about 7 kJ/m² or more, in some embodiments from about 8 kJ/m² to about 40 kJ/m², and in some embodiments from about 10 kJ/m² to about 25 kJ/m². The impact strength may be determined at a temperature of 23° C. in accordance with ISO Test No. ISO 179-1:2010.

Various embodiments of the present invention will now be described in more detail.

I. Polymer Composition

A. Polymer Matrix

The polymer matrix contains one or more liquid crystalline polymers. Liquid crystalline polymers are generally classified as “thermotropic” to the extent that they can possess a rod-like structure and exhibit a crystalline behavior in their molten state (e.g., thermotropic nematic state). The liquid crystalline polymers employed in the polymer composition typically have a melting temperature of about 180° C. or more, in some embodiments about 200° C. or more, in some embodiments from about 220° C. to about 350° C., in some embodiments from about 240° C. to about 300° C. The melting temperature may be determined as is well known in the art using differential scanning calorimetry (“DSC”), such as determined by ISO Test No. 11357-3:2011.

The liquid crystalline polymers may be formed from one or more types of repeating units as is known in the art. A liquid crystalline polymer may, for example, contain one or more aromatic ester repeating units generally represented by the following Formula (I):

wherein,

ring B is a substituted or unsubstituted 6-membered aryl group (e.g., 1,4-phenylene or 1,3-phenylene), a substituted or unsubstituted 6-membered aryl group fused to a substituted or unsubstituted 5- or 6-membered aryl group (e.g., 2,6-naphthalene), or a substituted or unsubstituted 6-membered aryl group linked to a substituted or unsubstituted 5- or 6-membered aryl group (e.g., 4,4-biphenylene); and

Y₁ and Y₂ are independently O, C(O), NH, C(O)HN, or NHC(O).

Typically, at least one of Y₁ and Y₂ are C(O). Examples of such aromatic ester repeating units may include, for instance, aromatic dicarboxylic repeating units (Y₁ and Y₂ in Formula I are C(O)), aromatic hydroxycarboxylic repeating units (Y₁ is O and Y₂ is C(O) in Formula I), as well as various combinations thereof.

Aromatic dicarboxylic repeating units, for instance, may be employed that are derived from aromatic dicarboxylic acids, such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl ether-4,4′-dicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4′-dicarboxybiphenyl, bis(4-carboxyphenyl)ether, bis(4-carboxyphenyl)butane, bis(4-carboxyphenyl)ethane, bis(3-carboxyphenyl)ether, bis(3-carboxyphenyl)ethane, etc., as well as alkyl, alkoxy, aryl and halogen substituents thereof, and combinations thereof. Particularly suitable aromatic dicarboxylic acids may include, for instance, terephthalic acid (“TA”), isophthalic acid (“IA”), and 2,6-naphthalenedicarboxylic acid (“NDA”). When employed, repeating units derived from aromatic dicarboxylic acids (e.g., IA, TA, and/or NDA) typically constitute from about 5 mol. % to about 60 mol. %, in some embodiments from about 10 mol. % to about 55 mol. %, and in some embodiments from about 15 mol. % to about 50 mol. % of the polymer.

Aromatic hydroxycarboxylic repeating units may also be employed that are derived from aromatic hydroxycarboxylic acids, such as, 4-hydroxybenzoic acid; 4-hydroxy-4′-biphenylcarboxylic acid; 2-hydroxy-6-naphthoic acid; 2-hydroxy-5-naphthoic acid; 3-hydroxy-2-naphthoic acid; 2-hydroxy-3-naphthoic acid; 4′-hydroxyphenyl-4-benzoic acid; 3′-hydroxyphenyl-4-benzoic acid; 4′-hydroxyphenyl-3-benzoic acid, etc., as well as alkyl, alkoxy, aryl and halogen substituents thereof, and combination thereof. Particularly suitable aromatic hydroxycarboxylic acids are 4-hydroxybenzoic acid (“HBA”) and 6-hydroxy-2-naphthoic acid (“HNA”). When employed, repeating units derived from hydroxycarboxylic acids (e.g., HBA and/or HNA) typically constitute from about 10 mol. % to about 85 mol. %, in some embodiments from about 20 mol. % to about 80 mol. %, and in some embodiments from about 25 mol. % to about 75 mol. % of the polymer.

Other repeating units may also be employed in the polymer. In certain embodiments, for instance, repeating units may be employed that are derived from aromatic diols, such as hydroquinone, resorcinol, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4′-dihydroxybiphenyl (or 4,4′-biphenol), 3,3′-dihydroxybiphenyl, 3,4′-dihydroxybiphenyl, 4,4′-dihydroxybiphenyl ether, bis(4-hydroxyphenyl)ethane, etc., as well as alkyl, alkoxy, aryl and halogen substituents thereof, and combinations thereof. Particularly suitable aromatic diols may include, for instance, hydroquinone (“HQ”) and 4,4′-biphenol (“BP”). When employed, repeating units derived from aromatic diols (e.g., HQ and/or BP) typically constitute from about 1 mol. % to about 30 mol. %, in some embodiments from about 2 mol. % to about 25 mol. %, and in some embodiments from about 5 mol. % to about 20 mol. % of the polymer. Repeating units may also be employed, such as those derived from aromatic amides (e.g., acetaminophen (“APAP”)) and/or aromatic amines (e.g., 4-aminophenol (“AP”), 3-aminophenol, 1,4-phenylenediamine, 1,3-phenylenediamine, etc.). When employed, repeating units derived from aromatic amides (e.g., APAP) and/or aromatic amines (e.g., AP) typically constitute from about 0.1 mol. % to about 20 mol. %, in some embodiments from about 0.5 mol. % to about 15 mol. %, and in some embodiments from about 1 mol. % to about 10 mol. % of the polymer. It should also be understood that various other monomeric repeating units may be incorporated into the polymer. For instance, in certain embodiments, the polymer may contain one or more repeating units derived from non-aromatic monomers, such as aliphatic or cycloaliphatic hydroxycarboxylic acids, dicarboxylic acids, diols, amides, amines, etc. Of course, in other embodiments, the polymer may be “wholly aromatic” in that it lacks repeating units derived from non-aromatic (e.g., aliphatic or cycloaliphatic) monomers.

Although not necessarily required, the liquid crystalline polymer may be a “high naphthenic” polymer to the extent that it contains a relatively high content of repeating units derived from naphthenic hydroxycarboxylic acids and naphthenic dicarboxylic acids, such as naphthalene-2,6-dicarboxylic acid (“NDA”), 6-hydroxy-2-naphthoic acid (“HNA”), or combinations thereof. That is, the total amount of repeating units derived from naphthenic hydroxycarboxylic and/or dicarboxylic acids (e.g., NDA, HNA, or a combination of HNA and NDA) may be about 10 mol. % or more, in some embodiments about 12 mol. % or more, in some embodiments about 15 mol. % or more, in some embodiments about 18 mol. % or more, in some embodiments about 30 mol. % or more, in some embodiments about 40 mol. % or more, in some embodiments about 45 mol. % or more, in some embodiments about 50 mol. % or more, in some embodiments about 55 mol. % or more, and in some embodiments, from about 60 mol. % to about 95 mol. % of the polymer. Without intending to be limited by theory, it is believed that such “high naphthenic” polymers are capable of reducing the tendency of the polymer composition to absorb water, which can help stabilize the dielectric constant and dissipation factor at high frequency ranges. Namely, such high naphthenic polymers typically have a water adsorption of about 0.015% or less, in some embodiments about 0.01% or less, and in some embodiments, from about 0.0001% to about 0.008% after being immersed in water for 24 hours in accordance with ISO 62-1:2008. The high naphthenic polymers may also have a moisture adsorption of about 0.01% or less, in some embodiments about 0.008% or less, and in some embodiments, from about 0.0001% to about 0.006% after being exposed to a humid atmosphere (50% relative humidity) at a temperature of 23° C. in accordance with ISO 62-4:2008. For instance, in one embodiment, the repeating units derived from HNA and/or NDA may constitute 10 mol. % or more, in some embodiments about 12 mol. % or more, in some embodiments about 15 mol. % or more, and in some embodiments, from about 18 mol. % to about 95 mol. % of the polymer. In such embodiments, the liquid crystalline polymer may also contain various other monomers, such as aromatic hydroxycarboxylic acid(s) (e.g., HBA) in an amount of from about 20 mol. % to about 60 mol. %, and in some embodiments, from about 30 mol. % to about 50 mol. %; aromatic dicarboxylic acid(s) (e.g., IA and/or TA) in an amount of from about 2 mol. % to about 30 mol. %, and in some embodiments, from about 5 mol. % to about 25 mol. %; and/or aromatic diol(s) (e.g., BP and/or HQ) in an amount of from about 2 mol. % to about 40 mol. %, and in some embodiments, from about 5 mol. % to about 35 mol. %.

