Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/301—Macromolecular compounds obtained by reactions forming a linkage containing sulfur with or without nitrogen, oxygen or carbon in the main chain of the macromolecule, not provided for in group H01B3/302
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/24—Acids; Salts thereof
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate
  • H05K1/0313—Organic insulating material
  • H05K1/032—Organic insulating material consisting of one material
  • H05K1/0333—Organic insulating material consisting of one material containing S
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate
  • H05K1/0313—Organic insulating material
  • H05K1/0353—Organic insulating material consisting of two or more materials, e.g. two or more polymers, polymer + filler, + reinforcement
  • H05K1/0373—Organic insulating material consisting of two or more materials, e.g. two or more polymers, polymer + filler, + reinforcement containing additives, e.g. fillers
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/16—Printed circuits incorporating printed electric components, e.g. printed resistor, capacitor, inductor

Definitions

• This invention relates generally to the field of materials having a high dielectric constant, and more particularly to composite materials comprising poly(phenylene sulfide) and ceramic fillers that have high dielectric constants and low loss tangents.
• New materials with high dielectric constants and low loss tangents are needed in the electronics industry for use at high frequencies and as a means to enable further miniaturization. These materials are particularly useful if they can be made into thin films, sheets, plaques, and other molded shapes, so that they can be used as circuit boards at microwave frequencies, high energy density capacitors, filters, antennas, buried components, and multichip modules. These have a variety of end uses, as for example in wireless communications. Many ceramic materials have the desired high dielectric constant and low dielectric loss, but they are not readily made into thin films. Ceramic materials that have been fabricated into films and shaped articles are also generally brittle.
• One approach to making films and sheets with the desired properties is to utilize a composite comprising a polymeric matrix and a ceramic filler having a high dielectric constant. This approach is difficult because the composites need high levels of the ceramic filler in order to achieve the desired high dielectric constant while retaining rheological properties that make the composites suitable for extrusion or molding.
• the composites must also be stable to changes in ambient moisture (humidity) and temperature. Resistance to elevated temperatures, as well as high mechanical strength, impact resistance and chemical resistance are also all desirable.
• flat substrates made from these materials will need to be made into laminates with copper and/or other materials.
• This composite was easy to process before the epoxy resins set because of the low viscosity of the epoxy prepolymer, and dielectric constants up to about 20 and loss tangents of about 0.0165 - 0.0173 were observed with this composite.
• High dielectric constant/low loss tangent composites have now been found that utilize a thermoplastic polymer and a filler, and that are easy to fabricate without complex processing.
• Polymeric compositions having a high dielectric constant are made by combining polyphenylene sulfide and a ceramic having a high dielectric constant.
• the ceramic is one or more of the following: SrTiO 3 , barium neodymium titanate, or barium strontium titanate/magnesium zirconate.
• the ceramic is included in an amount that is sufficient to yield a composition that has a dielectric constant of at least about 4.0 at 1 GHz of frequency.
• Laminates that have a high dielectric constant and low loss tangent may also be made from these compositions.
• Such laminates include at least one flat substrate of the polymeric composition described above, which contains poly(phenylene sulfide) and one or more of SrTiO 3 , barium neodymium titanate, or barium strontium titanate/magnesium zirconate.
• a layer of copper or other metal is laminated or coated onto one or both sides of the sheet of the polymeric composition, resulting in a laminated structure which has a dielectric constant of at least about 4.0 at a frequency of 1.0 GHz.
• a method of making a laminate that has a high dielectric constant includes the following steps:
• shape is meant any process for making a polymer into a fabricated product, such as a sheet, film or three-dimensional object. Such processes include extrusion, injection molding, calendaring, compression molding, and the like.
• the polymeric compositions described above may optionally also include other fillers, which are included as reinforcing fillers or for other purposes, such as for lubrication for molding or to modify the electrical properties.
• Fillers that are preferred include glass fiber, mica, alumina, and magnesium titanate.
• Mica, magnesium titanate, and alumina lead to improved physical properties and also reduce the coefficient of thermal expansion (CTE), resulting in reduced warpage in laminates made using these compositions. Mica reduces the CTE in the plane of a flat substrate or laminate, and to a lesser extent, reduces the CTE perpendicular to the plane.
