Flexible laminated materials

Abstract

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

Description

[Technical Field]

[0001] Metal clad laminates are used as printed wiring board substrates in a variety of electronic applications. Summary of the Invention [Means for solving the problem]

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

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

[0004] L-glass fabric comprises yarns of L-glass, NL-glass or L2-glass.

[0005] The laminate article has a thickness of from 20 μm to 200 μm, for example from 30 μm to 90 μm or from 30 μm to 60 μm.

[0006] The dielectric substrate has a dielectric constant at 10 GHz of 2.10 to 2.70, for example, 2.10 to 2.40.

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

[0008] The dielectric substrate has a dielectric loss tangent at 10 GHz of less than 0.0015, for example, 0.0006 to 0.001 or 0.0006 to 0.0008.

[0009] The laminated article has a planar shape that defines an XY plane, and the thermal expansion coefficient of the laminated article in the XY plane is 5 to 25 ppm / °C, for example, 14 to 20 ppm / °C or 16 to 22 ppm / °C.

[0010] Fluorinated perfluorocopolymers include fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers, and non-fluorinated perfluorocopolymers include non-fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers.

[0011] The perfluorocopolymer matrix comprises 50 to 90 weight percent fluorinated perfluorocopolymer, for example, 10 to 50 weight percent non-fluorinated perfluorocopolymer.

[0012] The number of carboxyl end groups per million carbon atoms in the perfluorocopolymer matrix is sufficient so that the laminate article does not form conductive anodic filaments (CAFs).

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

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

[0015] The fluorinated perfluorocopolymer has no more than 5 carboxyl end groups per million carbon atoms.

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

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

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

[0019] L-glass has a basis weight of less than 100 g / m2, for example less than 50 g / m2.

[0020] The L-glass cloth has a thickness of 10 μm to 100 μm, for example, 10 μm to 30 μm.

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

[0022] L-glass cloth includes plasma-treated or corona-treated L-glass cloth.

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

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

[0025] The L-glass fabric is pre-treated with a fluoropolymer treatment before incorporation into the laminate article.

[0026] The dielectric substrate comprises 5 to 20 volume percent L-glass cloth and 80 to 95 volume percent perfluorocopolymer matrix.

[0027] The water contact angle of the L-glass cloth is 0° to 60°.

[0028] Additive materials include 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 thermosetting 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] Conductive cladding is disposed on two opposing surfaces of the dielectric substrate.

[0033] The conductive cladding comprises copper foil, which in some cases is disposed on the surface of the dielectric substrate by a lamination process.

[0034] The conductive cladding has a thickness of less than 72 μm, for example between 5 μm and 18 μm.

[0035] The conductive cladding has a root mean square (RMS) roughness of less than 1 μm, such as less than 0.5 μm.

[0036] In one aspect, a printed wiring board comprises a laminate article having any of the foregoing features, wherein a conductor pattern is formed within a conductive cladding.

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

[0038] The through holes are defined by the thickness of the laminate article and include a copper film that plates the through holes.

[0039] In one aspect, a multilayer printed wiring board comprises a multilayer laminate structure comprising a plurality of printed wiring boards according to the previous aspect.

[0040] Embodiments may 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 a laminate structure. Optionally, the thermoplastic adhesive is bonded at a temperature between 0 and 200°C below the melting point of the perfluorocopolymer matrix. Optionally, the thermoplastic adhesive is bonded at a temperature between 0 and 50°C below the melting point of the perfluorocopolymer matrix.

[0042] The multilayer printed wiring board includes a thermosetting adhesive disposed between adjacent printed wiring boards in a laminate structure, and in some cases, the thermosetting adhesive is cured at a temperature of 150°C to 250°C.

[0043] A through-hole is defined through at least a portion of the thickness of the multilayer printed wiring board and includes a copper film plating the through-hole.

[0044] An antenna usable in a 5G communication network may include a printed wiring board according to the above-described aspects.

[0045] In one aspect, a method of making a multilayer printed wiring board includes forming a conductor pattern in the conductive cladding of each of a plurality of laminate articles having any of the aforementioned characteristics to form a respective printed wiring board, and stacking the plurality of printed wiring boards to form a multilayer laminate structure.

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

[0047] Laminating multiple printed wiring boards includes bonding adjacent printed wiring boards using a thermoplastic adhesive. Optionally, the method includes bonding the thermoplastic adhesive at a temperature 0 to 200°C below the melting point of the perfluorocopolymer matrix. Optionally, the method includes bonding the thermoplastic adhesive at a temperature 0 to 50°C below the melting point of the perfluorocopolymer matrix.

[0048] Stacking the multiple printed wiring boards includes bonding adjacent printed wiring boards together using a thermosetting adhesive. Optionally, the method includes curing the thermosetting adhesive at a temperature of 150°C to 250°C.

[0049] The method includes defining a through hole through at least a portion of a thickness of the multi-layer laminate structure. Optionally, the method includes defining the through hole in an ultraviolet laser drilling process.

[0050] In one aspect, a method of making a laminate article includes forming a 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 cloth 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 laminated article.

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

[0052] Fluorinated perfluorocopolymers include fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers, and non-fluorinated perfluorocopolymers include non-fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers.

[0053] Applying heat and pressure to the layered article includes compressing the layered article within heated platens.

[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 subjecting the layered article to a temperature 10 to 30° C. above the melting point of the perfluorocopolymer matrix.

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

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

[0058] The method includes forming first and second films in a melt processing and extrusion process. Optionally, forming the first and second films includes blending a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer. Optionally, the method includes dispersing an additive material in the fluorinated perfluorocopolymer before blending the fluorinated perfluorocopolymer and the non-fluorinated perfluorocopolymer.

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

[0060] Each polymer film includes a first layer including a fluorinated perfluorocopolymer and a non-fluorinated perfluorocopolymer, and a second layer including a non-fluorinated perfluorocopolymer, each second layer being disposed in contact with the quartz cloth, and each second layer being disposed in contact with the conductive cladding. 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 explanation of the drawings]

[0061] [Figure 1] FIG. 1 is a diagram of a flexible metal clad laminate. [Figure 2] FIG. 1 is a diagram of a layer structure for a flexible metal clad laminate. [Figure 3A] FIG. 1 is a diagram of a stack having a conductive anode filament. [Figure 3B] FIG. 1 is a diagram of a stack having a conductive anode filament. [Figure 4] FIG. 1 is a diagram of a printed wiring board. [Figure 5] FIG. 1 is a diagram of a printed wiring board. [Figure 6] 1 is a diagram of a communication network. [Figure 7] FIG. 1 is a diagram of a roll-to-roll lamination process. [Figure 8] 1 is a flow chart of a method of making a flexible metal clad laminate. [Figure 9] 1 is a photograph of a flexible copper clad laminate. [Figure 10] 1 is a plot of the thickness of various flexible copper clad laminates. [Figure 11] 1 is a plot of resin content for various flexible copper clad laminates. [Figure 12A] 1 is a plot of dimensional stability measurements for various flexible copper clad laminates. [Figure 12B] 1 is a plot of dimensional stability measurements for various flexible copper clad laminates. [Figure 13]1 is a plot of the flatness of various flexible copper clad laminates. [Figure 14] 1 is a plot of the thickness of various flexible copper clad laminates. [Figure 15] 1 is a plot of resin content for various flexible copper clad laminates. [Figure 16] 1 is a plot of the dielectric constant of various flexible copper clad laminates. [Figure 17] 1 is a plot of the dissipation factor of various flexible copper clad laminates. [Figure 18A] 1 is a plot of dimensional stability measurements for various flexible copper clad laminates. [Figure 18B] 1 is a plot of dimensional stability measurements for various flexible copper clad laminates. [Figure 19] 1 is a plot of the dielectric loss tangent of blended PFA films as a function of the number of carboxyl end groups per 106 carbon atoms in the film. [Figure 20] 1 is a plot of the dielectric loss tangent of laminates as a function of the number of carboxyl end groups per 106 carbon atoms in the blended PFA film. [Figure 21] 1 is a plot of the copper peel strength of laminates as a function of the number of carboxyl end groups per 106 carbon atoms in the blended PFA film. DETAILED DESCRIPTION OF THE INVENTION