In other embodiments, however, “low naphthenic” liquid crystalline polymers may also be employed in the composition in which the total amount of repeating units derived from naphthenic hydroxycarboxylic and/or dicarboxylic acids (e.g., NDA, HNA, or a combination of HNA and NDA) is less than 10 mol. %, in some embodiments about 8 mol. % or less, in some embodiments about 6 mol. % or less, and in some embodiments, from about 1 mol. % to about 5 mol. % of the polymer. In one particular embodiment, for example, the liquid crystalline polymer may be formed from repeating units derived from 4-hydroxybenzoic acid (“HBA”) and terephthalic acid (“TA”) and/or isophthalic acid (“IA”), as well as various other optional constituents. The repeating units derived from 4-hydroxybenzoic acid (“HBA”) may constitute from about 10 mol. % to about 80 mol. %, in some embodiments from about 30 mol. % to about 75 mol. %, and in some embodiments from about 45 mol. % to about 70 mol. % of the polymer. The repeating units derived from terephthalic acid (“TA”) and/or isophthalic acid (“IA”) may likewise constitute from about 5 mol. % to about 40 mol. %, in some embodiments from about 10 mol. % to about 35 mol. %, and in some embodiments from about 15 mol. % to about 35 mol. % of the polymer. Repeating units may also be employed that are derived from 4,4′-biphenol (“BP”) and/or hydroquinone (“HQ”) in an amount from about 1 mol. % to about 30 mol. %, in some embodiments from about 2 mol. % to about 25 mol. %, and in some embodiments from about 5 mol. % to about 20 mol. % of the polymer. Other possible repeating units may include those derived from 6-hydroxy-2-naphthoic acid (“HNA”), 2,6-naphthalenedicarboxylic acid (“NDA”), and/or acetaminophen (“APAP”).

The liquid crystalline polymers within the polymer matrix may be present in an amount of about 30 wt. % or more, in some embodiments about 40 wt. % or more, in some embodiments from about 40 wt. % to about 99.5 wt. %, in some embodiments from about 45 wt. % to about 90 wt. %, and in some embodiments from about 50 wt. % to about 85 wt. % based on the weight of the polymer composition. In certain embodiments, all of the liquid crystalline polymers may be “high naphthenic” polymers such as described above. In other embodiments, “low naphthenic” liquid crystalline polymers may be employed, preferably in only a relatively low amount. For example, low naphthenic liquid crystalline polymers may constitute from about 1 wt. % to about 50 wt. %, in some embodiments from about 2 wt. % to about 40 wt. %, and in some embodiments, from about 5 wt. % to about 30 wt. % of the total amount of liquid crystalline polymers in the composition, and from about 0.5 wt. % to about 45 wt. %, in some embodiments from about 2 wt. % to about 35 wt. %, and in some embodiments, from about 5 wt. % to about 25 wt. % of the entire composition. Conversely, high naphthenic liquid crystalline polymers may constitute from about 50 wt. % to about 99 wt. %, in some embodiments from about 60 wt. % to about 98 wt. %, and in some embodiments, from about 70 wt. % to about 95 wt. % of the total amount of liquid crystalline polymers in the composition, and from about 55 wt. % to about 99.5 wt. %, in some embodiments from about 65 wt. % to about 98 wt. %, and in some embodiments, from about 75 wt. % to about 95 wt. % of the entire composition.

B. Hollow Inorganic Fillers

To help achieve the desired dielectric properties, the polymer composition may include hollow inorganic fillers. For instance, these fillers may have a dielectric constant of about 3.0 or less, in some embodiments about 2.5 or less, in some embodiments from about 1.1 to about 2.3, and in some embodiments from about 1.2 to about 2.0 at 100 MHz. In addition, the hollow inorganic fillers may have a certain size and contribute to the strength of the polymer composition may also allowing the polymer composition to have a reduced weight and/or density because of the hollow nature.

In general, the hollow inorganic fillers have an interior hollow space or cavity and may be synthesized using techniques known in the art. The hollow inorganic fillers may be made from conventional materials. For instance, the hollow inorganic fillers may include alumina, silica, zirconia, magnesia, glass, fly ash, borate, phosphate, ceramic, and the like. In one embodiment, the hollow inorganic fillers may include hollow glass fillers, hollow ceramic fillers, and mixtures thereof. In one embodiment, the hollow inorganic fillers include hollow glass fillers.

The hollow glass fillers may be made from a soda lime borosilicate glass, a soda lime glass, a borosilicate glass, a sodium borosilicate glass, a sodium silicate glass, or an aluminosilicate glass. In this regard, in one embodiment, the composition of the glass, while not limited, may be at least about 65% by weight of SiO₂, 3-15% by weight of Na₂O, 8-15% by weight of CaO, 0.1-5% by weight of MgO, 0.01-3% by weight of Al₂O₃, 0.01-1% by weight of K₂O, and optionally other oxides (e.g., Li₂O, Fe₂O₃, TiO₂, B₂O₃). In another embodiment, the composition may be about 50-58% by weight of SiO₂, 25-30% by weight of Al₂O₃, 6-10% by weight of CaO, 1-4% by weight of Na₂O/K₂O, and 1-5% by weight of other oxides. Also, in one embodiment, the hollow glass fillers may include more alkaline earth metal oxides than alkali metal oxides. For example, the weight ratio of the alkaline earth metal oxides to the alkali metal oxides may be more than 1, in some embodiments about 1.1 or more, in some embodiments about 1.2 to about 4, and in some embodiments from about 1.5 to about 3. Regardless of the above, it should be understood that the glass composition may vary depending on the type of glass utilized and still provide the benefits as desired by the present invention.

The hollow inorganic fillers may have at least one dimension having an average value that is about 1 micrometers or more, in some embodiments about 5 micrometers or more, in some embodiments about 8 micrometers or more, in some embodiments from about 1 micrometer to about 150 micrometers, in some embodiments from about 10 micrometers to about 150 micrometers, and in some embodiments from about 12 micrometers to about 50 micrometers. In one embodiment, such average value may refer to a d₅₀ value.

Furthermore, the hollow inorganic fillers may have a Dio of about 3 micrometers or more, in some embodiments about 4 micrometers or more, in some embodiments from about 5 micrometers to about 20 micrometers, and in some embodiments from about 6 micrometers to about 15 micrometers. The hollow inorganic fillers may have a D₉₀ of about 10 micrometers or more, in some embodiments about 15 micrometers or more, in some embodiments from about 20 micrometers to about 150 micrometers, and in some embodiments from about 22 micrometers to about 50 micrometers.

