Low dielectric constant, low dissipation factor laminates comprising an aerogel layer

Abstract

A laminate comprising one or more electrically conductive layers and one or more electrically insulating layers coupled to the electrically conductive layers. Each electrically conductive layer can comprise at least 90 wt% copper. Each electrically insulating layer can comprise a polymeric aerogel layer. For at least one of the opposing front and back surfaces of the laminate, at least a portion of the surface is defined by one of the electrically conductive layers.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 025,947, filed May 15, 2020, the entire contents of which are incorporated herein without disclaimer. BACKGROUND

[0003] A. TECHNICAL FIELD

[0004] The present invention relates generally to copper clad laminates for high frequency (e.g., 10 GHz to 300 GHz) electrical applications such as communication systems, antenna systems, electronic amplifiers, radar systems, and the like.

[0005] B. RELATED ART DESCRIPTION

[0006] Copper clad laminates are commonly used in printed circuit boards (PCBs). Traditionally, copper clad laminates include one or more thin (e.g., less than four and one-half thousandths of an inch (i.e., 4.5 mils)) copper layers defining at least one outer surface of the laminate, and one or more insulating substrates that can provide structural support to the copper layers. To manufacture a PCB, each copper layer can be etched to define individual conductive lines or “traces” through which electrical current can flow between different components connected to the PCB.

[0007] The properties of the substrate of a copper clad laminate can affect the durability and electrical performance of a PCB. For example, the laminate can be heated when components are soldered to the PCB or when the PCB is used. Thermal expansion of the substrate, particularly when the temperature of the substrate is raised above its glass transition temperature (T g ), can cause delamination of the copper layers and / or breakage of the joints connecting components to the PCB. In addition, the rate at which signals propagate in a PCB and the amount of electromagnetic energy lost in a signal in a PCB are affected by the dielectric constant (Dk) and dissipation factor (Df) of the laminate.

[0008] Substrates used in PCBs include woven or non-woven glass fibers dispersed in an epoxy resin, polytetrafluoroethylene (PTFE), and paper impregnated with a phenolic resin (e.g., phenolic paper). While copper-clad laminates incorporating one or more of these substrates generally have a relatively low dissipation factor (e.g., 0.0009 to 0.0018 at 10 GHz) that can mitigate dielectric loss, their dielectric constant is greater than 2.0. For example, copper-clad laminates with a PTFE substrate generally have a dielectric constant of 2.2 to 2.3 at 10 GHz. Due to the dielectric constant being greater than 2.0, PCBs using conventional copper-clad laminates can not be able to propagate signals at a sufficient rate to maintain signal integrity in high frequency applications such as 5G communication systems and high speed digital circuits. Accordingly, there is a need in the art for copper-clad laminates having an ultra-low dielectric constant suitable for use in PCBs. SUMMARY

[0009] To address this need in the art, some laminates of the present disclosure include one or more electrically conductive layers each of which includes at least 90 wt.% copper and one or more electrically insulating layers coupled to the electrically conductive layers. In some aspects, at least one of the electrically insulating layers can include a porous material. In some aspects, each of the electrically insulating layers can independently include a porous material. In certain aspects, the porous material can be an open-cell porous material. In certain other aspects, the porous material can be a closed-cell porous material. In certain aspects, the porous material can be a foam. In certain aspects, the foam can be an organic foam or a polysiloxane foam. Non-limiting examples of organic foams can include polyurethane foam, polystyrene foam, polyvinyl chloride foam, (meth)acrylic polymer foam, polyamide foam, polyimide foam, polyaramid foam, polyurea foam, polyester foam, polyolefin foam (e.g., polyethylene foam, polypropylene foam, ethylene propylene diene monomer (EPDM) foam, etc.), polyethylene terephthalate foam, polybutylene terephthalate foam, polyvinyl chloride foam, polyvinyl acetate foam, ethylene vinyl alcohol (EVOH) foam, ethylene-vinyl acetate (EVA) foam, polymethyl methacrylate foam, polyacrylate foam, polycarbonate foam, polysulfonate foam, or synthetic rubber foam, or any combination thereof. In certain aspects, the foam can be a polyurethane foam. In certain aspects, the porous material can be an aerogel. In some laminates, each of the electrically insulating layers can include a polymeric aerogel layer. With such aerogel layers, the laminates can have an ultra-low dielectric constant (e.g., less than 2.0, such as less than 1.7 or equal to 1.7 at 10 GHz) and dissipation factor (e.g., less than 0.002 or equal to 0.002 at 10 GHz) that make them suitable for use in high frequency electrical applications.

[0010] The composition of the aerogel layer can improve the heat resistance of the laminate, making it suitable for use in PCBs. For example, in some embodiments, for at least one of the electrically insulating layers, the polymeric aerogel layer has a thermal decomposition temperature of at least 400 °C, 450 °C, or 500 °C. In some embodiments, for at least one of the electrically insulating layers, the polymeric aerogel layer comprises at least 90 wt% organic polymer and / or at least 90 wt% polyimide, polyamide, polyaramid, polyurethane, polyurea, and / or polyester. In some embodiments, for at least one of the electrically insulating layers, the polymeric aerogel layer comprises an open-cell structure and / or comprises micropores, mesopores, and / or macropores. In some embodiments, the aerogel layer has a pore volume, wherein at least 10%, at least 50%, at least 75%, or at least 95% of the pore volume consists of micropores, mesopores, and / or macropores. In some embodiments, for at least one of the electrically insulating layers, the polymeric aerogel layer has an average pore diameter of 2 nm to 50 nm or 50 nm to 5000 nm, optionally 100 nm to 800 nm, 100 nm to 500 nm, 150 nm to 400 nm, 200 nm to 300 nm, or 225 nm to 275 nm. Thus, such laminates can withstand heat during PCB manufacturing (e.g., from soldering) and during use of the PCB.

[0011] Further, in some embodiments, the thickness of at least one of the aerogel layers is less than 20 mils or equal to 20 mils, less than 12 mils or equal to 12 mils, or less than 7 mils or equal to 7 mils, such as from 3 mils to 20 mils, from 3 mils to 15 mils, from 3 mils to 12 mils, or from 3 mils to 7 mils. Such relatively thin aerogel layers can contribute to the low dielectric constant and low dissipation factor of the laminate. To illustrate, in some embodiments, at least one of the aerogel layers has a dielectric constant at 10 GHz of any one of, at most any one of, or between any two of, 3, 2.75, 2.5, 2.25, 2, 1.75, 1.6, 1.4, 1.3, 1.2, and 1.1, and / or a dissipation factor at 10 GHz of any one of, at most any one of, or between any two of, 0.005, 0.004, 0.003, 0.0025, 0.00225, 0.002, 0.00175, 0.0015, 0.00125, 0.001, 0.00075, and 0.0005. To illustrate, in some embodiments, the dielectric constant of the laminate is less than 2.0 or equal to 2.0, less than 1.9 or equal to 1.9, less than 1.8 or equal to 1.8, less than 1.75 or equal to 1.75, less than 1.7 or equal to 1.7, or less than 1.6 or equal to 1.6 at 10 GHz, and / or the dissipation factor of the laminate is less than 0.0025 or equal to 0.0025, less than 0.00225 or equal to 0.00225, less than 0.002 or equal to 0.002, less than 0.00175 or equal to 0.00175, or less than 0.0015 or equal to 0.0015 at 10 GHz.

[0012] In some aspects, at least one or more of the electrically insulating layers can comprise fibers that do not comprise the inventive porous material. In other aspects, at least one or more of the electrically insulating layers can comprise a combination of fibers and the inventive porous material (e.g., fibers dispersed or arranged within the porous material). The fibers can be natural fibers, synthetic fibers, semi-synthetic fibers, or combinations thereof. The fibers can include plant fibers, wood fibers, animal fibers, mineral fibers, biofibers, or combinations thereof. In some particular cases, the fibers can include rayon fibers, bamboo fibers, diacetate fibers, triacetate fibers, polyester fibers, polyaramid fibers, or combinations thereof. In some embodiments, the fibers include metal fibers, carbon fibers, carbide fibers, glass fibers, mineral fibers, basalt fibers, or combinations thereof. In some embodiments, the fibers include thermoplastic polymer fibers, thermoset polymer fibers, or combinations thereof. Non-limiting examples of thermoplastic fibers include fibers of polyethylene terephthalate (PET), polycarbonate (PC) family polymers, polybutylene terephthalate (PBT), poly(l,4-cyclohexanedicarboxylic acid-l,4-cyclohexanedimethanol ester) (PCCD), poly(cyclohexyl terephthalate) glycol-modified (PCTG), polyphenylene oxide (PPO), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polymethyl methacrylate (PMMA), polyethyleneimine or polyetherimide (PEI) and derivatives thereof, thermoplastic elastomers (TPE), terephthalic acid (TPA) elastomers, poly(cyclohexanedimethylene terephthalate) (PCT), polyethylene naphthalate (PEN), polyamide (PA), polysulfone sulfonate (PSS), sulfonates of polysulfone, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), acrylonitrile butadiene styrene (ABS), polyphenylene sulfide (PPS), copolymers thereof, or blends thereof. Non-limiting examples of thermoset fibers include fibers of unsaturated polyester resins, polyurethanes, polyoxybenzyl methylene glycol anhydride (e.g., phenol formaldehyde resins), urea-formaldehyde resins, diallyl phthalate, epoxy resins, epoxy vinyl esters, polyimides, cyanate esters of polyureas, dicyclopentadiene, phenolic plastics, benzoxazines, copolymers thereof, or blends thereof. In some embodiments, the fibers are polyaramid, polyimide, polybenzoxazole, polyurethane, or blends thereof. In some embodiments, the fibers are vinylon. In some embodiments, the fibers are polyester fibers. In some embodiments, the fibers are non-woven. In some embodiments, the fibers form a fibrous matrix. In some embodiments, the average filament cross-sectional area of the fibers is 5 pm to 40,000 pm to 40,000 pm 2 to 40,000 pm 2and an average length of 20 mm to 100 mm. In some embodiments, the cross-sectional area is 5 μm 2 , 10 μm 2 , 15 μm 2 , 20 μm 2 , 25 μm 2 , 50 μm 2 , 100 μm 2 , 150 μm 2 , 200 μm 2 , 250 μm 2 , 300 μm 2 , 350 μm 2 , 400 μm 2 , 450 μm 2 , or 500 μm 2 or any two of these values. In some embodiments, the average length of the fibers is about 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1000 mm, 1500 mm, 2000 mm, 3000 mm, 4000 mm, 5000 mm, or any two of these values. Depending on the use of the internally reinforced aerogel, various fiber tows can be used. For example, the fiber tows can be carbon fibers or ceramic fibers, or tows of precursor fibers of carbon or ceramic, glass fibers, polyaramid fibers, or mixtures of different kinds of fibers. The tows can contain any number of fibers. For example, the tows can contain 400, 750, 800, 1375, 1000, 1500, 3000, 6000, 12000, 24000, 50000, or 60000 filaments. The filament diameter of the fibers can be 5 microns to 24 microns, 10 microns to 20 microns, or 12 microns to 15 microns or any range therebetween, or 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns, 21 microns, 22 microns, 23 microns, 24 microns, or any value therebetween. The average filament cross-sectional area of the fibers in the fiber tow can be 7 μm 2 to 800 μm 2This corresponds to an average diameter of the looped fibers of 3 microns to 30 microns. In some embodiments, the fibrous matrix comprises a felt, batt, nonwoven, or mat.

[0013] The conductive layers can have a suitable thickness for propagating electrical signals. In some embodiments, at least one of the conductive layers has a thickness of 0.5 mil to 3 mil, 0.5 mil to 2 mil, or 0.5 mil to 0.9 mil, 1 mil to 2 mil, 1.4 mil, or about 0.7 mil. In some embodiments, at least one of the conductive layers has an areal density of 0.35 ounces per square foot (oz / ft 2 ) to 3 ounces per square foot (oz / ft 2 ) or 0.35 oz / ft 2 to 0.75 oz / ft 2 , for example about 0.5 oz / ft 2 .

[0014] In some embodiments, the laminate comprises one or more adhesive layers, each disposed between adjacent layers of the conductive layers and the electrically insulating layers. The adhesive layers can bond the other layers together and have properties that improve the electrical performance of the laminate and mitigate delamination. To illustrate, in some embodiments, at least one of the adhesive layers comprises a fluoropolymer film, at least one of the adhesive layers comprises a polyimide film, and / or at least one of the adhesive layers comprises a B-staged epoxy resin. In some embodiments, at least one of the adhesive layers has a dielectric constant less than 3.5 or equal to 3.5, less than 3.0 or equal to 3.0, less than 2.5 or equal to 2.5, or less than 2.25 or equal to 2.25 at 10 GHz and / or a dissipation factor less than 0.0040 or equal to 0.0040, less than 0.0035 or equal to 0.0035, less than 0.0030 or equal to 0.0030, less than or equal to 0.0025, less than 0.0025 or equal to 0.0020, or less than 0.0015 or equal to 0.0015 at 10 GHz. In some embodiments, at least one of the adhesive layers has a decomposition temperature greater than 350°C or equal to 350°C, greater than 375°C or equal to 375°C, greater than 400°C or equal to 400°C, greater than 450°C or equal to 450°C, or greater than 500°C or equal to 500°C and / or a glass transition temperature or melting point greater than 100°C or equal to 100°C, greater than 150°C or equal to 150°C, greater than 200°C or equal to 200°C, greater than 225°C or equal to 225°C, greater than 250°C or equal to 250°C, or greater than 275°C or equal to 275°C. In some embodiments, at least one of the adhesive layers has a thickness of 0.3 mil to 5 mil, 0.3 mil to 3.0 mil, 0.3 mil to 2.0 mil, 0.3 mil to 1.2 mil, or 0.75 mil to 1.25 mil.

