WO2024010787A1

WO2024010787A1 - Flexible laminate material

Info

Publication number: WO2024010787A1
Application number: PCT/US2023/026893
Authority: WO
Inventors: Brian AMOS; John C. FRANKOSKY; Franciscus Cornelis Joannes HULSEBOSCH; Scott Kennedy; Xiaolin Liu; Ying Wang; Robert Thomas Young
Original assignee: The Chemours Company Fc, Llc
Priority date: 2022-07-06
Filing date: 2023-07-05
Publication date: 2024-01-11
Also published as: TW202402540A

Abstract

A laminate article includes a dielectric substrate including a perfluorocopolymer matrix comprising a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer; an L-glass fabric embedded in the perfluorocopolymer matrix; and an additive material dispersed in the perfluorocopolymer matrix, in which the additive material is capable of absorbing ultraviolet light; and a conductive cladding disposed on a surface of the dielectric substrate.

Description

Background

[0001] Metal-clad laminates are used as printed-wiring board substrates in various electronics applications.

Summary

[0002] In an aspect, a laminate article includes a dielectric substrate including: a perfluorocopolymer matrix including a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer; an L-glass fabric embedded in the perfluorocopolymer matrix; and an additive material dispersed in the perfluorocopolymer matrix, in which the additive material is capable of absorbing ultraviolet light; and a conductive cladding disposed on a surface of the dielectric substrate.

[0003] Embodiments can include one or any combination of two or more of the following features.

[0004] The L-glass fabric includes yarn of L-glass, NL-glass, or L2-glass.

[0005] The laminate article has a thickness of between 20 pm and 200 pm, e.g., between 30 pm and 90 pm or between 30 pm and 60 pm.

[0006] The dielectric substrate has a dielectric constant at 10 GHz of between 2.10 and 2.70, e.g., between 2.10 and 2.40.

[0007] The dielectric substrate has a thermal coefficient of dielectric constant with a value of between -250 to +50 ppm/°C over a temperature range of 0 to 100 °C.

[0008] The dielectric substrate has a dissipation factor at 10 GHz of less than 0.0015, e.g., between 0.0006 and 0.001 or between 0.0006 and 0.0008.

[0009] The laminate article has a planar shape defining an X-Y plane, and in which a coefficient of thermal expansion of the laminate article in the X-Y plane is between 5 and 25 ppm/°C, e.g., between 14 and 20 ppm/°C or between 16 and 22 ppm/°C.

[0010] The fluorinated perfluorocopolymer includes a fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer and in which the nonfluorinated perfluorocopolymer includes a non-fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer.

[0011] The perfluorocopolymer matrix includes between 50 and 90 weight percent of the fluorinated perfluorocopolymer, e.g., between 10 and 50 weight percent of the non-fluorinated perfluorocopolymer.

[0012] A number of carboxyl end groups per million carbon atoms in the perfluorocopolymer matrix is sufficient for the laminate article to form no conductive anodic filaments (CAF).

[0013] A number of carboxyl end groups per million carbon atoms in the perfluorocopolymer matrix provides the laminate article with a peel strength between the dielectric substrate and the conductive cladding of greater than 2 Ib/inch.

[0014] The number of carboxyl end groups per million carbon atoms in the perfluorocopolymer matrix is between 30 and 70.

[0015] The fluorinated perfluorocopolymer has 5 or fewer carboxyl end groups per million carbon atoms.

[0016] The non-fluorinated perfluorocopolymer has between 100 and 300 carboxyl end groups per million carbon atoms.

[0017] The perfluorocopolymer matrix has a melt flow rate (MFR) of between 10 g/10 minutes and 30 g/10 minutes.

[0018] The perfluorocopolymer matrix has a solder float resistance of at least 10 seconds at 288 °C.

[0019] The L-glass has a basis weight of less than 100 g/m2, e.g., less than 50 g/m2. [0020] The L-glass fabric has a thickness between 10 pm and 100 pm, e.g., between 10 pm and 30 pm.

[0021] The L-glass fabric includes an aminosilane or methacrylate silane surface chemistry treatment.

[0022] The L-glass fabric includes a plasma-treated or corona-treated L-glass fabric.

[0023] The L-glass fabric is impregnated with a fluoropolymer.

[0024] The L-glass fabric includes a fluoropolymer coating.

[0025] The L-glass fabric is pretreated with a fluoropolymer treatment prior to incorporation into the laminate article.

[0026] The dielectric substrate includes between 5 and 20 volume percent of the L-glass fabric and between 80 and 95 volume percent of the perfluorocopolymer matrix.

[0027] A water contact angle of the L-glass fabric is between 0° and 60°.

[0028] The additive material includes inorganic particles, such as particles of cerium oxide, titanium dioxide, silicon dioxide, barium titanate, calcium titanate, or zinc oxide.

[0029] The additive material includes a thermoset polymer.

[0030] The additive material is present in the perfluorocopolymer matrix at a volume percent of less than 2%.

[0031] The additive material is dispersed homogeneously throughout the perfluorocopolymer matrix.

[0032] The conductive cladding is disposed on two opposing surfaces of the dielectric substrate.

[0033] The conductive cladding includes a copper foil. In some cases, the copper foil is disposed on the surface of the dielectric substrate by a lamination process. [0034] The conductive cladding has a thickness of less than 72 pm, e.g., between 5 pm and 18 pm.

[0035] The conductive cladding has a root mean square (RMS) roughness of less than 1 pm, e.g., less than 0.5 pm.

[0036] In an aspect, a printed-wiring board includes the laminate article having any of the preceding features, in which a conductor pattern is formed in the conductive cladding.

[0037] Embodiments can include one or any combination of two or more of the following features.

[0038] A through-hole is defined through a thickness of the laminate article; and including a copper film plating the through-hole.

[0039] In an aspect, a multilayer printed-wiring board includes a multilayer laminated structure including multiple printed-wiring boards according to the previous aspect.

[0040] Embodiments can include one or any combination of two or more of the following features.

[0041] The multilayer printed-wiring board includes a thermoplastic adhesive disposed between adjacent printed-wiring boards in the laminated structure. In some cases, the thermoplastic adhesive was bonded at a temperature between 0 and 200 °C below a melting point of the perfluorocopolymer matrix. In some cases, the thermoplastic adhesive was bonded at temperatures between 0 and 50 °C below the melting point of the perfluorocopolymer matrix.

[0042] The multilayer printed-wiring board includes a thermoset adhesive disposed between adjacent printed-wiring boards in the laminated structure. In some cases, the thermoset adhesive was cured at a temperature of between 150 °C and 250 °C.

[0043] A through-hole is defined through at least a portion of the thickness of the multilayer printed-wiring board; and including a copper film plating the through-hole. [0044] An antenna usable with a 5G communications network can include a printed-wiring board according to the foregoing aspects.

[0045] In an aspect, a method of making a multilayer printed-wiring board includes forming a conductor pattern in the conductive cladding of each of multiple of the laminate articles having any of the foregoing features to form respective printed-wiring boards; and laminating the multiple printed-wiring boards to form a multilayer laminated structure.

[0046] Embodiments can include one or any combination of two or more of the following features.

[0047] Laminating the multiple printed-wiring boards includes adhering adjacent printed-wiring boards using a thermoplastic adhesive. In some cases, the method includes bonding the thermoplastic adhesive at a temperature between 0 and 200 °C below a melting point of the perfluorocopolymer matrix. In some cases, the method includes bonding the thermoplastic adhesive at a temperature between 0 and 50 °C below the melting point of the perfluorocopolymer matrix.

[0048] Laminating the multiple printed-wiring boards includes adhering adjacent printed-wiring boards using a thermoset adhesive. In some cases, the method includes curing the thermoset adhesive at a temperature of between 150°C and 250°C.

[0049] The method includes defining a through-hole through at least a portion of the thickness of the multilayer laminated structure. In some cases, the method includes defining the through-hole in an ultraviolet laser drilling process.

[0050] In an aspect, a method of making a laminate article includes forming a layered article, the layered article including: first and second polymer films, each film including: a perfluorocopolymer matrix including a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer, and an additive material capable of absorbing ultraviolet light, an L-glass fabric disposed between the first and second polymer films; and a conductive cladding disposed in contact with the first film; and applying heat and pressure to the layered article to form the laminate article.

[0051] Embodiments can include one or any combination of two or more of the following features.

[0052] The fluorinated perfluorocopolymer includes a fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer and the non-fluorinated perfluorocopolymer includes a non-fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer.

[0053] Applying heat and pressure to the layered article includes compressing the layered article in a heated platen.

[0054] Applying heat and pressure to the layered article includes processing the layered article in a roll-to-roll lamination process.

[0055] Applying heat and pressure to the layered article includes applying to the layered article a temperature between 10 and 30 °C greater than a melting point of the perfluorocopolymer matrix.

[0056] Applying heat and pressure to the layered article includes applying to the layered article a temperature of between 300 °C and 400 °C.

[0057] Applying heat and pressure to the layered article includes applying to the layered article a pressure of between 200 psi and 1000 psi.