[0062] Described herein are metal-clad flexible laminates with low dielectric constants and low dissipation at high frequencies, e.g., 10 GHz. The flexible laminates described herein can be used as substrates for printed wiring boards in high-frequency applications, such as antennas for use in 5G cellular communication networks or automotive radar, among other applications. The flexible laminates described herein include a dielectric substrate formed from a perfluorocopolymer matrix and an L-glass cloth, e.g., a woven L-glass cloth, embedded therein. The perfluorocopolymer matrix includes perfluorinated perfluorocopolymers (referred to herein as "fluorinated perfluorocopolymers") and non-perfluorinated perfluorocopolymers (referred to herein as "non-fluorinated perfluorocopolymers"), such as perfluorinated and non-perfluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers. The additive material in the dielectric substrate can absorb ultraviolet light, for example, so that the laminate can be drilled with an ultraviolet laser to form through-holes through the thickness of the laminate. The flexible laminate is clad on one or both sides with a conductive cladding such as copper foil.

[0063] The presence of the L-glass cloth results in a laminate with a high degree of flatness, for example, a degree of flatness sufficient to allow alignment between multiple layers of the laminate during the drilling process. For example, in a multilayer laminate structure, the high degree of flatness allows alignment during the drilling of vias that penetrate 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 cloth and the CTE of the perfluorocopolymer matrix, together with the relatively low modulus of elasticity of the L-glass cloth (compared to, for example, quartz cloth), is such that the shrinkage of the L-glass cloth during cooling of the laminate is small enough to avoid the occurrence of waviness in the laminate.

[0064] 1, a metal-clad flexible laminate 100 includes a dielectric substrate 102 and conductive cladding, such as metal (e.g., copper) foils 104a, 104b (collectively referred to as conductive cladding 104), disposed on a top surface 106a and a bottom surface 106b, respectively, of the dielectric substrate 102. While the conductive cladding 104 is present on both surfaces 106a, 106b of the dielectric substrate 102 in FIG. 1, in some examples, the conductive cladding is disposed on only a single surface of the dielectric substrate 102 (e.g., only on the top surface 106a).

[0065] The dielectric substrate 102 of the flexible laminate 100 includes an L-glass cloth 108, e.g., a woven L-glass cloth (e.g., L-glass, NL-glass, or L2-glass yarns woven into a cloth), embedded in a perfluorocopolymer matrix 110 including fluorinated and non-fluorinated perfluorocopolymers, e.g., 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 cloth allows the coefficient of thermal expansion (CTE) of the dielectric substrate 102 in the xy plane to be matched to the CTE of the conductive cladding 104. An additive material 112 capable of absorbing ultraviolet (UV) light, e.g., light having a wavelength between 180 nm and 400 nm, is dispersed in the perfluorocopolymer matrix 110. The presence of the UV-reactive additive material 112 allows the flex laminate 100 to be drilled with a UV laser, for example, to form circuit structures such as vias through the thickness of the flex laminate 100 .

[0066] The flexible laminate 100 is a planar structure having a thickness along the z-axis of less than about 200 μm or less than about 100 μm, e.g., 20 μm to 200 μm, e.g., 30 μm to 90 μm, or 30 μm to 60 μm. The thickness of the dielectric substrate 102 constitutes the majority of the thickness of the flexible laminate 100. For example, the dielectric substrate 102 has a thickness along the z-axis of less than about 200 μm or less than about 100 μm, e.g., 20 μm to 200 μm, e.g., 30 μm to 90 μm, or 30 μm to 60 μm. Each conductive cladding 104 a, 104 b has a thickness along the z-axis of less than about 72 μm, e.g., less than about 18 μm, e.g., 5 μm to 18 μm.

[0067] The dielectric substrate 102 of the flexible laminate 100 has a low dielectric constant, for example, a dielectric constant at 10 GHz of less than about 2.7, for example, 2.1 to 2.7, for example, 2.1 to 2.4. The dielectric constant has a thermal coefficient having a value of -250 to 50 ppm / °C, for example, -100 to 50 ppm / °C or -50 to 25 ppm / °C, over a temperature range of 0 to 100°C. The dielectric substrate 102 also has a low dielectric loss tangent, for example, a dielectric loss tangent at 10 GHz of less than 0.0015, such as less than 0.001 or less than 0.0008, for example, 0.0002 to 0.001, for example, 0.0006 to 0.001, for example, 0.0006 to 0.0008.

[0068] The improved electrical properties (e.g., low dielectric constant and low dissipation factor) of the flexible laminate 100 allow designers to realize, for example, up to 25% or more improvement in insertion loss for a given characteristic impedance over existing 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.

[0069] The coefficient of thermal expansion (CTE) of the dielectric substrate 102 and the CTE of the conductive cladding 104 are similar in the xy plane of the flexible laminate 100. For example, when the conductive cladding 104 is copper foil, the CTE of the dielectric substrate 102 in the xy plane can be 5-25 ppm / °C, such as 16-22 ppm / °C, for example 14-20 ppm / °C. The matching of CTE values between the dielectric substrate 102 and the conductive cladding 104 provides dimensional stability to the flexible laminate 100, for example, to within about 0.1% of its original dimensions upon removal of the conductive cladding and temperature changes.

[0070] The conductive cladding 104 of the flexible laminate 100 is strongly adhered to the dielectric substrate. For example, the peel strength between the dielectric substrate 102 and the conductive cladding 104 is greater than 2 lb. / inch, e.g., greater than 4 lb. / inch, e.g., 2-20 lb. / inch or 4-20 lb. / inch. The flexible laminate 100 is mechanically robust to bending and can be bent through bend radii typically found in electronic devices without breaking any of the components of the flexible laminate 100. This flexibility facilitates installation of the flexible laminate 100 into a device.

[0071] The flexible laminate 100 is compatible with metallization techniques, such as plasma metallization, such that through-holes can be drilled by a UV laser to form 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., 5-20 seconds, 10-15 seconds, 10-30 seconds, 10-60 seconds, or 30-60 seconds.

[0072] The flexible laminate 100 can be used in printed wiring boards, such as flexible printed circuit board antennas. For example, the dimensions and electrical properties of the flexible laminate 100 can make it suitable for use in high frequency applications, such as antennas for mobile devices usable on 5G communication networks, or for use in automotive radar or other high frequency applications, as discussed further below. In some examples, multiple flexible laminates 100 can themselves be stacked into multilayer circuit board structures. The flexible laminate is substantially void-free and resistant to the formation of conductive anodic filaments, which contributes to the electrical reliability of the flexible laminate as a printed wiring board substrate.

