Co-fired glass substrates for high frequency electronic packaging and methods of making

Abstract

A method of making a glass article using a phase separated silicate glass including a silica rich first phase and a boron rich second phase. The phase separated silica glass is etched with an etchant to remove at least a portion of the second phase and obtain a high silica content porous glass article. Vias may be formed in the porous glass article by first forming holes in the porous glass article and filling the holes with an electrically conductive material. The porous glass article may be heat treated to consolidate the porous glass article to close the pores of the porous glass article and obtain a consolidated glass article with very low dielectric properties. Various glass compositions are disclosed that phase separate via spinodal decomposition.

Description

CO-FIRED GLASS SUBSTRATES FOR HIGH FREQUENCY ELECTRONIC PACKAGING AND METHODS OF MAKINGCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63 / 524732 filed on July 3, 2023, the content of which is relied upon and incorporated herein by reference in its entirety.FIELD

[0002] The disclosure generally relates to glass substrates for high frequency electronic packaging using glasses having at least two distinct glass phases.BACKGROUND

[0003] Digital technologies continue to expand, particularly regarding data connectivity and processing rates. For example, processing rates on the order of 1 gigabits per second (Gbits / s) are expanding to rates at tens of Gbits / s. The corresponding electronic device technology needed to achieve these data rates likely will result in an expansion of signal transmission and receiving frequencies on the order of 1 GHz up to about 100 GHz.

[0004] As these signal frequencies increase to accommodate an increase in data processing rates, the technical specifications and requirements relating to absorption loss associated with the insulating materials employed in these devices take on greater importance. While there are materials available having low loss tangents at frequencies greater than 10 GHz, the processing characteristics of these materials can limit their ability to be manufactured using certain forming processes.

[0005] There are commercially available materials used as insulating layers in printed circuit boards (PCBs). For example, one common glass-epoxy laminate used as an insulating layer in PCB applications has a loss tangent of 0.0058 at signal frequencies of 10 GHz. However, this insulating laminate has a limiting loss tangent as the industry moves to higher and higher signal frequencies. Other laminates, such as fused silica-polymer laminates, have been found thatexhibit low loss characteristics at frequencies of 10 GHz or more. However, the mechanical properties of fused silica and polymer layers limit the use of these laminates in some processes, as the fused silica layer may crack during post processing.

[0006] Materials such as Radome pyroceramics, high purity fused silica, sapphire, alumina, and silica, may have low loss tangents at frequencies greater than 10 GHz. However, these materials may have such high viscosities at forming temperatures that their ability to be processed using standard sheet forming processes, such as slot-draw and overflow down draw (e.g., fusion), may be limited. There are also alkali-free glass and glass-ceramic materials that have low loss tangents at frequencies greater than 10 GHz, examples of which include B2O3- P2O5-S1O2 (BPS) and MgO-AhCh-SiCh (MAS) systems. However, these systems typically have a liquidus viscosity too low for common forming methods.SUMMARY

[0007] In a first aspect, a method of making a glass article is disclosed comprising exposing at least one spinodally phase separated glass substrate comprising a majority SiCh first phase and a second phase comprising B2O3 to an acid solution comprising about 5 weight percent (wt%) to about 40 wt% of an acid at a temperature in a range from about 60°C to about 95°C for a time in a range from about 8 hours to about 24 hours to remove at least a portion of the second phase from the at least one spinodally phase separated glass substrate and obtain at least one porous glass substrate comprising a total Si O2 content greater than about 95 mol%. The method also comprise forming a plurality of holes in the at least one porous glass substrate and depositing an electrically conductive material in the plurality of holes to form an intermediate circuit board comprising a plurality of vias. The method may further comprise consolidating the intermediate circuit board to form the glass circuit board. After the consolidating the glass circuit board comprises amorphous glass. In some embodiments, the step of forming the plurality of holes may be performed prior to the step of exposing the least one spinodally phase separated glass substrate to the acid solution, i.e., prior to obtaining the porous glass substrate.

[0008] In a second aspect, the acid solution of the first aspect may comprise at least one of HC1, H2SO4, HNO3, HF, or H3PO4.

[0009] In a third aspect, the acid solution of the first aspect or the second aspect may comprise HC1.

[0010] In a fourth aspect, the acid solution of any one of the first aspect to the third aspect may comprise about 5 wt% HC1.

[0011] In a fifth aspect, the acid solution of the first aspect may comprise at least one of citric acid or acetic acid.

[0012] In a sixth aspect, an open porosity of the at least one porous glass substrate of any one of the first aspect to the fifth aspect may be greater than about 28%.

[0013] In a seventh aspect, the forming the plurality of holes of any one of the first aspect to the sixth aspect may comprise laser ablation or chemical etching.

[0014] In an eighth aspect, the forming the plurality of holes of the seventh aspect may comprise an RF -excited CO2 laser.

[0015] In a ninth aspect, the forming the plurality of holes of any one of the seventh aspect may comprise using a laser operating at an ultraviolet wavelength.

[0016] In a tenth aspect, the first aspect may comprise, prior to the consolidating, further depositing the electrically conductive material on the porous glass substrate as a line between a first via of the plurality of vias and a second via of the plurality of vias.

[0017] In an eleventh aspect, the heat treating of any one of the first aspect to the fifth aspect may further comprise heat treating the intermediate circuit board at a temperature in a range from about 500°C to about 700°C for a time in a range from about 45 minutes to about 75 minutes.

[0018] In a twelfth aspect, the consolidating of any one of the first aspect to the fifth aspect may comprise heating the intermediate circuit board to a consolidation temperature in a range from about 850°C to about 1250°C, such as in a range from about 900°C to about 1100°C, for a time in a range from about 1 hour to about 24 hours.

[0019] In a thirteenth aspect, the at least one spinodally phase separated glass substrate of the first aspect may comprise a plurality of spinodally phase separated glass substrates, the exposing resulting in a plurality of porous glass substrates, the method further comprising forming the plurality of holes in at least a subset of the plurality of porous glass substrates, depositing the electrically conductive material in the plurality of holes of the at least the subset of porous glass substrates to obtain a plurality of intermediate circuit boards, arranging the plurality of porous glass substrates and the plurality of intermediate circuit boards to form a stack, and consolidating the stack to form the glass circuit board.

[0020] In a fourteenth aspect, the stack of the thirteenth aspect may be positioned between a pair of thermally conductive substrates prior to the consolidating.

[0021] In a fifteenth aspect, the pair of thermally conductive substrates of the fourteenth aspect may comprise SiC.

[0022] In a sixteenth aspect, the glass circuit board of any one of the first aspect to the fifteenth aspect may comprise, on an oxide basis greater than about 95% mol% SiCh, less than about 1 mol% AI2O3, and less than about 3 mol% B2O3.

[0023] In a seventeenth aspect, the glass circuit board of any one of the first aspect to the sixteenth aspect may comprise one or more alkaline earth oxides (RO) totaling less than 0.5 mol%, wherein RO is at least one of MgO, CaO, SrO, or BaO.

[0024] In an eighteenth aspect, a dielectric constant Dk of the glass circuit board of any one of the first aspect to the seventeenth aspect may be less than about 6.0 when measured at 10 GHz

[0025] In a nineteenth aspect, the Dk of the eighteenth aspect is less than about 4.0 when measured at 10 GHz.

[0026] In a twentieth aspect, a loss tangent Df of the at least one glass circuit board of any one of the first aspect to the nineteenth aspect may be less than about 0.001 when measured at 30 GHz.

[0027] In a twenty first aspect, the Df of the twentieth aspect may be less than about 0.001 when measured at 10 GHz.

[0028] In a twenty second aspect, the spinodally phase separated glass substrate of the first aspect comprises a total amount of SiCh from about 59 mol% to about 69 mol%, a total amount of AI2O3 from about 3 mol% to about 13 mol%, a total amount of B2O3 from about 9.8 mol% to about 20 mol%, and one or more alkaline earth oxides (RO) totaling from about 3.9 mol% to about 11.5 mol%, wherein RO is selected from MgO, CaO, SrO, and BaO

[0029] In a twenty third aspect, B2O3 / (AhO3 + SiO2) of the spinodally phase separated glass substrate of the twenty second aspect may be in a range from about 0. 12 to about 0.3.

[0030] In a twenty fourth aspect, the spinodally phase separated glass substrate of the twenty second aspect may comprise SiO2 in a range from about 68.0 mol% to about 69.0 mol%.

[0031] In a twenty fifth aspect, the spinodally decomposed glass substrate of the first aspect may comprise, on an oxide basis, a total amount of SiCh from about 57 mol% to about 70 mol%, a total amount of AI2O3 from about 4.7 mol% to about 10.5 mol%, a total amount of B2O3 from about 11.2 mol% to about 15.2 mol%, atotal amount of ZnO from about 1.2 mol% to about 7.4 mol%, and one or more alkaline earth oxides (RO) totaling from about 3.7 mol% to about 20 mol%, wherein RO is selected from MgO, CaO, SrO, and BaO.

[0032] In a twenty sixth aspect, the glass of the twenty fifth aspect may comprise SnO in a range from about 0.09 mol% to about 0.15 mol%.

[0033] In a twenty seventh aspect, the spinodally phase separated glass substrate of the twenty sixth aspect may comprise MgO in a range from about 1.5 mol%to about 9.6 mol%.

[0034] In a twenty eight aspect, MgO / ZnO of the spinodally phase separated glass substrate of the twenty seventh aspect may be in a range from about 0 to about 3.7.

[0035] In a twenty ninth aspect, EhCh / ZnO of the spinodally phase separated glass substrate of the twenty seventh aspect may be in a range from about 1.6 to about 12.6.

[0036] In a thirtieth aspect, a glass circuit board is disclosed, comprising greater than about 95% mol% SiCh, less than about 1 mol% AI2O3, less than about 3 mol% B2O3, a plurality of vias disposed in the glass circuit board, and wherein a dielectric constant Dk of the glass circuit board is less than about 6.0 when measured at 10 GHz.

[0037] In a thirty first aspect, the plurality of vias of the thirtieth aspect may comprise a first via and a second via, and an electrically conductive material is disposed on the glass circuit board as a line extending between the first via and the second via such that the electrically conductive material forms an electrical pathway between the first via and the second via.

[0038] In a thirty second aspect, the glass circuit board of the thirtieth aspect may comprise a first major surface and a second major surface opposite the first major surface, the plurality of vias comprises a first via extending from the first major surface partially through a thickness of the glass circuit board and a second via extending from the second major surface partially through the thickness of the glass circuit board, and an electrically conductive material forms an electrical pathway between the first via and the second via.

[0039] In a thirty third aspect, wherein the electrically conductive material of the thirtieth aspect to the thirty first aspect may be positioned within an interior of the glass circuit board.

[0040] In a thirty fourth aspect, wherein the plurality of vias of the thirtieth aspect to the thirty first aspect may comprise a third via, and the electrical pathway is in electrical communication with the third via.

[0041] In a thirty fifth aspect, the plurality of vias of the thirtieth aspect may comprise at least one blind vias.

[0042] In a thirty sixth aspect, a loss tangent Df of the glass circuit board of any one of the thirtieth aspect to the thirty fifth aspect may be less than about 0.001 when measured at 30 GHz.

[0043] In a thirty seventh aspect, the Df of the thirty sixth aspect may be equal to or less than about 0.0005 when measured at 10 GHz.

[0044] In still another aspect, a method of making a glass circuit board is disclosed, comprising forming a plurality of holes in at least one spinodally phase separated glass substrate comprising a first major surface, a second major surface opposite the first major surface, and a thickness therebetween, the at least one spinodally phase separated glass substrate further comprising a majority SiCh first phase and a second phase comprising B2O3, and wherein each hole of the plurality of holes extends through the thickness of the spinodally phase separated glass substrate. The method further comprises exposing the at least one spinodally phase separated glass substrate to an acid solution comprising about 5 wt% to about 40 wt% of an acid at a temperature in a range from about 60°C to about 95 °C for a time in a range from about 8 hours to about 24 hours to remove at least a portion of the second phase from the at least one spinodally phase separated glass substrate, and wherein after the exposing a total SiC>2 content of the spinodally phase separated glass substrate is greater than about 95 mol%, depositing an electrically conductive material in the plurality of holes to form an intermediate circuit board comprising a plurality of vias, and consolidating the intermediate circuit board to form the glass circuit board.

[0045] In aspects, the acid solution may comprise at least one of HC1, H2SO4, HNO3, HF, or H3PO4. For example, the acid solution may comprise HC1, such as about 5 wt% HC1.

[0046] In other aspects, the acid solution may comprise at least one of citric acid or acetic acid.

[0047] In aspects, an open porosity of the at least one spinodally phase separated glass, not including porosity derived from the holes, after the exposing can be greater than about 28%.

[0048] In aspects, the forming the plurality of holes may comprise laser ablation or chemical etching.

[0049] In some aspects, the forming the plurality of holes may comprise using an RF -excited CO2 laser.

[0050] In other aspects, the forming the plurality of holes may comprise using a laser operating at an ultraviolet wavelength.

[0051] In some embodiments, the depositing the electrically conductive material may comprise depositing the electrically conductive material as a line between a first via of the plurality of vias and a second via of the plurality of vias prior. For example, the depositing the electrically conductive material as a line is performed prior to consolidating the intermediate circuit board.

[0052] In embodiments, the method may further comprise heat treating the intermediate circuit board at a temperature in a range from about 500°C to about 700°C for a time in a range from about 45 minutes to about 75 minutes.

[0053] In embodiments, the consolidating comprises heating the intermediate circuit board to a consolidation temperature in a range from about 850°C to about 1250°C for a time in a range from about 1 hour to about 24 hours.

[0054] In aspects, the at least one spinodally phase separated glass substrate may comprise a plurality of spinodally phase separated glass substrates, the method further comprising forming the plurality of holes in at least a subset of the plurality of the spinodally phase separated glass substrates, depositing the electrically conductive material in the plurality of holes of the at least the subset of spinodally phase separated glass substrates to obtain a plurality of intermediate circuit boards, arranging the plurality of intermediate circuit boards to form a stack of intermediate circuit boards, and wherein the consolidating comprises consolidating the stack of intermediate circuit boards to form the glass circuit board.

[0055] The stack of intermediate circuit boards may be positioned between a pair of thermally conductive substrates prior to the consolidating, such as a pair of thermally conductive substrates comprising SiC.

[0056] The method may further comprise delivering a molten material to a forming body, drawing a glass ribbon from the forming body, and separating the spinodally phase separated glass substrate from the glass ribbon. The molten material may comprise a 35,000 Poise Temperature greater than about 1250°C. For example, the glass ribbon may be formed in a fusion downdraw apparatus, wherein the forming body comprises a pair of converging forming surface that join along a bottom edge of the forming body where the converging forming surfaces converge.