• Alumina and magnesium titanate effect a greater reduction in the CTE perpendicular to the plane of the substrate or laminate.
• the combination of poly(phenylene sulfide) and one or more of the ceramics from the group that includes SrTiO 3 , barium neodymium titanate, and barium strontium titanate/magnesium zirconate yields a composition that is excellent for making substrates having a high dielectric constant for use in electronic circuits at high frequencies (above about 500 MHz).
• the high dielectric constant is needed for further miniaturization.
• the loss tangent also known as dielectric loss, dielectric loss factor, or dissipation factor
• the compositions comprising a polymer and a ceramic or other filler having a high dielectric constant are also referred to herein as "high dielectric composites" and "high dielectric constant composites.”
• Poly(phenylene sulfide) is a well known and readily available polymer which has the following molecular formula:
• Ar is a 1 ,4-phenylene group.
• a small percentage of other aromatic groups may also be included in the polymer chain, such as 1 ,3-phenylene, 4,4'-biphenylene, 2,4-tolylene, 2,5-tolylene, 1 ,4-naphthylene, 2,6-napthylene, 1 -methoxy-2,5-phenylene, 2-halo-1 ,4-phenylene (where halo- is a chloro, bromo, fluoro, or iodo substituent), and the like.
• poly(phenylene sulfide) Some of the commercial grades of poly(phenylene sulfide) are lightly branched due to the presence of a small number of trifunctional aryl groups or other crosslinks in the polymer. All of the commercial grades of poly(phenylene sulfide) appear to be suitable. Polyrphenylene sulfide) is available from a number of manufacturers, including Hoechst Celanese Corporation under the FORTRON ® trademark, Phillips Petroleum Company under the RYTON ® trademark, G.E. Plastics under the SUPEC ® trademark, and Mobay Corporation under the TEDUR ® trademark.
• the three preferred ceramic materials that are blended with poly(phenylene sulfide) are all commercially available or readily synthesized by methods known in the art.
• the metal titanates can be made by sintering the metal oxides (e.g., oxides of Sr,
• Ba, Nd, Zr and/or Mg and TiO 2 in the stoichiometric ratio needed to obtain the desired product. See for example "Ceramic Dielectrics And Capacitors," by J.M. Herbert, Gordon and Breach Science Publishers, New York, 1985, for more details on synthetic methods.
• the ratio of Ba and Nd, or Mg, Ba, Zr and Sr, in the mixed metal titanates can be optimized to achieve the desired loss tangent and dielectric constant.
• Strontium titanate is available from several manufacturers. Strontium titanate and barium neodymium titanate are both available from Tarn Ceramics, Niagara Falls, NY, and are sold as TICONTM55 and COG900MW respectively.
• the commercial barium neodymium titanate has a Ba:Nd atomic ratio of about 1 , with a small amount of Bi ( ⁇ 10% compared with Ba or Nd) and enough Ti to balance the titanate stoichiometry.
• This material has a dielectric constant of about 92 and a loss tangent of about 0.001 at 1.0 GHz.
• a preferred barium strontium titanate/magnesium zirconate can be made by sintering about 68% by weight BaTiO 3 , about 28% by weight SrTiO 3 , and about 3% MgZrO 3 , or by sintering a mixture of the oxides.
• Strontium titanate is the preferred high dielectric ceramic. It is readily compounded with poly(phenylene sulfide) to yield high dielectric compositions that are readily fabricated into shaped articles by such methods as injection molding and extrusion of films or sheets. It is preferably used as a powder having an average particle size in the range of about 0.2 microns to about 10 microns, preferably about 1 to about 2 microns. Larger or smaller particle sizes can also be used, depending on the size and shape of the article to be fabricated. The electrical properties are easily fine-tuned for specific applications by adjusting the amount of SrTiO 3 .
• the loss tangent is low at all levels of SrTiO 3 , generally not exceeding 0.003 at a frequency of 1.0 GHz. Furthermore, because of the ease of mixing and injection molding these compositions, specific compositions can be made that give reproducible dielectric constants. Thus, for example, the compositions containing 19% of SrTiO 3 in poly(phenylene sulfide) on a volume basis have a dielectric constant of 6.03, with a standard deviation of 0.135 for 100 sample data points.