[0073] The low dielectric constant and low dielectric loss tangent 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 may be linear, unbranched polymers. The fluorinated perfluorocopolymer has low or zero polarity and therefore a low dielectric constant and low dielectric loss tangent. However, fluorinated perfluorocopolymers are generally non-reactive; for example, fluorinated copolymers have poor adhesion to the L-glass cloth 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 cloth 108 and the conductive cladding 104. The presence of these reactive end groups promotes adhesion between the perfluorocopolymer matrix and the L-glass cloth 108 and the conductive cladding 104.

[0074] In some instances, the perfluorinated copolymers are prepared by aqueous dispersion polymerization and, as polymerized, have a molecular weight of 10 6 It can contain at least about 400 reactive end groups per carbon atom. Most of these end groups are thermally unstable in the sense that when exposed to heat or film lamination conditions such as those encountered during extrusion and film formation, they undergo chemical reactions such as decomposition and decarboxylation, which can cause the extruded polymer to discolor or become filled with uneven cells, or both. To produce the fluorinated perfluorocopolymer described herein, the polymerized perfluorocopolymer is stabilized to replace substantially all of the reactive end groups with thermally stable -CF3 end groups. An exemplary method of stabilization is to expose the fluoropolymer to a fluorinating agent such as elemental fluorine, for example, by a process such as that disclosed in U.S. Pat. No. 4,742,122 and U.S. Pat. No. 4,743,658, the contents of which are incorporated herein by reference in their entirety.

[0075] Non-fluorinated perfluorocopolymers typically have a higher dielectric loss tangent than fluorinated perfluorocopolymers. The composition of the perfluorocopolymer matrix 110 can be tailored to achieve both a sufficiently low dielectric constant and low dielectric loss tangent for the dielectric substrate 102, and sufficient adhesion to the L-glass cloth 108 and conductive cladding 104. For example, 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 cloth 108 and 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., 2.1 to 2.7, e.g., 2.1 to 2.4. A sufficiently low dielectric loss tangent for the dielectric substrate 102 is a dielectric loss tangent at 10 GHz of less than 0.0015, such as between 0.0002 and 0.001, e.g., between 0.0006 and 0.001, e.g., between 0.0006 and 0.0008. In some examples, the sufficiency of the adhesion between the perfluorocopolymer matrix 110, the L-glass cloth 108, and the conductive cladding 104 is determined by the peel strength between the dielectric substrate 102 and the conductive cladding 104. For example, the adhesion is sufficient if the peel strength is greater than 2 lb. / inch, e.g., greater than 4 lb. / inch, e.g., between 2 and 20 lb. / inch or between 4 and 20 lb. / inch. In some examples, the sufficiency of the adhesion between the perfluorocopolymer matrix 110, the L-glass cloth 108, and the conductive cladding 104 is determined by the tendency of the flexible laminate 100 to resist the formation of conductive anodic filaments (CAFs), which is discussed further below.

[0076] In some examples, the composition of the perfluorocopolymer matrix 110 is indicated by the ratio (e.g., weight or volume) of fluorinated perfluorocopolymer to non-fluorinated perfluorocopolymer. The weight percentage of fluorinated perfluorocopolymer can be 50% to 90%, such as 50% to 80%, e.g., 50%, 60%, 70%, 75%, 80%, or 90%. The weight percentage of non-fluorinated perfluorocopolymer can be 10% to 50%, e.g., 10%, 20%, 25%, 30%, 40%, or 50%.

[0077] In some examples, the composition of the perfluorocopolymer matrix 110 is indicated by the number (e.g., 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 the polymerization aspects, such as the selection of the polymerization medium, initiator, chain transfer agent, if present, and buffer, if present. The number of carboxyl end groups per million carbon atoms present in the perfluorocopolymer matrix 100 can be 30 to 70, e.g., 35 to 65. The number of carboxyl end groups can be selected to achieve sufficient adhesion between the perfluorocopolymer matrix 110, the L-glass cloth 108, and the conductive cladding 104, while also achieving a sufficiently low dielectric constant and dissipation factor. For example, the number of carboxyl end groups can be selected to prevent the formation of CAF in the flexible laminate 100. In some examples, the composition of fluorinated and non-fluorinated perfluorocopolymers is indicated by the number (e.g., number concentration) of carboxyl end groups present in each type of perfluorocopolymer. Fluorinated perfluorocopolymers may have fewer than 10 carboxyl end groups per million carbon atoms, e.g., 5 or fewer, or 1 or fewer, or fewer than 1 carboxyl end group per million carbon atoms. Non-fluorinated perfluorocopolymers may have 100 to 300 carboxyl end groups per million carbon atoms, e.g., 120 to 280 or 150 to 250 carboxyl end groups per million carbon atoms. Analysis and quantification of carboxyl end groups in perfluorocopolymers can be performed by infrared spectroscopy, 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 herein by reference in their entireties. The presence of thermally stable end groups -CF3 (a product of fluorination) is inferred from the absence of unstable end groups after fluorine treatment. The presence of -CF3 end groups leads to a reduction in the dielectric loss tangent of the perfluorocopolymer compared to other end groups.

[0078] The melt flow rate (MFR) of the fluorinated perfluorocopolymer, the non-fluorinated perfluorocopolymer, or both, can also affect the adhesion between the perfluorocopolymer matrix 110, the L-glass cloth 108, and the conductive cladding 104. A polymer with a high MFR flows more easily 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) allows the perfluorocopolymer matrix 110 to completely encapsulate the fibers of the L-glass cloth 108, resulting in a dielectric substrate 102 that is substantially void-free, e.g., non-porous. The void-free dielectric substrate 102 is resistant to CAF formation. For example, the MFR of the fluorinated perfluoro copolymer can be 1 to 40 g / 10 min, such as 2 to 15 g / 10 min, for example, 2 g / 10 min, 4 g / 10 min, 6 g / 10 min, 8 g / 10 min, 10 g / 10 min, 12 g / 10 min, 14 g / 10 min, 16 g / 10 min, 18 g / 10 min, 20 g / 10 min, 25 g / 10 min, 30 g / 10 min, 35 g / 10 min, or 40 g / 10 min. The MFR of the non-fluorinated perfluoro copolymer can be 1 to 40 g / 10 min, for example, 2 to 20 g / 10 min, for example, 2 g / 10 min, 5 g / 10 min, 10 g / 10 min, 15 g / 10 min, or 20 g / 10 min. The fluorinated and non-fluorinated perfluorocopolymers may be provided in a ratio that results in an overall MFR for the perfluorocopolymer matrix of 10 to 30 g / 10 min, e.g., 10 g / 10 min, 15 g / 10 min, 18 g / 10 min, 21 g / 10 min, 24 g / 10 min, 27 g / 10 min, or 30 g / 10 min.

[0079] Suitable materials for fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) perfluorocopolymers include Teflon™ perfluoroalkane (PFA) 416HP, which has an MFR of about 40 g / 10 min, or Teflon™ PFA 440HP(A / B) (The Chemours Company, Wilmington, Del.), which has an MFR of about 16 g / 10 min or 14 g / 10 min, respectively. Suitable materials for non-fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) include Teflon™ PFA 316, which has an MFR of about 40 g / 10 min, or Teflon™ PFA 340 (Chemours), which has an MFR of about 14 g / 10 min.