In this regard, the hollow inorganic fillers may be present in a size distribution, which may be a Gaussian, normal, or non-normal size distribution. In one embodiment, the hollow inorganic fillers may have a Gaussian size distribution. In another embodiment, the hollow inorganic fillers may have a normal size distribution. In a further embodiment, the hollow inorganic fillers may have a non-normal size distribution. Examples of non-normal size distributions may include unimodal and multi-modal (e.g., bimodal) size distributions.

When referring to dimensions above, such dimension may be any dimension. In one embodiment, however, such dimension refers to a diameter. For example, such value for the dimension refers to an average diameter of spheres. The dimension, such as the average diameter, may be determined in accordance to 3M QCM 193.0. In this regard, in one embodiment, the hollow inorganic fillers may be referring to hollow spheres such as hollow glass spheres. For instance, the hollow inorganic fillers may have an average aspect ratio of approximately 1. In general, the average aspect ratio may be about 0.8 or more, in some embodiments about 0.85 or more, in some embodiments from about 0.9 to about 1.3, and in some embodiments from about 0.95 to about 1.05.

In addition, the hollow inorganic fillers may have relatively thin walls to help with the dielectric properties of the polymer composition as well as the reduction in weight. The thickness of the wall may be about 50% or less, in some embodiments about 40% or less, in some embodiments from about 1% to about 30%, and in some embodiments from about 2% to about 25% the average dimension, such as the average diameter, of the hollow inorganic fillers.

In addition, the hollow inorganic fillers may have a certain true density that can allow for easy handling and provide a polymer composition having a reduction in weight. In general, the true density refers to the quotient obtained by dividing the mass of a sample of the hollow fillers by the true volume of that mass of hollow fillers wherein the true volume is referred to as the aggregate total volume of the hollow fillers. In this regard, the true density of the hollow inorganic fillers may be about 0.1 g/cm³ or more, in some embodiments about 0.2 g/cm³ or more, in some embodiments from about 0.3 g/cm³ or more to about 1.2 g/cm³, and in some embodiments from about 0.4 g/cm³ or more to about 0.9 g/cm³. The true density may be determined in accordance to 3M QCM 14.24.1.

Even though the fillers are hollow, they may have a mechanical strength that allows for maintaining the integrity of the structure of the fillers resulting in a lower likelihood of the fillers being broken during processing and/or use. In this regard, the isotactic crush resistance (i.e., wherein at least 80 vol. %, such as at least 90 vol. % of the hollow fillers survive) of the hollow inorganic fillers may be about 20 MPa or more, in some embodiments about 100 MPa or more, in some embodiments from about 150 MPa to about 500 MPa, and in some embodiments from about 200 MPa to about 350 MPa. The isotactic crush resistance may be determined in accordance to 3M QCM 14.1.8.

The alkalinity of the hollow inorganic fillers may be about 1.0 meq/g or less, in some embodiments about 0.9 meq/g or less, in some embodiments from about 0.1 meq/g to about 0.8 meq/g, and in some embodiments from about 0.2 meq/g to about 0.7 meq/g. The alkalinity may be determined in accordance to 3M QCM 55.19. In order to provide a relatively low alkalinity, the hollow inorganic fillers may be treated with a suitable acid, such as a phosphoric acid.

In addition, the hollow inorganic fillers may also include a surface treatment to assist with providing a better compatibility with the polymer and/or other components within the polymer composition. As an example, the surface treatment may be a silanization. In particular, the surface treatment agents may include, but are not limited to, aminosilanes, epoxysilanes, and the like.

The hollow inorganic fillers may, for instance, constitute about 1 wt. % or more, in some embodiments about 4 wt. % or more, in some embodiments from about 5 wt. % to about 40 wt. %, and in some embodiments from about 10 wt. % to about 30 wt. % of the polymer composition.

C. Dielectric Fillers

In addition, a dielectric filler may also be employed in the polymer composition to improve the properties of the polymer composition. For instance, the dielectric filler may also be one that is capable of reducing the dielectric constant of the polymer composition. In addition, the dielectric filler may also contribute to improving other properties of the polymer composition. For example, the dielectric filler may also improve the thermal and mechanical properties of the polymer composition.

These dielectric fillers may be dielectric inorganic fillers, dielectric organic fillers, or a mixture thereof. In one embodiment, the dielectric fillers may be inorganic dielectric fillers. In another embodiment, the dielectric fillers may be organic dielectric fillers. In a further embodiment, the dielectric fillers may be a mixture of inorganic dielectric fillers and organic dielectric fillers. Furthermore, in one embodiment, these dielectric fillers may be solid fillers such that they do not have an interior cavity.

These dielectric fillers may constitute about 1 wt. % or more, in some embodiments about 2 wt. % or more, in some embodiments from about 3 wt. % to about 40 wt. %, and in some embodiments from about 5 wt. % to about 25 wt. % of the polymer composition. Furthermore, because the hollow inorganic filler and the dielectric filler each have their own attributes, utilizing them in combination within a certain ratio may provide a polymer composition with beneficial properties, such as a desired balance among dielectric, thermal, and/or mechanical properties. In this regard, the weight ratio of the hollow inorganic fillers to the dielectric fillers may be about 0.1 or more, in some embodiments about 0.1 to about 10, in some embodiments from about 0.1 to about 5, in some embodiments from about 0.5 to about 4, and in some embodiments from about 1 to about 2.

i. Fibrous Fillers

A fibrous filler may be employed in the polymer composition as a dielectric filler. The fibrous filler typically includes fibers having a high degree of tensile strength relative to their mass. For example, the ultimate tensile strength of the fibers (determined in accordance with ASTM D2101) is typically from about 1,000 to about 15,000 Megapascals (“MPa”), in some embodiments from about 2,000 MPa to about 10,000 MPa, and in some embodiments from about 3,000 MPa to about 6,000 MPa. To help maintain the desired dielectric properties, such high strength fibers may be formed from materials that are generally insulative in nature, such as glass, ceramics or minerals (e.g., alumina or silica), aramids (e.g., Kevler® marketed by E. I. duPont de Nemours, Wilmington, Del.), minerals, polyolefins, polyesters, etc.

In one embodiment, the fibrous filler may include glass fibers, mineral fibers, or a mixture thereof. For instance, in one embodiment, the fibrous filler may include glass fibers. The glass fibers particularly suitable may include E-glass, A-glass, C-glass, D-glass, AR-glass, R-glass, S1-glass, S2-glass, etc. In another embodiment, the fibrous filler may include mineral fibers. The mineral fibers may include those derived from silicates, such as neosilicates, sorosilicates, inosilicates (e.g., calcium inosilicates, such as wollastonite; calcium magnesium inosilicates, such as tremolite; calcium magnesium iron inosilicates, such as actinolite; magnesium iron inosilicates, such as anthophyllite; etc.), phyllosilicates (e.g., aluminum phyllosilicates, such as palygorskite), tectosilicates, etc.; sulfates, such as calcium sulfates (e.g., dehydrated or anhydrous gypsum); mineral wools (e.g., rock or slag wool); and so forth. Particularly suitable are inosilicates, such as wollastonite fibers available from Nyco Minerals under the trade designation NYGLOS® (e.g., NYGLOS® 4 W or NYGLOS® 8).