• concentration of the SrTiO 3 in poly(phenylene sulfide) for any application depends on the desired dielectric constant, with concentrations typically ranging from about 10% to about 70%, on a volume basis, with preferred ranges being about 20% to about 70%, or about 30% to about 70%, depending on the specific application.
• concentrations typically ranging from about 10% to about 70%, on a volume basis, with preferred ranges being about 20% to about 70%, or about 30% to about 70%, depending on the specific application.
• compositions having a dielectric constant of at least about 6, at least about 10, or other values are readily made for specific applications.
• the compounds of ceramics e.g. SrTiO 3
• poly(phenylene sulfide) have good tensile properties, because the ceramic filler acts as a reinforcing filler.
• other fillers such as glass fiber, can also be added to further reinforce the filled poly(phenylene sulfide) or for other purposes, such as lubrication for molding or to modify the electrical properties.
• These fillers are added at levels such that the poly(phenylene sulfide) has a total content of fillers, including the ceramic, in the range of about 10% to about 70% by volume.
• the high dielectric ceramic e.g. SrTiO 3
• the ceramic may be used at a level of as low as about 2% by volume.
• Solid or reinforcing fillers that may be used include carbon, wollastonite, mica, talc, silicates, silica, clay, poly(tetrafluoroethylene), thermotropic liquid crystalline polymer, alumina, glass, rock wool, silicon carbide, diamond, fused quartz, aluminum nitride, beryllium oxide, boron nitride, and magnesium titanate, all in either particle or fiber form, including mixtures of more than one filler.
• Antioxidants, mold lubricants, and sizing and coupling agents may also be added. The use of some of these other additives (e.g.
• Mica, magnesium titanate, and alumina are preferred for applications in which a low coefficient of thermal expansion is desired, such as laminates.
• Mica reduces the CTE in the plane of a flat substrate, and to a lesser extent, perpendicular to the plane.
• Alumina reduces the CTE perpendicular to the plane more strongly than does mica. Mica and alumina also reinforce the compositions.
• the high dielectric polymer compositions are made by standard methods for making compounds of polymers and fillers. These methods typically involve mixing the filler and polymer at a temperature high enough to melt the polymer. Compounding of the polymer and ceramic filler in a twin screw extruder is the preferred method.
• the polymeric compositions are readily made into shaped articles.
• the filled poly(phenylene sulfide) has a low melt viscosity and can readily be shaped into films, sheets, plaques, disks, and other flat shapes which are particularly useful as substrates in electronics (e.g. printed circuit boards). Three dimensional shapes may also be made.
• the polymers may be shaped by many processes, such as extrusion, injection molding, and compression molding. Films and sheets typically are made by injection molding or extrusion processes. Laminates having a high dielectric constant and low loss tangent are also readily made from these polymer compositions. Such laminates are particularly useful in making rf circuits, such as antennas, filters, couplers, splitters, and the like.
• the laminates generally have a flat substrate of the polymeric composition described above, such as a sheet, film, or plaque, placed between two layers of copper or other metal.
• the metal has not necessarily been applied by a lamination process, so that the term "laminates” has a broader meaning and includes multilayer structures made by methods other than lamination.
• the flat substrates have two surfaces, other than the edges. The thickness of the substrate is a matter of choice, depending on the application, but generally will be in the range of about 1 mil to about 500 mils.
• At least one of the surfaces of the flat substrate has a metal layer adhering to it, and generally both surfaces have a metal layer.
• the metal is present as an electrical conductor. Copper is the preferred metal, but others may be used, such as gold, titanium, silver and alloys thereof or with copper.
• the metal may be included in the form of a coating which has been applied by a coating process, such as vapor deposition or sputtering, or by electroplating onto a sheet whose surface has been activated for electroplating.
• the preferred method of applying the metal is by an actual lamination process, whereby metal film or foil is laminated onto the surfaces of the substrates.
• the metal film or foil is thin, generally being in the range of about V ⁇ mil to about 12 mils, yielding a laminate with the same thickness of metal.
• foil and “film” are used interchangably herein when describing metal films and foils.
• the metal is laminated onto the filled poly(phenylene sulfide) sheet by the use of an adhesive or by heating the poly(phenylene sulfide) to the melt temperature while the metal film or foil is pressed against the polymeric sheet.