[0080] The fluorinated perfluorocopolymer, the non-fluorinated perfluorocopolymer, or both have a high melting point of 250° C. to 350° C., e.g., 280° C. to 320° C., 290° C. to 310° C., e.g., about 305° C. The high melting point of the fluorinated perfluorocopolymer, the non-fluorinated perfluorocopolymer, or both results in a perfluorocopolymer matrix 100 that is resistant to high temperatures, providing a dielectric substrate 102 with 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., 5-20 seconds, 10-15 seconds, 10-30 seconds, 10-60 seconds, or 30-60 seconds, when measured according to the IPC-TM-650 test method.

[0081] The composition of the perfluorocopolymer matrix 110 may be selected to enable the dielectric substrate 102 to be compatible with plasma processing, for example, for metallization of through-holes formed through the thickness of the flexible laminate 100.

[0082] Specific examples of fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers suitable for inclusion in perfluorocopolymer matrix 100 include Teflon™ perfluoroalkane (PFA) 416HP, having an MFR of about 40 g / 10 min, or Teflon™ PFA 440HP (The Chemours Company, Wilmington, Del.), having an MFR of about 14 g / 10 min. Specific examples of non-fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymers suitable for inclusion in perfluorocopolymer matrix 100 include Teflon™ PFA 316, having an MFR of about 40 g / 10 min, or Teflon™ PFA 340 (The Chemours Company), having an MFR of about 14 g / 10 min.

[0083] In some examples, the perfluorocopolymer matrix 100 is formed from a single type of perfluorocopolymer having both fluorinated and reactive end groups (e.g., rather than a mixture of fluorinated and non-fluorinated perfluorocopolymers). The ratio of fluorinated 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 cloth 108 and a sufficiently low dielectric constant and dissipation factor.

[0084] The presence of the woven L-glass fabric 108 allows the CTE of the dielectric substrate 102 to match the CTE of the metal foil 104. The woven L-glass fabric 108, which is embedded in a perfluorocopolymer matrix 110, is formed from spread glass (e.g., L-glass) strands.

[0085] 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 2.5 ppm / °C to 4 ppm / °C, e.g., 2.5 ppm / °C to 3 ppm / °C, or 3 ppm / °C to 4 ppm / °C. By adjusting the ratio of perfluorocopolymer matrix 110 to woven glass cloth 108, the CTE of the dielectric substrate 102 in the xy plane can be matched to the in-plane CTE of the metal foil 104, thereby providing a dimensionally stable flexible laminate 100. For example, the dielectric substrate 102 can include 5 to 20 volume percent L-glass woven cloth 108 and 80 to 95 volume percent perfluorocopolymer matrix 110 relative to the woven glass cloth 108. The CTE in the xy plane of the dielectric substrate 102 may be 5-25 ppm / °C, e.g., 16-22 ppm / °C, e.g., 14-20 ppm / °C, thereby providing dimensional stability of less than about 0.1%. In contrast, the CTE of the perfluorocopolymer matrix 110 alone may be 100-300 ppm / °C.

[0086] [Table 1]

[0087] L-glass has a low dielectric constant, such as a dielectric constant of 4.0 to 5.0 at 10 GHz, e.g., 4.5 to 5.0 or 4.5 to 4.8. Thus, the dielectric substrate 102 has a low dielectric constant and low loss, even with the L-glass cloth embedded in the perfluorocopolymer matrix. L-glass also has a low dielectric loss tangent, such as a dielectric loss tangent of 0.002 to 0.003 at 10 GHz, e.g., 0.002, 0.0023, 0.0025, 0.0028, or 0.003.

[0088] The L-glass woven fabric 108 has a thickness of less than about 100 μm, for example, 30 μm to 100 μm or 10 μm to 30 μm, which helps to achieve a thin dielectric substrate 102. The basis weight of the quartz cloth 108 is about 1000 g / m 2Less than, for example, about 50 g / m 2 Less than, for example, 10 g / m 2 ~50g / m 2 In a specific example, the L-glass cloth 108 is NL1035 NL-glass cloth (Asahi Kasei Corporation, Tokyo, Japan).

[0089] In some examples, the woven L-glass fabric 108 is subjected to one or more surface treatments to improve wetting of the fibers of the woven L-glass fabric 108 by the perfluorocopolymer matrix 110, to remove residual organic matter, or to mechanically modify the surface of the fibers to enhance adhesion between the fibers of the L-glass fabric 108 and the perfluorocopolymer matrix 110. The purpose of the surface treatment may be to promote substantially complete wetting of the L-glass fibers (e.g., L-glass yarn) by the perfluorocopolymer, such that the perfluorocopolymer fully encapsulates the L-glass fiber (e.g., L-glass yarn) bundles. Sufficient encapsulation and sufficient adhesion of the L-glass fiber bundles by the perfluorocopolymer allows the dielectric substrate 102 to be substantially void-free, e.g., non-porous, which in turn helps to prevent the formation of conductive anode filaments and the occurrence of electromigration during post-processing, e.g., during the formation of vias through the thickness of the flexible laminate 100.

[0090] The surface treatment can include a heat treatment to remove residual organic matter (e.g., residual starch) from the surface of the L-glass fiber so that a clean L-glass surface is exposed to the perfluorocopolymer. The surface treatment can include the addition of an adhesion promoter, such as a methacrylate silane, an aminosilane, or a fluorosilane, to the surface of the L-glass fiber. The surface treatment can include a plasma or corona treatment. The surface treatment can include treatment with a polymer coating, such as a fluoropolymer, e.g., 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 fiber. For example, the L-glass cloth can be immersed in a solution containing a dispersion of a fluoropolymer to form a monolayer of the fluoropolymer on the surface of the L-glass fiber. 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 fiber. A combination of surface treatments can be applied, such as a heat treatment followed by a plasma or corona treatment. The surface treatment(s) applied to the L-glass cloth 108 can improve the wetting of the fibers by the perfluorocopolymer matrix 110, allowing for better encapsulation of the fibers of the L-glass cloth 108 by the perfluorocopolymer matrix 110 and stronger adhesion between the perfluorocopolymer matrix 110 and the fibers of the L-glass cloth 108, thereby contributing to the formation of a void-free dielectric substrate 102 that is resistant to CAF formation.

[0091] The wettability of L-glass fabric can be characterized by the water contact angle (WCA). After surface treatment, the L-glass fabric can have a WCA of 0° to 60°.

[0092] In some examples, the laminate structure can be designed to achieve good encapsulation of the L-glass cloth, for example, in addition to or instead of applying a surface treatment to the L-glass cloth. Referring to FIG. 2 , an exemplary metal-clad flexible laminate can be fabricated by laminating a set of layers 150. The set of layers includes multiple layers of fluoropolymer film, including non-fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) layers 162a, 162b disposed on either side of the L-glass cloth 108, and perfluorocopolymer layers 164a, 164b including fluorinated and non-fluorinated perfluorocopolymers disposed on the outer-facing side of each non-fluorinated layer 162. Conductive cladding (such as the aforementioned metal (e.g., copper) foils 104a, 104b) is disposed on the outside of both sets of layers 150. When the structure shown in FIG. 2 is laminated to produce a flexible laminate (see below for further discussion of the lamination process), the non-fluorinated layer 162 encapsulates the L-glass cloth 108 such that the non-fluorinated layer 162 and the perfluorocopolymer layer 164 form a matrix in which the L-glass cloth 108 is embedded, e.g., forming a dielectric substrate for the flexible laminate.