[0057] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0058] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description explain principles and operation of the various embodiments.BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1 is a schematic drawing of an exemplary fusion downdraw glass manufacturing apparatus;

[0060] FIG. 2 is a photo of an exemplary phase separated glass in accordance with the present disclosure;

[0061] FIG. 3 is a plot representing x-ray diffraction (XRD) data showing no crystallization in the glass, verifying the phase separation is between two glass phases;

[0062] FIG. 4 is a plot showing optical transmission for two glasses, a commercially available, non-phase separated glass (Coming® Eagle XG®) and an exemplary phase separated glass, as a function of wavelength;

[0063] FIG. 5 is a plot showing reflectance between Coming Eagle XG and the exemplary phase separated glass of FIG. 4 as a function of wavelength;

[0064] FIG. 6 is (a) a strain scope image of an as-drawn sample of the exemplary phase separated glass of FIG. 4 and (b) a photograph of an SEM image of the exemplary phase separated glass;

[0065] FIG. 7 is (a) a strain scope image of the exemplary phase separated glass sample of FIG. 4 after heat treatment at 720°C for 2 hours and (b) a photograph of an SEM image of the exemplary phase separated glass after the heat treatment;

[0066] FIG. 8 is (a) a strain scope image of the exemplary phase separated glass sample of FIG. 7 after a second heat treatment at 720°C for 2 hours and (b) a photograph of an SEM image of the same exemplary phase separated glass sample after the second heat treatment;

[0067] FIG. 9 is a photograph of an SEM image of a sample of the exemplary phase separated glass of FIG. 4 after heat treatment at 745°C for 24 hours;

[0068] FIG. 10 a photograph of an SEM image of a sample of the exemplary phase separated glass of FIG. 4 after heat treatment at 800°C for 24 hours;

[0069] FIG. I l a photograph of an SEM image of a sample of the exemplary phase separated glass of FIG. 4 after heat treatment at 850°C for 24 hours;

[0070] FIG. 12 a photograph of an SEM image of a sample of the exemplary phase separated glass of FIG. 4 after heat treatment at 900°C for 24 hours;

[0071] FIG. 13 is schematic representation of a coordinate system used to evaluate the Fourier transform of data from a phase separated glass;

[0072] FIG. 14 is two-dimensional Fourier transform (2DFT) corresponding to a sample measured from an x surface;

[0073] FIG. 15 are Fourier transform data for three surfaces of an exemplary phase separated glass sample plotted in an r0 coordinate system, where (a) represents the x cross-section, (b) represents the y cross-section, and (c) represents the z cross-section;

[0074] FIG. 16 is schematic representation of a glass sheet showing points along the edge portions of the glass sheet where stress measurements were obtained;

[0075] FIG. 17 is a plot showing comer stress in the glass sheet of FIG. 16 as the glass composition was transitioned during the manufacturing process from a commercially available glass (Coming Eagle XG) to an exemplary phase separated glass, and showing a gradual increase in stress over the transition period;

[0076] FIG. 18 is a plot showing the loss tangent of exhibited by glass formed from a commercially available non-phase separable glass composition to an exemplary phase separable glass composition as a function of time and shows a gradual decrease in loss tangent;

[0077] FIG. 19 is a plot showing stress in a glass sheets produced from molten glass as the ratio (B2O3 + MgO) / CaO (calculated with wt%) in the molten glass varied during a transition from a commercially available non-phase separable glass composition to an exemplary phase separable glass composition as a function of time;

[0078] FIG. 20 is a plot of dielectric constant as a function of replacement of MgO with ZnO for an exemplary phase separated glass;

[0079] FIG. 21 is a plot of loss tangent as a function of replacement of MgO with ZnO for the exemplary phase separated glass of FIG. 20;

[0080] FIG. 22 is a plot of dielectric constant as a function of replacement of MgO with ZnO for an exemplary phase separated glass as a function of total RO (or R2O) in exemplary phase separated glass with ZnO replacing B2O3;

[0081] FIG. 23 is a plot of loss tangent as a function of replacement of MgO with ZnO for the exemplary phase separated glass of FIG. 22 as a function of total RO (or R2O) in exemplary phase separated glass with Zn replacing B2O3;

[0082] FIG. 24 is a plot of resistivity as a function of temperature (°C) for GS57 and GS17 resistivity;

[0083] FIG. 25 is a plot of dielectric constant as a function of mol% La2O3 when La2O3 is substituted for BaO in glass composition GS72;

[0084] FIG. 26 is a plot of loss tangent as a function of mol% La2C>3 when La2O3 is substituted for Ba in glass composition GS72;

[0085] FIG. 27 is a plot of dielectric constant as a function of mole% La2Os or Y2O3 when added on top of an exemplary phase separable glass composition, an Sr-Ba containing alumino- borosilicate glass;

[0086] FIG. 28 is a plot of loss tangent as a function of mole% La2Os or Y2O3 when added on top of an exemplary phase separable glass composition, an Sr-Ba containing alumino- borosilicate glass;

[0087] FIG. 29 is a plot of Dk at 10 GHz as a function of mol% transition metal oxide when added as a replacement for CaO in glass composition;

[0088] FIG. 30 is a plot of Dr at 10 GHz as a function of mol% transition metal oxide when added as a replacement for CaO in glass composition GS 17;

[0089] FIG. 31 Dk at 10 GHz as a function of mole% F- when added as a replacement for B2O3 in glass composition GS 17;

[0090] FIG. 32 Df at 10 GHz as a function of mole% F- when added as a replacement for B2O3 in glass composition GS 17.

[0091] FIG. 33 shows a series of photos of holes formed by the UV laser before and after thermal consolidation;

[0092] FIG. 34 shows x-ray diffraction patterns (intensity in counts as a function of degrees (2 theta)) on the consolidated substrate of FIG. 33;

[0093] FIG. 35 is a perspective view of a first intermediate circuit board and a second intermediate circuit board that may be arranged into a stack of intermediate circuit boards (shown separated for ease of viewing);

[0094] FIG. 36 is a cross-sectional edge view of a stack of intermediate circuit boards positioned between two thermally conductive substrates;

[0095] FIG. 37 is atop view of a glass circuit board formed from the stack intermediate circuit boards of FIG. 35; and

[0096] FIG. 38 is a cross-sectional view of the glass circuit board of FIG. 37 shown along line 38-38.DETAILED DESCRIPTION

[0097] In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of various principles of the present disclosure. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that thepresent disclosure may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of various principles of the present disclosure. Finally, wherever applicable, like reference numerals refer to like elements.

[0098] Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0099] Unless otherwise specified, all compositions are expressed in terms of as-batched (i.e., constituent content) mole percent (mol%). As will be understood by those having ordinary skill in the art, various melt constituents (e.g., fluorine, alkali metals, boron, etc.) may be subject to different levels of volatilization (e.g., as a function of vapor pressure, melt time and / or melt temperature) during melting of the constituents. As such, the term “about,” in relation to such constituents, is intended to encompass values within about 1 mol% when measuring final articles as compared to the as-batched compositions provided herein. With the forgoing in mind, substantial compositional equivalence between final articles and as-batched compositions is expected.

[0100] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.

[0101] A variety of processes may be used to form glass articles described herein including, without limitation, fusion processes, slot-draw processes, and float glass processes.

[0102] As used herein, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a “component”includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0103] The term “CTE,” as used herein, refers to the coefficient of thermal expansion of a glass material, element or the like in the disclosure as averaged over a temperature range from 20°C to 300°C, unless otherwise specified.

[0104] The term “dielectric constant (Dk)” refers to the dielectric constant of a glass structure, design, or article of the disclosure. Unless otherwise indicated, dielectric properties were measured at 10 GHz.

[0105] As used herein, amorphous (an amorphous material) means a non-crystalline material having no long-range atomic order. That is, the material may exhibit short range atomic order that extends for about 1 to 2 atomic spacings beyond a reference atom, but not much beyond such spacing

[0106] For brevity, ranges of values disclosed herein, including compositional ranges or attribute (performance) ranges, or series of ranges, may be appended by the phrase “including all ranges and subranges therebetween,” which is to be interpreted as including whole number or decimal subranges as though explicitly presented. Thus, by way of example, a range between 6 and 8 (units omitted) implicitly includes a subrange between 6.4 and 8, or a subrange between 6 and 7.2, or a subrange between 6 and 7, and so forth. Additionally, a series of ranges, such as “in a range from 6 to 11 or in a range from 6 to 8” implicitly includes a range from 7 to 10, or subranges therebetween, such as 7.2 to 10.4, as though explicitly presented, provided the range does not exceed the minimum or maximum endpoints of the explicitly presented range or series of ranges. Thus, for example, “in a range from 6 to 11 or in a range from 6 to 8” has as endpoints 6 and 11.

[0107] The term “loss tangent” as used herein refers to the inherent dissipation of electromagnetic energy (e.g., heat) afforded by a particular glass, layer, or laminated structure associated with aspects of this disclosure. The lower the dielectric loss (e.g. , portion of energy lost as heat), the more effective the dielectric material is. The dielectric loss can be parameterized in terms of either the loss angle 3 or the corresponding loss tangent, tan 3. Permittivity is the ability of a substance, such as glasses of the disclosure, to store electrical energy in the presence of an external electric field. Permittivity is a complex quantity because it describes the phase and magnitude of polarization in relation to an oscillating field. The terms “dielectric constant (Dk)” and “relative permittivity (£>)” are used interchangeably in the disclosure and are defined as the ratio between the real part of the complex permittivity(absolute permittivity, s) and permittivity of free space (vacuum permittivity, sO). Materials with an ;.> > I are considered to be dielectric materials and poor conductors of electricity. Materials with low dielectric constants can withstand more intense electrostatic fields without having a dielectric breakdown. Dielectric breakdown results in the material conducting a electrical current which, in most solid materials, can result in damage to the material. The “loss tangent” is expressed as the ratio between the imaginary and real part of the complex permittivity. In general, the dielectric constant and loss tangent of a material are dependent on the frequency of the external field. Therefore, the dielectric property measured in the kHz range may not represent the dielectric property at microwave frequencies. Further, unless otherwise noted, the “loss tangent” and “dielectric constant (Dk)” attributes of the glasses of the present disclosure can be measured at frequencies of 1 GHz or greater according to a split post dielectric resonator (SPDR) or an open-cavity resonator configuration according to techniques as understood by those with ordinary skill in the field of the disclosure. The particular method chosen can be selected based on the sample thickness and its lateral dimensions.

[0108] As used herein, molten glass refers to a molten material formed by heating batch materials in a melting vessel, the molten glass having a viscosity in a range from about 1 kiloPoise (kP or kPoise) to about 200 kPoise.

[0109] As used herein, spinodal decomposition refers to a phase transformation in which a material, e.g., a glass material, having a single thermodynamic phase, separates, for example spontaneously, into multiple coexisting but separate phases, for example two phases, without nucleation. The separate phases may be dispersed throughout the glass and interconnected. The separate phases may exist in approximately equal proportions and occupy approximately equal volumes. Accordingly, the term “phase separated glass,” as used herein, refers to a glass that has undergone spinodal decomposition to produce a glass with at least two stable, interconnected phases, wherein the interconnected second phase is dispersed throughout the interconnected first phase. One phase (e.g., the first or primary phase) may be enriched with a first chemical species (e.g., SiO2) and the second (e.g., secondary) phase may be enriched with a second chemical species (e.g., B2O3). That is, the first phase may, for example, include predominately all SiO2, while the second phase includes predominately all B2O3. That is, by way of example, the first phase may comprise a majority SiO2 whereas the second phase may comprise a majority B2O3. The term “majority” here means greater than 50 mol%.

[0110] As used herein, consolidation, also referred to as firing (e.g., to consolidate), refers to a process by which a porous material is subjected to heating conditions appropriate to bring the material to at least a softening temperature, e.g., a melting temperature, whereby the pores of the porous material close and the material ceases to be porous and becomes a solid article, e.g., a solid glass article without pores distributed throughout.

[0111] Glasses and glass articles of the present disclosure may be suitable for electronic devices, electronic device substrates, and other comparable applications that enable higher frequency communication in devices without a significant reduction in performance as it relates to other non-electrical device requirements. For instance, as higher frequency communication signals are used in these devices, the signals must pass through various physical barriers that otherwise attenuate or block these signals. As such, glasses and / or glass articles of the present disclosure can be well-suited for use as these physical barriers. Examples of these physical barriers include electrically insulating substrates used in the fabrication of electronic circuits and signal transmission structures, electronic device covers, and other related structures that can be employed to house electronic circuits and other electronic device components employed in electronic devices operating at high signal frequencies.

[0112] In some embodiments, glasses of the present disclosure may be suitable for use as substrates in PCBs. A PCB typically includes an insulating layer laminated with a conductive film. In some implementations, glasses of the present disclosure can be characterized by a low loss tangent and mechanical properties suitable for use as the insulating layer in a PCB, optionally in combination with one or more polymeric substrate layers. Optionally, glasses of the present disclosure can be substantially free of alkali metals to decrease the likelihood of ion migration into electronic components (e.g., thin film transistors) during processing of the circuit board.

[0113] Some aspects of the present disclosure also relate to glasses having properties suitable for manufacturing, for example slot-draw processes and overflow fusion drawing processes. The fusion draw process is an industrial technique that has been used for large-scale manufacture of thin glass sheets, e.g., sheets having a thickness less than about 3 mm, for example less than about 1 mm, less than about 0.7 mm, or even less than about 0.1 mm. Compared to other flat glass manufacturing techniques, such as the float or slot draw processes, the fusion draw process yields thin glass sheets with high flatness and surface quality. As a result, the fusion draw process is often a desired manufacturing technique in the fabrication ofthin glass substrates (e.g., for liquid crystal displays, as well as for cover glass for various personal electronic devices).

[0114] Shown in FIG. 1 is an exemplary fusion glass manufacturing apparatus 10. Glass manufacturing apparatus 10 comprises a glass melting furnace 12 including a melting vessel 14. In addition to melting vessel 14, glass melting furnace 12 may optionally include one or more additional components such as heating elements (e.g., combustion burners and / or electrodes) configured to heat raw material and convert the raw material into a molten material, hereinafter, molten glass. For example, melting vessel 14 may be an electrically boosted melting vessel, wherein energy is added to the raw material through both combustion burners and by direct heating, wherein an electrical current is passed through the raw material, the electrical current thereby adding energy via Joule heating of the raw material.

[0115] Glass melting furnace 12 may include other thermal management devices (e.g., thermal insulation components) that reduce heat loss from the melting vessel. Glass melting furnace 12 may include electronic and / or electromechanical devices that facilitate melting of the raw material into a glass melt. Glass melting furnace 12 may include support structures (e.g., support chassis, support member, etc.) or other components.

[0116] Melting vessel 14 can be formed from a refractory material, for example a refractory ceramic material comprising alumina or zirconia, although the refractory ceramic material can comprise other refractory materials, such as yttrium (e.g., yttria, yttria-stabilized zirconia, yttrium phosphate), zircon (ZrSiO-i) or alumina-zirconia-silica or even chrome oxide, used either alternatively or in any combination. In some examples, melting vessel 14 may be constructed from refractory ceramic bricks.