[0058] The method includes forming the first and second films in a melt processing and extrusion process. In some cases, forming the first and second films includes mixing the fluorinated perfluorocopolymer and the non-fluorinated perfluorocopolymer. In some cases, the method includes dispersing the additive material in the fluorinated perfluorocopolymer prior to mixing the fluorinated perfluorocopolymer and the non-fluorinated perfluorocopolymer.

[0059] The method includes treating the L-glass fabric with a fluoropolymer treatment. In some cases, treating the L-glass fabric with a fluoropolymer treatment includes coating the L-glass fabric with a fluoropolymer coating. In some cases, coating the L-glass fabric with a fluoropolymer coating includes coating the L-glass fabric in a solution coating process. In some cases, coating the L-glass fabric with a fluoropolymer coating includes depositing fluoropolymer particles on a surface of the L-glass fabric.

[0060] Each polymer film includes a first layer including the fluorinated perfluorocopolymer and the non-fluorinated perfluorocopolymer and a second layer including the non-fluorinated perfluorocopolymer, and in which each second layer is disposed in contact with the quartz fabric and each second layer is disposed in contact with the conductive cladding. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.

Brief Description of Drawings

[0061] Fig. 1 is a diagram of a flexible, metal-clad laminate.

[0062] Fig. 2 is a diagram of a layered structure for a flexible, metal-clad laminate.

[0063] Figs. 3A and 3B are diagrams of laminates with conductive anodic filaments.

[0064] Figs. 4 and 5 are diagrams of printed-wiring boards.

[0065] Fig. 6 is a diagram of a communications network.

[0066] Fig. 7 is a diagram of a roll-to-roll lamination process.

[0067] Fig. 8 is a flow chart of a method of making a flexible, metal-clad laminate.

[0068] Fig. 9 is a photograph of flexible copper clad laminates.

[0069] Fig. 10 is a plot of the thickness of various flexible copper clad laminates.

[0070] Fig. 11 is a plot of the resin content of various flexible copper clad laminates. [0071] Figs. 12A and 12B are plots of dimensional stability measurements for various flexible copper clad laminates.

[0072] Fig. 13 is a plot of the flatness of various flexible copper clad laminates.

[0073] Fig. 14 is a plot of the thickness of various flexible copper clad laminates.

[0074] Fig. 15 is a plot of the resin content of various flexible copper clad laminates.

[0075] Fig. 16 is a plot of the dielectric constant of various flexible copper clad laminates.

[0076] Fig. 17 is a plot of the dissipation factor of various flexible copper-clad laminates.

[0077] Figs. 18A and 18B are plots of dimensional stability measurements for various flexible copper clad laminates.

[0078] Fig. 19 is a plot of dissipation factor of blended PFA films as a function of the number of carboxyl end groups per 106 carbon atoms in the films.

[0079] Fig. 20 is a plot of dissipation factor of a laminate as a function the number of carboxyl end groups per 106 carbon atoms in blended PFA films.

[0080] Fig. 21 is a plot of copper peel strength of a laminate as a function the number of carboxyl end groups per 106 carbon atoms in blended PFA films.

Detailed Description

[0081] We describe here a metal-clad, flexible laminate with a low dielectric constant and low dissipation at high frequencies, e.g., at 10 GHz. The flexible laminates described here can be used for substrates for printed-wiring boards in high-frequency applications, such as for antennas for use in 5G cellular communications networks or for use with automotive radar, among other applications. The flexible laminates described here include a dielectric substrate formed of a perfluorocopolymer matrix with an L-glass fabric, e.g., a woven L- glass fabric, embedded therein. The perfluorocopolymer matrix includes a fully fluorinated perfluorocopolymer (referred to here as a “fluorinated perfluorocopolymer”) and a not fully fluorinated perfluorocopolymer (referred to here as a “non-fluorinated perfluorocopolymer”), such as fully fluorinated and not fully fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymers. An additive material in the dielectric substrate is capable of absorbing ultraviolet light such that the laminate can be drilled with an ultraviolet laser, e.g., for formation of through-holes through the thickness of the laminate. The flexible laminate is clad on one or both sides by a conductive cladding, such as a copper foil.

[0082] The presence of L-glass fabric results in a laminate that has a high degree of flatness, e.g., a degree of flatness that is sufficient to enable registration between multiple layers of laminates during a drilling process. For instance, in a multilayer laminate structure, a high degree of flatness enables registration during drilling of vias through the thickness of the multilayer structure. Without being bound by theory, it is believed that the difference between the coefficient of thermal expansion (CTE) of the L-glass fabric and the CTE of the perfluorocopolymer matrix, together with the relatively low modulus of L-glass fabric (e.g., as compared to quartz fabric), is such that the contraction of the L- glass fabric during cooling of the laminate is small enough to avoid generation of waviness in the laminate.

[0083] Referring to Fig. 1 , a metal-clad, flexible laminate 100 includes a dielectric substrate 102 and a conductive cladding, such as a metal (e.g., copper) foil 104a, 104b (referred to collectively as the conductive cladding 104) disposed on top and bottom surfaces 106a, 106b, respectively, of the dielectric substrate 102. Although the conductive cladding 104 is present on both surfaces 106a, 106b of the dielectric substrate 102 in Fig. 1 , in some examples, a conductive cladding is disposed on only a single surface (e.g., only the top surface 106a) of the dielectric substrate 102.

[0084] The dielectric substrate 102 of the flexible laminate 100 includes an L- glass fabric 108, such as a woven L-glass fabric e.g., an L-glass, NL-glass, or L2-glass yarn woven into a fabric), embedded in a perfluorocopolymer matrix 110 that includes a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer, such as fluorinated and non-fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymers. As discussed further below, the perfluorocopolymer matrix 110 provides the dielectric substrate 102 with a low dielectric constant and low dissipation factor, while the L-glass fabric enables the coefficient of thermal expansion (CTE) in the x-y plane of the dielectric substrate 102 to match the CTE of the conductive cladding 104. An additive material 112 that is capable of absorbing ultraviolet (UV) light, e.g., light having a wavelength of between 180 nm and 400 nm, is dispersed in the perfluorocopolymer matrix 110. The presence of the UV-responsive additive material 112 enables the flexible laminate 100 to be drilled by a UV laser, e.g., for formation of circuit structures such as vias through the thickness of the flexible laminate 100.

[0085] The flexible laminate 100 is a planar structure that has a thickness along the z-axis of less than about 200 pm or less than about 100 pm, e.g., between 20 pm and 200 pm, e.g., between 30 pm and 90 pm or between 30 pm and 60 pm. The thickness of the dielectric substrate 102 constitutes most of the thickness of the flexible laminate 100. For instance, the dielectric substrate 102 has a thickness along the z-axis of less than about 200 pm or less than about 100 pm, e.g., between 20 pm and 200 pm, e.g., between 30 pm and 90 pm or between 30 pm and 60 pm. Each conductive cladding 104a, 104b has a thickness along the z-axis of less than about 72 pm, e.g., less than about 18 pm, e.g., between 5 pm and 18 pm.

[0086] The dielectric substrate 102 of the flexible laminate 100 has a low dielectric constant, e.g., a dielectric constant at 10 GHz of less than about 2.7, e.g., between 2.1 and 2.7, e.g., between 2.1 and 2.4. The dielectric constant has a thermal coefficient with a value of between -250 and 50 ppm/°C, e.g., between -100 and 50 ppm/°C or between -50 and 25 ppm/°C, over a temperature range of 0 to 100 °C. The dielectric substrate 102 also has a low dissipation factor, e.g., a dissipation factor at 10 GHz of less than 0.0015, such as less than 0.001 or less than 0.0008, e.g., between 0.0002 and 0.001 , e.g., between 0.0006 and 0.001 , e.g., between 0.0006 and 0.0008.

[0087] The improved electrical properties (e.g., low dielectric constant and low dissipation factor) of the flexible laminate 100 make it possible for designers to realize improvements in insertion loss, e.g., of up to 25% or more for a given characteristic impedance versus incumbent flexible materials. It is believed that low levels of ferromagnetic elements (e.g., Fe, Ni, or Co) in the conductive cladding 104 (e.g., in the copper foil) can help achieve low insertion loss.

[0088] The coefficient of thermal expansion (CTE) of the dielectric substrate 102 and the CTE of the conductive cladding 104 are similar in the x-y plane of the flexible laminate 100. For instance, when the conductive cladding 104 is a copper foil, the CTE of the in the x-y plane of the dielectric substrate 102 can be between 5 and 25 ppm/°C, e.g., between 16 and 22 ppm/°C, e.g., between 14 and 20 ppm/°C. The matching of CTE values between the dielectric substrate 102 and the conductive cladding 104 provides the flexible laminate 100 with dimensional stability, e.g., a dimensional stability of less than about 0.1 %, e.g., such that the flexible laminate maintains its original dimensions within about 0.1 % when subjected to removal of the conductive cladding and a change in temperature.