[0093] 1 , the additive material 112 is dispersed, e.g., homogeneously dispersed, in the perfluorocopolymer matrix 110. The additive material 112 is a material that can absorb UV light such that the flexible laminate 100 can be processed by a UV drilling process, 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., 1-2 volume percent, e.g., 1 vol %, 1.25 vol %, 1.5 vol %, or 2 vol %. The additive material 112 can be a material with a relatively low dielectric constant, e.g., a dielectric constant between 10 and 1000, such 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 example, including less than 2% by volume of additive material 112 can increase the dielectric constant of dielectric substrate 102 by less than 10%, such as less than 5% or less than 2%.

[0094] In some examples, the additive material 112 is an inorganic particle, such as cerium oxide (CeO), titanium dioxide (TiO), silicon dioxide (SiO), barium titanate (BaTiO), calcium titanate (CaTiO), zinc oxide (ZnO), or other suitable material. The particle may have a diameter of less than about 5 μm, less than about 2 μm, less than about 1 μm, or less than about 0.5 μm, e.g., between 0.1 μm and 0.5 μm. For example, smaller particles are often more effective UV light absorbers 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 thermosetting material, such as a polyimide, blended into the perfluorocopolymer matrix 110. In some examples, both inorganic particles and organic additives are used as additive materials.

[0095] The copper foil 104 of the flexible laminate 100 provides a platform upon which a conductive pattern can be defined, such that the flexible laminate 100 can be used, for example, 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, such as a roll-to-roll lamination process. For example, the copper foil can be an electrodeposited copper foil or a rolled copper foil. In some examples, the copper foil 104 is deposited, for example, electrolytically plated, onto the dielectric substrate 102.

[0096] The copper foil 104 has a thickness of less than about 72 μm, e.g., less than about 18 μm, e.g., between 10 μm and 18 μm. The copper foil 104 has a low root-mean-square (RMS) roughness, such as an RMS roughness of less than 1 μm, e.g., less than 0.5 μm, as measured by non-contact interferometry. The low RMS roughness of the copper foil 104 helps maintain low insertion loss in circuits fabricated 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 through a low RMS roughness) with good adhesion between the copper foil 104 and the dielectric substrate 102 (e.g., achievable through a higher RMS roughness). For example, 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 lb. / inch, e.g., 2-20 lb. / inch or 4-20 lb. / inch.

[0097] The copper foil 104 has a purity of at least about 99.9%. The surface chemistry of the copper foil 104 may be affected by surface treatments, such as treatment with zinc, thermal stability additives, and oxidation resistance treatments. These surface treatments may 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 increasing peel strength without significantly degrading the electrical performance of the substrate.

[0098] As discussed above, the dielectric substrate 102 of the flexible laminate 100 is substantially void-free and has sufficient adhesion between the perfluorocopolymer matrix 110 and the L-glass cloth 108, allowing the flexible laminate to resist the formation of conductive anodic filaments (CAFs). CAFs are metallic filaments that form, for example, within voids or weak areas of the dielectric substrate due to, for example, electromigration of metal induced by the application of an electric field. CAF formation can lead to electrical failure, for example, when the CAFs form short-circuit paths between vias through a printed wiring board. A flexible laminate can be considered free of CAF formation when it exhibits a resistance of greater than 10 megohms after an initial 96-hour equilibration period with less than a 10-fold drop in resistance throughout the test period. The CAF test can last, for example, up to 1000 hours or more with an applied voltage of 100 VDC to 1000 VDC, depending on the applicable standard.

[0099] An example of CAF formation is shown in Figure 3A, which shows a hypothetical laminate 200 having a dielectric matrix 202 with glass fibers 204 embedded therein. Through holes (sometimes referred to as vias) 206 are formed through the thickness of the laminate 200 and plated with a metal 208, e.g., copper. Upon application of an electric field, the metal 208 anodically dissolves, migrates, and redeposits within the dielectric matrix 202, e.g., at the interface between the dielectric matrix 202 and the glass fibers 204, to form filaments 210 extending between adjacent vias 206.

[0100] 3B shows another example of CAF formation in a hypothetical laminate 250 having a dielectric matrix 252 with embedded glass fibers 254 and a conductor pattern 262, e.g., a copper pattern, defined on the top, bottom, and interior surfaces of the laminate 250. Metal, e.g., copper, filaments 260 form at the interface between the conductor pattern 262 and the glass fibers 254.

[0101] 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 cloth 108. This is achieved, for example, by the properties of the perfluorocopolymer (e.g., the number concentration of reactive end groups), the surface chemistry of the L-glass cloth, and manufacturing parameters such as pressure and temperature (discussed below). In addition, the arrangement of the L-glass cloth 108 in the perfluorocopolymer matrix 110 is such that there is substantially no contact between the fibers of the cloth and the conductive cladding 104. As a result, CAF formation in the dielectric substrate 102 is minimized, and the flexible laminate 100 can be used with a reliable and robust printed wiring board substrate.

[0102] Referring to FIG. 4, a multilayer printed wiring board 300 can be formed from multiple 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, for example, by UV drilling, where the UV energy is absorbed by an 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, for example, an adhesive capable of bonding 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 capable of bonding at a temperature 0°C to 50°C below the melting point of the perfluorocopolymer matrix. In some examples, the adhesive is a thermosetting adhesive capable of bonding at temperatures between 0°C and 200°C, for example, 150°C to 250°C, which are below the melting point of the perfluorocopolymer matrix.

[0103] Referring to FIG. 5, multiple (here, three) flexible laminates 100 are laminated together to form a multilayer printed wiring board 400. A central flexible laminate 100c includes top and bottom conductive claddings. Flexible laminates 100d and 100e each include a single conductive cladding. Flexible laminates 100c and 100d are bonded to the central flexible laminate 100e by adhesive layers 402a and 402b, respectively. The adhesive layers 402a and 402b may be, for example, an adhesive capable of bonding at temperatures below the melting point of the perfluorocopolymer matrix of the flexible laminate 100. In some examples, the adhesive is a thermoplastic adhesive capable of bonding at temperatures 0°C to 50°C below the melting point of the perfluorocopolymer matrix. In some examples, the adhesive is a thermosetting adhesive capable of bonding at temperatures 0°C to 200°C below the melting point of the perfluorocopolymer matrix.

[0104] Vias (not shown) may be defined through all or a portion of the thickness of multilayer printed wiring board 400, for example, by UV drilling.

[0105] Printed wiring boards made from the flexible laminates 100 described herein can be used in a variety of applications, for example, high frequency applications such as high frequency communication applications. For example, 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 device) capable of operating on a 5G communication network. For example, the flexible laminate can be useful as a substrate for a printed wiring board for a communication device antenna or antenna feedline for connecting electronic components of the device located on different planes. A printed wiring board 504 including one or more flexible laminates can be used in communication network equipment, such as a transmitting antenna in a tower 508 of a cellular communication network. Printed wiring boards including a flexible laminate can also be used in other applications, such as a camera feedline in a mobile computing device.

[0106] The flexible laminates described herein can be manufactured by a lamination process. Referring to FIG. 7 , in one example, an L-glass cloth 108 is disposed between two perfluorocopolymer films 120a, 120b. Each perfluorocopolymer film 120a, 120b has a thickness of 10 μm to 100 μm, e.g., 10 μm to 80 μm, 10 μm to 60 μm, or 20 μm to 50 μm. Conductive claddings 104a, 104b are disposed on the perfluorocopolymer films 120a, 120b, respectively. For example, the conductive cladding 104 is an electrodeposited copper foil or a rolled annealed copper foil. Each conductive cladding 104a, 104b has a thickness of less than about 72 μm, e.g., less than about 18 μm, e.g., 10 μm to 18 μm.