[0117] Glass melting furnace 12 may be incorporated as a component of a glass manufacturing apparatus configured to fabricate a glass article, for example a glass ribbon, although the glass manufacturing apparatus can be configured to form other glass articles without limitation, such as glass rods, glass tubes, glass envelopes (for example, glass envelopes for lighting devices, e.g., light bulbs), and glass lenses. In some examples, glass melting furnace 12 may be included in a glass manufacturing apparatus comprising a slot draw apparatus, a float bath apparatus, a down-draw apparatus (e.g., a fusion down-draw apparatus), an up-draw apparatus, a pressing apparatus, a rolling apparatus, a tube drawing apparatus or any other glass manufacturing apparatus that would benefit from the present disclosure. By way of example, FIG. 1 schematically illustrates glass melting furnace 12 as a component of a fusion down-draw glass manufacturing apparatus 10 for fusion drawing a glass ribbon forsubsequent processing into individual glass sheets or rolling the glass ribbon onto a spool. As used herein, fusion drawing comprises flowing molten glass over inclined, e.g., converging, side surfaces of a forming body, wherein the resulting streams of molten material join, or “fuse,” at the bottom of the forming body to form a glass ribbon.

[0118] Glass manufacturing apparatus 10 may optionally include an upstream glass manufacturing apparatus 16 positioned upstream of melting vessel 14. In some examples, a portion of, or the entire upstream glass manufacturing apparatus 16, can be incorporated as part of the glass melting furnace 12.

[0119] As shown in FIG. 1, upstream glass manufacturing apparatus 16 may include a raw material storage bin 18, a raw material delivery device 20, and a motor 22 connected to raw material delivery device 20. Raw material storage bin 18 may be configured to store raw material 24 that can be fed into melting vessel 14 of glass melting furnace 12 through one or more feed ports, as indicated by arrow 26. Raw material 24 typically comprises one or more glass forming metal oxides and one or more modifying agents. In some examples, raw material delivery device 20 may be powered by motor 22 to deliver a predetermined amount of raw material 24 from raw material storage bin 18 to melting vessel 14. In further examples, motor 22 may power raw material delivery device 20 to introduce raw material 24 at a controlled rate based on a level of molten glass sensed downstream from melting vessel 14 relative to a flow direction of the molten glass. Raw material 24 within melting vessel 14 can thereafter be heated to form molten glass 28. Typically, the raw material is added to the melting vessel as particulate, for example as various “sands.” Raw material 24 may also include scrap glass (i.e., cullet) from previous melting and / or forming operations. Combustion burners may be used to begin the melting process. In an electrically boosted melting process, once the electrical resistance of the raw material is sufficiently reduced by the combustion burners, electric boost can begin by developing an electrical potential between electrodes positioned in contact with the raw material, thereby establishing an electrical current through the raw material, the raw material typically entering, or in, a molten state.

[0120] Glass manufacturing apparatus 10 may also include a downstream glass manufacturing apparatus 30 positioned downstream of glass melting furnace 12 relative to a flow direction of molten glass 28. In some examples, a portion of downstream glass manufacturing apparatus 30 may be incorporated as part of glass melting furnace 12. For instance, first connecting conduit 32 discussed below, or other portions of the downstream glass manufacturing apparatus 30, may be incorporated as part of the glass melting furnace 12.

[0121] Downstream glass manufacturing apparatus 30 may include a first conditioning chamber, such as fining vessel 34, located downstream from melting vessel 14 and coupled to melting vessel 14 by way of the above-referenced first connecting conduit 32. In some examples, molten glass 28 may be gravity fed from melting vessel 14 to fining vessel 34 by way of first connecting conduit 32. Accordingly, first connecting conduit 32 provides a flow path for molten glass 28 from melting vessel 14 to fining vessel 34. However, other conditioning chambers may be positioned downstream of melting vessel 14, for example between melting vessel 14 and fining vessel 34. In some embodiments, a conditioning chamber may be employed between the melting vessel and the fining chamber. For example, molten glass from a primary melting vessel can be further heated in a secondary melting (conditioning) vessel or cooled in the secondary melting vessel to a temperature lower than the temperature of the molten glass in the primary melting vessel before entering the fining chamber.

[0122] Bubbles may be removed from molten glass 28 by various techniques. For example, raw material 24 may include multivalent compounds (i.e., fining agents) such as tin oxide that, when heated, undergo a chemical reduction reaction and release oxygen. Other suitable fining agents can include without limitation arsenic, antimony, iron, and / or cerium, although the use of arsenic and antimony, owing to their toxicity, may be discouraged for environmental reasons in some applications. Fining vessel 34 is heated, for example to a temperature greater than the melting vessel interior temperature, thereby heating the fining agent to a sufficient reaction temperature for chemical reduction. Oxygen produced by the temperature -induced chemical reduction of one or more fining agents included in the molten glass can diffuse into gas bubbles produced during the melting process. The enlarged gas bubbles with increased buoyancy then rise to a free surface of the molten glass within the fining vessel and are thereafter vented from the fining vessel, for example through a vent tube in fluid communication with the atmosphere above the free surface.

[0123] Downstream glass manufacturing apparatus 30 may further include another conditioning chamber, such as mixing apparatus 36, for example a stirring vessel, for mixing the molten glass that flows downstream from fining vessel 34. Mixing apparatus 36 can be used to provide a homogenous glass melt composition, thereby reducing chemical and / or thermal inhomogeneities that may otherwise exist within the molten glass exiting the fining vessel. As shown, fining vessel 34 may be coupled to mixing apparatus 36 by way of a second connecting conduit 38. Accordingly, molten glass 28 can be gravity fed from the fining vessel 34 to mixing apparatus 36 through second connecting conduit 38. Typically, the molten glasswithin mixing apparatus 36 includes a free surface, with a free (e.g., gaseous) volume extending between the free surface and a top of the mixing apparatus. While mixing apparatus 36 is shown downstream of fining vessel 34 relative to a flow direction of molten glass 28, mixing apparatus 36 may be positioned upstream from fining vessel 34 in other embodiments. Downstream glass manufacturing apparatus 30 may include multiple mixing apparatus, for example a mixing apparatus upstream from fining vessel 34 and a mixing apparatus downstream from fining vessel 34. When used, multiple mixing apparatus may be of the same design, or they may be of a different design from one another. One or more of the vessels and / or conduits disclosed herein may include static mixing vanes positioned therein to further promote mixing and subsequent homogenization of the molten material.

[0124] Downstream glass manufacturing apparatus 30 may further include another conditioning chamber such as delivery vessel 40 located downstream from mixing apparatus 36. Delivery vessel 40 can act as an accumulator and / or flow controller to provide a consistent flow of molten glass 28 to forming body 42 by way of exit conduit 44. The molten glass within delivery vessel 40 can, in some embodiments, include a free surface, wherein a free volume extends upward from the free surface to a top of the delivery vessel. As shown, mixing apparatus 36 can be coupled to delivery vessel 40 by way of third connecting conduit 46, wherein molten glass 28 can be gravity fed from mixing apparatus 36 to delivery vessel 40 through third connecting conduit 46.

[0125] Downstream glass manufacturing apparatus 30 may further include forming apparatus 48 configured to form a glass article, for example glass ribbons. Accordingly, forming apparatus 48 may comprise a down-draw apparatus, such as an overflow down-draw apparatus, wherein exit conduit 44 is positioned to deliver molten glass 28 from delivery vessel 40 to inlet conduit 50 of forming body 42. The forming body in a fusion down-draw glass manufacturing apparatus can comprise a trough 52 positioned in an upper surface of the forming body and opposing converging forming surfaces 54 that converge in a draw direction 56 along a bottom edge (root) 58 of the forming body. Molten glass delivered to forming body trough 52 via delivery vessel 40, exit conduit 44, and inlet conduit 50 overflows the walls of trough 52 and descends along the converging forming surfaces 54 as separate flows of molten glass. The separate flows of molten glass join below and along root 58 to produce a ribbon of molten glass that is drawn in draw direction 56 from root 58 by applying a downward tension to the molten glass ribbon, such as by gravity and opposing, counter-rotating pulling rolls 62. The applied downward tension, and the temperature of the molten glass, can be used to controldimensions of the glass ribbon as the molten glass cools and a viscosity of the molten glass increases. Accordingly, the molten glass ribbon goes through a viscosity transition, from a viscous state to a viscoelastic state, to an elastic state and acquires mechanical properties that give glass ribbon 60 stable dimensional characteristics. Glass ribbon 60 may then be scored, then divided into shorter lengths, such as into glass sheets 64 using scoring apparatus 66.

[0126] Components of downstream glass manufacturing apparatus 30, including any one or more of connecting conduits 32, 38, 46, fining vessel 34, mixing apparatus 36, delivery vessel 40, exit conduit 44, or inlet conduit 50 may be formed from a precious metal. Suitable precious metals include platinum group metals selected from the group consisting of platinum, iridium, rhodium, osmium, ruthenium and palladium, or alloys thereof. For example, downstream components of the glass manufacturing apparatus may be formed from a platinumrhodium alloy including from about 70% to about 90% by weight platinum and about 10% to about 30% by weight rhodium.

[0127] To facilitate fusion draw processing, a glass desirably has a sufficiently high liquidus viscosity (i.e., the viscosity of a molten glass at the liquidus temperature). A higher liquidus viscosity can facilitate forming of the glass by a down-draw process, such as fusion forming. Liquidus viscosities of fusion formable glasses may be greater than about 140 kPoise. In addition, the fusion drawing process can operate over a range of viscosities. Glass is typically delivered to the trough of the forming body at a viscosity corresponding to about 20,000-35,000 Poise and leaves the root of the forming body as a viscous ribbon at a viscosity corresponding to about 100,000 Poise or more. The temperature corresponding to a 35,000 Poise viscosity is often used as a guide for the temperature at which glass is to be delivered to the trough of the forming body for fusion drawing. Glasses of the present disclosure can have a temperature corresponding to a 35,000 Poise Temperature (referred to herein as the “35,000 Poise Temperature”) that facilitates forming through down-draw processes, for example a 35,000 Poise Temperature greater than about 1250°C. Typically, a low 35,000 Poise Temperature is desired to minimize undesirable creep of the forming body refractory material over time.

[0128] The temperature corresponding to a 200 Poise viscosity is often used as a guideline for a suitable melting temperature for a glass. In some implementations, glasses of the present disclosure may be characterized by a high 200 Poise Temperature, also referred to as a Poise Melting Point (and referred to herein as the “200 Poise Melting Point”), to facilitate forming. Preferably, the difference between the 200 Poise Temperature and the 35,000 PoiseTemperature is less than or equal to about 450°C, for example equal to or less than about 420°C, such as equal to or less than about 400°C.

[0129] In some glass compositions described herein, SiCh can serve as a basic glass former. Phase separated glasses of the present disclosure may comprise a total amount of S i O2 in a range from about 57 mol% to about 71 mol%, for example in a range from about 57 mol% to about 70 mol%, in a range from about 57 mol% to about 69 mol%, in a range from about 57 mol% to about 68 mol%, in a range from about 57 mol% to about 67 mol%, in a range from about 57 mol% to about 66 mol%, in a range from about 57 mol% to about 65 mol%, in a range from about 57 mol% to about 64 mol%, in a range from about 57 mol% to about 63 mol%, in a range from about 57 mol% to about 62 mol%, in a range from about 57 mol% to about 61 mol%, in a range from about 57 mol%to about 60 mol%, or in a range from about 57 mol% to about 59 mol%, or in a range from about 57 mol% to about 58 mol%, including all ranges and subranges therebetween. In embodiments, the glass composition may include Si O2 in a range from about 58 mol% to about 71 mol%, in a range from about 59 mol% to about 71 mol%, in a range from about 60 mol% to about 71 mol%, in a range from about 61 mol% to about 71 mol%, in a range from about 62 mol% to about 71 mol%, in a range from about 63 mol% to about 71 mol%, in a range from about 64 mol% to about 71 mol%, in a range from about 65 mol% to about 71 mol%, in a range from about 66 mol% to about 71 mol%, in a range from about 67 mol% to about 71 mol%, in a range from about 68 mol% to about 71 mol%, in a range from about 69 mol% to about 71 mol%, or in a range from about 70 mol% to about 71 mol%, including all ranges and subranges therebetween.

[0130] In some embodiments, glasses of the present disclosure may comprise a total amount of SiCh in an amount in a range from about 67.2 mol% to about 69 mol%, in a range from about 67.4 mol% to about 69 mol%, in a range from about 67.6 mol% to about 69 mol%, in a range from about 67.8 mol% to about 69 mol%, in a range from about 68.0 mol% to about 69 mol%, in a range from about 68.2 mol% to about 69 mol%, in a range from about 68.4 mol% to about 69 mol%, in a range from about 68.6 mol% to about 69 mol%, in a range from about 68.8 mol% to about 69 mol%, including all ranges and subranges therebetween. In embodiments, the glass may comprise SiCh in a range from about 67 mol%to about 68.6 mol%, in a range from about 67 mol% to about 68.4 mol%, in a range from about 67 mol% to about 68.2 mol%, in arange from about 67 mol%to about 68.0 mol%, in arange from about 67 mol% to about 67.8 mol%, in a range from about 67 mol% to about 67.6 mol%, in a range from about 67 mol% to about 67.4 mol%, including all ranges and subranges therebetween. As usedherein, the term “total amount” in the context of a phase separated glass refers to the amount of a chemical species in the phase separated glass without regard to the location of the chemical species in any of the individual phases present in the glass. Thus, for example, the total amount of SiC>2 in a phase separated glass comprising two phases refers to the combined amount of SiC>2 that may be present in both phases.

[0131] Phase separated glasses of the present disclosure may comprise a total amount of AI2O3 in a range from about 3 mol% to about 13 mol%, for example in a range from about 3 mol% to about 12 mol%, in a range from about 3 mol% to about 11 mol%, in a range from about 3 mol% to about 10 mol%, in a range from about 3 mol% to about 9 mol%, in a range from about 3 mol% to about 8 mol%, in a range from about 3 mol% to about 7 mol%, in a range from about 3 mol% to about 6 mol%, in a range from about 3 mol% to about 5 mol%, or in a range from about 3 mol% to about 4 mol%, including all ranges and subranges therebetween. In embodiments, the glass may comprise AI2O3 in a range from about 4 mol% to about 13 mol%, in a range from about 5 mol% to about 13 mol%, in a range from about 6 mol% to about 13 mol%, in a range from about 7 mol% to about 13 mol%, in a range from about 8 mol% to about 13 mol%, in a range from about 9 mol% to about 13 mol%, in a range from about 10 mol% to about 13 mol%, in a range from about 11 mol% to about 13 mole%, or in a range from about 12 mol% to about 13 mol%, including all ranges and subranges therebetween. In some embodiments, glasses of the present disclosure may comprise AI2O3 in a range from about 7.6 mol% to about 8.7 mol%, for example in a range from about 7.6 mol% to about 8.6 mol%, in a range from about 7.6 mol% to about 8.5 mol%, in a range from about7.6 mol% to about 8.4 mol%, in a range from about 7.6 mol% to about 8.3 mol%, in a range from about 7.6 mol% to about 8.2 mol%, in a range from about 7.6 mol% to about 8.1 mol%, in a range from about 7.6 mol% to about 8.0 mol%, in a range from about 7.6 mol% to about 7.9 mol%, in a range from about 7.6 mol% to about 7.8 mol%, or in a range from about 7.6 mol% to about 7.7 mol%, including all ranges and subranges therebetween. In embodiments, the glass may comprise AI2O3 in a range from about 7.7 mol% to about 8.7 mol%, in a range from about 7.8 mol% to about 8.7 mol%, in a range from about 7.9 mol% to about 8.7 mol%, in a range from about 8.0 mol% to about 8.7 mol%, in a range from about 8.1 mol% to about8.7 mol%, in a range from about 8.2 mol% to about 8.7 mol%, in a range from about 8.3 mol% to about 8.7 mol%, in a rage from about 8.4 mol% to about 8.7 mol%, in a range from about 8.5 mol% to about 8.7 mol%, or in a range from about 8.6 mol% to about 8.7 mol%, including all ranges and subranges therebetween.