[0015] The aerogels and laminates can be relatively flexible. For example, in some embodiments, the laminate is provided in a roll such that a portion of the front surface of the laminate faces a portion of the back surface of the laminate. In some such embodiments, the laminate, which is flexible enough to be provided in a roll, can be used in a flexible circuit board. However, in other embodiments, the laminate can have a stiffness high enough that it cannot be rolled up. For example, in some embodiments, the laminate includes one or more reinforcement layers. In some embodiments, each reinforcement layer has a bending stiffness that is at least 10% greater than the bending stiffness of each conductive layer and electrically insulating layer. In some embodiments, for at least one of the electrically insulating layers, at least one of the reinforcement layers is at least partially embedded in the polymeric aerogel layer, optionally such that the Young’s modulus of the electrically insulating layer is at least 200 MPa. In some embodiments, at least one of the reinforcement layers includes one or more unidirectional, non-woven, or woven sheets, each sheet including fibers. In some embodiments, for at least one of the electrically insulating layers, a plurality of fibers are dispersed in the polymeric aerogel layer, optionally such that the Young’s modulus of the electrically insulating layer is at least 200 MPa. In some embodiments, at least one of the reinforcement layers includes one or more sheets of paper. However, in other embodiments, the laminate does not include fibers.

[0016] In some embodiments, for at least one of the opposing front and back surfaces of the laminate, at least a portion, optionally at least a majority, of the surface is defined by one of the conductive layers. In some embodiments, the one or more conductive layers includes two or more conductive layers, where, optionally, at least a portion of the front surface of the laminate is defined by a first of the conductive layers and at least a portion of the back surface of the laminate is defined by a second of the conductive layers. In some embodiments, the electrically insulating layers include two or more, optionally four or more, electrically insulating layers. In some embodiments, no conductive layer is disposed between adjacent electrically insulating layers. In some embodiments, the laminate has a thickness of 5 mils to 100 mils, 5 mils to 75 mils, 5 mils to 50 mils, or 5 mils to 30 mils.

[0017] Some inventive circuit boards include some inventive laminates, and for at least one of the front and back surfaces, a solder mask is bonded to the surface such that the solder mask covers at least a majority of the surface. In some embodiments, the solder mask includes at least 90% by weight of a polymer, and / or has a thickness of less than 3.2 mils or equal to 3.2 mils, less than 1.6 mils or equal to 1.6 mils, or less than 0.8 mils or equal to 0.8 mils. Some inventive devices include some inventive circuit boards, and optionally include an antenna electrically coupled to the circuit board. In some embodiments, the device is an electronic amplifier, a radar system, or a communication system.

[0018] Also disclosed is a method of making a polymeric aerogel layer suitable for use in at least some of the present laminates. The method can comprise: (a) providing a monomer or combination of monomers into a solvent to form a solution; (b) polymerizing the monomers in the solution to form a polymeric gel matrix; and (c) subjecting the polymeric gel matrix to conditions sufficient to remove liquid from the polymeric gel matrix to form an aerogel having a polymeric matrix comprising an open-cell structure. Step (b) can further comprise adding a solidification agent to the solution to reduce the solubility of the polymer formed in the solution and form macro-pores in the gel matrix, the macro-pores formed comprising liquid from the solution. The method can comprise casting the polymeric gel matrix in step (b) onto a support such that the polymeric gel matrix layer is contained on the support, wherein the aerogel in step (c) is in the form of a film.

[0019] The pore structure of the aerogel, including the amount and volume of macro-pores, meso-pores, and micro-pores, can be controlled, primarily by controlling the polymer / solvent kinetics during the formation of the polymeric gel matrix. As one example, a solidification agent can be added to the solution in step (b) to reduce the solubility of the polymer formed in the solution and form macro-pores in the gel matrix, the macro-pores formed comprising liquid from the solution. Such a solidification agent can be, for example, 1,4-diazabicyclo[2.2.2]octane. Adding a solidification agent, such as triethylamine, to the solution in step (b) to increase the solubility of the polymer formed in the solution will result in a relatively lesser number of macro-pores being formed in the gel matrix. In another example, when forming a polyimide aerogel, increasing the ratio of rigid amines (e.g., p-phenylenediamine (p-PDA)) to more flexible diamines (e.g., 4,4’-oxydianiline (4,4’-ODA)) in the polymer backbone can favor the formation of macro-pores over the formation of smaller meso-pores and micro-pores.

[0020] Although more details are provided below regarding monomers, solvents, and processing conditions, generally speaking, the following can be adjusted to control the pore structure of the aerogel: (1) polymerization solvent; (2) polymerization temperature; (3) polymer molecular weight; (4) molecular weight distribution; (5) copolymer composition; (6) amount of branching; (7) amount of crosslinking; (8) method of branching; (9) method of crosslinking; (10) method used to form the gel; (11) type of catalyst used to form the gel; (12) chemical composition of the catalyst used to form the gel; (13) amount of catalyst used to form the gel; (14) temperature at which the gel is formed; (15) type of gas flowed through the material during gel formation; (16) rate at which the gas is flowed through the material during gel formation; (17) atmospheric pressure during gel formation; (18) removal of dissolved gases during gel formation; (19) presence of solid additives in the resin during gel formation; (20) amount of time for the gel formation process; (21) substrate used to form the gel; (22) type of solvent used in each step of the optional solvent exchange process; (23) composition of the solvent used in each step of the optional solvent exchange process; (24) amount of time used in each step of the optional solvent exchange process; (25) residence time of the part in each step of the solvent exchange process; (26) flow rate of the optional solvent exchange solvent; (27) flow type of the optional solvent exchange solvent; (28) agitation rate of the optional solvent exchange solvent; (29) temperature used in each step of the optional solvent exchange process; (30) ratio of the volume of the optional solvent exchange solvent to the volume of the part; (31) method of drying; (32) temperature of each step in the drying process; (33) pressure of each step in the drying process; (34) gas composition used in each step of the drying process; (35) gas flow rate of each step in the drying process; (36) temperature of the gas in each step of the drying process; (37) temperature of the part in each step of the drying process; (38) presence of an enclosure around the part in each step of the drying process; (39) type of enclosure around the part in the drying process; and / or (40) solvent used in each step of the drying process.

[0021] The term "aerogel" refers to a class of materials that are typically prepared by forming a gel, removing the mobile interstitial solvent phase from the pores, and then replacing it with a gas or gas-like material. By controlling the gel and evaporation system, the density, shrinkage, and pore collapse can be minimized. The aerogels of the present invention can comprise macropores, mesopores, and / or micropores. In preferred aspects, a majority (e.g., more than 50%) of the pore volume of the aerogel can be comprised of macropores. In other alternative aspects, a majority of the pore volume of the aerogel can be comprised of mesopores and / or micropores, such that less than 50% of the pore volume of the aerogel is comprised of macropores. In some embodiments, the aerogels of the present invention can have a low bulk density (about 0.75 g / cm33 or less than 0.75 g / cm 3 , preferably about 0.01 g / cm 3 to about 0.5 g / cm 3 ), high surface area (typically about 10 m 2 / g to 1000 m 2 / g and more than 1000 m 2 / g, preferably about 50 m 2 / g to about 1000 m 2 / g), high porosity (about 20% and greater than 20%, preferably greater than about 85%), and / or relatively large pore volume (greater than about 0.3 mL / g, preferably about 1.2 mL / g and higher than 1.2 mL / g).

[0022] The presence of macropores, mesopores, and / or micropores in the aerogels of the present invention can be determined by mercury intrusion porosimetry (MIP) and / or gas physisorption experiments. MIP testing can be used to measure mesopores and macropores (i.e., ASTM D4404-10, Standard Test Methods for Determining Pore Volume and Porosity of Soils and

[0023] The “decomposition temperature” of a material is the temperature at which 2%, 5%, or 10% of a sample of the material will decompose when heated in an environment raised to that temperature. The decomposition temperature can be measured by placing a sample in a thermogravimetric analyzer (TGA), heating the sample in the TGA from ambient temperature (e.g., at a rate of 10 °C / minute), and recording the temperature at which the sample is 2%, 5%, or 10% less in mass than its initial mass as its decomposition temperature.

[0024] The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically. The two items being “coupled” can be integral with each other or can be attached to, or be part of, one or more intermediate components or elements.

[0025] The use of the ordinal “first,” “second,” “third,” etc. to describe a common but distinct item, unless otherwise clear by context, is used only for purposes of brevity and does not constitute a requirement or preference for such items. The use of ordinal terms, unless otherwise clear by context, is not intended to imply a particular order of occurrence or precedence.

[0026] The term “substantially” is defined to include a majority of as understood by one of ordinary skill in the art, and, further, encompasses the stated specification, (and includes the stated specification; e.g., substantially 90 degrees includes 90 degrees, substantially parallel includes parallel). In any of the disclosed embodiments, the terms “substantially,” “about,” and “approximately” can be replaced with “within X%” where X is 0.1%, 1%, 5%, or 10%.

[0027] The phrase "and / or" means "and" or "or". For example, A, B, and / or C includes: A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C. In other words, "and / or" serves as a disjunctive word.

[0028] The terms "comprise," "have," "include," and "contain" are open-ended connecting verbs. As such, an apparatus that "comprises," "has," "includes," or "contains" one or more elements possesses those one or more elements, but is not limited to possessing only those one or more elements. Likewise, a method that "comprises," "has," "includes," or "contains" one or more steps possesses those one or more steps, but is not limited to possessing only those one or more steps.

[0029] Any embodiment of any of the devices and methods can be used in combination with any other, and vice versa, except where this is explicitly prohibited or inherently impossible. Any embodiment of any of the devices and methods can consist of or consist essentially of any of the described elements, features, and / or steps, unless otherwise specified. Accordingly, in any claim that follows any of the phrases "comprises the steps of," "comprises the elements of," "consists of," or "consists essentially of," the steps or elements of that claim are not exhaustive, unless otherwise specified.

[0030] One or more features of an embodiment can be applied to other embodiments even if such a feature is not described or exemplified in combination with that other embodiment unless the nature of the disclosure or the embodiment explicitly prohibits such a combination.

[0031] Some details are described below in relation to the above-described embodiments and other embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0032] The following drawings are included to illustrate the following embodiments, by way of non-limiting example. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which the structure appears. Identical reference numerals do not necessarily refer to the same structure or component throughout the description. Rather, like reference numerals can be used to indicate similar features or features with similar functionality, and different reference numerals can also be used to indicate similar features or features with similar functionality.

[0033] Figure 1A is a top view of a first embodiment of the inventive laminate comprising a polymeric aerogel layer disposed between two copper-containing layers.

[0034] Figure 1B is a cross-sectional view of the laminate of Figure 1A is a cross-sectional view of the laminate of

[0035] Figure 2A is a cross-sectional view of a second embodiment of the inventive laminate comprising two polymeric aerogel layers disposed between two copper-containing layers.

[0036] Figure 2B is a cross-sectional view of a third embodiment of the inventive laminate comprising four polymeric aerogel layers disposed between two copper-containing layers.

[0037] Figure 3A is a cross-sectional view of a fourth embodiment of the inventive laminate comprising a reinforcing layer embedded in a polymeric aerogel layer.

[0038] Figure 3B is a cross-sectional view of a fifth embodiment of the inventive laminate comprising a polymeric aerogel and copper-containing layers, in addition to a non-embedded reinforcing layer.

[0039] Figure 4 is a perspective view of a roll of the laminate of Figure 1A

[0040] Figure 5A is a top view of one of the inventive circuit boards comprising the laminate of Figure 1A Figure 5A the top copper-containing layer of the laminate is etched to define individual conductive paths.

[0041] Figure 5B is a top view of the circuit board of Figure 5A

[0042] Figure 5C is a cross-sectional view of the circuit board of Figure 5B Figure 5A

[0043] Figure 6 is a schematic view of one of the inventive devices comprising the circuit board of Figure 5A

[0044] Figure 7 is the pore size diameter distribution of a first non-limiting aerogel of the invention.

[0045] Figure 8 is the pore size diameter distribution of a second non-limiting aerogel of the invention.