[0107] The layers of material 104, 108, 120 are heated and compressed to solidify the layers of material, thereby forming the flexible laminate 100. In some examples, the L-glass cloth 108 and two perfluorocopolymer films 120a, 120b are laminated to form a dielectric substrate, and a conductive cladding (e.g., copper foil) is electrodeposited onto the dielectric substrate in a second processing step.

[0108] The lamination process parameters (e.g., temperature, time, and pressure) are selected to achieve a target viscosity of the perfluorocopolymer that allows it to flow, thereby wetting and encapsulating the glass bundles of the L-glass cloth 108 and enabling good adhesion between the perfluorocopolymer and the conductive cladding 104. For example, the process parameters are selected so that the perfluorocopolymer reaches a zero-shear viscosity of 2000 Pa-s to 5000 Pa-s at 330°C. The temperature can be above the melting point of the perfluorocopolymer, e.g., 10°C to 30°C higher than the melting point of the perfluorocopolymer. For example, the temperature can be 300°C to 400°C, e.g., 320°C to 330°C, e.g., 300°C, 320°C, 340°C, 360°C, 380°C, or 400°C. The temperature ramp rate can be 1-5°C / min, e.g., 1°C / min, 2°C / min, 3°C / min, 4°C / min, or °C / min. The pressure applied to the layers of material can be 100 psi to 1000 psi, e.g., 200 psi to 1000 psi, or 600 psi to 1000 psi. The dwell time (e.g., for a static lamination process) can be 30 minutes to 120 minutes, e.g., 30 minutes, 60 minutes, 90 minutes, or 120 minutes.

[0109] 7 shows an isopressure roll-to-roll lamination process using a set of rollers 600. In some examples, the roll-to-roll lamination process is an isovolume gap controlled lamination process. In some examples, the lamination process is a static lamination process in which layers of material are pressed between heated platens.

[0110] The perfluorocopolymer film 120 is formed, for example, by melt processing and extrusion. In some examples, the additive material is mixed into a molten fluorinated perfluorocopolymer, and the mixture of fluorinated copolymer and additive material is mixed with a molten non-fluorinated perfluorocopolymer. In some examples, the additive material is mixed into a molten non-fluorinated perfluorocopolymer, and the mixture of non-fluorinated perfluorocopolymer and additive material is mixed with a molten fluorinated perfluorocopolymer. The resulting perfluorocopolymer mixture is extruded to form a perfluorocopolymer film. Mixing the additive material with the non-fluorinated perfluorocopolymer helps to integrate and distribute the additive material throughout the perfluorocopolymer film.

[0111] 8 is a flowchart of an exemplary process for making a flexible laminate 100. An additive material capable of absorbing ultraviolet light is dispersed (700) in a non-fluorinated perfluorocopolymer, such as a non-fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) perfluorocopolymer. The additive material may be, for example, particles of cerium oxide, titanium dioxide, silicon dioxide, barium titanate, calcium titanate, or zinc oxide; or a polymer additive such as a polyimide. The non-fluorinated perfluorocopolymer with the dispersed additive material is mixed (702) with a fluorinated perfluorocopolymer, such as a fluorinated tetrafluoroethylene / perfluoro(alkyl vinyl ether) perfluorocopolymer, to form a perfluorocopolymer mixture. The perfluorocopolymer mixture is melt processed and extruded to form a perfluorocopolymer film (704).

[0112] The woven L-glass cloth is exposed to a surface treatment, such as a heat treatment, a corona or plasma treatment, or the formation of a coating on the surface of the fibers of the L-glass cloth (706). Copper foil, e.g., electrodeposited copper foil or rolled annealed copper foil, is also exposed to a surface treatment, such as a heat treatment, a corona or plasma treatment, or the deposition of an adhesion promoter or thermal stability additive (708).

[0113] A layered stack of materials is formed (710) comprising a treated L-glass cloth disposed between two perfluorocopolymer films, with treated conductive cladding on both the top and bottom of the stack. The layered stack of materials is laminated (712) by applying heat and pressure, for example, in a static lamination process or a roll-to-roll lamination process, to form a flexible laminate. [Example]

[0114] The following polymers and polymer dispersions are used in these examples:

[0115] PFA1: Teflon™ PFA 440HP(A / B) (Chemours), a high purity fluorinated perfluoroalkoxy (PFA) melt-processable resin with an MFR of 16 g / 10 min (for “A”) and 14 g / 10 min (for “B”).

[0116] PFA2: Teflon™ PFA 340 (Chemours), a general-purpose non-fluorinated PFA melt-processible resin with an MFR of 14 g / 10 min.

[0117] PFA3: Teflon™ PFA 416HP (Chemours), a high purity fluorinated PFA melt processable resin with an MFR of 40 g / 10 min.

[0118] Example 1: Mechanical characterization of flexible copper clad laminates with L-glass or quartz cloth Experiments were conducted to investigate the thickness, flatness, and dimensional stability of copper-clad laminates incorporating L-glass cloth and quartz cloth. PFA film was combined with either Asahi NL1035 NL-glass cloth or Shin-Etsu 1027C-04 quartz cloth and 12 μm-thick BHFX-P92F-HG rolled copper foil from JX Nippon Mining & Metals Corporation (Tokyo, Japan) to form flexible copper-clad laminates. The PFA film consisted of 50 wt% PFA1, 25 wt% PFA2, and 22.5 wt% PFA3, and 2.5 wt% TiO particles (50.63 vol% PFA1, 25.31 vol% PFA2, and 22.78 vol% PFA3, and 1.28 vol% TiO particles), and both sides of the film were corona-treated. The materials were laminated in a hot oil vacuum press at a peak temperature of 320° C. and a pressure of 200 psi.

[0119] Details of the experimental setup, including the 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 μm in this example), the thickness of the perfluorocopolymer film used to create the laminate (54 μm in this example), and the type of fabric (NL1035 L-glass or 1035 quartz glass fabric in this example). The materials were laminated in a hot oil vacuum press at a dwell temperature of 320°C and 200 psi pressure, with a dwell time of 60 minutes, a vacuum of 1 atmosphere, and a ramp rate of 2°C / min. Samples were allowed to equilibrate at 23°C and 50% relative humidity for 24 hours before testing.

[0120] [Table 2]

[0121] The laminates are shown in the photograph in Figure 9. The flatness of each laminate was visually characterized. As can be seen from Figure 9, the laminate containing the L-glass cloth is flatter than the laminate containing the quartz cloth.

[0122] The thickness of each laminate was measured after etching according to IPC TM-650 2.2.18 test method, and the results are shown in Figure 10. L-glass laminates are generally thicker than quartz glass laminates. The thickness and estimated squeeze-out results are shown in Table 3. The estimated squeeze-out is measured by measuring the distance the film flows from the edge of the laminate as it is squeezed. The resin content of each laminate is shown in Figure 11.

[0123] [Table 3]

[0124] The dimensional stability results for the laminates tested in the machine direction (MD) and cross direction (CMD) are shown in Figure 12A (tested according to IPC TM-650 2.2.4b) and Figure 12B (test conducted according to IPC TM-650 2.2.4c), which show lower dimensional stability values for the L-glass laminates than for the quartz glass laminates.