[0132] Phase separated glasses of the present disclosure may comprise a total amount of B2O3 in a range from about 9% to about 20%, for example in a range from about 10 mol% to about 20 mol%, in a range from about 11 mol% to about 20 mole%, in a range from about 12 mol%to about 20 mol%, in a range from about 13 mol%to about 20 mol%, in a range from about 14 mol% to about 20 mol%, in a range from about 15 mol% to about 20 mol%, in a range from about 16 mol% to about 20 mole%, in a range from about 17 mol% to about 20 mol%, in a range from about 18 mol% to about 20 mol%, or in a range from about 19 mol% to about 20 mol%, including all ranges and subranges therebetween. In embodiments, the glass may comprise B2O3 in a range from about 9% to about 18%, for example in a range from about 9 mol% to about 18 mol%, in a range from about 9 mol% to about 17 mole%, in a range from about 9 mol% to about 16 mol%, in a range from about 9 mol% to about 15 mol%, in a range from about 9 mol% to about 14 mol%, in a range from about 9 mol% to about 13 mol%, in a range from about 9 mol% to about 12 mole%, in a range from about 9 mol% to about 11 mol%, or in a range from about 9 mol% to about 10 mol%, including all ranges and subranges therebetween. In some embodiments, glasses of the present disclosure may comprise B2O3 in a range from about 11.9 mol% to about 14.1 mol%, for example in a range from about 11.9 mol% to about 13.8 mol%, in a range from about 11.9 mol% to about 13.6 mol%, in a range from about 11.9 mol% to about 13.4 mol%, in a range from about 11.9 mol% to about 13.2 mol%, in a range from about 11.9 mol%to about 13.0 mol%, in a range from about 11.9 mol% to about 12.8 mol%, in a range from about 11.9 mol% to about 12.6 mol%, in a range from about 11.9 mol% to about 12.4 mol%, or in a range from about 11.9 mol% to about 12.2 mol%, including all ranges and subranges therebetween. In embodiments, the glass may comprise AI2O3 in a range from about 12.0 mol% to about 14. 1 mol%, in a range from about 12.2 mol% to about 14.1 mol%, in a range from about 12.3 mol% to about 14.1 mol%, in a range from about 12.4 mol% to about 14.1 mol%, in a range from about 12.5 mol% to about 14.1 mol%, in a range from about 12.6 mol% to about 14.1 mol%, in a range from about 12.8 mol% to about 14. 1 mol%, in a range from about 13.0 mol% to about 14. 1 mol%, in a range from about 13.2 mol% to about 14.1 mol%, in a range from about 13.4 mol% to about 14.1 mol%, in a range from about 13.6 mol% to about 14. 1 mol%, or in a range from about 13.8 mol% to about 14.1 mol%, including all ranges and subranges therebetween.

[0133] Increasing amounts of Si O2 can decrease the dielectric constant and loss tangent of the glass at frequencies of 10 GHz or greater; however, increasing amounts of SiCh may decrease formability of the glass, and in particular formability by down-draw processes. Forexample, as the amount of SiCh increases, the liquidus temperature of the glass may increase. Pure SiC>2 has a low CTE, and, due to its high melting temperature, is incompatible with downdraw processes. B2O3 can be added to lower the viscosity of the glass and reduce the liquidus temperature to facilitate forming of the glass, particularly by down-draw processes. B2O3 can have the effect of decreasing the liquidus temperature more rapidly than the viscosity, and thus may improve the liquidus viscosity for forming by down-draw processes. AI2O3 can reduce the liquidus temperature and thus increase the liquidus viscosity. Thus, the amounts of SiC>2, B2O3, and optionally AI2O3, can be selected according to the present disclosure to balance the desired dielectric properties and formability of the glass.

[0134] In some aspects of the present disclosure, the total amounts of SiCh, B2O3, and AI2O3 in the glass may be selected such that a ratio of B2O3:(AhO3 + SiCE) is from about 0. 1 to about 0.3, for example in a range from about 0.12 to about 0.3, in a range from about 0.14 to about 0.3, in a range from about 0. 16 to about 0.3, in a ranger from about 0.18 to about 0.3, in a range from about 0.2 to about 0.3, in a range from about 0.22 to about 0.3, in a range from about 0.24 to about 0.3, in a range from about 0.26 to about 0.3, or in a range from about 0.28 to about 0.3, including all arranges and subranges therebetween. In some aspects, the ratio of B2O3:(AhO3 + SiCh) may be from about 0.16 to about 0. 18, about 0.16 to about 0. 17, or in a range from about 0.17 to about 0.18, including all ranges and subranges therebetween.

[0135] In some aspects, the total amounts of Si O2 and B2O3 may be selected such that a sum of SiC>2 plus B2O3 is in a range from about 77 mol% to about 84 mol%, for example in a range from about 78 mol% to about 84 mol%, in a range from about 79 mol% to about 84 mol%, in a range from about 80 mol% to about 84 mol%, in a range from about 81 mol% to about 84 mol%, in a range from about 82 to about 84 mol%, or in a range from about 83 mol% to about 84 mol%. In aspects, the glass may comprise such that a sum of SiCE plus B2O3 is in a range from about 77 mol% to about 83 mol%, in a range from about 77 mol% to about 82 mol%, in a range from about 77 mol% to about 81 mol%, in a range from about 77 mol% to about 80 mol%, in a range from about 77 mol% to about 79 mol%, or in a range from about 77 mol% to about 78 mol%, including all ranges and subranges therebetween.

[0136] In some aspects, the total amounts of SiCh, B2O3, and AI2O3 in the phase separated glass may be selected such that a sum of SiCh plus B2O3 plus AI2O3 is in a range from about 85 mol% to about 93 mol%, for example in a range from about 86 mol% to about 93 mol%, in a range from about 87 mol% to about 93 mol%, in a range from about 88 mol% to about 93 mol%, in a range from about 89 mol% to about 93 mol%, in a range from about 90mol% to about 93 mol%, in a range from about 91 mol% to about 93 mol%, or in a range from about 92 mol% to about 93 mol%, including all ranges and subranges therebetween. In aspects, the glass may comprise a sum of SiCh, B2O3, and AI2O3 in a range from about 85 mol% to about 92 mol%, in a range from about 85 mol%to about 91 mol%, in a range from about 85 mol% to about 90 mol%, in a range from about 85 mol% to about 89 mol%, in a range from about 85 mol% to about 88 mol%, in a range from about 85 mol% to about 87 mol%, or in a range from about 85 mol% to about 86 mol%, including all ranges and subranges therebetween.

[0137] According to some aspects, when present, the phase separated glass can include one or more alkaline earth oxides (RO), where RO comprises MgO, CaO, BaO, and / or SrO.

[0138] MgO may benefit glass melting by reducing melting temperatures and may benefit glass forming by reducing liquidus temperatures and increasing liquidus viscosity, while also preserving high annealing points. Phase separated glasses of the present disclosure may comprise a total amount of MgO in a range from about 4% to about 6%, for example in a range from about 4 mol%to about 5.8 mol%, in a range from about 4 mol%to about 5.6 mole%, in a range from about 4 mol% to about 5.4 mol%, in a range from about 4 mol% to about 5.2 mol%, in a range from about 4 mol% to about 5 mol%, in a range from about 4 mol% to about 4.8 mol%, in a range from about 4 mol% to about 4.6 mole%, in a range from about 4 mol% to about 4.4 mol%, or in a range from about 4 mol% to about 4.2 mol%, including all ranges and subranges therebetween. In aspects, the glass may comprise MgO in a range from about 4.2 mol% to about 6 mol%, in a range from about 4.4 mol% to about 6%, in a range from about 4.6 mol% to about 6 mol%, in a range from about 4.8 mol% to about 6 mole%, in a range from about 5 mol% to about 6 mol%, in a range from about 5.2 mol% to about 6 mol%, in a range from about 5.4 mol% to about 6 mol%, in a range from about 5.6 mol% to about 6 mol%, or in a range from about 5.8 mol% to about 6 mole%, including all ranges and subranges therebetween.

[0139] Phase separated glasses of the present disclosure may comprise a total amount of CaO in a range from about 3 mol% to about 6 mol%, for example in a range from about 3.2 mol% to about 6 mol%, in a range from about 3.4 mol% to about 6 mole%, in a range from about 3.6 mol% to about 6 mol%, in a range from about 3.8 mol% to about 6 mol%, in a range from about 4 mol% to about 6 mol%, in a range from about 4.2 mol% to about 6 mol%, in a range from about 4.4 mol% to about 6 mole%, in a range from about 4.6 mol% to about 6 mol%, in a range from about 4.8 mol% to about 6 mol%, in a range from about 5 mol% to about 6 mol%, in a range from about 5.2 mol% to about 6%, in a range from about 5.4 mol%to about 6 mol%, in a range from about 5.6 mol%to about 6 mole%, or in a range from about5.8 mol% to about 6 mol%, including all ranges and subranges therebetween. In embodiments, the glass may comprise CaO in a range from about 3 mol% to about 5.8 mol%, in a range from about 3 mol% to about 5.6 mol%, in a range from about 3 mol% to about 5.4 mol%, in a range from about 3 mol% to about 5.2 mol%, in a range from about 3 mol% to about 5 mol%, in a range from about 3 mol% to about 4.8 mol%, in a range from about 3 mol% to about 4.6 mol%, in a range from about 3 mol% to about 4.4 mol%, in a range from about 3 mol% to about 4.2 mol%, in a range from about 3 mol% to about 4 mol%, in a range from about 3 mol% to about3.8 mol%, in a range from about 3 mol% to about 3.6 mol%, in a range from about 3 mol% to about 3.4 mol%, or in a range from about 3 mol% to about 3.2 mole%, including all ranges and subranges therebetween.

[0140] Phase separated glasses of the present disclosure may comprise a total amount of SrO less than about 0.2 mol%, for example in a range from about 0% to about 0.2 mol%, for example in a range from about 0.02 mol% to about 0.2 mol%, in a range from about 0.04 mol% to about 0.2 mol%, in a range from about 0.06 mol% to about 0.2 mol%, in a range from about 0.08 mol% to about 0.2 mol%, in a range from about 0. 1 mol% to about 0.2 mol%, in a range from about 0.12 mol% to about 0.2 mol%, in a range from about 0.14 mol% to about 0.2 mol%, in a range from about 0.16 mol% to about 0.2 mol%, or in a range from about 0.18 mol% to about 0.2 mol%, including all ranges and subranges therebetween. In embodiments, the glass may comprise SrO in a range from about 0 mol% to about 0.18 mol%, in a range from about 0 mol% to about 0.16 mol%, in a range from about 0 mol% to about 0.14 mol%, in a range from about 0 mol% to about 0. 12 mol%, in a range from about 0 mol% to about 0. 1 mol%, in a range from about 0 mol% to about 0.08 mol%, in a range from about 0 mol% to about 0.06 mol%, in a range from about 0 mol% to about 0.4 mol%, or in a range from about 0 mol% to about 0.02 mol%, including all ranges and subranges therebetween.

[0141] Phase separated glasses of the present disclosure may optionally comprise a total amount of BaO less than about 1 mol%, for example in a range from about 0% to about 1 mol%, such as in a range from about 0.1 mol% to about 1 mol%, in a range from about 0.2 mol% to about 1 mol%, in a range from about 0.3 mol% to about 1 mol%, in a range from about 0.4 mol% to about 1 mol%, in a range from about 0.5 mol% to about 1 mol%, in a range from about 0.6 mol% to about 1 mol%, in a range from about 0.7 mol% to about 1 mol%, in a range from about 0.8 mol% to about 1 mol%, or in a range from about 0.9 mol% to about 1 mol%, including all ranges and subranges therebetween. In aspects, the glass may compriseBaO in a range from about 0 mol% to about 0.9 mol%, in a range from about 0 mol% to about 0.8 mol%, in a range from about 0 mol% to about 0.7 mol%, in a range from about 0 mol% to about 0.6 mol%, in a range from about 0 mol% to about 0.5 mol%, in a range from about 0 mol% to about 0.4 mol%, in a range from about 0 mol% to about 0.3 mol%, in a range from about 0 mol% to about 0.2 mol%, or in a range from about 0 mol% to about 0.1 mol%, including all ranges and subranges therebetween.

[0142] In some aspects, the one or more alkaline earth oxides MgO, CaO, BaO, SrO may be present in a combined amount of from about 4.6 mol% to about 14.2 mol%, for example in a range from about 4.8 mol% to about 14.2 mol%, in a range from about 5 mol% to about 14.2 mol%, in a range from about 5.4 mol% to about 14.2 mol%, in a range from about 5.8 mol% to about 14.2 mol%, in a range from about 6.2 mol% to about 14.2 mol%, in a range from about 7.2 mol%to about 14.2 mol%, in a range from about 8.2 mol%to about 14.2 mol%, in a range from about 9.2 mol% to about 14.2 mol%, in a range from about 10.2 mol% to about 14.2 mol%, in a range from about 11.2 mol% to about 14.2 mol%, in a range from about 12.2 mol% to about 14.2 mol%, or in a range from about 13.2 mol% to about 14.2 mol%, including all ranges and subranges therebetween. In aspects, the one or more alkaline earth oxides may be present in a combined amount in a range from about 4.6 mol% to about 13.6 mol%, in a range from about 4.6 mol% to about 12.6 mol%, in a range from about 4.6 mol% to about 11.6 mol%, in a range from about 4.6 mol% to about 10.6 mol%, in a range from about 4.6 mol% to about 9.6 mol%, in a range from about 4.6 mol% to about 8.6 mol%, in a range from about 4.6 mol% to about 7.6 mol%, in a range from about 4.6 mol% to about 6.6 mol%, or in a range from about 4.6 mol% to about 5.6 mol%, including all ranges and subranges therebetween.

[0143] According to some aspects of the present disclosure, the phase separated glass can include MgO and at least one additional alkaline earth oxide (RO) selected from CaO, BaO, and SrO. In some examples, the combination of MgO and at least one additional RO can result in a glass having a lower dielectric constant and / or loss tangent compared to a glass that includes MgO or another RO alone.

[0144] In some aspects, the total amount of MgO and the total amount of additional RO are selected as described above and in concert with the total amount of AI2O3 present in the glass such that a ratio of RO i otai to AI2O3 (ROiotai: AI2O3) is greater than 1. Providing a glass with a ratio RO otai: AI2O3 > 1, can facilitate forming a manufacturable glass that can be drawn using conventional glass forming processes, such as a fusion process.

[0145] In some aspects, a ratio of the total amount of MgO to ROTotai (MgO. ROTotai) may be in a range from about 0.3 to about 4.7, for example in a range from about 0.3 to about 4.5, in a range from about 0.3 to about 0.4, in a range from about 0.3 to about 3.5, in a range from about 0.3 to about 3, in a range from about 0.3 to about 2.5, or in a range from about 0.3 to about 2, including all ranges and subranges therebetween. In embodiments, the total ratio of MgO to RO otai may be in a range from about 0.5 to about 4.7, in a range from about 0.75 to about 4.7, in a range from about 1 to about 4.7, in a range from about 1.5 to about 4.7, in a range from about 2 to about 4.7, in a range from about 2.5 to about 4.7, in a range from about 3 to about 4.7, in a range from about 3.5 to about 4.7, or in a range from about 4 to about 4.7, including all ranges and subranges therebetween.