[0046] Figure 9 is the pore size diameter distribution of a third non-limiting aerogel of the invention. DETAILED DESCRIPTION

[0047] A. Copper-clad laminate, circuit board and devices comprising the same

[0048] Reference is made to Figure 1A and Figure 1B ​​​​​​Figure 1 1 shows a first embodiment 10a of a laminate of the present disclosure. The laminate 10a can include one or more than one electrically conductive layer 14 and one or more than one electrically insulating layer 18, for example, greater than or equal to any of, or between any two of, 1, 2, 3, 4, 5, or 6 electrically conductive layers, and greater than or equal to any of, or between any two of, 1, 2, 3, 4, 5, or 6 electrically insulating layers. As shown, the laminate 10a includes two electrically conductive layers 14 and a single electrically insulating layer 18 disposed therebetween. However, in other embodiments, the laminate (e.g., 10b or 10c) can include multiple electrically insulating layers 18, for example, two ( Figure 2A ) or four ( Figure 2B ) electrically insulating layers.

[0049] For at least one (e.g., each) of the opposing front and back surfaces 22a, 22b of the laminate (e.g., 10a-10c), at least a portion (e.g., at least a majority, up to and including all) of the surface (e.g., planar area of the surface) can be defined by one of the electrically conductive layers 14; as shown, substantially all of the front and back surfaces are defined by the first and second electrically conductive layers, respectively, with all of the electrically insulating layers 18 disposed between the first and second electrically conductive layers. In this manner, one or more of the electrically conductive layers 14 can be exposed, such that circuitry can be fabricated therefrom (e.g., by etching, as described below), with the electrically insulating layers 18 supporting and insulating the electrically conductive layers. To further facilitate such circuitry fabrication, in some embodiments, in which there are multiple electrically insulating layers 18, no electrically conductive layer 14 is disposed between adjacent electrically insulating layers.

[0050] Each electrically conductive layer 14 can include copper, which can facilitate electrical conductivity. For example, each electrically conductive layer 14 can include copper in an amount greater than or equal to, or between any two of, 90 wt.%, 91 wt.%, 92 wt.%, 93 wt.%, 94 wt.%, 95 wt.%, 96 wt.%, 97 wt.%, 98 wt.%, or 99 wt.%. The thickness 30 of each electrically conductive layer 14 can improve manufacturability and suitable electrical properties. For example, the thickness 30 of at least one (e.g., each) of the electrically conductive layers 14 can be less than or equal to, or between any two of, 4.5 mils, 4.0 mils, 3.5 mils, 3.0 mils, 2.5 mils, 2.0 mils, 1.5 mils, 1.0 mils, 0.9 mils, 0.8 mils, 0.7 mils, 0.6 mils, or 0.5 mils (e.g., 0.5 mils to 3.0 mils, e.g., 0.5 mils to 2 mils, e.g., 0.5 mils to 0.9 mils, approximately 1.4 mils, or approximately 0.7 mils). The areal density of each electrically conductive layer 14 can be less than or equal to, or between any two of, 3.0 ounces per square foot (oz / ft 22.5 oz / ft 2 2.0 oz / ft 2 1.5 oz / ft 2 1.0 oz / ft 2 0.75 oz / ft 2 0.50 oz / ft 2 or 0.25 oz / ft 2 (e.g., 0.35 oz / ft 2 to 3.0 oz / ft 2 , e.g., 0.35 oz / ft 2 to 0.75 oz / ft 2 or about 0.5 oz / ft 2 ). Conductive layers 14 having a relatively higher thickness (e.g., greater than 1.5 mils or equal to 1.5 mils and / or a areal density of greater than 1.1 oz / ft 2 or equal to 1.1 oz / ft 2 may be used to accommodate greater electrical loads.

[0051] In some aspects, each electrically insulating layer 18 can comprise a porous material. In certain aspects, the porous material can be an open-cell porous material. In certain other aspects, the porous material can be a closed-cell porous material. In certain aspects, the porous material can be a foam. In certain aspects, the foam can be an organic foam or a polysiloxane foam. Non-limiting examples of organic foams can include polyurethane, polystyrene, polyvinyl chloride, (meth)acrylic polymers, polyamides, polyimides, polyaramids, polyureas, polyesters, polyolefins (e.g., polyethylene, polypropylene, ethylene propylene diene monomer (EPDM) foams, etc.), polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, polyvinyl acetate, ethylene vinyl alcohol (EVOH), ethylene-vinyl acetate (EVA), polymethyl methacrylate, polyacrylate, polycarbonate, polysulfonate, or synthetic rubber foams, or any combination thereof. In certain aspects, the foam can be a polyurethane foam. In certain aspects, the porous material can be an aerogel. In some aspects, each electrically insulating layer 18 can comprise a polymeric aerogel layer. To facilitate the desired dielectric properties (e.g., low dielectric constant and low dissipation factor), each aerogel layer 18 can be relatively thin. For example, the thickness 34 of at least one (e.g., each) of the aerogel layers 18 can be less than or equal to, or between any two of, 20 mils, 19 mils, 18 mils, 17 mils, 16 mils, 15 mils, 14 mils, 13 mils, 12 mils, 11 mils, 10 mils, 9.0 mils, 8.0 mils, 7.0 mils, 6.0 mils, 5.0 mils, 4.0 mils, or 3.0 mils, preferably less than 12 mils or equal to 12 mils (e.g., about 10 mils) or less than 7.0 mils or equal to 7.0 mils (e.g., about 5.0 mils). In some embodiments, each electrically insulating layer 18 has i) a dielectric constant at 10 GHz of any one of, at most any one of, or between any two of, 3, 2.75, 2.5, 2.25, 2, 1.75, 1.6, 1.4, 1.3, 1.2, and 1.1; and / or a dissipation factor at 10 GHz of any one of, at most any one of, or between any two of, 0.005, 0.004, 0.003, 0.0025, 0.00225, 0.002, 0.00175, 0.0015, 0.00125, 0.001, 0.00075, and 0.0005.

[0052] Each polymeric aerogel layer 18 can have micropores, mesopores, and / or macropores. Each aerogel layer 18 can have a pore volume greater than or equal to, or between any two of, 10%, 25%, 50%, 75%, or 95%, and can be composed of micropores, mesopores, and / or macropores (e.g., micropores, mesopores, micropores and mesopores, or macropores). Each aerogel layer 18 can have an average pore volume greater than or equal to, or between any two of, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 800 nm, 1000 nm, 2000 nm, 3000 nm, 4000 nm, or 5000 nm.

[0053] Each of the aerogel layers 18 can also be heat resistant, such that the laminate can withstand heating during the circuit board manufacturing process (e.g., during soldering) and during use of the laminate (e.g., from heat generated by current flowing through the laminate). For example, at least one (e.g., each) of the aerogel layers 18 can have a decomposition temperature greater than or equal to, or between any two of, 400 °C, 425 °C, 450 °C, 475 °C, 500 °C, 525 °C, 550 °C, 575 °C, or 600 °C (e.g., greater than or equal to 450 °C). Materials and processes for manufacturing the polymeric aerogel layers are explained in Sections B and C below.

[0054] In some aspects, each electrical insulating layer 18 may comprise fibers that do not contain the porous material of the present invention. In other aspects, each electrical insulating layer 18 may comprise a combination of fibers and the porous material of the present invention (e.g., fibers dispersed or arranged within the porous material). The fibers may be natural fibers, synthetic fibers, semi-synthetic fibers, or combinations thereof. Fibers may include plant fibers, wood fibers, animal fibers, mineral fibers, biological fibers, or combinations thereof. In some specific cases, the fibers may include man-made fibers, bamboo fibers, diacetic acid fibers, triacetic acid fibers, polyester fibers, polyaramid fibers, or combinations thereof. In some embodiments, the fibers include metal fibers, carbon fibers, carbide fibers, glass fibers, mineral fibers, basalt fibers, or combinations thereof. In some embodiments, the fibers include thermoplastic polymer fibers, thermosetting polymer fibers, or combinations thereof. Non-limiting examples of thermoplastic fibers include polyethylene terephthalate (PET), polycarbonate (PC) family polymers, polybutanol terephthalate (PBT), poly(1,4-cyclohexanedicarboxylate-1,4-cyclohexanediol) (PCCD), glycol-modified polycyclohexyl terephthalate (PCTG), polyphenylene ether (PPO), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), and polymethyl methacrylate (PMMA). Fibers of polyethyleneimine or polyetherimide (PEI) and their derivatives, thermoplastic elastomers (TPE), terephthalic acid (TPA) elastomers, poly(cyclohexanedimethyl terephthalate) (PCT), polyethylene naphthalate (PEN), polyamide (PA), polysulfone sulfonate (PSS), polysulfone sulfonates, polyetheretherketone (PEEK), polyetherketoneketone (PEKK), acrylonitrile butadiene styrene (ABS), polyphenylene sulfide (PPS), copolymers thereof, or blends thereof. Non-limiting examples of thermosetting fibers include unsaturated polyester resins, polyurethanes, polyoxybenzylmethylenglycolanhydride (e.g., phenolic resins), urea-formaldehyde resins, diallyl phthalate, epoxy resins, epoxy vinyl esters, polyimides, cyanate esters of polycyanurate, dicyclopentadiene, phenolic plastics, benzo[a] Fibers of aziridines, their copolymers, or blends thereof. In some embodiments, the fibers are polyaramids, polyimides, polybenzo[a]pyrene, etc. The fiber is azole, polyurethane, or a blend thereof. In some embodiments, the fiber is vinylon. In some embodiments, the fiber is polyester. In some embodiments, the fiber is nonwoven. In some embodiments, the fiber forms a fiber matrix. In some embodiments, the average filament cross-sectional area of ​​the fiber is 5 μm. 2 Up to 40000μm 2 The average length ranges from 20 mm to 100 mm. In some embodiments, the cross-sectional area is 5 μm.2 , 10 pm 2 , 15 pm 2 , 20 pm 2 , 25 pm 2 , 50 pm 2 , 100 pm 2 , 150 pm 2 , 200 pm 2 , 250 pm 2 , 300 pm 2 , 350 pm 2 , 400 pm 2 , 450 pm 2 , or 500 pm 2 or between any two of these values. In some embodiments, the average length of the fibers is about 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1000 mm, 1500 mm, 2000 mm, 3000 mm, 4000 mm, 5000 mm, or between any two of these values. Depending on the use of the internally reinforced aerogel, various fiber tows can be used. For example, the fiber tows can be carbon fibers or ceramic fibers, or tows of precursor fibers of carbon or ceramic, glass fibers, polyaramid fibers, or mixtures of different kinds of fibers. The tows can contain any number of fibers. For example, the tows can contain 400, 750, 800, 1375, 1000, 1500, 3000, 6000, 12000, 24000, 50000, or 60000 filaments. The filament diameter of the fibers can be 5 microns to 24 microns, 10 microns to 20 microns, or 12 microns to 15 microns, or any range therein, or 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns, 21 microns, 22 microns, 23 microns, 24 microns, or any value therein. The average filament cross-sectional area of the fibers in the fiber tow can be 7 pm 2 to 800 pm 2 , which is equivalent to an average diameter of 3 microns to 30 microns of the ring-shaped fibers. In some embodiments, the fiber matrix comprises a felt, batt, nonwoven, or mat.

[0055] The laminate also includes one or more adhesive layers 26, for example, greater than or equal to any of, or between any two of, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, to bond other layers of the laminate together. Each adhesive layer 26 can be disposed between adjacent layers of the other laminate (e.g., the conductive layer 14 and the electrically insulating layer 18). Bonding can be achieved by stacking the layers (e.g., 14, 18, 26) and applying heat and / or pressure (e.g., with a press) to the stack, optionally such that the temperature thereof exceeds the glass transition temperature of the adhesive layer 26.

[0056] The adhesive layers 26 can have components that reduce the risk of delamination, for example, by being heat resistant. For example, at least one (e.g., each) of the adhesive layers 26 can have a decomposition temperature greater than or equal to any of, or between any two of, 350 °C, 375 °C, 400 °C, 425 °C, 450 °C, or 500 °C. Further, at least one (e.g., each) of the adhesive layers 26 can have a glass transition temperature or melting point greater than or equal to any of, or between any two of, 100 °C, 150 °C, 175 °C, 200 °C, 225 °C, 250 °C, or 275 °C. The adhesive layers 26 can also facilitate low dielectric constant and dissipation factor of the laminate. For example, at least one (e.g., each) of the adhesive layers 26 can have a dielectric constant less than or equal to any of, or between any two of, 3.5, 3.25, 3.0, 2.75, 2.5, or 2.25 (e.g., less than 3.0 or equal to 3.0), and / or a dissipation factor less than or equal to any of, or between any two of, 0.0040, 0.0035, 0.0030, 0.0025, 0.0020, or 0.0015 (e.g., less than 0.00375 or equal to 0.00375), measured at 10 GHz. Exemplary adhesives suitable for the adhesive layers 26 include fluoropolymer films, polyimide films, and B-staged epoxy resins. The adhesives for the adhesive layers 26 can be commercially available adhesives, such as DuPont TM FEP films, HT and GPL, TSU510S-A by Toyochem Co., Ltd. (Tokyo, Japan), Teflon FEP by DuPont TM The thickness 38 of at least one (e.g., each) of the adhesive layers 26 can be less than or equal to any of, or between any two of, 5.0 mils, 4.0 mils, 3.0 mils, 2.0 mils, 1.25 mils, 1.0 mils, 0.75 mils, 0.60 mils, 0.50 mils, 0.40 mils, or 0.30 mils (e.g., 0.3 mils to 0.7 mils, such as approximately 0.5 mils), which can facilitate adhesion while improving desired dielectric properties.