• the metal film or foil can be laminated onto a freshly extruded sheet of poly(phenylene sulfide) while the sheet is still in a molten or softened state by co-feeding the metal film or foil with the poly(phenylene sulfide) sheet as it emerges from the die of the extruder and passing the metal film or foil and polymer sheet through an apparatus that applies pressure, such as a set of rollers.
• Another method of making a laminate directly from molten polymer is to place the metal film or foil against the inner walls of a mold and then feed molten polymer into the moid under pressure in an injection molding process. The pressure of the molding process results in a laminate with good adhesion after the polymer cools and hardens.
• the preferred method is application of the metal foil or film under heat and pressure to a preformed polymer substrate.
• the preferred metal foil has a matte surface on one side to facilitate adhesion between the metal and the polymer. Foil can be obtained in which the matte surface has a surface profile with an arithmetic mean roughness value of about 1 micron and a mean peak to valley height of about 10 microns. These give acceptable adhesion.
• Foils can also be obtained that have been treated to increase the surface roughness on the matte side. These give better adhesion and are preferred.
• the laminates made by this method have a dielectric constant that is greater than or equal to about 4 at a frequency of 1.0 GHz.
• enough ceramic filler may be included to yield a laminate with a dielectric constant of at least about 6, at least about 10, or other values, which may be higher.
• the loss tangent is low, generally not exceeding about 0.003 at a frequency of 1.0 GHz.
• the coefficient of thermal expansion must be reduced.
• the laminate can warp (i.e. bend), or in extreme cases, delamination can occur due to differences in the expansion or contraction between the metal layer and the substrate. This is most commonly observed in laminates in which a copper layer adheres to both surfaces of a flat substrate. Initially, even though there may be stresses, there is no bending because the forces are the same on both surfaces. As copper is removed from one side of the laminate during subsequent processing, the laminate starts to bend, apparently because the stress forces differ on the two sides of the laminate.
• the strontium titanate/poly(phenylene sulfide) substrates have a coefficient of thermal expansion (CTE) greater than about 50 ppm/°C when less than 30% filler is included in the compositions, whereas the copper layer has a much lower CTE, about 16 ppm/°C. Reinforcement of the substrate with such materials as glass fiber or glass flake increases the tensile and thermal properties (i.e., heat distortion temperature), but the CTE is still greater than about 30 ppm/°C, and the improved tensile properties do not prevent bending.
• the use of mica, alumina, and/or magnesium titanate, as an additional filler increases the tensile properties and/or thermal (e.g. heat distortion temperature) properties of the substrate.
• the CTE is significantly reduced when mica, alumina, and/or magnesium titanate are included (e.g. to about 25 ppm/°C for some compositions).
• the mica, alumina, and/or magnesium titanate filler can be compounded with poly(phenylene sulfide) along with the high dielectric constant ceramic filler in the melt phase, as previously described, in either one step or two steps (i.e. sequentially).
• a twin screw extruder is preferred.
• Compounding of mica and/or alumina and the high dielectric ceramic with the polymer at the same time is the simplest and most economical method and is preferred.
• the mica and/or alumina and high dielectric constant ceramic filler e.g. SrTiO 3
• the dielectric laminates can be stacked and interconnected so that multiple layers are present. The layers may have different dielectric constants and different thickness, to form substrates for multichip modules and circuit boards.
• the high dielectric composites and laminates have many uses.
• sheets, films, plaques, and the like may all be used as substrates for making printed circuit boards that are useable at microwave frequencies.
• Other uses for flat substrates include high energy density capacitors, filters, antennas, buried components, and multichip modules.
• An application for which these materials are particularly useful is printed circuit antennas, such as microstrip, dipole, and patch antennas, for wireless equipment. These kinds of antennas are typically flat because the substrate is a ceramic, and their emitted signals and response to received signals are therefore directional. These materials can easily be made in curved or other shaped forms so that the directionality of the antenna response (either transmitting or receiving) can be modified as desired.
• rf printed (stripline or microstrip) rf and microwave circuit elements, such as transmission lines, inductors, capacitors, filters, (e.g. low pass filters, high pass filters, band pass filters, and band stop filters), signal couplers, branch line couplers, power splitters, signal splitters, impedance transformers, half wave and quarter wave transformers, and impedance matching circuits.