[0089] The conductive cladding 104 of the flexible laminate 100 is adhered strongly to the dielectric substrate. For instance, a peel strength between the dielectric substrate 102 and the conductive cladding 104 is greater than

2 Ib./inch, e.g., greater than 4 lb. /inch, e.g., between 2 and 20 Ib./inch or between 4 and 20 Ib./inch. The flexible laminate 100 is mechanically robust against bending and can be flexed over bend radii typically found in electronic devices without failure of any of the components of the flexible laminate 100. This flexibility facilitates installation of the flexible laminate 100 into devices.

[0090] The flexible laminate 100 can be drilled by a UV laser and is compatible with metallization techniques, e.g., plasma metallization, such that through-holes can be formed through the thickness of the flexible laminate 100 (e.g., along the z-axis of the flexible laminate 100). The dielectric substrate 102 of the flexible laminate 100 has a solder float resistance at 288 °C of at least 5 seconds, at least 10 seconds, at least 30 seconds, or at least 60 seconds, e.g., between 5 and 20 seconds, between 10 and 15 seconds, between 10 and 30 seconds, between 10 and 60 seconds, or between 30 and 60 seconds.

[0091] The flexible laminate 100 can be used for a printed-wiring board, e.g., for flexible printed circuit board antennas. For instance, the dimensions and electrical properties of the flexible laminate 100 can make the flexible laminate 100 suitable for use in high-frequency applications, such as for antennas for mobile devices usable on 5G communications networks, as discussed further below, or for use with automotive radar or other high-frequency applications. In some examples, multiple flexible laminates 100 can themselves be laminated into a multilayer circuit board structure. The flexible laminate is substantially void-free and resistant to formation of conductive anodic filaments, which contributes to electrical reliability of the flexible laminate as printed-wiring board substrate.

[0092] The low dielectric constant and low dissipation factor of the dielectric substrate 102 of the flexible laminate 100 are due, at least in part, to the composition of the perfluorocopolymer matrix 110. The perfluorocopolymer matrix 110 includes a fluorinated perfluorocopolymer, such as a fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer; and a non-fluorinated perfluorocopolymer, such as a non-fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer. The fluorinated perfluorocopolymer, the non-fluorinated perfluorocopolymer, or both can be straight-chain, unbranched polymers. The fluorinated perfluorocopolymer has a low or zero polarity, and thus has a low dielectric constant and a low dissipation factor. However, fluorinated perfluorocopolymers are generally non-reactive, e.g., the fluorinated copolymer has poor adhesion to the L-glass fabric 108 and the conductive cladding 104. The non-fluorinated perfluorocopolymer has reactive end groups (e.g., carboxyl or amide end groups) that are attracted to the L-glass fabric 108 and the conductive cladding 104. The presence of these reactive end groups promotes adhesion between the perfluorocopolymer matrix and the L-glass fabric 108 and the conductive cladding 104.

[0093] In some examples, the perfluorocopolymers are made by aqueous dispersion polymerization, and as-polymerized can contain at least about 400 reactive end groups per 10⁶ carbon atoms. Most of these end groups are thermally unstable in the sense that when exposed to heat, such as encountered during extrusion and film formation, or film lamination conditions, they can undergo chemical reaction such as decomposition and decarboxylation, either discoloring the extruded polymer or filling it with non-uniform bubbles or both. To make the fluorinated perfluorocopolymers described here, polymerized perfluorocopolymer is stabilized to replace substantially all of the reactive end groups by thermally stable -CF3 end groups. An example method of stabilization is exposure of the fluoropolymer to a fluorinating agent, such as elemental fluorine, for example by processes as disclosed in U.S. Pat. No. 4,742,122 and U.S. Pat. No. 4,743,658, the contents of which are incorporated here by reference in their entirety.

[0094] Non-fluorinated perfluorocopolymers typically have a higher dissipation factor than fluorinated perfluorocopolymers. The composition of the perfluorocopolymer matrix 110 can be tailored to achieve both a sufficiently low dielectric constant and low dissipation factor for the dielectric substrate 102 and sufficient adhesion to the L-glass fabric 108 and the conductive cladding 104. For instance, the composition of the perfluorocopolymer matrix 110 can be tailored to provide as much fluorinated copolymer as possible while still maintaining sufficient adhesion to the L-glass fabric 108 and the conductive cladding 104. A sufficiently low dielectric constant for the dielectric substrate 102 is a dielectric constant at 10 GHz of less than about 2.7, e.g., between 2.1 and 2.7, e.g., between 2.1 and 2.4. A sufficiently low dissipation factor for the dielectric substrate 102 is a dissipation factor at 10 GHz of less than 0.0015, such as between 0.0002 and 0.001 , e.g., between 0.0006 to 0.001 , e.g., between 0.0006 and 0.0008. In some examples, the sufficiency of the adhesion between the perfluorocopolymer matrix 110 and the L-glass fabric 108 and the conductive cladding 104 is determined by the peel strength between the dielectric substrate 102 and the conductive cladding 104. For instance, the adhesion is sufficient if the peel strength is greater than 2 Ib./inch, e.g., greater than 4 lb. /inch, e.g., between 2 and 20 Ib./inch or between 4 and 20 Ib./inch. In some examples, the sufficiency of the adhesion between the perfluorocopolymer matrix 110 and the L-glass fabric 108 and the conductive cladding 104 is determined by the tendency of the flexible laminate 100 to resist formation of conductive anodic filaments (CAF), discussed further below.

[0095] In some examples, the composition of the perfluorocopolymer matrix 110 is indicated by a ratio (e.g. , a weight or volume ratio) of fluorinated perfluorocopolymer to non-fluorinated perfluorocopolymer. The weight percentage of fluorinated perfluorocopolymer can be between 50% and 90%, such as between 50% and 80%, e.g., 50%, 60%, 70%, 75%, 80%, or 90%; and the weight percentage of non-fluorinated perfluorocopolymer can be between 10% and 50%, e.g., 10%, 20%, 25%, 30%, 40%, or 50%.

[0096] In some examples, the composition of the perfluorocopolymer matrix 110 is indicated by a number (e.g., a number concentration) of carboxyl end groups, present in the perfluorocopolymer matrix 110. Non-limiting examples of such carboxyl end groups include -COF, -CONH2, -CO2CH3, and -CO2H and are determined by polymerization aspects such as choice of polymerization medium, initiator, chain transfer agent, if any, and buffer if any. The number of carboxyl end groups per million carbon atoms present in the perfluorocopolymer matrix 100 can be between 30 and 70, e.g., between 35 and 65. This number of carboxyl end groups can be selected to achieve sufficient adhesion between the perfluorocopolymer matrix 110 and the L-glass fabric 108 and the conductive cladding 104 while also achieving a sufficiently low dielectric constant and dissipation factor. For instance, the number of carboxyl end groups can be selected such that there is no CAF formation in the flexible laminate 100. In some examples, the composition of the fluorinated perfluorocopolymer and the non-fluorinated perfluorocopolymer are indicated by a number (e.g., a number concentration) of carboxyl end groups present in each type of perfluorocopolymer. The fluorinated perfluorocopolymer can have less than 10 carboxyl end groups per million carbon atoms, e.g., 5 or fewer, or 1 or fewer, or fewer than 1 carboxyl end groups per million carbon atoms. The non-fluorinated perfluorocopolymer can have between 100 and 300 carboxyl end groups per million carbon atoms, e.g., between 120 and 280 or between 150 and 250 carboxyl end groups per million carbon atoms. The analysis and quantification of carboxyl end groups in perfluorocopolymers can be carried out by infrared spectroscopy methods, such as described in U.S. Pat. No. 3,085,083, U.S. Pat. No. 4,742,122 and U.S. Pat. No. 4,743,658, the contents of all of which are incorporated here by reference in their entirety. The presence of the thermally stable end group -CF3 (the product of fluorination) is deduced from the absence of unstable end groups existing after the fluorine treatment. The presence of - CF3 end groups results in reduced dissipation factor of the perfluorocopolymer as compared to other end groups

[0097] The melt flow rate (MFR) of the fluorinated perfluorocopolymer, the non-fluorinated perfluorocopolymer, or both also can affect the adhesion between the perfluorocopolymer matrix 110 and the L-glass fabric 108 and the conductive cladding 104. A polymer with a high MFR flows more readily during lamination of the flexible laminate 100 than can a polymer with a lower MFR. The flow of the perfluorocopolymer matrix 110 during the lamination process (discussed in more detail below) enables the perfluorocopolymer matrix 110 to fully encapsulate the fibers of the L-glass fabric 108, resulting in a dielectric substrate 102 that is substantially free of voids, e.g. , non-porous. A void-free dielectric substrate 102 is resistant to CAF formation. For instance, the MFR of the fluorinated perfluorocopolymer can be between 1 and 40 g/10 minutes, e.g., between 2 and 15 g/10 minutes, e.g., 2 g/10 minutes, 4 g/10 minutes, 6 g/10 minutes, 8 g/10 minutes, 10 g/10 minutes, 12 g/10 minutes, 14 g/10 minutes, 16 g/10 minutes, 18 g/10 minutes, 20 g/10 minutes, 25 g/10 minutes, 30 g/10 minutes, 35 g/10 minutes, or 40 g/10 minutes,. The MFR of the non-fluorinated perfluorocopolymer can be between 1 and 40 g/10 minutes, e.g., between 2 and 20 g/10 minutes, e.g., 2 g/10 minutes, 5 g/10 minutes, 10 g/10 minutes, 15 g/10 minutes, or 20 g/10 minutes. The fluorinated and non-fluorinated perfluorocopolymers can be provided in a ratio that results in an overall MFR for the perfluorocopolymer matrix of between 10 and 30 g/10 minutes, e.g., 10 g/10 minutes, 15 g/10 minutes, 18 g/10 minutes, 21 g/10 minutes, 24 g/10 minutes, 27 g/10 minutes, or 30 g/10 minutes.