[0057] The laminate can have a total thickness 42 (e.g., measured between the front surface 22a and the back surface 22b) suitable for a circuit board, and be relatively thin (e.g., to facilitate low dielectric constant and dissipation factor). For example, the thickness 42 can be less than or equal to, or between any two of, 100 mils, 75 mils, 50 mils, 40 mils, 30 mils, or 20 mils (e.g., 5 mils to 30 mils).

[0058] The laminate can have dielectric properties suitable for high frequency applications (e.g., signal frequencies of 10 GHz to 300 GHz). For example, the laminate can have an ultra-low dielectric constant, such as less than or equal to, or between any two of, 2.0, 1.9, 1.8, 1.7, or 1.6 (e.g., less than 1.75 or equal to 1.75) at 10 GHz, such that electrical signals can propagate through the laminate at a relatively high rate. In addition, the laminate can have a low dissipation factor to mitigate dielectric losses, such as less than or equal to, or between any two of, 0.0025, 0.00225, 0.002, 0.00175, or 0.0015 (e.g., less than 0.002 or equal to 0.002) at 10 GHz.

[0059] In some embodiments, the laminate can include a reinforcement to increase strength and / or stiffness (e.g., for rigid circuit board applications), such as a plurality of fibers. For example, referring to Figure 3A and Figure 3B , laminates 10d and 10e are shown that are substantially the same as the laminate 10a, except that each includes one or more reinforcement layers 46, such as greater than or equal to, or between any two of, 1, 2, 3, 4, 5, 6, 7, or 8. At least one (e.g., each) of the reinforcement layers 46 can include one or more plies. At least one (e.g., each) of the plies can be a unidirectional, woven, and / or nonwoven ply that includes fibers optionally dispersed in a thermoplastic resin or a thermoset resin (e.g., a resin that is structurally or compositionally different from the resin of the aerogel layer 18). The plies of the reinforcement layers 46 can also be substantially free of fibers (e.g., a polymeric film, such as a fluoropolymer film). When including a plurality of plies, the reinforcement layers 46 can be a consolidated laminate. Additionally or alternatively, at least one (e.g., each) of the reinforcement layers 46 can include a paper ply that optionally includes cellulose fibers, vinylon fibers, polyester fibers, polyolefin fibers, and / or polypropylene fibers. Suitable papers for the reinforcement layers 46 are commercially available from Hirose Paper Mfg. Co. (Kochi, Japan) or Hirose Paper North America (Macon, GA, USA).

[0060] As shown in the figure, for at least one of the aerogel layers 18, at least one of the reinforcing layers 46 is embedded in the aerogel layer. Figure 3A Although a single reinforcing layer 46 is embedded in the aerogel layer 18 as shown, in other embodiments, multiple reinforcing layers (e.g., greater than or equal to any one of the following, or between any two of the following: 2, 3, 4, 5, or 6) may be embedded in the aerogel layer. Additionally or alternatively, one or more reinforcing layers 46 need not be embedded in one of the aerogel layers 18 and may be bonded to other laminated layers by one or more adhesive layers 26 (e.g., may be disposed between adjacent adhesive layers). As described in section C, the reinforcing or support layer 46 may be embedded in or attached to the aerogel layer 18.

[0061] Furthermore, although laminates 10d and 10e are reinforced with reinforcing layer 46 as shown in the figure, in some embodiments, at least one (e.g., each) of the aerogel layers 18 may contain reinforcing fibers (e.g., chopped or discontinuous fibers not arranged in sheets) dispersed throughout the aerogel layer, optionally such that the volume of the fibers is greater than or equal to, or between, the volume of the aerogel layer as described below: 0.1%, 10%, 20%, 30%, 40%, or 50%. However, in some embodiments, the laminate does not contain fibers (e.g., to improve flexibility).

[0062] Suitable fibers include glass fibers, carbon fibers, polyaramid fibers, thermoplastic fibers, thermosetting fibers, ceramic fibers, basalt fibers, asbestos fibers, steel fibers, cellulose fibers, and / or the like. The average filament cross-sectional area of ​​the fibers used as reinforcement can be greater than or equal to any one of the following, or between any two of the following: 7 μm 2 15μm 2 30μm 2 60μm 2 100μm 2 200μm 2 300μm 2 400μm 2 500μm 2 600μm 2 700μm 2 or 800μm 2 For example, for fibers with a circular cross-section, the average fiber diameter can be greater than or equal to any of the following, or between any two of the following: 3μm, 4μm, 5μm, 6μm, 7μm, 8μm. 2 9μm 2 10μm 2, 11 pm, 12 pm, 13 pm, 14 pm, 15 pm, 16 pm, 17 pm, 18 pm, 19 pm, 20 pm, 21 pm, 22 pm, 23 pm, 24 pm, 25 pm, 26 pm, 27 pm, 28 pm, 29 pm, or 30 pm (e.g., 5 pm to 24 pm, e.g., 10 pm to 20 pm, or 12 pm to 15 pm).

[0063] Non-limiting examples of materials that can be used as the fiber dispersed in the reinforcing layer 46 and / or thermoplastic polymers used to polymerize the reinforcing fibers include polyethylene terephthalate (PET), polycarbonate (PC), polybutylene terephthalate (PBT), poly(l,4-cyclohexane dicarboxylic acid- 1,4-cyclohexane dimethanol ester) (PCCD), poly(cyclohexylene terephthalate glycol) (PCTG), polyphenylene oxide (PPO), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polymethyl methacrylate (PMMA), polyethyleneimine or polyetherimide (PEI) and derivatives thereof, thermoplastic elastomer (TPE), terephthalic acid (TPA) elastomer, poly(cyclohexane dimethylene terephthalate) (PCT), polyethylene naphthalate (PEN), polyamide (PA), polysulfone sulfonate (PSS), sulfonate of polysulfone, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), acrylonitrile butadiene styrene (ABS), polyphenylene sulfide (PPS), copolymers thereof, polyesters or derivatives thereof, polyamides or derivatives thereof (e.g., nylon), or blends thereof.

[0064] Non-limiting examples of materials that can be used as the fiber dispersed in the reinforcing layer 46 and / or thermoplastic polymers used to polymerize the reinforcing fibers include unsaturated polyester resins, polyurethanes, polyoxybenzylmethylglycolic anhydride (e.g., phenol formaldehyde resins), urea-formaldehyde resins, diallyl phthalate, epoxy resins, epoxy vinyl esters, polyimides, cyanate esters of polycyanuric acid ester, dicyclopentadiene, phenolic plastics, benzoxazine, copolymers thereof, or blends thereof. Non-limiting examples of materials that can be used as the fiber dispersed in the reinforcing layer 46 and / or thermoplastic polymers used to polymerize the reinforcing fibers include unsaturated polyester resins, polyurethanes, polyoxybenzylmethylglycolic anhydride (e.g., phenol formaldehyde resins), urea-formaldehyde resins, diallyl phthalate, epoxy resins, epoxy vinyl esters, polyimides, cyanate esters of polycyanuric acid ester, dicyclopentadiene, phenolic plastics, benzoxazine, copolymers thereof, or blends thereof.

[0065] Such reinforcements can increase the strength and stiffness of the laminate. For example, each electrically insulating layer 18 in which the aerogel layer is reinforced (e.g., has one or more embedded sheets and / or fibrous reinforcements dispersed throughout the aerogel) can have a tensile strength greater than or equal to, or between any two of, 5 MPa, 10 MPa, 15 MPa, 20 MPa, or 25 MPa, and / or a Young’s modulus greater than or equal to, or between any two of, 200 MPa, 225 MPa, 250 MPa, 275 MPa, 300 MPa, 325 MPa, or 350 MPa. Each reinforced layer 46 can also be stiffer than other laminate layers; for example, the bending stiffness of each reinforced layer can be greater than or equal to, or between any two of, 10%, 20%, 30%, or 40% of the bending stiffness of each of the electrically conductive layer 14 and the electrically insulating layer 18.

[0066] Further descriptions of suitable reinforcements for the aerogel layer 18 are described in U.S. Patent No. 10,500,557 to Sakaguchi et al., the entirety of which is incorporated by reference herein.

[0067] The laminate (e.g., 10a-10e) can be rigid or flexible. For example, with reference to Figure 4 , the laminate (whether or not reinforced as described above) can be disposed in a roll 48 having an inner diameter 50 less than or equal to, or between any two of, 10 cm, 8 cm, 5 cm, 4 cm, 2 cm, or 1 cm, without suffering permanent deformation. Such flexibility - even if not to the level of this example - can be provided by the materials of the electrically conductive layer, the aerogel layer, and other layers (if present) of the laminate and / or the relatively small thicknesses of these layers (e.g., those discussed above). When in the roll 48, a portion of the front surface 22a of the laminate can face a portion of the back surface 22b of the laminate. The laminate can have a protective film 52 (e.g., to protect the one or more electrically conductive layers 14) removably disposed on at least one of the front surface 22a and the back surface 22b of the laminate. The protective film 52 can be removed from the laminate by, for example, peeling it from the laminate. Such a protective film does not constitute a part of the laminate.

[0068] Such flexible laminates can be suitable for flexible circuit boards. In other embodiments, however, the laminate can have a higher stiffness (e.g., such that it cannot be disposed in such a roll without suffering permanent deformation and / or breaking), which can be provided by the reinforcements described above. Such laminates can be suitable for rigid circuit boards.

[0069] Some laminates of the present invention (e.g., 10a-10e) can be incorporated into a circuit board. For example, with reference toFigure 5A to Figure 5C As shown, at least one (e.g., each) of the electrically conductive layers 14 defining at least a portion of one of the front surface 22a and the back surface 22b can be etched such that the electrically conductive layer defines one or more conductive lines 56. The etching can remove material from the electrically conductive layer 14; as a result, the etched layer can define a surface area of the front surface 22a and / or the back surface 22b that is less than (e.g., less than or equal to any of, or between any two of: 90%, 80%, 70%, 60%, 50%, or 40%) the surface area defined by each of the polymeric aerogel layer 18 and / or the adhesive layer 26 (e.g., where such surface area is measured as a planar area).

[0070] The circuit board 54 can include one or more soldermask layers 58, each bonded to a respective one of the front surface 22a and the back surface 22b such that the soldermask layer covers at least a majority of the surface Figure 5B and Figure 5C ). Each soldermask layer 58 can protect the outermost electrically conductive layer 14 (e.g., from corrosion, damage, and / or shorting). For example, each soldermask layer 58 can include a polymer (e.g., those of any of the foregoing), optionally such that the soldermask layer includes greater than or equal to any of, or between any two of: 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% polymer. To facilitate such protection while maintaining suitable manufacturability and / or electrical properties, a thickness 62 of each soldermask layer 58 is less than or equal to any of, or between any two of: 3.2 mils, 3.0 mils, 2.8 mils, 2.6 mils, 2.4 mils, 2.2 mils, 2.0 mils, 1.8 mils, 1.6 mils, 1.4 mils, 1.2 mils, 1.0 mil, or 0.8 mils (e.g., 0.8 mils to 3.2 mils). Each soldermask layer 58 can cover less than all of the surface (e.g., 22a or 22b) to which the soldermask layer is bonded, such that at least a portion of the electrically conductive layer 14 is exposed (e.g., such that a component can be electrically connected thereto) Figure 5B ).

[0071] Some circuit boards (e.g., 54) of the present disclosure can be incorporated into devices (e.g., 66) for high frequency (e.g., 10 GHz to 300 GHz) applications. For example, referring to Figure 6 As shown, the device 66 is a communication system (e.g., for satellites, high-speed routers and servers, spacecraft, cell phones, cell towers, etc.). The device 66 can also be another device for high frequency applications, such as an electronic amplifier and / or a radar system.

[0072] B. Materials of the polymeric aerogel layer

[0073] The polymeric aerogel layer can include organic materials, inorganic materials, or mixtures thereof. Organic aerogels can be made from polyacrylate, polystyrene, polyacrylonitrile, polyurethane, polyurea, polyimide, polyamide, polyaramid, polyfurfural alcohol, phenol furfural alcohol, melamine formaldehyde, resorcinol formaldehyde, cresol formaldehyde, phenol formaldehyde, polyvinyl alcohol dialdehyde, polycyanurate, polyacrylamide, various epoxy resins, agar, agarose, and the like. In particular embodiments, the aerogel is a polyimide aerogel.