• filters e.g. low pass filters, high pass filters, band pass filters, and band stop filters
• signal couplers e.g. low pass filters, high pass filters, band pass filters, and band stop filters
• branch line couplers e.g. low pass filters, high pass filters, band pass filters, and band stop filters
• power splitters e.g. low pass filters, high pass filters, band pass filters, and band stop filters
• signal splitters e.g. low pass filters, high pass filters, band pass filters, and band stop filters
• branch line couplers e.g. low pass filters, high pass filters, band pass filters, and
• the pelletized compounds were then made into plaques (6" ⁇ 6" ⁇ 1/8" and 6" ⁇ 6" ⁇ 1/16" ) and 1 ⁇ 8" thick (2 - 2 1 ⁇ 2 " in diameter) discs by injection molding using DEMAG and BOY30M injection molding machines respectively at a melt temperature of about 300°C.
• the dielectric constants (D k ) and loss tangents of the plaques were measured as a function of frequency at room temperature (20°C).
• the dielectric constants and loss tangents at 1 MHz were measured using a Hewlett Packard HP 4192ALF Impedence Analyzer and HP 1645B dielectric fixture.
• the dielectric constants and loss tangents at 1 , 2, and 5 GHz were measured by the cavity resonance technique according to ASTM Test Method No. D2520, Method B. These data are presented in Table 1.
• the dielectric constant and loss tangent of poly(phenylene sulfide) at 1.0 GHz are 3.13 and 0.0021 respectively.
• the barium neodymium titanate has an approximate Ba:Nd atomic ratio of about 1 , with a small amount of bismuth ( ⁇ 10% compared with Ba or Nd), and enough Ti to make the titanate stoichiometry.
• the powder has a dielectric constant of about 92 at 1.0 GHz and a loss tangent of about 0.001 at 1.0 GHz.
• Two compounds were made, containing the barium neodymium titanate at the levels shown in Table 2. These were made into VB" thick discs that were about 2" - 21 ⁇ 2" in diameter.
• the high dielectric/low loss composites will be used as laminates in which a substrate, which may be a film, sheet, plaque, or the like, is laminated between two layers of copper film.
• Laminates are generally made by one of the following procedures:
• Tests were also carried out using copper foil that had been treated by the manufacturer to increase the roughness of the matte surface.
• the treated copper foil was sold as JTC Grade 3.
• the three layers (composite and foil) were placed under a pressure of about 55 psi under a vacuum (less than 100 Torr) in a static vacuum press and slowly heated over 50 minutes to a temperature of about 300°C, which is above the melt temperature of the polymer. The heating was stopped as soon as the sample reached 302°C, and the sample was then allowed to cool back down to about 65°C over a time of about 20 minutes.
• Adhesion is measured by a 180° pull test carried out according to the following method.
• the copper on the plaque is cut so that it can be peeled in one inch wide strips. Peeling of the strip from the plaque is started manually and is then continued while the resistance to peeling is measured. The peeling is carried out at an angle of 180° (i.e. parallel to the surface of the plaque) at a speed of 0.5 inches/minute.
• the adhesion is reported as the force per inch width of copper needed to peel the copper.
• the adhesion of the copper laminated to the poly(phenylene sulfide)/SrTiO 3 composites as described above was in the range of about 3.5 - 4.2 lbs/ inch using this method. Copper foil that had been subjected to a surface treatment that increased the surface roughness to improve adhesion (JTC Grade 3) was also laminated onto the composite plaques using the same method. The peel strength was much higher (greater than about 10 lbs/inch).
• Copper film also can be applied to the poly(phenylene sulfide)/ strontium titanate substrates by use of an adhesive.
• An adhesive that works well for this is C-Flex TM adhesive, which is available from
• the adhesive is applied between each of the two layers of copper foil and the two surfaces of the substrate.
• the copper and substrate are then heated under a pressure of about 140 psi at 204°C for one hour using the same static vacuum press that was utilized in Example 4(a).
• the adhesion was measured using the 180° pull test described above and was about 5-6 lbs/inch.
• a copper layer may also be applied by electroplating a substrate that has been modified to make electroplating feasible.
• copper can be applied by sputtering or vapor deposition.
• the layers made by sputtering and vapor deposition are normally very thin.
• the layers applied by electroplating can be made thick as well as thin.