[0098] Suitable materials for the fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) perfluorocopolymer include a Teflon™ perfluoroalkane (PFA) 416HP with an MFR of about 40 g/10 minutes or a Teflon™ PFA 440HP (A/B) with an MFR of about 16 g/10 minutes or 14 g/10 minutes, respectively (The Chemours Company, Wilmington, DE). Suitable materials for the non-fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) include a Teflon™ PFA 316 with an MFR of about 40 g/10 minutes or a Teflon™ PFA 340 with an MFR of about 14 g/10 minutes (Chemours).

[0099] The fluorinated perfluorocopolymer, the non-fluorinated perfluorocopolymer, or both, have a high melting point, such as between 250 °C and 350 °C, e.g., between 280 °C and 320 °C, between 290 °C and 310 °C, e.g., about 305 °C. The high melting point of the fluorinated perfluorocopolymer, the non-fluorinated perfluorocopolymer, or both results in the perfluorocopolymer matrix 100 being resistant to high temperatures and provides the dielectric substrate 102 with a sufficient solder float resistance, such as a solder float resistance at 288 °C of at least 5 seconds, at least 10 seconds, at least 30 seconds, or at least 60 seconds, e.g., between 5 and 20 seconds, between 10 and 15 seconds, between 10 and 30 seconds, between 10 and 60 seconds, or between 30 and 60 seconds, as measured according to the IPC-TM-650 test method.

[0100] The composition of the perfluorocopolymer matrix 110 can be selected to enable the dielectric substrate 102 to be compatible with plasma treatment, e.g., for metallization of through-holes formed through the thickness of the flexible laminate 100. [0101] Specific examples of fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymers that are suitable for inclusion in the perfluorocopolymer matrix 100 include a Teflon™ perfluoroalkane (PFA) 416HP with an MFR of about 40 g/10 minutes or a Teflon™ PFA 440HP with an MFR of about 14 g/10 minutes (The Chemours Company, Wilmington, DE). Specific examples of nonfluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymers that are suitable for inclusion in the perfluorocopolymer matrix 100 include a Teflon™ PFA 316 with an MFR of about 40 g/10 minutes or a Teflon™ PFA 340 with an MFR of about 14 g/10 minutes (The Chemours Company) .

[0102] In some examples, the perfluorocopolymer matrix 100 is formed of a single type of perfluorocopolymer having both fluorinated end groups and reactive end groups (e.g., rather than a mixture of a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer). The ratio of fluorinated end groups to reactive end groups in the single type of perfluorocopolymer is selected to achieve both sufficient adhesion between the perfluorocopolymer matrix 110 and the L-glass fabric 108 and a sufficiently low dielectric constant and dissipation factor.

[0103] The presence of the woven L-glass fabric 108 enables the CTE of the dielectric substrate 102 to be matched to the CTE of the metal foil 104. The woven L-glass fabric 108 that is embedded in the perfluorocopolymer matrix 110 is formed of spread glass (e.g., L-glass) bundles.

[0104] The composition of L-glass is shown in Table 1 . The composition of E-glass is also shown for comparison. L-glass has a lower CTE than the perfluorocopolymer matrix 110, such as a CTE of between 2.5 ppm/°C and 4 ppm/°C, e.g., between 2.5 ppm/°C and 3 ppm/°C or between 3 ppm/°C and 4 ppm/°C. By adjusting the ratio of the perfluorocopolymer matrix 110 to the woven glass fabric 108, the CTE of the dielectric substrate 102 in the x-y plane can be matched to the in-plane CTE of the metal foil 104, thereby providing the flexible laminate 100 with dimensional stability. For instance, the dielectric substrate 102 can include between 5 and 20 volume percent of woven L-glass fabric 108 and between 80 and 95 volume percent of the perfluorocopolymer matrix 110 to the woven glass fabric 108. The CTE in the x-y plane of the dielectric substrate 102 can be between 5 and 25 ppm/°C, e.g., between 16 and 22 ppm/°C, e.g., between 14 and 20 ppm/°C, thereby providing a dimensional stability of less than about 0.1 %. By contrast, the CTE of the perfluorocopolymer matrix 110 alone can be between 100 and 300 ppm/°C.

Table 1 . Composition of L-glass

[0105] L-glass has a low dielectric constant, such as a dielectric constant of between 4.0 and 5.0 at 10 GHz, e.g., between 4.5 and 5.0 or between 4.5 and 4.8. Thus, the dielectric substrate 102 has a low dielectric constant and low loss even with the presence of the L-glass fabric embedded in the perfluorocopolymer matrix. L-glass also has a low dissipation factor, such as a dissipation factor of between 0.002 and 0.003 at 10 GHz, e.g., 0.002, 0.0023, 0.0025, 0.0028, or 0.003.

[0106] The woven L-glass fabric 108 has a thickness of less than about 100 pm, e.g., between about 30 pm and 100 pm or between 10 pm and 30 pm, helping a thin dielectric substrate 102 to be achieved. The basis weight of the quartz fabric 108 is less than about 1000 g/m², e.g., less than about 50 g/m², e.g., between 10 g/m² and 50 g/m². In a specific example, the L-glass fabric 108 is an NL1035 NL-glass fabric (Asahi Kasei Corporation, Tokyo, Japan).. [0107] In some examples, the woven L-glass fabric 108 is subjected to one or more surface treatments to improve the wettability of the fibers of the woven L- glass fabric 108 by the perfluorocopolymer matrix 110, to remove residual organic matter, or to mechanically alter the surface of the fibers to enhance adhesion between the fibers of the L-glass fabric 108 and the perfluorocopolymer matrix 110.. The objective of the surface treatment can be to facilitate substantially complete wetting of the L-glass fibers by the perfluorocopolymer such that the perfluorocopolymer fully encapsulates the L-glass fiber (e.g., L- glass yarn) bundles. Sufficient encapsulation of and adhesion to the L-glass fiber bundles by the perfluorocopolymer enables the dielectric substrate 102 to be substantially free of voids, e.g., non-porous, which in turn helps prevent formation of conductive anodic filaments and occurrence of electromigration during postprocessing, e.g., during formation of vias through the thickness of the flexible laminate 100.

[0108] The surface treatment can include a thermal treatment to remove residual organic matter (e.g., residual starches) from the surface of the L-glass fibers such that a clean L-glass surface is exposed to the perfluorocopolymer. The surface treatment can include the addition of adhesion promotors such as methacrylate silane, aminosilane, or fluorosilane on the surface of the L-glass fibers. The surface treatment can include a plasma or corona treatment. The surface treatment can include treatment with a polymeric coating, such as a fluoropolymer, e.g., a perfluoroalkane (PFA), fluorinated ethylene propylene (FEP), or Teflon™ amorphous fluoropolymer, to form a polymer (e.g., fluoropolymer) film on the surface of the L-glass fibers. For instance, the L-glass fabric can be immersed in a solution containing a dispersion of the fluoropolymer to form a monolayer of the fluoropolymer on the surface of the L-glass fibers. The surface treatment can include treatment with a fluorinated silane to form a layer, e.g., a monolayer, of fluorinated molecules on the surface of the L-glass fibers. A combination of surface treatments can be applied, such as a thermal treatment followed by a plasma or corona treatment. The surface treatment(s) applied to the L-glass fabric 108 can improve wettability of the fibers by the perfluorocopolymer matrix 110, enabling better encapsulation of the fibers of the L-glass fabric 108 by the perfluorocopolymer matrix 110 and stronger adhesion between the perfluorocopolymer matrix 110 and the fibers of the L-glass fabric 108, thereby contributing to formation of a void-free dielectric substrate 102 that is resistant to CAF formation.

[0109] The wettability of the L-glass fabric can be characterized by the water contact angle (WCA). The woven L-glass fabric following surface treatment can have a WCA of between 0° and 60°.