[0146] For a given phase separated glass, a lower dielectric constant and / or loss tangent may be achieved in the glass by decreasing the concentration of the single RO species present in the glass. Further, it is believed that for a given ROiotai concentration, a reduced dielectric constant and / or loss tangent may be achieved in the glass by combining MgO with at least one additional RO species, such as CaO, SrO, and / or BaO, compared to a glass derived from a precursor composition having a similar ROTotai concentration but which includes a single RO species. For example, for a given ROTotai concentration, a glass including a combination of MgO plus CaO, SrO, and / or BaO according to the present disclosure may have a lower dielectric constant than a glass that includes a single RO species selected from MgO, CaO, SrO, or BaO. In another example, for a given ROTotai concentration, a glass including a combination of MgO plus CaO, SrO, and / or BaO according to the present disclosure may have a lower loss tangent than a glass including a single RO species selected from CaO, SrO, or BaO.

[0147] Without wishing to be bound by theory, it is believed that for a glass derived from a precursor composition having a single RO species, as the concentration of the single RO species decreases, the dielectric constant and the loss tangent of the derived glass, as measured with signals of 10 GHz, also decreases.

[0148] In some aspects, the amount of alkaline earth oxides in the phase separated glass can be selected in combination with other materials, such as B2O3 and optionally AI2O3, to provide phase separated glasses having desired characteristics. For example, increasing the amount of alkaline earth oxides relative to SiO2 and AI2O3 can have the effect of decreasing the viscosity of a glass melt and may increase melting and forming temperatures. Alkaline earth oxides may also increase the CTE and density of the glass, and may affect other propertiesas well, such as the elastic modulus. Alkaline earth oxides can also decrease the liquidus temperature. Thus, in some aspects, the total amounts of the alkaline earth oxides, B2O3, and AI2O3 can be selected to balance the desired physical properties and formability of the phase separated glass.

[0149] Phase separated glasses of the present disclosure may optionally comprise a total amount of ZnO less than about 2 mol%, for example in a range from about 0 mol% to about 1.5 mol%, in a range from about 0 mol% to about 1 mol%, or in a range from about 0 mol% to about 0.5 mol%, including all ranges and subranges therebetween. In aspects, the glass may comprise ZnO in range from about 0.5 mol% to about 2 mol%, in a range from about 1 mol% to about 2 mol%, or in a range from about 1.5 mol% to about 2 mol%, including all ranges and subranges therebetween.

[0150] In some aspects, the total amounts of alkaline earth oxides may be selected such that a ratio of ROiotafCAhOs + B2O3) in the glass is in a range from about 0.2 to about 0.6, in a range from about 0.2 to about 0.5, or in a range from about 0.2 to about 0.4, including all ranges and subranges therebetween. In aspects, the total amount of alkaline earth oxides may be selected such that the ratio of ROrotai:(A12O3 + B2O3) is in a range from about 0.3 to about 0.6, in a range from about 0.4 to about 0.6, or in a range from about 0.5 to about 0.6, including all ranges and subranges therebetween. In some aspects, the ratio of ROrotai:( AI2O3 + B2O3) may be about 0.2, about 0.24, about 0.25, about 0.28, about 0.29, about 0.3, about 0.32, about 0.35, about 0.36, about 0.4, about 0.5, about 0.55, about 0.58, about 0.6, including all ranges and subranges therebetween.

[0151] Phase separated glasses of the present disclosure may optionally include one or more fining agents, such as, by way of non-limiting example, SnCh. Sb2C>3, AS2O3, and / or one or more halogen salts, including fluorine, chlorine, or bromine salts. When one or more fining agents are present in the glass, the fining agents may be present in a total amount less than about 1 mol%. In some aspects, the fining agents may be present in an total amount of about 0.01 mol% to about 1 mol%, for example in an amount in a range from about 0.01 mol% to about 0.9 mol%, in a range from about 0.01 mol% to about 0.8 mol%, in a range from about 0.01 mol% to about 0.7 mol%, in a range from about 0.01 mol%to about 0.6 mol%, in a range from about 0.01 mol% to about 0.5 mol%, in a range from about 0.01 mol% to about 0.4 mol%, in a range from about 0.01 mol% to about 0.3 mol%, in a range from about 0.01 mol% to about 0.2 mol%, in a range from about 0.01 mol% to about 0.1 mol%, including all ranges and subranges therebetween. In various embodiments, the glass may comprise a total concentrationof fining agents in an amount in a range from about 0.01 mol% to about 0.09 mol%, in a range from about 0.01 mol% to about 0.08 mol%, in a range from about 0.01 mol% to about 0.07 mol%, in a range from about 0.01 mol% to about 0.06 mol%, in a range from ab out 0.01 mol% to about 0.05 mol%, in a range from about 0.01 mol% to about 0.04 mol%, in a range from about 0.01 mol%to about 0.03 mol%, or in a range from about 0.01 mol%to about 0.02 mol%, , including all ranges and subranges therebetween. In embodiments, the total concentration of fining agent(s) may be in a range from about 0.02 mol% to about 0.1 mol%, in a range from about 0.03 mol% to about 0. 1 mol%, in a range from about 0.04 mol% to about 0.1 mol%, in a range from about 0.05 mol% to about 0.1 mol%, in a range from about 0.06 mol% to about 0. 1 mol%, in a range from about 0.07 mol% to about 0. 1 mol%, in a range from about 0.08 mol% to about 0.1 mol%, or in a range from about 0.09 mol% to about 0.1 mol%, including all ranges and subranges therebetween. However, in other embodiments, the fining agents may be present in an amount in a range from about 0.01 mol% to about 0.5 mol%, including all ranges and subranges therebetween.

[0152] When the content of the fining agents in the phase separated glass is too large, the fining agents may enter the glass structure and affect various glass properties. However, when the content of the fining agents is too low, the phase separated glass may be difficult to form. According to one aspect of the disclosure, SnCh may be included as a fining agent in a total amount in a range from about 0 mol% to about 0.3 mol%. For example, SnCh may be present in a total amount in a range from about 0 mol% to about 0.3 mol%, in a range from about 0 mol% to about 0.2 mol%, or in a range from about 0 mol% to about 0.1 mol%, including all ranges and subranges therebetween. In further embodiments, the glass may comprise SnCh in a range from about 0.05 mol% to about 0.3 mol%, in a range from about 0.05 mol% to about 0.2 mol%, or in a range from about 0.05 mol% to about 0.1 mol%, including all ranges and subranges therebetween.

[0153] The phase separated glass may optionally include contaminants or unintended additives, such as TiCh or ZrCh. These additional materials, when present, are typically present in very low or trace total amounts of less than about 0.5 mol%, for example in a range from 0 to about 0.4 mol%, in a range from 0 to about 0.3 mol%, or in a range from 0 to about 0.2 mol%, or in a range from 0 to about 0.1 mol%, including all ranges and subranges therebetween.

[0154] In some aspects, phase separated glasses of the present disclosure may be substantially free of alkali metal. As used herein, the phrase “substantially free” is defined tomean no more than trace amounts of the material, in this case, alkali metal oxides, are present, for example a total amount no more than about 0.5 mole%, no more than 0.4 mol%, no more than 0.3 mol%, no more than about 0.2 mol%, or no more than about 0. 1 mol%. Trace amounts of alkali metal oxides may be present due to contamination or limitations in manufacturing. As discussed above, in some implementations, glasses of the present disclosure can be prepared without the addition of alkali metals such that the glasses are substantially free of alkali metals to decrease the likelihood of ion migration during thermal treatment of articles formed from the glass. Decreasing or minimizing the likelihood of ion migration may be advantageous in some applications, such when the glasses are used as a substrate in an electronic device where ion migration may be undesirable.

[0155] In some aspects, phase separated glasses of the present disclosure can include at least one alkali metal oxide (R2O), where R2O is Li2O, Na2O, and / or K2O. In some aspects, the one or more alkali metal oxides may be present individually or in a combined amount of from 0 mol% to about 1 mol%. In some aspects, the one or more alkali metal oxides may be present individually or in a combined amount in a range from about 0 mol% to about 0.9 mol%, in a range from about 0 mol% to about 0.8 mol%, in a range from about 0 mol% to about 0.7 mol%, in a range from about 0 mol% to about 0.6 mol%, in a range from about 0 mol% to about 0.5 mol%, in a range from 0 mol% to about 0.4 mol%, in a range from 0 mol% to about 0.3 mol%, in a range from 0 mol% to about 0.2 mol%, or in a range from about 0 to about 0. 1 mol%, including all ranges and subranges therebetween. For example, Na2O may be present in a total amount in a range from about 0 mol% to about 0.05 mol%, in a range from about 0 mol% to about 0.04 mol%, in a range from about 0 mol% to about 0.03 mol%, in a range from about 0 mol% to about 0.02 mol%, or in a range from about 0 mol% to about 0.01 mol%, including all ranges and subranges therebetween. In aspects, the glass may comprise NaO? in a range from about 0.005 mol% to about 0.5 mol%, in a range from about 0.01 mol% to about 0.05 mol%, in a range from about 0.02 mol% to about 0.05 mol%, in a range from about 0.03 mol% to about 0.05mol%, or in a range from about 0.04 mol% to about 0.05 mol%, including all ranges and subranges therebetween. In another example, K2O can be present in a total amount of from about 0 mol% to about 2 mol%, in a range from about 0 mol% to about 1 mol%, in a range from about 0 mol% to about 0.5 mol%, including all ranges and subranges therebetween. In aspects, the glass may comprise K2O in a range from about 0. 1 mol% to about 2 mol%, in a range from about 0.2 mol% to about 2 mol%, in a range from about 0.5 mol% toabout 2 mol%, in a range from about 1 mol% to about 2 mol%, or in a range from about 1.5 mol% to about 2 mol%, including all ranges and subranges therebetween.

[0156] In some aspects, phase separated glasses of the present disclosure can be characterized by a dielectric constant Dk of about 10 or less, as measured with signals at 10 GHz. In some implementations, the phase separated glass may have a dielectric constant Dk of about 9 or less, about 8 or less, about 7 or less, about 6 or less, or about 5 or less, as measured with signals at 10 GHz. In some implementations, the phase separated glass may have a dielectric constant Dk of about 4.5 to about 6, as measured with signals at 10 GHz.

[0157] In some aspects, phase separated glasses of the present disclosure can be characterized by a loss tangent Dr of about 0.004 or less, as measured with signals at 10 GHz, for example about 0.003 or less, including all ranges and subranges therebetween. In some aspects, phase separated glasses of the present disclosure can be characterized by a loss tangent of about 0.0029 to about 0.004, as measured with signals at 10 GHz. Unless otherwise specified, dielectric properties Dk and Df were measured on polished, as-made glass samples that were 3” x 3” and less than 1 mm thick. Test frequencies ranged from 2.7 GHz to 50 GHz. The samples were tested with a split post dielectric resonator at signal frequencies equal to or less than 10 GHz or an open cavity resonator at signal frequencies greater than 10 GHz. In each case, the dielectric constant and loss tangent were measured from the shift and the broadening of the resonance peaks.

[0158] Phase separated glasses of the present disclosure may be suitable for use in PCB applications. A PCB laminate may include an insulating layer laminated to electrically conductive films with the insulating layer disposed between the electrically conductive films. The insulating layer preferably has a low dielectric loss, for example less than 0.005 at 10 GHz, and sufficient mechanical strength and fracture toughness to allow for handing and post processing in a production environment. The insulating layer should also be able withstand hole drilling without damage or fracture and, depending on the application, can be in the range of about 100 to 700 micrometers thick. In addition, the insulating layer may withstand temperatures of up to 260°C for 30 seconds, while maintaining dimensional stability. This temperature is usually based on the temperature required for solder reflow in post processing of the PCB boards. Solder paste is generally used to attach the electrical components to their contact pads. The assembly may then be exposed to high temperatures (usually 260°C for 30 seconds) to cause the solder to reflow and create a permanent solder joint. Thus, the insulating layer of the PCB should be a low dielectric loss material that can also withstand solderingreflow temperatures typically used in PCB processing with little to no softening or dimensional change.

[0159] It has been observed that during a drawing process, wherein a phase separable glass is placed under tension, for example in a downdraw process, and drawn, for example, into a glass sheet, optical retardation may be produced in the phase separated glass sheet as evidenced by stress across the glass sheet as shown by strain scope measurements using polarized light. Annealing has been shown to increase optical retardation. The longer the anneal time, the greater the optical retardation may be.

[0160] FIGS. 6, 7, and 8 illustrate (1) strain scope images of an approximately 3- centimeter (cm) x 3 cm sample of a phase separated glass sheet (6(a), 7(a), and 8(a)) and (2) photographs (FIGS. 6(b), 7(b), and 8(b)) from a scanning electron microscope (SEM) showing the phases of the glass samples. The sample of FIG. 6 is an as-drawn sample of the glass, without subsequent annealing. The sample of FIG. 7 is the sample after annealing for 2 hours at 720°C. FIG. 8 depicts the sample of FIG. 7 after annealing for a second time, for an additional 2 hours at 720°C (i.e., four hours total). The increased shading, via strain scope measurement, particularly of the sample of FIG. 7(a), is indicative of increased optical retardation. Moreover, an increase in size of the secondary phase as the samples were annealed is clear when comparing the SEM images of FIGS. 6-8.

[0161] FIGS. 9-12 illustrate SEM photographs of samples of the phase separated glass composition of FIG. 5 after annealing at increasingly greater temperature. For example, the sample of FIG. 9 was annealed at a temperature of about 745°C for a period of about 12 hours. The features indicating phase separation were quite fine and visually difficult to discern. The sample of FIG. 10 was annealed at a temperature of about 800°C for approximately 12 hours. Here, the two phases of the glass become visually distinct, although still small. The sample of FIG. 11 was annealed at a temperature of approximately 850°C for a period of about 12 hours. Distinct phases are clearly visible. The sample of FIG. 12 was annealed at a temperature of about 900°C for a period of about 12 hours. As is evident, the separate phases of the glass of FIG. 12 are easily distinguished. Similar to the results of FIGS. 6,7,8, the greater the anneal temperature, the greater the extent of phase separation, as evidenced by the growth of the secondary phase. Whereas the secondary phase in FIG. 9 is barely discernable, the secondary phase is clearly visible in the image of FIG. 12.

[0162] Images similar to those of FIGS. 9-12 were analyzed using two-dimensional Fourier transform techniques. The samples were etched with a series of different etch times toaccentuate the spatial distribution of the two phases. Close examination of the images revealed the edges of the more-slowly-etched material phase were brighter than the faster-etching phase, giving a signal from the SEM image that was associated with the spatial orientation of the phases. The two-dimensional Fourier transform can be described mathematically using the following equation. vy)] dxdywhere x and y are the coordinates of the physical structure, f(x,y) is the signal from the physical structure to be analyzed (in this instance, the intensity of the backscatter SEM image), u and v are the coordinates in the Fourier domain, and F(u,v) is the Fourier transform of the function f(x,y).