[0125] Example 2: Characterization of flexible copper clad laminates with L-glass or quartz cloth Additional experiments were conducted to investigate the relationship between thickness, flatness, and dimensional stability. Various types of PFA film were combined with various types of glass cloth, including 1017C-02, 1027C-04, 1035C-04, 1078C-04, or 2116C-04 quartz cloth from Shin-Etsu, or NL1027, NL1035, NL-1078, or L2-1078L-glass or NL-glass cloth from Asahi. The PFA film and glass cloth were laminated with 12 μm-thick BHFX-P92F-HG rolled copper foil from JX Nippon Mining & Metals Corporation to form flexible copper foil laminates. In some cases, R101 titanium dioxide particles (Chemours) were added at a filler loading of 1.25% by volume. The material was laminated in a hot oil vacuum press at a peak temperature of 320°C and a pressure of 200 psi with a 60 minute dwell time, 1 atmosphere vacuum, and a ramp rate of 2°C / min.

[0126] A variety of PFA films were tested, including: PFA film 1 consisted of 50 wt% PFA1, 25 wt% PFA2, and 22.5 wt% PFA3, and 2.5 wt% TiO2 particles (50.63 vol% PFA1, 25.31 vol% PFA2, and 22.78 vol% PFA3, and 1.28 vol% TiO2 particles), and both sides of the film were treated with corona treatment. PFA film 2 consisted of 75 wt% PFA3 and 25 wt% PFA2 mixed with 2.5 wt% (1.25 vol%) R101 TiO2 particles.

[0127] [Table 4]

[0128] The data from these experiments are shown in Figures 13-17. Figure 13 is a plot of the 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). Figure 14 is a plot of the thickness of each laminate, measured after etching according to IPC TM-650 2.2.18 test method. These results show that thicker laminates are generally flatter than thinner laminates. Figure 15 is a plot of the resin content of each laminate.

[0129] The dielectric constant and dissipation factor of each sample were also measured. The dielectric constant and dissipation factor were measured at 23°C and 50% relative humidity according to IPC TM-650 2.5.5.13 test method. The results are shown in Figures 16 and 17. The dimensional stability results by Methods B and C are shown in Figures 18A and 18B.

[0130] These results show the effect of L-glass cloth versus quartz glass cloth on the dielectric constant and dissipation factor of the laminate for the same resin content.

[0131] Example 3: Effect of End Group Content on Copper Clad Laminates The effect of end group content on copper-clad laminate properties was evaluated by preparing PFA1 (fluorinated PFA) and PFA2 (non-fluorinated PFA) resins in combination with R101 titania (Chemours) at various ratios of PFA2 to PFA1. Approximately 70 grams of the resin mixtures were dry blended and then fed into a Rheometer Services Inc. System 10 batch mixer equipped with a 60 cc mixing bowl containing a roller blade. These blends were mixed at 150 rpm and 350°C for 10 minutes to disperse all components. The mixtures were then removed from the bowl and subsequently pressed into plaques measuring approximately 100 mm x 100 mm by approximately 0.20 mm thick at 350°C for use in electrical testing and subsequent lamination. The pressed films were tested and found to have the electrical properties shown in Table 5.

[0132] [Table 5]

[0133] As expected, the dielectric constant (Dk) remained fairly consistent with PFA2 loading, and the dissipation factor (DF) increased linearly with increasing concentration of PFA2 in the blends.

[0134] About Selective Blending 10 6 Measurements were also made to determine the total number of carboxyl end groups per carbon atom, and the results are shown in Table 6.

[0135] [Table 6]

[0136] Similar to the dissipation factor data, the addition of PFA2 to the blends was found to increase the amount of end groups measured in a generally linear fashion. A plot of the measured dissipation factor as a function of end group level is shown in Figure 19. This helps to demonstrate how directly the end group level relates to the measured electrical behavior of the blend films.

[0137] These blended PFA films were combined with NL2116 fabric (Asahi Kasei, Japan) and 35 μm EXP-WS copper foil (Furukawa Electric Co., Ltd., Japan) and laminated in an electrically heated press (PHI, USA) at 320°C and 400 psi for a 60-minute dwell time to form copper-clad laminates. Experimental details are shown in Tables 7A and 7B.

[0138] [Table 7]

[0139] [Table 8]

[0140] The laminated material was tested for various properties, and the results are shown in Tables 8A and 8B.

[0141] [Table 9]

[0142] [Table 10]

[0143] 10 6 It was found that there was a very good correlation between the total number of end groups per carbon atom and the dissipation factor, and a suggested relationship between copper peel strength and end groups. These data can be seen in Figures 20 and 21.

[0144] Example 4: Sharpie Wicking Behavior of Commercially Available Laminates In the Sharpie wicking test, a hole is formed in a flexible laminate, a Sharpie® permanent marker is rubbed around the edge of the hole, and the hole is washed with isopropanol to remove excess ink. The radial distance away from the edge of the hole to which the ink has wicked is measured. Without being bound by theory, it is believed that this wicking test serves as an indicator of adhesion between the fibers of the quartz cloth and the perfluorocopolymer matrix. Poor adhesion or poor encapsulation can leave voids into which the ink can wick, resulting in a longer travel distance. In contrast, a substrate with good adhesion and good encapsulation will exhibit a low wicking distance.

[0145] Sharpie wicking test results for laminates predict the laminate's performance under CAF testing. To demonstrate this correlation, 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 a sharpie wicking result of less than 0.5 mm corresponds to a material with good CAF resistance. Flexible copper clad laminates with L-glass are expected to exhibit sharpie wicking of less than 1 mm.

[0146] [Table 11]

[0147] Specific 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 an 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, concurrent operations and parallel processing may be advantageous.

Claims

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

2. 10. The laminate article of claim 1, wherein the L-glass fabric comprises L-glass, NL-glass, or L2-glass yarns.

3. The laminate article of claim 1 or 2, wherein the laminate article has a thickness of from 20 μm to 200 μm.

4. The laminate article of claim 3, wherein the thickness of the laminate article is from 30 μm to 90 μm.

5. The laminate article of claim 4, wherein the thickness of the laminate article is from 30 μm to 60 μm.

6. The laminate article of any one of claims 1 to 5, wherein the dielectric substrate has a dielectric constant at 10 GHz of 2.10 to 2.

70.

7. The laminate article of claim 6, wherein the dielectric constant of the dielectric substrate is from 2.10 to 2.

40.

8. A laminate article according to any one of claims 1 to 7, wherein the dielectric substrate has a thermal coefficient of dielectric constant having a value of -250 to +50 ppm / °C over the temperature range of 0 to 100°C.

9. The laminate article of any one of claims 1 to 8, wherein the dielectric substrate has a dissipation factor at 10 GHz of less than 0.0015.

10. 10. The laminate article of claim 9, wherein the dielectric substrate has a dissipation factor at 10 GHz of 0.0006 to 0.

001.

11. The laminate article of claim 10, wherein the dielectric loss tangent of the dielectric substrate at 10 GHz is 0.0006 to 0.0008.

12. 12. The laminate article of any one of claims 1 to 11, wherein the laminate article has a planar shape defining an XY plane, and the coefficient of thermal expansion of the laminate article in the XY plane is 5 to 25 ppm / °C.

13. The laminate article of claim 12, wherein the coefficient of thermal expansion of the laminate article in the XY plane is 14 to 20 ppm / °C.

