Low dielectric resin substrate

Abstract

The technical problem to be solved by the present invention is to provide a resin substrate using quartz glass cloth having a low dielectric loss tangent and excellent tensile strength. The solution provided by the present invention is a low-dielectric resin substrate obtained by compounding an organic resin with annealed quartz glass cloth subjected to a heat treatment, wherein the annealed quartz glass cloth has a dielectric loss tangent of less than 0.0010 at 10 GHz and a weight per unit area (g / m2). 2 ) has a tensile strength of 1.0 N / 25 mm or more.

Description

Technical Field

[0001] The invention relates to a low-dielectric resin substrate. Background Art

[0002] Currently, with the advancement of high-speed communications such as 5G, there is a strong demand for high-speed communication substrates and antenna substrates that have low transmission loss even when using high frequencies such as millimeter waves. In addition, in information terminals such as smartphones, the high-density mounting and ultra-thinness of circuit substrates are progressing significantly.

[0003] For high-speed communications such as 5G, a laminated board obtained by stacking, heating, pressurizing, and curing prepregs is being widely used. The prepreg is obtained by impregnating low-dielectric glass cloths such as D glass, NE glass, and L glass with thermoplastic resins such as fluororesin or polyphenylene ether, and thermosetting resins such as low-dielectric epoxy resins or low-dielectric maleimide resins. However, although glass cloths with improved dielectric properties such as D glass, NE glass, and L glass have been proposed, the dielectric loss tangent of any of the above glasses in the high-frequency range above 10G is relatively large, at around 0.002 to 0.005. When high frequencies such as millimeter waves are used for communication, the transmission loss is large and correct information cannot be transmitted.

[0004] In addition, as Edward A.Wolff formula: Transmission loss As shown in FIG. 1 , a material with a smaller dielectric constant (ε) and dielectric loss tangent (tan δ) can improve signal transmission loss.

[0005] To lower the dielectric loss tangent of organic resin substrates used in printed wiring boards and other applications, inorganic powders or glass cloths with lower dielectric loss tangents than resins are commonly used. However, inorganic powders or glass cloths with dielectric loss tangents less than 0.0010 in the high-frequency range and dielectric constants below 4.0 are virtually unknown.

[0006] Silica powder or quartz glass cloth, one of the representative general-purpose inorganic powders, is an inorganic powder added to resin or a reinforcing material for a substrate. It has a low coefficient of expansion and is excellent in insulation and dielectric properties.

[0007] Quartz glass cloth is known to have excellent dielectric properties, but currently available quartz glass cloth has a dielectric loss tangent of 0.0010 or higher at 10 GHz. Furthermore, due to the wide variety of methods used to produce silica powder, the dielectric loss tangent ranges from 0.005 to over 0.0005 at 10 GHz, with significant variation depending on the production method. It is not possible to obtain a single quartz glass cloth or silica powder with a dielectric loss tangent that approaches the level of pure quartz, i.e., less than 0.0005.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 5-170483

[0011] Non-patent literature

[0012] Non-patent document 1: Changing the OH group concentration in the heat treatment process, February 2011, Fukui University Graduate School of Engineering Preparatory Course Paper

[0013] Non-patent document 2: Structural modification of Structural heat treatment, Fukui University Graduate School of Engineering, February 2005, pre-doctoral course paper Summary of the Invention

[0014] Technical Problems to be Solved by the Invention

[0015] Patent Document 1 describes silica glass fibers produced by a sol-gel method, which are heat-treated to produce a silica glass fiber with a moisture content of 1000 ppm or less. While a printed circuit board using this silica glass and a fluororesin (PTFE) is described, this silica glass is not etched solely by heat treatment, which is completely different from the annealed quartz glass cloth used in the present invention. This can also be seen from the following.

[0016] First, although Patent Document 1 describes the moisture content of the heat-treated silica glass fiber, it does not mention the silanol group (Si-OH) content or the dielectric loss tangent. Since the fiber is produced using a sol-gel process, the moisture and silanol groups attached to the gel are not separated.

[0017] Second, although the diffuse reflection IR method is used in Patent Document 1, the influence of coexisting water is not considered and only the 3660 cm -1 The water content was determined by the peak of silanol, and no distinction was made between the water content and the silanol content contained in the silica glass (the OH groups of silanol and the OH groups derived from H2O were not distinguished).

[0018] Third, Patent Document 1 shows the relationship between the moisture content and the dielectric loss tangent in silica glass fiber, but does not describe the silanol content. Regarding the dielectric loss tangent, since the value is measured on a printed circuit board using silica glass fiber and PTFE, the correlation between the silanol content and the dielectric loss tangent of the glass fiber is not clear.

[0019] Fourth, although it is described that the yarn strength (tensile strength) decreases rapidly when the yarn is fired at 1200° C. or higher, there is no description of strength recovery.

[0020] It is known that for quartz glass, the hydroxyl group (OH group) amount remaining in the glass is usually different due to manufacturing method or heat treatment, and the difference of OH concentration can bring the difference of various physical properties to silica glass (non-patent literature 1). However, it is unknown to promote the dielectric loss tangent of the quartz glass cloth or silica powder obtained by the method other than the sol-gel method by high-temperature treatment. In addition, although the quartz glass and silica powder after the known high-temperature treatment can increase (non-patent literature 2) in the strain (distortion) of the surface layer, above-mentioned patent documentation 1 is not recorded at all in the surface layer of the silica glass obtained by high-temperature heat treatment and produces strain.

[0021] When the strength of the heat-treated quartz glass cloth is measured, the strength is significantly reduced due to the surface strain described above. Therefore, resin substrates using heat-treated quartz glass cloth or silica powder have not been put to practical use.

[0022] As described above, conventional technology has not been able to produce a quartz glass cloth having a dielectric loss tangent close to the level of dielectric loss tangent inherent in quartz. Therefore, even if an organic resin with a low dielectric loss tangent is used, it is still not enough to reduce the dielectric loss tangent of the organic resin substrate itself. This has led to the problem of difficulty in producing an ideal substrate with very low transmission loss even in high-speed communications using millimeter waves, etc.

[0023] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a resin substrate using quartz glass cloth having a low dielectric loss tangent and excellent tensile strength.

[0024] Technical means to solve technical problems

[0025] In order to solve the above technical problems, the present invention provides a low-dielectric resin substrate, which is a low-dielectric resin substrate obtained by compounding an organic resin with a heat-treated annealed quartz glass cloth, characterized in that the dielectric loss tangent of the annealed quartz glass cloth at 10 GHz is less than 0.0010, and the weight per unit area of the cloth (g / m 2 ) has a tensile strength of 1.0 N / 25 mm or more.

[0026] According to the low-dielectric resin substrate of the present invention, it is possible to provide a resin substrate using annealed quartz glass cloth having a low dielectric loss tangent and excellent tensile strength.

[0027] In this case, it is preferred that the silica powder having a dielectric loss tangent of less than 0.0010 at 10 GHz and an average particle size of 0.1 to 30 μm is further contained.

[0028] With such a low-dielectric resin substrate, the dielectric loss tangent of the silica powder filled therein is also low, so the expansion coefficient and elastic modulus of the substrate can be adjusted, and the dielectric properties can be significantly improved.

[0029] In the present invention, the organic resin is preferably a thermoplastic resin, and more preferably the thermoplastic resin is one or more thermoplastic resins selected from polyphenylene ether, polyetheretherketone, polyetherketone, polyethersulfone, and fluororesin.

[0030] In addition, in the present invention, it is also preferred that the organic resin is a thermosetting resin, and it is more preferred that the thermosetting resin is one or more thermosetting resins selected from epoxy resins, allylated epoxy resins, allylated polyphenylene ether resins, maleimide resins, bismaleimide resins, cyanate resins, and cyclopentadiene-styrene copolymer resins.

[0031] In the low-dielectric resin substrate of the present invention, the above-mentioned resin can be preferably used as the organic resin to be composited with the annealed quartz glass cloth.

[0032] Effects of the Invention

[0033] As described above, if it is a low-dielectric resin substrate of the present invention, it is possible to provide a resin substrate using annealed quartz glass cloth with a low dielectric loss tangent and excellent tensile strength. Furthermore, it is possible to use a silica powder with a dielectric loss tangent of less than 0.0010 at 10 GHz and an average particle size of 0.1 to 30 μm, adjust the expansion coefficient and elastic modulus of the substrate, and make a resin substrate with significantly improved dielectric properties. In addition, since the quartz glass cloth used in the present invention itself has a low dielectric loss tangent and excellent tensile strength, there are more choices of organic resins that can be combined. In this way, since the low-dielectric resin substrate of the present invention has a low dielectric loss tangent and excellent tensile strength, it can be suitably used for high-speed communication substrates and antenna substrates with less transmission loss even when using high frequencies such as millimeter waves, and can also cope with high-density mounting or ultra-thinning of circuit substrates. In the field of high-speed communications such as 5G, it has high utilization value. DETAILED DESCRIPTION

[0034] If the dielectric properties of existing quartz glass cloth or silica powder, particularly the dielectric loss tangent, can be reduced to the level of quartz glass itself, they could be used in a wide range of applications, such as sealing materials for high-speed communication semiconductors, which are expected to see significant growth in the future, and as reinforcing materials or fillers for high-speed communication substrates and antenna substrates.