• Laminates can also be made directly in one step by placing a copper film or sheet into the cavity of a mold and then injection molding a composition containing poly(phenylene sulfide) and one or more fillers into the mold.
• the copper film is held in place by using an adhesive tape (e.g. KAPTON ® film with adhesive on both sides).
• an adhesive tape e.g. KAPTON ® film with adhesive on both sides.
• an 8oz HPM injection molding machine with a 150 ton clamping capacity is used to make 6" ⁇ 6" ⁇ 0.125" laminates from either 1 ounce or 1 ⁇ 2 ounce JTC Grade 3 copper film from Gould, Inc. and poly(phenylene sulfide) containing SrTiO 3 and mica.
• Barrel temperature are set to achieve a melt temperature of 320°C.
• the temperatures of the mold halves are between 120°C and 140°C.
• a slow injection speed, corresponding to about 30% of the maximum capacity, is used to achieve the maximum balance of molded part properties and laminates appearance.
• the mold is injected at 4000 psi and is held under pressure at 3000 psi for 15 seconds.
• the part is allowed to cool for 40 seconds before being ejected from the mold.
• the cycle is completed is about 65 seconds
• Laminates can also be made directly from polymer and metal film by extruding the polymer to form one or more layers of film, co-feeding one or more layers of metal film, and pressing the metal film and freshly extruded polymer film which is still in a molten or softened state, to produce a laminate.
• the method is most typically used to apply a layer of metal film to both surfaces of a polymer film to make a polymer laminate with a metal layer on both sides. It can also be used to make a laminate with a metal layer on one surface or to make laminates having multiple layers of polymer and metal film.
• a composition containing 62% by volume of poly(phenylene sulfide), 14% by volume of SrTiO 3 , and 24% by volume of mica, described previously, is laminated to a layer of JTC Grade 3 copper foil (1 -ounce or 1 ⁇ 2-ounce) from Gould, Inc. as follows.
• the polymeric composition is dried in a vacuum dryer at 135°C for four hours. It is then fed through a gravity fed hopper into a single screw extruder with a 3.5" barrel diameter.
• the extruder barrel temperatures range from 280°C in the feed zone to 300°C in the metering zone.
• a melt pump is used to provide an even polymer flow to the die.
• the melt pump and melt lines are maintained at 300°C, while the die temperature is 310°C, and the gap between the die lips is1 ⁇ 8 inch, which produces a1 ⁇ 8 inch thick sheet.
• the melt web is extruded vertically downward between the first two rolls of a horizontal 3-roll stack.
• the chrome surfaced rolls have a diameter of 18" and the gap between rolls 1 and 2 is V ⁇ inch.
• the web follows a standard S-wrap and exits the roll stack in solid form.
• the roll temperatures are maintained at 70°C by circulating oil.
• a laminate having copper on one side is made by feeding a sheet of copper foil between the molten web and the middle roll of the 3-roll stack. Laminates having copper on both sides are made by feeding copper foil on both sides of the molten web.
• the laminated sheet then passes through a pair of rubber pull rolls and into a shear blade cutter, which chops the sheet into the desired length.
• the copper has good adhesion to the sheet.
• the moisture absorption of the material was measured as 0.01% by ASTM Method D570.
• the dielectric constant was measured in the machine direction (direction of flow during molding) and normal to the machine direction to determine whether there was any variation (i.e. anisotropy) of dielectric properties.
• the dielectric constant was the same (within 3%) in the two directions, indicating that there was little or no dielectric anisotropy.
• the temperature dependence of the dielectric constant of poly(phenylene sulfide)/strontium titanate sheet was measured over the temperature range of -50°C to 100°C.
• Two samples contained about 30% by volume of strontium titanate.
• the dielectric constant showed some variation with temperature, varying from about 10.5 at -50°C to about 9.8 at 100°C for one sample, and 10.1 at -50°C to 9.5 at 100°C, for the second sample.
• the dielectric constant of the two samples were about 10.1 and 9.7 respectively.
• the loss tangent varied more with temperature; for both samples, at -50°, the loss tangent was about 0.0014; at room temperature, the loss tangent was about 0.0020, and at 100°C, the loss tangent was about 0.0023.