[0163] To understand how the Fourier transform helps identify the spatial orientation of the phases, a few illustrative examples are inspected. First, consider the case in which the phases are oriented into alternating vertical lines. The two-dimensional Fourier transform would consist of a series of peaks in the horizontal direction of the Fourier plane. The spacing between the peaks would provide information about the width of the vertical regions of the phases. The width of the peaks would provide information about the variation in the width of the vertical regions. A similar response is expected if the phases are oriented in alternating horizontal lines, except the peaks in the Fourier transform would be in the vertical direction, rather than the horizontal direction. In both cases, the amplitude of the peaks in the Fourier domain would provide information about how many of the domains have a particular orientation.

[0164] If the material phases are randomly oriented vertically, horizontally, and at every azimuthal angle in the physical plane, but with nearly constant width, the Fourier transform would consist of an annulus, where the peak position in the Fourier domain would be inversely proportional to the phase domain widths. The width of the peak would provide information about the distribution of the phase domain widths.

[0165] The SEM images can be described using a coordinate system illustrated in FIG. 13. The draw direction (represented by arrow 56 in the figure) extends along the y axis (in the -y direction), the thickness of the glass sheet is in the z direction, and the x direction is orthogonal to each of the draw and thickness directions. A sample is referred to as a x cross-sectional image if the surface normal of the surface from which the sample was taken is parallel to the x direction.

[0166] The two-dimensional Fourier transform (2DFT) corresponding to a sample measured from an x surface is shown in FIG. 14. The pale halo around the central dot is the annular ring corresponding to the characteristic width of the phase separation features (i.e., the secondary phase). Its uniformity in radius and width indicates the structure is nearly isotropic for this 2D cross section. However, it is somewhat easier to see nonuniformity if the figure is plotted in rd space, rather than an uv space, where r = yu + v2and 9 = tan-1[y / x],

[0167] The data for samples from the three surfaces plotted in this rd coordinate system are shown in FIG. 15 in greyscale. The vertical axis is the azimuthal direction, 9. The horizontal dimension is the radial direction in the xy Fourier plane, r. The results show the structure of the two phases is isotropic in the azimuthal direction (vertical axes), but the spatial frequency of 31 pm'1, indicates the width of the phases is nearly uniform, with a width of approximately 32 nm. While the 2DFT cross-section from the x sample shows very little anisotropy, the samples in the y and z surfaces (whose surface normals are along the draw direction and along the thickness direction, respectively) show a larger azimuthal variation, as well as a wider variation in the width of the peaks, indicating the material phase regions are being compressed (higher spatial frequency indicates smaller domain widths). These results indicate the anisotropy of the spatial distribution of the material phases of the phase-separated material can vary, depending on the orientation of the material with respect to the draw and thickness directions more strongly than the directions perpendicular to those directions - that is, within the glass sheet, but perpendicular to the draw direction shows less anisotropy.

[0168] Unlike other glasses that may be treated post-forming to induce phase separation, such as by heat treating the glass, it is believed phase separated glasses of the present disclosure phase separate by spontaneous spinodal decomposition while the molten glass flows through downstream glass manufacturing apparatus 30, for example as the molten glass traverses the various connecting conduits and vessels downstream of the melting vessel and before the forming body. This belief is supported by the effect the drawing of the molten glass from the forming body has on the orientation of the phases. To wit, the phase separation must have already occurred for the draw tension to affect the phase orientation.

[0169] FIG. 16 is a schematic diagram of sample locations for collection of stress measurements, and FIG. 17 illustrates stress in a glass ribbon drawn in a fusion downdraw process as the glass composition was changed from a commercially available non-phase separated glass (i.e., Coming® Eagle™ XG®) to a phase separated glass composition as a function of time. The transition occurred over a period of approximately one month. Thetransition was accomplished by slowly varying the glass composition while striving to maintain a stable glass density. Stress data was collected at the edges of the glass sheet (e.g., comers and sides - see FIG. 16). The data show a gradual change in stress (pounds per square inch, psi) from virtually no difference in stress at the beginning of the transition (e.g., about day 3) (which would be expected from the commercial glass) to a stress exceeding + / -250 psi at the completion of the transition, and as much as + / - 300 psi by day 45.

[0170] FIG. 18 is a graph showing loss tangent Df plotted with the logic of stress (in psi) as a function of time during the transition from the Coming® Eagle™ XG® glass to the phase separated glass at various locations on the glass sheet (refer to FIG. 17). The data show both an increase in stress responsible for inherent birefringence and a decrease in loss tangent (e.g., from about 0.0065 to about 0.0045).

[0171] FIG. 19 is a plot of the ratio (B2O3 + MgO) / CaO (when the individual constituents are expressed in mole %) coplotted with stress (in psi), at several locations on the sheet (refer to FIG. 17) during the transition, showing the dielectric property was changing with compositional change.

[0172] The primary glass phase of phase separated glasses disclosed herein is rich in SiC>2, whereas the secondary phase is rich in boron (e.g., B2O3). As described above, the greater the amount of Si O2 in phase separated glass, the more favorable the dielectric properties as components for electronic circuits (e.g., dielectric constant, Dk, and loss tangent, Dr). That is, the dielectric constant and / or loss tangent may be decreased by increasing the amount of SiCh. However, increasing the amount of SiCh in the glass makes the glass less formable by conventional sheet-forming means, e.g., fusion downdraw processes. On the other hand, because the principal form of such electronic (e.g., dielectric) components in PCBs is as thin sheets, high volume production methods may offer beneficially reduced costs. Accordingly, methods of modifying the composition of phase separated intermediate sheets of glass are described, wherein the amount of SiO2 in the glass sheet may be greatly increased after forming the glass sheet. Thus, high-volume production methods may be utilized to form an intermediate glass sheet, whereupon the intermediate glass sheet is further processed to produce an SiCh- rich glass article with desired dielectric properties.

[0173] In accordance with the present disclosure, a phase separated glass article can be etched with a suitable etchant to remove substantially all the boron-rich secondary phase while leaving a silica-rich porous glass article including the silica-rich primary phase. In someembodiments, the porous glass article may subsequently be heated to consolidate the porous glass article into a silica-rich solid glass article, e.g., glass sheet.

[0174] Accordingly, a method is described comprising a first step of forming a glass sheet comprising a phase separated glass including at least a first phase and a second phase, such as a phase separated glass as described herein. The phase separated glass sheet may comprise a width greater than about 340 mm and a length greater than about 440 mm, a width greater than about 680 mm and a length greater than about 880 mm, or a width greater than about 1500 mm and a length greater than about 1500 mm, although smaller or larger dimensions are contemplated and possible using, for example a fusion downdraw process such as the fusion downdraw process described herein.

[0175] The phase separated glass sheet may have a first phase enriched in S i O2 and a second phase enriched in B2O3. The phase separated glass sheet may be optionally washed prior to subsequent steps. For example, the phase separated glass may be washed in a detergent. An ultrasonic bath may be used for the washing. For example, the phase separated glass may be washed by soaking the phase separated glass in an ultrasonic bath comprising a detergent, for example an aqueous solution comprising 4 wt% Semiclean, for a time in a range from about 2 minutes to about 6 minutes, such as for about 4 minutes.

[0176] In a second step, the phase separated glass sheet may be exposed to an etchant, for example an acid suitable for etching the second phase from the glass sheet. The acid may be an aqueous solution comprising an inorganic acid or an organic acid. The acid may be present in the solution in an amount from about 5 wt% to about 40 wt%, depending on the acid selected and the amount of secondary phase that should be removed. Suitable inorganic acids may include at least one of HC1, H2SO4, HNO3, HF, or H3PO4. Example organic acids may include citric acid and / or acetic acid. The etchant may be at a temperature in a range from about 60°C to about 100°C, with the exposure time in a range from about 1 hour to about 6 hours, for example in a range from about 2 hours to about 4 hours. The strength of the acid solution and the temperature of the etchant will dictate the length of time suitable to etch away the boron-rich second phase from the phase separated glass sheet. Removal of the second phase from the phase separated glass sheet produces a porous glass sheet containing predominantly, or entirely, the first phase, e.g., the SiCh-rich phase. Calculated open porosity of the porous glass sheet can be greater than about 28%. About 8.7% of the pores during testing had a diameter greater than about 3 nm, meaning most of the pores were less than about 3 nm in diameter. A median (d50) pore diameter of pores of the porous glass sheet may be less thanabout 1 pm, for example less than about 0.5 pm, less than about 0.1 pm, less than about 0.05 pm, less than about 0.025 pm, or less than about 0.02 pm. Direct porosity measurements were made using mercury intrusion into the pores. However, this technique is limited to pore sizes in excess of 3 nm. Accordingly, porosity was calculated based on density.

[0177] In an optional subsequent step after the etching, the porous glass article resulting from the etching may be rinsed in deionized water, for example an 18 mega-ohm (Mohm) deionized water.

[0178] The porous glass article resulting from the etching process described above may find separate use in other than electronic applications. For example, because the secondary phase is interconnected, the pores left behind by the etching, which can be quite small (e.g., e.g., less than about 100 nm, less than about 75 nm, less than about 50 nm, less than about 25 nm, or, for example, as small as about 3 nanometers in diameter) can extend through the thickness of the porous glass sheet. Accordingly, the porous glass sheet may be used for such diverse applications as nano filtration, reverse osmosis, and water treatment applications. Despite the porous structure of the porous glass sheet, the porous glass sheet remains transparent. Surfaces of the pores may be treated (e.g., coated) such that the porous article may be used in micro-reactor (e.g., nano-reactor) applications (where chemical reactions can be performed at very small scales). The pore surfaces may be coated with a catalyst. In some embodiments, the pores may be impregnated with nano-sized particles to provide additional functionality.

[0179] In a third step of the method, the porous glass article can be consolidated by heating the porous glass article to a suitable consolidation temperature. Consolidation of the porous glass sheets can stabilize performance of the glass sheet by preventing the uptake of water molecules into the pores. Because water is a highly polarized molecule, moisture in the glass can adversely affect the dielectric properties of the glass. In embodiments, the porous glass article can be preheated to a temperature in a range from about 100°C to about 300°C for a time in a range from about 1 hour to about 2 hours to dry the porous glass article prior to consolidation. The dried porous glass article may be further heated to a temperature in a range from about 500°C to about 700°C, for example at a temperature in a range from about 550°C to about 650°C, to remove (bum out) any organic contaminants, e.g., carbon, that may have contaminated the porous glass article. Contaminates can include oils from handling, or other environmental contaminants. The dried porous glass article may be heated for a time in a rangefrom about 30 minutes to about 2 hours, for a time in a range from about 45 minutes to about 75 minutes.

[0180] To consolidate the porous glass article, the porous glass article may be heated to a consolidation temperature in a range from about 850°C to about 1250°C, for example in a range from about 900°C to about 1250°C, for example in a range from about 920°C to about 1250°C, in a range from about 940°C to about 1250°C, in a range from about 960°C to about 1250°C, in a range from about 980°C to about 1250°C, in a range from about 1000°C to about 1250°C, in a range from about 1020°C to about 1250°C, in a range from about 1040°C to about 1250°C, in a range from about 1060°C to about 1250°C, in a range from about 1080°C to about 1250°C, in a range from about 1100°C to about 1250°C, in a range from about 1120°C to about 1250°C, in a range from about 1140°C to about 1250°C, in a range from about 1160°C to about 1250°C, in a range from about 1180°C to about 1250°C, or in a range from about 1200°C to about 1250°C, including all ranges and subranges therebetween. The consolidation temperature may, for example, be in a range from about 900°C to about 1100°C. The porous glass article may be heated to the consolidation temperature for a time in a range from about 1 hour to about 4 hours, although longer consolidation times are contemplated, for example in a range from about 1 hour to about 24 hours, in a range from about 1 hour to about 20 hours, in a range from about 1 hour to about 16 hours, in a range from about 1 hour to about 12 hours, or in a range from about 1 hour to about 8 hours, including all ranges and subranges therebetween. When heated to the consolidation temperature, pores in the porous glass article close and the glass becomes solid. SEM and time of flight (ToF) secondary ion mass spectrometry (SIMs) analysis has shown the porous glass remaining after the etching process is composed primarily of SiCh (see Table 2). Dielectric property measurements have shown that once the porous glass is consolidated, Dk and Df values are comparable to that of high purity fused silica (HPFS). However, unlike pure fused silica, a phase separated glass can be drawn, for example via a fusion downdraw process, into large glass sheets, etched, then consolidated to produce a high-silica glass sheet with pure fused silica-like dielectric properties.

[0181] Table 1 lists a phase separated glass sample (GS17, see Table 5) etched in accordance with the above etching process using an aqueous acid solution comprising 5 wt% HC1. All samples were 2” x 2” coupons of GS17 (see Table 5), washed with a solution of 4% Semiclean detergent in an ultrasonic bath for 2 minutes at 65°C, then dried in an oven for 1hour at 110°C (except trial C, which was not dried). All etching was performed in a solution of 5 wt% HC1 at 95°C. For reference, the glass before etching had a Dk of 4.6 and a Dr of 0.0037. Listed in Table 1 are the trial designation (A-DD), the first heat treatment (1stHT) expressed as temperature (Tp,°C) / time (Tm, hours), 2ndheat treatment (2ndHT) expressed as temperature (Tp,°C) / time (Tm, hours), first consolidation (1stCon.) expressed as temperature (Tp,°C) / time (Tm, hours), second consolidation (2ndCon.) expressed as temperature (Tp,°C) / time (Tm, hours), surface treatment with hydrofluoric acid (HF) expressed as “before heat treatment” (B) or “after last consolidation” (A), environmental soak in an 85°C / 85% relative humidity environment expressed in time (hours), and the dielectric properties dielectric constant Dk, and loss tangent Df. Dielectric constant and loss tangent were measured at 10 GHz, except those including an asterisk. Dielectric properties including an asterisk were measured at 5 GHz. Samples comprising an apostrophe (‘) after the dielectric properties indicates the sample was exposed to a lab environment (72C, 20% RH) for approximately 24 hours prior to measurement for dielectric properties. Samples including a cross (+) after the dielectric properties were exposed to the lab environment for approximately 60 hours prior to measurement for dielectric properties.