14. The laminate article of claim 12, wherein the coefficient of thermal expansion of the laminate article in the XY plane is 16 to 22 ppm / °C.

15. 15. The laminate article of any one of claims 1 to 14, wherein 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.

16. The laminate article of any one of claims 1 to 15, wherein said perfluorocopolymer matrix comprises 50 to 90% by weight of said fluorinated perfluorocopolymer.

17. The laminate article of claim 16, wherein said perfluorocopolymer matrix comprises 10 to 50% by weight of said non-fluorinated perfluorocopolymer.

18. 18. The laminate article of any one of claims 1 to 17, wherein the number of carboxyl end groups per million carbon atoms in the perfluorocopolymer matrix is sufficient such that the laminate article does not form conductive anode filaments (CAF).

19. 19. The laminate article of any one of claims 1 to 18, wherein the 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 greater than 2 lb / inch.

20. 20. The laminate article of any one of claims 1 to 19, wherein 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 one of claims 1 to 20, wherein said fluorinated perfluorocopolymer has no more than 5 carboxyl end groups per million carbon atoms.

22. The laminate article of any one of claims 1 to 21, wherein said non-fluorinated perfluorocopolymer has from 100 to 300 carboxyl end groups per million carbon atoms.

23. The laminate article of any one of claims 1 to 22, wherein the perfluorocopolymer matrix has a melt flow rate (MFR) of 10 g / 10 min to 30 g / 10 min.

24. The laminate article of any one of claims 1 to 23, wherein the perfluorocopolymer matrix has a solder float resistance at 288°C of at least 10 seconds.

25. The L-glass is 100 g / m ２ The laminate article of any one of claims 1 to 24, having a basis weight of less than 1000g.

26. The basis weight of the L-glass cloth is 50 g / m ２ 26. The laminate article of claim 25, wherein the thickness is less than 1 / 2 mm.

27. The laminated article of any one of claims 1 to 26, wherein the L-glass cloth has a thickness of from 10 μm to 100 μm.

28. 28. The laminated article of claim 27, wherein the L-glass cloth has a thickness of from 10 μm to 30 μm.

29. The laminate article of any one of claims 1 to 28, wherein the L-glass cloth comprises an aminosilane or methacrylate silane surface chemical treatment.

30. The laminated article of any one of claims 1 to 29, wherein the L-glass cloth comprises a plasma-treated or corona-treated L-glass cloth.

31. The laminated article of any one of claims 1 to 30, wherein the L-glass cloth is impregnated with a fluoropolymer.

32. The laminate article of any one of claims 1 to 31, wherein the L-glass fabric comprises a fluoropolymer coating.

33. The laminate article of any one of claims 1 to 32, wherein the L-glass fabric is pretreated with a fluoropolymer treatment prior to incorporation into the laminate article.

34. The laminate article of any one of claims 1 to 33, wherein the dielectric substrate comprises 5 to 20 volume percent of the L-glass cloth and 80 to 95 volume percent of the perfluorocopolymer matrix.

35. The laminated article of any one of claims 1 to 34, wherein the L-glass fabric has a water contact angle of 0° to 60°.

36. The laminate article of any one of claims 1 to 35, wherein the additive material comprises inorganic particles.

37. 37. The laminate article of claim 36, wherein 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 one of claims 1 to 37, wherein the additive material comprises a thermosetting polymer.

39. The laminate article of any one of claims 1 to 38, wherein the additive material is present in the perfluorocopolymer matrix at a volume percent of less than 2%.

40. The laminate article of any one of claims 1 to 39, wherein the additive material is homogeneously dispersed throughout the perfluorocopolymer matrix.

41. The laminate article of any one of claims 1 to 40, wherein the conductive cladding is disposed on two opposing surfaces of the dielectric substrate.

42. The laminate article of any one of claims 1 to 41, wherein the conductive cladding comprises copper foil.

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

44. The laminate article of any one of claims 1 to 43, wherein the conductive cladding has a thickness of less than 72 μm.

45. 45. The laminate article of claim 44, wherein the thickness of the conductive cladding is from 5 μm to 18 μm.

46. The laminate article of any one of claims 1 to 45, wherein the conductive cladding has a root mean square (RMS) roughness of less than 1 μm.

47. 47. The laminate article of claim 46, wherein the RMS roughness of the conductive cladding is less than 0.5 μm.

48. A printed wiring board, The laminate article according to any one of claims 1 to 47, A printed wiring board having a conductor pattern formed within the conductive cladding.

49. 49. The printed wiring board of claim 48, wherein through holes are defined by the thickness of the laminate article and include a copper film plating the through holes.

50. A multilayer printed wiring board, 50. A multilayer printed wiring board comprising a multilayer laminate structure comprising a plurality of the printed wiring boards of claims 48 or 49.

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

52. 52. The multilayer printed wiring board of claim 51, wherein the thermoplastic adhesive is bonded at a temperature 0 to 200° C. below the melting point of the perfluorocopolymer matrix.

53. 53. The multilayer printed wiring board of claim 52, wherein the thermoplastic adhesive is bonded at a temperature 0 to 50° C. below the melting point of the perfluorocopolymer matrix.

54. 51. The multilayer printed wiring board of claim 50, including a thermosetting adhesive disposed between adjacent printed wiring boards in the laminate structure.

55. 55. The multilayer printed wiring board of claim 54, wherein the thermosetting adhesive is cured at a temperature of 150°C to 250°C.

56. A multilayer printed wiring board as described in any one of claims 5048 to 55, wherein the through holes are defined by at least a portion of the thickness of the multilayer printed wiring board and include a copper film that plates the through holes.

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

58. 1. A method for making a multilayer printed wiring board, the method comprising: forming a conductor pattern within the conductive cladding of each of a plurality of laminate articles of claim 1 to form a respective printed wiring board; and stacking a plurality of printed wiring boards to form a multi-layer laminate structure.

59. 60. The method of claim 58, wherein stacking the plurality of printed wiring boards comprises adhering adjacent printed wiring boards using a thermoplastic adhesive.

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

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

62. 60. The method of claim 58, wherein stacking the plurality of printed wiring boards comprises bonding adjacent printed wiring boards together using a thermosetting adhesive.

63. 63. The method of claim 62, comprising curing the thermosetting adhesive at a temperature of 150°C to 250°C.

64. 64. The method of any one of claims 58 to 63, comprising defining through holes through at least a portion of the thickness of the multi-layer laminate structure.

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

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

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

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

70. 70. The method of any one of claims 66 to 69, wherein applying heat and pressure to the layered article comprises applying a temperature to the layered article that is 10 to 30°C above the melting point of the perfluorocopolymer matrix.

71. 71. The method of any one of claims 66 to 70, wherein applying heat and pressure to the layered article comprises subjecting the layered article to a temperature of from 300°C to 400°C.

72. 72. The method of any one of claims 66-71, wherein applying heat and pressure to the layered article comprises applying a pressure of 200 psi to 1000 psi to the layered article.

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

74. 74. The method of claim 73, wherein forming the first film and the second film comprises blending the fluorinated perfluorocopolymer and the non-fluorinated perfluorocopolymer.

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

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

77. 77. The method of claim 76, wherein treating the L-glass cloth with a fluoropolymer treatment comprises coating the L-glass cloth with a fluoropolymer coating.

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

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

80. 80. The method of any one of claims 66-79, wherein 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, each second layer being disposed in contact with the quartz cloth, and each second layer being disposed in contact with the conductive cladding.

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