[0035] The inventors of the present application conducted research aimed at lowering dielectric constants and discovered that heating quartz glass cloth or silica powder to a temperature of 500°C to 1500°C is effective in reducing the dielectric loss tangent. Furthermore, by slightly etching the surface of the annealed quartz glass cloth or silica powder, the surface of the annealed glass cloth or powder can be hardened, thereby improving adhesion to resin. Furthermore, the inventors discovered that the tensile strength of the annealed quartz glass cloth is significantly increased, leading to the completion of the present invention.

[0036] That is, the present invention is a low-dielectric resin substrate obtained by compounding an organic resin with annealed quartz glass cloth that has been heat-treated at 500°C to 1500°C, wherein the annealed quartz glass cloth has a dielectric loss tangent of less than 0.0010 at 10 GHz and a weight per unit area (g / m2) of the cloth. 2 ) has a tensile strength of 1.0 N / 25 mm or more.

[0037] Furthermore, the inventors of the present application have discovered that by further blending silica powder having an average particle size of 0.1 to 30 μm and a dielectric loss tangent (10 GHz) of less than 0.0010 into a low-dielectric resin substrate obtained by compounding an organic resin with annealed quartz glass cloth, the expansion coefficient and elastic modulus of the substrate can be adjusted to produce a resin substrate with significantly improved dielectric properties.

[0038] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0039] The present invention relates to a low-dielectric resin substrate using annealed quartz glass cloth with a low dielectric loss tangent, exhibiting excellent dielectric properties and mechanical strength, such as tensile strength. The low-dielectric resin substrate of the present invention enables the production of an ideal substrate with very low transmission loss for high-speed communications using millimeter waves and other technologies.

[0040] The low dielectric resin substrate of the present invention is (B) an organic resin and (A) a dielectric loss tangent of less than 0.0010 at 10 GHz and a weight per unit area of the cloth (g / m 2 ) is composited with annealed quartz glass cloth having a tensile strength of 1.0 N / 25 mm or more. (C) An additive such as a filler or coupling agent may be further included as needed. Here, "composite" means that the glass cloth and the organic resin are integrally connected and inseparable, specifically, it refers to a state in which the annealed quartz glass cloth is embedded in the organic resin. Examples of such resin substrates include: resin substrates obtained by curing a prepreg obtained by impregnating annealed quartz glass cloth with an organic resin; or resin substrates obtained by sandwiching annealed quartz glass cloth with a thermoplastic resin and hot pressing.

[0041] Hereinafter, the low-dielectric resin substrate will be described in detail.

[0042] [(A) Annealed quartz glass cloth]

[0043] The annealed quartz glass cloth used in the present invention is obtained by heat treating quartz glass cloth (500-1500°C). The dielectric loss tangent (10 GHz) is less than 0.0010, preferably 0.0008 or less, more preferably 0.0005 or less, and even more preferably 0.0002 or less. The weight per unit area of the cloth (g / m 2 ) has a tensile strength of 1.0 N / 25 mm or more, and preferably has a weight per unit area of ​​the cloth (g / m 2 ) has a tensile strength of 1.2N / 25mm or more.

[0044] In the present invention, annealed quartz glass cloth refers to annealed quartz glass cloth obtained by subjecting quartz glass cloth to a heat treatment at a temperature of 500°C to 1500°C. As described below, this refers to annealed quartz glass cloth obtained by subjecting the quartz glass cloth itself to a specific heat treatment. Therefore, it is clearly different from quartz glass obtained by subjecting the glass cloth itself to a high-temperature treatment during the manufacturing process, such as so-called fused silica or quartz glass obtained by subjecting sol-gel silica to a high-temperature treatment.

[0045] As described below, the dielectric loss tangent can be measured at a frequency of 10 GHz using a SPDR (Split Post Dielectric Resonators) dielectric resonator for dielectric constant measurement, and the tensile strength can be measured in accordance with "7.4 Tensile Strength" of JIS R3420:2013 "Glass Fiber General Test Methods".

[0046] <Quartz glass cloth>

[0047] The material of the quartz glass cloth used in the present invention can mainly include naturally occurring quartz with few impurities and synthetic quartz using silicon tetrachloride as a raw material.

[0048] The SiO2 content of the quartz glass material is preferably 99% by mass or more, more preferably 99.5% by mass or more. If the SiO2 content is such, the quartz glass cloth after heat treatment tends to have a low dielectric loss tangent comparable to that of the original quartz.

[0049] The impurity concentration in the quartz glass material is preferably such that the total of alkali metals Na, K, and Li is 10 ppm or less, B is 1 ppm or less, and P is 1 ppm or less. To prevent damage caused by radiation, the contents of U and Th are 0.1 ppb or less.

[0050] Quartz glass cloth can be produced by using a quartz ingot obtained by the following production method as a raw material, producing filaments or yarns, and weaving the filaments or yarns.

[0051] Quartz ingots can be produced by the following methods: electric melting method or flame melting method using naturally occurring quartz as raw material; direct synthesis method, plasma synthesis method, soot method using silicon tetrachloride as raw material; or sol-gel method using alkyl silicate as raw material.

[0052] For example, the quartz wire having a diameter of 100 to 300 μm used in the present invention can be produced by melting an ingot at 1700 to 2300° C., and then stretching and winding the ingot.

[0053] In this specification, a filament-shaped single fiber obtained by stretching the above-mentioned quartz filament is defined as a quartz glass filament, a product obtained by bundling quartz glass filaments is defined as a quartz glass strand, and a product obtained by bundling and further twisting quartz glass filaments is defined as a quartz glass yarn.

[0054] In the case of quartz glass filaments, the diameter is preferably 3 μm to 20 μm, more preferably 3.5 μm to 9 μm. Examples of methods for producing quartz glass filaments include methods of extending the quartz filaments by electric melting or oxyhydrogen flame, but are not limited to these methods as long as the diameter of the quartz glass filaments is 3 μm to 20 μm.

[0055] The quartz glass filaments are bundled in a number of 10 to 400 to produce a quartz glass filament bundle, and more preferably, the number of the quartz glass filaments is 40 to 200.

[0056] Furthermore, the quartz glass cloth used in the present invention can be produced by weaving the above-mentioned quartz glass yarns or filaments.

[0057] In the present invention, the twist count of the quartz glass yarn is not particularly limited. A lower twist count facilitates thinning of the glass cloth during the fiber-opening process after fabrication, and also tends to reduce air permeability. Furthermore, a higher twist count improves yarn bundling, making breakage and fuzzing less likely to occur.

[0058] The quartz glass yarn is woven to prepare a glass cloth with a warp and weft weaving density of 10 yarns / 25 mm or more, preferably 30 yarns / 25 mm or more, more preferably 50 yarns / 25 mm or more, and 120 yarns / 25 mm or less, preferably 110 yarns / 25 mm or less, more preferably 100 yarns / 25 mm or less.

[0059] The method for weaving the glass cloth is not particularly limited, and examples thereof include a method using a rapier loom, a method using a shuttle loom, and a method using an air jet loom.

[0060] When making cloth, in order to prevent the yarn from fuzzing or breaking, a yarn with a sizing agent coated on the surface of the yarn is usually used for weaving. The sizing agent contains starch as the main component of the film-forming agent.

[0061] The sizing agent may contain other ingredients besides starch, such as a cationic vinyl acetate copolymer emulsion. Examples of other ingredients include lubricants, emulsifiers, cationic softeners, antistatic agents, silane coupling agents, and preservatives. Furthermore, a small amount of alcohols such as methanol, ethanol, and isopropyl alcohol, or other organic solvents, may be added to the quartz glass fiber sizing agent of the present invention.

[0062] Furthermore, flattening glass cloth (grey cloth) with an organic substance exhibiting lubricant properties attached to the glass filaments, or with an adhesive or paste used in weaving conventional glass cloth attached to the glass filaments, or a combination of these methods, is particularly effective in reducing the thickness of the glass cloth, increasing the amount of glass that can be filled without increasing the thickness of the glass cloth. Furthermore, surface treatment after fiber spreading and further fiber spreading can further increase the gaps between the bundled filaments.

[0063] Here, if the fiber bundle is widened by fiber opening, the impregnation of the resin varnish can be improved, resulting in a more uniform distribution of the glass and matrix resin, which can also provide advantages such as improved heat resistance. In addition, since the distribution of the glass fibers is more uniform, it can also achieve advantages such as improved laser processability (uniformity of pore size distribution, processing speed, etc.), which is preferred.

[0064] Methods for removing sizing agents after weaving include common methods such as dissolution with a solution and incineration by heating. A particularly preferred method involves using a sizing agent composed of water-soluble fibers and dissolving and removing it with hot water. This method not only removes the sizing agent but also spreads the filaments that make up the glass cloth, effectively opening them. Furthermore, unexpectedly, the presence of minute gaps created by the removal of the sizing agent causes the spread filaments to curve into a wavy shape. This results in a smooth cloth with a relatively uniform density and minimal surface irregularities, even with a low weight per unit area or a low number of filaments.

[0065] When thermal cleaning such as heat treatment is performed after knitting, the removal can be achieved by storing the fabric at a temperature of 200° C. or higher and lower than 500° C. for 24 to 100 hours.

