The present disclosure relates to a dielectric substrate that may include a polymer based core film, and a fluoropolymer based adhesive layer. The polymer based core film may include a resin matrix component, and a ceramic filler component. The ceramic filler component may include a first filler material. The particle size distribution of the first filler material may have a D.sub.10 of at least about 1.0 microns and not greater than about 1.7, a D.sub.50 of at least about 1.0 microns and not greater than about 3.5 microns, and a D.sub.90 of at least about 2.7 microns and not greater than about 6 microns.

Provided is a composite material that shows a low specific dielectric constant, and that hardly causes an appearance failure or changes in characteristics when exposed to, for example, a treatment liquid to be used in the production of an electronic circuit board. Specifically, a plate-like composite material including polytetrafluoroethylene and a predetermined filler, and satisfying a predetermined condition serves as a composite material that shows a low specific dielectric constant, and that hardly causes an appearance failure or changes in characteristics even when exposed to, for example, a treatment liquid to be used in the production of an electronic circuit board.

In an embodiment the dielectric layer comprises a fluoropolymer, a plurality of boron nitride particles, a plurality of titanium dioxide particles, a plurality of silica particles; and a reinforcing layer. The dielectric layer can comprise at least one of 20 to 45 volume percent of the fluoropolymer, 15 to 35 volume percent of the plurality of boron nitride particles, 1 to 32 volume percent of the plurality of titanium dioxide particles, 10 to 35 volume percent of the plurality of silica particles, and 5 to 15 volume percent of the reinforcing layer; wherein the volume percent values are based on a total volume of the dielectric layer.

A preparation method for a spherical silica powder filler, comprises the following steps: S1, providing spherical polysiloxane comprising T units by means of a hydrolysis condensation reaction of R.sub.1SiX.sub.3, wherein R.sub.1 is hydrogen atom or an independently selectable organic group having 1 to 18 carbon atoms, X is a hydrolyzable group, and the T unit is R.sub.1SiO.sub.3—; and S2, calcining the spherical polysiloxane under the condition of a dry oxidizing gas atmosphere at a calcining temperature between 850° C. and 1200° C., so as to obtain a spherical silica powder filler having a low hydroxyl content. The spherical silica powder filler is composed of at least one selected from Q.sub.1 unit, Q.sub.2 unit, Q.sub.3 unit and Q.sub.4 unit, wherein Q.sub.1 unit is Si(OH).sub.3O—, Q.sub.2 unit is Si(OH).sub.2O.sub.2—,Q.sub.3 unit is SiOHO.sub.3—, Q.sub.4 unit is SiO.sub.4—, and the content of Q.sub.4 unit is greater than or equal to 95%.

In an embodiment, a printed circuit board substrate (12) comprises a polymer matrix; a reinforcing layer (42); and a plurality of coated boron nitride particles (44); wherein the plurality of coated boron nitride particles comprise a coating having an average coating thickness of 1 to 100 nanometers. The polymer matrix can comprise at least one of an epoxy, a polyphenylene ether, polystyrene, an ethylene-propylene dicyclopentadiene copolymer, a polybutadiene, a polyisoprene, a fluoropolymer, or a crosslinked matrix comprising at least one of triallyl cyanurate, triallyl isocyanurate, 1,2,4-trivinyl cyclohexane, trimethylolpropane triacrylate, or trimethylolpropane trimethacrylate.

The wiring board according to the present disclosure includes: a first insulating layer including insulating particles; a plurality of first conductors located on the first insulating layer at an interval of a first distance from each other; a second conductor located on the first insulating layer at an interval of a second distance from the first conductor; and a second insulating layer located on the first insulating layer to cover the first conductor and the second conductors and including the insulating particles. When a boundary portion between the first insulating layer and the second insulating layer is viewed in cross-section in the thickness direction, the ratio of a first area occupied by the insulating particles in a first boundary portion including the first distance is higher than the ratio of a second area occupied by the insulating particles in a second boundary portion including the second distance.

A copper base substrate of the present invention, in which a copper substrate, an insulating layer, and a circuit layer, are laminated in an order in the copper substrate, a ratio of a thickness (unit: .Math.m) to an elastic modulus (unit: GPa) at 100° C. is 50 or more in the insulating layer, and the circuit layer has an elastic modulus at 100° C. of 100 GPa or less.

A laminated plate has a metallic conductive layer layered on one surface or each surface of an insulating substrate, the insulating substrate contains a fluorine resin and a polymer of an alkoxysilane, and the fluorine resin is dispersed in the polymer of the alkoxysilane.

Provided is a boron nitride sintered body including: a plurality of coarse particles each having a length of 20 μm or more; and fine particles smaller than the plurality of coarse particles, in which, when viewed in a cross-section, the plurality of coarse particles intersect with each other. Provided is a method for manufacturing a boron nitride sintered body, the method including: a raw material preparation step of firing a mixture containing boron carbonitride and a boron compound in a nitrogen atmosphere to obtain lump boron nitride having an average particle diameter of 10 to 200 μm; and a sintering step of molding and heating a blend containing the lump boron nitride and a sintering aid to obtain a boron nitride sintered body including coarse particles each having a length of 20 μm or more in a cross-section and fine particles smaller than the coarse particles.

A circuit board includes, in order in a stacking direction, a first insulating layer, a second insulating layer in contact with the first insulating layer, and a conductor layer, the first insulating layer includes a liquid crystal polymer as a main component, and the second insulating layer includes a fluoropolymer including at least one of polytetrafluoroethylene and a perfluoroalkoxy alkane and includes a polyimide resin with an imidization rate of about 90% or more, the polyimide resin being present in an amount of about 0.5 parts or more by weight and less than about 20 parts by weight per 100 parts by weight of the fluoropolymer.