Further, although the fibrous fillers may have a variety of different sizes, fibers having a certain aspect ratio can help improve the mechanical properties of the polymer composition. That is, fibrous fillers having an aspect ratio (average length divided by nominal diameter) of about 2 or more, in some embodiments about 4 or more, in some embodiments from about 5 to about 50, and in some embodiments from about 8 to about 40 may be particularly beneficial. Such fibrous fillers may, for instance, have a weight average length of about 10 micrometer or more, in some embodiments about 25 micrometers or more, in some embodiments from about 50 micrometers or more to about 800 micrometers or less, and in some embodiments from about 60 micrometers to about 500 micrometers. Also, such fibrous fillers may, for instance, have a volume average length of about 10 micrometer or more, in some embodiments about 25 micrometers or more, in some embodiments from about 50 micrometers or more to about 800 micrometers or less, and in some embodiments from about 60 micrometers to about 500 micrometers.

The fibrous fillers may likewise have a nominal diameter of about 5 micrometers or more, in some embodiments about 6 micrometers or more, in some embodiments from about 8 micrometers to about 40 micrometers, and in some embodiments from about 9 micrometers to about 20 micrometers. The relative amount of the fibrous filler may also be selectively controlled to help achieve the desired mechanical and thermal properties without adversely impacting other properties of the polymer composition, such as its flowability and dielectric properties, etc. In this regard, the fibrous fillers may have a dielectric constant of about 6 or less, in some embodiments about 5.5 or less, in some embodiments from about 1.1 to about 5, and in some embodiments from about 2 to about 4.8 at a frequency of 1 GHz.

The fibrous filler may be in a modified or an unmodified form, e.g. provided with a sizing, or chemically treated, in order to improve adhesion to the plastic. In some examples, glass fibers may be provided with a sizing to protect the glass fiber, to smooth the fiber but also to improve the adhesion between the fiber and a matrix material. If present, a sizing may comprise silanes, film forming agents, lubricants, wetting agents, adhesive agents optionally antistatic agents and plasticizers, emulsifiers and optionally further additives. In one particular embodiment, the sizing may include a silane. Specific examples of silanes are aminosilanes, e.g. 3-trimethoxysilylpropylamine, N-(2-aminoethyl)-3-aminopropyltrimethoxy-silane, N-(3-trimethoxysilanylpropyl)ethane-1,2-diamine, 3-(2-aminoethyl-amino)propyltrimethoxysilane, N-[3-(trimethoxysilyl)propyl]-1,2-ethane-diamine.

ii. Particulate Fillers

Particulate fillers may also be employed in the polymer composition as a dielectric filler to help achieve the desired properties and/or color. Particulate clay minerals may be particularly suitable for use in the present invention. Examples of such clay minerals include, for instance, talc (Mg₃Si₄O₁₀(OH₂), halloysite (Al₂Si₂O₅(OH)₄), kaolinite (Al₂Si₂O₅(OH)₄), illite ((K,H₃O)(Al,Mg,Fe)₂(Si,Al)₄O₁₀[(OH)₂,(H₂O)]), montmorillonite (Na,Ca)_0.33(Al,Mg)₂Si₄O₁₀(OH)₂.nH₂O), vermiculite ((MgFe,Al)₃(Al,Si)₄O₁₀(OH)₂.4H₂O), palygorskite ((Mg,Al)₂Si₄O₁₀(OH).4(H₂O)), pyrophyllite (Al₂Si₄O₁₀(OH)₂), etc., as well as combinations thereof. In lieu of, or in addition to, clay minerals, still other particulate fillers may also be employed. For example, other suitable particulate silicate fillers may also be employed, such as mica, diatomaceous earth, and so forth. Mica, for instance, may be a particularly suitable mineral for use in the present invention. As used herein, the term “mica” is meant to generically include any of these species, such as muscovite (KAl₂(AlSi₃)O₁₀(OH)₂), biotite (K(Mg,Fe)₃(AlSi₃)O₁₀(OH)₂), phlogopite (KMg₃(AlSi₃)O₁₀(OH)₂), lepidolite (K(Li,Al)_2-3(AlSi₃)O₁₀(OH)₂), glauconite (K,Na)(Al,Mg,Fe)₂(Si,Al)₄O₁₀(OH)₂), etc., as well as combinations thereof.

The particulate filler may be in a modified or an unmodified form, e.g., provided with a treatment to improve the properties. In some examples, particulate filler may be fluorinated, for example as a coating. The fluorinated additive may be utilized to improve the processing of the polymer composition, such as by providing better mold filling, internal lubrication, mold release, etc. In certain embodiments, the fluorinated additive may include a fluoropolymer, which contains a hydrocarbon backbone polymer in which some or all of the hydrogen atoms are substituted with fluorine atoms. The backbone polymer may be polyolefinic and formed from fluorine-substituted, unsaturated olefin monomers. The fluoropolymer can be a homopolymer of such fluorine-substituted monomers or a copolymer of fluorine-substituted monomers or mixtures of fluorine-substituted monomers and non-fluorine-substituted monomers. Along with fluorine atoms, the fluoropolymer can also be substituted with other halogen atoms, such as chlorine and bromine atoms. Representative monomers suitable for forming fluoropolymers for use in this invention are tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, chlorotrifluoroethylene, perfluoroethylvinyl ether, perfluoromethylvinyl ether, perfluoropropylvinyl ether, etc., as well as mixtures thereof. Specific examples of suitable fluoropolymers include polytetrafluoroethylene, perfluoroalkylvinyl ether, poly(tetrafluoroethylene-co-perfluoroalkyvinylether), fluorinated ethylene-propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, etc., as well as mixtures thereof. The fluorinated additive may contain only the fluoropolymer, or it may also include other ingredients, such as those that aid in its ability to be uniformly dispersed within the polymer composition. In one embodiment, for example, the fluorinated additive may include a fluoropolymer in combination with a plurality of carrier particles. In such embodiments, for instance, the fluoropolymer may be coated onto the carrier particles, such as the particulate fillers mentioned above.

D. Functional Compounds

If desired, functional compounds may also be employed in the polymer composition to, among other things, help reduce the melt viscosity of the polymer composition. For example, the functional compound may be a functional aromatic compound, a non-aromatic functional compound, or a mixture thereof. In one embodiment, for example, the polymer composition may include a non-aromatic functional compound. Such compounds may serve a variety of purposes, such as reducing melt viscosity. One such non-aromatic functional compound is water. If desired, water can be added in a form that under process conditions generates water. For example, the water can be added as a hydrate that under the process conditions (e.g., high temperature) effectively “loses” water. Such hydrates include alumina trihydrate, copper sulfate pentahydrate, barium chloride dihydrate, calcium sulfate dehydrate, etc., as well as combinations thereof. In one particular embodiment, the hydrate may include alumina trihydrate.

When employed, the functional compounds, such as the hydrates, may constitute about 0.001 wt. % or more, in some embodiments about 0.005 wt. % or more, in some embodiments from about 0.005 wt. % to about 2 wt. %, and in some embodiments from about 0.01 wt. % to about 1 wt. % of the polymer composition.

E. Laser Activatable Additive

The polymer composition may be “laser activatable” in the sense that it contains an additive that can be activated by a laser direct structuring (“LDS”) process. In such a process, the additive is exposed to a laser that causes the release of metals. The laser thus draws the pattern of conductive elements onto the part and leaves behind a roughened surface containing embedded metal particles. These particles act as nuclei for the crystal growth during a subsequent plating process (e.g., copper plating, gold plating, nickel plating, silver plating, zinc plating, tin plating, etc.).