[0182] The glass from trial DD was measured for dielectric properties a first time after consolidation, and a second time after an 85°C / 85% RH soak. Double dashes indicate a process step was not performed. Accordingly, by way of example, the samples of trials A-C were etched, but not heat treated, consolidated, subjected to an HF treatment, or exposed to an 85C / 85% RH environment prior to measurement for dielectric properties. The data show a distinct decrease in dielectric properties Dk and Dr when comparing the glass samples of trials A-C with, for example, the glass sample of trial D, which after etching, was simply subjected to heating to a temperature of 200°C for 1 hour (1 hr.) without the benefit of further heating. It is believed this decrease in dielectric properties occurred as a result of removal of moisture from the porous sample obtained after etching. Similarly, the dielectric properties for the glass sample of trial E were further decreased by including a consolidation step, wherein the sample was subjected to a temperature of 820°C for 1 hour. Similar results can be observed for other samples, wherein the addition of further heating, either through one or more heat treatment steps, or one or more consolidation steps, may result in a decrease in dielectric properties. The glass sample of trial DD is presented on two lines because the sample was measured for Dk and Df after etching and consolidation (including an HF treatment of the porous glass article beforeconsolidation), and then measured a second time after the consolidated glass article was exposed to an 85°C / 85% RH environment for 24 hours. The values for Dk and Df both before and after the 85°C / 85% RH exposure are remarkably consistent, showing stable dielectric properties even in the presence of moisture.Table 1

[0183] Table 2 lists before and after composition of a fusion formed GS 17 glass sample before and after etching in 5 wt% HC1 at 95°C. Composition analysis was performed with ToF SIMS to estimate the remaining glass composition more accurately after HC1 etching. The analysis was performed with 500 micrometer x 500 micrometer field of view across the entire thickness of the sample. The before compositional constituents reflect total amounts (including both phases of the phase separated glass sample). All constituent amounts are given in mol%. The data show a significant increase in the proportional amount of SiCh after a significant portion of the boron-rich secondary phase was removed from the sample, resulting in a near pure Si O2 sheet that would have been impossible to form via a fusion downdraw process. There was no indication that a composition gradient existed. It is expected that other phase separated glass compositions described herein will provide similar after-etching results.

[0184] Table 2

[0185] Tables 3-9 below illustrates exemplary phase separated glasses according to the present disclosure, in mole percent (mol%), as calculated on an oxide basis from the as-batched glasses (the glass precursor composition from which the glass is derived). The glass sampleswere batched and drawn in a production fusion draw apparatus as glass ribbon and separated into glass sheets having dimension 1500 millimeters (mm) x 1850 mm. The glass sheets had a thickness of 0.7 mm.

[0186] Table 3

[0187] Table 4

[0188] Table 5

[0189] Table 6

[0190] Table 7

[0191] Table 8

[0192] Table 9

[0193] To obtain low dielectric constant (Dk) and dielectric loss tangent (Df) and increased durability in glass, several different oxides were investigated. Table 10 and Table 11 list compositions and measured Dk and Df data for glasses with ZnO additions. FIG. 20 and FIG. 21 are plots showing the impact on Dk and Df of replacing MgO with ZnO in GS 17. As can be seen in the plots, Dk increased with an addition of ZnO for MgO and Df decreased with an addition of ZnO. However, when ZnO is added as a replacement for B2O3 in the glass the Dk and Df properties did not appear to change. This is shown in Figure 22 and 23. In FIG. 22 and FIG. 23 the open circles are glasses with ZnO replacing B2O3 and as can be seen the open circles overlay the black circles which are the same glasses without ZnO. This indicates Dk and Df are impacted by the B2O3 content but not at all by the ZnO content. These data indicate ZnO is a good option for further lowering the Df of the glass or retaining the same Dk and Df while potentially improving the meltability of the glass by reducing the resistivity, which is related to the B2O3 content in these types of glasses. The glass melt resistivity of GS57, which has approximately 4 mol% ofZnO, is shown in FIG. 24. Itis evident GS57 has lower resistivity compared to glass sample GS17. Note that GS57 has no CaO whereas GS17 has approximately 5 mol% of CaO. The fact that GS17 shows low resistivity without CaO indicates the effectiveness of ZnO in lowering resistivity, and thereby improving meltability.

[0194] Table 10

[0195] Table 11

[0196] Rare-Earth oxides have shown potential for lowering the Df of a glass. Table 12 provides compositions for several glasses made with additions of La2O3 or Y2O3 and the Dk and Df data for those glasses measured at 10 GHz. FIG. 27 and FIG. 28 are plots of Dk and Df, respectively, as a function of mole% La2C>3 in a glass that has substituted La for Ba. The plots clearly show that as La2C>3 increases in the glass at the expense of BaO the Dk increases and the Df decreases. However, when La2C>3 or Y2O3 are added on top of a glass composition ( so not substituted for a particular oxide) the Dk and Df both increase over that of the parent glass that did not contain the rare earth element. FIGS. 27 and 28 show the increase in both Dk and Df for an La2C>3 and Y2O3 -containing glass, where the rare-earth oxide was in addition to the base glass composition (the La2C>3 and / or Y2O3 was not a substitution for another constituent) The data indicate that to lower the Df of a glass, the rare-earth oxide should instead be added as a substitution for one of the larger alkaline-earth oxides in the glass.

[0197] Table 12

[0198] Transition metals have relatively low polarizabilities compared to other metal oxides so it was believed this should result in a reduction in either one or both Dk and Dr of a glass. Table 13 and Table 14 list compositions of several glasses with various transition metal oxide additions and the resulting measured Dk and Dr at 10 GHz for each of those glasses. The data indicate transition metals (except for Co) provide a means of decreasing Dk in an alkaline- earth alumino-borosilicate glass when substituted for CaO, as shown in FIG. 29. However, the data shown in Figure FIG. 30 indicate the transition metals may not lower the Dr of the glass but may cause the Dr to remain substantially constant of increase compared to the parent glass. Transition metals may also be used to color the glass.

[0199] Table 13

[0200] Table 14

[0201] Fluorine is a halide element that has been used in glass melting to lower the viscosity of a glass melt as well as help with fining of a glass melt. When substituted for B2O3 it also provides a lowering of Df while maintaining substantially the same Dk as the base glass. Table 15 shows three glass compositions with data for Dk and Df at 10 GHz. FIG. 31 and FIG. 32 show of Dk and Dr as a function of mole% F-, respectively. As shown, the B2O3 content of glass samples GS95 and GS96 has been reduced compared to GS94 and fluorine added. The data show Dk remains substantially the same for a glass with 4.5 mole% fluorine (F-) in place of B2O3, while Df decreases. This not only helps lower the Df of the glass, but it also helps lower the B2O3 content of the glass, thereby reducing melting defects such as silica knots, and lowers the viscosity of the glass melt, making it easier to melt the glass as it requires less energy for melting. The F- may also help reduce bubbles or seeds due to inadequate fining of the glass.

[0202] Table 15

[0203] In still another aspect, electrically conductive vias, and optionally electrically conductive traces (e.g., lines), may be added to one or more porous intermediate glass articles formed from phase separated glasses disclosed herein. As used herein, the term “via” refers to a small hole extending through one or more layers of the circuit board, the via comprising an electrically conductive material disposed therein that forms an electrical connection between electrically conductive layers (e.g., lines or traces) and / or electrical components on the circuit board. The via may be a through via, in which the hole and the electrically conductive material therein, extends through an entire thickness of the circuit board, from one major surface of the circuit board to the opposing major surface, or a “blind” via, in which the via, and the electrically conductive material therein, extends partially through the thickness of the circuit board. That is, a blind via terminates internally, within a body of the circuit board intermediate between the exposed, outward facing major surfaces.

[0204] In some embodiments, porous intermediate glass articles may be laminated together and co-fired (consolidated together) to form a glass circuit board comprising electrically conducting vias extending at least partly through the thickness of the glass circuit board. The glass circuit board may further comprise interconnecting electrical pathways extending on a surface of and / or internally within the glass circuit board., for example from one via to another via. In aspects, once a porous intermediate glass article has been obtained from a phase separated glass sheet by etching (leaching) the glass sheet in accordance with methods disclosed herein, holes may be formed in the porous intermediate glass article by laser ablation or chemical etching, then filling with a suitable electrically conductive material to form a via. Prior to the acid leaching step, the phase separated glass has a low ablation threshold. After the leaching step, the ablation threshold is close to that of fused silica. Accordingly, hole forming may be performed faster prior to the leaching step than after, e.g., before obtaining the porous intermediate glass article. In embodiments, hole formation, either in the phase separated glass substrate prior to etching or the porous intermediate article after etching, can be performed by using one of a variety of lasers, with a wavelength from UV to far-infrared, and a pulse duration from quasi-continuous to ultrafast. The selection of an appropriate laser may further depend on the desired hole size. For large via holes with a diameter greater than one or more hundreds of micrometers, an RF-excited (quasi-continuous wave or nanosecond pulsed) CO2 laser can be used; for small holes with diameters of ones ortens of micrometers, ultrafast laser-induced damage followed by chemical etching may be employed.

[0205] The following example demonstrates via formation using a direct ablative approach on phase separated glass articles after the leaching step. A pulsed 355 nanometer wavelength Nd:YAG solid state laser was used to form holes with a diameter of about 400 micrometers (pm) in a porous glass substrate produced by processes described herein. That is, a spinodally phase separated glass substrate was exposed to an acid solution and thereby leached to remove the second, B2O3 -containing phase and produce a porous intermediate glass substrate with a primary phase comprising greater than 95 mol% SiCh. The resultant porous glass substrate was then subjected to laser processing to form the holes. The laser was operated at a repetition rate of 50 kilohertz (kHz), with a pulse energy of 70 microjoules (pJ) and a power of 3.5 watts (W). The expanded laser beam was scanned using a galvanometer with a 100-millimeter focal length (f = 100 mm) telecentric lens. The spot size of the laser beam at the focus was about 15 pm. As used herein, spot size refers to the radial distance (radius) from the center of the maximum irradiance of the beam at the surface impinged by the beam to the irradiance at the 1 / e2point. The porous intermediate glass substrate was placed on a lift stage and the laser beam scanned in a series of concentric circles while the substrate was moved by the lift stage through the focus of the laser beam. FIG. 33 shows holes formed by the UV laser before and after thermal consolidation. The column on the left (FIG. 33, (a) and (c) show an average hole diameter of about 150 pm and the column on the right (FIG. 33 (b) and (d)) show an average hole diameter of about 400 pm. In the top row (FIG. 33, (a) and (b)), two hole sizes formed by laser ablation in the as-leached glass are shown, 150 pm (left) and 400 pm (right). Holes extending fully through the substrate are shown to be formed without visible cracks. The bottom row images (FIG. 33, (c) and (d)) show the hole shape after the substrate underwent thermal consolidation. The hole size and shape were substantially maintained. FIG. 34 shows the x-ray diffraction patterns on the consolidated substrate. The curve 100 is the diffraction pattern on the glass surface away from via, and the curve 102 line is the diffraction pattern near the via hole. Both patterns show completely amorphous features, e.g., wherein no crystalline phases, such as cristobalite, were formed after thermal consolidation.

[0206] In embodiments, the holes may be filled with an electrically conductive ink, for example an ink comprising a metal such as, without limitation, copper, silver, or platinum, to form an intermediate circuit board. However, because the consolidation temperature is greater than the melting temperatures of some metals, such as copper, gold, or silver, such “low”melting temperature metals may not be suitable for pre-consolidation via hole filling. A suitable, non-limiting electrically conductive ink for pre-consolidation hole filling may be a platinum -based ink with about 85 wt% of Pt, 5 wt% of glass and 10 wt% of organic binders (supplied by Applied Technologies). Other metal-based inks can include, without limitation, molybdenum or tungsten-based inks. Additionally, electrically conductive pathways may be deposited between vias on a surface of the porous glass substrate. For example, via holes may be filled with the electrically conductive ink, and further, the electrically conductive ink may be deposited as a continuous line extending between one via and one or more other vias. The filling and / or deposition of the electrically conductive ink may be performed, for example, using a screen-printing process. The porous glass substrate, including the electrically conductive ink, may be consolidated (fired) to form a glass circuit board.

[0207] In some embodiments, two or more intermediate circuit boards, including a plurality of vias containing electrically conductive ink, and optionally electrically conductive ink deposited as electrically conductive traces (lines) leading from one via to one or more other vias, may be stacked, then fired together, thereby consolidating the stacked intermediate product into a glass circuit board comprising external and / or internal electrically conductive pathways arranged on one or more layers of the glass circuit board. Alignment of the two or more intermediate circuit boards during the stacking can be achieved with edge alignment or fiducial marks placed on the individual intermediate circuit boards. Thermally conductive substrates such as SiC may be used to sandwich the stack. Pressure may be applied to the stack during consolidation, for example through the thermally conductive substrates. In some embodiments, the stack of intermediate circuit boards may be separated into a plurality of stacks of intermediate circuit boards prior to placement between the thermally conductive substrates, or at least prior to consolidation, thereby facilitating simultaneous formation of multiple glass circuit boards. In aspects, some vias of the plurality of vias on one intermediate circuit board in the stack may be arranged in registration (aligned) with other vias of another adjacent intermediate circuit board in the stack such that after firing, the vias in registration form a continuous electrical pathway through adjacent layers of the resultant glass circuit board.

[0208] By way of example and not limitation, FIG. 35 depicts a first intermediate circuit board 120 and a second intermediate circuit board 122. First intermediate circuit board 120 comprises a first major surface 124 and a second major surface 126 opposite first major surface 124. First major surface 124 may be substantially flat (substantially planar) and parallelto second major surface 126. Accordingly, second major surface 126 may also be substantially flat (substantially planar).

[0209] Second intermediate circuit board 122 comprises a third major surface 128 and a fourth major surface 130. Third major surface 128 may be substantially flat (substantially planar) and parallel to fourth major surface 130. Accordingly, fourth major surface 130 may also be substantially flat (substantially planar).

[0210] First intermediate circuit board 120 comprises a first plurality of vias 132, for example a first via 132a, a second via 132b and a third via 132c, each via of the plurality of vias, as described herein, comprising a hole extending through a thickness of first intermediate circuit board between first major surface 124 and second major surface 126. First intermediate circuit board 120 may have fewer than three vias, for example two vias, or more than three vias, for example four vias, five vias, six vias, or greater that six vias, such as tens or hundreds of vias.

[0211] Similarly, second intermediate circuit board 122 comprises a second plurality of vias 134, for example a fourth via 134a, a fifth via 134b and a sixth via 134c, each of the fourth, fifth, and sixth vias 134a, 134b, 134c, as described herein, comprising a hole extending through a thickness of second intermediate circuit board 122 between third major surface 128 and fourth major surface 130. Like first intermediate circuit board 120, second intermediate circuit board 122 may have fewer than three vias, for example two vias, or more than three vias, for example four vias, five vias, six vias, or greater that six vias, such as tens or hundreds of vias.

[0212] In the example of FIG. 35, a first line (trace) 136a of electrically conducting material is deposited on first major surface 124 of first intermediate circuit board 120 extending between first via 132a and second via 132b. First line 136a of electrically conducting material is in electrical communication with first via 132a and second via 132b. A second line 136b of electrically conducting material (shown as a dashed line in FIG. 35) is similarly deposited on second major surface 126 extending between second via 132b and third via 132c, the second line 136b of electrically conducting material in electrical communication with second via 132b and third via 132c. Thus, first via 132a is in electrical communication with third via 132c through first line 136a of electrically conducting material and second line 136b of electrically conducting material.

[0213] Additionally, a third line (trace) 136c of electrically conducting material is deposited on third major surface 128 of second intermediate circuit board 122 extendingbetween fourth via 134a and fifth via 134b, third line 136c of electrically conducting material in electrical communication with fourth via 134a and fifth via 134b. A fourth line 136d of electrically conducting material (shown as a dashed line in FIG. 35) is similarly deposited on fourth major surface 130 extending between fifth via 134b and sixth via 134c, the fourth line 136d of electrically conducting material in electrical communication with fifth via 134b and sixth via 134c. Thus, fourth via 134a is in electrical communication with sixth via 134c through third line 136c of electrically conducting material and fourth line 136d of electrically conducting material.