[0110] In some examples, the lamination structure can be designed to achieve good encapsulation of the L-glass fabric, e.g., in addition to or instead of application of a surface treatment to the L-glass fabric. Referring to Fig. 2, an example metal-clad, flexible laminate can be fabricated by laminating a set of layers 150. The set of layers includes multiple layers of fluoropolymer films, including a non-fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) layer 162a, 162b disposed on either side of a L-glass fabric 108, and a perfluorocopolymer layer 164a, 164b that includes a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer disposed on the exterior-facing side of each non-fluorinated layer 162. A conductive cladding, such as the metal (e.g., copper) foil 104a, 104b described above), is disposed on both exterior sides of the set of layers 150. When the structure shown in Fig. 2 is laminated to produce a flexible laminate (see below for further discussion of lamination processes), the non-fluorinated layer 162 encapsulates the L-glass fabric 108 such that the non-fluorinated layers 162 and the perfluorocopolymer layer 164 form a matrix in which the L-glass fabric 108 is embedded, e.g., form a dielectric substrate for the flexible laminate.

[0111] Referring again to Fig. 1 , the additive material 112 is dispersed, e.g., homogeneously dispersed, in the perfluorocopolymer matrix 110. The additive material 112 is a material that is capable of absorbing UV light such that the flexible laminate 100 can be processed by UV drilling processes, e.g., to form vias between the top and bottom surfaces 106 of the flexible laminate 100. The additive material 112 is present in the dielectric substrate 102 at a volume percentage of less than 2%, e.g., between 1 and 2 volume percent, e.g., 1 vol.%, 1 .25 vol.%, 1 .5 vol.%, or 2 vol.%. The additive material 112 can be a material that has a relatively low dielectric constant, e.g., a dielectric constant of between 10 and 1000, so that the inclusion of the additive material 112 in the perfluorocopolymer matrix 110 does not significantly increase the dielectric constant or dissipation factor of the dielectric substrate 102. For instance, the inclusion of the additive material 112 at less than 2% by volume can cause the dielectric constant of the dielectric substrate 102 to increase by less than 10%, e.g., less than 5% or less than 2%.

[0112] In some examples, the additive material 112 is inorganic particles, e.g., particles of cerium oxide (CeCh), titanium dioxide (TiC>2), silicon dioxide (SiC>2), barium titanate (BaTiOs), calcium titanate (CaTiOs), zinc oxide (ZnO), or other suitable materials. The particles can have a diameter of less than about 5 pm, less than about 2 pm, less than about 1 pm, or less than about 0.5 pm, e.g., between 0.1 pm and 0.5 pm. For instance, smaller particles often are more effective absorbers of UV light than larger particles of similar composition. In some examples, the additive material 112 is an organic (e.g., polymeric) additive, such as a low loss thermoset material such as polyimide, that is blended into the perfluorocopolymer matrix 110. In some examples, both inorganic particles and an organic additive are used as additive materials.

[0113] The copper foil 104 of the flexible laminate 100 provides a platform on which conductive patterns can be defined, e.g., such that the flexible laminate 100 can be used as a printed-wiring board. In some examples, the copper foil 104 is disposed on the surface(s) 106 of the dielectric substrate 102 by a mechanical process, e.g., a roll-to-roll lamination process. For instance, the copper foil can be an electrodeposited copper foil or a rolled copper foil. In some examples, the copper foil 104 is deposited, e.g., electrolytically plated onto the dielectric substrate 102. [0114] The copper foil 104 has a thickness of less than about 72 pm, e.g., less than about 18 pm, e.g., between 10 pm and 18 pm. The copper foil 104 has a low root mean square (RMS) roughness, such as an RMS roughness of less than 1 pm, e.g., less than 0.5 pm, as measured by non-contact interferometry. The low RMS roughness of the copper foil 104 helps to maintain the low insertion loss of the circuitry made from the flexible laminate 100. In some examples, the RMS roughness of the copper foil 104 is selected to balance low insertion loss (e.g., achievable by a low RMS roughness) with good adhesion between the copper foil 104 and the dielectric substrate 102 (e.g., achievable by higher RMS roughness). For instance, as discussed above, a sufficiently high peel strength between the dielectric substrate 102 and the copper foil 104 is a peel strength that is greater than 2 lb. /inch, e.g., greater than 4 Ib./inch, e.g., between 2 and 20 lb. /inch or between 4 and 20 Ib./inch.

[0115] The copper foil 104 has a purity of at least about 99.9%. The surface chemistry of the copper foil 104 can be affected by surface treatments such as treatment with zinc, thermal stability additives, and treatments to resist oxidation. These surface treatments can be applied to one or both surfaces of the copper foil 104. Elements such as iron and zinc have been found to be effective in enhancing the peel strength without appreciably degrading the electrical performance of the substrate.

[0116] As discussed above, the dielectric substrate 102 of the flexible laminate 100 is substantially free of voids and has sufficient adhesion between the perfluorocopolymer matrix 110 and the L-glass fabric 108, which enables the flexible laminate to resist formation of conductive anodic filaments (CAF). CAF are metallic filaments that form, e.g., in voids or weak areas of a dielectric substrate due to electromigration of metal induced by, e.g., application of an electric field. CAF formation can lead to electric failure, e.g., when the CAF create short-circuit pathways between vias through the printed-wiring board. A flexible laminate can be considered as having no CAF formation when there is less than a one decade drop in resistance throughout the duration of a test a resistance of greater than 10 MOhms after an initial 96 hour equilibration period. A CAF test can last up to 1000 hours or more with applied voltages of between 100 VDC and 1000 VDC, e.g., depending on application criteria.

[0117] An example of CAF formation is shown in Fig. 3A. Fig. 3A shows a hypothetical laminate 200 having a dielectric matrix 202 with glass fibers 204 embedded therein. Through holes (also sometimes referred to as vias) 206 are formed through the thickness of the laminate 200 and plated with a metal 208, e.g., copper. Application of an electric field causes the metal 208 to anodically dissolve, migrate, and redeposit in the dielectric matrix 202, e.g., at interfaces between the dielectric matrix 202 and the glass fibers 204, forming filaments 210 that extend between adjacent vias 206.

[0118] Fig. 3B shows another example of CAF formation in a hypothetical laminate 250 having a dielectric matrix 252 with glass fibers 254 embedded therein and a conductor pattern 262, e.g., a copper pattern, defined on the top, bottom, and interior surfaces of the laminate 250. Filaments 260 of metal, e.g., copper, form at interfaces between the conductor pattern 262 and the glass fibers 254.

[0119] Referring again to Fig. 1 , the dielectric substrate 102 of the flexible laminate is substantially void-free and has strong adhesion between the perfluorocopolymer matrix 110 and the L-glass fabric 108. This is achieved, e.g., by the nature of the perfluorocopolymer (e.g., the number concentration of reactive end groups), the surface chemistry of the L-glass fabric, and manufacturing parameters such as pressure and temperature (discussed below). In addition, the arrangement of the L-glass fabric 108 in the perfluorocopolymer matrix 110 is such that there is substantially no contact between fibers of the fabric and the conductive cladding 104. As a result, CAF formation in the dielectric substrate 102 is minimal and the flexible laminate 100 can be used a reliable and robust printed-wiring board substrate.

[0120] Referring to Fig. 4, a multilayer printed-wiring board 300 can be formed from multiple of the flexible laminates 100 described above. In the example of Fig. 4, the multilayer printed-wiring board 300 includes two flexible laminates 100a, 100b connected by an adhesive layer 302. Vias (also referred to as through-holes; not shown) can be defined through all or a portion of the thickness of the multilayer printed-wiring board, e.g., by UV drilling, with the UV energy being absorbed by the additive material in the dielectric substrate of the flexible laminate 100. The vias can be plated with a metal, such as a copper film. The adhesive layer 302 can be, e.g., an adhesive that can be bonded at a temperature below the melting point of the perfluorocopolymer matrix of the flexible laminate 100. In some examples, the adhesive is a thermoplastic adhesive that is capable of being bonded at a temperature between 0 °C and 50 °C less than the melting point of the perfluorocopolymer matrix. In some examples, the adhesive is a thermoset adhesive that is capable of being bonding at a temperature of between 0 °C and 200 °C less than the melting point of the perfluorocopolymer matrix, e.g., at temperatures between 150 °C and 250 °C.

[0121] Referring to Fig. 5, multiple (here, three) flexible laminates 100 are laminated together to form a multi-layer printed-wiring board 400. A central flexible laminate 100c includes top and bottom conductive claddings. Flexible laminates 10Od, 100e each includes a single conductive cladding. The flexible laminates 100c, 100d are bonded to the central flexible laminate 100e by adhesive layers 402a, 402b, respectively. The adhesive layers 402a, 402b can be, e.g., an adhesive that can be bonded at a temperature below the melting point of the perfluorocopolymer matrix of the flexible laminates 100. In some examples, the adhesive is a thermoplastic adhesive that is capable of being bonded at a temperature between 0 °C and 50 °C less than the melting point of the perfluorocopolymer matrix. In some examples, the adhesive is a thermoset adhesive that is capable of being bonding at a temperature of between 0 °C and 200 °C less than the melting point of the perfluorocopolymer matrix.

[0122] Vias (not shown) can be defined through all or a portion of the thickness of the multilayer printed-wiring board 400, e.g., by UV drilling.