The laser activatable additive generally includes spinel crystals, which may include two or more metal oxide cluster configurations within a definable crystal formation. For example, the overall crystal formation may have the following general formula:AB₂O₄

wherein,

A is a metal cation having a valance of 2, such as cadmium, chromium, manganese, nickel, zinc, copper, cobalt, iron, magnesium, tin, titanium, etc., as well as combinations thereof; and

B is a metal cation having a valance of 3, such as chromium, iron, aluminum, nickel, manganese, tin, etc., as well as combinations thereof.

Typically, A in the formula above provides the primary cation component of a first metal oxide cluster and B provides the primary cation component of a second metal oxide cluster. These oxide clusters may have the same or different structures. In one embodiment, for example, the first metal oxide cluster has a tetrahedral structure and the second metal oxide cluster has an octahedral cluster. Regardless, the clusters may together provide a singular identifiable crystal type structure having heightened susceptibility to electromagnetic radiation. Examples of suitable spinel crystals include, for instance, MgAl₂O₄, ZnAl₂O₄, FeAl₂O₄, CuFe₂O₄, CuCr₂O₄, MnFe₂O₄, NiFe₂O₄, TiFe₂O₄, FeCr₂O₄, MgCr₂O₄, etc. Copper chromium oxide (CuCr₂O₄) is particularly suitable for use in the present invention and is available from Shepherd Color Co. under the designation “Shepherd Black 1GM.”

Laser activatable additives may constitute from about 0.1 wt. % to about 30 wt. %, in some embodiments from about 0.5 wt. % to about 20 wt. %, and in some embodiments, from about 1 wt. % to about 10 wt. % of the polymer composition.

F. Other Additives

A wide variety of additional additives can also be included in the polymer composition, such as lubricants, thermally conductive fillers, pigments, antioxidants, stabilizers, surfactants, waxes, flame retardants, anti-drip additives, nucleating agents (e.g., boron nitride), flow modifiers, coupling agents, antimicrobials, pigments or other colorants, impact modifiers, and other materials added to enhance properties and processability. Such optional materials may be employed in the polymer composition in conventional amounts and according to conventional processing techniques. When employed, for example, such additive(s) typically constitute from about 0.05 wt. % to about 5 wt. %, and in some embodiments from about 0.1 wt. % to about 1 wt. % of the polymer composition.

In one embodiment, the polymer composition may include a lubricant. For example, the lubricant may include polyolefin waxes (e.g., polyethylene wax), amide waxes, fatty acid ester waxes, etc. In one embodiment, the lubricant may include a polyolefin wax, such as a polyethylene wax. The lubricant may also be a fatty acid ester wax. Fatty acid ester waxes may, for instance, be obtained by oxidative bleaching of a crude natural wax and subsequent esterification of the fatty acids with an alcohol. The alcohol may, in some cases, have 1 to 4 hydroxyl groups and 2 to 20 carbon atoms. When the alcohol is multifunctional (e.g., 2 to 4 hydroxyl groups), a carbon atom number of 2 to 8 is particularly desired. Particularly suitable multifunctional alcohols may include dihydric alcohol (e.g., ethylene glycol, propylene glycol, butylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and 1,4-cyclohexanediol), trihydric alcohol (e.g., glycerol and trimethylolpropane), tetrahydric alcohols (e.g., pentaerythritol and erythritol), and so forth. Aromatic alcohols may also be suitable, such as o-, m- and p-tolylcarbinol, chlorobenzyl alcohol, bromobenzyl alcohol, 2,4-dimethylbenzyl alcohol, 3,5-dimethylbenzyl alcohol, 2,3,5-cumobenzyl alcohol, 3,4,5-trimethylbenzyl alcohol, p-cuminyl alcohol, 1,2-phthalyl alcohol, 1,3-bis(hydroxymethyl)benzene, 1,4-bis(hydroxymethyl)benzene, pseudocumenyl glycol, mesitylene glycol and mesitylene glycerol. Particularly suitable fatty acid esters for use in the present invention are derived from montanic waxes. Licowax® OP (Clariant), for instance, contains montanic acids partially esterified with butylene glycol and montanic acids partially saponified with calcium hydroxide. Thus, Licowax® OP contains a mixture of montanic acid esters and calcium montanate. Other montanic acid esters that may be employed include Licowax® E, Licowax® OP, and Licolub® WE 4 (all from Clariant), for instance, are montanic esters obtained as secondary products from the oxidative refining of raw montan wax. Licowax® E and Licolub®WE 4 contain montanic acids esterified with ethylene glycol or glycerine.

In one embodiment, the polymer composition may include a black pigment. The black pigment generally includes a plurality of carbon black particles, such as furnace black, channel black, acetylene black, lamp black, etc. The carbon black particles may have any desired shape, such as a granular, flake (scaly), etc. The average size (e.g., diameter) of the particles may, for instance, range from about 1 to about 200 nanometers, in some embodiments from about 5 to about 150 nanometers, and in some embodiments from about 10 to about 100 nanometers. It is also typically desired that the carbon black particles are relatively pure, such as containing polynuclear aromatic hydrocarbons (e.g., benzo[a]pyrene, naphthalene, etc.) in an amount of about 1 part per million (“ppm”) or less, and in some embodiments about 0.5 ppm or less. For example, the black pigment may contain benzo[a]pyrene in an amount of about 10 parts per billion (“ppb”) or less, and in some embodiments about 5 ppb or less.

If desired, the black pigment of the polymer composition may include a carrier resin that can encapsulate the carbon black particles, thereby providing a variety of benefits. For example, the carrier resin can enhance the ability of the particles to be handled and incorporated into the base polymer composition. While any known carrier resin may be employed for this purpose, in particular embodiments, the carrier resin is a liquid crystalline polymer; which may be the same or different than the polymer employed in the polymer composition. If desired, the carrier resin may be pre-blended with the carbon black particles to form a pigment masterbatch, which can later be combined with the polymer. When employed, the carrier resin typically constitutes from about 50 wt. % to about 95 wt. %, in some embodiments from about 60 wt. % to about 90 wt. %, and in some embodiments from about 70 wt. % to about 85 wt. % of the masterbatch, and the carbon black particles typically constitute from about 5 wt. % to about 50 wt. %, in some embodiments from about 10 wt. % to about 40 wt. %, and in some embodiments from about 15 wt. % to about 30 wt. % of the masterbatch. Of course, other components may also be incorporated into the masterbatch.

II. Formation

The components used to form the polymer composition may be combined together using any of a variety of different techniques as is known in the art. In one particular embodiment, for example, the liquid crystalline polymer, hollow inorganic filler, and other optional additives are melt processed as a mixture within an extruder to form the polymer composition. The mixture may be melt-kneaded in a single-screw or multi-screw extruder at a temperature of from about 250° C. to about 450° C. In one embodiment, the mixture may be melt processed in an extruder that includes multiple temperature zones. The temperature of individual zones is typically set within about −60° C. to about 25° C. relative to the melting temperature of the liquid crystalline polymer. By way of example, the mixture may be melt processed using a twin screw extruder such as a Leistritz 18-mm co-rotating fully intermeshing twin screw extruder. A general purpose screw design can be used to melt process the mixture. In one embodiment, the mixture including all of the components may be fed to the feed throat in the first barrel by means of a volumetric feeder. In another embodiment, different components may be added at different addition points in the extruder, as is known. For example, the liquid crystalline polymer may be applied at the feed throat, and certain additives (e.g., hollow inorganic filler) may be supplied at the same or different temperature zone located downstream therefrom. Regardless, the resulting mixture can be melted and mixed then extruded through a die. The extruded polymer composition can then be quenched in a water bath to solidify and granulated in a pelletizer followed by drying.