• TICONTM55 strontium titanate powder (2.53 pounds), mica (0.766 pounds), and FORTON ® W205 poly(phenylene sulfide) powder (2.71 pounds) were compounded in a Brabender twin screw extruder, generally using the method of Examples 1 -3, to make a compound having 20% by volume strontium titanate, 10% by volume mica, and 70% by volume poly(phenylene sulfide).
• the mica was obtained from KMG Minerals, Inc., Kings Mountain, North Carolina 28086, and was designated L-140.
• the mica was in the form of platelets having an average particle size of about 70 microns.
• the die temperature of the extruder was 285° - 300°C, and the screw speed was 60 rpm.
• the compound of mica, strontium titanate, and poly(phenylene sulfide) was made into 1/16" thick plaques by the method of Examples 1-3.
• the plaques were then made into laminates by applying a film of either 1 ounce or 1 ⁇ 2 ounce JTC Grade 3 copper film, obtained from Gould Inc., to the plaques by the application of heat and pressure, following the method of Example 5 (a).
• Laminates based on other compositions of mica, strontium titanate, and polyphenylene sulfide were made, generally according to the method of Example 7.
• FORTRON ® W203 was used.
• a different grade of mica was used (L-135, having an average particle size of about 250 microns).
• Example 7 - 17 The plaques of Example 7 - 17 were then subjected to various tests to determine the dielectric and mechanical properties.
• the coefficient of thermal expansion (CTE) was measured according to ASTM E-831 -86 using a dynamic mechanical analyzer.
• the CTE of the plaque was measured in three directions: (1) The machine direction (also referred to as the flow direction or x-direction); (2) the transverse direction, perpendicular to the flow direction and in the plane of the plaque (also referred to as the y-direction); (3) perpendicular to the plane of the plaque (the z-direction).
• the flexural strength and flexural modules were measured using ASTM Method D790.
• the heat distortion temperature (HDT) under a 264 psi load was measured by ASTM Method D648.
• the dielectric constant and the loss tangent at 1 GHz were measured by the methods described in Examples 1 - 3.
• the moisture absorption of the plaque was measured by ASTM Method 570.
• the CTE values are much higher than those of the mica-filled compositions
• the flexural strengths and heat distortion temperatures are also higher than those of the mica-filled compositions, which had higher flexural modulus values
• the dielectric constants showed a greater anisotropy between the x and y directions than the mica-filled compositions.
• the loss tangents for the glass fiber-filled compositions were also higher than for the mica-filled compositions (0.0023 - 0.0031 for the glass fiber-filled compositions, compared with less than 0.0022 for all of the mica-filled composition).
• glass flake was also tested as a reinforcing filler.
• the glass flake was sold under the name Hammermilled FLAKEGLASTM 74 ⁇ 59647, and was obtained from Owens Corning, Huntington, PA The average particle diameter was 0 4mm Glass flake,
• SrTiO 3 SrTiO 3
• FORTRON W-205 poly(phenylene sulfide) were compounded in a twin screw extruder using the same general method described above.
• the compounds were made into plaques and laminates using the methods described above and subjected to the same tests.
• a compound of 62 volume % poly(phenylene sulfide), 18 volume% glass flake, and 20 volume % SrTiO 3 had CTE in the x, y and z directions of 30.2, 35 6 and 43-139 ppm/°C, measured over a temperature range of -30°C to 230°C
• the flexural strength and modulus of the plaques were 16.41 ksi and 1 74 Msi
• the heat distortion temperature was 209°C
• the dielectric constant was 7 34 and 7 47 in the x and y directions
• the loss tangent was 0 0031 and 0.0030 in the x and y directions.
• the Water Absorption was 0.02%.
• the CTE's in the x-y plane are lower (30.6 - 35.6) than with glass fiber, but still are higher than the CTE values of the mica-filled and alumina-filled compositions, which are generally less than 30.
• the physical properties (flexural modulus, heat distortion temperature) were somewhat improved over compositions with only SrTiO 3 .
• the flexural modulus values and heat distortion temperatures were much lower than those of the mica-filled compositions.
• the dielectric constant showed a greater anisotropy in the x and y directions than was observed for mica and SrTiO 3 .
• the loss tangent values for the glass flake-filled compositions were higher (0.0030 - 0.0031 ) than those of the mica-filled compositions (less than 0.0022).
• the alumina was calcined alumina, Realox Reactive Grade A- 3500, which has a median particle size of 3.6 microns.