[0123] Printed-wiring boards made from the flexible laminates 100 described here can be used in various applications, e.g., high-frequency applications such as high-frequency communications applications. For instance, referring to Fig. 6, a printed-wiring board 502 including one or more flexible laminates can be used for an antenna or antenna feedline for a communication device 500 (e.g., a mobile communication devices) operable on a 5G communications network. For instance, flexible laminates can be useful as substrates for printed-wiring boards for communication device antennas or antenna feed lines to connect electronic components of the device that are located on different planes. A printed-wiring board 504 including one or more flexible laminates can be used in communications network equipment, such as in a transmission antenna in a tower 508 of a cellular communications network. Printed-wiring boards including flexible laminates can also be used in other applications, such as in camera feedlines in mobile computing devices.

[0124] The flexible laminates described here can be manufactured by lamination processes. Referring to Fig. 7, in an example, the L-glass fabric 108 is disposed between two perfluorocopolymer films 120a, 120b. Each perfluorocopolymer film 120a, 120b has a thickness of between 10 pm and 100 pm, e.g., between 10 pm and 80 pm, between 10 pm and 60 pm, or between 20 pm and 50 pm. The conductive claddings 104a, 104b are disposed on respectively perfluorocopolymer film 120a, 120b. For example, the conductive claddings 104 are electrodeposited copper foils or rolled annealed copper foils. Each conductive cladding 104a, 104b has a thickness of less than about 72 pm, e.g., less than about 18 pm, e.g., between 10 pm and 18 pm.

[0125] The layers of material 104, 108, 120 are heated and compressed to consolidate the layers of the material, thereby forming the flexible laminate 100. In some examples, the L-glass fabric 108 and the two perfluorocopolymer films 120a, 120b are laminated to form the dielectric substrate and the conductive cladding (e.g., copper foils) are electrodeposited onto the dielectric substrate in a second processing step.

[0126] The parameters of the lamination process (e.g., temperature, time, and pressure) are selected to achieve a target viscosity of the perfluorocopolymer that enables the perfluorocopolymer to flow, thereby wetting and encapsulating the glass bundles of the L-glass fabric 108 and enabling good adhesion between the perfluorocopolymer and the conductive claddings 104. For instance, the process parameters are selected such that the perfluorocopolymer reaches a zero shear viscosity of between 2000 Pa-s and 5000 PA-s at 330 °C. The temperature can be greater than the melting point of the perfluorocopolymer, e.g., between 10 °C and 30 °C higher than then the melting point of the perfluorocopolymer. For instance, the temperature can be between 300 °C and 400 °C, e.g., between 320 °C and 330 °C, e.g., 300 °C, 320 °C, 340 °C, 360 °C, 380 °C, or 400 °C. The temperature ramp rate can be between 1 and 5 °C/minute, e.g., 1 °C/minute, 2°C/minute, 3°C/minute, 4°C/minute, or °C/minute. The pressure applied to the layers of material can be between 100 psi and 1000 psi, e.g., between 200 psi and 1000 psi or between 600 psi and 1000 psi. The dwell time (e.g., for a static lamination process) can be between 30 minutes and 120 minutes, e.g., 30 minutes, 60 minutes, 90 minutes, or 120 minutes.

[0127] Fig. 7 depicts an isobaric roll-to-roll lamination process using a set of rollers 600. In some examples, the roll-to-roll lamination process is an isochoric, gap-controlled lamination process. In some examples, the lamination process is a static lamination process in which the layers of material are pressed between heated platens.

[0128] The perfluorocopolymer films 120 are formed by, e.g., melt processing and extrusion. In some examples, the additive material is mixed into melted fluorinated perfluorocopolymer, and the mixture of fluorinated copolymer and additive material is mixed with melted non-fluorinated perfluorocopolymer. In some examples, the additive material is mixed into melted non-fluorinated perfluorocopolymer, and the mixture of non-fluorinated perfluorocopolymer and additive material is mixed with melted fluorinated perfluorocopolymer. The resulting perfluorocopolymer mixture is extruded to form the perfluorocopolymer films. Mixing the additive material with the non-fluorinated perfluorocopolymer helps with integration and dispersion of the additive material throughout the perfluorocopolymer film.

[0129] Fig. 8 is a flow chart of an example process for making the flexible laminate 100. An additive material that is capable of absorbing ultraviolet light is dispersed in a non-fluorinated perfluorocopolymer, such as a non-fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) perfluorocopolymer (700). The additive material is, e.g., particles of cerium oxide, titanium dioxide, silicon dioxide, barium titanate, calcium titanate, or zinc oxide; or a polymeric additive such as a polyimide. The non-fluorinated perfluorocopolymer with the dispersed additive material is mixed with a fluorinated perfluorocopolymer, such as a fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) perfluorocopolymer (702), to form a perfluorocopolymer mixture. The perfluorocopolymer mixture is melt processed and extruded to form perfluorocopolymer films (704).

[0130] A woven L-glass fabric is exposed to a surface treatment, such as heat treatment, corona or plasma treatment, or formation of a coating on the surface of the fibers of the L-glass fabric (706). Copper foils, e.g., electrodeposited copper foils or rolled annealed copper foils, are also exposed to a surface treatment, such as heat treatment, corona or plasma treatment, or deposition of adhesion promoters or thermal stability additives (708).

[0131] A layered stack of materials is formed (710) including the treated L- glass fabric disposed between two perfluorocopolymer films, with a treated conductive cladding on both the top and the bottom of the stack. The layered stack of materials is laminated by application of heat and pressure to form a flexible laminate (712), e.g., in a static lamination process or a roll-to-roll lamination process.

Examples

[0132] The following polymers and polymer dispersions are used in these examples. [0133] PFA1 : Teflon™ PFA 440HP (A/B) (Chemours), a high purity fluorinated perfluoroalkoxy (PFA) melt processable resin having an MFR of 16 g/10 min (for “A”) and 14 g/10 min (for “B).

[0134] PFA2: Teflon™ PFA 340 (Chemours), a general purpose nonfluorinated PFA melt processable resin having an MFR of 14 g/10 min.

[0135] PFA3: Teflon™ PFA 416HP (Chemours), high purity fluorinated PFA melt processable resin having an MFR of 40 g/10 min.

[0136] Example 1 : Mechanical characterization of flexible copper clad laminates with L-glass or quartz fabric

[0137] Experiments were performed to investigate the thickness, flatness, and dimensional stability of copper clad laminates incorporating L-glass fabrics and quartz fabrics. PFA films were combined with either NL1035 NL-glass fabric from Asahi or 1027C-04 quartz fabric from Shin-Etsu and 12 pm thick BHFX- P92F-HG rolled copper foil from JX Nippon Mining & Metals Corporation (Tokyo, Japan) to form flexible copper clad laminates. The PFA films were composed of 50 wt.% PFA1 , 25% wt.PFA2, and 22.5 wt.% PFA3, with 2.5 wt.% of TiO2 particles (50.63 vol.% PFA1 , 25.31 % vol.PFA2, and 22.78 vol.% PFA3, with 1.28 vol.% of TiO2 particles), treated on both sides of the film with corona treatment. Materials were laminated in a hot oil vacuum press at a peak temperature of 320 °C and a pressure of 200 psi.

[0138] The details of the experimental configuration including materials used are shown in Table 2. The five values in the "Construction" column refer to the thickness of the copper cladding on each side of the laminate (12 pm in this example), the thickness of the perfluorocopolymer films used to create the laminate (54 pm in this example), and type of fabric (NL1035 L-glass or 1035 quartz glass fabric in this example). Materials were laminated in a hot oil vacuum press at a dwell temperature of 320 °C and a pressure of 200 psi, with a dwell time of 60 minutes, a vacuum of 1 atm, and a ramp rate of 2 °C/minute. Prior to testing, samples were allowed to equilibrate at 23 °C and 50% relative humidity for 24 hours.

Table 2. Experimental details.

[0139] The laminates are shown in the photograph of Fig. 9. The flatness of each laminate was characterized visually. As can be seen from Fig. 9, laminates including L-glass fabric are flatter than laminates including quartz fabric.

[0140] The thickness of each laminate was measured after etch, according to the IPC TM-650 2.2.18 test method, and the results are shown in Fig. 10.

Generally, L-glass laminates are thicker than quartz glass laminates. Thickness and estimated squeeze out results are shown in Table 3. Estimated squeeze-out is measured by measuring the film flow distance from the edge of the laminate when squeezed. The resin content of each laminate is shown in Fig. 11 .

Table 3. Experimental test data for the experiments detailed in Table 2.

[0141] Dimensional stability results for laminates tested in machine direction (MD) and cross machine direction (CMD) are shown in Figs. 12A (tested according to IPC TM-650 2.2.4b) and 12B (testing performed according to IPC TM-650 2.2.4c). These results show lower dimensional stability values for L- glass laminates than for quartz glass laminates.