[0066] The weight per unit area of the quartz glass cloth in this state (g / m 2 ) has a tensile strength of 1.0 N / 25 mm or more, which is a level that will not cause problems in the operation of subsequent steps.

[0067] The currently available quartz glass cloth obtained by this manufacturing method has dielectric properties superior to those of LE glass, a low-dielectric glass known as LE glass. Its dielectric loss tangent is 0.0010 or higher, an order of magnitude greater than the dielectric loss tangent of 0.0001 possessed by conventional quartz.

[0068] The inventors of the present application have discovered that annealed quartz glass cloth, which has been subjected to a high-temperature treatment at a temperature of 500°C or higher to remove the strain layer on the surface of the fibers constituting the cloth, has a dielectric loss tangent of less than 0.0010 at 10 GHz in the high-frequency region and a weight per unit area (g / m2). 2 ) has a tensile strength of 1.0 N / 25 mm or more. By using this annealed quartz glass cloth, a resin substrate with excellent dielectric properties can be manufactured.

[0069] According to IPC-4412B (Appendix II), the weight per unit area of the fabric (g / m 2 ) or fabric thickness (mm) varies depending on the type of fabric, and the weight per unit area of fabric (g / m 2 ) in the range of 9~270(g / m 2 ) range, and the cloth thickness (mm) is in the range of 0.011 to 0.260 (mm). The tensile strength (N / 25mm) of the cloth also varies depending on the type of cloth. Therefore, as shown in the following formula (1), the tensile strength of the quartz glass cloth is the measured value of the tensile strength (N / 25mm) divided by the weight per unit area of the cloth (g / m 2 ) and the value obtained.

[0070] Tensile strength (N / 25mm) ÷ fabric weight per unit area (g / m 2 )≥1.0(1)

[0071] <Method for Manufacturing Annealed Quartz Glass Cloth>

[0072] In the present invention, annealed quartz glass cloth (low-dielectric quartz glass cloth) is used. This is obtained by heating the quartz glass cloth at high temperatures to remove silanol groups present in the quartz glass, dissolving and removing the strain layer generated on the surface of the quartz glass, and then treating the quartz glass surface with a coupling agent or the like as needed.

[0073] Furthermore, the SiO 2 content of the annealed quartz glass cloth is preferably 99% by mass or more, and more preferably 99.5% by mass or more.

[0074] (Heat treatment process)

[0075] Regarding the heating temperature for removing silanol groups from the quartz glass, the quartz glass cloth is heat-treated at a temperature of 500°C to 1500°C, preferably 500°C to 1300°C, and more preferably 700°C to 1000°C. As a heating method, the woven quartz glass cloth can be placed in an electric furnace, a muffle furnace, or the like in a state of being wound around a quartz tube or a metal tube and heated at the above-mentioned temperature. However, the heating method and the shape of the quartz glass cloth to be treated are not limited to this.

[0076] The heat treatment time of the quartz glass cloth varies depending on the heating temperature, but is preferably 1 minute to 72 hours, more preferably 10 minutes to 24 hours, and even more preferably 1 hour to 12 hours from a practical point of view.

[0077] In addition, the cooling to room temperature after heating can be slow cooling or fast cooling, because the quartz glass of molten state is partially crystallized due to condition sometimes, therefore preferably heating temperature or cooling condition are optimized.As heating atmosphere, can be in air, in inert gases such as nitrogen, can be at normal pressure, vacuum or under reduced pressure, is not particularly limited, but consider cost etc., usually carry out in air at normal pressure.About the reduction degree based on heat-treated silanol group, infrared spectroscopy etc. can be utilized to analyze, thus confirm whether required dielectric properties have been reached.By this operation, dielectric loss tangent can be made less than 0.0010, preferably below 0.0008, more preferably below 0.0005, further preferably below 0.0002, close to the original grade of quartz.

[0078] As a method for analyzing silanol groups, in addition to infrared spectroscopy, there are also solid-state29 Si NMR analysis method. Solid 29 Although Si NMR has its own drawbacks, such as complicated analysis operations and low efficiency, it is a preferred analysis method because it can quantify silanol groups on the surface and inside of quartz glass cloth.

[0079] Here, the reason for removing the silanol groups in the quartz glass will be described.

[0080] It is known that in the GHz band, dipoles generated by polarization respond to electric fields, causing dielectric (induced dielectric). Therefore, the key to achieving low dielectric properties in the GHz band lies in reducing polarization in the structure.

[0081] The dielectric constant is expressed using the Clausius-Mossotti equation below, with molar polarizability and molar volume as factors. Therefore, the key to lowering the dielectric constant lies in reducing polarization and increasing molar volume.

[0082] Dielectric constant = [1 + 2 (ΣPm / ΣVm)] / [1 - (ΣPm / ΣVm)]

[0083] (Pm: molar polarizability of the atomic group, Vm: molar volume of the atomic group)

[0084] Furthermore, the dielectric loss tangent (tanδ) represents the delay in the dielectric response to an AC electric field. In the GHz band, this delay is primarily due to the orientational relaxation of dipoles. Therefore, to reduce the dielectric loss tangent, one approach is to eliminate dipoles (creating a nearly non-polarized structure).

[0085] In summary, as a method for achieving low dielectric properties of silica glass in the GHz band, the present invention suppresses the concentration of silanol groups, which are polar groups, to a low level.

[0086] Based on the above perspectives, in the present invention, the silanol group (Si-OH) concentration in the heat-treated quartz glass cloth is preferably 300 ppm or less, preferably 250 ppm or less, and more preferably 100 ppm or less. To dissolve and remove the strain layer on the surface of the quartz glass in the strength recovery step described later, the lower the silanol group concentration in the heat-treated quartz glass cloth, the better.

[0087] As a result, an annealed quartz glass cloth with a lower dielectric loss tangent can be obtained. As described above, the silanol group (Si-OH) concentration in the finally obtained annealed quartz glass cloth is preferably 300 ppm or less, more preferably 250 ppm or less, and even more preferably 100 ppm or less.

[0088] It is preferred to use a solid that can quantify the silanol groups on the surface and inside of the quartz glass cloth. 29 Si NMR was used to measure the silanol concentration in the heat-treated and annealed quartz glass cloth. This allowed us to accurately understand the silanol concentration that affects the dielectric loss tangent. 29 The silanol concentration in quartz glass by Si NMR can be measured by a known method such as the DD (Dipolar Decoupling) / MAS (Magic Angle Spinning) method (for example, see Japanese Patent Application Publication Nos. 2013-231694 and 2017-3429).

[0089] By the above-mentioned heat treatment step, the dielectric loss tangent (10 GHz) of the quartz glass cloth can be set within the above-mentioned range.

[0090] However, the weight per unit area (g / m2) of the quartz glass cloth obtained by heat treatment at high temperature to reduce the dielectric constant is 2 ) is less than 0.5 (N / 25mm), which is significantly reduced. Therefore, subsequent processes such as coupling agent treatment or resin impregnation for producing prepreg cannot be directly carried out, and quartz glass cloth in this state cannot be used in practice.

[0091] Therefore, the present invention also aims to restore the strength of the quartz glass cloth after heat treatment by immersion in an etching solution.

[0092] (Strength recovery process)

[0093] This strength recovery step is a step of improving the tensile strength of the quartz glass by dissolving and removing the strain layer on the surface of the quartz glass generated during the high-temperature treatment.

[0094] The inventors of the present application studied the decrease in strength after heat treatment and found that after high-temperature heat treatment, a slight strain remains in the surface layer of the quartz glass cloth, which becomes a starting point for fracture. They further found that in order to restore strength, the strength can be restored by simply removing this strained layer.

[0095] The strained layer of quartz glass cloth can be easily removed by immersing it in an etching solution. The etching solution is not particularly limited as long as it can remove the strained layer. Examples of acidic aqueous solutions include hydrofluoric acid, ammonium fluoride (NH4F·HF) aqueous solutions, and potassium fluoride (KHF2) aqueous solutions. Alkaline aqueous solutions selected from ammonium fluoride, sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia, and alkaline electrolyzed water are also acceptable. From the perspective of the operating environment and wastewater treatment, alkaline electrolyzed water is more preferred.

[0096] As long as the strain layer can be removed, the etching treatment conditions of the quartz glass cloth after heat treatment are not particularly limited, but the preferred temperature is room temperature (23°C) to 100°C, more preferably 40°C to 80°C. The treatment time depends on the etching rate of the quartz surface at the treatment temperature, so it is not particularly limited. The treatment temperature is from room temperature to 90°C, preferably 40°C to 80°C. The lower the temperature of the etching solution, the less likely it is to be etched, and the higher the temperature, the faster the etching rate. However, in terms of practicality, the temperature at which the treatment is completed within a treatment time of more than 10 minutes to 168 hours is preferred. The treatment time is preferably 1 hour to 72 hours, more preferably 10 hours to 24 hours. In addition, even under atmospheric pressure or a pressurized atmosphere, the treatment can be carried out within the above-mentioned temperature and time ranges. As long as the strain layer can be removed, the pH value of the etching solution is not particularly limited, and can be adjusted as needed by adding acid or alkali.

