A low-dielectric substrate material and a metal substrate using the same are provided. The low-dielectric substrate material includes a rubber resin composition, at least one inorganic filler, and borosilicate-type hollow microparticles. The rubber resin composition includes 30 wt percent to 60 wt percent of a liquid rubber, 10 wt percent to 40 wt percent of a polyphenylene ether resin, and 10 wt percent to 40 wt percent of a crosslinker. A molecular weight of the liquid rubber ranges from 2500 g/mol to 6000 g/mol. The at least one inorganic filler is selected from the group consisting of magnesium oxide, aluminum oxide, silicon oxide, zinc oxide, aluminum nitride, boron nitride, silicon carbide, and aluminum silicate. An amount of the borosilicate-type hollow microparticles is not more than 10 phr relative to 100 phr of the rubber resin composition.

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