[0074] Polyimides are polymers that have many desirable properties. Polyimide polymers contain nitrogen atoms in the polymer backbone, where the nitrogen atom is attached to two carbonyl carbons, such that the nitrogen atom is stabilized to some extent by the adjacent carbonyl groups. A carbonyl group contains a carbon double-bonded to an oxygen atom, known as a carbonyl carbon. Polyimides are generally considered to be AA-BB type polymers, as two different types of monomers are generally used to make polyimide polymers. Polyimides can also be made from AB type monomers. For example, amino dicarboxylic acid monomers can be polymerized to form AB type polyimides. If desired, mono amines and / or mono anhydrides can be used as endcapping agents.

[0075] One class of polyimide monomers is generally diamine or diamine monomers. Diamine monomers can also be diisocyanates, with the understanding that isocyanate can be appropriately substituted for amine in this specification. Other types of monomers can be used in place of diamine monomers, as known to those skilled in the art. Other types of monomers are referred to as acid monomers, and are generally found in the form of dianhydrides. In this specification, the term "diacid monomer" is defined to include dianhydrides, tetraesters, diester acids, tetracarboxylic acids, or trimethylsilyl esters, all of which can react with diamines to form polyimide polymers. Dianhydrides are understood to be tetraesters, diester acids, tetracarboxylic acids, or trimethylsilyl esters, which can be appropriately substituted. Other types of monomers can also be used in place of diacid monomers, as known to those skilled in the art.

[0076] Because one diacid monomer has two anhydride groups, and different diamine monomers can react with each anhydride group, diacid monomers can be located between two different diamine monomers. Diamine monomers contain two amine functional groups; thus, after the first amine functional group is attached to one diacid monomer, the second amine functional group can still be attached to another diacid monomer, which can then be attached to another diamine monomer, and so on. In this way, a polymer backbone is formed. The resulting condensation reaction forms a polyamic acid.

[0077] Polyimide polymers are generally formed from two different types of monomers, and different kinds of each type of monomer can be mixed. Thus, one, two, or more diacid monomers, and one, two, or more diamine monomers can be included in the reaction vessel. If long polymer chains are desired, the total moles of diacid monomers are kept approximately the same as the total moles of diamine monomers. Because more than one type of diamine or diacid can be used, the various monomer components of each polymer chain can be varied to make polyimides with different properties. For example, a single diamine monomer AA can be reacted with two diacid co-monomers B1B1 and B2B2 to form a polymer chain of the general formula (AA-B1B1) x -(AA-B2B2) y where x and y are determined by the relative amounts of B1B1 and B2B2 incorporated into the polymer backbone. Alternatively, diamine co-monomers A1A1 and A2A2 can be reacted with a single diacid monomer BB to form a polymer chain of the general formula (A1A1-BB) x -(A2A2-BB) y In addition, two diamine co-monomers A1A1 and A2A2 can be reacted with two diacid co-monomers B1B1 and B2B2 to form a polymer chain of the general formula (A1A1-B1B1) w -(A1A1-B2B2) x -(A2A2-B1B1) y -(A2A2-B2B2) z where w, x, y, and z are determined by the relative amounts of A1A1-B1B1, A1A1-B2B2, A2A2-B1B1, and A2A2-B2B2 incorporated into the polymer backbone. More than two diacid co-monomers and / or more than two diamine co-monomers can also be used. Thus, one or more than one diamine monomer can be polymerized with one or more than one diacid, and the general formula of the polymer is determined by varying the amounts and types of monomers used.

[0078] There are many examples of monomers that can be used to make polymeric aerogels containing polyamidamide polymers. In some embodiments, the diamine monomer is a substituted or unsubstituted aromatic diamine, a substituted or unsubstituted alkyl diamine, or a diamine that can contain both aromatic and alkyl functional groups. A non-limiting list of possible diamine monomers includes 4,4’-diaminodiphenylamine (ODA), 3,4’-diaminodiphenylamine, 3,3’-diaminodiphenylamine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, diaminobenzanilide, 3,5-diaminobenzoic acid, 3,3’-diaminodiphenyl sulfone, 4,4’-diaminodiphenyl sulfone, 1,3-bis-(4-aminophenoxy)benzene, 1,3-bis-(3-aminophenoxy)benzene, 1,4-bis-(4-aminophenoxy)benzene, 1,4-bis-(3-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]-hexafluoropropane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 4,4’-isopropylidene dianiline, 1-(4-aminophenoxy)-3-(3-aminophenoxy)benzene, 1-(4-aminophenoxy)-4-(3-aminophenoxy)benzene, bis-[4-(4-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]sulfone, bis(4-[4-aminophenoxy]phenyl)ether, 2,2’-bis-(4-aminophenyl)-hexafluoropropane (6F-diamine), 2,2’-bis-(4-aminophenoxy)isopropylidene, m-phenylenediamine, p-phenylenediamine, 1,2-diaminobenzene, 4,4’-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 4,4’-diaminodiphenylpropane, 4,4’-diaminodiphenyl sulfide, 4,4’-diaminodiphenyl sulfone, 3,4’-diaminodiphenyl ether, 4,4’-diaminodiphenyl ether, 2,6-diaminopyridine, bis(3-aminophenyl)diethylsilane, 4,4’-diaminodiphenyl diethylsilane, benzidine, dichlorobenzidine, 3,3’-dimethoxybenzidine, 4,4’-diaminobenzophenone, N,N-bis(4-aminophenyl)-n-butylamine, N,N-bis(4-aminophenyl)methylamine, 1,5-diaminonaphthalene, 3,3’-dimethyl-4,4’-diaminobiphenyl, 4-aminophenyl-3-aminobenzoate, N,N-bis(4-aminophenyl)aniline, bis(p-β-amino-t-butylphenyl)ether, p-bis-2-(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,3-bis(4-aminophenoxy)benzene, m-xylylenediamine, p-xylylenediamine, 4,4’-diaminodiphenyl ether phosphine oxide, 4,4’-diaminodiphenyl N-methylamine, 4,4’-diaminodiphenyl N-phenylamine, amino-terminated polydimethylsiloxane, amino-terminated polypropylene oxide, amino-terminated polybutylene oxide, 4,4’-methylenebis(2-methylcyclohexylamine), 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7- diaminioeane, 1,8-diaminooctane, 1,9-diaminononane, 1,10- diaminodecane, and 4,4'-methylenebisbenzeneamine, 2,2'-dimethyl- benzidine (also known as 4,4'-diamino-2,2'-dimethylbiphenyl (DMB)), bisbenzene-p-xylylenediamine, 4,4'-bis(4-aminophenoxy)biphenyl, 3,3'- bis(4-aminophenoxy)biphenyl, 4,4'-(l,4-phenylenediisopropylidene)bis- benzeneamine, and 4,4'-(l,3-phenylenediisopropylidene)bisbenzene- amine, or combinations thereof. In particular embodiments, the diamine monomer is ODA, 2,2'-dimethylbenzidine, or both.

[0079] A non-limiting list of possible dianhydride ("diacid") monomers includes hydroquinone dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride, 4,4'-(4,4'- isopropylidene diphenoxy)bis(phthalic anhydride), 2,2-bis(3,4- dicarboxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, bis(3,4-dicarboxyphenyl) sulfoxide dianhydride, polysiloxane-containing dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,2',3'- benzophenone tetracarboxylic dianhydride, naphthalene-2,3,6,7- tetracarboxylic dianhydride, naphthalene- 1,4,5,8-tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-biphenyl sulfone tetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis(3,4- dicarboxyphenyl)sulfide dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4- dicarboxyphenyl)hexafluoropropane, 2,6-dichloronaphthalene- 1,4,5,8- tetracarboxylic dianhydride, 2,7-dichloronaphthalene- 1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene- 1,4,5,8-tetracarboxylic dianhydride, phenanthrene-8,9,10-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, benzene- 1,2,3,4-tetracarboxylic dianhydride, and thiophene-2,3,4,5-tetracarboxylic dianhydride. In particular embodiments, the dianhydride monomer is BPDA, PMDA, or both.

[0080] In some aspects, the molar ratio of the dianhydride to the total diamine is 0.4:1 to 1.6:1, 0.5:1 to 1.5:1, 0.6:1 to 1.4:1, 0.7:1 to 1.3:1, or specifically 0.8:1 to 1.2:1. In further aspects, the molar ratio of the dianhydride to the polyfunctional amine (e.g., triamine) is 2:1 to 140:1, 3:1 to 130:1, 4:1 to 120:1, 5:1 to 110:1, 6:1 to 100:1, 7:1 to 90:1, or specifically 8:1 to 80:1. Monoanhydride groups can also be used. Non-limiting examples of monoanhydride groups include 4-amino-1,8-naphthalic anhydride, endobicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride, citraconic anhydride, trans-1,2-cyclohexanedicarboxylic anhydride, 3,6-dichlorophthalic anhydride, 4,5-dichlorophthalic anhydride, tetrachlorophthalic anhydride, 3,6-difluorophthalic anhydride, 4,5-difluorophthalic anhydride, tetrafluorophthalic anhydride, maleic anhydride, 1-cyclopentene-1,2-dicarboxylic anhydride, 2,2-dimethylglutaric anhydride, 3,3-dimethylglutaric anhydride, 2,3-dimethylmaleic anhydride, 2,2-dimethylsuccinic anhydride, 2,3-diphenylmaleic anhydride, phthalic anhydride, 3-methylglutaric anhydride, methylsuccinic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride, 2,3-pyrazinedicarboxylic anhydride, or 3,4-pyridinedicarboxylic anhydride. Specifically, the monoanhydride group can be phthalic anhydride.

[0081] In another embodiment, the polymer composition used to make the polymeric aerogel layer comprises a polyfunctional amine monomer having at least three primary amine functional groups. The polyfunctional amine can be a substituted or unsubstituted aliphatic polyfunctional amine, a substituted or unsubstituted aromatic polyfunctional amine, or a polyfunctional amine comprising a combination of aliphatic and two aromatic groups or a combination of aromatic and two aliphatic groups. A non-limiting list of possible polyfunctional amines includes propane-1,2,3-triamine, 2-aminomethylpropane-1,3-diamine, 3-(2- aminoethyl)pentane-1,5-diamine, bis(hexamethylene)triamine, N',N'-bis(2- aminoethyl)ethane-1,2-diamine, N',N'-bis(3-aminopropyl)propane-1,3-diamine, 4-(3- aminopropyl)heptane-1,7-diamine, N',N'-bis(6-aminohexyl)hexane-1,6-diamine, benzene-1,3,5-triamine, cyclohexane-1,3,5-triamine, melamine, N-2-dimethyl-1,2,3- propane triamine, diethylenetriamine, 1-methyl or 1-ethyl or 1-propyl or 1-benzyl substituted diethylenetriamine, 1,2-dibenzyl diethylenetriamine, lauryldiethylenetriamine, N-(2-hydroxypropyl)diethylenetriamine, N,N-bis(1-methylheptyl)-N-2-dimethyl-1,2,3- propane triamine, 2,4,6-tris(4-(4-aminophenoxy)phenyl)pyridine, N,N-dibutyl-N-2- dimethyl-1,2,3-propane triamine, 4,4'-(2-(4-aminobenzyl)propane-1,3-diyl)diphenylamine, 4-((bis(4-aminobenzyl)amino)methyl)aniline, 4-(2-(bis(4- aminophenethyl)amino)ethyl)aniline, 4,4'-(3-(4-aminophenethyl)pentane-1,5-diyl)diphenylamine, 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), 4,4',4"-methanetriyltrianiline, N,N,N',N'-tetrakis(4-aminophenyl)-1,4-benzenediamine, polyoxypropylenetriamine, octakis(aminophenyl)cage polysilsesquioxane, or combinations thereof. A specific example of a polyoxypropylenetriamine is Jeffamine® T-403, available from Huntsman Corporation, Woodlands, Texas, USA. In a particular embodiment, the aromatic polyfunctional amine can be 1,3,5-tris(4- aminophenoxy)benzene or 4,4',4"-methanetriyltrianiline. In some embodiments, the polyfunctional amine comprises three primary amine groups and one or more than one secondary and / or tertiary amine groups, for example, N',N'-bis(4-aminophenyl)benzene-1,4-diamine. T-403. In a particular embodiment, the aromatic polyfunctional amine can be 1,3,5-tris(4- aminophenoxy)benzene or 4,4',4"-methanetriyltrianiline. In some embodiments, the polyfunctional amine comprises three primary amine groups and one or more than one secondary and / or tertiary amine groups, for example, N',N'-bis(4-aminophenyl)benzene-1,4-diamine.

[0082] Non-limiting examples of capping agents or capping groups include amines, maleimides, nadimides, acetylenes, biphenylenes, norbornenes, cycloalkyls, and N- propargyl groups, particularly those derived from reagents including 5-norbornene-2,3- dicarboxylic anhydride (Nadic anhydride, NA), methyl-Nadic anhydride, hexachloro-Nadic anhydride, cis-4-cyclohexene-1,2-dicarboxylic anhydride, 4-amino-N-propargyl phthalimide, 4-ethynyl phthalic anhydride, and maleic anhydride.