The melt viscosity of the polymer composition is generally low enough that it can readily flow into the cavity of a mold to form the small-sized circuit substrate. For example, in one particular embodiment, the polymer composition may have a melt viscosity of about 5 Pa-s or more, in some embodiments about 10 Pa-s or more, in some embodiments from about 10 Pa-s to about 500 Pa-s, in some embodiments from about 5 Pa-s to about 150 Pa-s, in some embodiments from about 5 Pa-s to about 100 Pa-s, in some embodiments from about 10 Pa-s to about 100 Pa-s, in some embodiments from about 15 to about 90 Pa-s, and in some embodiments from about 20 Pa-s to about 60 Pa-s, as determined at a shear rate of 1,000 seconds⁻¹ at a temperature of 20° C. higher than the melting temperature of the polymer. The melt viscosity may be determined in accordance with 11443:2005.

Also, the polymer composition may have a relatively low density. For example, the density may be about 3 g/cm³ or less, in some embodiments about 2.5 g/cm³ or less, in some embodiments from about 0.1 g/cm³ to about 2 g/cm³, and in some embodiments from about 0.5 g/cm³ to about 1.6 g/cm³. The density may be determined in accordance with ISO 1183.

In addition, the polymer composition may have a certain X value as described in U.S. Pat. No. 6,495,616, which is incorporated herein by reference, and as defined by the following equation:X=100×[(100/ρ₀+α/ρ₁+β/ρ₃)−(100+α+β)/ρ](α/ρ₁−α/ρ₂)wherein α represents the amount of the hollow inorganic fillers (part by weight based on 100 parts by weight of the liquid crystalline polymer), β represents the amount of the dielectric (e.g., fibrous) fillers (part by weight based on 100 parts by weight of the liquid crystalline polymer), ρ₀ represents the specific gravity of the liquid crystalline polymer, pi represents the true specific gravity of the hollow inorganic fillers, ρ₂ represents the material specific gravity of the hollow inorganic fillers, ρ₃ represents the specific gravity of the dielectric (e.g., fibrous) fillers, and p represents the specific gravity of ASTM No. 4 dumbbell (having a thickness of 2.5 mm) obtained by injection molding of said liquid crystalline polymer composition. In one embodiment, X may be from 10 to 50. In another embodiment, X may be less than 10 or greater than 50. For example. In one embodiment, X may be less than 10. In another embodiment, X may be greater than 50.

III. Molded Parts

Once formed, the polymer composition may be molded into a desired shape for a particular application. Typically, the shaped parts are molded using a one-component injection molding process in which dried and preheated plastic granules are injected into the mold.

In one embodiment, the molded part or shape may be a thin walled electrical connector. The thin walled electrical connector can have a variety of configurations within the scope of this disclosure. As an example, the thin walled connector can define a plurality of passageways or spaces between opposing walls. The passageways can accommodate contact pins to facilitate a large number of distinct electrical connections with the pins.

The electrical connector can also be very compact as a result of the polymer composition from which it is formed. For example, the polymer composition may exhibit excellent flow characteristics for forming very small features required to form the electrical connector described herein while also exhibiting minimal warpage when exposed to heat. In this regard, the walls can have respective widths “w” that are relatively thin, such as about 500 micrometers or less, in some embodiments about 400 micrometers or less, in some embodiments from about 25 micrometers to about 350 micrometers, and in some embodiments from about 50 micrometers to about 300 micrometers.

One particularly suitable thin walled electrical connector 100 is shown in FIG. 1A according to aspects of the present invention. FIG. 1B depicts an enlarged view of the thin walled connector 100 of FIG. 1A. As illustrated, insertion passageways or spaces 225 are defined between opposing walls 224 that can accommodate contact pins to facilitate a large number of distinct electrical connections. The thin walled electrical connector 100 can be very compact. More specifically, the walls 224 can have respective widths “w” that are relatively thin, such as within the ranges described above.

Another embodiment of a thin walled electrical connector 200 is depicted in FIG. 2. A board-side portion C2 that can be mounted onto the surface of a circuit board P. The connector 200 may also include a wiring material-side portion C1 structured to connect discrete wires 3 to the circuit board P by being coupled to the board-side connector C2. The board-side portion C2 may include a first housing 10 that has a fitting recess 10a into which the wiring material-side connector C1 is fitted and a configuration that is slim and long in the widthwise direction of the housing 10. The wiring material-side portion C1 may likewise include a second housing 20 that is slim and long in the widthwise direction of the housing 20. In the second housing 20, a plurality of terminal-receiving cavities 22 may be provided in parallel in the widthwise direction so as to create a two-tier array including upper and lower terminal-receiving cavities 22. A terminal 5, which is mounted to the distal end of a discrete wire 3, may be received within each of the terminal-receiving cavities 22. If desired, locking portions 28 (engaging portions) may also be provided on the housing 20 that correspond to a connection member (not shown) on the board-side connector C2.

As discussed above, the interior walls of the first housing 10 and/or second housing 20 may have be relatively thin (e.g., may have a relatively small width dimension), and can be formed from the polymer composition of the present invention.

As indicated, the electrical connector may be formed from a polymer composition that has a relatively low dielectric constant and dissipation factor. In this regard, the electrical connector may also reduce or prevent interference (e.g., “cross-talk”) between signals that are transmitted on adjacent or nearby pins because of the dielectric properties of the polymer composition from which it is formed. By providing a composition with such dielectric properties, this may assist in minimizing signal loss and improving performance when utilized for a particular application, such as in signal transfer applications and in particular those related to 5G communications. As used herein, “5G” generally refers to high speed data communication over radio frequency signals. 5G networks and systems are capable of communicating data at much faster rates than previous generations of data communication standards (e.g., “4G, “LTE”). Various standards and specifications have been released quantifying the requirements of 5G communications. As one example, the International Telecommunications Union (ITU) released the International Mobile Telecommunications-2020 (“IMT-2020”) standard in 2015. The IMT-2020 standard specifies various data transmission criteria (e.g., downlink and uplink data rate, latency, etc.) for 5G. The IMT-2020 Standard defines uplink and downlink peak data rates as the minimum data rates for uploading and downloading data that a 5G system must support. The IMT-2020 standard sets the downlink peak data rate requirement as 20 Gbit/s and the uplink peak data rate as 10 Gbit/s.

As another example, 3^rd Generation Partnership Project (3GPP) recently released new standards for 5G, referred to as “5G NR.” 3GPP published “Release 15” in 2018 defining “Phase 1” for standardization of 5G NR. 3GPP defines 5G frequency bands generally as “Frequency Range 1” (FR1) including sub-6 GHz frequencies and “Frequency Range 2” (FR2) as frequency bands ranging from 20-60 GHz. However, as used herein “5G frequencies” can refer to systems utilizing frequencies greater than 60 GHz, for example ranging up to 80 GHz, up to 150 GHz, and up to 300 GHz. As used herein, “5G frequencies” can refer to frequencies that are about 2.5 GHz or higher, in some embodiments about 3.0 GHz or higher, in some embodiments from about 3 GHz to about 300 GHz, or higher, in some embodiments from about 4 GHz to about 80 GHz, in some embodiments from about 5 GHz to about 80 GHz, in some embodiments from about 20 GHz to about 80 GHz, and in some embodiments from about 28 GHz to about 60 GHz.