Example 2: Characterization of flexible copper clad laminates with L-qlass or quartz fabric

[0142] Additional experiments were performed to investigate the relationship between thickness and flatness and dimensional stability. PFA films of various types were combined with various types of glass fabrics, including 1017C-02, 1027C-04, 1035C-04, 1078C-04, or 2116C-04 quartz fabrics from Shin-Etsu, or NL1027, NL1035, NL-1078, or L2-1078 L-glass or NL-glass fabrics from Asahi. The PFA films and glass fabric were laminated with 12 pm thick BHFX-P92F-HG rolled copper foil from JX Nippon Mining & Metals Corporation to form flexible copper clad laminates. In some cases R101 titanium dioxide particles (Chemours) was added at a filler loading of 1 .25 vol.%. Materials were laminated in a hot oil vacuum press at a peak temperature of 320 °C and a pressure of 200 psi, with a dwell time of 60 minutes, a vacuum of 1 atm, and a ramp rate of 2 °C/min. • Various PFA films were tested, including the following:

• PFA film 1 , composed of 50 wt.% PFA1 , 25% wt.PFA2, and 22.5 wt.% PFA3, with 2.5 wt.% of TiC>2 particles (50.63 vol.% PFA1 , 25.31 % vol.PFA2, and 22.78 vol.% PFA3, with 1.28 vol.% of TiCh particles), treated on both sides of the film with corona treatment.

• PFA film 2, composed of 75 wt.% PFA3 and 25 wt.% PFA 2, mixed with

2.5 wt.% (1.25 vol. %) R101 TiO2 particles.

Table 4. Experimental details. [0143] The data obtained from these experiments are shown in Figs. 13-17. Fig. 13 is a plot of a visual characterization of the flatness of each laminate, with a score of 1 being the lowest (worst flatness) and 5 being the best (very flat).

Fig. 14 is a plot of the thickness of each laminate, measured after etch, according to the IPC TM-6502.2.18 test method. These results show that generally, thicker laminates are flatter than thinner laminates. Fig. 15 is a plot of the resin content of each laminate.

[0144] The dielectric constant and dissipation factor of each sample was also measured. The dielectric constant and dissipation factor were measured according to the IPC TM-650 2.5.5.13 test method, at 23 °C and 50% relative humidity. Results are shown in Figs. 16 and 17. Dimensional stability results according to methods B and C are shown in Figs. 18A and 18B.

[0145] These results show the effect of L-glass fabric versus quartz glass fabric on the dielectric constant and dissipation factor of the laminate, for the same resin content.

Example 3: Effect of end group content on copper clad laminates

[0146] The effects of end group content on copper clad laminate properties were evaluated by preparing PFA1 (fluorinated PFA) and PFA2 (non-fluorinated PFA) resins combined with R101 titania (Chemours) at various ratios of PFA2 to PFA1 . Mixtures of ~ 70 grams of resin were dry blended and then fed into a Rheometer Services Inc. System 10 batch mixer outfitted with a 60 cc volume mixing bowl containing roller blades. These blends were mixed at 150 rpm at 350 °C for 10 minutes to disperse all the components. The mixtures were then removed from the bowl and subsequently pressed into plaques at 350 °C that were ~ 100 mm x 100 mm by ~ 0.20 mm thickness for use in electrical testing and subsequent lamination. The pressed films were tested and found to have the electrical properties shown in Table 5:

Table 5. Electrical properties @ 10 GHz of molded PFA films having varying ratios of PFA2 to PFA1 .

[0147] As expected, the dielectric constant (Dk) remained fairly consistent with PFA2 loading and the dissipation factor (DF) rose in a linear fashion with increasing concentration of the PFA2 in the blend.

[0148] Measurements were also made to determine the total number of carboxyl end groups per 10⁶ carbon atoms for select blends and the results are shown in Table 6.

[0149] Table 6. End group level of PFA blends having varying 340 and 440 ratios

[0150] As with the dissipation factor data, the addition of the PFA2 to the blend was found to increase the amount of end groups measured in a generally linear fashion. A plot showing the measured dissipation factor as function of end group level is shown in Figure 19. This serves to show how the levels of end groups have a direct bearing on the measured electrical behavior of the blend films.

[0151] These blended PFA films were combined with NL2116 fabric (Asahi Kasei, Japan) and 35pm EXP-WS copper foil (Furukawa Electric Co., Ltd, Japan) and laminated at 320 °C and 400 psi in an electrically heated press (PHI, USA) for a dwell time of 60 minutes to form copper clad laminates. The experimental details are shown in Tables 7A and 7B.

Table 7A. Experimental details.

Table 7B. Experimental details.

[0152] The laminated materials were tested for various properties. These results are shown in Tables 8A and 8B.

Table 8A. Experimental test results for PFA2/PFA1 blending study.

Table 8B. Experimental test results for PFA2/PFA1 blending study.

[0153] It was found that there is a very good correlation between the total number of end groups per 10⁶ carbon atoms and dissipation factor and a suggested relationship between copper peel strength and end groups. These data can be seen in Figures 20 and 21 . Example 4: Sharpie wicking behavior of commercially available laminates

[0154] In a Sharpie wicking test, a hole is formed in the flexible laminate, a Sharpie® permanent marker is rubbed around the edge of the hole, and the hole is cleaned with isopropanol to remove excess ink. The radial distance away from the edge of the hole to which the ink was wicked is measured. Without being bound by theory, it is believed that this wicking test serves as an indicator of the adhesion between the fibers of the quartz fabric and the perfluorocopolymer matrix; poor adhesion or poor encapsulation leaves voids into which the ink can wick, resulting in a longer travel distance. By contrast, a substrate with good adhesion and good encapsulation will exhibit a low wicking distance.

[0155] Sharpie wicking test results for a laminate are predictive of the laminate’s performance under CAF testing. To demonstrate this association, commercially available materials known to have good CAF resistance were subjected to sharpie wicking tests. The results of these tests are shown in Table 9. These results indicate that sharpie wicking result of less than 0.5 mm corresponds to a material with good CAF resistance. It is believed that flexible copper clad laminates with L-glass exhibit a sharpie wicking of less than 1 mm.

Table 9. Sharpie wicking results of commercially available materials.

[0156] Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.

Claims

What is claimed is:

1 . A laminate article comprising: a dielectric substrate comprising: a perfluorocopolymer matrix comprising a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer; an L-glass fabric embedded in the perfluorocopolymer matrix; and an additive material dispersed in the perfluorocopolymer matrix, in which the additive material is capable of absorbing ultraviolet light; and a conductive cladding disposed on a surface of the dielectric substrate.

2. The laminate article of claim 1 , in which the L-glass fabric comprises yam of L-glass, N L-glass, or L2-glass.

3. The laminate article of claim 1 or 2, in which the laminate article has a thickness of between 20 pm and 200 pm.

4. The laminate article of claim 3, in which the thickness of the laminate article is between 30 pm and 90 pm.

5. The laminate article of claim 4, in which the thickness of the laminate article is between 30 pm and 60 pm.

6. The laminate article of any of the preceding claims, in which the dielectric substrate has a dielectric constant at 10 GHz of between 2.10 and 2.70.

7. The laminate article of claim 6, in which the dielectric constant of the dielectric substrate is between 2.10 and 2.40.

8. The laminate article of any of the preceding claims, in which the dielectric substrate has a thermal coefficient of dielectric constant with a value of between - 250 to +50 ppm/°C over a temperature range of 0 to 100 °C.

9. The laminate article of any of the preceding claims, in which the dielectric substrate has a dissipation factor at 10 GHz of less than 0.0015.

10. The laminate article of claim 9, in which the dielectric substrate has a dissipation factor at 10 GHz of between 0.0006 and 0.001 .

11 . The laminate article of claim 10, in which the dissipation factor of the dielectric substrate at 10 GHz is between 0.0006 and 0.0008.

12. The laminate article of any of the preceding claims, in which the laminate article has a planar shape defining an X-Y plane, and in which a coefficient of thermal expansion of the laminate article in the X-Y plane is between 5 and 25 ppm/°C.

13. The laminate article of claim 12, in which the coefficient of thermal expansion of the laminate article in the X-Y plane is between 14 and 20 ppm/°C.

14. The laminate article of claim 12, in which the coefficient of thermal expansion of the laminate article in the X-Y plane is between 16 and 22 ppm/°C.

15. The laminate article of any of the preceding claims, in which the fluorinated perfluorocopolymer comprises a fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer and in which the nonfluorinated perfluorocopolymer comprises a non-fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer.

16. The laminate article of any of the preceding claims, in which the perfluorocopolymer matrix comprises between 50 and 90 weight percent of the fluorinated perfluorocopolymer.

17. The laminate article of claim 16, in which the perfluorocopolymer matrix comprises between 10 and 50 weight percent of the non-fluorinated perfluorocopolymer.

18. The laminate article of any of the preceding claims, in which a number of carboxyl end groups per million carbon atoms in the perfluorocopolymer matrix is sufficient for the laminate article to form no conductive anodic filaments (CAF).