[0097] Specifically, as for the alkaline solution, if the pH value is 8.0 or higher, the etching effect on silica glass is sufficient and improvement in tensile strength is confirmed. The pH value is preferably 10.0 to 13.5, and more preferably 11.0 to 13.0.

[0098] As the alkaline etching solution, an alkaline aqueous solution having a pH of 11 or higher is preferably used, and alkaline electrolyzed water having a pH of 12 or higher is more preferably used.

[0099] The etching process is not particularly limited as long as the strained layer can be removed, but from the perspective of improving the productivity of the quartz glass cloth, it is preferably performed as a continuous process.

[0100] The strain layer can be removed by directly immersing the resulting roll of quartz glass cloth wrapped around a metal tube or quartz tube in an etching tank filled with an etchant, or by sequentially immersing the roll in multiple etching tanks filled with different etchants. The treatment method is not limited as long as the specified temperature and time are met. The metal tube or quartz tube can be perforated to facilitate the penetration of the etchant into the wound quartz glass cloth.

[0101] Alternatively, etching can be performed by continuously unwinding a quartz glass cloth wound around a metal tube or a quartz tube and pulling it out, passing it through the etching tank for a predetermined period of time. This method is preferred for uniform etching.

[0102] In order to smoothly carry out etching, an ultrasonic generator can also be set in the etching tank to emit ultrasonic waves to impart vibration while etching. By applying ultrasonic waves, etching can be processed more uniformly, so it is a preferred method.

[0103] After etching, the quartz glass cloth is further cleaned in a cleaning bath of pure water or ion-exchanged water at room temperature to 100°C in order to remove impurities such as alkali metals from the roll state described above, or to remove impurities such as alkali metals while continuously unwinding and pulling out the quartz glass cloth. When alkaline electrolyzed water is used as the etching solution, the cleaning step can be omitted.

[0104] After cleaning, it is best to heat and dry the moisture attached to the quartz glass cloth in order to transfer it to subsequent steps such as coupling agent treatment.

[0105] Through the strength recovery process, a low dielectric loss tangent and high tensile strength annealed quartz glass cloth can be obtained, wherein the dielectric loss tangent is less than 0.0010 and the weight per unit area of the cloth (g / m 2 ) has a tensile strength of 1.0 (N / 25mm) or more.

[0106] (Coupling agent treatment process)

[0107] It is preferable to further perform a coupling agent treatment on the surface of the quartz glass cloth after the etching treatment and the moisture adhering to the quartz glass cloth is dried by heating.

[0108] By coating the surface of the quartz glass cloth with a silane coupling agent, the lubricity or wettability of the glass cloth or yarn is improved, and the tensile strength of the glass cloth is increased. By treating the surface of the etched quartz glass cloth with a silane coupling agent, the weight per unit area (g / m 2 ) of the tensile strength becomes 1.5 (N / 25mm) or more, and by selecting the most suitable silane coupling agent, the weight per unit area of the quartz glass cloth (g / m 2 ) has a tensile strength of 2.0 (N / 25mm) or more.

[0109] In addition, when manufacturing prepreg etc., in order to make the adhesion between resin and glass cloth surface firm, carry out surface treatment utilizing silane coupling agent.Regarding surface treatment, after high temperature treatment and etching treatment of quartz glass cloth, quartz glass cloth is cleaned, and then the surface of glass cloth is covered with silane coupling agent.As silane coupling agent, known silane coupling agent can be used, preferably alkoxysilane, more preferably selected from 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, N-2-(aminoethyl)-3-aminopropyl trimethoxysilane, N-2-(aminoethyl)-3-aminopropyl triethoxysilane, N-phenyl-3-aminopropyl trimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl triethoxysilane, p-phenylyl trimethoxysilane, trifluoropropyl trimethoxysilane group consisting of one or more.

[0110] The concentration of the silane coupling agent is typically between 0.1% and 5% by mass as a dilute solution, with concentrations between 0.1% and 1% being particularly effective. Using annealed quartz glass cloth not only allows the silane coupling agent to adhere evenly, providing more uniform protection to the glass cloth surface and facilitating handling, but also improves the tensile strength of the quartz glass cloth and allows for uniform and smooth application to resins used in prepregs and the like.

[0111] [(B) Organic resin]

[0112] The organic resin to be composited with the annealed quartz glass cloth is not particularly limited, and both thermosetting resins and thermoplastic resins can be used.

[0113] As thermoplastic resin, polyphenylene ether, polyetheretherketone, polyetherketone, polyethersulfone, fluororesin etc. can be illustrated as representative examples.Wherein, from the perspective of low dielectric properties, preferred fluororesin.As fluororesin, preferably at least one in the group consisting of polytetrafluoroethylene [PTFE], polychlorotrifluoroethylene [PCTFE], ethylene [Et]-TFE copolymer [ETFE], Et-chlorotrifluoroethylene [CTFE] copolymer, CTFE-TFE copolymer, TFE-HFP copolymer [FEP], TFE-PAVE copolymer [PFA] and polyvinylidene fluoride [PVdF] is selected from.

[0114] Examples of the thermosetting resin include epoxy resins, allylated epoxy resins, allylated polyphenylene ether resins, maleimide resins, bismaleimide resins, cyanate resins, and cyclopentadiene-styrene copolymer resins.

[0115] Among them, the bismaleimide resin represented by the following general formula (1) can be preferably used for lowering the dielectric constant.

[0116]

[0117] In the formula, A independently represents a tetravalent organic group containing an aromatic ring or an aliphatic ring. B is a divalent alkylene chain having 6 to 18 carbon atoms and optionally containing a heteroatom and having an aliphatic ring. Q independently represents a linear alkylene group having 6 or more carbon atoms. R independently represents a linear or branched alkyl group having 6 or more carbon atoms. n represents a number from 1 to 10. m represents a number from 0 to 10.

[0118] Representative bismaleimide resins include the SLK-2000 series (manufactured by Shin-Etsu Chemical Co., Ltd.), SLK-6895 (manufactured by Shin-Etsu Chemical Co., Ltd.), and SLK-3000 (manufactured by Shin-Etsu Chemical Co., Ltd.). Furthermore, thermosetting cyclopentadiene-styrene copolymer resins can also be used as high-heat-resistant resins. A representative example is the SLK-250 series (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0119] [(C) Filler]

[0120] In the present invention, fillers can be included as needed. As fillers, known fillers such as silicon dioxide can be used, preferably the following low-dielectric silicon dioxide powder. By including fillers, the expansion coefficient and elastic modulus of the substrate can be adjusted, and dielectric properties can also be adjusted.

[0121] (Low dielectric silica powder)

[0122] The silica powder that can be used in the present invention has an average particle size of 0.1 to 30 μm, and a dielectric loss tangent (10 GHz) of preferably less than 0.0010, more preferably 0.0005 or less. The silica powder preferably contains a metal selected from aluminum, magnesium, and titanium and / or its oxide in an amount of 200 ppm or less, calculated as a metal, in a portion or the entirety of the interior and surface thereof, and the content of each of alkali metals and alkaline earth metals is preferably 10 ppm or less.

[0123] In the present invention, the maximum particle size and the average particle size can be measured using a laser diffraction particle size distribution analyzer (e.g., SALD-3100: manufactured by Shimadzu Corporation). The mass average value D50 (i.e., the particle size or median size at which the cumulative mass is 50%) in the particle size distribution measurement based on the laser diffraction method can be calculated and used as the average particle size.

[0124] Furthermore, silica powders containing less than 1 ppm of B, less than 1 ppm of P, and less than 0.1 ppb of U and Th can also be used as low-dielectric silica powders. Preferred silica powders for use in the present invention include those obtained by heating at a temperature of 500°C to 1500°C to reduce the dielectric constant, and those obtained by etching the surface of the silica powder with an alkaline aqueous solution, more preferably alkaline electrolyzed water having a pH of 12 or higher.

[0125] The preferred silica powder in the present invention is one having a silanol group (Si-OH) content of 300 ppm or less. When the content is less than this, the dielectric loss tangent is sufficiently low. The heat treatment reduces the silanol group content of the silica powder to 300 ppm or less, preferably 280 ppm or less, and more preferably 150 ppm or less, thereby forming a silica powder having a low dielectric loss tangent.

[0126] The low dielectric silica powder preferably used in the present invention is a silica powder having an average particle size of 0.1 to 30 μm and preferably a maximum particle size of 100 μm or less. When used as a filler for high-speed communication substrates, the average particle size is 0.1 to 5 μm and the maximum particle size is 20 μm, and more preferably the average particle size is 0.1 to 3 μm and the maximum particle size is 10 μm or less.

[0127] The silica powder can be heat-treated at 500°C to 1500°C to reduce its dielectric loss tangent (10 GHz) to less than 0.0010, preferably 0.0005 or less, and more preferably 0.0004 or less.

[0128] Heat-treating silica powder at temperatures above 500°C may produce a strained layer on the particle surface, reducing strength. Therefore, the silica powder used in the present invention is preferably one from which this strained layer has been removed. The strained layer can be easily removed by immersing the silica powder in an etching solution, similar to the quartz glass cloth described above.

[0129] Furthermore, when a prepreg is produced by coating the surface of the silica powder with a silane coupling agent or the like, the adhesion between the resin and the glass cloth or the surface of the silica powder can be strengthened.