Connectors described herein can be used in radio frequency systems that can satisfy or qualify as “5G” under standards released by 3GPP, such as Release 15 (2018), and/or the IMT-2020 Standard. To achieve such high speed data communication at high frequencies, antenna elements and arrays generally employ small feature sizes/spacing (e.g., fine pitch technology) and/or advanced materials that can improve antenna performance. For example, the feature size (spacing between antenna elements, width of antenna elements) etc. is generally dependent on the wavelength (“λ”) of the desired transmission and/or reception radio frequency propagating through the substrate dielectric on which the antenna element is formed (e.g., nλ/4 where n is an integer). Further, beamforming and/or beam steering can be employed to facilitate receiving and transmitting across multiple frequency ranges or channels (e.g., MIMO, massive MIMO).

Referring to FIG. 3, a 5G communication system 300 can include a base station 302, one or more relay stations 304, one or more user computing devices 306, one or more Wi-Fi repeaters 308 (e.g., “femtocells”), and/or other suitable antenna components for the 5G antenna system 300. The relay stations 304 can be configured to facilitate communication with the base station 302 by the user computing devices 306 and/or other relay stations 304 by relaying or “repeating” signals between the base station 302 and the user computing devices 306 and/or relay stations 304. The base station 302 can include a MIMO antenna array 310 configured to receive and/or transmit radio frequency signals 312 with the relay station(s) 304, Wi-Fi repeaters 308, and/or directly with the user computing device(s) 306. The user computing device 306 is not necessarily limited by the present invention and include devices such as 5G smartphones.

The MIMO antenna array 310 can employ beam steering to focus or direct radio frequency signals 312 with respect to the relay stations 304. For example, the MIMO antenna array 310 can be configured to adjust an elevation angle 314 with respect to an X-Y plane and/or a heading angle 316 defined in the Z-Y plane and with respect to the Z direction.

Similarly, one or more of the relay stations 304, user computing devices 306, Wi-Fi repeaters 308 can employ beam steering to improve reception and/or transmission ability with respect to MIMO antenna array 310 by directionally tuning sensitivity and/or power transmission of the device 304, 306, 308 with respect to the MIMO antenna array 310 of the base station 302 (e.g., by adjusting one or both of a relative elevation angle and/or relative azimuth angle of the respective devices).

The electrical connector can be employed to communicatively couple the various elements of the base station(s) 302, relay station(s) 304, and/or user computing devices 306. For example, the base station(s) 302, relay station(s) 304, and/or user computing devices 306. Such antennas and/or antenna arrays can be communicatively coupled with one or more integrated circuits, processors, memory, etc. For example, a front end module can be used to control transmission and/or reception of radio frequency signals using the antennas and/or antenna arrays. The electrical connector can communicatively couple any of the devices above.

The present invention may be better understood with reference to the following examples.

Test Methods

Melt Viscosity: The melt viscosity (Pa-s) may be determined in accordance with ISO Test No. 11443:2005 at a shear rate of 1,000 s⁻¹ and temperature 15° C. above the melting temperature (e.g., about 350° C.) using a Dynisco LCR7001 capillary rheometer. The rheometer orifice (die) had a diameter of 1 mm, length of 20 mm, L/D ratio of 20.1, and an entrance angle of 180°. The diameter of the barrel was 9.55 mm+0.005 mm and the length of the rod was 233.4 mm.

Melting Temperature: The melting temperature (“Tm”) may be determined by differential scanning calorimetry (“DSC”) as is known in the art. The melting temperature is the differential scanning calorimetry (DSC) peak melt temperature as determined by ISO Test No. 11357-2:2013. Under the DSC procedure, samples were heated and cooled at 20° C. per minute as stated in ISO Standard 10350 using DSC measurements conducted on a TA Q2000 Instrument.

Deflection Temperature Under Load (“DTUL”): The deflection under load temperature may be determined in accordance with ISO Test No. 75-2:2013 (technically equivalent to ASTM D648-07). More particularly, a test strip sample having a length of 80 mm, thickness of 10 mm, and width of 4 mm may be subjected to an edgewise three-point bending test in which the specified load (maximum outer fibers stress) was 1.8 Megapascals. The specimen may be lowered into a silicone oil bath where the temperature is raised at 2° C. per minute until it deflects 0.25 mm (0.32 mm for ISO Test No. 75-2:2013).

Tensile Modulus, Tensile Stress, and Tensile Elongation: Tensile properties may be tested according to ISO Test No. 527:2012 (technically equivalent to ASTM D638-14). Modulus and strength measurements may be made on the same test strip sample having a length of 80 mm, thickness of 10 mm, and width of 4 mm. The testing temperature may be about 23° C., and the testing speeds may be 1 or 5 mm/min.

Flexural Modulus, Flexural Stress, and Flexural Elongation: Flexural properties may be tested according to ISO Test No. 178:2010 (technically equivalent to ASTM D790-10). This test may be performed on a 64 mm support span. Tests may be run on the center portions of uncut ISO 3167 multi-purpose bars. The testing temperature may be about 23° C. and the testing speed may be 2 mm/min.

Unnotched and Notched Charpy Impact Strength: Charpy properties may be tested according to ISO Test No. ISO 179-1:2010) (technically equivalent to ASTM D256-10, Method B). This test may be run using a Type 1 specimen size (length of 80 mm, width of 10 mm, and thickness of 4 mm). When testing the notched impact strength, the notch may be a Type A notch (0.25 mm base radius). Specimens may be cut from the center of a multi-purpose bar using a single tooth milling machine. The testing temperature may be about 23° C.

Dielectric Constant (“Dk”) and Dissipation Factor (“Df”): The dielectric constant (or relative static permittivity) and dissipation factor are determined using a known split-post dielectric resonator technique, such as described in Baker-Jarvis, et al., IEEE Trans. on Dielectric and Electrical Insulation, 5(4), p. 571 (1998) and Krupka, et al., Proc. 7th International Conference on Dielectric Materials: Measurements and Applications, IEEE Conference Publication No. 430 (September 1996). More particularly, a plaque sample having a size of 80 mm×80 mm×1 mm was inserted between two fixed dielectric resonators. The resonator measured the permittivity component in the plane of the specimen. Five (5) samples are tested and the average value is recorded. The split-post resonator can be used to make dielectric measurements in the low gigahertz region, such as 1 GHz, 2 GHz or 10 GHz.

Example 1

Samples 1-5 are formed from liquid crystalline polymers (LCP 1 or LCP 2), hollow glass spheres, as well as mica, wollastonite, glass powder, and/or glass fibers. LCP 1 is formed from 43% HBA, 9% TA, 29% HQ, and 20% NDA. LCP 2 is formed from 48% HNA, 2% HBA, 25% BP, and 25% TA. The hollow glass spheres had an average diameter of 18 micrometers. The glass powder had a dielectric constant of 4.8 as determined at a frequency of 1 GHz. Further, the glass fibers employed had an initial length of either 3 mm or 4 mm. The polymer compositions may also include a polyethylene lubricant, alumina trihydrate, pigments, and/or various other minor additives. Compounding was performed using a 25-mm single screw extruder.

TABLE 1
Sample	1	2	3	4	5	6
LCP 1	—	—	77.3	67.3	67.3	—
LCP 2	72.8	71.8	—	—	—	71.8
Hollow Glass Spheres	17	17	20	15	15	17
Mica	—	—	—	15	—	—
Wollastonite	—	—	—	—	15	—
Glass Powder	—	1		—	—	1
Glass Fibers (4 mm length)	—	—	—	—	—	10
Glass Fibers (3 mm length)	10	10		—	—	—
Alumina Trihydrate	0.2	0.2	—	—	—	0.2
Polyethylene	—	—	0.2	0.2	0.2	—
Black Pigment Masterbatch	—	—	2	2	2	—
Other Additives	—	—	0.5	0.5	0.5	—

The samples were then tested for thermal and mechanical properties. The results are set forth below in Table 2.