[0083] The properties or characteristics of the final polymer are significantly influenced by the choice of monomers used to make the polymer. Factors to consider in choosing monomers include the properties of the final polymer, such as flexibility, thermal stability, coefficient of thermal expansion (CTE), coefficient of hydroscopic expansion (CHE), and any other properties that are particularly desired, as well as cost. In general, certain important properties of the polymer can be identified for a polymer for a particular use. Other properties of the polymer can be less important, or can have a wider range of acceptable values; a number of different combinations of monomers can be used.

[0084] In some cases, the backbone of the polymer can include substituents. The substituents (e.g., oligomers, functional groups, etc.) can be bonded directly to the backbone or connected to the backbone through a linker (e.g., a connecting chain or a flexible connecting chain). In other embodiments, compounds or particles can be incorporated (e.g., blended and / or encapsulated) into the polyimide structure without being covalently bound to the polyimide structure. In some cases, the incorporation of the compounds or particles can be performed during the polyamide reaction. In some cases, the particles can aggregate, resulting in a polyimide having domains of non-covalently bound compounds or particles at different concentrations.

[0085] Certain properties of the polyimide can be influenced by incorporating certain compounds into the polyimide. The choice of monomers is one way to influence certain properties. Another way to influence properties is to add compounds or modifying moieties to the polyimide.

[0086] C. Preparation of the polymer aerogel layer

[0087] Polymer aerogel films that can be used in at least some of the present laminates are commercially available. Non-limiting examples of such films include Blueshift Rolling thin films (available from Blueshift Materials, Inc. (Spencer, MA, USA) and Aerogel films (available from Aerogel Technologies, LLC) in certain aspects, Blueshift Rolling thin films are preferred.

[0088] In addition, the polymeric aerogels (films, raw shapes or blocks, etc.) can be manufactured using the methods described in Rodman et al. International Patent Application Publication No. WO 2014 / 189560, Sakaguchi et al. International Patent Application Publication No. WO 2017 / 07888, Yang et al. International Patent Application Publication No. WO 2018 / 078512, Sakaguchi et al. International Patent Application Publication No. WO 2018 / 140804, and Irvin et al. International Patent Application Publication No. WO 2019 / 006184, Ejaz et al. International Patent Application No. PCT / US2019 / 029191, Poe et al. U.S. Patent Application Publication No. 2017 / 0121483, and / or Sakaguchi et al. U.S. Patent No. 9963571, all of which are incorporated herein by reference, in addition to the processes described below.

[0089] Non-limiting processes that can be used to manufacture polymeric aerogel layers suitable for use in the present laminates are provided below. These processes can include: 1) preparing a polymeric gel; 2) optional solvent exchange; 3) drying the polymeric solution to form an aerogel; and (4) attaching the polymeric aerogel film to a substrate.

[0090] 1. Formation of a Polymeric Gel

[0091] The first stage of aerogel synthesis can be the synthesis of a polymerized gel. For example, if a polyimide aerogel is desired, at least one acid monomer can be reacted with at least one diamine monomer in a reaction solvent to form a polyamide acid. As described above, many acid monomers and diamine monomers can be used to synthesize a polyamide acid. In one aspect, the polyamide acid is contacted with an imidization catalyst in the presence of a chemical dehydrating agent to form a polymerized polyimide gel via an imidization reaction. “Imidization” is defined as the conversion of a polyimide precursor to an imide. Any imidization catalyst suitable for driving the conversion of a polyimide precursor to a polyimide state is suitable. Non-limiting examples of chemical imidization catalysts include pyridine, methylpyridine, quinoline, isoquinoline, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), triethylenediamine, dimethylpyridine, N-methylmorpholine, triethylamine, tripropylamine, tributylamine, other trialkyl amines, 2-methylimidazole, 2-ethyl-4-methylimidazole, imidazole, other imidazoles, and combinations thereof. Any dehydrating agent suitable for forming imide rings from amide acid precursors is suitable for use in the methods of the present application. Preferred dehydrating agents include at least one compound selected from the group consisting of acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, phosphorus trichloride, and dicyclohexylcarbodiimide.

[0092] In one aspect of the application, one or more diamine monomers and one or more multifunctional amine monomers are premixed in one or more solvents, and then treated with one or more small amounts of dianhydride (e.g., diacid monomer) added sequentially in predetermined time increments while monitoring viscosity. The desired viscosity of the polymerized solution can be 50 cP to 20,000 cP, or specifically 500 cP to 5,000 cP. The reaction can be carried out by using incremental addition of dianhydride while monitoring viscosity to produce a non-crosslinked aerogel. For example, a triamine monomer (23 equivalents) can be added to a solvent to yield a 0.0081 molar solution. A first diamine monomer (280 equivalents) can be added to this solution, followed by a second diamine monomer (280 equivalents). Next, dianhydride (552 total equivalents) can be added in smaller amounts sequentially in predetermined time increments while monitoring viscosity. The dianhydride can be added until the viscosity reaches 1,000 cP to 1,500 cP. For example, a first portion of dianhydride can be added, the reaction can be stirred (e.g., for 20 minutes), a second portion of dianhydride can be added, and a sample of the reaction mixture can be analyzed for viscosity. After stirring for an additional period of time (e.g., 20 minutes), a third portion of dianhydride can be added, and a sample can be taken for viscosity analysis. After further stirring for a desired period of time (e.g., 10 hours to 12 hours), a monoacid anhydride (96 equivalents) can be added. After reaching the target viscosity, the reaction mixture can be stirred for a desired period of time (e.g., 10 hours to 12 hours) or the reaction can be deemed complete.

[0093] The reaction temperature for gel formation can be determined by routine experimentation depending on the starting materials. In preferred embodiments, the temperature can be greater than or equal to, or between any two of, 15 °C, 20 °C, 30 °C, 35 °C, 40 °C, and 45 °C. After a desired amount of time (e.g., about 2 hours), the product can be isolated (e.g., filtered), and then a nitrogen-containing hydrocarbon (828 equivalents) and a dehydrating agent (1214 equivalents) can be added. The addition of the nitrogen-containing hydrocarbon and / or the dehydrating agent can be carried out at any temperature. In some embodiments, the nitrogen-containing hydrocarbon and / or the dehydrating agent are added to the solution at 20 °C to 28 °C (e.g., room temperature) and stirred at room temperature for a desired amount of time. In some cases, after the addition of the nitrogen-containing hydrocarbon and / or the dehydrating agent, the solution temperature is increased to 150 °C.

[0094] The reaction solvent can include dimethyl sulfoxide (DMSO), diethyl sulfoxide, N,N-dimethylformamide (DMF), N,N-diethylformamide, N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 1 -methyl-2-pyrrolidinone, N-cyclohexyl-2-pyrrolidinone, 1,13-dimethyl-2-imidazolidinone, diglycol dimethoxy ether, o-dichlorobenzene, phenol, cresol, xylenol, o-dihydroxybenzene, butyrolactone, hexamethylphosphoramide, and mixtures thereof. The reaction solvent and other reactants can be selected based on compatibility with the materials and methods applied; i.e., if the polymerized polyamide amide gel is cast onto a support film, injected into a moldable part, or poured into a shape for further processing into a workpiece. In a particular embodiment, the reaction solvent is DMSO.

[0095] With the above in mind, macropores can be introduced into the aerogel polymer matrix, and this macroporosity can be present in an amount, in the manner described in the SUMMARY. In one non-limiting manner, the formation of macropores relative to smaller mesopores and micropores can be controlled primarily by controlling the polymer / solvent kinetics during gel formation. By doing so, the pore structure can be controlled, and the amount and volume of macropores, mesopores, and micropores can be controlled. For example, a solidification additive that reduces the solubility of the polymer formed during polymerization, such as 1,4-diazabicyclo[2.2.2]octane, can produce a polymer gel containing more macropores than another solidification additive that improves the solubility of the resulting polymer, such as triethylamine. In another particular non-limiting example, increasing the ratio of rigid amines (e.g., p-phenylenediamine (p-PDA)) to more flexible diamines (e.g., ODA) incorporated into the polymer backbone when forming a polyimide aerogel can favor the formation of macropores over smaller mesopores and micropores.

[0096] The polymer solution can optionally be cast onto a casting sheet covered by a support film for a period of time. Casting can include spin casting, gravure coating, three-roll coating, roll blade coating, slot-die coating, dip coating, Meyer bar coating, or other techniques. In one embodiment, the casting sheet is a polyethylene terephthalate (PET) casting sheet. After a period of time, the polymerized reinforced gel is removed from the casting sheet and prepared for the solvent exchange process. In some embodiments, the cast film can be heated in stages to high temperatures to remove solvents and to convert amic acid functionalities in the polyamic acid to imides, also known as imidization, through a dehydration cyclization reaction. In some cases, the polyamic acid can be converted to a polyimide in solution by the addition of a chemical dehydrating agent, a catalyst, and / or heating.

[0097] In some embodiments, the polyimide polymer can be prepared by preparing a polyamide acid polymer in a reaction vessel. The polyamide acid is then formed into a sheet or film, which is subsequently treated with a catalyst or heat and catalyst to convert the polyamide acid to a polyimide.

[0098] The wet gel used to prepare the aerogel can be prepared by any known gel formation technique, for example adjusting the pH and / or temperature of a dilute metal oxide sol to the point at which gelation occurs.

[0099] 2. Optional solvent exchange

[0100] After polymer gel synthesis, in some cases it can be desirable to perform a solvent exchange, in which the reaction solvent is exchanged for a second, more desirable solvent. Thus, in one embodiment, a solvent exchange can be performed in which the polymerized gel is placed in a pressure vessel and immersed in a mixture comprising the reaction solvent and the second solvent. A high pressure atmosphere is then created within the pressure vessel, thereby forcing the second solvent into the polymerized gel and displacing a portion of the reaction solvent. Alternatively, the solvent exchange step can be performed without the use of a high pressure environment. Multiple rounds of solvent exchange can be desirable. In some embodiments, no solvent exchange is necessary.

[0101] The time required to perform the solvent exchange will vary depending on the type of polymer being exchanged and the reaction solvent and second solvent used. In one embodiment, the time for each solvent exchange can be from 1 hour to 168 hours, or any time period therein, including 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, or 23 hours, 24 hours, 25 hours, 50 hours, 75 hours, 100 hours, 125 hours, 150 hours, 155 hours, 160 hours, 165 hours, 166 hours, 167, or 168 hours. In another embodiment, each solvent exchange can be from about 1 minute to 60 minutes, or about 30 minutes. Exemplary second solvents include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, t-butanol, 3-methyl-2-butanol, 3,3-dimethyl-2-butanol, 2-pentanol, 3-pentanol, 2,2-dimethylpropan-1-ol, cyclohexanol, diethylene glycol, cyclohexanone, acetone, acetylacetone, 1,4-dioxane, diethyl ether, dichloromethane, trichloroethylene, chloroform, carbon tetrachloride, water, and mixtures thereof. In certain non-limiting embodiments, the second solvent can have a suitable freezing point for performing a supercritical or subcritical drying step. For example, the freezing point of t-butanol is 25.5 °C and the freezing point of water is 0 °C at one atmosphere. However, alternatively, drying can be performed without the use of a supercritical or subcritical drying step, such as by evaporation drying techniques, as described below.

[0102] The temperature and pressure used during the solvent exchange process can vary. The duration of the solvent exchange process can be adjusted by performing the solvent exchange at varying temperatures or atmospheric pressures or both, provided that the pressure and temperature within the pressure vessel do not cause the first solvent or the second solvent to exit the liquid phase and become a gas phase, vapor phase, solid phase, or supercritical fluid. Generally, higher pressures and / or temperatures will decrease the time required to perform the solvent exchange, while lower temperatures and / or pressures will increase the time required to perform the solvent exchange.

[0103] 3. Cooling and Drying

[0104] In one embodiment, after solvent exchange, the polymerized gel can be exposed to supercritical drying. In this case, the solvent in the gel can be removed by supercritical CO2 extraction.

[0105] In another embodiment, after solvent exchange, the polymerized gel can be exposed to subcritical drying. In this case, the gel can be cooled below the freezing point of the second solvent and subjected to a freeze-drying process to produce an aerogel. For example, if the second solvent is water, the polymerized gel is cooled to below 0°C. After cooling, the polymerized gel can be subjected to a period of vacuum to allow the second solvent to sublimate.

[0106] In yet another embodiment, after solvent exchange, after most of the second solvent has been removed by sublimation, the polymerized gel can be exposed to subcritical drying with optional heating. In this case, the partially dried gel material is heated to a temperature near or above the boiling point of the second solvent for a period of time. The period of time can range from a few hours to several days, although a typical period of time is on the order of 4 hours. During the sublimation process, a portion of the second solvent present in the polymerized gel is removed, leaving a gel that can have macropores, mesopores, or micropores, or any combination or all of these pore sizes. Upon completion or near completion of the sublimation process, an aerogel is formed.