[0130] As the silane coupling agent, a known silane coupling agent used for the above-mentioned quartz glass cloth can be used.

[0131] The amount of silica powder added is preferably 0 to 1000 parts by mass, more preferably 10 to 950 parts by mass, and particularly preferably 50 to 850 parts by mass relative to the total amount of 100 parts by mass of the resin components. Depending on the type and use of the organic resin, silica powder may not be added, but sometimes the coefficient of thermal expansion (CTE) of the cured product becomes larger and sufficient strength cannot be obtained. If it is less than 1000 parts by mass, it will not lose flexibility or produce a poor appearance when manufacturing the prepreg. In addition, when the silica powder can be mixed in a small amount, it is preferably contained in the range of 10 to 90% by mass of the entire resin, and particularly preferably contained in the range of 35 to 85% by mass.

[0132] By using the silica powder together with the quartz glass cloth, the silica powder is suitable as a filler for substrates such as high-speed communication substrates and antenna substrates.

[0133] To improve fluidity and processability, silica powders having different average particle sizes may be mixed with the silica powder.

[0134] [Other ingredients]

[0135] In addition to the above components (A) to (C), the low dielectric resin substrate of the present invention may further contain the above silane coupling agent and, if necessary, an acid, a dye, a pigment, a surfactant, a flame retardant, an adhesive aid, and other optional components.

[0136] [Low dielectric resin substrate]

[0137] As the low dielectric resin substrate of the present invention, the following first to third aspects can be cited, but the present invention is not limited thereto.

[0138] First, the annealed quartz glass cloth having a low dielectric loss tangent, a prepreg obtained by impregnating the glass cloth with a resin, and a resin substrate obtained by pressurizing and heating the glass cloth prepreg.

[0139] Second, a resin substrate obtained by compounding annealed quartz glass cloth and an organic resin by pressurizing and heating them.

[0140] Thirdly, there is a low dielectric resin substrate related to annealed quartz glass cloth, a prepreg obtained by impregnating the glass cloth with a resin containing low dielectric loss tangent silica powder, and a resin substrate obtained by compositely forming the glass cloth prepreg by pressurizing and heating.

[0141] In addition, the present invention relates to a circuit board material such as a prepreg and a laminate with a low dielectric loss tangent, and further relates to a multilayer printed substrate and a printed substrate with a low dielectric constant and a low dielectric loss tangent that have excellent high-frequency signal transmission characteristics, as well as a resin composition, prepreg, laminate, etc. used to manufacture the printed substrate.

[0142] The low dielectric resin substrate (organic resin substrate) of the present invention comprises the above-mentioned (A) to (B) components as essential components. Although the (C) component is an optional component, it is preferably filled with the (C) component from the perspective of controlling the thermal expansion coefficient or strength of the organic resin. When the (C) component is contained, an organic resin prepreg can be produced and made into a (laminated) substrate. The low dielectric resin substrate can be made into an organic resin laminated substrate or an organic resin-coated metal laminated substrate according to its use. In the low dielectric resin substrate of the present invention, the thickness of the insulating layer can be appropriately selected according to its use, etc., and is not particularly limited, but is preferably 20 to 2000 μm, more preferably 50 to 1000 μm.

[0143] -Method for manufacturing low-dielectric resin substrate-

[0144] The low dielectric resin substrate of the present invention can be produced by a conventional method using the above-mentioned components (A) to (B) and, if necessary, other components such as the component (C).

[0145] When organic resin (matrix resin) can be dissolved / dispersed in solvent, low dielectric resin substrate can be obtained in the following manner: preparation comprises the organic resin composition of the composition except (A) component, after using the organic resin composition to obtain prepreg, the prepreg is pressurized, heat-cured (first manufacturing method). When organic resin cannot be dissolved / dispersed in solvent or is difficult to dissolve, low dielectric resin substrate (second manufacturing method) can also be made by heating and pressing the organic resin film of film and annealed quartz glass cloth and copper foil as needed. Below, these manufacturing methods are described.

[0146] (First Manufacturing Method)

[0147] In the first manufacturing method, the organic resin composition containing the above-mentioned (B) component and the (C) component as needed is impregnated in the annealed quartz glass cloth as the (A) component under the state of being dissolved / dispersed in the solvent, then, the solvent is evaporated from the glass cloth to remove it, thereby obtaining a prepreg. The obtained prepreg is solidified by pressurization, heating, etc., thus enabling the low dielectric resin substrate of the present invention to be obtained. Here, relative to 100 parts by mass of (B) component, the filler (inorganic filler, etc.) of (C) component is preferably less than 1000 parts by mass, more preferably in the range of 10 to 950 parts by mass, particularly preferably in the range of 50 to 850 parts by mass.

[0148] -Solvents-

[0149] When manufacturing a low-dielectric resin substrate using the first manufacturing method, the solvent is not particularly limited as long as it can dissolve / disperse the organic resin composition and evaporate at a temperature that maintains the composition in an uncured or semi-cured state. For example, solvents with a boiling point of 50-200°C, preferably 80-150°C, are used. Specific examples of the solvent include non-polar hydrocarbon solvents such as toluene, xylene, hexane, and heptane; and polar hydrocarbon solvents such as ethers and esters. The amount of solvent used is not particularly limited as long as it can dissolve / disperse the organic resin composition and allow the resulting solution or dispersion to be impregnated into the annealed quartz glass cloth. The amount is preferably 10-200 parts by mass, more preferably 20-100 parts by mass, relative to 100 parts by mass of the organic resin composition.

[0150] For example, the organic resin composition can be prepared in the following manner.

[0151] First, various components soluble in an organic solvent, such as an organic resin and, if necessary, additives such as a crosslinking agent and a reaction initiator, are placed in an organic solvent to dissolve them. Heating may be performed as needed. Components insoluble in the organic solvent, such as an inorganic filler, are then added and dispersed using a ball mill, bead mill, planetary mixer, roller mill, or the like until a desired dispersion state is achieved, thereby preparing a varnish-like resin composition.

[0152] Alternatively, the inorganic filler is mixed and dispersed in the organic resin using a disperser such as a planetary mixer or a roll mill, and then the organic resin mixture, a crosslinking agent, a reaction initiator, etc. are added to the organic solvent using a dissolving device such as a ball mill, a bead mill, or a stirring device manufactured by Satake Chemical Equipment Mfg., Ltd., to prepare a varnish-like resin composition.

[0153] Furthermore, when blending, it is preferred to pre-treat the inorganic filler with a coupling agent such as a silane or titanate, or a surface treatment agent such as an organosilicon oligomer, or to integrally blend the filler. Alternatively, a surface treatment agent (such as a silane coupling agent) can be pre-blended into the organic resin composition instead of pre-treating the glass cloth.

[0154] The resin composition in the final varnish preferably accounts for 30 to 90% by mass of the entire varnish, more preferably 40 to 80% by mass, and even more preferably 50 to 70% by mass. By setting the resin composition content in the varnish to 30 to 90% by mass, good coating properties can be maintained, resulting in a prepreg with an appropriate amount of resin composition adhered.

[0155] -Prepreg-

[0156] The solution or dispersion (varnish) of the organic resin composition is prepared by, for example, impregnating annealed quartz glass cloth with the solution or dispersion, or applying the solution or dispersion to annealed quartz glass cloth by spraying, extrusion, or the like, followed by semi-curing (B-stage) by removing the solvent in a drying furnace preferably at 50 to 150°C, more preferably at 60 to 120°C. This provides a prepreg (organic resin prepreg). The method for impregnating annealed quartz glass cloth with the organic resin composition is not limited to the method described above; general methods can be used. Alternatively, the organic resin composition can be impregnated into annealed quartz glass cloth and then maintained in a pre-cured (A-stage) state to form a prepreg.

[0157] In this way, a thinner prepreg with a lower dielectric constant and improved insulation reliability is obtained.

[0158] The resin content in the prepreg is not particularly limited, for example, preferably 40 to 90% by mass, more preferably 50 to 90% by mass, and further preferably 60 to 80% by mass. If such a resin content is used, the desired low dielectric properties can be obtained, and the coefficient of thermal expansion (CTE) will not increase or the thickness accuracy will not decrease. In addition, the resin content here is the ratio of the mass of the part after deducting the mass of the glass cloth from the mass of the prepreg to the mass of the prepreg [=(mass of the prepreg - mass of the glass cloth) / mass of the prepreg × 100].

[0159] The number of prepregs obtained corresponding to the thickness of the insulating layer can be overlapped, pressurized, and heated to produce a laminated substrate. A metal foil is overlapped on the prepreg, and a vacuum press is used at a pressure of 5 to 50 MPa and a temperature of 70 to 180°C to produce a metal-clad laminated substrate. There is no particular limitation on the metal foil, but copper foil can be preferably used from an electrical and economic perspective. The metal-clad laminate can be processed by commonly used methods such as subtractive processing and hole processing to obtain a printed wiring board.

[0160] (Second Manufacturing Method)

[0161] Even in the case of a thermoplastic resin that is not easily soluble in a solvent, a resin substrate can be produced by heating and pressure-bonding a thin resin film, copper foil, and annealed quartz glass cloth.