• the alumina was low soda calcined alumina Grade A-10, which has a median particle size of 6-10 microns.
• the CTE in the z-direction is low and appears constant (within experimental error) with temperature over the range -30° to 80°C.
• the loss tangents were also low, with a maximum of 0.0029 in the examples.
• the dielectric constants of Examples 23, 24, and 25 were measured as a function of temperature and were constant (within experimental error). Over the temperature range of -40°C to 85°C, the dielectric constant of Example 23 averaged from 6.02 - 6.18, the dielectric constant of Example 24 ranged from 5.78 - 5.93, and the dielectric constant of Example 25 ranged from 6.60 - 6.88.
• compositions containing SrTiO 3 and mica also exhibit dielectric constants that are relatively unchanged with temperature.
• a disc was made from a composition of 62 volume % of FORTRON W205 poly(phenylene sulfide), 14 volume % of SrTiO 3 , and 24 volume % of mica.
• the dielectric constant ranged from 6.26 - 6.39 when measured at several temperatures from -40°C to 85°C.
• compositions were made having a dielectric constant of about 9 - 10, by the methods previously described.
• the compositions were made into 1 ⁇ 8" thick ⁇ about 2" diameter discs for testing of electrical properties and CTE.
• the compositions and results follow:
• Example 27 50 Volume % poly(phenylene sulfide) (PPS)/25 volume % SrTiO 3 /25 volume % Mica has a dielectric constant in the xy-plane of 9.31 , measured at 2 GHz at 20°C. There was no variation of the dielectric constant over the temperature range -40°C to 85°C within experimental error (measured values were 9.49 - 9.14). The loss tangent in the xy-plane at 2 GHz is 0.002, and the CTE in the z-direction is 32.92 ppm/°C.
• Example 28 50 Volume % PPS/ 25 volume % SrTiO 3 /25 volume % alumina has a dielectric constant in the xy-plane of 10.27, measured at 2 GHz at 20°C. There was no variation in the dielectric constant over the range -40°C to 85°C within experimental error (measured values 10.58 -10.16). The loss tangent in the xy-plane at 2 GHz is 0.002, and the CTE in the z-direction is 20.71 ppm/°C.
• Example 29 50 Volume % PPS/20 volume % SrTiO 3 /30 volume % alumina has a dielectric constant in the xy-plane of 9.07, measured at 2 GHz at 20°C. There was no variation in the dielectric constant over the temperature range of -40°C to 85°C within experimental error (measured values 8.98 - 9.30). The loss tangent at 2 GHz in the xy-plane is 0.0019, and the CTE in the z-direction is 21.01 ppm/°C.
• compositions were made in which MgTiO 3 (purchased from Tam Ceramics) was included as the added filler.
• Barium neodymium titanate (COG900MW, from Tam Ceramics) was the high dielectric filler in these examples.
• the compositions were made by melt blending, as previously described for other compositions.
• the blended compositions were made into 1 ⁇ 8" thick ⁇ 2" diameter discs for testing of electrical properties and CTE. The results follow:
• Example 30 A composition was made comprising 55 volume %
• the dielectric constant in the xy-plane was 6.81 at 20°C. There was no variation in the dielectric constant over the temperature range -40°C to 85°C within experimental error (measured values 6.87 - 6.81 ).
• the loss tangent in the xy-plane is 0.0015 at 2 GHz.
• the CTE in the z-direction is 24.56 ppm. °C.
• Example 31 The composition comprises 53 volume % PPS, 39 volume % MgTiO 3 , and 8 volume % barium neodymium titanate.
• the dielectric constant in the xy-plane at 20°C was 7.06. There was no variation in dielectric constant within experimental error over the temperature range -40°C to 85°C (measured values 6.99 - 7.12).
• the loss tangent in the xy-plane is 0.0015 at 2 GHz, and the CTE in the z-direction is 25.37 ppm/°C.
• the dielectric constant of compositions of SrTiO 3 and PPS without a second filler varies much more with temperature than that of compositions containing alumina and/or mica. (See Example 6).
• the low variation of dielectric constant with temperature for SrTiO 3 or barium neodymium titanate with either mica, alumina, or magnesium titanate, as a second filler in poly(phenylene sulfide) is useful for devices which may be exposed to a variety of temperatures (e.g. outdoor use).

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