[0107] In another embodiment, after solvent exchange, the polymerized gel can be dried under ambient conditions, for example, by removing the solvent under a gas stream (e.g., air, anhydrous gas, an inert gas (e.g., nitrogen (N2)), etc.). In addition, passive drying techniques can be used, for example, simply exposing the gel to ambient conditions without the use of a gas stream.

[0108] Once cooled or dried, the film or raw shape can be configured for use in the laminates of the present application. For example, the film or raw shape can be processed (e.g., by cutting or grinding) into a desired shape, such as a square, rectangle, circle, triangle, irregular shape, random shape, etc. In addition, as discussed above, the film or raw shape can be affixed to a support material, for example, with an adhesive. In alternative embodiments, the support material can be incorporated into the matrix of the polymer aerogel, which is discussed below.

[0109] 4. Incorporation of Reinforcing Layers into the Matrix of the Polymer Aerogel

[0110] In addition to the methods discussed above for attaching the polymer aerogel to a support material using an adhesive, optional embodiments of the present application can include incorporating the support material into the polymer matrix without the use of an adhesive to produce a reinforced polymer aerogel. Notably, during the manufacturing process of a non-reinforced polymer aerogel, a reinforcing support film can be used as a carrier to support the gelled film during processing. During rewinding, the gelled film can be irreversibly pressed into the carrier film. Pressing the gelled film into the carrier film can significantly increase durability. In another case, during the solvent-casting step described above, the polymer solution can be cast into a reinforcing material or support material.

[0111] Substrate selection and direct casting can optimize (e.g., minimize) the thickness of the resulting reinforced aerogel material. This method can also be extended to produce fiber-reinforced polymer aerogels - take the example of internally reinforced polyimide aerogels. The method can include: (a) forming a polyamic acid solution from a mixture of dianhydride and diamine monomers in a polar solvent such as DMSO, DMAc, NMP, or DMF; (b) contacting the polyamic acid solution with the chemical curing agent and chemical dehydrating agent listed above to initiate chemical imidization; (c) casting the polyamic acid solution onto a fiber support and allowing it to penetrate before gelling; (d) allowing the catalyzed polyamic acid solution to gel around and within the fiber support during chemical imidization; (e) performing an optional solvent exchange to facilitate drying; and (f) removing the transient liquid phase contained in the gel with supercritical, subcritical, or ambient drying to yield an internally reinforced aerogel.

[0112] Implementation Example

[0113] The present application will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the application in any manner. Those of ordinary skill in the art will readily recognize a variety of noncritical parameters that can be changed or modified to yield essentially the same results.

[0114] Table 1 lists the acronyms for the compounds used in the following examples.

[0115] Table 1

[0116]

[0117] The structures of the raw materials are shown below.

[0118]

[0119] Example 1

[0120] (Preparation of highly branched BPDA / DMB-ODA polyimide)

[0121] A reaction vessel with a mechanical stirrer and a water jacket was used. The water flow through the reaction vessel jacket was adjusted to maintain the temperature between 18 °C and 35 °C. DMSO (108.2 pounds, 49.1 kg) was added to the reaction vessel and the mechanical stirrer speed was adjusted to 120 rpm to 135 rpm. TAPOB (65.13 g) was added to the solvent. DMB (1081.6 g) was added to the solution followed by the addition of ODA (1020.2 g). A first portion of BPDA (1438.4 g) was then added. After stirring for 20 minutes, a sample of the reaction mixture was analyzed for viscosity using a Brookfield DV1 viscometer (Brookfield, AMETEK, USA). A second portion of BPDA (1407.8 g) was added and the reaction mixture was stirred for an additional 20 minutes. A third portion of BPDA (138.62 g) was added and the reaction mixture was stirred for 20 minutes. A sample of the reaction mixture was analyzed for viscosity. After stirring for 8 hours, PA (86.03 g) was added. The resulting reaction mixture was stirred until no more solids were seen. After 2 hours, the product was removed from the reaction vessel, filtered, and weighed.

[0122] Example 2

[0123] (Preparation of highly branched polyimide aerogel monoliths by freeze-drying)

[0124] The resin prepared in Example 1 (about 10000 grams) was mixed with triethylamine (about 219 grams) and acetic anhydride (about 561 grams) for 5 minutes. After mixing, the resulting solution was poured into a 15” x 15” square mold and left for 48 hours. The gel-like object was removed from the mold and placed in an acetone bath. After 24 hours of immersion, the acetone bath was exchanged for fresh acetone. The immersion and exchange process was repeated five times. After the last exchange, the bath was replaced with t-butanol. After 24 hours of immersion, the t-butanol bath was exchanged for fresh t-butanol. The immersion and exchange process was repeated three times. The part was then flash frozen and subcritically dried at 5 °C for 96 hours followed by vacuum drying at 50 °C for 48 hours. The final recovered aerogel part had an open-cell structure with a density of 0.22 g / cm3as measured using an AutoPore V 9605 fully automatic mercury porosimeter (Micromeritics® Instrument Company, USA) according to ASTM D4404-10 and a specific surface area of 0.22 m2 / g as measured using a Micromeritics® ASAP 2020 surface area and porosity analyzer (Micromeritics® Instrument Company, USA) according to ASTM D4823-17. AutoPore V 9605 fully automatic mercury porosimeter Instrument Company, USA) measured a density of 0.22 g / cm3 3porosity of 88.5%, a compressive modulus of 2.2 MPa as determined by American Standard Test Method (ASTM) D395-16, and a compressive strength at 25% strain of 3.5 MPa as determined by ASTM D395-16. Pore size distribution was measured according to ASTM D4404-10 using a Micromeritics AutoPore V9605 automated mercury porosimeter (Micromeritics Instrument Inc., USA), and the pore size distribution is shown in Figure 7 According to the data, 100% of the pores were macropores with an average pore diameter of about 1200 nm, confirming the production of an aerogel with a macroporous structure.

[0125] Example 3

[0126] (Preparation of highly branched polyimide aerogel monoliths by thermal drying)

[0127] The resin prepared in Example 1 (about 10000 grams) was mixed with triethylamine (about 219 grams) and acetic anhydride (about 561 grams) at a temperature of 10°C to 35°C for 5 minutes. After mixing, the resulting solution was poured into a 15” x 15” square mold and left for 48 hours. The gel-like object was removed from the mold and placed in an acetone bath. After 24 hours of immersion, the acetone bath was exchanged for fresh acetone. The immersion and exchange process was repeated five times. After the last exchange, the part was dried using an ambient (about 20°C to 30°C) drying process for over 48 hours to evaporate most of the acetone, followed by a thermal drying process at 50°C for 4 hours, 100°C for 2 hours, 150°C for 1 hour, and then 200°C for 30 minutes. The final recovered aerogel had similar properties as observed in Example 2.

[0128] Example 4

[0129] (Preparation of highly branched polyimide)

[0130] ​At a temperature of 18 °C to 35 °C, TAPOB (about 2.86 g) was added to a reaction vessel containing about 2523.54 g of DMSO as described in Example 1. To this solution was added a first portion of DMB (about 46.75 g), followed by a first portion of ODA (about 44.09 g). After stirring for about 20 minutes, a first portion of BPDA (about 119.46 g) was added. After stirring for about 20 minutes, TAPOB (about 2.86 g), DMB (about 46.75 g), and ODA (about 44.09 g) were added. After stirring for about 20 minutes, BPDA (about 119.46 g) was added. After stirring for about 20 minutes, TAPOB (about 2.86 g), DMB (about 46.75 g), and ODA (about 44.09 g) were added. After stirring for about 20 minutes, BPDA (about 119.46 g) was added. After stirring for about 8 hours, PA (about 50.12 g) was added. The resulting reaction mixture was stirred until no more solids were seen. After about 2 hours, the product was removed from the reaction vessel, filtered, and weighed.

[0131] Example 5

[0132] (Preparation of highly branched polyimide aerogel monoliths by freeze-drying)

[0133] At a temperature of 18 °C to 35 °C, the resin prepared in Example 4 (about 400 grams) was mixed with 2-methylimidazole (about 53.34 grams) for 5 minutes, followed by benzoic anhydride (about 161.67 grams) for 5 minutes. After mixing, the resulting solution was poured into a 3” x 3” square mold and placed in an oven at 75 °C for 30 minutes, then left at room temperature overnight. The gel-like object was removed from the mold and placed in an acetone bath. After 24 hours of immersion, the acetone bath was exchanged for fresh acetone. The immersion and exchange process was repeated five times. After the last exchange, the bath was replaced with t-butanol. After 24 hours of immersion, the t-butanol bath was exchanged for fresh t-butanol. The immersion and exchange process was repeated three times. The part was then frozen on a freeze rack and subcritically dried at 5 °C for 96 hours, followed by vacuum drying at 50 °C for 48 hours. The final recovered aerogel part had an open-cell structure with a density of 0.15 g / cm3and a porosity of 92.2% as measured by scanning electron microscopy (SEM) observations on a Phenom Pro scanning electron microscope (Phenom-World, Netherlands) and using a Micromeritics AutoPore V 9605 automated mercury porosimeter (Micromeritics Instrument Company, USA) according to ASTM D4404-10. AutoPore V 9605 automated mercury porosimeter Instrument Company, USA). The pore size distribution was measured using a Micromeritics AutoPore V 9605 automated mercury porosimeter (Micromeritics Instrument Company, USA) according to ASTM D4404-10. 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 <000009measured by a Micromeritics® Accelerated Surface Area and Porosimetry (ASAP®) 2020 instrument (Micromeritics® Instrument Company, USA) and the pore size distribution is shown in Figure 8 According to the data, 96.3% of the pore volume of the shaped aerogel was composed of pores with an average pore diameter greater than 50 nm, thus forming a macroporous structured aerogel.

[0134] Example 6

[0135] (Preparation of highly branched polyimide)

[0136] At a temperature of 18 °C to 35 °C, TAPOB (about 2.05 g) was added to a reaction vessel containing about 2776.57 g of DMSO as described in Example 1. To this solution was added a first portion of DMB (about 33.54 g), followed by a first portion of ODA (about 31.63 g). After about 20 minutes of stirring, a first portion of PMDA (about 67.04 g) was added. After about 20 minutes of stirring, TAPOB (about 2.05 g), DMB (about 33.54 g), and ODA (about 31.63 g) were added. After about 20 minutes of stirring, PMDA (about 67.04 g) was added. After about 20 minutes of stirring, TAPOB (about 2.05 g), DMB (about 33.54 g), and ODA (about 31.63 g) were added. After about 20 minutes of stirring, PMDA (about 67.04 g) was added. After about 8 hours of stirring, PA (about 18.12 g) was added. The resulting reaction mixture was stirred until no more solids were seen. After about 2 hours, the product was removed from the reaction vessel, filtered, and weighed.

[0137] Example 7

[0138] (Preparation of highly branched polyimide aerogel monoliths by freeze-drying)

[0139] The resin prepared in Example 6 (about 400 grams) was mixed with 2-methylimidazole (about 40.38 grams) for 5 minutes at a temperature of 18 °C to 35 °C, then mixed with benzoic anhydride (about 122.38 grams) for 5 minutes. After mixing, the resulting solution was poured into a 3” x 3” square mold and placed in an oven at 75 °C for 30 minutes, then left at room temperature overnight. The gel-like object was removed from the mold and placed in an acetone bath. After 24 hours of immersion, the acetone bath was exchanged for fresh acetone. The process of immersion and exchange was repeated five times. After the last exchange, the bath was replaced with t-butanol. After 24 hours of immersion, the t-butanol bath was exchanged for fresh t-butanol. The process of immersion and exchange was repeated three times. The part was then frozen on a freeze frame and subcritically dried at 5 °C for 96 hours, then vacuum dried at 50 °C for 48 hours. The final recovered aerogel part had an open-cell structure as observed by scanning electron microscopy (SEM) on a Phenom Pro scanning electron microscope (Phenom-World, Netherlands) and a density of 0.23 g / cm3, a porosity of 82.7% as measured according to ASTM D4404-10 using a Micromeritics AutoPore V 9605 automated mercury porosimeter (Micromeritics Instrument Inc., USA). AutoPore V 9605 automated mercury porosimeter (Micromeritics Instrument Inc., USA). 3 The pore size distribution was measured according to ASTM D4404-10 using a Micromeritics AutoPore V 9605 automated mercury porosimeter (Micromeritics Instrument Inc., USA) and is shown in Figure 9 According to the data, 90.6% of the aerogel’s pore volume was composed of pores with an average pore diameter greater than 50 nm.