[0162] For example, when making a fluororesin substrate, there is a method of pressing a pre-formed and surface-treated fluororesin film to annealed quartz glass cloth and copper foil under heating. Heat pressing under heating can usually be performed in the range of 250-400°C for 1-20 minutes at a pressure of 0.1-10 MPa. Regarding the heat pressing temperature, if it is too high, there is a possibility of resin bleeding and uneven thickness. It is preferably below 340°C, and more preferably below 330°C. Heat pressing can also be performed intermittently using a press, or continuously using a high-temperature laminator. When using a press, it is preferably a vacuum press to prevent air entrapment and facilitate the entry of the fluororesin into the annealed quartz glass cloth.

[0163] Surface-treated fluororesin films alone do not adequately adhere to copper foil with low surface roughness, oozing out of the copper foil during thermocompression bonding, and achieving uniform thickness is impossible. However, as described above, when composited with annealed quartz glass cloth, the linear expansion coefficient is sufficiently reduced, resin oozing is also reduced, and high adhesion is exhibited even to copper foil with a surface roughness Ra of less than 0.2 μm.

[0164] The laminate is constructed by alternately laminating n fluororesin films and n-1 annealed quartz glass cloths between two copper foils (n is an integer from 2 to 10). The value of n is preferably 8 or less, and more preferably 6 or less. The linear expansion coefficient of the resin-laminated substrate of the present invention in the XY directions can be varied by changing the thickness of the fluororesin films, the type of annealed quartz glass cloth, and the value of n. The linear expansion coefficient is preferably within the range of 5 to 50 ppm / °C, and more preferably within the range of 10 to 40 ppm / °C. If the linear expansion coefficient of the dielectric layer exceeds 50 ppm / °C, the adhesion between the copper foil and the dielectric layer decreases, and defects such as warping and undulation of the substrate are more likely to occur after etching the copper foil.

[0165] The resin substrate can also be produced by previously filling the thin resin film with the component (C) and heating and press-bonding it with annealed quartz glass cloth or the like.

[0166] The electrode pattern of the metal-clad laminate substrate can be produced by a known method, for example, by etching a copper-clad laminate substrate having the organic resin laminate substrate of the present invention and copper foil provided on one or both surfaces of the laminate substrate.

[0167] Example

[0168] Hereinafter, the present invention will be described in detail with reference to Examples, Comparative Examples, and Preparation Examples. However, the present invention is not limited to the following Examples.

[0169] In addition, the tensile strength, dielectric loss tangent (tan δ), and average particle size described below were measured by the following methods.

[0170] 1. Determination of tensile strength

[0171] The measurement was performed in accordance with "7.4 Tensile Strength" of JIS R3420:2013 "Glass Fiber General Testing Methods".

[0172] 2. Determination of dielectric loss tangent

[0173] 2.1 Glass cloth, resin substrate

[0174] Unless otherwise specified, the dielectric constant was measured at a frequency of 10 GHz using a SPDR (Split post dielectric resonators, manufactured by Keysight Technologies) dielectric resonator for dielectric constant measurement.

[0175] 2.2 Silica powder

[0176] (1) 100 parts by mass of silica powder was mixed, dispersed, and dissolved in 100 parts by mass of anisole solvent containing 100 parts by mass of SLK-3000 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a low-dielectric maleimide resin and 2.0 parts by mass of dicumyl peroxide (manufactured by PERCUMYLD: NOF CORPORATION) as a curing agent and free radical polymerization initiator to prepare a varnish. At this time, the volume percentage of silica powder relative to the resin was 33.3%. Similarly, silica powder was blended in such a manner that the volume percentages relative to 100 parts by mass of the above resin were 0%, 11.1%, and 66.7%, respectively, to prepare varnishes.

[0177] The prepared varnish was spread to a thickness of 200 μm using a bar coater and placed in a dryer at 80° C. for 30 minutes to remove the anisole solvent, thereby preparing an uncured maleimide resin composition.

[0178] (2) Each uncured maleimide resin composition prepared was placed in a 60 mm × 60 mm × 100 μm mold and cured using a hand press at 180°C for 10 minutes and 30 MPa. The cured resin sheet was then completely cured in a dryer at 180°C for 1 hour to produce a cured resin sheet. The cured resin sheet was cut into 50 mm × 50 mm pieces, and the dielectric loss tangent was measured at a frequency of 10 GHz using a SPDR (Split Post Dielectric Resonators, manufactured by Keysight Technologies) dielectric resonator for dielectric constant measurement.

[0179] (3) Create a straight line plotting the volume percentage of silica powder against the dielectric loss tangent using a graph with the volume percentage of silica powder on the horizontal axis and the measured dielectric loss tangent on the vertical axis. Extrapolate this straight line and use the dielectric loss tangent at 100% silica powder as the dielectric loss tangent value of the silica powder.

[0180] In addition, although there are measuring instruments that can directly measure silica powder, since the measurement is performed by filling the measuring pot with silica powder, it is difficult to remove the air mixed in. Silica powder with a large specific surface area is particularly affected by the mixed air, making this even more difficult. Therefore, in order to eliminate the influence of mixed air and obtain a value in a state close to the actual usage form, the dielectric loss tangent of silica powder is calculated using the above-mentioned measurement method in the present invention.

[0181] 3. Determination of average particle size

[0182] The particle size distribution was measured using a laser diffraction particle size analyzer, and the mass average value D50 in the particle size distribution was defined as the average particle size.

[0183] (Preparation Example 1): Production Example of Quartz Glass Cloth (SQ11, SQ12, SQ13)

[0184] While stretching the silica glass filaments at high temperature, a silica glass fiber sizing agent was applied to produce a silica glass filament bundle consisting of 200 silica glass filaments with a diameter of 5.0 μm. The resulting silica glass filament bundle was then twisted 0.4 times per 25 mm to produce a silica glass yarn.

[0185] The obtained quartz glass yarn was installed on an air jet loom to weave a plain woven quartz glass cloth with a warp density of 54 yarns / 25mm and a weft density of 54 yarns / 25mm. The thickness of the quartz glass cloth was 0.045mm and the weight per unit area of the cloth was 42.5g / m 2 .

[0186] The quartz glass cloth was heated at 400°C for 10 hours to remove the fiber sizing agent. The quartz glass cloth produced above, with a width of 1.3 m and a length of 2000 m, was designated SQ11. The dielectric loss tangent of SQ11 at a frequency of 10 GHz was 0.0011, and the tensile strength was 96 N / 25 mm. The weight per unit area of the cloth (g / m 2 ) has a tensile strength of 2.26 (N / 25mm).

[0187] Next, the quartz glass cloth with a width of 1.3 m and a length of 2000 m was placed in an electric furnace set at 700°C and heated for 5 hours. After heating, it was cooled to room temperature over 8 hours. This quartz glass cloth was designated as SQ12. The dielectric loss tangent of SQ12 at 10 GHz was 0.0002, and the tensile strength was 14 N / 25 mm. The weight per unit area of the cloth (g / m 2 ) has a tensile strength of 0.33 (N / 25mm).

[0188] The cooled quartz glass cloth was then immersed in alkaline electrolyzed water heated to 40°C and pH 13 for 48 hours to perform an etching process. After etching, it was rinsed with ion-exchanged water and then dried to produce a low-dielectric, high-strength quartz glass cloth (SQ13). The dielectric loss tangent of the quartz glass cloth SQ13 is 0.0002, the tensile strength is 120N / 25mm, and the weight per unit area of the cloth (g / m 2 ) has a tensile strength of 2.82 (N / 25mm).

[0189] The impurity metal contents of the quartz glass cloths SQ11, SQ12, and SQ13 were all 0.5 ppm in terms of the total alkali metal content, 0.1 ppm for P (phosphorus), and 0.1 ppb for U and Th. The contents of each element were measured by atomic absorption spectrometry (mass conversion).

[0190] Furthermore, each of the quartz glass cloths SQ11, SQ12, and SQ13 was surface-treated with a silane coupling agent KBM-903 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd., 3-aminopropyltrimethoxysilane) in the following steps, and then the tensile strength was measured.

[0191] (Process)

[0192] The quartz glass cloth was immersed in a 0.5 mass % KBM-903 aqueous solution for 10 minutes, and then heated and dried at 110° C. for 20 minutes to perform surface treatment.

[0193] (Preparation Example 2): Production Example of Quartz Glass Cloth (SQ21, SQ22, SQ23)

[0194] A quartz glass filament bundle consisting of 100 quartz glass filaments having a diameter of 5.0 μm was produced in the same manner as in Preparation Example 1. The obtained quartz glass filament bundle was twisted 0.8 times per 25 mm to produce a quartz glass yarn.

[0195] The obtained quartz glass yarn was installed on an air jet loom to weave a plain woven quartz glass cloth with a warp density of 66 yarns / 25mm and a weft density of 66 yarns / 25mm. The thickness of the quartz glass cloth was 0.030mm and the weight per unit area of the cloth was 26.5g / m 2 .

[0196] The quartz glass cloth was heated at 400°C for 10 hours to remove the fiber sizing agent. The quartz glass cloth produced above, with a width of 1.3 m and a length of 2000 m, was designated SQ21. The dielectric loss tangent of SQ21 at a frequency of 10 GHz was 0.0011, and the tensile strength was 49 N / 25 mm. The weight per unit area of the cloth (g / m 2 ) has a tensile strength of 1.85 (N / 25mm).