TABLE 2
Sample	1	2	3	4	5	6
Dielectric Constant (10 GHz)	3.03	3.01	3.0	3.2	3.2	2.93
Dissipation Factor (10 GHz)	0.002	0.002	0.003	0.003	0.003	0.003
Dielectric Constant (2 GHz)	—	2.99	—	—	—	—
Dissipation Factor (2 GHz)	—	0.002	—	—	—	—
DTUL at 1.8 MPa (° C.)	289	291	243	243	250	—
Tensile Strength (MPa)	78	86	77	66	65	99
Flexural Strength (MPa)	122	—	—	—	—	—
Impact Strength (kJ/m2)	11	7	15	6	6	—
Density (g/cm3)	1.22	1.18	1.14	1.27	1.28	—

Example 2

Samples 7 is formed from liquid crystalline polymers (LCP 2 and LCP 4), hollow glass spheres, glass powder, glass fibers, and alumina trihydrate. LCP 4 is formed from 60% HBA, 4% HNA, 18% TA, and 18% BP. The glass powder had a dielectric constant of 4.8 as determined at a frequency of 1 GHz. Compounding was performed using a 25-mm single screw extruder.

TABLE 3
Sample                     7
LCP 2                      49.8
LCP 4                      15.4
Hollow Glass Spheres       17.0
Glass Powder               1.0
Glass Fibers (4 mm length) 10.0
Alumina Trihydrate         0.2
Copper Chromite            6.6

The samples were then tested for thermal and mechanical properties. The results are set forth below in Table 4.

TABLE 4
Sample                           7
Dielectric Constant (2 GHz)      3.07
Dissipation Factor (2 GHz)       0.0043
Dielectric Constant (10 GHz)     3.14
Dissipation Factor (10 GHz)      0.0035
Melt Viscosity at 1,000 s−1 (Pa-s) 55.5
Melt Viscosity at 400 s−1 (Pa-s) 88.9
Melting Temperature (° C.)       338.6
DTUL at 1.8 MPa (° C.)           217
Tensile Strength (MPa)           81
Tensile Modulus (MPa)            7,658
Tensile Elongation (%)           1.41
Flexural Strength (MPa)          116
Flexural Modulus (MPa)           7,241
Flexural Elongation (%)          1.91
Charpy Notched Impact Strength (kJ/m2) 3.1
Charpy Unnotched Impact Strength (kJ/m2) 7.3

These and other modifications and variations of the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.

Claims

1. A polymer composition comprising: a polymer matrix containing at least one thermotropic liquid crystalline polymer, andat least one hollow inorganic filler having a dielectric constant of about 3.0 or less at a frequency of 100 MHz,wherein the weight ratio of the at least one thermotropic liquid crystalline polymer to the at least one hollow inorganic filler is from about 0.1 to about 10,wherein the polymer composition exhibits a dielectric constant of 3.4 or less and a dissipation factor of about 0.02 or less, as determined at a frequency of 10 GHz, and wherein repeating units derived from aromatic dicarboxylic acids constitute from 15 mol. % to about 60 mol. % of the thermotropic liquid crystalline polymer.

2. The polymer composition of claim 1, wherein the weight ratio of the at least one thermotropic liquid crystalline polymer to the at least one hollow inorganic filler is from about 2 to about 6.

3. The polymer composition of claim 1, wherein the polymer composition exhibits a dielectric constant of about 3.2 or less and a dissipation factor of about 0.005 or less, as determined at a frequency of 10 GHz.

4. The polymer composition of claim 1, wherein the thermotropic crystalline polymer is an aromatic polyester that contains repeating units derived from 4-hydroxybenzoic acid.

5. The polymer composition of claim 1, wherein the thermotropic liquid crystalline polymer has a total amount of repeating units derived from naphthenic hydroxycarboxylic and/or naphthenic dicarboxylic acids of about 10 mol. % or more.

6. The polymer composition of claim 5, wherein the thermotropic liquid crystalline polymer has a total amount of repeating units derived from naphthalene-2,6-dicarboxylic acid of about 10 mol. % or more.

7. The polymer composition of claim 1, wherein the thermotropic crystalline polymer is present in an amount of about 40 wt. % or more.

8. The polymer composition of claim 1, wherein the at least one hollow inorganic filler comprises hollow glass spheres.

9. The polymer composition of claim 8, wherein the hollow glass spheres have an aspect ratio of from about 0.8 to about 12.

10. The polymer composition of claim 8, wherein the hollow glass spheres have an average diameter of from about 1 micrometer to about 150 micrometers.

11. The polymer composition of claim 10, wherein the thickness of the walls of the hollow glass spheres is about 40% or less the average diameter of the hollow glass spheres.

12. The polymer composition of claim 1, wherein the at least one hollow inorganic filler is present in an amount of from about 5 wt. % to about 40 wt. %.

13. The polymer composition of claim 1, wherein the polymer composition further comprises at least one dielectric filler.

14. The polymer composition of claim 13, wherein the at least one dielectric filler comprises a fibrous filler, a particulate filler, or a mixture thereof.

15. The polymer composition of claim 13, wherein the fibrous filler comprises a glass fiber.

16. The polymer composition of claim 13, wherein the fibrous filler comprises wollastonite.

17. The polymer composition of claim 13, wherein the particulate filler comprises mica.

18. The polymer composition of claim 17, wherein the mica is modified by a fluorinated additive.

19. The polymer composition of claim 13, wherein the at least one dielectric filler is present in an amount of from about 3 wt. % to about 40 wt. %.

20. The polymer composition of claim 13, wherein the thermotropic liquid crystalline polymer is present in an amount about 50 wt. % or more, the at least one hollow inorganic filler is present in an amount of from about 5 wt. % to about 40 wt. %, and the at least one dielectric filler is present in an amount of from about 3 wt. % to about 40 wt. %.

21. The polymer composition of claim 1, wherein the polymer composition further comprises a hydrate.

22. The polymer composition of claim 1, wherein the polymer composition further comprises a polyethylene wax.

23. The polymer composition of claim 1, wherein the polymer composition has a deflection temperature under load of about 200° C. or more at 1.8 MPa as determined in accordance with ISO 75.

24. The polymer composition of claim 1, wherein the polymer composition has a tensile strength of about 40 MPa or more as determined in accordance with ISO 527.

25. The polymer composition of claim 1, wherein the polymer composition has a Charpy notched impact strength of about 3 kJ/m2 or more as determined in accordance with ISO 179.

26. The polymer composition of claim 1, wherein the polymer composition has a density of about 2.5 g/cm3 or less as determined in accordance with ISO 1183.

27. The polymer composition of claim 1, wherein the polymer composition has a melt viscosity of from about 10 Pa-s to about 100 Pa-s, as determined at a shear rate of 1,000 seconds−1 and a temperature of 20° C. higher than the melting temperature of the at least one polymer.

28. The polymer composition of claim 1, wherein the polymer composition further comprises a laser activatable additive.

29. The polymer composition of claim 28, wherein the laser activatable additive contains spinel crystals having the following general formula: AB2O4 wherein,A is a metal cation having a valance of 2; andB is a metal cation having a valance of 3.

30. The polymer composition of claim 28, wherein the spinel crystals include MgAl2O4, ZnAl2O4, FeAl2O4, CuFe2O4, CuCr2O4, MnFe2O4, NiFe2O4, TiFe2O4, FeCr2O4, MgCr2O4, or a combination thereof.

31. A molded part that comprises the polymer composition of claim 1.

32. An electrical connector formed from the polymer composition of claim 1.