[0140] Example 8

[0141] Preparation of highly branched polyimide films

[0142] ​​A reaction vessel with a mechanical stirrer and a water jacket was used. The water flow through the reaction vessel jacket was adjusted to maintain the temperature at 20 °C to 28 °C. DMSO (108.2 pounds, 49.1 kg) was added to the reaction vessel and the mechanical stirrer speed was adjusted to 120 rpm to 135 rpm. TAPOB (65.03 g) was added to the solvent. DMB (1080.96 g) was added to the solution followed by ODA (1018.73 g). A first portion of BPDA (1524.71 g) was then added. After stirring for 20 minutes, a sample of the reaction mixture was analyzed for viscosity. A second portion of BPDA (1420.97 g) was added and the reaction mixture was stirred for an additional 20 minutes. A sample of the reaction mixture was analyzed for viscosity. A third portion of BPDA (42.81 g) was added and the reaction mixture was stirred for an additional 20 minutes. A sample of the reaction mixture was analyzed for viscosity. After stirring for 8 hours, PA (77.62 g) was added. The resulting reaction mixture was stirred until no more solids were seen. After 2 hours, the resin was removed from the reaction vessel, filtered, and weighed.

[0143] The resin (10000 grams) was mixed with 2-methylimidazole (250 grams) for 5 minutes. Benzoic anhydride (945 grams) was added and the solution was mixed for an additional 5 minutes. After mixing, the resulting solution was poured onto a moving polyester substrate that was heated in an oven at 100 °C for 30 seconds. The gelled film was collected and placed in an acetone bath. After 24 hours of soaking, the acetone bath was exchanged for fresh acetone. The soaking and exchange process was repeated six times. After the last exchange, the gelled film was removed. The acetone solvent was evaporated at room temperature under a stream of air followed by drying at 200 °C for 2 hours. The final recovered aerogel part had an open-cell structure with a density of 0.20 g / cm3, a porosity of 80%, and an average pore size of 400 nm as measured by scanning electron microscopy (SEM) observations on a Phenom Pro scanning electron microscope (Phenom-World, Netherlands) and an AutoPore V 9605 mercury porosimeter (Micromeritics® Instrument Company, USA) according to ASTM D4404-10. The tensile strength and elongation of the final recovered film at room temperature were 1200 psi (8.27 MPa) and 14%, respectively, as measured according to ASTM D882-02. The average pore size of the film was 400 nm. 3

[0144] Example 9

[0145] Preparation of a Copper Clad Polyimide Aerogel Laminate

[0146] ​​A laminate with a polyimide aerogel layer bonded between two copper layers was prepared by hot lamination of the aerogel film with adhesive sheets on either side of the aerogel film. The thickness of each copper foil layer was 1.4 mil, the polyimide aerogel layer was Blueshift film.

[0147] Prior to lamination, The film was dried in a convection oven at 120°C for 30 minutes. After assembling the aerogel film between two adhesive sheets with a copper foil layer on top, the sample was placed in a vacuum press. Three different low Dk / Df adhesives were used to make the copper clad laminates: Teflon FEP (Dupont), Pyralux GPL (Dupont), and TSU 510 (Toyo Chem).

[0148] The press was heated to 180°C using a temperature gradient of 5°C / min and the pressure was increased from 4 psi to 300 psi. The press was then held isothermally at 180°C for 10 to 60 minutes depending on the type of adhesive used. The press was then cooled to 50°C using a temperature gradient of 5°C / min and the pressure was held at 300 psi.

[0149] Example 10

[0150] (Dielectric properties of polyimide aerogel film)

[0151] The dielectric constant (Dk) and loss tangent (Df) properties of the Blueshift film were measured at 1 MHz and 1 GHz according to IPC TM-650 test method manual 2.5.5.9. Parallel plate method. The samples were conditioned at 23 ± 5°C and 50 ± 5% relative humidity for at least 24 hours prior to testing. The thickness of the polyimide aerogel film used was 148 microns. The dielectric properties are listed in Table 1.

[0152] Table 1

[0153] Frequency Average Dk Average Df 1 MHz 1.400 0.0006 1 GHz 1.500 0.0006

[0154] Example 11

[0155] (Dielectric properties of polyimide aerogel film at high frequency)

[0156] The dielectric constant (Dk) and loss tangent (Df) of a polyimide aerogel film with a thickness of 157.8 microns were measured at 10 GHz using a Damaskos wafer tester. The results were a Dk of 1.45 and a Df of 0.0046.

[0157] Example 12

[0158] (Dielectric Properties of Polyimide Aerogel Stockshape)

[0159] The dielectric constant (Dk) and dissipation factor (Df) of polyimide aerogel samples having a thickness of 10.2 mm were measured at room temperature (22 °C, 22% relative humidity) by a DI 08 type sheet tester and a DI 900T open resonator using CAVITY TM Controlled Anritsu VectorStar vector network analyzer. The sheet tester measurements followed ASTM D 2520 Part C. Table 2 shows the average dielectric constant (Dk) and dissipation factor (Df) measured in four directions (X1, X2, Y1, and Y2) using the 08 type sheet tester.

[0160] Table 2

[0161] Frequency.GHz Average Dk Average Df 0.8 1.243 0.00042 1.3 1.245 0.00050 2.5 1.248 0.00053 4.5 1.251 0.00073 7.2 1.254 0.00068

[0162] Table 3 shows the average dielectric constant (Dk) and dissipation factor (Df) measured in two directions (X, Y) using the 900T open resonator over a frequency of 7.3 GHz to 50 GHz.

[0163] Table 3

[0164]

[0165] Example 13

[0166] (Dielectric Properties of Polyimide Aerogel Copper Clad Laminate)

[0167] The dielectric constant (Dk) and dissipation factor (Df) of an etched sample of a polyimide aerogel copper clad laminate of a polyimide aerogel film having a thickness of 161 microns was measured at 10 GHz. The results were Dk of 2.0 and Df of 0.004.

[0168] The above specification and examples provide a complete description of the structure and use of illustrative embodiments. Although certain embodiments have been described above with some specificity, many changes can be made to these embodiments without departing from the scope of the application. Thus, the various illustrative embodiments of the devices and methods are not intended to limit the scope of the application to particular forms encompassed while providing a complete description of the illustrative embodiments. Rather, they are intended to cover all modifications and alternatives falling within the scope of the claims and to include all equivalents of the depicted embodiments. For example, elements can be omitted or combined as a single structure and / or connections can be replaced. Further, aspects of any of the above-described examples can be combined with aspects of any other described examples to form further examples having comparable or different properties and / or functions and addressing the same or different problems. Similarly, it should be understood that the benefits and advantages described above can relate to one embodiment or can relate to a combination of embodiments.

[0169] The claims are not intended to include, and should not be interpreted to include, the apparatuses and steps in their exact, complete, and recited order of operation, unless specifically recited in the claims.

Claims

1. A laminate comprising: two or more electrically conductive layers comprising a first electrically conductive layer and a second electrically conductive layer, the electrically conductive layers each comprising at least 90 wt% copper; and two or more electrically insulating layers comprising a first electrically insulating layer and a second electrically insulating layer, wherein the first electrically insulating layer and the second electrically insulating layer are coupled to the first electrically conductive layer and the second electrically conductive layer, respectively, by one or more adhesive layers, wherein the first electrically insulating layer and the second electrically insulating layer are bonded by an additional adhesive layer, and wherein the electrically insulating layers each comprise an organic polymeric aerogel, wherein at least a portion of a front surface of the laminate is defined by the first electrically conductive layer of the electrically conductive layers; and at least a portion of a back surface of the laminate is defined by the second electrically conductive layer of the electrically conductive layers.

2. The laminate of claim 1, wherein the thickness of at least one of the electrically conductive layers is from 0.5 mil to 3.0 mil.

3. The laminate of claim 2, wherein the thickness of at least one of the electrically conductive layers is 0.7 mil.

4. The laminate of claim 1, wherein the areal density of at least one of the electrically conductive layers is from 0.35 ounces per square foot (oz / ft 2 ) to 3.0 ounces per square foot (oz / ft 2 ).

5. The laminate of claim 4, wherein the areal density of at least one of the electrically conductive layers is 0.5 oz / ft 2 .

6. The laminate of claim 1, wherein at least one of the organic polymeric aerogels comprises an open-cell structure.

7. The laminate of claim 1, wherein at least one of the organic polymeric aerogels comprises micropores, mesopores, and / or macropores.

8. The laminate of claim 7, wherein at least one of the organic polymeric aerogels has a pore volume; and at least 10% of the pore volume consists of macropores.

9. The laminate of claim 7, wherein at least one of the organic polymeric aerogels has a pore volume; and at least 10% of the pore volume consists of micropores and / or mesopores.

10. The laminate of claim 1, wherein at least one of the organic polymeric aerogels has an average pore diameter from 2.0 nm to 50 nm.

11. The laminate of claim 1, wherein at least one of the organic polymeric aerogels has an average pore diameter from 50 nm to 5000 nm.

12. The laminate of claim 11, wherein the average pore diameter is from 100 nm to 800 nm.

13. The laminate of claim 1, wherein at least one of the organic polymeric aerogels comprises at least 90 wt% organic polymer.

14. The laminate of claim 1, wherein at least one of the organic polymeric aerogels comprises at least 90 wt% polyimide, polyamide, polyaramid, polyurethane, polyurea, and / or polyester.

15. The laminate of claim 14, wherein at least one of the organic polymeric aerogels comprises at least 90 wt% polyimide.

16. The laminate of claim 1, wherein at least one of the organic polymeric aerogels has a thickness of less than 20 mil or equal to 20 mil.

17. The laminate of claim 16, wherein at least one of the organic polymeric aerogels has a thickness of less than 12 mil or equal to 12 mil.

18. The laminate of claim 17, wherein at least one of the organic polymeric aerogels has a thickness of less than 7.0 mil or equal to 7.0 mil.

19. The laminate of claim 1, wherein the thickness of at least one of the organic polymeric aerogels is from 3.0 mils to 20 mils.

20. The laminate of claim 1, wherein at least one of the organic polymeric aerogels is a polyimide aerogel having a decomposition temperature greater than or equal to 400 °C.

21. The laminate of claim 1, wherein at least one of the bonding layers comprises a fluoropolymer film.

22. The laminate of claim 1, wherein at least one of the bonding layers comprises a polyimide film.

23. The laminate of claim 1, wherein at least one of the bonding layers comprises a B-staged epoxy resin.

24. The laminate of claim 1, wherein at least one of the bonding layers has a dielectric constant at 10 GHz of less than or equal to 3.

5.

25. The laminate of claim 1, wherein at least one of the bonding layers has a dissipation factor at 10 GHz of less than or equal to 0.0040.

26. The laminate of claim 1, wherein at least one of the bonding layers has a decomposition temperature greater than or equal to 350 °C.

27. The laminate of claim 1, wherein at least one of the bonding layers has a glass transition temperature or melting point greater than or equal to 100 °C.

28. The laminate of claim 1, wherein at least one of the bonding layers has a thickness of from 0.3 mils to 5 mils.

29. The laminate of any one of claims 1 to 28, wherein: no electrically conductive layer is disposed between adjacent electrically insulating layers.

30. The laminate of claim 1, wherein the laminate has a thickness of from 5.0 mils to 100 mils.

31. The laminate of claim 1, wherein the laminate is disposed in a roll such that a portion of a front surface of the laminate faces a portion of a back surface of the laminate.

32. The laminate of claim 1, wherein the laminate has a dielectric constant at 10 GHz of less than or equal to 2.

0.

33. The laminate of claim 32, wherein the dielectric constant is less than or equal to 1.

75.

34. The laminate of claim 1, wherein the laminate has a dissipation factor at 10 GHz of less than or equal to 0.0025.

35. The laminate of claim 34, wherein the dissipation factor is less than or equal to 0.

002.

36. The laminate of claim 1, wherein: the laminate comprises one or more than one reinforcing layer, wherein: the bending stiffness of each reinforcing layer is at least 10% greater than the bending stiffness of each electrically conductive layer and electrically insulating layer; and / or for at least one of the electrically insulating layers, at least one of the reinforcing layers is at least partially embedded in the polymeric aerogel layer such that the Young’s modulus of the electrically insulating layer is at least 200 MPa; and / or for at least one of the electrically insulating layers, a plurality of fibers are dispersed in the polymeric aerogel layer such that the Young’s modulus of the electrically insulating layer is at least 200 MPa.

37. The laminate of claim 36, wherein at least one of the reinforcement layers comprises one or more unidirectional, woven, or nonwoven fibrous-containing sheets and / or one or more paper sheets.

38. The laminate of claim 1, wherein the laminate does not comprise fibers.

39. A circuit board comprising: the laminate of claim 1; and a solder resist layer bonded to at least one of the front surface and the back surface, the solder resist layer covering at least a majority of the surface, the solder resist layer comprising at least 90 wt% of a polymer.

40. The circuit board of claim 39, wherein the solder resist layer has a thickness of less than 3.2 mils or equal to 3.2 mils.

41. An apparatus comprising the circuit board of claim 39 or 40, wherein: the apparatus comprises an antenna electrically coupled to the circuit board; and / or the apparatus is an electronic amplifier, a radar system, or a communication system.

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