19. The laminate article of any of the preceding claims, in which a number of carboxyl end groups per million carbon atoms in the perfluorocopolymer matrix provides the laminate article with a peel strength between the dielectric substrate and the conductive cladding of greater than 2 Ib/inch.

20. The laminate article of any of the preceding claims, in which the number of carboxyl end groups per million carbon atoms in the perfluorocopolymer matrix is between 30 and 70.

21 . The laminate article of any of the preceding claims, in which the fluorinated perfluorocopolymer has 5 or fewer carboxyl end groups per million carbon atoms.

22. The laminate article of any of the preceding claims, in which the nonfluorinated perfluorocopolymer has between 100 and 300 carboxyl end groups per million carbon atoms.

23. The laminate article of any of the preceding claims, in which the perfluorocopolymer matrix has a melt flow rate (MFR) of between 10 g/10 minutes and 30 g/10 minutes.

24. The laminate article of any of the preceding claims, in which the perfluorocopolymer matrix has a solder float resistance of at least 10 seconds at 288 °C.

25. The laminate article of any of the preceding claims, in which the L-glass has a basis weight of less than 100 g/m²

26. The laminate article of claim 25, in which the basis weight of the L-glass fabric is less than 50 g/m².

27. The laminate article of any of the preceding claims, in which the L-glass fabric has a thickness between 10 pm and 100 pm.

28. The laminate article of claim 27, in which the L-glass fabric has a thickness between 10 pm and 30 pm.

29. The laminate article of any of the preceding claims, in which the L-glass fabric includes an aminosilane or methacrylate silane surface chemistry treatment.

30. The laminate article of any of the preceding claims, in which the L-glass fabric comprises a plasma-treated or corona-treated L-glass fabric.

31 . The laminate article of any of the preceding claims, in which the L-glass fabric is impregnated with a fluoropolymer.

32. The laminate article of any of the preceding claims, in which the L-glass fabric comprises a fluoropolymer coating.

33. The laminate article of any of the preceding claims, in which the L-glass fabric is pretreated with a fluoropolymer treatment prior to incorporation into the laminate article.

34. The laminate article of any of the preceding claims, in which the dielectric substrate comprises between 5 and 20 volume percent of the L-glass fabric and between 80 and 95 volume percent of the perfluorocopolymer matrix.

35. The laminate article of any of the preceding claims, in which a water contact angle of the L-glass fabric is between 0° and 60°.

36. The laminate article of any of the preceding claims, in which the additive material comprises inorganic particles.

37. The laminate article of claim 36, in which the inorganic particles comprise particles of cerium oxide, titanium dioxide, silicon dioxide, barium titanate, calcium titanate, or zinc oxide.

38. The laminate article of any of the preceding claims, in which the additive material comprises a thermoset polymer.

39. The laminate article of any of the preceding claims, in which the additive material is present in the perfluorocopolymer matrix at a volume percent of less than 2%.

40. The laminate article of any of the preceding claims, in which the additive material is dispersed homogeneously throughout the perfluorocopolymer matrix.

41 . The laminate article of any of the preceding claims, in which the conductive cladding is disposed on two opposing surfaces of the dielectric substrate.

42. The laminate article of any of the preceding claims, in which the conductive cladding comprises a copper foil.

43. The laminate article of claim 42, in which the copper foil is disposed on the surface of the dielectric substrate by a lamination process.

44. The laminate article of any of the preceding claims, in which the conductive cladding has a thickness of less than 72 pm.

45. The laminate article of claim 44, in which the thickness of the conductive cladding is between 5 pm and 18 pm.

46. The laminate article of any of the preceding claims, in which the conductive cladding has a root mean square (RMS) roughness of less than 1 pm.

47. The laminate article of claim 46, in which the RMS roughness of the conductive cladding is less than 0.5 pm.

48. A printed-wiring board comprising: the laminate article of any of the preceding claims, in which a conductor pattern is formed in the conductive cladding.

49. The printed-wiring board of claim 48, in which a through-hole is defined through a thickness of the laminate article; and comprising a copper film plating the through-hole.

50. A multilayer printed-wiring board comprising: a multilayer laminated structure comprising multiple printed-wiring boards according to claim 48 or 49.

51 . The multilayer printed-wiring board of claim 50, comprising a thermoplastic adhesive disposed between adjacent printed-wiring boards in the laminated structure.

52. The multilayer printed-wiring board of claim 51 , in which the thermoplastic adhesive was bonded at a temperature between 0 and 200 °C below a melting point of the perfluorocopolymer matrix.

53. The multilayer printed-wiring board of claim 52, in which the thermoplastic adhesive was bonded at temperatures between 0 and 50 °C below the melting point of the perfluorocopolymer matrix.

54. The multilayer printed-wiring board of claim 50, comprising a thermoset adhesive disposed between adjacent printed-wiring boards in the laminated structure.

55. The multilayer printed-wiring board of claim 54, in which the thermoset adhesive was cured at a temperature of between 150 °C and 250 °C.

56. The multilayer printed-wiring board of any of claims 5048 to 55, in which a through-hole is defined through at least a portion of the thickness of the multilayer printed-wiring board; and comprising a copper film plating the through- hole.

57. An antenna usable with a 5G communications network, the antenna comprising: a printed-wiring board according to any of claims 50 to 56.

58. A method of making a multilayer printed-wiring board, the method comprising: forming a conductor pattern in the conductive cladding of each of multiple of the laminate articles of claim 1 to form respective printed-wiring boards; and laminating the multiple printed-wiring boards to form a multilayer laminated structure.

59. The method of claim 58, in which laminating the multiple printed-wiring boards comprises adhering adjacent printed-wiring boards using a thermoplastic adhesive.

60. The method of claim 59, comprising bonding the thermoplastic adhesive at a temperature between 0 and 200 °C below a melting point of the perfluorocopolymer matrix.

61 . The method of claim 60, comprising bonding the thermoplastic adhesive at a temperature between 0 and 50 °C below the melting point of the perfluorocopolymer matrix.

62. The method of claim 58, in which laminating the multiple printed-wiring boards comprises adhering adjacent printed-wiring boards using a thermoset adhesive.

63. The method of claim 62, comprising curing the thermoset adhesive at a temperature of between 150 °C and 250 °C.

64. The method of any of claims 58 to 63, comprising defining a through-hole through at least a portion of the thickness of the multilayer laminated structure.

65. The method of claim 64, comprising defining the through-hole in an ultraviolet laser drilling process.

66. A method of making a laminate article, the method comprising: forming a layered article, the layered article comprising: first and second polymer films, each film comprising: a perfluorocopolymer matrix comprising a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer, and an additive material capable of absorbing ultraviolet light, an L-glass fabric disposed between the first and second polymer films; and a conductive cladding disposed in contact with the first film; and applying heat and pressure to the layered article to form the laminate article.

67. The method of claim 66, in which the fluorinated perfluorocopolymer comprises a fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer and the non-fluorinated perfluorocopolymer comprises a non-fluorinated tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer.

68. The method of claim 66 or 67, in which applying heat and pressure to the layered article comprises compressing the layered article in a heated platen.

69. The method of any of claims 66 to 68, in which applying heat and pressure to the layered article comprises processing the layered article in a roll-to-roll lamination process.

70. The method of any of claims 66 to 69, in which applying heat and pressure to the layered article comprises applying to the layered article a temperature between 10 and 30 °C greater than a melting point of the perfluorocopolymer matrix.

71 . The method of any of claims 66 to 70, in which applying heat and pressure to the layered article comprises applying to the layered article a temperature of between 300 °C and 400 °C.

72. The method of any of claims 66 to 71 , in which applying heat and pressure to the layered article comprises applying to the layered article a pressure of between 200 psi and 1000 psi.

73. The method of any of claims 66 to 72, comprising forming the first and second films in a melt processing and extrusion process.

74. The method of claim 73, in which forming the first and second films comprises mixing the fluorinated perfluorocopolymer and the non-fluorinated perfluorocopolymer.

75. The method of claim 74, comprising dispersing the additive material in the fluorinated perfluorocopolymer prior to mixing the fluorinated perfluorocopolymer and the non-fluorinated perfluorocopolymer.

76. The method of any of claims 66 to 75, comprising treating the L-glass fabric with a fluoropolymer treatment.

77. The method of claim 76, in which treating the L-glass fabric with a fluoropolymer treatment comprises coating the L-glass fabric with a fluoropolymer coating.

78. The method of claim 77, in which coating the L-glass fabric with a fluoropolymer coating comprises coating the L-glass fabric in a solution coating process.

79. The method of claim 77 or 78, in which coating the L-glass fabric with a fluoropolymer coating comprises depositing fluoropolymer particles on a surface of the L-glass fabric.

80. The method of any claims 66 to 79, in which each polymer film comprises a first layer comprising the fluorinated perfluorocopolymer and the non- fluorinated perfluorocopolymer and a second layer comprising the non-fluorinated perfluorocopolymer, and in which each second layer is disposed in contact with the quartz fabric and each second layer is disposed in contact with the conductive cladding.