[0197] Next, the quartz glass cloth with a width of 1.3 m and a length of 2000 m produced above was placed in an electric furnace set at 700°C and heated for 5 hours. After heating, it was cooled to room temperature over 8 hours. This quartz glass cloth was designated as SQ22. The dielectric loss tangent of SQ22 at 10 GHz was 0.0002, and the tensile strength was 9 N / 25 mm. The weight per unit area of the cloth (g / m 2 ) has a tensile strength of 0.34 (N / 25mm).

[0198] The cooled quartz glass cloth was then immersed in alkaline electrolyzed water heated to 40°C and pH 13 for 48 hours to perform an etching process. After etching, the cloth was rinsed with ion-exchanged water and then dried to produce a low-dielectric, high-strength quartz glass cloth (SQ23). The dielectric loss tangent of the quartz glass cloth SQ23 at a frequency of 10 GHz was 0.0002, and the tensile strength was 79 N / 25 mm. The weight per unit area of the cloth (g / m 2 The metal content in the quartz glass cloth was measured in the same manner as in Preparation Example 1, and the results were the same.

[0199] Table 1 shows the types of the produced quartz glass cloths and the treatment items.

[0200] [Table 1]

[0201]

[0202] In the table, ○ represents the project to be processed and implemented.

[0203] (Preparation Example 3): Preparation Example of Low Dielectric Loss Tangent Silica Powder (S1)

[0204] 5 kg of silica (SO-E5 manufactured by Admatechs) with an average particle size of 1.5 μm and a dielectric loss tangent of 0.0015 (10 GHz) was placed in an alumina container and heated at 900°C in air for 12 hours in a muffle furnace (manufactured by AS ONE Corporation). The silica was then cooled to room temperature over 6 hours to obtain silica. The heat-treated silica was placed in a plastic container containing 20 liters of alkaline electrolyzed water with a pH of 13, heated to 60°C while stirring for 2 hours to remove the strain layer on the particle surface. The silica was then separated using a centrifugal separator, washed with methanol, and dried. The dielectric loss tangent of the silica obtained by crushing the dried silica using a ball mill was 0.0002 (10 GHz). The silica (S1) thus obtained was surface-treated with a silane coupling agent KBM-503 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd., 3-methacryloxypropyltrimethoxysilane) and then used for the production of a resin substrate.

[0205] (Preparation Example 4): Preparation Example of Low Dielectric Loss Tangent Silica Powder (S2)

[0206] Heat-treated silica was prepared in the same manner as in Preparation Example 3. 5 kg of silica (SO-E5 manufactured by Admatechs) having an average particle size of 1.5 μm and a dielectric loss tangent of 0.0015 (10 GHz) was placed in an alumina container and heated in a muffle furnace (manufactured by AS ONE Corporation) at 900° C. in air for 12 hours. The silica was then cooled to room temperature over 6 hours to obtain silica. The dielectric loss tangent of the silica was 0.0002 (10 GHz). The silica (S2) obtained here was surface-treated with a silane coupling agent, KBM-503 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd., 3-methacryloxypropyltrimethoxysilane), and then used in the manufacture of a resin substrate.

[0207] Table 2 shows the treatment items of the raw silica and the treated silica.

[0208] [Table 2]

[0209]

[0210] In the table, ○ represents the project to be processed and implemented.

[0211] [Manufacturing of Fluororesin Substrates]

[0212] (Example 1)

[0213] Two 50 μm-thick tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) films (TFE / PPVE = 98.5 / 1.5 (mol %), MFR (melt flow rate): 14.8 g / 10 min, melting point: 305°C) and one sheet of annealed quartz glass cloth (SQ13) prepared in Preparation Example 1 were prepared. These films were stacked in the order of PFA film / annealed quartz glass cloth / PFA film, and hot pressed at 325°C for 30 minutes using a vacuum press to produce a fluororesin substrate.

[0214] The fluororesin substrate had no molding defects and was a good fluororesin substrate. The dielectric loss tangent at 10 GHz was 0.0003, indicating excellent properties.

[0215] (Comparative Example 1)

[0216] Two 50 μm-thick tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) films (TFE / PPVE = 98.5 / 1.5 (mol %), MFR: 14.8 g / 10 min, melting point: 305°C) and one sheet of annealed quartz glass cloth (SQ11) prepared in Preparation Example 1 were prepared and laminated in the order of PFA film / quartz glass cloth / PFA film. The laminate was then hot-pressed at 325°C for 30 minutes using a vacuum press to produce a fluororesin substrate. The resulting fluororesin substrate exhibited no molding defects and exhibited a dielectric loss tangent of 0.0007 at 10 GHz.

[0217] (Comparative Example 2)

[0218] Two 50 μm-thick tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) films (TFE / PPVE = 98.5 / 1.5 (mol %), MFR: 14.8 g / 10 min, melting point: 305°C) and one quartz glass cloth (SQ12) prepared in Preparation Example 1 were prepared and laminated in the order of PFA film / quartz glass cloth / PFA film. The films were then hot-pressed at 325°C for 30 minutes using a vacuum press to produce a fluororesin substrate. The quartz glass cloth of the resulting fluororesin substrate was weak in strength, with some cracking due to the pressurization. Consequently, a satisfactory fluororesin substrate could not be produced. Therefore, the dielectric loss tangent could not be measured.

[0219] The results are shown in Table 3.

[0220] [Table 3]

[0221] Example 1 Comparative Example 1 Comparative Example 2 PFA membrane ○ ○ ○ Quartz glass cloth SQ13 SQ11 SQ12 Dielectric loss tangent (10GHz) 0.0003 0.0007 - Forming processability ◎ ◎ ×

[0222] Forming processability:

[0223] ◎: The fabric is not broken and is well formed.

[0224] ×: The fabric is torn and the molding is poor

[0225] [Prepreg and substrate using the SLK series of bismaleimide resins]

[0226] (Examples 2 to 5 and Comparative Examples 3 to 6)

[0227] As the (B) organic resin, the following bismaleimide resin was used.

[0228] (B) Bismaleimide resin

[0229] (B-1): SLK-3000 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.), a linear alkylene group-containing bismaleimide resin represented by the following formula (2):

[0230]

[0231] n≒3 (average)

[0232] (B-2): SLK-2500 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.), a linear alkylene group-containing bismaleimide resin represented by the following formula (3):

[0233]

[0234] n≒3, m≒3 (both are average values)

[0235] <Preparation of slurry>

[0236] (Preparation Example 5)

[0237] 100 parts by mass of SLK-3000 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.), 100 parts by mass of the silica powder (S1) prepared in Preparation Example 3, and 2 parts by mass of dicumyl peroxide (trade name: PERCUMYL D, manufactured by NOF CORPORATION) were added to anisole as a solvent and premixed with a stirrer to prepare a 60% slurry solution, thereby preparing a bismaleimide resin slurry composition in which the filler was uniformly dispersed.

[0238] (Preparation Example 6)

[0239] 100 parts by mass of SLK-3000 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.), 100 parts by mass of the silica powder (S2) prepared in Preparation Example 4, and 2 parts by mass of dicumyl peroxide (trade name: PERCUMYL D, manufactured by NOF CORPORATION) were added to anisole as a solvent and premixed with a stirrer to prepare a 60% slurry solution, thereby preparing a bismaleimide resin slurry composition in which the filler was uniformly dispersed.

[0240] (Preparation Example 7)

[0241] 100 parts by mass of SLK-2500 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.), 100 parts by mass of the silica powder (S1) prepared in Preparation Example 3, and 2 parts by mass of dicumyl peroxide (trade name: PERCUMYL D, manufactured by NOF CORPORATION) were added to anisole as a solvent and premixed with a stirrer to prepare a 60% slurry solution, thereby preparing a bismaleimide resin slurry composition in which the filler was uniformly dispersed.

[0242] (Preparation Example 8)

[0243] 100 parts by mass of SLK-3000 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.), 100 parts by mass of silica powder (SO-E5 manufactured by Admatechs) used as a raw material for the silica powder (S1) prepared in Preparation Example 3, and 2 parts by mass of dicumyl peroxide (trade name: PERCUMYLD, manufactured by NOFCORPORATION) were added to anisole as a solvent and pre-mixed with a stirrer to prepare a 60% slurry solution, thereby preparing a bismaleimide resin slurry composition in which the filler was uniformly dispersed.

[0244] <Prepreg production>

[0245] The slurry compositions prepared in Preparation Examples 5 to 8 were impregnated into quartz glass cloths SQ11, SQ12, and SQ13, and then dried at 120°C for 5 minutes to produce prepregs. The adhesion was adjusted to 44%. Three of the prepregs were then stacked and cured using a vacuum press at 150°C for 1 hour and then at 180°C for 2 hours to produce resin substrates (Examples 2 to 5 and Comparative Examples 3 to 6).

[0246] Then, a network analyzer (E5063-2D5 manufactured by Keysight) and a strip line (manufactured by KEYCOM Corp.) were connected to measure the dielectric loss tangent of the cured resin substrate at a frequency of 10 GHz.