[0214] In accordance with embodiments disclosed herein, first intermediate circuit board 120 may be placed into contact with second intermediate circuit board 122 to form a stack 140 of intermediate circuit boards. For example, first intermediate circuit board 120 may be equally sized to second intermediate circuit board 122, such that a length and a width of first intermediate circuit board 120 is equal to the corresponding length and width of second intermediate circuit board 122. Thus, in embodiments, first intermediate circuit board 120 may be arranged such that edge surfaces of first intermediate circuit board 120 are substantially coplanar with corresponding edge surfaces of second intermediate circuit board 122. However, similar sizes are not required. In the example of FIG. 35, showing first intermediate circuit board 120 and second intermediate circuit board 122 so arranged (although separated for illustration purposes), first major surface 124 of first intermediate circuit board 120 is an external (exposed) major surface and fourth major surface 130 is an external (exposed) major surface. Conversely, second major surface 126 is arranged opposite third major surface 128 and internal to stack 140 of intermediate circuit boards and third major surface 128 is opposite second major surface 126 and internal to stack 140 of intermediate circuit boards. Additionally, first line 136a of electrically conducting material extending between first via 132a and second via 132b on first major surface 124 is an external line of electrically conducting material, whereas second line 136b of electrically conducting material extending between second via 132b and third via 132c is an internal line of electrically conducting material, i.e., internal to stack 140. Similarly, third line 136c of electrically conducting material extending between fourth via 134a and fifth via 134b on third major surface 128 is an internal line of electrically conducting material, whereas fourth line 136d of electrically conducting material extending between fifth via 134b and sixth via 134c is an external line of electrically conducting material. Consequently, when first intermediate circuit board 120 is positioned in contact with second intermediate circuit board 122 (or vice versa) second line 136b of electrically conductingmaterial and third line 136c of electrically conducting material extend within an interior region of the stack. In the embodiment of FIG. 35, first intermediate circuit board 120 is positioned on and in contact with second intermediate circuit board 122 such that third via 132c is in contact with, or proximate to, fourth via 134a, i.e., aligned therewith such that a longitudinal axis of third via 132c is coaxial with a longitudinal axis of fourth via 134a.

[0215] As previously described and shown in FIG. 36, stack 140 of intermediate circuit boards may be arranged between a pair of thermally conductive substrates 141a, 141b and subjected to heating and consolidation cycles as described herein. In embodiments, a force may be applied to stack 140 through thermally conductive substrates 141a, 141b as indicated by arrows 143. As a result of the consolidation cycles, first intermediate circuit board 120 (second major surface 126) is fused to second intermediate circuit board 122 (third major surface 128) to form a glass circuit board 142 (see FIGS. 37-38) comprising a first external major surface 144 corresponding to first major surface 124 of first intermediate circuit board 120 and a second external major surface 146 corresponding to fourth major surface 130 of second intermediate circuit board 122. During this process, pores of the porous first intermediate circuit board 120 and pores of the second intermediate circuit board 122 close. Additionally, the electrically conducting material comprising the first and second plurality of vias 132, 134, as well as electrically conducting lines extending therebetween are sintered. Aligned vias, such as third via 132c and fourth via 134a, are physically and electrically connected, thereby forming a through via that extends through the total thickness of glass circuit board 142 from first major surface 144 to second major surface 146. Indeed, while each via of the first plurality of vias 132 and each via of the second plurality of vias 134 are through vias in respect of their individual intermediate circuit boards, once the plurality of intermediate circuit boards are fused by consolidation, some vias may extend entirely through the total thickness of the glass circuit board while other vias may extend from one major surface of the glass circuit board, e.g., from first major surface 144 or second major surface 146, partially through the total thickness of the glass circuit board and not through the total thickness, thereby becoming a blind via. In instances where vias on each intermediate circuit board of the plurality of intermediate circuit boards forming stack 140 are aligned vias, the resultant via formed by the consolidation step produces a through via.

[0216] A multistep heat treatment and consolidation cycle may be used to co-fire the porous intermediate articles and the electrically conductive ink as described previously herein, or a heat treatment and consolidation cycle similar thereto, may be used. For example, a three-step heat treatment schedule may comprise: baking the porous glass substrate in an oven at 200°C for 1 hour to drive out water content; heat the baked porous glass substrate at 600°C for 1 hour to remove carbon impurities from the porous glass substrate; consolidate the porous glass substrates and the electrically conductive ink at 960-1100C for 2 hours to close the pores of the porous glass substrate. After co-firing (consolidation), the resulting substrate remains amorphous.

[0217] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A method of making a glass circuit board, comprising exposing at least one spinodally phase separated glass substrate comprising a majority SiC>2 first phase and a second phase comprising B2O3 to an acid solution comprising about 5 wt% to about 40 wt% of an acid at a temperature in a range from about 60°C to about 95°C for a time in a range from about 8 hours to about 24 hours to remove at least a portion of the second phase from the at least one spinodally phase separated glass substrate and obtain at least one porous glass substrate comprising a total Si O2 content greater than about 95 mol%; forming a plurality of holes in the at least one porous glass substrate; depositing an electrically conductive material in the plurality of holes to form an intermediate circuit board comprising a plurality of vias; and consolidating the intermediate circuit board to form the glass circuit board.

2. The method of claim 1, wherein the acid solution comprises at least one of HC1, H2SO4, HNO3, HF, or H3PO4.

3. The method of claim 1 or claim 2, wherein the acid solution comprises HC1.

4. The method of claim 3, wherein the acid solution comprises about 5 wt% HC1.

5. The method of claim 1, wherein the acid solution comprises at least one of citric acid or acetic acid.

6. The method of any one of claims 1 to 5, wherein an open porosity of the at least one porous glass substrate is greater than about 28%.

7. The method of claim 1, wherein the forming the plurality of holes comprises laser ablation or chemical etching.

8. The method of claim 7, wherein the forming the plurality of holes comprises using an RF- excited CO2 laser.

9. The method of claim 7, wherein the forming the plurality of holes comprises using a laser operating at an ultraviolet wavelength.

10. The method of claim 1, wherein further comprising depositing the electrically conductive material on the porous glass substrate as a line between a first via of the plurality of vias and a second via of the plurality of vias prior to consolidating the intermediate circuit board.

11. The method of claim 1 to 10, further comprising heat treating the intermediate circuit board at a temperature in a range from about 500°C to about 700°C for a time in a range from about 45 minutes to about 75 minutes.

12. The method of any one of claims 1 to 11, wherein the consolidating comprises heating the intermediate circuit board to a consolidation temperature in a range from about 850°C to about 1250°C for a time in a range from about 1 hour to about 24 hours.

13. The method of claim 1, wherein the at least one spinodally phase separated glass substrate comprises a plurality of spinodally phase separated glass substrates, the exposing resulting in a plurality of porous glass substrates, and wherein: the forming the plurality of holes comprises forming holes in at least a subset of the plurality of porous glass substrates, the depositing comprises depositing the electrically conductive material in the holes of of the at least the subset of porous glass substrates to obtain a plurality of intermediate circuit boards, arranging the plurality of intermediate circuit boards to form a stack of intermediate circuit boards, and wherein the consolidating comprises consolidating the stack of intermediate circuit boards to form the glass circuit board.

14. The method of claim 13, wherein the stack of intermediate circuit boards is positioned between a pair of thermally conductive substrates prior to the consolidating.

15. The method of claim 14, wherein the pair of thermally conductive substrates comprise SiC .

16. The method of any one of claims 1 to 15, wherein the glass circuit board comprises, on an oxide basis: greater than about 95% mol% SiCh; less than about 1 mol% AI2O3; less than about 3 mol% B2O3.

17. The method of any one of claims 1 to 16, wherein the glass circuit board comprises one or more alkaline earth oxides (RO) totaling less than 0.5 mol%, wherein RO is at least one of MgO, CaO, SrO, or BaO.

18. The method of any one of claims 1 to 17, wherein a dielectric constant Dk of the glass circuit board is less than about 6.0 when measured at 10 GHz19. The method of claim 18, wherein Dk is less than about 4.0 when measured at 10 GHz.

20. The method of any one of claims 1 to 19, wherein a loss tangent Df of the at least one glass circuit board is less than about 0.001 when measured at 30 GHz.

21. The method of claim 20, wherein Df is less than about 0.001 when measured at 10 GHz.

22. The method of claim 1, wherein the spinodally phase separated glass substrate comprises: a total amount of SiCh from about 59 mol% to about 69 mol%; a total amount of AI2O3 from about 3 mol% to about 13 mol%; a total amount of B2O3 from about 9.8 mol% to about 20 mol%; and one or more alkaline earth oxides (RO) totaling from about 3.9 mol% to about 11.5 mol%, wherein RO is selected from MgO, CaO, SrO, and BaO23. The method of claim 22, wherein B2O3 / (AhO3 + SiO2) is in a range from about 0.12 to about 0.3.

24. The method of claim 22, wherein the spinodally phase separated glass substrate comprises SiO2 in a range from about 68.0 mol% to about 69.0 mol%.

25. The method of claim 1, wherein the spinodally decomposed glass substrate comprises, on an oxide basis: a total amount of SiCh from about 57 mol% to about 70 mol% a total amount of AI2O3 from about 4.7 mol% to about 10.5 mol% a total amount of B2O3 from about 11.2 mol% to about 15.2 mol% a total amount of ZnO from about 1.2 mol% to about 7.4 mol%; and one or more alkaline earth oxides (RO) totaling from about 3.7 mol% to about 20 mol%, wherein RO is selected from MgO, CaO, SrO, and BaO.

26. The method of claim 25, wherein the spinodally phase separated glass substrate comprises SnO in a range from about 0.09 mol%to about 0. 15 mol%.

27. The method of claim 25, wherein the spinodally phase separated glass substrate comprises MgO in a range from about 1.5 mol% to about 9.6 mol%.

28. The method of claim 27, wherein MgO / ZnO is in a range from about 0 to about 3.7.

29. The method of claim 27, wherein B2O3 / ZnO is in a range from about 1 .6 to about 12.6.

30. The method of any one of claims 1 to 29, wherein after the consolidating the glass circuit board comprises amorphous glass.

31. A glass circuit board comprising: greater than about 95% mol% SiCh; less than about 1 mol% AI2O3; less than about 3 mol% B2O3; a plurality of vias disposed in the glass circuit board; and wherein a dielectric constant Dk of the glass circuit board is less than about 6.0 when measured at 10 GHz.

32. The glass circuit board of claim 31, wherein the plurality of vias comprises a first via and a second via, and an electrically conductive material is disposed on the glass circuit board as aline extending between the first via and the second via such that the electrically conductive material forms an electrical pathway between the first via and the second via.

33. The glass circuit board of claim 31, wherein the glass circuit board comprises a first major surface and a second major surface opposite the first major surface, the plurality of vias comprises a first via extending from the first major surface partially through a thickness of the glass circuit board and a second via extending from the second major surface partially through the thickness of the glass circuit board, and an electrically conductive material forms an electrical pathway between the first via and the second via.

34. The glass circuit board of claim 31 or 32, wherein the electrical pathway is positioned within an interior of the glass circuit board.

35. The glass circuit board of claim 31 or claim 32, wherein the plurality of vias comprises a third via, and the electrical pathway is in electrical communication with the third via.

36. The glass circuit board of claim 31, wherein the plurality of vias comprises at least one blind via.

37. The glass circuit board of any one of claims 31 to 36, wherein a loss tangent Df of the glass circuit board is less than about 0.001 when measured at 30 GHz.

38. The glass circuit board of claim 37, wherein Dr is equal to or less than about 0.0005 when measured at 10 GHz.

39. The glass circuit board of any one of claims 31 to 38, wherein the glass circuit board comprises amorphous SiCh.

40. A method of making a glass circuit board, comprising: forming a plurality of holes in at least one spinodally phase separated glass substrate comprising a first major surface, a second major surface opposite the first major surface, and a thickness therebetween, the at least one spinodally phase separated glass substrate further comprising a majority SiCh first phase and a second phase comprising B2O3, and wherein eachhole of the plurality of holes extends through the thickness of the spinodally phase separated glass substrate; exposing the at least one spinodally phase separated glass substrate to an acid solution comprising about 5 wt% to about 40 wt% of an acid at a temperature in a range from about 60°C to about 95 °C for a time in a range from about 8 hours to about 24 hours to remove at least a portion of the second phase from the at least one spinodally phase separated glass substrate, and wherein after the exposing a total S i O2 content of the spinodally phase separated glass substrate is greater than about 95 mol%; depositing an electrically conductive material in the plurality of holes to form an intermediate circuit board comprising a plurality of vias; and consolidating the intermediate circuit board to form the glass circuit board.

41. The method of claim 40, wherein the acid solution comprises at least one of HC1, H2SO4, HNO3, HF, or H3PO4.

42. The method of claim 40 or claim 41, wherein the acid solution comprises HC1.

43. The method of claim 42, wherein the acid solution comprises about 5 wt% HC1.

44. The method of claim 40, wherein the acid solution comprises at least one of citric acid or acetic acid.

45. The method of any one of claims 40 to 44, wherein an open porosity of the at least one spinodally phase separated glass substrate after the exposing is greater than about 28%.

46. The method of claim 40, wherein the forming the plurality of holes comprises laser ablation or chemical etching.

47. The method of claim 46, wherein the forming the plurality of holes comprises using an RF-excited CO2 laser.

48. The method of claim 46, wherein the forming the plurality of holes comprises using a laser operating at an ultraviolet wavelength.

49. The method of claim 40, wherein the depositing the electrically conductive material comprises depositing the electrically conductive material as a line between a first via of the plurality of vias and a second via of the plurality of vias prior.

50. The method of claim 49, wherein the depositing the electrically conductive material as a line is performed prior to consolidating the intermediate circuit board51. The method of claim 40 to 44, further comprising heat treating the intermediate circuit board at a temperature in a range from about 500°C to about 700°C for a time in a range from about 45 minutes to about 75 minutes.

52. The method of any one of claims 40 to 44, wherein the consolidating comprises heating the intermediate circuit board to a consolidation temperature in a range from about 850°C to about 1250°C for a time in a range from about 1 hour to about 24 hours.

53. The method of claim 40, wherein the at least one spinodally phase separated glass substrate comprises a plurality of spinodally phase separated glass substrates, the method further comprising forming the plurality of holes in at least a subset of the plurality of the spinodally phase separated glass substrates, depositing the electrically conductive material in the plurality of holes of the at least the subset of spinodally phase separated glass substrates to obtain a plurality of intermediate circuit boards, arranging the plurality of intermediate circuit boards to form a stack of intermediate circuit boards, and wherein the consolidating comprises consolidating the stack of intermediate circuit boards to form the glass circuit board.

54. The method of claim 53, wherein the stack of intermediate circuit boards is positioned between a pair of thermally conductive substrates prior to the consolidating.

55. The method of claim 54, wherein the pair of thermally conductive substrates comprise SiC.

56. The method of any one of claims 40 to 55, further comprising delivering a molten material to a forming body, drawing a glass ribbon from the forming body, and separating the spinodally phase separated glass substrate from the glass ribbon.

57. The method of claim 56, wherein the molten material comprises a 35,000 Poise Temperature greater than about 1250°C.

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