[0247] In Comparative Examples 3 and 4, resin substrates could not be produced due to poor molding, and the dielectric loss tangent could not be measured.

[0248] The results are shown in Table 4.

[0249] [Table 4]

[0250]

[0251] Forming processability:

[0252] ◎: The fabric is not broken and is well formed.

[0253] ×: The fabric is torn and the molding is poor

[0254] (Example 6 and Comparative Examples 7 and 8)

[0255] In the same manner as in Examples 2 to 5 and Comparative Examples 3 to 6, the slurry composition prepared in Preparation Example 5 was impregnated into quartz glass cloths SQ21, SQ22, and SQ23, followed by drying at 120°C for 5 minutes to produce prepregs. The adhesion was adjusted to 44%. Three of the prepregs were then stacked and cured using a vacuum press at 150°C for 1 hour and then at 180°C for 2 hours to produce resin substrates.

[0256] Then, a network analyzer (E5063-2D5 manufactured by Keysight) and a strip line (manufactured by KEYCOM Corp.) were connected to measure the dielectric loss tangent of the cured resin substrate at a frequency of 10 GHz.

[0257] In Comparative Example 7, the resin substrate could not be produced due to poor molding, and the dielectric loss tangent could not be measured.

[0258] The results are shown in Table 5.

[0259] [Table 5]

[0260] Examples / Comparative Examples Example 6 Comparative Example 7 Comparative Example 8 Preparation Example 5 5 5 Quartz glass cloth 8Q23 8Q22 8Q21 8LK-3000 ○ ○ ○ Silica powder (S1) ○ ○ ○ Dielectric loss tangent (10GHz) 0.0009 - 0.0013 Forming processability ◎ × ◎

[0261] Forming processability:

[0262] ◎: The fabric is not broken and is well formed.

[0263] ×: The fabric is torn and the molding is poor

[0264] [Prepreg and laminated substrate using cyanate resin]

[0265] (Example 7)

[0266] 90 parts by mass of Primaset PT-60 (manufactured by Lonza Corporation, with a cyanate group equivalent of 119) as a cyanate ester resin, 10 parts by mass of the phenol compound TD2131 (manufactured by DIC Corporation, with a phenolic hydroxyl group equivalent of 110), and 800 parts by mass of the silica (S2) prepared in Preparation Example 4 were placed in 500 parts by mass of methyl ethyl ketone as a solvent and uniformly mixed using a high-speed mixer to prepare a dispersion.

[0267] By impregnating the methyl ethyl ketone dispersion of the cyanate resin composition in quartz glass cloth (SQ13), the dispersion is impregnated in quartz glass cloth and the adhesion amount is adjusted to 44%. By placing the glass cloth in a hot air dryer for 2 hours at 60 ° C, the solvent is volatilized and a prepreg is made. The prepreg is a base material that is not sticky and easy to operate at room temperature. The 2 prepregs manufactured here are overlapped, and after being molded by hot pressing machine with 170 ° C for 1 hour pressurization / heat curing, it is further post-cured for 1 hour at 185 ° C to obtain a cyanate resin laminated substrate. Then, a network analyzer (Keysight company manufactures E5063-2D5) and a stripline (KEYCOM Corp. manufacture) are connected to measure the dielectric loss tangent of the above-mentioned cured resin substrate under a frequency of 10 GHz. The dielectric loss tangent (10 GHz) is 0.0008.

[0268] (Comparative Example 9)

[0269] 90 parts by mass of Primaset PT-60 (manufactured by Lonza, with a cyanate group equivalent of 119) as a cyanate resin, 10 parts by mass of the phenol compound TD2131 (manufactured by DIC Corporation, with a phenolic hydroxyl group equivalent of 110), and 800 parts by mass of the silica powder (SO-E5) used as the raw material for the silica powder (S1) produced in Preparation Example 3 (manufactured by Admatechs) were added to 500 parts by mass of methyl ethyl ketone as a solvent and uniformly mixed using a high-speed mixer to prepare a dispersion.

[0270] The methyl ethyl ketone dispersion of the cyanate resin composition is impregnated in quartz glass cloth (SQ11), so that the dispersion is impregnated in quartz glass cloth, and the adhesion amount is adjusted to 44%. By placing the glass cloth in a hot air dryer at 60 ° C for 2 hours, so that the solvent is volatilized, a prepreg is made. The prepreg is a base material that is not sticky and easy to operate at room temperature. The 2 prepregs made here are overlapped, and after being molded by hot pressing machine with 170 ° C for 1 hour pressurization / heat curing, it is further post-cured at 185 ° C for 1 hour to obtain a cyanate resin laminated substrate. Then, in the same manner as Example 7, the dielectric loss tangent of the cured resin substrate at a frequency of 10 GHz is measured. The dielectric loss tangent (10 GHz) is 0.0017.

[0271] Compared to substrates using conventional quartz glass cloth (SQ11, SQ21) (Comparative Examples 1, 5, 6, 8, and 9), the low-dielectric resin substrates of the present invention in Examples 1 to 7 have lower dielectric loss tangents and higher tensile strengths of the composited quartz glass cloth. Consequently, the substrates themselves also have excellent strength and formability.

[0272] Furthermore, a comparison of the results of Example 2 with Comparative Example 5, and of the results of Example 5 with Comparative Example 6, shows that even when silica powder is further included as a filler, the substrates of the present invention (Examples 2 and 5) exhibit lower dielectric loss tangents than substrates using conventional quartz glass cloth (Comparative Examples 5 and 6). If the silica powder used for filling also has a low dielectric loss tangent, the substrate's coefficient of expansion and elastic modulus can be adjusted, significantly improving dielectric properties (Examples 2 to 4, 6, and 7).

[0273] On the other hand, since the substrates outside the scope of the present invention (Comparative Examples 1 to 9) did not use quartz glass cloth having a low dielectric loss tangent and excellent tensile strength, they could not achieve both low dielectric loss tangent and moldability.

[0274] Furthermore, because the quartz glass cloth used in the low-dielectric resin substrate of the present invention inherently has a low dielectric loss tangent and excellent tensile strength, a wider range of organic resins can be composited with it. Consequently, by appropriately selecting the composite organic resin, a prepreg can be obtained by impregnation before manufacturing the substrate. Alternatively, the substrate can be manufactured without a prepreg by thermally fusing the molded resin.

[0275] Thus, since the low-dielectric resin substrate of the present invention has a low dielectric loss tangent and excellent tensile strength, it can be suitably used in high-speed communication substrates and antenna substrates, which have low transmission loss even when using high frequencies such as millimeter waves. It can also cope with high-density mounting or ultra-thin circuit substrates, and has high utilization value in high-speed communication fields such as 5G.

[0276] Furthermore, because the present invention allows the incorporation of silica powder, a representative general-purpose inorganic powder, while maintaining a low dielectric loss tangent of the substrate, and because silica powder, as an inorganic powder added to resin, exhibits a low coefficient of expansion and excellent insulating and dielectric properties, it is expected to have broad applications as a filler in high-speed communication substrates and antenna substrates, which are expected to see significant growth in the future. In particular, even when silica powder is further included as a filler, the use of low-dielectric-loss-tangent silica powder, with a dielectric loss tangent of less than 0.0010 at 10 GHz, further reduces the dielectric loss tangent of the substrate, making its utility in these applications highly valuable.

[0277] The present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any technical solution having substantially the same structure and having the same function and effect as the technical concept described in the claims of the present invention is within the scope of protection of the present invention.

Claims

1. A low-dielectric resin substrate, which is a composite of an organic resin and a heat-treated annealed quartz glass cloth, characterized in that: The heating temperature of the heat treatment is 500°C to 1000°C. The SiO2 content of the annealed quartz glass cloth is 99.5% by mass or more and has been etched. The dielectric loss tangent of the annealed quartz glass cloth at 10 GHz is less than 0.0010, and the weight per unit area of the cloth (g / m 2 ) has a tensile strength of 1.0 N / 25 mm or more.

2. The low dielectric resin substrate according to claim 1, wherein The invention further comprises silicon dioxide powder having a dielectric loss tangent of less than 0.0010 at 10 GHz and an average particle size of 0.1 to 30 μm.

3. The low dielectric resin substrate according to claim 1, wherein The organic resin is a thermoplastic resin.

4. The low dielectric resin substrate according to claim 2, wherein The organic resin is a thermoplastic resin.

5. The low dielectric resin substrate according to claim 1, wherein The organic resin is a thermosetting resin.

6. The low dielectric resin substrate according to claim 2, wherein The organic resin is a thermosetting resin.

7. The low dielectric resin substrate according to claim 3 or 4, characterized in that The thermoplastic resin is one or more thermoplastic resins selected from the group consisting of polyphenylene ether, polyetheretherketone, polyetherketone, polyethersulfone, and fluororesin.

8. The low dielectric resin substrate according to claim 5 or 6, characterized in that The thermosetting resin is one or more thermosetting resins selected from epoxy resin, allylated polyphenylene ether resin, maleimide resin, cyanate resin, and cyclopentadiene-styrene copolymer resin.

9. The low dielectric resin substrate according to claim 8, wherein The epoxy resin is an allylated epoxy resin.

10. The low dielectric resin substrate according to claim 8, wherein The maleimide resin is a bismaleimide resin.

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